Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Reference Manual
Volume I
Basic Programming Guide
Quicksilver Beta
December 31st 2007

CLIPS Reference Manual

CLIPS Basic Programming Guide
Quicksilver Beta December 31st 2007
CONTENTS
License Information
...
iii
Acknowledgements
...
1
Section 2 - CLIPS Overview
...
1 Interacting with CLIPS
...
1
...
3
2
...
2 Automated Command Entry and Loading
...
1
...
5
2
...
5
2
...
6
2
...
1 Data Types
...
3
...
9
2
...
3 Constructs
...
4 Data Abstraction
...
4
...
11
2
...
1
...
11
2
...
1
...
12
2
...
1
...
13
2
...
2 Objects
...
4
...
1 Initial Objects
...
4
...
14
2
...
15
2
...
1 Heuristic Knowledge – Rules
...
5
...
16
2
...
2
...
16
2
...
2
...
16
2
...
2
...
17
2
...
2
...
17
2
...
17
2
...
1 COOL Deviations from a Pure OOP Paradigm
...
6
...
18
2
...
3 Instance-set Queries and Distributed Actions
...
21
CLIPS Basic Programming Guide

i

CLIPS Reference Manual

3
...
22
3
...
22
3
...
23
3
...
23
Section 4 - Deffacts Construct
...
27
5
...
27
5
...
28
5
...
29
5
...
1 Depth Strategy
...
3
...
29
5
...
3 Simplicity Strategy
...
3
...
30
5
...
5 LEX Strategy
...
3
...
31
5
...
7 Random Strategy
...
4 LHS Syntax
...
4
...
33
5
...
1
...
34
5
...
1
...
36
5
...
1
...
38
5
...
1
...
40
5
...
1
...
43
5
...
1
...
45
5
...
1
...
46
5
...
1
...
49
5
...
2 Test Conditional Element
...
4
...
51
5
...
4 And Conditional Element
...
4
...
53
5
...
6 Exists Conditional Element
...
4
...
56
5
...
8 Logical Conditional Element
...
4
...
61
5
...
9
...
61
5
...
9
...
61
5
...
9
...
62
5
...
9
...
63
5
...
9
...
63
5
...
10 Declaring Rule Properties
...
4
...
1 The Salience Rule Property
...
4
...
2 The Auto-Focus Rule Property
...
67
Section 7 - Deffunction Construct
...
75
8
...
75
8
...
76
8
...
76
8
...
76
8
...
1 Generic Function Headers
...
4
...
77
8
...
3 Method Parameter Restrictions
...
4
...
79
8
...
81
8
...
1 Applicability of Methods Summary
...
5
...
82
8
...
3 Shadowed Methods
...
5
...
85
8
...
5 Generic Function Return Value
...
87
9
...
87
9
...
87
9
...
88
9
...
1 Multiple Inheritance
...
3
...
1 Multiple Inheritance Rules
...
3
...
92
9
...
2
...
92
9
...
2
...
92
9
...
3 Slots
...
3
...
1 Slot Field Type
...
3
...
2 Default Value Facet
...
3
...
3 Storage Facet
...
3
...
4 Access Facet
...
3
...
5 Inheritance Propagation Facet
...
3
...
6 Source Facet
...
3
...
7 Pattern-Match Reactivity Facet
...
3
...
8 Visibility Facet
...
3
...
9 Create-Accessor Facet
...
3
...
10 Override-Message Facet
...
3
...
11 Constraint Facets
...
3
...
102
CLIPS Basic Programming Guide

iii

CLIPS Reference Manual

9
...
103
9
...
1 Message-handler Parameters
...
4
...
1 Active Instance Parameter
...
4
...
106
9
...
3 Daemons
...
4
...
108
9
...
4
...
108
9
...
4
...
109
9
...
4
...
110
9
...
4
...
110
9
...
4
...
111
9
...
4
...
111
9
...
4
...
112
9
...
4
...
112
9
...
112
9
...
1 Applicability of Message-handlers
...
5
...
113
9
...
3 Shadowed Message-handlers
...
5
...
114
9
...
5 Message Return Value
...
6 Manipulating Instances
...
6
...
115
9
...
1
...
117
9
...
2 Reinitializing Existing Instances
...
6
...
120
9
...
4 Setting Slots
...
6
...
121
9
...
6 Delayed Pattern-Matching When Manipulating Instances
...
6
...
122
9
...
7
...
122
9
...
7
...
123
9
...
7
...
123
9
...
7
...
124
9
...
8 Duplicating Instances
...
6
...
1 Directly Duplicating an Instance with Delayed Pattern-Matching
...
6
...
2 Directly Duplicating an Instance with Immediate Pattern-Matching
...
6
...
3 Duplicating an Instance using Messages with Delayed Pattern-Matching
...
6
...
4 Duplicating an Instance using Messages with Immediate Pattern-Matching 126
9
...
127
9
...
1 Instance-set Definition
...
7
...
129
9
...
3 Query Definition
...
7
...
131
iv

Table of Contents

CLIPS Reference Manual

9
...
5 Scope in Instance-set Query Functions
...
7
...
132
9
...
7 Halting and Returning Values from Query Functions
...
7
...
133
9
...
8
...
133
9
...
8
...
133
9
...
8
...
134
9
...
8
...
134
9
...
8
...
135
9
...
8
...
135
Section 10 - Defmodule Construct
...
1 Defining Modules
...
2 Specifying a Construct’s Module
...
3 Specifying Modules
...
4 Importing and Exporting Constructs
...
4
...
140
10
...
2 Importing Constructs
...
5 Importing and Exporting Facts and Instances
...
5
...
142
10
...
142
Section 11 - Constraint Attributes
...
1 Type Attribute
...
2 Allowed Constant Attributes
...
3 Range Attribute
...
4 Cardinality Attribute
...
5 Deriving a Default Value From Constraints
...
6 Constraint Violation Examples
...
151
12
...
151
12
...
1 Testing For Numbers
...
1
...
151
12
...
3 Testing For Integers
...
1
...
152
12
...
5 Testing For Strings
...
1
...
152
12
...
7 Testing For Even Numbers
...
1
...
152
12
...
9 Testing For Multifield Values
...
1
...
153
12
...
11 Comparing for Equality
...
1
...
153
12
...
13 Comparing Numbers for Equality
...
1
...
154
12
...
15 Greater Than Comparison
...
1
...
155
12
...
17 Less Than Comparison
...
1
...
156
12
...
19 Boolean And
...
1
...
157
12
...
21 Boolean Not
...
2 Multifield Functions
...
2
...
157
12
...
2 Specifying an Element
...
2
...
158
12
...
4 Comparing Multifield Values
...
2
...
159
12
...
6 Creating Multifield Values from Strings
...
2
...
160
12
...
8 Extracting a Sub-sequence from a Multifield Value
...
2
...
161
12
...
10 Inserting Fields within a Multifield Value
...
2
...
162
12
...
12 Getting All but the First Field from a Multifield Value
...
2
...
162
12
...
14 Deleting Specific Values within a Multifield Value
...
2
...
163
12
...
163
12
...
1 String Concatenation
...
3
...
164
12
...
3 Taking a String Apart
...
3
...
164
12
...
5 Evaluating a Function within a String
...
3
...
165
12
...
7 Converting a String to Uppercase
...
3
...
166
12
...
9 Comparing Two Strings
...
3
...
167
12
...
11 Checking the Syntax of a Construct or Function Call within a String
...
3
...
168
12
...
168
12
...
1 Logical Names
...
4
...
169
12
...
2
...
169
vi

Table of Contents

CLIPS Reference Manual

12
...
2
...
170
12
...
2
...
171
12
...
2
...
171
12
...
2
...
172
12
...
2
...
173
12
...
2
...
175
12
...
2
...
175
12
...
2
...
176
12
...
2
...
177
12
...
2
...
177
12
...
178
12
...
1 Standard Math Functions
...
5
...
1 Addition
...
5
...
2 Subtraction
...
5
...
3 Multiplication
...
5
...
4 Division
...
5
...
5 Integer Division
...
5
...
6 Maximum Numeric Value
...
5
...
7 Minimum Numeric Value
...
5
...
8 Absolute Value
...
5
...
9 Convert To Float
...
5
...
10 Convert To Integer
...
5
...
182
12
...
2
...
183
12
...
2
...
184
12
...
2
...
184
12
...
2
...
184
12
...
2
...
185
12
...
2
...
185
12
...
2
...
185
12
...
2
...
185
12
...
2
...
186
12
...
2
...
186
12
...
2
...
186
12
...
2
...
187
12
...
2
...
187
12
...
187
12
...
1 Binding Variables
...
6
...
then
...
189
12
...
3 While
...
6
...
191
12
...
5 Progn
...
6
...
192
CLIPS Basic Programming Guide

vii

CLIPS Reference Manual

12
...
7 Return
...
6
...
193
12
...
9 Switch
...
7 Miscellaneous Functions
...
7
...
194
12
...
2 Gensym*
...
7
...
195
12
...
4 Random
...
7
...
196
12
...
6 Time
...
7
...
197
12
...
8 Determining the Restrictions for a Function
...
7
...
197
12
...
10 Calling a Function
...
7
...
198
12
...
199
12
...
1 Determining the Module in which a Deftemplate is Defined
...
8
...
199
12
...
3 Getting the Cardinality for a Deftemplate Slot
...
8
...
200
12
...
5 Getting the Default Value for a Deftemplate Slot
...
8
...
201
12
...
7 Testing whether a Deftemplate Slot is a Multifield Slot
...
8
...
202
12
...
9 Getting the Numeric Range for a Deftemplate Slot
...
8
...
202
12
...
11 Getting the Primitive Types for a Deftemplate Slot
...
8
...
203
12
...
203
12
...
1 Creating New Facts
...
9
...
204
12
...
3 Modifying Template Facts
...
9
...
206
12
...
5 Asserting a String
...
9
...
207
12
...
7 Determining If a Fact Exists
...
9
...
208
12
...
9 Determining the Slot Names Associated with a Fact
...
9
...
209
12
...
11 Retrieving the Fact-List
...
9
...
210
12
...
12
...
211
12
...
12
...
212
viii

Table of Contents

CLIPS Reference Manual

12
...
12
...
213
12
...
12
...
213
12
...
12
...
214
12
...
12
...
214
12
...
12
...
215
12
...
12
...
215
12
...
218
12
...
1 Getting the List of Deffacts
...
10
...
219
12
...
219
12
...
1 Getting the List of Defrules
...
11
...
219
12
...
219
12
...
1 Getting the Current Focus
...
12
...
220
12
...
3 Removing the Current Focus from the Focus Stack
...
13 Defglobal Functions
...
13
...
221
12
...
2 Determining the Module in which a Defglobal is Defined
...
14 Deffunction Functions
...
14
...
222
12
...
2 Determining the Module in which a Deffunction is Defined
...
15 Generic Function Functions
...
15
...
222
12
...
2 Determining the Module in which a Generic Function is Defined
...
15
...
223
12
...
4 Type Determination
...
15
...
224
12
...
6 Calling Shadowed Methods
...
15
...
225
12
...
8 Calling a Specific Method
...
15
...
226
12
...
227
12
...
1 Class Functions
...
16
...
1 Getting the List of Defclasses
...
16
...
2 Determining the Module in which a Defclass is Defined
...
16
...
3 Determining if a Class Exists
...
16
...
4 Superclass Determination
...
16
...
5 Subclass Determination
...
16
...
6 Slot Existence
...
16
...
7 Testing whether a Slot is Writable
...
16
...
8 Testing whether a Slot is Initializable
...
16
...
9 Testing whether a Slot is Public
...
16
...
10 Testing whether a Slot can be Accessed Directly
...
16
...
11 Message-handler Existence
...
16
...
12 Determining if a Class can have Direct Instances
...
16
...
13 Determining if a Class can Satisfy Object Patterns
...
16
...
14 Getting the List of Superclasses for a Class
...
16
...
15 Getting the List of Subclasses for a Class
...
16
...
16 Getting the List of Slots for a Class
...
16
...
17 Getting the List of Message-Handlers for a Class
...
16
...
18 Getting the List of Facets for a Slot
...
16
...
19 Getting the List of Source Classes for a Slot
...
16
...
20 Getting the Primitive Types for a Slot
...
16
...
21 Getting the Cardinality for a Slot
...
16
...
22 Getting the Allowed Values for a Slot
...
16
...
23 Getting the Numeric Range for a Slot
...
16
...
24 Getting the Default Value for a Slot
...
16
...
25 Setting the Defaults Mode for Classes
...
16
...
26 Getting the Defaults Mode for Classes
...
16
...
27 Getting the Allowed Values for a Slot
...
16
...
236
12
...
2
...
236
12
...
2
...
237
12
...
2
...
237
12
...
3 Definstances Functions
...
16
...
1 Getting the List of Definstances
...
16
...
2 Determining the Module in which a Definstances is Defined
...
16
...
239
12
...
4
...
239
12
...
4
...
239
12
...
4
...
239
12
...
4
...
240
12
...
4
...
240
12
...
4
...
240
12
...
4
...
240
12
...
4
...
241
12
...
4
...
241
12
...
4
...
242
12
...
4
...
242
12
...
4
...
242
12
...
244
12
...
1 Getting the List of Defmodules
...
17
...
245
12
...
3 Getting the Current Module
...
18 Sequence Expansion
...
18
...
246
12
...
2 Multifield Expansion Function
...
18
...
247
12
...
4 Getting The Sequence Operator Recognition Behavior
...
18
...
248
Section 13 - Commands
...
1 Environment Commands
...
1
...
249
13
...
2 Loading Constructs From A File without Progress Information
...
1
...
249
13
...
4 Loading a Binary Image
...
1
...
250
13
...
6 Clearing CLIPS
...
1
...
251
13
...
8 Resetting CLIPS
...
1
...
252
13
...
10 Executing Commands From a File Without Replacing Standard Input
...
1
...
252
13
...
12 Calling the Operating System
...
1
...
253
13
...
14 Getting The Auto-Float Dividend Behavior
...
1
...
254
13
...
16 Getting the Dynamic Constraint Checking Behavior
...
1
...
254
13
...
18 Getting the Static Constraint Checking Behavior
...
1
...
254
13
...
255
13
...
1 Generating Trace Files
...
2
...
255
13
...
3 Enabling Watch Items
...
2
...
257
13
...
5 Viewing the Current State of Watch Items
...
3 Deftemplate Commands
...
3
...
258
13
...
2 Displaying the List of Deftemplates
...
3
...
259
13
...
259
13
...
1 Displaying the Fact-List
...
4
...
259
13
...
3 Saving The Fact-List To A File
...
4
...
260
13
...
5 Getting the Duplication Behavior of Facts
...
4
...
261
13
...
262
13
...
1 Displaying the Text of a Deffacts
...
5
...
262
13
...
3 Deleting a Deffacts
...
6 Defrule Commands
...
6
...
263
13
...
2 Displaying the List of Rules
...
6
...
263
13
...
4 Displaying Matches for a Rule
...
6
...
265
13
...
6 Removing a Breakpoint for a Rule
...
6
...
266
13
...
8 Refreshing a Rule
...
6
...
266
13
...
10 Getting the Incremental Reset Behavior
...
6
...
267
13
...
12 Determining the Logical Dependents of a Pattern Entity
...
7 Agenda Commands
...
7
...
268
13
...
2 Running CLIPS
...
7
...
268
13
...
4 Stopping Rule Execution
...
7
...
269
13
...
6 Getting The Current Conflict Resolution Strategy
...
7
...
269
13
...
8 Removing all Module Names from the Focus Stack
...
7
...
270
13
...
10 Getting the Salience Evaluation Behavior
...
7
...
270
13
...
271
13
...
1 Displaying the Text of a Defglobal
...
8
...
271
13
...
3 Deleting a Defglobal
...
8
...
271
13
...
5 Setting the Reset Behavior of Global Variables
...
8
...
272
13
...
272
13
...
1 Displaying the Text of a Deffunction
...
9
...
272
13
...
3 Deleting a Deffunction
...
10 Generic Function Commands
...
10
...
273
xii

Table of Contents

CLIPS Reference Manual

13
...
2 Displaying the Text of a Generic Function Method
...
10
...
273
13
...
4 Displaying the List of Methods for a Generic Function
...
10
...
274
13
...
6 Deleting a Generic Function Method
...
10
...
275
13
...
275
13
...
1 Class Commands
...
11
...
1 Displaying the Text of a Defclass
...
11
...
2 Displaying the List of Defclasses
...
11
...
3 Deleting a Defclass
...
11
...
4 Examining a Class
...
11
...
5 Examining the Class Hierarchy
...
11
...
279
13
...
2
...
279
13
...
2
...
279
13
...
2
...
280
13
...
2
...
280
13
...
3 Definstances Commands
...
11
...
1 Displaying the Text of a Definstances
...
11
...
2 Displaying the List of Definstances
...
11
...
3 Deleting a Definstances
...
11
...
282
13
...
4
...
282
13
...
4
...
283
13
...
4
...
283
13
...
4
...
284
13
...
4
...
284
13
...
4
...
284
13
...
4
...
284
13
...
285
13
...
1 Displaying the Text of a Defmodule
...
12
...
285
13
...
285
13
...
1 Determining the Amount of Memory Used by CLIPS
...
13
...
285
13
...
3 Releasing Memory Used by CLIPS
...
13
...
286
13
...
286
13
...
1 Using the CLIPS Help Facility
...
14
...
287
13
...
288
13
...
1 External Text File Format
...
15
...
290
13
...
2
...
290
13
...
2
...
290
13
...
2
...
292
13
...
2
...
292
13
...
292
13
...
1 Setting the Profiling Report Threshold
...
16
...
293
13
...
3 Resetting Profiling Information
...
16
...
293
13
...
5 Profiling Constructs and User Functions
...
297
A
...
297
A
...
297
A
...
297
Appendix B - Update Release Notes
...
1 Version 6
...
299
B
...
24
...
3 Version 6
...
302
B
...
22
...
5 Version 6
...
303
B
...
2
...
7 Version 6
...
306
B
...
05
...
9 Version 6
...
310
B
...
03
...
11 Version 6
...
312
B
...
01
...
315
Appendix D - Integrated Editor
...
1 Special characters
...
2 Control Commands
...
3 Extended (Control-X) Commands
...
4 Meta Commands (Activated by or )
...
327
E
...
327
E
...
328
E
...
329
E
...
329
xiv

Table of Contents

CLIPS Reference Manual

E
...
329
Appendix F - CLIPS Warning Messages
...
333
Appendix H - CLIPS BNF
...
379
Appendix J - Bibliography of CLIPS Publications
...
393

CLIPS Basic Programming Guide

xv

CLIPS Reference Manual

License Information
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
associated documentation files (the “Software”), to deal in the Software without restriction,
including without limitation the rights to use, copy, modify, merge, publish, distribute, and/or
sell copies of the Software, and to permit persons to whom the Software is furnished to do so
...
IN NO EVENT SHALL
THE AUTHORS BE LIABLE FOR ANY CLAIM, OR ANY SPECIAL INDIRECT OR CONSEQUENTIAL
DAMAGES, OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE
...
However, if you derive commercial or monetary benefit from use of the software or just
want to show support, please consider making a voluntary payment based on the worth of the
software to you as compensation for the time and effort required to develop and maintain CLIPS
...
kagi
...


CLIPS Basic Programming Guide

i

CLIPS Reference Manual

Preface
The History of CLIPS
The origins of the C Language Integrated Production System (CLIPS) date back to 1984 at
NASA’s Johnson Space Center
...

However, despite extensive demonstrations of the potential of expert systems, few of these
applications were put into regular use
...
In particular, three problems
hindered the use of LISP based expert system tools within NASA: the low availability of LISP
on a wide variety of conventional computers, the high cost of state-of-the-art LISP tools and
hardware, and the poor integration of LISP with other languages (making embedded applications
difficult)
...
Although a number of tool
vendors started converting their tools to run in C, the cost of each tool was still very high, most
were restricted to a small variety of computers, and the projected availability times were
discouraging
...

The prototype version of CLIPS was developed in the spring of 1985 in a little over two months
...
Thus, the syntax of CLIPS was
made to very closely resemble the syntax of a subset of the ART expert system tool developed
by Inference Corporation
...

The original intent for CLIPS was to gain useful insight and knowledge about the construction of
expert system tools and to lay the groundwork for the construction of a replacement tool for the
commercial tools currently being used
...
0 demonstrated the feasibility of the project
concept
...
Another year of development and internal
use went into CLIPS improving its portability, performance, functionality, and supporting
documentation
...
0 of CLIPS was made available to groups outside of NASA in the
summer of 1986
...
Versions 4
...
1 of CLIPS, released
CLIPS Basic Programming Guide

iii

CLIPS Reference Manual

respectively in the summer and fall of 1987, featured greatly improved performance, external
language integration, and delivery capabilities
...
2 of CLIPS, released in the summer of
1988, was a complete rewrite of CLIPS for code modularity
...

Version 4
...

Originally, the primary representation methodology in CLIPS was a forward chaining rule language based on the Rete algorithm (hence the Production System part of the CLIPS acronym)
...
0 of CLIPS, released in the spring of 1991, introduced two new programming
paradigms: procedural programming (as found in languages such as C and Ada) and
object-oriented programming (as found in languages such as the Common Lisp Object System
and Smalltalk)
...
Version 5
...
Version 6
...
Version 6
...
Commands to profile the time spent in constructs and user-defined functions were
also added
...
2 of CLIPS, released in 2002, added support for multiple environments
into which programs can be loaded and improved Windows XP and MacOS development
interfaces
...
The development of
CLIPS has helped to improve the ability to deliver expert system technology throughout the
public and private sectors for a wide range of applications and diverse computing environments
...

CLIPS is now maintained as public domain software by the main program authors who no longer
work for NASA
...

CLIPS Version 6
...
3 of CLIPS contains two major enhancements
...

Second, support for integration with languages such as Java and C++ has been improved
...
x releases of CLIPS, refer to appendix B of the Basic
Programming Guide and appendix C of the Advanced Programming Guide
...

•

The CLIPS Reference Manual which is split into the following parts:
•

•

Volume II - The Advanced Programming Guide, which provides detailed discussions of
the more sophisticated features in CLIPS and is intended for people with extensive
programming experience who are using CLIPS for advanced applications
...


Volume III - The Interfaces Guide, which provides information on machine-specific
interfaces
...


CLIPS Basic Programming Guide

v

CLIPS Reference Manual

Acknowledgements
As with any large project, CLIPS is the result of the efforts of numerous people
...
Joseph Giarratano of the
University of Houston-Clear Lake, who wrote the CLIPS User’s Guide; and Frank Lopez, who
designed and developed CLIPS version 1
...
0 User’s Guide
...
J
...


CLIPS Basic Programming Guide

vii

CLIPS Reference Manual

Section 1 - Introduction
This manual is the Basic Programming Guide for CLIPS
...
No previous expert system background is required, although a general
understanding of computer languages is assumed
...
Sections 3 through 11 provide additional details
regarding the CLIPS programming language on topics such as rules and the CLIPS Object
Oriented Programming Language (COOL)
...
Finally, commands typically used from the CLIPS interactive
interface are described in section 13
...
More advanced
capabilities, such as user-defined functions, embedded applications, etc
...
The Advanced Programming Guide is intended for
users who have a complete knowledge of the CLIPS syntax and a programming background
...
CLIPS can
be learned and simple expert systems can be built with the information provided in this manual
...

2
...
Embedded applications are discussed in the Advanced
Programming Guide
...

The generic CLIPS interface is a simple, interactive, text-oriented, command prompt interface
for high portability
...
The interface provides commands for viewing the
current state of the system, tracing execution, adding or removing information, and clearing
CLIPS
...
1, and X
Window environments
...
These interfaces are described in more detail in the Interfaces Guide
...
1
...
When the “CLIPS>” prompt is printed, a command
may be entered for evaluation
...
If a function call is entered (see section 2
...
2), that function is evaluated
and its return value is printed
...
Entering a construct definition (see section
2
...
3) at the CLIPS prompt creates a new construct of the appropriate type
...
4
...
Local variables
can be set at the command prompt using the bind function and retain their value until a reset or
clear command is issued
...
Entering a constant (see section 2
...
1) at the top level causes the
constant to be printed (which is not very useful)
...
3 10/25/07)
CLIPS> (+ 3 4)
7
CLIPS Basic Programming Guide

3

CLIPS Reference Manual
CLIPS> (defglobal ?*x* = 3)
CLIPS> ?*x*
3
CLIPS> red
red
CLIPS> (bind ?a 5)
5
CLIPS> (+ ?a 3)
8
CLIPS> (reset)
CLIPS> ?a
[EVALUATN1] Variable a is unbound
FALSE
CLIPS>

The previous example first called the addition function adding the numbers 3 and 4 to yield the
result 7
...
The variable ?*x* was
then entered at the prompt and its value of 3 was returned
...

2
...
2 Automated Command Entry and Loading
Some operating systems allow additional arguments to be specified to a program when it begins
execution
...
The command-line syntax for starting CLIPS and automatically reading
commands or loading constructs from a file is as follows:
Syntax
clips *
::= -f |
-f2 |
-l

For the -f option, is a file that contains CLIPS commands
...
If an exit command is not in the file, CLIPS will enter in its
interactive state after executing the commands in the file
...
e
...
The -f command line option
is equivalent to interactively entering a batch command as the first command to the CLIPS
prompt
...
The commands stored in are immediately executed, but the commands
and their return values are not displayed as they would be for a batch command
...
This file will be
loaded into the environment
...

2
...
3 Integration with Other Languages
When using an expert system, two kinds of integration are important: embedding CLIPS in other
systems, and calling external functions from CLIPS
...

Using CLIPS as an embedded application allows the easy integration of CLIPS with existing
systems
...
In these situations, CLIPS can be called as a subroutine and
information may be passed to and from CLIPS
...

It also may be useful to call external functions while executing a CLIPS construct or from the
top-level of the interactive interface
...
The easy addition of external
functions allows CLIPS to be extended or customized in almost any way
...

2
...
Plain words or characters, particularly parentheses, are to be typed
exactly as they appear
...
Sequences of words enclosed in single-angle brackets (called terms or
non-terminal symbols), such as , represent a single entity of the named class of items to
be supplied by the user
...
A non-terminal symbol followed
by a +, represents one or more entities of the named class of items which must be supplied by the
user
...
Vertical and horizontal ellipsis (three dots
arranged respectively vertically and horizontally) are also used between non-terminal symbols to
indicate the occurrence of one or more entities
...
e
...
Vertical bars indicate a choice
between multiple terms
...
The ::=
symbol is used to indicate how a non-terminal symbol can be replaced
...

CLIPS Basic Programming Guide

5

CLIPS Reference Manual

::= |

A complete BNF listing for CLIPS constructs along with some commonly used replacements for
non-terminal symbols are listed in appendix I
...
3 BASIC PROGRAMMING ELEMENTS
CLIPS provides three basic elements for writing programs: primitive data types, functions for
manipulating data, and constructs for adding to a knowledge base
...
3
...
These types are float,
integer, symbol, string, external-address, fact-address, instance-name and instance-address
...
Symbolic information can be
represented using symbols and strings
...
), a sign (+ or -), and, optionally, an (e)
for exponential notation with its corresponding sign
...
Any number consisting of an optional sign followed by only digits is stored as an
integer (represented internally by CLIPS as a C long integer)
...
The number of significant
digits will depend on the machine implementation
...
As with any computer language, care should be taken
when comparing floating-point values to each other or comparing integers to floating-point
values
...
0

-32
...
09

Specifically, integers use the following format:
::= [+ | -] +
::= 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9

Floating point numbers use the following format:
::= |

...
[exponent]

...

A symbol in CLIPS is any sequence of characters that starts with any printable ASCII character
and is followed by zero or more printable ASCII characters
...
The following characters act as delimiters: any non-printable ASCII character
(including spaces, tabs, carriage returns, and line feeds), a double quote, opening and closing
parentheses “(” and “)”, an ampersand “&”, a vertical bar “|”, a less than “<”, and a tilde “~”
...
3
...
Delimiters
may not be included in symbols with the exception of the “<“ character which may be the first
character in a symbol
...
These characters
are reserved for variables (which are discussed later in this section)
...
e
...
Note that numbers are a special case of
symbols (i
...
they satisfy the definition of a symbol, but they are treated as a different data type)
...
A string ends with double quotes
...
A backslash may be embedded by
placing two consecutive backslash characters in the string
...
They both contain the same
characters, but are of different types
...

An external-address is the address of an external data structure returned by a function (written
in a language such as C or Ada) that has been integrated with CLIPS
...
e
...
In the basic version of CLIPS (which has no user defined external functions), it is not
possible to create this data type
...
Within CLIPS, the printed representation of an external-address
is


where XXXXXX is the external-address
...
Facts are referred to by index or address; section 2
...
1 gives
more details
...

An instance is an object that is an instantiation or specific example of a class
...
A user-defined class is created using the
defclass construct
...
Within the scope of a
module (see section 10
...
1), an instance can also be uniquely referred to by name
...
4
...
5
...
3, 2
...
An instance-name
is formed by enclosing a symbol within left and right brackets
...
If the CLIPS Object Oriented Language (COOL) is not included in a
particular CLIPS configuration, then brackets may be wrapped around symbols
...
An instance-address can only be obtained by binding the
return value of a function called instance-address or by binding a variable to an instance
matching an object pattern on the LHS of a rule (i
...
, it is not possible to specify an
instance-address by typing the value)
...

Within CLIPS, the printed representation of an instance-address is


where XXX is the name of the instance
...

The primitive data types are referred to as single-field values
...
A multifield
value is a sequence of zero or more single field values
...
Collectively, single and multifield values are referred to as
values
...
0 "red" 567)

Note that the multifield value (a) is not the same as the single field value a
...
In CLIPS, a variable is a symbolic location that is used to
store values
...

2
...
2 Functions
A function in CLIPS is a piece of executable code identified by a specific name which returns a
useful value or performs a useful side effect (such as displaying information)
...

There are several types of functions
...
System defined functions are those functions that have
been defined internally by the CLIPS environment
...
A complete list of system defined
functions can be found in appendix J
...
Functions defined in this manner appear and act like other
functions, however, instead of being directly executed (as code written in an external language
would be) they are interpreted by the CLIPS environment
...
5
...
1 in the context of procedural knowledge representation
...
Generic
functions allow different pieces of code to be executed depending upon the arguments passed to
the generic function
...
Generic functions are also discussed in section 2
...
2
...

CLIPS Basic Programming Guide

9

CLIPS Reference Manual

Function calls in CLIPS use a prefix notation – the arguments to a function always appear after
the function name
...
Arguments to a function can be primitive data types, variables, or another function call
...
Some examples of function calls using
the addition (+) and multiplication (*) functions are shown following
...
0 2)
(* 8 9) 4)
(+ 3 (* 2 3 4) 9) (* 3 4))

While a function refers to a piece of executable code identified by a specific name, an
expression refers to a function which has its arguments specified (which may or may not be
functions calls as well)
...

2
...
3 Constructs
Several defining constructs appear in CLIPS: defmodule, defrule, deffacts, deftemplate,
defglobal, deffunction, defclass, definstances, defmessage-handler, defgeneric, and
defmethod
...
The construct opens with a
left parenthesis and closes with a right parenthesis
...
Typically a function call leaves the CLIPS environment unchanged
(with some notable exceptions such as resetting or clearing the environment or opening a file)
...
Unlike function calls, constructs never have a return value
...
All
constructs (with the exception of defglobal) allow a comment directly following the construct
name
...
Everything
from the semicolon until the next return character will be ignored by CLIPS
...
Examples of
commented code will be provided throughout the reference manual
...

2
...


10

Section 2 - CLIPS Overview

CLIPS Reference Manual

2
...
1 Facts
Facts are one of the basic high-level forms for representing information in a CLIPS system
...
Facts are the fundamental unit of data used by rules (see section 2
...
1)
...
The
number of facts in the fact-list and the amount of information that can be stored in a fact is
limited only by the amount of memory in the computer
...
4
...
4
...

Some commands, such as the retract, modify, and duplicate commands, require a fact to be
specified
...
Whenever a fact is added
(or modified) it is given a unique integer index called a fact-index
...
Whenever a reset or clear command is
given, the fact-indices restart at zero
...
A fact-address can be obtained by capturing the return value of commands which
return fact addresses (such as assert, modify, and duplicate) or by binding a variable to the fact
address of a fact which matches a pattern on the LHS of a rule (see section 5
...
1
...

A fact identifier is a shorthand notation for displaying a fact
...
For example, f-10 refers to the fact
with fact-index 10
...

2
...
1
...

The first field of an ordered fact specifies a “relation” that applied to the remaining fields in the
ordered fact
...

Some examples of ordered facts are shown following
...
The
following symbols are reserved and should not be used as the first field in any fact (ordered or
non-ordered): test, and, or, not, declare, logical, object, exists, and forall
...
These
symbols may be used as slot names, however, this is not recommended
...
4
...
2 Non-ordered Facts
Ordered facts encode information positionally
...
Non-ordered (or
deftemplate) facts provide the user with the ability to abstract the structure of a fact by assigning names to each field in the fact
...
The deftemplate construct is
analogous to a record or structure definition in programming languages such as Pascal and C
...
Unlike ordered facts, the slots of a deftemplate fact may be
constrained by type, value, and numeric range
...
A slot consists of an opening parenthesis followed by the name of the slot, zero or more
fields, and a closing parenthesis
...

Deftemplate facts are distinguished from ordered facts by the first field within the fact
...
The first field of a deftemplate fact is followed by
a list of zero or more slots
...

Some examples of deftemplate facts are shown following
...
For example the following facts
are all identical:
(class (teacher "Martha Jones") (#-students 30) (Room "37A"))
(class (#-students 30) (teacher "Martha Jones") (Room "37A"))
(class (Room "37A") (#-students 30) (teacher "Martha Jones"))

In contrast, note that the following ordered fact are not identical
...

In addition to being asserted and retracted, deftemplate facts can also be modified and duplicated
(using the modify and duplicate commands)
...
Duplicating a fact creates a new fact identical to the original fact and then
changes a set of specified slots within the new fact
...

2
...
1
...
When the CLIPS environment is reset (using the reset command) every fact specified
within a deffacts construct in the CLIPS knowledge base is added to the fact-list
...
4
...
Section 2
...
1 explains
how to reference instances of user-defined classes
...
A class is a template for common properties and behavior of objects
which are instances of that class
...
0
8
(8
...
These two types of objects differ in the way they are referenced, created
and deleted as well as how their properties are specified
...
Primitive type objects have no names or slots,
and their classes are predefined by CLIPS
...
It is anticipated that primitive types will not be used often in
an object-oriented programming (OOP) context; the main reason classes are provided for them is
for use in generic functions
...
3
...
5
...
2 and 8 give more detail
...
The properties of an instance of a
user-defined class are expressed by a set of slots, which the object obtains from its class
...
For example, the object
Rolls-Royce is an instance of the class CAR
...
00
...
Message-handlers and manipulation of objects are described in Section 2
...
2
...
All
instances of a user-defined class have the same set of slots, but each instance may have different
values for those slots
...

The primary difference between object slots and template (or non-ordered) facts is the notion of
inheritance
...
COOL supports multiple inheritance: a class may directly inherit slots and
message-handlers from more than one class
...
This is because these classes cannot have slots and usually
do not have message-handlers
...
6, and a comprehensive description
of the CLIPS Object-Oriented Language (COOL) can be found in Section 9
...
4
...
1 Initial Objects
The definstances construct allows a set of a priori or initial knowledge to be specified as a
collection of instances of user-defined classes
...

2
...
3 Global Variables
The defglobal construct allows variables to be defined which are global in scope throughout the
CLIPS environment
...
In contrast, some constructs
(such as defrule and deffunction) allow local variables to be defined within the definition of the
14

Section 2 - CLIPS Overview

CLIPS Reference Manual

construct
...
A CLIPS global variable is similar to global variables found in procedural
programming languages such as LISP, C and Ada
...

2
...
These two
paradigms are discussed in this section
...
6
...
5
...
Rules are used to
represent heuristics, or “rules of thumb”, which specify a set of actions to be performed for a
given situation
...
A rule is composed of an antecedent and a consequent
...

The consequent of a rule is also referred to as the then portion or the right-hand side (RHS) of
the rule
...
In CLIPS, the conditions of a rule are satisfied based on the
existence or non-existence of specified facts in the fact-list or specified instances of user-defined
classes in the instance-list
...
Patterns
consist of a set of restrictions which are used to determine which facts or objects satisfy the
condition specified by the pattern
...
CLIPS provides a mechanism, called the inference engine, which
automatically matches patterns against the current state of the fact-list and instance-list and
determines which rules are applicable
...
The
actions of applicable rules are executed when the CLIPS inference engine is instructed to begin
execution of applicable rules
...
The actions of
the selected rule are executed (which may affect the list of applicable rules) and then the
inference engine selects another rule and executes its actions
...

In many ways, rules can be thought of as IF-THEN statements found in procedural programming
languages such as C and Ada
...
In contrast, rules act like WHENEVER-THEN statements
...
In this sense, rules are similar to exception handlers found
in languages such as Ada
...
5
...
Deffunctions and generic functions allow the user
to define new executable elements to CLIPS that perform a useful side-effect or return a useful
value
...

Message-handlers allow the user to define the behavior of objects by specifying their response to
messages
...

Defmodules allow a knowledge base to be partitioned
...
5
...
1 Deffunctions
Deffunctions allow you to define new functions in CLIPS directly
...
The
body of a deffunction is a series of expressions similar to the RHS of a rule that are executed in
order by CLIPS when the deffunction is called
...
Calling a deffunction is identical to calling
any other function in CLIPS
...

2
...
2
...
However, generic
functions are much more powerful because they can be overloaded
...
Generic
functions are comprised of multiple components called methods, where each method handles
different cases of arguments for the generic function
...
However, the “+”
operator will still perform arithmetic addition when passed numbers
...
The return value of a generic function is the
evaluation of the last expression in the method executed
...


16

Section 2 - CLIPS Overview

CLIPS Reference Manual

2
...
2
...
Object properties are specified
in terms of slots obtained from the object’s class; slots are discussed in more detail in Section
2
...
2
...
Objects are manipulated via message-passing
...
How the
Rolls-Royce responds to this message will be dictated by the execution of the message-handlers
for “start-engine” attached to the CAR class and any of its superclasses
...

Further discussion on message-handlers can be found in Section 2
...

2
...
2
...
Every construct defined must be placed
in a module
...
The visibility of
facts and instances between modules can be controlled in a similar manner
...
Defmodules are covered comprehensively in
Section 10
...
6 CLIPS OBJECT-ORIENTED LANGUAGE
This section gives a brief overview of the programming elements of the CLIPS Object-Oriented
Language (COOL)
...

This section gives an overview of COOL as a whole, incorporating the elements of both
concepts
...
3
...
4
...
5
...
3
...

2
...
1 COOL Deviations from a Pure OOP Paradigm
In a pure OOP language, all programming elements are objects which can only be manipulated
via messages
...
All objects may be manipulated with messages, except
instances of user-defined classes, which must be
...
In CLIPS, you may simply call the “+” function with the two
CLIPS Basic Programming Guide

17

CLIPS Reference Manual

numbers as arguments, or you can define message-handlers for the NUMBER class which allow
you to do it in the purely OOP fashion
...
For example, to print a rule, you call the
function ppdefrule; you do not send a message “print” to a rule, since it is not an object
...
6
...
An abstraction is a higher
level, more intuitive representation for a complex concept
...
Classes
may be described in terms of other classes by use of inheritance
...
Dynamic binding is the
ability to defer the selection of which specific message-handlers will be called for a message
until run-time
...
The slots and
message-handlers of these classes describe the properties and behavior of a new group of objects
...
An instance cannot respond to a message for which it does not have a
defined message-handler
...
This process is called multiple inheritance
...
Objects which are instances of this new class can inherit properties (slots) and
behavior (message-handlers) from each of the classes in the class precedence list
...

One COOL object can respond to a message in a completely different way than another object;
this is polymorphism
...

Dynamic binding is supported in that an object reference (see section 2
...
1) in a send function
call is not bound until run-time
...


18

Section 2 - CLIPS Overview

CLIPS Reference Manual

2
...
3 Instance-set Queries and Distributed Actions
In addition to the ability of rules to directly pattern-match on objects, COOL provides a useful
query system for determining, grouping and performing actions on sets of instances of
user-defined classes that meet user-defined criteria
...
You can simply use the query system to determine if a
particular association set exists, you can save the set for future reference, or you can iterate an
action over the set
...


CLIPS Basic Programming Guide

19

CLIPS Reference Manual

Section 3 - Deftemplate Construct
Ordered facts encode information positionally
...
Non-ordered (or deftemplate)
facts provide the user with the ability to abstract the structure of a fact by assigning names to
each field found within the fact
...
The deftemplate
construct is analogous to a record or structure definition in programming languages such as
Pascal and C
...
A deftemplate
can not be redefined while it is being used (for example, by a fact or pattern in a rule)
...
CLIPS always enforces the single
and multifield definitions of the deftemplate
...

Example

(deftemplate object
(slot name)
(slot location)
(slot on-top-of)
(slot weight)
(multislot contents))

CLIPS Basic Programming Guide

21

CLIPS Reference Manual

3
...
One of two types of default selections can be chosen: default
or dynamic-default
...
The specified expressions are evaluated
once when the deftemplate is defined and the result is stored with the deftemplate
...
If the keyword ?DERIVE is
used for the default value, then a default value is derived from the constraints for the slot (see
section 11
...
By default, the default attribute for a slot is (default ?DERIVE)
...
It is an error to assert a template fact without specifying the
values for the (default ?NONE) slots
...
The specified expressions are evaluated
every time a template fact is asserted, and the result is assigned to the appropriate slot
...
Any number of values may be
specified as the default for a multifield slot (as long as the number of values satisfies the
cardinality attribute for the slot)
...

CLIPS> (assert (foo (w 3)))

CLIPS> (assert (foo (w 4)))

CLIPS> (facts)
f-0
(foo (w 3) (x nil) (y gen1) (z gen2))
f-1
(foo (w 4) (x nil) (y gen1) (z gen3))
For a total of 2 facts
...
2 SLOT DEFAULT CONSTRAINTS FOR PATTERN-MATCHING
Single-field slots that are not specified in a pattern on the LHS of a rule are defaulted to
single-field wildcards (?) and multifield slots are defaulted to multifield wildcards ($?)
...
3 SLOT VALUE CONSTRAINT ATTRIBUTES
The syntax and functionality of single and multifield constraint attributes are described in detail
in Section 11
...
Static
checking is performed when constructs or commands using deftemplates slots are being parsed
(and the specific deftemplate associated with the construct or command can be immediately
determined)
...
Errors for inappropriate
values are immediately signaled
...

Static checking is enabled by default
...
Dynamic checking is also supported
...
This dynamic checking is disabled by default
...
If a violation occurs when dynamic checking is
being performed, then execution will be halted
...
4 IMPLIED DEFTEMPLATES
Asserting or referring to an ordered fact (such as in a LHS pattern) creates an “implied”
deftemplate with a single implied multifield slot
...
The implied deftemplate can be manipulated and examined
identically to any user defined deftemplate (although it has no pretty print form)
...

CLIPS> (facts)
f-0
(foo 1 2 3)
For a total of 1 fact
...
Facts asserted through deffacts may be retracted or
pattern-matched like any other fact
...

Syntax

(deffacts []
*)

Redefining a currently existing deffacts causes the previous deffacts with the same name to be
removed even if the new definition has errors in it
...

Dynamic expressions may be included in a fact by embedding the expression directly within the
fact
...

Example
(deffacts startup "Refrigerator Status"
(refrigerator light on)
(refrigerator door open)
(refrigerator temp (get-temp)))

Upon startup and after a clear command, CLIPS automatically constructs the following
deftemplate and deffacts
...

Important Note
Once created, the initial-fact deffacts and deftemplate are treated just as any other deffacts or
deftemplate defined by the user would be—All of the functions and commands appropriate for
these constructs can be applied to them
...
Similarly,
the initial-fact fact asserted by the initial-fact deffacts when a reset command is issued, should
never be retracted by a program
...
A rule is a collection
of conditions and the actions to be taken if the conditions are met
...
Rules execute (or fire) based on
the existence or non-existence of facts or instances of user-defined classes
...

Throughout this section, the term pattern entity will be used to refer to either a fact or an
instance of a user-defined class
...
1 DEFINING RULES
Rules are defined using the defrule construct
...
The LHS is made up of a series of conditional
elements (CEs) which typically consist of pattern conditional elements (or just simply patterns)
to be matched against pattern entities
...
The RHS contains a list of actions to be performed when the LHS of the
rule is satisfied
...
4
...
The arrow (=>) separates the LHS from the RHS
...
Actions are performed sequentially if, and only if, all conditional elements on the
LHS are satisfied
...
If no actions are on the RHS, the rule can be activated and fired but nothing
will happen
...
This means that CEs in newly defined rules
can be satisfied by pattern entities at the time the rule is defined, in addition to pattern entities
created after the rule is defined (see sections 13
...
8, 13
...
9, and 13
...
10 for more details)
...
2 BASIC CYCLE OF RULE EXECUTION
Once a knowledge base (in the form of rules) is built and the fact-list and instance-list is
prepared, CLIPS is ready to execute rules
...
With
CLIPS, the program flow does not need to be defined quite so explicitly
...
The basic execution cycle is as follows:
a) If the rule firing limit has been reached or there is no current focus, then execution is halted
...
If there are no rules on that agenda, then the current focus is removed from
the focus stack and the current focus becomes the next module on the focus stack
...
See
sections 5
...
10
...
6, 12
...
7 for information on the focus stack and the current
focus
...
The use of the return
function on the RHS of a rule may remove the current focus from the focus stack (see
sections 10
...
6
...
The number of rules fired is incremented for use with the rule
firing limit
...
Activated rules (those rules
whose conditions are currently satisfied) are placed on the agenda of the module in which
they are defined
...
3, 5
...
10, 13
...
5, and 13
...
6)
...
If the activations item is being watched (see
section 13
...

d) If dynamic salience is being used, the salience values for all rules on the agenda are
reevaluated (see sections 5
...
10, 13
...
9, and 13
...
10)
...


28

Section 5 - Defrule Construct

CLIPS Reference Manual

5
...
Each module has its own agenda
...
When a rule is newly activated, its placement on the
agenda is based (in order) on the following factors:
a) Newly activated rules are placed above all rules of lower salience and below all rules of
higher salience
...

c) If a rule is activated (along with several other rules) by the same assertion or retraction of a
fact, and steps a and b are unable to specify an ordering, then the rule is arbitrarily (not
randomly) ordered in relation to the other rules with which it was activated
...
Do not
depend upon this arbitrary ordering for the proper execution of your rules
...
The default strategy is depth
...

5
...
1 Depth Strategy
Newly activated rules are placed above all rules of the same salience
...
However, the
position of rule-1 relative to rule-2 and rule-3 relative to rule-4 will be arbitrary
...
3
...
For example, given that
fact-a activates rule-1 and rule-2 and fact-b activates rule-3 and rule-4, then if fact-a is asserted
before fact-b, rule-1 and rule-2 will be above rule-3 and rule-4 on the agenda
...

5
...
3 Simplicity Strategy
Among rules of the same salience, newly activated rules are placed above all activations of rules
with equal or higher specificity
...
Each comparison to a constant or
previously bound variable adds one to the specificity
...
The boolean
functions and, or, and not do not add to the specificity of a rule, but their arguments do
...
For example,
the following rule
(defrule example
(item ?x ?y ?x)
(test (and (numberp ?x) (> ?x (+ 10 ?y)) (< ?x 100)))
=>)

has a specificity of 5
...
The calls to the and and + functions do not add to the specificity of the rule
...
3
...

5
...
5 LEX Strategy
Among rules of the same salience, newly activated rules are placed using the OPS5 strategy of
the same name
...
Every fact and instance is marked internally with a “time tag” to
indicate its relative recency with respect to every other fact and instance in the system
...
An activation with a more recent pattern entities is placed before
activations with less recent pattern entities
...

The comparison should continue until one activation’s time tag is greater than the other
activation’s corresponding time tag
...

If one activation has more pattern entities than the other activation and the compared time tags
are all identical, then the activation with more time tags is placed before the other activation on
the agenda
...
Unlike OPS5, the not
conditional elements in CLIPS have pseudo time tags which are used by the LEX conflict
resolution strategy
...


30

Section 5 - Defrule Construct

CLIPS Reference Manual

As an example, the following six activations have been listed in their LEX ordering (where the
comma at the end of the activation indicates the presence of a not CE)
...
For this
example, assume that the time tags and indices are the same
...

rule-6:
rule-5:
rule-1:
rule-2:
rule-4:
rule-3:

f-4,f-1
f-3,f-2,f-1,
f-3,f-2,f-1
f-3,f-1
f-2,f-1,
f-2,f-1

5
...
6 MEA Strategy
Among rules of the same salience, newly activated rules are placed using the OPS5 strategy of
the same name
...
An activation thats first pattern’s time tag is greater than
another activations first pattern’s time tag is placed before the other activation on the agenda
...
Again, as with the CLIPS LEX strategy, negated
patterns have pseudo time tags
...

rule-2:
rule-3:
rule-6:
rule-5:
rule-1:
rule-4:

f-3,f-1
f-2,f-1
f-1,f-4
f-1,f-2,f-3,
f-1,f-2,f-3
f-1,f-2,

5
...
7 Random Strategy
Each activation is assigned a random number which is used to determine its placement among
activations of equal salience
...

Usage Note
A conflict resolution strategy is an implicit mechanism for specifying the order in which rules of
equal salience should be executed
...
Because the mechanism is implicit, it’s not possible to
determine the programmer’s original intent simply by looking at the code
...
] Rather than explicitly indicating that rule A should be executed before rule B, the
order of execution is implicitly determined by the order in which facts are asserted and the
complexity of the rules
...

Because they require explicit declarations, the preferred mechanisms in CLIPS for ordering the
execution of rules are salience and modules
...
Modules allow one to explicitly specify that all of
the rules in a particular group (module) should be executed before all of the rules in a different
group
...
For example, the following two rules need
correction because they can be activated at the same time, but the order in which they execute
matters:
(defrule rule-1
(factoid a)
=>
(assert (factoid b)))
(defrule rule-2
?f <- (factoid a)
(factoid d)
=>
(retract ?f)
(assert (factoid c)))

Programmers should also be careful to avoid overusing salience
...
It’s rarely necessary to use more
than five to ten salience values in a well-designed program
...
The breadth,
simplicity, and complexity strategies are provided largely for academic reasons (i
...
the study of
32

Section 5 - Defrule Construct

CLIPS Reference Manual

conflict resolution strategies)
...

The random strategy is useful for testing
...
Before running a program with the random strategy,
first seed the random number generator using the seed function
...

5
...
The LHS of a CLIPS rule is made
up of a series of conditional elements (CEs) that must be satisfied for the rule to be placed on the
agenda
...
The pattern CE is the most basic and
commonly used conditional element
...
The test CE is used to
evaluate expressions as part of the pattern-matching process
...
The or CE is used to specify that only one of a
group of CEs must be satisfied
...

The exists CE is used to test for the occurence of at least one partial match for a set of CEs
...

Finally, the logical CE allows assertions of facts and the creation of instances on the RHS of a
rule to be logically dependent upon pattern entities matching patterns on the LHS of a rule (truth
maintenance)
...
4
...
A
pattern CE is satisfied by each and every pattern entity that satisfies its constraints
...
A
field constraint may consist of only a single literal constraint, however, it may also consist of
CLIPS Basic Programming Guide

33

CLIPS Reference Manual

several constraints connected together
...
Wildcards are used within pattern CEs to indicate that a single field or group of
fields can be matched by anything
...

The first field of any pattern must be a symbol and can not use any other constraints
...
The symbol object is reserved to indicate an object pattern
...
Slot names
must also be symbols and cannot contain any other constraints
...
A multifield slot can contain any number of field constraints
...
Section 5
...
1
...
The following constructs are used by the examples
...
0 blue "red")
(data 1 blue)
(data 1 blue red)
(data 1 blue RED)
(data 1 blue red 6
...
4
...
1 Literal Constraints
The most basic constraint which can be used in a pattern CE is one which precisely defines the
exact value that will match a field
...
A literal pattern CE
consists entirely of constants such as floats, integers, symbols, strings, and instance names
...
All constraints in a literal pattern must be matched
exactly by all fields of a pattern entity
...
)

A deftemplate pattern conditional element containing only literals has the following basic syntax:
( ( )

•
•
•

( ))

Example 1
This example utilizes the data-facts deffacts shown in section 5
...
1
...

CLIPS> (facts)
f-0
(initial-fact)
f-1
(data 1
...
9)
For a total of 6 facts
...
4
...

CLIPS> (clear)
CLIPS>
(defrule Find-Bob
(person (name Bob) (age 20))
=>)
CLIPS>
(defrule Find-Sue
(person (age 34) (name Sue))
=>)
CLIPS> (reset)
CLIPS> (agenda)
0
Find-Sue: f-4
0
Find-Bob: f-2
For a total of 2 activations
...

CLIPS>

(age
(age
(age
(age
(age

20)
20)
34)
34)
20)

(friends))
(friends))
(friends))
(friends))
(friends))

5
...
1
...
CLIPS interprets
these wildcard symbols as standing in place of some part of a pattern entity
...
The multifield wildcard, denoted by a dollar sign followed by a
question mark ($?), matches any value in zero or more fields in a pattern entity
...
It is illegal to use a
multifield wildcard in a single field slot of a deftemplate or object pattern
...
Similarly, an unspecified multifield slot in a deftemplate/object pattern is
matched against an implied multifield-wildcard
...
)

where
::= | ? | $?

A deftemplate pattern conditional element containing only literals and wildcards has the
following basic syntax:
( ( )

•
•
•
( ))

Example 1
This example utilizes the data-facts deffacts shown in section 5
...
1
...

CLIPS> (facts)
f-0
(initial-fact)
f-1
(data 1
...
9)
For a total of 6 facts
...
4
...

CLIPS> (clear)
CLIPS>
(defrule match-all-persons
(person)
=>)
CLIPS> (reset)
CLIPS> (agenda)
0
match-all-persons: f-5
0
match-all-persons: f-4
0
match-all-persons: f-3
0
match-all-persons: f-2
0
match-all-persons: f-1
For a total of 5 activations
...

CLIPS>

20)
20)
34)
34)
20)

(friends))
(friends))
(friends))
(friends))
(friends))

Multifield wildcard and literal constraints can be combined to yield some powerful
pattern-matching capabilities
...
The use of multifield
wildcards should be confined to cases of patterns in which the single-field wildcard cannot create
a pattern that satisfies the match required, since the multifield wildcard produces every possible
match combination that can be derived from a pattern entity
...

5
...
1
...
The value of the field being
replaced may be captured in a variable for comparison, display, or other manipulations
...

Syntax
Expanding on the syntax definition given in section 5
...
1
...
Double quotes are not allowed as part of a variable name; i
...
a string cannot be used for a
variable name
...
On its
first appearance, a variable acts just like a wildcard in that it will bind to any value in the field(s)
...
The binding will only be true within the scope of the rule in which it occurs
...

Bound variables can be passed to external functions
...

In other places (such as the RHS of a rule), the $ in front of a variable indicates that sequence
expansion should take place before calling the function
...
All other uses of a multifield variable on the
LHS of a rule, however, should use the $
...

Example 1

CLIPS> (clear)
CLIPS> (reset)

38

Section 5 - Defrule Construct

CLIPS Reference Manual
CLIPS> (assert (data 2 blue green)
(data 1 blue)
(data 1 blue red))

CLIPS> (facts)
f-0
(initial-fact)
f-1
(data 2 blue green)
f-2
(data 1 blue)
f-3
(data 1 blue red)
For a total of 4 facts
...
9))

CLIPS> (facts)
f-0
(initial-fact)
f-1
(data 1 blue)
f-2
(data 1 blue red)
f-3
(data 1 blue red 6
...

CLIPS>
(defrule find-data-1
(data ?x $?y ?z)
=>
(printout t "?x = " ?x crlf
"?y = " ?y crlf
"?z = " ?z crlf
"------" crlf))
CLIPS> (run)
?x = 1
?y = (blue red)
?z = 6
...
This applies to both single- and multifield variables
...

Example 3

CLIPS> (clear)
CLIPS>
(deffacts data
(data red green)
(data purple blue)
(data purple green)
(data red blue green)
(data purple blue green)
(data purple blue brown))
CLIPS>
(defrule find-data-1
(data red ?x)
(data purple ?x)
=>)
CLIPS>
(defrule find-data-2
(data red $?x)
(data purple $?x)
=>)
CLIPS> (reset)
CLIPS> (facts)
f-0
(initial-fact)
f-1
(data red green)
f-2
(data purple blue)
f-3
(data purple green)
f-4
(data red blue green)
f-5
(data purple blue green)
f-6
(data purple blue brown)
For a total of 7 facts
...

CLIPS>

5
...
1
...
These are the & (and), | (or), and ~ (not) connective constraints
...
The | constraint is satisfied if either of the
two adjoining constraints is satisfied
...
The connective constraints can be combined in almost any manner or number to
constrain the value of specific fields while pattern-matching
...
Otherwise, evaluation of
multiple constraints can be considered to occur from left to right
...
If the first constraint is a
variable followed by an & connective constraint, then the first constraint is treated as a separate
constraint which also must be satisified
...

Basic Syntax
Connective constraints have the following basic syntax:
&
...
|
~

where could be a single-field variable, multifield variable, constant, or connected
constraint
...
4
...
3 now gives:
::= ? | $? |

::= |
& |
|
::= | ~
::= |
|


The & constraint typically is used only in conjunction with other constraints or variable bindings
...
If the first
term of a connective constraint is the first occurrence of a variable name, then the field will be
constrained only by the remaining field constraints
...
If the variable has been bound previously, it is considered an additional constraint
along with the remaining field constraints; i
...
, the field must have the same value already bound
to the variable and must satisfy the field constraints
...

CLIPS> (agenda)
0
example1-2: f-4
0
example1-3: f-3
0
example1-1: f-1
For a total of 3 activations
...

CLIPS> (agenda)
0
example3-3: f-1,f-4
0
example3-3: f-2,f-4
0
example3-2: f-2,f-4
0
example3-1: f-2,f-3
For a total of 4 activations
...
4
...
5 Predicate Constraints
Sometimes it becomes necessary to constrain a field based upon the truth of a given boolean
expression
...
The
predicate constraint allows a predicate function (one returning the symbol FALSE for
unsatisfied and a non-FALSE value for satisfied) to be called during the pattern-matching
process
...
If the
predicate function returns the symbol FALSE, the constraint is not satisfied
...
Typically, predicate constraints are used in conjunction with a connective constraint
and a variable binding (i
...
you have to bind the variable to be tested and then connect it to the
predicate constraint)
...
4
...
4 now gives:
::= |
|
|
:

Multiple predicate constraints may be used to constrain a single field
...
2)
...

Example 1
CLIPS> (clear)
CLIPS>
(defrule example-1
(data ?x&:(numberp ?x))
=>)
CLIPS> (assert (data 1) (data 2) (data red))

CLIPS> (agenda)
0
example-1: f-1
0
example-1: f-0
For a total of 2 activations
...

CLIPS>

Example 3
CLIPS> (clear)
CLIPS>
(defrule example-3
(data ?x&:(numberp ?x)&:(oddp ?x))
=>)
CLIPS> (assert (data 1) (data 2) (data red))

CLIPS> (agenda)
0
example-3: f-0
For a total of 1 activation
...

CLIPS>

Example 5
CLIPS> (clear)
CLIPS>
(defrule example-5
(data $?x&:(> (length$ ?x)
=>)
CLIPS> (assert (data 1)
(data 1 2)
(data 1 2 3))

CLIPS> (agenda)
0
example-5: f-2
For a total of 1 activation
...
4
...
6 Return Value Constraints
It is possible to use the return value of an external function to constrain the value of a field
...
(This
constraint is different from the comparison function which uses the same symbol
...
) The return value must be one of the primitive data types
...
Note that the function is evaluated each time the constraint is
checked (not just once)
...
4
...
5 now gives:
::= |
|
|
CLIPS Basic Programming Guide

45

CLIPS Reference Manual
: |
=

Example 1

CLIPS> (clear)
CLIPS> (deftemplate data (slot x) (slot y))
CLIPS>
(defrule twice
(data (x ?x) (y =(* 2 ?x)))
=>)
CLIPS> (assert (data (x 2) (y 4)) ; f-0
(data (x 3) (y 9))) ; f-1

CLIPS> (agenda)
0
twice: f-0
For a total of 1 activation
...

CLIPS>

5
...
1
...

Patterns can only match objects for which the object’s most specific class is defined before the
pattern and which are in scope for the current module
...
Even if a rule
is deleted by its RHS, the classes bound to its patterns cannot be changed until after the RHS
finishes executing
...

However, when a slot is changed, only those patterns which explicitly match on that slot are
affected
...

Changes to non-reactive slots or instances of non-reactive classes (see sections 9
...
2
...
3
...
7) will have no effect on rules
...

Syntax


::= (object *)

::= (is-a ) |
(name ) |
( *)

The is-a constraint is used for specifying class constraints such as “Is this object a member of
class FOO?”
...
The name constraint is used for specifying a specific
instance on which to pattern-match
...
Multifield constraints (such as $?) cannot be used with the is-a
or name constraints
...
As with deftemplate patterns, slot names for
object patterns must be symbols and can not contain any other constraints
...

(defrule class-match-1
(object)
=>)
(defrule class-match-2
(object (is-a FOO))
=>)
(defrule class-match-3
(object (is-a FOO | BAR))
=>)
(defrule class-match-4
(object (is-a ?x))
(object (is-a ~?x))
=>)

CLIPS Basic Programming Guide

47

CLIPS Reference Manual

Rule class-match-1 is satisified by all instances of any reactive class
...
Rule class-match-3 is satisfied by all instances of class
FOO or BAR
...

Example 2
The following rules illustrate pattern-matching on various attributes of an object's slots
...
Rule slot-match-2 is satisfied by all instances of reactive
classes that contain a reactive single or multifield width slot that is bound to a single value
...
Note that a slot containing a zero
length multifield value would satisfy rules slot-match-1 and slot-match-3, but not rule
slot-match-2 (because the value's cardinality is zero)
...

(defrule value-match-1
(object (width 10)
=>)
(defrule value-match-2
(object (width ?x&:(> ?x 20)))
=>)
(defrule value-match-3
(object (width ?x) (height ?x))
=>)

Rule value-match-1 is satisified by all instances of reactive classes that contain a reactive width
slot with value 10
...
Rule value-match-3 is satisfied by all
instances of reactive classes that contain a reactive width and height slots with the same value
...
4
...
8 Pattern-Addresses
Certain RHS actions, such as retract and unmake-instance, operate on an entire pattern CE
...
Collectively, fact-addresses and instance-addresses bound
on the LHS of a rule are referred to as pattern-addresses
...
A variable bound to a fact-address or
instance-address can be compared to other variables or passed to external functions
...
It is an error to bind a varible to a not CE
...
4
...
Additional capability is provided with the test conditional element
...
As with predicate constraints, the user can
compare the variable bindings that already have occurred in any manner
...
g
...
External functions also can be called
which compare variables in any way that the user desires
...
User-defined predicate functions must take arguments as defined in the
Advanced Programming Guide
...
1)
...
A test CE is evaluated when all proceeding CEs are
satisfied
...
In order to cause the reevaluation of a test
CE, a pattern entity matching a CE prior to the test CE must be changed
...
In addition, test CEs may also be automatically
reordered by CLIPS
...
4
...

Example 1
This example checks to see if the difference between two numbers is greater than or equal to
three:
CLIPS> (clear)
CLIPS>
(defrule example-1
(data ?x)
(value ?y)
(test (>= (abs (- ?y ?x)) 3))
=>)
CLIPS> (assert (data 6) (value 9))

CLIPS> (agenda)
0
example-1: f-0,f-1
For a total of 1 activation
...

CLIPS> (clear)
CLIPS>
(deffunction positive-slope
(?x1 ?y1 ?x2 ?y2)
(< 0 (/ (- ?y2 ?y1) (- ?x2 ?x1))))
CLIPS>
(defrule example-2
(point ?a ?x1 ?y1)
(point ?b ?x2 ?y2)
50

Section 5 - Defrule Construct

CLIPS Reference Manual
(test (> ?b ?a))
(test (positive-slope ?x1 ?y1 ?x2 ?y2))
=>)
CLIPS>
(assert (point 1 4
...
0) (point 2 5
...
0))

CLIPS> (agenda)
0
example-2: f-0,f-1
For a total of 1 activation
...
In addition, the initial-fact fact asserted or initial-object instance created when a
reset command is issued should never be retracted or deleted by a program
...
4
...
If
any of the conditional elements inside of the or CE is satisfied, then the or CE is satisfied
...
Note that a rule will be
activated for each conditional element with an or CE that is satisfied (assuming the other
conditional elements of the rule are also satisfied)
...
The or CE produces the identical effect of writing several rules with
similar LHS’s and RHS’s
...

Example
(defrule system-fault
(error-status unknown)
(or (temp high)
(valve broken)
(pump (status off)))
=>
(printout t "The system has a fault
...
" crlf))
(defrule system-fault
(error-status unknown)
(valve broken)
=>
(printout t "The system has a fault
...
" crlf))

5
...
4 And Conditional Element
CLIPS assumes that all rules have an implicit and conditional element surrounding the
conditional elements on the LHS
...
An explicit and conditional element is provided to
allow the mixing of and CEs and or CEs
...
The and CE is satisfied if all of the CEs inside of the
explicit and CE are satisfied
...
Any
number of conditional elements may be placed within an and CE
...
" crlf))

An and CE that has a test or not CE as its first CE has the pattern (initial-fact) or (initial-object)
added as the first CE
...
For
example, the following rule
(defrule nothing-to-schedule
(not (schedule ?))
=>
(printout t "Nothing to schedule
...
" crlf))

5
...
5 Not Conditional Element
Sometimes the lack of information is meaningful; i
...
, one wishes to fire a rule if a pattern entity
or other CE does not exist
...
The not CE is
satisfied only if the conditional element contained within it is not satisfied
...

Syntax

::= (not )

Only one CE may be negated at a time
...
Care must be taken when combining not CEs with or and and CEs; the results are not
always obvious! The same holds true for variable bindings within a not CE
...
However, variables bound for the first time
within a not CE can be used only in that pattern
...
For example, the following
conditional element
(not (test (> ?time-1 ?time-2)))

CLIPS Basic Programming Guide

53

CLIPS Reference Manual

is converted to
(not (and (initial-fact)
(test (> ?time-1 ?time-2))))

Note that it is much simpler just to convert the test CE to the following format:
(test (not (> ?time-1 ?time-2)))

Important Note
Because the not CE can cause the addition of the initial-fact fact pattern or the initial-object
instance pattern to a rule, a reset command (which creates the initial-fact fact and the
initial-object instance) must be issued for the correct operation of the not CE under all
circumstances
...

5
...
6 Exists Conditional Element
The exists conditional element provides a mechanism for determining if a group of specified
CEs is satisfied by a least one set of pattern entities
...
For
example, the following rule
(defrule example
(exists (a ?x) (b ?x))
=>)

is equivalent to the rule below
(defrule example
(not (not (and (a ?x) (b ?x))))
=>)

Because of the way the exists CE is implemented using not CEs, the restrictions which apply to
CEs found within not CEs (such as binding a pattern CE to a fact-address) also apply to the CEs
found within an exists CE
...
" crlf))
CLIPS>

the following commands illustrate that even though there are three facts which can match the
second CE in the save-the-day rule, there is only one partial match generated
...

CLIPS> (facts)
f-0
(initial-fact)
f-1
(goal save-the-day)
f-2
(hero (name Death Defying Man) (status unoccupied))
f-3
(hero (name Stupendous Man) (status unoccupied))
f-4
(hero (name Incredible Man) (status unoccupied))
For a total of 5 facts
...
Because the not CE can cause the addition of
the initial-fact fact pattern or the initial-object instance pattern to a rule, a reset command (which
creates the initial-fact fact and the initial-object instance) must be issued for the correct operation
of the exists CE under all circumstances
...

CLIPS Basic Programming Guide

55

CLIPS Reference Manual

5
...
7 Forall Conditional Element
The forall conditional element provides a mechanism for determining if a group of specified
CEs is satisfied for every occurence of another specified CE
...
For example, the following rule
(defrule example
(forall (a ?x) (b ?x) (c ?x))
=>)

is equivalent to the rule below
(defrule example
(not (and (a ?x)
(not (and (b ?x) (c ?x)))))
=>)

Because of the way the forall CE is implemented using not CEs, the restrictions which apply to
CE found within not CEs (such as binding a pattern CE to a fact-address) also apply to the CEs
found within an forall CE
...

CLIPS> (clear)
CLIPS>
(defrule all-students-passed
(forall (student ?name)
(reading ?name)
(writing ?name)
(arithmetic ?name))
=>
(printout t "All students passed
...
Note
that initially the all-students-passed rule is satisfied because there are no students
...

CLIPS>
56

Section 5 - Defrule Construct

CLIPS Reference Manual

After the (student Bob) fact is asserted, the rule is no longer satisfied since Bob has not passed
reading, writing, and arithmetic
...

CLIPS> (assert (reading Bob) (writing Bob))

CLIPS> (agenda)
CLIPS>

Once Bob has passed arithmetic, the all-students-passed rule is reactivated
...

CLIPS>

If a new student is asserted, then the rule is taken off the agenda, since John has not passed
reading, writing, and arithmetic
...

CLIPS> (retract 1 5)
CLIPS> (agenda)
0
all-students-passed: f-0,
For a total of 1 activation
...
Because the not CE can cause the addition of
the initial-fact fact pattern or the initial-object instance pattern to a rule, a reset command (which
creates the initial-fact fact and the initial-object instance) must be issued for the correct operation
of the forall CE under all circumstances
...

CLIPS Basic Programming Guide

57

CLIPS Reference Manual

5
...
8 Logical Conditional Element
The logical conditional element provides a truth maintenance capability for pattern entities
(facts or instances) created by rules which use the logical CE
...
The pattern entities matching the LHS logical patterns provide logical support to the facts
and instance created by the RHS of the rule
...
If any one supporting pattern
entities is removed from a group of supporting pattern entities (and there are no other supporting
groups), then the pattern entity is removed
...
g
...
Unconditionally supporting a pattern entity removes all logical support
(without causing the removal of the pattern entity)
...
Removing a rule that generated logical
support for a pattern entity, removes the logical support generated by that rule (but does not
cause the removal of the pattern entity if no logical support remains)
...
It may be used in
conjunction with the and, or, and not CEs
...
For example, the following rule is legal
(defrule ok
(logical (a))
(logical (b))
(c)
=>
(assert (d)))

whereas the following rules are illegal
(defrule not-ok-1
(logical (a))
(b)
(logical (c))
=>
(assert (d)))
(defrule not-ok-2
(a)
(logical (b))
(logical (c))
=>
58

Section 5 - Defrule Construct

CLIPS Reference Manual
(assert (d)))
(defrule not-ok-3
(or (a)
(logical (b)))
(logical (c))
=>
(assert (d)))

Example
Given the following rules,
CLIPS> (clear)
CLIPS>
(defrule rule1
(logical (a))
(logical (b))
(c)
=>
(assert (g) (h)))
CLIPS>
(defrule rule2
(logical (d))
(logical (e))
(f)
=>
(assert (g) (h)))
CLIPS>

the following commands illustrate how logical dependencies work
...
(watch rules)
CLIPS> (assert (a) (b) (c) (d) (e) (f))
==> f-0
(a)
==> f-1
(b)
==> f-2
(c)
==> Activation 0
rule1: f-0,f-1,f-2
==> f-3
(d)
==> f-4
(e)
==> f-5
(f)
==> Activation 0
rule2: f-3,f-3,f-5

CLIPS> (run)
FIRE
1 rule2: f-3,f-4,f-5 ; 1st rule adds logical support
==> f-6
(g)
==> f-7
(h)
FIRE
2 rule1: f-0,f-1,f-2 ; 2nd rule adds further support
CLIPS> (retract 1)
<== f-0
(a)
; Removes 1st support for (g) and (h)
CLIPS> (assert (h))
; (h) is unconditionally supported
FALSE
CLIPS> (retract 3)
<== f-3
(d)
; Removes 2nd support for (g)
CLIPS Basic Programming Guide

59

CLIPS Reference Manual
<== f-6
(g)
CLIPS> (unwatch all)
CLIPS>

; (g) has no more support

As mentioned in section 5
...
1
...
This cannot be accomplished with template facts because a
change to a template fact slot actually involves the retraction of the old template fact and the
assertion of a new one, whereas a change to an instance slot is done in place
...

CLIPS> (run)
==> f-3
(new-fact)
CLIPS> (send [a] put-foo 100)
<== f-3
(new-fact)
100
CLIPS> (agenda)
0
match-A-s: [a],f-2
For a total of 1 activation
...
4
...
There are two default patterns used by
CLIPS: the initial-fact fact pattern and the initial-object instance pattern
...
4
...
1 Rules Without Any LHS Pattern CEs
The initial-fact pattern is added to any rule that has no patterns on its LHS (unless facts have
been disabled by configuring CLIPS in which case the initial-object pattern is added to the LHS
of the rule)
...

(defrule example-1
(initial-fact)
=>)

5
...
9
...
An initial-fact pattern is added if the first
pattern CE preceding the CE in question is a fact pattern
...
If there are no preceding
pattern CEs, the type of pattern is determined by the succeeding pattern CEs using the same
methodology
...
For example, the following rules
(defrule example-2
(test (> 80 (startup-value)))
=>)
(defrule example-3
CLIPS Basic Programming Guide

61

CLIPS Reference Manual
(test (> 80 (startup-value)))
(object (is-a MACHINE))
=>)
(defrule example-4
(machine ?x)
(not (and (not (part ?x ?y))
(inventoried ?x)))
=>)

would be changed as follows
...
4
...
3 Test CEs Following Not CEs
Test CEs that immediately follow a not CE are automatically moved by CLIPS behind the first
pattern CE that precedes the not CE
...

(defrule example
(a ?x)
(test (> ?x 5))
(not (b ?x))
=>)

62

Section 5 - Defrule Construct

CLIPS Reference Manual

5
...
9
...
For example,
the following rule
(defrule example
(a ?x)
(not (or (b ?x)
(c ?x)))
=>)

would be changed as follows
...
4
...
5 Notes About Pattern Addition and Reordering
There are several points which should be noted about the addition and reordering of pattern CEs:
1) The entire LHS of a rule is considered to be within an implicit and CE; 2) The conversion of
the forall and exists CEs to equivalent not and and CEs is performed before patterns are added to
the LHS of a rule; 3) In general, it is not very useful to have a test CE as the first CE within an
and CE; and 4) The output of commands such as the matches command display information for
the CEs that are actually added to the LHS of a rule and, because of reordering and implicit
additions, may not reflect the rule exactly as defined by the user
...

5
...
10 Declaring Rule Properties
This feature allows the properties or characteristics of a rule to be defined
...
A rule may only have one declare
statement and it must appear before the first conditional element on the LHS (as shown in section
5
...

Syntax
::= (declare +)

CLIPS Basic Programming Guide

63

CLIPS Reference Manual
::= (salience ) |
(auto-focus )
::= TRUE | FALSE

5
...
10
...
When multiple rules are
in the agenda, the rule with the highest priority will fire first
...
Salience
expressions may freely reference global variables and other functions (however, you should
avoid using functions with side-effects)
...

Example

(defrule test-1
(declare (salience 99))
(fire test-1)
=>
(printout t "Rule test-1 firing
...
" crlf))

Salience values can be evaluated at one of three times: when a rule is defined, when a rule is
activated, and every cycle of execution (the latter two situations are referred to as dynamic
salience)
...
The
set-salience-evaluation command can be used to change this behavior
...
e
...

Usage Note
Despite the large number of possible values, with good design there’s rarely a need for more than
five salience values in a simple program and ten salience values in a complex program
...
4
...
2 The Auto-Focus Rule Property
The auto-focus rule property allows an automatic focus command to be executed whenever a
rule becomes activated
...

If the auto-focus property for a rule is FALSE, then no action is taken when the rule is activated
...

Example
(defrule VIOLATIONS::bad-age
(declare (auto-focus TRUE))
(person (name ?name) (age ?x&:(< ?x 0)))
=>
(printout t ?name " has a bad age value
...
Global variables can be accessed as part of the pattern-matching process,
but changing them does not invoke the pattern-matching process
...
Global variables are reset to their original value when the reset
command is performed or when bind is called for the global with no values
...
Global variables can be removed by using the
clear command or the undefglobal command
...
2), then an informational message will be displayed each time the value of a global variable is
changed
...
The optional indicates the module in which the
defglobals will be defined
...

If a variable was defined in a previous defglobal construct, its value will be replaced by the value
found in the new defglobal construct
...

Commands that operate on defglobals such as ppdefglobal and undefglobal expect the symbolic
name of the global without the astericks (e
...
use the symbol max when you want to refer to the
global variable ?*max*)
...

Global variables may not be used as a parameter variable for a deffunction, defmethod, or
message-handler
...
Therefore, the following rule is illegal
(defrule example
(fact ?*x*)
=>)

The following rule, however, is legal
...
For
example, if ?*x* is 4 and the fact (fact 3) is added, then the rule is not satisfied
...

Example

(defglobal
?*x* = 3
?*y* = ?*x*
?*z* = (+ ?*x* ?*y*)
?*q* = (create$ a b c))

Usage Note
The inappropriate use of globals within rules is quite often the first resort of beginning
programmers who have reached an impasse in developing a program because they do not fully
understand how rules and pattern-matching work
...

Facts and instances are the primary mechanism that should be used to pass information from one
rule to another specifically because they do invoke pattern-matching
...
Since a change to a global variable does not trigger pattern-matching, it is
possible for a rule to remain activated based on a past value of a global variable which is
undesirable in most situations
...
Just as a rule can access any global variable that’s visible (i
...
it hasn’t been hidden
through the use of modules), so too can it access any fact or instance belonging to a deftemplate
or defclass that’s visible
...
In the case of an
instance, pattern-matching and instance-set query functions can also be used, and in addition an
instance can be directly referenced by name just as a global variable can
...
First attempts at rules to accomplish this task often loop
endlessly because of rules inadvertently retriggered by changes
...
A non-destructive approach makes use of temporary facts created by a helper rule:
(defrule add-factoid-helper
(factoid ?data)
=>
(assert (temp-factoid ?data)))
(defrule add-factoid
?f <- (temp-factoid ?data)
?c <- (collection $?collection)
=>
(retract ?f ?c)
(assert (collection ?collection ?data)))

It certainly looks simpler, however, to use a global variable to collect the slot values:
(defglobal ?*collection* = (create$))
(defrule add-factoid
(factoid ?data)
=>
(bind ?*collection* (create$ ?*collection* ?data)))

Again, the drawback to this approach is that changes to a global variable do not trigger
pattern-matching, so in spite of its greater complexity the fact-based approach is still preferable
...
If there are 1000 factoid facts, the add-factoid/add-factoid-helper rules will
each fire 1000 times generating and retracting 2000 facts
...
Typically if other rules are
waiting for the finished result of the collection, they would need to have lower salience so that
they aren’t fired for the intermediate results:
(defrule print-factoids
(declare (salience -10))
(collection $?data)
=>
(printout t "The collected data is " ?data crlf))

If the factoid facts are collected by a single rule firing, then the salience declaration is
unnecessary
...
It is a rare situation where a global variable is required in order to solve a problem
...
In
the following rule, a global variable is used to determine whether additional debugging
information is printed:
(defglobal ?*debug-print* = nil)
(defrule rule-debug
?f <- (info ?info)
=>
(retract ?f)
(printout ?*debug-print* "Retracting info " ?info crlf))

If ?*debug-print* is set to nil, then the printout statement will not display any information
...
Because
?*debug-print* is a global, it can be changed interactively without causing rules to be
reactivated
...

It’s possible, but a little more verbose, to achieve this same functionality using instances rather
than global variables:
(defclass DEBUG-INFO
(is-a USER)
(slot debug-print))
(definstances debug
([debug-info] of DEBUG-INFO (debug-print nil)))
(defrule rule-debug
?f <- (info ?info)
=>
(retract ?f)
(printout (send [debug-info] get-debug-print) "Retracting info " ?info crlf))

Unlike fact slots, changes to a slot of an instance won’t trigger pattern matching in a rule unless
the slot is specified on the LHS of that rule, thus you have explicit control over whether an
instance slot triggers pattern-matching
...

CLIPS Basic Programming Guide

71

CLIPS Reference Manual

Section 7 - Deffunction Construct
With the deffunction construct, new functions may be defined directly in CLIPS
...
3
...
The only differences between user-defined external functions and deffunctions are that
deffunctions are written in CLIPS and executed by CLIPS interpretively and user-defined
external functions are written in an external language, such as C, and executed by CLIPS
directly
...

A deffunction is comprised of five elements: 1) a name, 2) an optional comment, 3) a list of zero
or more required parameters, 4) an optional wildcard parameter to handle a variable number of
arguments and 5) a sequence of actions, or expressions, which will be executed in order when the
deffunction is called
...
In particular, a deffunction cannot be overloaded like a system function (see section 8
for more detail)
...
The only exception is a
self recursive deffunction
...
The regular parameters specify the minimum
number of arguments that must be passed to the deffunction
...
If a wildcard
parameter is present, the deffunction may be passed any number of arguments greater than or
equal to the minimum
...
All arguments to a
deffunction that do not correspond to a regular parameter are grouped into a multifield value that
can be referenced by the wildcard parameter
...

Example
CLIPS> (clear)
CLIPS>
(deffunction print-args (?a ?b $?c)
(printout t ?a " " ?b " and " (length ?c) " extras: " ?c
crlf))
CLIPS Basic Programming Guide

73

CLIPS Reference Manual
CLIPS> (print-args 1 2)
1 2 and 0 extras: ()
CLIPS> (print-args a b c d)
a b and 2 extras: (c d)
CLIPS>

When a deffunction is called, its actions are executed in order
...
If a deffunction has no actions, its return value is the symbol
FALSE
...

Deffunctions may be self and mutually recursive
...

Example
(deffunction factorial (?a)
(if (or (not (integerp ?a)) (< ?a 0)) then
(printout t "Factorial Error!" crlf)
else
(if (= ?a 0) then
1
else
(* ?a (factorial (- ?a 1))))))

Mutual recursion between two deffunctions requires a forward declaration of one of the
deffunctions
...
In the following example, the deffunction foo is forward declared so that it may be
called by the deffunction bar
...

Example

(deffunction foo ())
(deffunction bar ()
(foo))
(deffunction foo ()
(bar))

Care should be taken with recursive deffunctions; too many levels of recursion can lead to an
overflow of stack memory (especially on PC-type machines)
...
Generic functions are similar to deffunctions because they can be used to define new
procedural code directly in CLIPS, and they can be called like any other function (see sections
2
...
2 and 7)
...
For example, a “+”
operator could be defined which performs concatenation for strings but still performs arithmetic
addition for numbers
...
A generic
function which has more than one method is said to be overloaded
...
For example, an overloading of the “+” operator to handle strings consists of two
methods: 1) an implicit one which is the system function handling numerical addition, and 2) an
explicit (user-defined) one handling string concatenation
...

Deffunctions are only provided so that basic new functions can be added directly in CLIPS
without the concerns of overloading
...

In most cases, generic function methods are not called directly (the function
call-specific-method described in section 12
...
8 can be used to do so, however)
...
This process is termed the generic dispatch
...
1 NOTE ON THE USE OF THE TERM METHOD
Most OOP systems support procedural behavior of objects either through message-passing (e
...

Smalltalk) or by generic functions (e
...
CLOS)
...
A generic function may examine the
classes of its arguments but must still use messages within the bodies of its methods to
manipulate any arguments which are instances of user-defined classes
...
The fact that CLIPS supports both mechanisms leads to a confusion in
terminology
...
In systems which
support generic functions only, however, the term method is used to denote the different
implementations of a generic function for different sets of argument restrictions
...
Thus in CLIPS, message-handlers denote the different implementations of a message
for different classes, and methods denote the different implementations of a generic function
for different sets of argument restrictions
...
2 PERFORMANCE PENALTY OF GENERIC FUNCTIONS
A call to a generic function is computationally more expensive than a call to a system function,
user-defined external function or deffunction
...
A performance penalty of
15%-20% is not unexpected
...
Also,
generic functions should always have at least two methods
...
A system or user-defined external
function which is not overloaded will, of course, execute as quickly as ever, since the generic
dispatch is unnecessary
...
3 ORDER DEPENDENCE OF GENERIC FUNCTION DEFINITIONS
If a construct which uses a system or user-defined external function is loaded before a generic
function which uses that function as an implicit method, all calls to that function from that
construct will bypass the generic dispatch
...
However, similar rules defined after the generic function will use
the generic dispatch
...
4 DEFINING A NEW GENERIC FUNCTION
A generic function is comprised of a header (similar to a forward declaration) and zero or more
methods
...
A method is comprised of six elements: 1) a
name (which identifies to which generic function the method belongs), 2) an optional index, 3)
an optional comment , 4) a set of parameter restrictions, 5) an optional wildcard parameter
restriction to handle a variable number of arguments and 6) a sequence of actions, or
expressions, which will be executed in order when the method is called
...
The defgeneric construct is used to
specify the generic function header, and the defmethod construct is used for each of the generic
function’s methods
...
The
only exception is a self recursive generic function
...
4
...
In order to reference a generic function in
other constructs before any of its methods are declared, an explicit header is necessary
...
For example, two
generic functions whose methods mutually call the other generic function (mutually recursive
generic functions) would require explicit headers
...
4
...
Each
method for a generic function is assigned a unique integer index within the group of all methods
for that generic function
...

However, any difference in parameter restrictions will cause the new method to be defined in
addition to the older method
...

However, the parameter restrictions of the new method must not match that of another method
with a different index
...
The index assigned by CLIPS can
be determined with the list-defmethods command (see section 13
...
4)
...
4
...
A parameter restriction is applied to a generic function argument at run-time to determine if a
particular method will accept the argument
...
A type restriction constrains the classes of arguments that will be accepted for a
parameter
...
The complexity of parameter restrictions directly affects the speed of
the generic dispatch
...
However, each method of a generic function must have parameter restrictions that make
it distinguishable from all of the other methods so that the generic dispatch can tell which one to
call at run-time
...
5
...

A type restriction allows the user to specify a list of types (or classes), one of which must match
(or be a superclass of) the class of the generic function argument
...
Section 9 describes each of these system
classes
...
Generic functions which use
only the first group of types in their methods will work the same whether COOL is installed or
not
...
5
...

Redundant classes are not allowed in restriction class lists
...

Example

(defmethod foo ((?a INTEGER NUMBER)))

If the type restriction (if any) is satisfied for an argument, then a query restriction (if any) will be
applied
...
CLIPS evaluates
this expression, and if it evaluates to anything but the symbol FALSE, the restriction is
considered satisfied
...
Since parameter restrictions are examined from left to right, queries which
involve multiple parameters should be included with the rightmost parameter
...
For example, the following method
delays evaluation of the query restriction until the classes of both arguments have been verified
...
If all generic function
arguments are accepted by a method’s restrictions, the method itself is deemed applicable to the
set of arguments
...

Method precedence is used for this purpose and will be discussed in section 8
...
2
...
The second call executes the explicit method for
string concatenation, since there are two arguments and they are both strings
...

CLIPS> (clear)
CLIPS>
(defmethod + ((?a STRING) (?b STRING))
(str-cat ?a ?b))
CLIPS> (+ 1 2)
3
CLIPS> (+ "foo" "bar")
"foobar"
CLIPS> (+ "foo" "bar" "woz")
[GENRCEXE1] No applicable methods for +
...
4
...
The regular parameters specify the minimum number of
arguments that must be passed to the method
...
If a wildcard parameter is present,
the method may be passed any number of arguments greater than or equal to the minimum
...
Method arguments which do not correspond to a regular
parameter can be grouped into a multifield value that can be referenced by the wildcard
parameter within the body of the method
...

If multifield values are passed as extra arguments, they will all be merged into one multifield
value referenced by the wildcard parameter
...

Type and query restrictions can be applied to arguments grouped in the wildcard parameter
similarly to regular parameters
...
However, expressions involving the wildcard
parameter variable may be used in the query
...
This variable is only in scope within the query and has no
meaning in the body of the method
...
Thus in the following example, the > and
length$ functions are actually called three times, since there are three arguments:
Example

CLIPS> (defmethod foo (($?any (> (length$ ?any) 2))) yes)
CLIPS> (foo 1 red 3)
yes
CLIPS>

In addition, a query restriction will never be examined if there are no arguments in the wildcard
parameter range
...
In cases like this where the type is irrelevant to
the test, the query restriction can be attached to a regular parameter instead to improve
performance (see section 8
...
1)
...

FALSE
CLIPS>

80

Section 8 - Generic Functions

CLIPS Reference Manual

This approach should not be used if the types of the arguments grouped by the wildcard must be
verified prior to safely evaluating the query restriction
...
5 GENERIC DISPATCH
When a generic function is called, CLIPS selects the method for that generic function with
highest precedence for which parameter restrictions are satisfied by the arguments
...
This entire process is
referred to as the generic dispatch
...

METHOD STEP : Are there any uncalled methods?
YES: Call the next most specific method
...

Else go to DONE
...

NO:

ERROR: There are no applicable methods for this
generic function
...


The solid arrows indicate
automatic control transfer by
the generic dispatch
...


8
...
1 Applicability of Methods Summary
An explicit (user-defined) method is applicable to a generic function call if the following three
conditions are met: 1) its name matches that of the generic function, 2) it accepts at least as
many arguments as were passed to the generic function, and 3) every argument of the generic
function satisfies the corresponding parameter restriction (if any) of the method
...
As soon as one restriction is not satisfied, the
method is abandoned, and the rest of the restrictions (if any) are not examined
...
This implicit method is derived from the
argument restriction string for the external DefineFunction2 call defining that function to CLIPS
(see the Advanced Programming Guide)
...
The specification of this implicit method can be examined with the

CLIPS Basic Programming Guide

81

CLIPS Reference Manual

list-defmethods or get-method-restrictions functions
...
For example,
(+ +)

would yield the following method for the ‘+’ function:
(defmethod + ((?first NUMBER) (?second NUMBER) ($?rest NUMBER))

...

The following system functions cannot be overloaded, and CLIPS will generate an error if an
attempt is made to do so
...
5
...
Method precedence is determined when a
method is defined; the list-defmethods function can be used to examine the precedence of
methods for a generic function (see section 13
...

The precedence between two methods is determined by comparing their parameter restrictions
...

For example, a method which demands an integer for a particular argument will have higher
precedence than a method which only demands a number
...

1) ) The parameter restrictions of both methods are positionally compared from left to right
...
The comparisons between these pairs of
parameter restrictions from the two methods determine the overall precedence between the two
methods
...

The following rules are applied in order to a parameter pair; the result of the first rule which
establishes precedence is taken
...

1b) The most specific type restriction on a particular parameter has priority
...

1c) A parameter with a query restriction has priority over one that does not
...

3) A method without a wildcard parameter has precedence over one that does
4) A method defined before another one has priority
...
Since all precedence determination is done when the new method is defined, and
the actual class of the generic function argument will not be known until run-time, arbitrary (but
deterministic) rules are needed for determining the precedence between two class lists
...
g
...
The first pair containing a class and its
superclass specify precedence
...
If no class pairs
specify precedence, then the shorter class list has priority
...

Example 1

; The system operator '+' is an implicit method
; #1
; Its definition provided by the system is:
; (defmethod + ((?a NUMBER) (?b NUMBER) ($?rest NUMBER)))
(defmethod
(defmethod
(defmethod
(defmethod

+
+
+
+

((?a NUMBER) (?b INTEGER)))
((?a INTEGER) (?b INTEGER)))
((?a INTEGER) (?b NUMBER)))
((?a NUMBER) (?b NUMBER)
($?rest PRIMITIVE)))
(defmethod + ((?a NUMBER)
(?b INTEGER (> ?b 2))))
(defmethod + ((?a INTEGER (> ?a 2))
(?b INTEGER (> ?b 3))))

CLIPS Basic Programming Guide

; #2
; #3
; #4
; #5
; #6
; #7

83

CLIPS Reference Manual
(defmethod + ((?a INTEGER (> ?a 2))
(?b NUMBER)))

; #8

The precedence would be: #7,#8,#3,#4,#6,#2,#1,#5
...
Group A has precedence over group B because
parameters with query restrictions have priority over those that do not
...
Thus, the ordering so far is:
(#7,#8),(#3,#4),(#1,#2,#5,#6)
...

The next step in determining precedence between these methods considers their restrictions on
the second parameter
...
#3
has priority over #4 because INTEGER is a subclass of NUMBER
...
#6 has priority over #2 because it has a
query restriction and #2 does not
...

The restriction on the wildcard argument yields that #1 (the system function implicit method) has
priority over #5 since NUMBER is a sublclass of PRIMITIVE
...

Example 2
(defmethod foo ((?a NUMBER STRING)))
(defmethod foo ((?a INTEGER LEXEME)))

; #1
; #2

The precedence would be #2,#1
...

Example 3

(defmethod foo ((?a MULTIFIELD STRING)))
(defmethod foo ((?a LEXEME)))

; #1
; #2

The precedence would be #2,#1 because the classes of the first pair in the type restriction
(MULTIFIELD/LEXEME) are unrelated and #2 has fewer classes in its class list
...
Thus, the precedence is taken from the order of definition: #1,#2
...
5
...
Normally, only one method or system
function will be applicable to a particular generic function call
...

Letting the generic dispatch automatically handle the methods in this manner is called the
declarative technique, for the declarations of the method restrictions dictate which method gets
executed in specific circumstances
...
15
...
15
...
This is called the imperative technique, since the
method execution itself plays a role in the generic dispatch
...
In most circumstances, only one piece of code should need to be executed
for a particular set of arguments
...
15
...
5
...
The lack of any applicable methods for a set
of generic function arguments is considered a method execution error
...
5
...
Each applicable method that is executed can choose to ignore or capture the
return value of any method that it is shadowing
...


CLIPS Basic Programming Guide

85

CLIPS Reference Manual

Section 9 - CLIPS Object Oriented Language (COOL)
This section provides the comprehensive details of the CLIPS Object-Oriented Language
(COOL)
...
3
...
4
...
5
...
3 explain object references and structure
...
6
gives a high level overview of COOL
...

9
...
For
example, object encapsulation concepts are similar to those in Smalltalk, and the Common Lisp
Object System (CLOS) provides the basis for multiple inheritance rules
...
Section 8
...

9
...
The user may not delete or modify any of these classes
...

OBJECT
USER
PRIMITIVE

NUMBER

INTEGER

INSTANCE

INITIAL-OBJECT

ADDRESS

MULTIFIELD

FLOAT

INSTANCE-NAME

LEXEME

SYMBOL

INSTANCE-ADDRESS

FACT-ADDRESS

STRING

EXTERNAL-ADDRESS

All of these system classes except INITIAL-OBJECT are abstract classes, which means that
their only use is for inheritance (direct instances of this class are illegal)
...
However, the
user may explicitly attach message-handlers to all of the system classes except for INSTANCE,
INSTANCE-ADDRESS and INSTANCE-NAME
...
All user-defined classes should (but are not required to)
inherit directly or indirectly from the class USER, since this class has all of the standard system
CLIPS Basic Programming Guide

87

CLIPS Reference Manual

message-handlers, such as initialization and deletion, attached to it
...
4 describes these
system message-handlers
...
However, the three primitive system classes INSTANCE, INSTANCE-ADDRESS and
INSTANCE-NAME are provided strictly for use in methods (particularly in forming implicit
methods for overloaded system functions - see section 8
...
1) and as such cannot have subclasses
or message-handlers attached to them
...
This system class is
concrete and reactive to pattern-matching on the LHS of rules but is in other respects exactly
like the system class USER
...
4
...

9
...
A defclass consists of five elements: 1) a name, 2) a list of superclasses from
which the new class inherits slots and message-handlers, 3) a specifier saying whether or not the
creation of direct instances of the new class is allowed, 4) a specifier saying whether or not
instances of this class can match object patterns on the LHS of rules and 5) a list of slots specific
to the new class
...

Any slots explicitly given in the defclass override those gotten from inheritance
...
3
...
Facets (see section 9
...
3) further describe slots
...

Syntax
Defaults are outlined
...

An error will occur if instances of the class or any of its subclasses exist
...
3
...
Every user-defined class must have at least one
direct superclass, i
...
at least one class must appear in the is-a portion of the defclass
...
COOL examines the direct
superclass list for a new class to establish a linear ordering called the class precedence list
...
The word precedence implies that slots and message-handlers of a class in the list override
CLIPS Basic Programming Guide

89

CLIPS Reference Manual

conflicting definitions of another class found later in the list
...
All class precedence lists will terminate in the system
class OBJECT, and most (if not all) class precedence lists for user-defined classes will terminate
in the system classes USER and OBJECT
...
11
...
4)
...
3
...
1 Multiple Inheritance Rules
COOL uses the inheritance hierarchy of the direct superclasses to determine the class precedence
list for a new class
...

2) A class specifies the precedence between its direct superclasses
...
This heuristic attempts to preserve “family trees”
to the greatest extent possible
...
There are other orderings which would satisfy the
rules (such as child mother father paternal-grandfather maternal-grandmother
paternal-grandmother maternal-grandfather), but COOL chooses the one which keeps the family
trees together as much as possible
...
The class precedence list for A is: A
USER OBJECT
...
The class precedence list for B is: B
USER OBJECT
...
The class precedence list for C is:
C A B USER OBJECT
...
The class precedence list for D is:
D B A USER OBJECT
...
However, C is a subclass of A and cannot succeed A in a
precedence list without violating rule #1
...

Example 6
(defclass E (is-a C A))

Specifying that E inherits from A is extraneous, since C inherits from A
...
The class precedence list for E is: E C A B USER
OBJECT
...
The class precedence
list for F is: F C A B USER OBJECT
...

Example 8

(defclass G (is-a C D))

This is an error, for it violates rule #2
...

Example 9
(defclass H (is-a A))
(defclass I (is-a B))
(defclass J (is-a H I A B))

The respective class precedence lists of H and I are: H A USER OBJECT and I B USER
OBJECT
...
COOL would normally pick the first list since it preserves the family trees (H A and I
B) to the greatest extent possible
...

Usage Note
For most practical applications of multiple inheritance, the order in which the superclasses are
specified should not matter
...

9
...
2 Class Specifiers

9
...
2
...
A concrete class can have direct instances
...
If the
abstract or concrete descriptor for a class is not specified, it is determined by inheritance
...
Thus a class
which inherits from USER will be concrete if no role is specified
...
3
...
2 Reactive and Non-Reactive Classes
Objects of a reactive class can match object patterns in a rule
...
An abstract class cannot be reactive
...
For the
purpose of pattern-match inheritance, system defined classes behave as reactive classes unless
the inheriting class is abstract
...
3
...
Each instance
has a copy of the set of slots specified by the immediate class as well as any obtained from
inheritance
...
The name of a slot may be any
symbol with the exception of the keywords is-a and name which are reserved for use in object
patterns
...
A class is more specific than
its superclasses
...
3
...
5)
...
3
...
6)
...
Instances of A will have two slots: fooA
and barA
...
Instances of B will have four
slots: fooB, barB, fooA and barA
...
Facets describe various features of a slot that
hold true for all objects which have the slot: default value, storage, access, inheritance
propagation, source of other facets, pattern-matching reactivity, visibility to subclass
message-handlers, the automatic creation of message-handlers to access the slot, the name of the
message to send to set the slot and constraint information
...
3
...
3)
...
3
...
1 Slot Field Type
A slot can hold either a single-field or multifield value
...
The
keyword multislot specifies that a slot can hold a multifield value comprised of zero or more
fields, and the keywords slot or single-slot specify that the slot can hold one value
...
COOL also provides
functions for setting multifield slots, such as slot-insert$ (see section 12
...
4
...
2)
...

Example

CLIPS> (clear)
CLIPS>
(defclass A (is-a USER)
(role concrete)
(multislot foo (create-accessor read)
(default abc def ghi)))
CLIPS> (make-instance a of A)
[a]
CLIPS> (nth$ 2 (send [a] get-foo))
def
CLIPS>

9
...
3
...
By default, a slot will have a default value
which is derived from the slot’s constraint facets (see sections 9
...
3
...
5)
...
6
...

The default facet is a static default: the specified expression is evaluated once when the class is
defined, and the result is stored with the class
...
If the keyword ?DERIVE is used for the default value, then a default
value is derived from the constraints for the slot (see section 11
...
By default,
the default attribute for a slot is (default ?DERIVE)
...
Using this keyword causes
make-instance to require a slot-override for that slot when an instance is created
...
0, a slot now has a default even if one is not explicitly specified (unlike CLIPS 5
...

This could cause different behavior for CLIPS 5
...
The ?NONE keyword can be used to recover the original behavior for classes
...

Example
CLIPS> (clear)
CLIPS> (setgen 1)
1
CLIPS>
(defclass A (is-a USER)
(role concrete)
(slot foo (default-dynamic (gensym))
(create-accessor read)))
CLIPS> (make-instance a1 of A)
[a1]
CLIPS> (make-instance a2 of A)
[a2]
CLIPS> (send [a1] get-foo)
gen1
CLIPS> (send [a2] get-foo)
gen2
CLIPS>

9
...
3
...
The local facet specifies that the value be stored with the instance, and this is the default
...
If the slot value is locally
stored, then each instance can have a separate value for the slot
...
Anytime the value is
changed for a shared slot, it will be changed for all instances with that slot
...
Any changes to a shared slot will cause pattern-matching for rules to be
updated for all reactive instances containing that slot
...
3
...
4 Access Facet
There are three types of access facets which can be specified for a slot: read-write, read-only,
and initialize-only
...
The read-only facet says the slot can only be read; the only way to set this slot is with
default facets in the class definition
...
6
...
4)
...
4)
...

Example
CLIPS> (clear)
CLIPS>
(defclass A (is-a USER)
(role concrete)
(slot foo (create-accessor write)
(access read-write))
(slot bar (access read-only)
(default abc))
(slot woz (create-accessor write)
(access initialize-only)))
CLIPS>
(defmessage-handler A put-bar (?value)
(dynamic-put (sym-cat bar) ?value))
CLIPS> (make-instance a of A (bar 34))
[MSGFUN3] bar slot in [a] of A: write access denied
...

[PRCCODE4] Execution halted during the actions of message-handler put-bar primary
in class A
FALSE
CLIPS> (send [a] put-woz 1)
[MSGFUN3] woz slot in [a] of A: write access denied
...
3
...
5 Inheritance Propagation Facet
An inherit facet says that a slot in a class can be given to instances of other classes that inherit
from the first class
...
The no-inherit facet says that only direct instances of this
class will get the slot
...
3
...
6 Source Facet
When obtaining slots from the class precedence list during instance creation, the default behavior
is to take the facets from the most specific class which gives the slot and give default values to
any unspecified facets
...
The composite facet
causes facets which are not explicitly specified by the most specific class to be taken from the
next most specific class
...
Note that even though facets may be taken from superclasses,
the slot is still considered to reside in the new class for purposes of visibility (see section
9
...
3
...
One good example of a use of this feature is to pick up a slot definition and change only
its default value for a new derived class
...

Reactive: direct instances of this class can match defrule patterns
...
+oo] CRD:[0
...
3
...
7 Pattern-Match Reactivity Facet
Normally, any change to a slot of an instance will be considered as a change to the instance for
purposes of pattern-matching
...
The reactive facet specifies that changes to a slot
trigger pattern-matching, and this is the default
...

Example
CLIPS> (clear)
CLIPS>
(defclass A (is-a USER)
(role concrete)
(pattern-match reactive)
(slot foo (create-accessor write)
(pattern-match non-reactive)))
CLIPS>
(defclass B (is-a USER)
(role concrete)
(pattern-match reactive)
(slot foo (create-accessor write)
(pattern-match reactive)))
CLIPS>
(defrule Create
?ins<-(object (is-a A | B))
=>
(printout t "Create " (instance-name ?ins) crlf))
CLIPS>
(defrule Foo-Access
?ins<-(object (is-a A | B) (foo ?))
=>
98

Section 9 - CLIPS Object Oriented Language (COOL)

CLIPS Reference Manual
(printout t "Foo-Access " (instance-name ?ins) crlf))
CLIPS> (make-instance a of A)
[a]
CLIPS> (make-instance b of B)
[b]
CLIPS> (run)
Create [b]
Foo-Access [b]
Create [a]
CLIPS> (send [a] put-foo 1)
1
CLIPS> (send [b] put-foo 1)
1
CLIPS> (run)
Foo-Access [b]
CLIPS>

9
...
3
...
However, it is possible to allow message-handlers attached to superclasses or
subclasses which inherit the slot to directly access the slot as well
...
Declaring the visibility facet to be public specifies that the
message-handlers and subclasses which inherit the slot and superclasses may also directly access
the slot
...

ERROR:
(defmessage-handler MAIN::B get-foo
()
?self:foo
)
CLIPS>

CLIPS Basic Programming Guide

99

CLIPS Reference Manual

9
...
3
...
By default, implicit slot-accessor message-handlers are created for
every slot
...

If the value ?NONE is specified for the facet, no message-handlers are created
...

If accessors are required that do not use static slot references (see sections 9
...
2, 9
...
3 and 9
...
4),
then user must define them explicitly with the defmessage-handler construct
...
If the access facet is
read-write, then the default value for the create-accessor facet is read-write
...
If the access facet is initialize-only, then the default
is ?NONE
...


100

Section 9 - CLIPS Object Oriented Language (COOL)

CLIPS Reference Manual
FALSE
CLIPS>

9
...
3
...
g
...
By default, all these functions attempt to set a slot with the
message called put-
...

Example
CLIPS> (clear)
CLIPS>
(defclass A (is-a USER)
(role concrete)
(slot special (override-message special-put)))
CLIPS>
(defmessage-handler A special-put primary (?value)
(bind ?self:special ?value))
CLIPS> (watch messages)
CLIPS> (make-instance a of A (special 65))
MSG >> create ED:1 ()
MSG << create ED:1 ()
MSG >> special-put ED:1 ( 65)
MSG << special-put ED:1 ( 65)
MSG >> init ED:1 ()
MSG << init ED:1 ()
[a]
CLIPS> (unwatch messages)
CLIPS>

9
...
3
...
Static and dynamic constraint checking for classes and their instances is
supported
...
Object patterns used on the LHS of a rule are also checked to
determine if constraint conflicts exist among variables used in more that one slot
...
Static checking is enabled by default
...
Dynamic checking
is also supported
...
g
...
This dynamic checking
is
disabled
by
default
...
If an violation occurs when dynamic checking is
being performed, then execution will be halted
...
Single-field values are converted to a multifield value of length one
when storing in a multifield slot
...

Example

CLIPS> (clear)
CLIPS>
(defclass A (is-a USER)
(role concrete)
(multislot foo (create-accessor write)
(type SYMBOL)
(cardinality 2 3)))
CLIPS> (make-instance a of A (foo 45))
[a]
CLIPS> (set-dynamic-constraint-checking TRUE)
FALSE
CLIPS> (make-instance a of A (foo red 5
...
0) for slot foo of instance
class A does not match the allowed types
...

[PRCCODE4] Execution halted during the actions
in class A
FALSE
CLIPS>

[a] found in put-foo primary in
of message-handler put-foo primary

found in put-foo primary in class A
of message-handler put-foo primary

9
...
4 Message-handler Documentation
COOL allows the user to forward declare the message-handlers for a class within the defclass
statement
...
The
defmessage-handler construct must be used to actually add message-handlers to a class
...

Example

CLIPS> (clear)
CLIPS>
(defclass rectangle (is-a USER)
(slot side-a (default 1))
(slot side-b (default 1))
(message-handler find-area))
CLIPS>
(defmessage-handler rectangle find-area ()
(* ?self:side-a ?self:side-b))
CLIPS>
(defmessage-handler rectangle print-area ()
(printout t (send ?self find-area) crlf))

102

Section 9 - CLIPS Object Oriented Language (COOL)

CLIPS Reference Manual
CLIPS>

9
...
The result of a
message is a useful return-value or side-effect
...
The
implementation of a message is made up of pieces of procedural code called message-handlers
(or handlers for short)
...
In this way, the object’s class and all its superclasses share the labor of
handling the message
...
Within a class, the handlers for a particular message can be further subdivided into
four types or categories: primary, before, after and around
...
Before
handlers execute before the primary ones, and after message-handlers execute after the primary
ones
...
Around message-handlers allow the user to wrap code
around the rest of the handlers
...

A primary handler provides the part of the message implementation which is most specific to an
object, and thus the primary handler attached to the class closest to the immediate class of the
object overrides other primary handlers
...
When
only the roles of the handlers specify which handlers get executed and in what order, the
message is said to be declaratively implemented
...
For example, the results of more than one primary handler may be
needed
...
This is called the imperative technique
...
Around
handlers can change the environment in which other handlers execute and modify the return
value for the entire message
...

CLIPS Basic Programming Guide

103

CLIPS Reference Manual

A defmessage-handler is comprised of seven elements: 1) a class name to which to attach the
handler (the class must have been previously defined), 2) a message name to which the handler
will respond, 3) an optional type (the default is primary), 4) an optional comment, 5) a list of
parameters that will be passed to the handler during execution, 6) an optional wildcard parameter
and 7) a series of expressions which are executed in order when the handler is called
...

Syntax
Defaults are outlined
...
Message-handlers are never
called directly
...
This
process is termed the message dispatch
...
" crlf))
CLIPS>
(defmessage-handler USER delete after ()
(printout t "System completed deletion of an instance
...

<== instance [a] of A
System completed deletion of an instance
...
4
...
The regular parameters specify the minimum
number of arguments that must be passed to the handler
...
If a wildcard
parameter is present, the handler may be passed any number of arguments greater than or equal
to the minimum
...
All arguments to a handler that do not
correspond to a regular parameter are grouped into a multifield value that can be referenced by
the wildcard parameter
...

Handler parameters have no bearing on the applicability of a handler to a particular message (see
section 9
...
1)
...
5
...
Thus, the number of arguments
accepted should be consistent for all message-handlers applicable to a particular message
...
4
...
1 Active Instance Parameter
The term active instance refers to an instance which is responding to a message
...
This parameter name is reserved and cannot be explicitly listed in the
message-handler’s parameters, nor can it be rebound within the body of a message-handler
...
4
...
The return value of the message-handler is the result of the evaluation of the
last expression in the body
...
Normally, slots can only be
manipulated by sending the object slot-accessor messages (see sections 9
...
3
...
4
...

However, handlers are considered part of the encapsulation (see section 2
...
2) of an object, and
thus can directly view and change the slots of the object
...
These functions are discussed in section 12
...

A shorthand notation is provided for accessing slots of the active instance from within a
message-handler
...

Syntax

(bind ?self: *)

Example
CLIPS>
(defmessage-handler A set-foo (?value)
(bind ?self:foo ?value))
CLIPS> (send [a] set-foo 34)
34
CLIPS>

Direct slot accesses are statically bound to the appropriate slot in the defclass when the
message-handler is defined
...
If the subclass has redefined the slot, the direct slot access
contained in the message-handler attached to the superclass will fail
...

Example
CLIPS> (clear)
CLIPS>
(defclass A (is-a USER)
(slot foo (create-accessor read)))
CLIPS>
(defclass B (is-a A)
(role concrete)
(slot foo))
CLIPS> (make-instance b of B)
[b]
CLIPS> (send [b] get-foo)
[MSGPASS3] Static reference to slot foo of class A does not apply to [b] of B
[PRCCODE4] Execution halted during the actions of message-handler get-foo primary
in class A
FALSE
CLIPS>

In order for direct slot accesses in a superclass message-handler to apply to new versions of the
slot in subclasses, the dynamic-put and dynamic-get (see sections 12
...
4
...
16
...
11)
must be used
...
3
...
8)
...
4
...
All these basic actions
are implemented with primary handlers attached to the class of the instance
...
These pieces of code will then be executed whenever the
basic actions are performed on the instance
...
"
crlf))
CLIPS> (make-instance a of A)
Initializing a new instance of class A
...
4
...
These
handlers cannot be deleted or modified
...
4
...
1 Instance Initialization
Syntax

(defmessage-handler USER init primary ())

This handler is responsible for initializing instances with class default values after creation
...
6
...
6
...
This handler is
implemented using the init-slots function (see section 12
...
User-defined init handlers should
not prevent the system message-handler from responding to an init message (see section 9
...
3)
...
4
...
2 Instance Deletion
Syntax
(defmessage-handler USER delete primary ())

This handler is responsible for deleting an instance from the system
...
User-defined delete message-handlers should not prevent the
system message-handler from responding to a delete message (see section 9
...
3)
...

Example

CLIPS> (send [Rolls-Royce] delete)
MSG >> delete ED:1 ()
HND >> delete primary in class USER
ED:1 ()
HND << delete primary in class USER
ED:1 ()
MSG << delete ED:1 ()
TRUE
CLIPS>

CLIPS Basic Programming Guide

109

CLIPS Reference Manual

9
...
4
...

Example
CLIPS> (make-instance Rolls-Royce of CAR)
MSG >> create ED:1 ()
HND >> create primary in class USER
ED:1 ()
HND << create primary in class USER
ED:1 ()
MSG << create ED:1 ()
MSG >> init ED:1 ()
HND >> init primary in class USER
ED:1 ()
HND << init primary in class USER
ED:1 ()
MSG << init ED:1 ()
[Rolls-Royce]
CLIPS> (send [Rolls-Royce] print)
MSG >> print ED:1 ()
HND >> print primary in class USER
ED:1 ()
[Rolls-Royce] of CAR
(price 75000)
(model Corniche)
HND << print primary in class USER
ED:1 ()
MSG << print ED:1 ()
CLIPS> (unwatch messages)
CLIPS
...
4
...
4 Directly Modifying an Instance
Syntax
(defmessage-handler USER direct-modify primary
(?slot-override-expressions))

This handler modifies the slots of an instance directly rather than using put- override messages to
place the slot values
...
This message is used by the functions modify-instance
and active-modify-instance
...

(defmessage-handler USER direct-modify around
(?overrides)
(send ?self message-modify ?overrides))

9
...
4
...
The
slot-override expressions are passed as an EXTERNAL_ADDRESS data object to the
message-modify handler
...

9
...
4
...
Slot
values from the original instance and slot overrides are directly copied
...
The slot-override expressions are passed as an
EXTERNAL_ADDRESS data object to the direct-duplicate handler
...

Example
The following around message-handler could be used to insure that all duplicate message
slot-overrides are handled using put- messages
...
4
...
7 Duplicating an Instance using Messages
Syntax

(defmessage-handler USER message-duplicate primary
(?new-instance-name ?slot-override-expressions)

This handler duplicates an instance using messages
...
If the name of the new instance created
matches a currently existing instance-name, then the currently existing instance is deleted using a
delete message
...
The slot-override expressions are passed as an EXTERNAL_ADDRESS data object to
the message-duplicate handler
...

9
...
4
...

The newly created instance is sent a create message
...
The
handler returns the symbol TRUE if the instance was successfully created, otherwise it returns
the symbol FALSE
...
5 MESSAGE DISPATCH
When a message is sent to an object using the send function, CLIPS examines the class
precedence list of the active instance’s class to determine a complete set of message-handlers
which are applicable to the message
...
A handler
which is attached to a subclass of another message-handler’s class is said to be more specific
...
Following is a flow diagram
summary:

112

Section 9 - CLIPS Object Oriented Language (COOL)

CLIPS Reference Manual

START : Input is a list of applicable message-handlers
AROUND STEP: Are there any uncalled around handlers?
YES: Call most specific uncalled around handler
...

Else go to DONE
...

NO:
BEFORE STEP: Are there any uncalled before handlers?
YES: Call most specific uncalled before handler
...

NO:
PRIMARY STEP: Are there any uncalled primary handlers?
YES: Call most specific uncalled primary handler
...

NO:

The solid arrows indicate
automatic control transfer by
the message dispatch system
...


AFTER STEP: Are there any uncalled after handlers?
YES: Call least specific uncalled after handler
...

NO:
DONE: Return control and values to caller
...
5
...

9
...
2 Message-handler Precedence
The set of all applicable message-handlers are sorted into four groups according to role, and
these four groups are further sorted by class specificity
...

The order of execution is as follows: 1) around handlers begin execution from most specific to
most general (each around handler must explicitly allow execution of other handlers), 2) before
handlers execute (one after the other) from most specific to most general 3) primary handlers
begin execution from most specific to most general (more specific primary handlers must
explicitly allow execution of more general ones), 4) primary handlers finish execution from most
general to most specific, 5) after handlers execute (one after the other) from most general to most
specific and 6) around handlers finish execution from most general to most specific
...
5
...

9
...
3 Shadowed Message-handlers
When one handler must be called by another handler in order to be executed, the first handler is
said to be shadowed by the second
...
A primary handler shadows all more general primary handlers
...
Only the handler
roles will dictate which handlers get executed; only before and after handlers and the most
specific primary handler are used
...
However, if around handlers or shadowed primary
handlers are necessary, then the handlers must explicitly take part in the message dispatch by
calling other handlers they are shadowing
...
The functions
call-next-handler and override-next-handler (see section 12
...
2) allow a handler to execute
the handler it is shadowing
...

Example

(defmessage-handler USER my-message around ()
(call-next-handler))
(defmessage-handler USER my-message before ())
(defmessage-handler USER my-message ()
(call-next-handler))
(defmessage-handler USER my-message after ())
(defmessage-handler OBJECT my-message around ()
(call-next-handler))
(defmessage-handler OBJECT my-message before ())
(defmessage-handler OBJECT my-message ())
(defmessage-handler OBJECT my-message after ())

For a message sent to an instance of a class which inherits from USER,
the diagram to the right illustrates the order of execution for the handlers
attached to the classes USER and OBJECT
...
Handlers enclosed within
a bracket are shadowed
...
5
...


114

Section 9 - CLIPS Object Oriented Language (COOL)

CLIPS Reference Manual

A lack of applicable of primary message-handlers and a handler being called with the wrong
number of arguments are common message execution errors
...
5
...
The return value of
a handler is the result of the evaluation of the last action in the handler
...
An
around handler can choose to ignore or capture the return value of the next most specific around
or primary handler
...

9
...
This is achieved by using the send function,
which takes as arguments the destination object for the message, the message itself and any
arguments which are to be passed to handlers
...
4
...
The return value of send is the result of the message as
explained in section 9
...
5
...
This is how COOL implements
the notion of encapsulation (see Section 2
...
2)
...
There are two major exceptions:
1) objects which are not instances of user-defined classes (floating-point and integer numbers,
symbols, strings, multifield values, fact-addresses and external-addresses) can be manipulated in
the standard non-OOP manner of previous versions of CLIPS as well and 2) creation and
initialization of an instance of a user-defined class are performed via the function
make-instance
...
6
...
Likewise, all
instances are deleted during the reset command, and they can be loaded and saved similarly to
facts
...
A function called make-instance is used to
CLIPS Basic Programming Guide

115

CLIPS Reference Manual

create and initialize a new instance
...
The user can customize instance
initialization with daemons
...
make-instance automatically delays all object
pattern-matching activities for rules until all slot overrides have been processed
...

active-make-instance remembers the current state of delayed pattern-matching, explicitly turns
delay on, and then restores it to its previous state once all slot overrides have been processed
...
The evaluation of can either be an
instance-name or a symbol
...

make-instance performs the following steps in order:
1) If an instance of the specified name already exists, that instance receives a delete message,
e
...
(send delete)
...
Normally, the handler attached to class USER will respond to this message (see section
9
...
5
...

2) A new and uninitialized instance of the specified class is created with the specified name
...
g
...
Normally,
the handler attached to class USER will respond to this message (see section 9
...
4
...

4) All slot-overrides are immediately evaluated and placed via put- messages (see section
9
...
3
...
g
...
If there are any errors,
the new instance is deleted
...
g
...
Normally, the
handler attached to class USER will respond to this message (see section 9
...
4
...
This handler
calls the init-slots function (see section 12
...
4
...
This function uses defaults from the class
definition (if any) for any slots which do not have slot-overrides
...
If there are any errors, the new instance is deleted
...
" crlf))
CLIPS>
(defmessage-handler A delete after ()
(printout t "Old instance deleted
...

Slot x set with message
...

TRUE
CLIPS>

9
...
1
...
On every reset all current instances receive a
delete message, and the equivalent of a make-instance function call is made for every instance
specified in definstances constructs
...
The instances of a
definstances are created in order, and if any individual creation fails, the remainder of the
definstances will be aborted
...
However, if this is not desired,then the
active keyword can be specified after the definstances name so that the active-make-instance
function will be used
...

(definstances initial-object
(initial-object of INITIAL-OBJECT))

The class INITIAL-OBJECT is a predefined system class that is a direct subclass of USER
...
The
INITIAL-OBJECT class cannot be deleted, but the initial-object definstances can
...
4
...

Important Note
Although you can delete the initial-object definstances, in practice you never should since many
conditional elements rely on the existence of the initial-object instance for correct operation
...

9
...
2 Reinitializing Existing Instances
The initialize-instance function provides the ability to reinitialize an existing instance with class
defaults and new slot-overrides
...
The evaluation of
can either be an instance-name, instance-address or a symbol
...
The function active-initialize-instance can be used if
delayed pattern-matching is not desired
...
3
...
10), e
...
(send put- *)
...
g
...
Normally, the
handler attached to class USER will respond to this message (see section 9
...
5
...
This handler
calls the init-slots function (see section 12
...
4
...
This function uses defaults from the class
definition (if any) for any slots which do not have slot-overrides
...

If no slot-override or class default specifies the value of a slot, that value will remain the same
...

If an error occurs, the instance will not be deleted, but the slot values may be in an inconsistent
state
...
")
“Hello world
...
")
CLIPS> (initialize-instance a)
[a]
CLIPS> (send [a] print)
a of A
(x 34)
(y abc)
(z nil)
CLIPS>

9
...
3 Reading Slots
Sources external to an object, such as a rule or deffunction, can read an object’s slots only by
sending the object a message
...
4
...
Several functions also
exist which operate implicitly on the active instance for a message that can only be called by
message-handlers, such as dynamic-get (see section 12
...
4
...

Section 12
...

Example

CLIPS> (clear)
CLIPS>
(defclass A (is-a USER)
(role concrete)
(slot x (create-accessor read)
(default abc)))
CLIPS> (make-instance a of A)
[a]
CLIPS> (sym-cat (send [a] get-x) def)
abcdef
CLIPS>

9
...
4 Setting Slots
Sources external to an object, such as a rule or deffunction, can write an object’s slots only by
sending the object a message
...
16
...
11)
...
4
...

Example

CLIPS> (clear)
CLIPS>
(defclass A (is-a USER)
(role concrete)

120

Section 9 - CLIPS Object Oriented Language (COOL)

CLIPS Reference Manual
(slot x (create-accessor write)
(default abc)))
CLIPS> (make-instance a of A)
[a]
CLIPS> (send [a] put-x "New value
...
”
CLIPS>

9
...
5 Deleting Instances
Sending the delete message to an instance removes it from the system
...
16) can be used to delete the
active instance for a message
...
6
...
This can
be accomplished using the object-pattern-match-delay function
...
This function’s primary purpose is to provide some
control over performance
...

CLIPS> (make-instance b of A)
[b]
CLIPS> (agenda)
0
match-A: [b]
0
match-A: [a]
For a total of 2 activations
...
" crlf)
(agenda)
(make-instance d of A)
(printout t "After d
...

0
match-A: [b]
0
match-A: [a]
For a total of 2 activations
...

0
match-A: [b]
0
match-A: [a]
For a total of 2 activations
...

CLIPS>

9
...
7 Modifying Instances
Four functions are provided for modifying instances
...
Each of these functions
returns the symbol TRUE if successful, otherwise the symbol FALSE is returned
...
6
...
1 Directly Modifying an Instance with Delayed Pattern-Matching
The modify-instance function uses the direct-modify message to change the values of the
instance
...

Syntax
(modify-instance *)

Example

CLIPS> (clear)
CLIPS>
(defclass A (is-a USER)
(role concrete)
(slot foo)
(slot bar))
CLIPS> (make-instance a of A)
[a]
CLIPS> (watch all)
CLIPS> (modify-instance a (foo 0))
MSG >> direct-modify ED:1 ( )

122

Section 9 - CLIPS Object Oriented Language (COOL)

CLIPS Reference Manual
HND >> direct-modify primary in class USER
...

ED:1 ( )
MSG << direct-modify ED:1 ( )
TRUE
CLIPS> (unwatch all)
CLIPS>

9
...
7
...
Object pattern-matching occurs as slot modifications are being performed
...
6
...
3 Modifying an Instance using Messages with Delayed Pattern-Matching
The message-modify-instance function uses the message-modify message to change the values
of the instance
...

Syntax

(message-modify-instance *)

Example
CLIPS> (clear)
CLIPS>
(defclass A (is-a USER)
(role concrete)
(slot foo)
(slot bar (create-accessor write)))
CLIPS> (make-instance a of A)
[a]
CLIPS> (watch all)
CLIPS> (message-modify-instance a (bar 4))
MSG >> message-modify ED:1 ( )
HND >> message-modify primary in class USER
ED:1 ( )
MSG >> put-bar ED:2 ( 4)
HND >> put-bar primary in class A
ED:2 ( 4)
::= local slot bar in instance a <- 4
HND << put-bar primary in class A
ED:2 ( 4)
MSG << put-bar ED:2 ( 4)
HND << message-modify primary in class USER
ED:1 ( )
MSG << message-modify ED:1 ( )
CLIPS Basic Programming Guide

123

CLIPS Reference Manual
TRUE
CLIPS> (unwatch all)
CLIPS>

9
...
7
...
Object pattern-matching occurs as slot modifications are being performed
...
6
...
These functions allow instance duplication
and slot updates to be performed in blocks without requiring a series of put- messages
...

Each of the duplicate functions can optionally specify the name of the instance to which the old
instance will be copied
...
If the target instance already exists, it will be deleted directly or with a
delete message depending on which function was called
...
6
...
1 Directly Duplicating an Instance with Delayed Pattern-Matching
The duplicate-instance function uses the direct-duplicate message to change the values of the
instance
...

Syntax

(duplicate-instance [to ]
*)

Example

CLIPS> (clear)
CLIPS> (setgen 1)
1
CLIPS>
(defclass A (is-a USER)
(role concrete)
(slot foo (create-accessor write))
(slot bar (create-accessor write)))
CLIPS> (make-instance a of A (foo 0) (bar 4))
[a]
CLIPS> (watch all)
CLIPS> (duplicate-instance a)

124

Section 9 - CLIPS Object Oriented Language (COOL)

CLIPS Reference Manual
MSG >> direct-duplicate ED:1 ( [gen1] )
HND >> direct-duplicate primary in class USER
ED:1 ( [gen1] )
==> instance [gen1] of A
::= local slot foo in instance gen1 <- 0
::= local slot bar in instance gen1 <- 4
HND << direct-duplicate primary in class USER
ED:1 ( [gen1] )
MSG << direct-duplicate ED:1 ( [gen1] )
[gen1]
CLIPS> (unwatch all)
CLIPS>

9
...
8
...
Object pattern-matching occurs as slot modifications are being performed
...
6
...
3 Duplicating an Instance using Messages with Delayed Pattern-Matching
The message-duplicate-instance function uses the message-duplicate message to change the
values of the instance
...

Syntax
(message-duplicate-instance [to ]
*)

Example

CLIPS> (clear)
CLIPS>
(defclass A (is-a USER)
(role concrete)
(slot foo (create-accessor write))
(slot bar (create-accessor write)))
CLIPS> (make-instance a of A (foo 0) (bar 4))
[a]
CLIPS> (make-instance b of A)
[b]
CLIPS> (watch all)
CLIPS> (message-duplicate-instance a to b (bar 6))
MSG >> message-duplicate ED:1 ( [b] )
HND >> message-duplicate primary in class USER
ED:1 ( [b] )
MSG >> delete ED:2 ()
HND >> delete primary in class USER
ED:2 ()

CLIPS Basic Programming Guide

125

CLIPS Reference Manual
<== instance [b] of A
HND << delete primary in class USER
ED:2 ()
MSG << delete ED:2 ()
==> instance [b] of A
MSG >> create ED:2 ()
HND >> create primary in class USER
ED:2 ()
HND << create primary in class USER
ED:2 ()
MSG << create ED:2 ()
MSG >> put-bar ED:2 ( 6)
HND >> put-bar primary in class A
ED:2 ( 6)
::= local slot bar in instance b <- 6
HND << put-bar primary in class A
ED:2 ( 6)
MSG << put-bar ED:2 ( 6)
MSG >> put-foo ED:2 ( 0)
HND >> put-foo primary in class A
ED:2 ( 0)
::= local slot foo in instance b <- 0
HND << put-foo primary in class A
ED:2 ( 0)
MSG << put-foo ED:2 ( 0)
MSG >> init ED:2 ()
HND >> init primary in class USER
ED:2 ()
HND << init primary in class USER
ED:2 ()
MSG << init ED:2 ()
HND << message-duplicate primary in class USER
ED:1 ( [b] )
MSG << message-duplicate ED:1 ( [b] )
[b]
CLIPS> (unwatch all)
CLIPS>

9
...
8
...
Object pattern-matching occurs as slot modifications are being
performed
...
7 INSTANCE-SET QUERIES AND DISTRIBUTED ACTIONS
COOL provides a useful query system for determining and performing actions on sets of
instances of user-defined classes that satisfy user-defined queries
...
The specific details of each query
function will then be given
...
5 ?car2:price))
Instance-set query
(printout t ?car1 crlf))
Instance-set distributed action
[Albert-Maserati]
CLIPS>
Instance-set member variables

For all of the examples in this section, assume that the commands below have already been
entered:
Example

CLIPS>
(defclass PERSON (is-a USER)
(role abstract)
(slot sex (access read-only)
(storage shared))
(slot age (type NUMBER)
(visibility public)))
CLIPS>
(defmessage-handler PERSON put-age (?value)
(dynamic-put age ?value))

CLIPS Basic Programming Guide

127

CLIPS Reference Manual
CLIPS>
(defclass FEMALE (is-a PERSON)
(role abstract)
(slot sex (source composite)
(default female)))
CLIPS>
(defclass MALE (is-a PERSON)
(role abstract)
(slot sex (source composite)
(default male)))
CLIPS>
(defclass GIRL (is-a FEMALE)
(role concrete)
(slot age (source composite)
(default 4)
(range 0
...
9)))
CLIPS>
(defclass WOMAN (is-a FEMALE)
(role concrete)
(slot age (source composite)
(default 25)
(range 18
...
0)))
CLIPS>
(defclass BOY (is-a MALE)
(role concrete)
(slot age (source composite)
(default 4)
(range 0
...
9)))
CLIPS>
(defclass MAN (is-a MALE)
(role concrete)
(slot age (source composite)
(default 25)
(range 18
...
0)))
CLIPS>
(definstances PEOPLE
(Man-1 of MAN (age 18))
(Man-2 of MAN (age 60))
(Woman-1 of WOMAN (age 18))
(Woman-2 of WOMAN (age 60))
(Woman-3 of WOMAN)
(Boy-1 of BOY (age 8))
(Boy-2 of BOY)
(Boy-3 of BOY)
(Boy-4 of BOY)
(Girl-1 of GIRL (age 8))
(Girl-2 of GIRL))
CLIPS> (reset)
CLIPS>

9
...
1 Instance-set Definition
An instance-set is an ordered collection of instances
...
The class restrictions can be
different for each instance-set member
...
An instance-set template is a set of instance-set member variables and
their associated class restrictions
...
Variables may be used to specify the
classes for the instance-set template, but if the constant names of the classes are specified, the
classes must already be defined
...

Syntax

::= (+)

::= ( )
::=

::= +

Example
One instance-set template might be the ordered pairs of boys or men and girls or women
...
g
...

9
...
2 Instance-set Determination
COOL uses straightforward permutations to generate instance-sets that match an instance-set
template from the actual instances in the system
...

2) When there is more than one class that an instance-set member can be, iterate through the
classes from left to right
...

3a) Recursively examine instances of subclasses in the order that the subclasses were defined
...
Otherwise, only subclasses which are in scope
of the module to which the query class belongs will be examined
...
7
...

2
...

4
...

6
...

8
...

10
...

12
...

15
...

17
...

19
...

21
...

23
...

25
...

27
...

29
...


[Boy-4]
[Boy-4]
[Boy-4]
[Boy-4]
[Boy-4]
[Man-1]
[Man-1]
[Man-1]
[Man-1]
[Man-1]
[Man-2]
[Man-2]
[Man-2]
[Man-2]
[Man-2]

[Girl-1]
[Girl-2]
[Woman-1]
[Woman-2]
[Woman-3]
[Girl-1]
[Girl-2]
[Woman-1]
[Woman-2]
[Woman-3]
[Girl-1]
[Girl-2]
[Woman-1]
[Woman-2]
[Woman-3]

Example
Consider the following instance-set template:
((?f1 FEMALE) (?f2 FEMALE))

Twenty-five instance-sets would be generated in the following order:
1
...
[Girl-1] [Girl-2]
3
...
[Girl-1] [Woman-2]
5
...
[Girl-2] [Girl-1]
7
...
[Girl-2] [Woman-1]
9
...
[Girl-2] [Woman-3]
11
...
[Woman-1] [Girl-2]
13
...
[Woman-1]
15
...
[Woman-2]
17
...
[Woman-2]
19
...
[Woman-2]
21
...
[Woman-3]
23
...
[Woman-3]
25
...

9
...
3 Query Definition
A query is a user-defined boolean expression applied to an instance-set to determine if the
instance-set meets further user-defined restrictions
...

130

Section 9 - CLIPS Object Oriented Language (COOL)

CLIPS Reference Manual

Syntax
::=

Example
Continuing the previous example, one query might be that the two instances in an ordered pair
have the same age
...
4
...
If message-passing is not explicitly
required for reading a slot (i
...
there are no accessor daemons for reads), then this second method
of slot access should be used, for it gives a significant performance benefit
...

9
...
4 Distributed Action Definition
A distributed action is a user-defined expression evaluated for each instance-set which satisfies
a query
...
If more than one action is required, use the progn function (see section 12
...
5) to
group them
...

(printout t "(" ?man-or-boy "," ?woman-or-girl ")" crlf)

CLIPS Basic Programming Guide

131

CLIPS Reference Manual

9
...
5 Scope in Instance-set Query Functions
An instance-set query function can be called from anywhere that a regular function can be called
...
In addition, rebinding variables within
an instance-set function action is allowed
...
Binding variables is not allowed within a query
...

Example

CLIPS>
(deffunction count-instances (?class)
(bind ?count 0)
(do-for-all-instances ((?ins ?class)) TRUE
(bind ?count (+ ?count 1)))
?count)
CLIPS>
(deffunction count-instances-2 (?class)
(length (find-all-instances ((?ins ?class)) TRUE)))
CLIPS> (count-instances WOMAN)
3
CLIPS> (count-instances-2 BOY)
4
CLIPS>

Instance-set member variables are only in scope within the instance-set query function
...

Example

CLIPS>
(deffunction last-instance (?class)
(any-instancep ((?ins ?class)) TRUE)
?ins)
[PRCCODE3] Undefined variable ins referenced in deffunction
...
7
...


132

Section 9 - CLIPS Object Oriented Language (COOL)

CLIPS Reference Manual

9
...
7 Halting and Returning Values from Query Functions
The functions break and return are now valid inside the action of the instance-set query
functions do-for-instance, do-for-all-instances and delayed-do-for-all-instances
...

9
...
8 Instance-set Query Functions
The instance query system in COOL provides six functions
...
7
...
However,
if a particular instance is deleted and recreated, the iteration order will change
...
7
...
1 Testing if Any Instance-set Satisfies a Query
This function applies a query to each instance-set which matches the template
...
Otherwise, the return value is the symbol FALSE
...
7
...
2 Determining the First Instance-set Satisfying a Query
This function applies a query to each instance-set which matches the template
...
Otherwise, the return value is a zero-length multifield value
...

Syntax

(find-instance )

Example
Find the first pair of a man and a woman who have the same age
...
7
...
3 Determining All Instance-sets Satisfying a Query
This function applies a query to each instance-set which matches the template
...
This multifield value is returned when
the query has been applied to all possible instance-sets
...
The first n fields correspond to the first instance-set, and so on
...
The multifield
value can consume a large amount of memory due to permutational explosion, so this function
should be used judiciously
...

CLIPS>
(find-all-instances ((?m MAN) (?w WOMAN)) (= ?m:age ?w:age))
([Man-1] [Woman-1] [Man-2] [Woman-2])
CLIPS>

9
...
8
...
If an instance-set
satisfies the query, the specified action is executed, and the function is immediately terminated
...
If no instance-set satisfied the query, then the
return value is the symbol FALSE
...
The calls to neq in the query
eliminate the permutations where two or more members of the instance-set are identical
...
7
...
5 Executing an Action for All Instance-sets Satisfying a Query
This function applies a query to each instance-set which matches the template
...
The return value is the evaluation of the
action for the last instance-set which satisfied the query
...

Syntax

(do-for-all-instances *)

Example
Print out all triplets of different people that have the same age
...
Without these
restrictions, two instance-sets which differed only in the order of their members would both
satisfy the query
...
7
...
6 Executing a Delayed Action for All Instance-sets
Satisfying a Query
This function is similar to do-for-all-instances except that it groups all instance-sets which
satisfy the query into an intermediary multifield value
...
Otherwise, the specified action is
executed for each instance-set in the multifield value, and the return value is the evaluation of the
action for the last instance-set to satisfy the query
...
This function can consume large amounts of memory in the same fashion as
find-all-instances
...

Syntax
(delayed-do-for-all-instances
*)

CLIPS Basic Programming Guide

135

CLIPS Reference Manual

Example
Delete all boys with the greatest age
...
The action needs
to be delayed until all boys have been processed, or the greatest age will decrease as the older
boys are deleted
...
CLIPS modules allow a set of constructs to be grouped together such
that explicit control can be maintained over restricting the access of the constructs by other
modules
...
By restricting access to deftemplate and defclass
constructs, modules can function as blackboards, permitting only certain facts and instances to be
seen by other modules
...

10
...

Syntax
(defmodule []
*)
::= (export ) |
(import )


::= ?ALL |
?NONE |
?ALL |
?NONE |
+



::= deftemplate | defclass |
defglobal | deffunction |
defgeneric

A defmodule cannot be redefined or even deleted once it is defined (with the exception of the
MAIN module which can be redefined once)
...
Upon startup and after a clear command, CLIPS automatically constructs the
following defmodule
...
2) belong to the MAIN module
...
Discounting the
previous exception, the predefined MAIN module does not import or export any constructs
...


CLIPS Basic Programming Guide

137

CLIPS Reference Manual

Example
(defmodule
(import
(import
(import
(export
(export

FOO
BAR ?ALL)
YAK deftemplate ?ALL)
GOZ defglobal x y z)
defgeneric +)
defclass ?ALL))

10
...
The
deffacts, deftemplate, defrule, deffunction, defgeneric, defclass, and definstances constructs all
specify the module for the construct by including it as part of the name
...
The
module of a defmessage-handler is specified as part of the class specifier
...
For example, the following
constructs would be placed in the DETECTION module
...

CLIPS> (set-current-module B)
A
CLIPS> (list-defrules)
foo
For a total of 1 defrule
...
3 SPECIFYING MODULES
Commands such as undefrule and ppdefrule require the name of a construct on which to
operate
...
With modules,
however, it is possible to have a construct with the same name in two different modules
...
To explicitly
specify a name’s module the module name (a symbol) is listed followed by two colons, ::, and
then the name is listed
...
For
example, MAIN::find-stuff, refers to the find-stuff construct in the MAIN module
...
The current module is
changed whenever a defmodule construct is defined or the set-current-module function is used
...
Thus the name find-stuff would implicitly
have the MAIN module as its module when CLIPS is first started
...
4 IMPORTING AND EXPORTING CONSTRUCTS
Unless specifically exported and imported, the constructs of one module may not be used by
another module
...
For example, if module B wants to use the foo deftemplate defined in
module A, then module A must export the foo deftemplate and module B must import the foo
deftemplate from module A
...

10
...
1 Exporting Constructs
The export specification in a defmodule definition is used to indicate which constructs will be
accessible to other modules importing from the module being defined
...
A module may export any
valid constructs that are visible to it (not just constructs that it defines)
...
First, a module may export all valid
constructs that are visible to it
...
Second, a module may export all valid constructs of a particular type that are
visible to it
...
Third, a module may export specific constructs of a
particular type that are visible to it
...
In the following code, defmodule A exports all of its constructs; defmodule B
exports all of its deftemplates; and defmodule C exports the foo, bar, and yak defglobals
...

Defmethods and defmessage-handlers cannot be explicitly exported
...
Exporting a defclass automatically exports all
associated defmessage-handlers
...


140

Section 10 - Defmodule Construct

CLIPS Reference Manual

10
...
2 Importing Constructs
The import specification in a defmodule definition is used to indicate which constructs the
module being defined will use from other modules
...

There are three different types of import specifications
...
This accomplished by following the import
keyword with a module name followed by the ?ALL keyword
...
This accomplished by
following the import keyword with a module name followed by the name of the construct type
followed by the ?ALL keyword
...
This accomplished by following the import keyword with a module
name followed by the name of the construct type followed by the name of one or more visible
constructs of the specified type
...

(defmodule A (import D ?ALL))
(defmodule B (import D deftemplate ?ALL))
(defmodule C (import D defglobal foo bar yak))

The ?NONE keyword may be used in place of the ?ALL keyword to indicate either that no
constructs are imported from a module or that no constructs of a particular type are imported
from a module
...
Importing a defgeneric
automatically imports all associated defmethods
...
Deffacts, definstances, and defrules cannot be imported
...
In addition, if specific
constructs are listed in the import specification, they must already be defined in the module
exporting them
...
A construct can be indirectly imported from a module that directly imports and
then exports the module to be used
...
5 IMPORTING AND EXPORTING FACTS AND INSTANCES
Facts and instances are “owned” by the module in which their corresponding deftemplate or
defclass is defined, not by the module which creates them
...
This allows a

CLIPS Basic Programming Guide

141

CLIPS Reference Manual

knowledge base to be partitioned such that rules and other constructs can only “see” those facts
and instances which are of interest to them
...
Rules which
have the initial-fact or initial-object pattern added to their LHS (such as a rule thats first CE is a
not CE) will not be activated unless the corresponding construct for the pattern is imported
...

CLIPS> (facts B)
f-1
(foo (x 3))
For a total of 1 fact
...
5
...
The syntax of instance-names has been
extended to allow module specifications (note that the left and right brackets in bold are to be
typed and do not indicate an optional part of the syntax)
...
Specifying only the :: before the name, such as
[::Rolls-Royce], will search for the instance first in the current module and then recursively in
the imported modules as defined in the module definition
...
Regardless of which format is specified, the class of the instance must be in scope of the
current module in order for the instance to be found
...
6 MODULES AND RULE EXECUTION
Each module has its own pattern-matching network for its rules and its own agenda
...
Rule execution continues
until another module becomes the current focus, no rules are left on the agenda, or the return
function is used from the RHS of a rule
...
Before a rule executes, the current module is changed to
the module in which the executing rule is defined (the current focus)
...
See sections 5
...
4
...
2, 12
...
12 for more
details
...
" crlf)
(focus A B))
CLIPS>
(defmodule A (import MAIN deftemplate initial-fact))
CLIPS>
(defrule A::example-rule
=>
(printout t "Firing rule in module A
...
" crlf))
CLIPS> (reset)
CLIPS> (run)
Firing rule in module MAIN
...

Firing rule in module B
...
The constraint information is also analyzed for the patterns on the LHS of
a rule to determine if the specified constraints prevent the rule from ever firing
...
When static constraint
checking is enabled, constraint violations are checked when function calls and constructs are
parsed
...
When dynamic constraint checking is enabled, newly created data
objects (such as deftemplate facts and instances) have their slot values checked for constraint
violations
...
By default, static
constraint checking is enabled and dynamic constraint checking is disabled
...

Unless dynamic constraint checking is enabled, constraint information associated with constructs
is not saved when a binary image is created using the bsave command
...

Syntax

::= |
|
|


11
...

Syntax



::= (type )

::= + | ?VARIABLE

::= SYMBOL | STRING | LEXEME |
INTEGER | FLOAT | NUMBER |
INSTANCE-NAME | INSTANCE-ADDRESS | INSTANCE |
EXTERNAL-ADDRESS | FACT-ADDRESS

Using NUMBER for this attribute is equivalent to using both INTEGER and FLOAT
...
Using
CLIPS Basic Programming Guide

145

CLIPS Reference Manual

INSTANCE for this attribute is equivalent to using both INSTANCE-NAME and
INSTANCE-ADDRESS
...

11
...
The list of values provided should either be a list of constants of the
specified type or the keyword ?VARIABLE which means any constant of that type is allowed
...
Note the difference between using the attribute (allowed-symbols red
green blue) and (allowed-values red green blue)
...
The allowed-values
attribute completely restricts the allowed values to the listed values
...
Instead, if this attribute is specified and the slot value is either an instance address or
instance name, then the class to which the instance belongs must be a class specified in the
allowed-classes attribute or be a subclass of one of the specified classes
...
A string or symbol must match one of the constants in the attribute list
...
Similarly,
specifying the allowed-numbers attribute is equivalent to specifying constant restrictions on both
integers and floats
...
1, type conversion of integers to floats and floats to integers was
performed when using the allowed-numbers attribute (thus using allowed-numbers was not
equivalent to using both the allowed-integers and allowed-floats attributes together)
...
0, this type conversion is no longer performed
...
1 is no longer supported
...

11
...
If a numeric value is not used in that slot, then no checking is performed
...
Integers will be temporarily converted to floats when necessary to perform range
comparisons
...
If the keyword ?VARIABLE is used for the maximum value, then
the maximum value is positive infinity (+∞)
...

11
...

This attribute can not be used with a single field slot
...
If the keyword
?VARIABLE is used for the minimum value, then the minimum cardinality is zero
...
If the cardinality is not specified for a multifield slot, then it is assumed to be zero
to infinity
...
1 are no
longer supported
...

11
...
The following rules are used (in order) to
determine the default value for a slot with an unspecified default value
...

2) If the default type has an allowed constant restriction specified (such as the allowed-integers
attribute for the INTEGER type), then the first value specified in the allowed constant
attribute is chosen as the default value
...

4) If the default value was not specified by step 2 or 3, then the default default value is used
...
0 for type
FLOAT, [nil] for type INSTANCE-NAME, a pointer to a dummy instance for type
INSTANCE-ADDRESS, a pointer to a dummy fact for type FACT-ADDRESS, and the
NULL pointer for type EXTERNAL-ADDRESS
...
The default value for a multifield slot is a multifield value of
length zero
...


148

Section 11 - Constraint Attributes

CLIPS Reference Manual

11
...

Example 1

CLIPS>
(deftemplate bar
(slot a (type SYMBOL INTEGER))
(slot b (type INTEGER FLOAT))
(slot c (type SYMBOL STRING)))
CLIPS>
(defrule error
(bar (a ?x))
(bar (b ?x))
(bar (c ?x))
=>)
[RULECSTR1] Variable ?x in CE #3 slot c
has constraint conflicts which make the pattern unmatchable
ERROR:
(defrule error-4
(bar (a ?x))
(bar (b ?x))
(bar (c ?x))
=>)
CLIPS>

The first occurrence of the variable ?x in slot a of the first pattern restricts its allowed types to
either a symbol or integer
...
The final occurence of ?x in the third pattern
generates an error because slot c expects ?x to be either a symbol or a string, but its only allowed
type is an integer
...
The variable ?y,
found in the second pattern, can have a maximum of three fields
...
Since slot z in the the third pattern has a minimum cardinality of
seven, the variables ?x and ?y cannot satisfy the minimum cardinality restriction for this slot
...
Since the > function
expects numeric values for its arguments, an error occurs
...
The terms functions, actions, and commands should be
thought of interchangeably
...
The term action refers to a function having no return value but
performing some basic operation as a side effect (such as printout)
...

12
...

12
...
1 Testing For Numbers
The numberp function returns the symbol TRUE if its argument is a float or integer, otherwise it
returns the symbol FALSE
...
1
...

Syntax
(floatp )

12
...
3 Testing For Integers
The integerp function returns the symbol TRUE if its argument is an integer, otherwise it returns
the symbol FALSE
...
1
...

Syntax

(lexemep )

12
...
5 Testing For Strings
The stringp function returns the symbol TRUE if its argument is a string, otherwise it returns the
symbol FALSE
...
1
...
This function may also be called using the name wordp
...
1
...

Syntax
(evenp )

12
...
8 Testing For Odd Numbers
The oddp function returns the symbol TRUE if its argument is an odd number, otherwise it
returns the symbol FALSE
...
1
...
This function may also be called using the name
sequencep
...
1
...
External-addresses are discussed in further detail in the Advanced
Programming Guide
...
1
...
Note that eq compares types as
well as values
...
0) is FALSE since 3 is an integer and 3
...

Syntax

(eq +)

Example
CLIPS> (eq foo bar mumble foo)
FALSE
CLIPS> (eq foo foo foo foo)
TRUE
CLIPS> (eq 3 4)
FALSE
CLIPS>

12
...
12 Comparing for Inequality
The neq function returns the symbol TRUE if its first argument is not equal in value to all its
subsequent arguments, otherwise it returns the symbol FALSE
...
Thus, (neq 3 3
...
0 is a float
...
1
...
Note that = compares only
numeric values and will convert integers to floats when necessary for comparison
...
0)
TRUE
CLIPS> (= 4 4
...
In fact, you should be aware, even if code is not being ported, that roundoff error can
cause erroneous results
...
6666666666666666667
...
66666666666666666666 0
...
1
...
Note that <> compares only
numeric values and will convert integers to floats when necessary for comparison
...
0)

154

Section 12 - Actions and Functions

CLIPS Reference Manual
FALSE
CLIPS> (<> 4 4
...
1
...

12
...
15 Greater Than Comparison
The > function returns the symbol TRUE if for all its arguments, argument n-1 is greater than
argument n, otherwise it returns the symbol FALSE
...

Syntax

(> +)

Example
CLIPS> (> 5 4 3)
TRUE
CLIPS> (> 5 3 4)
FALSE
CLIPS>

Portability Note
See portability note in section 12
...
13
...
1
...
Note that >= compares only
numeric values and will convert integers to floats when necessary for comparison
...
1
...


CLIPS Basic Programming Guide

155

CLIPS Reference Manual

12
...
17 Less Than Comparison
The < function returns the symbol TRUE if for all its arguments, argument n-1 is less than
argument n, otherwise it returns the symbol FALSE
...

Syntax
(< +)

Example

CLIPS> (< 3 4 5)
TRUE
CLIPS> (< 3 5 4)
FALSE
CLIPS>

Portability Note
See portability note in section 12
...
13
...
1
...
Note that <= compares only
numeric values and will convert integers to floats when necessary for comparison
...
1
...

12
...
19 Boolean And
The and function returns the symbol TRUE if each of its arguments evaluates to TRUE,
otherwise it returns the symbol FALSE
...
Each argument of the function is evaluated from left to right
...


156

Section 12 - Actions and Functions

CLIPS Reference Manual

Syntax
(and +)

12
...
20 Boolean Or
The or function returns the symbol TRUE if any of its arguments evaluates to TRUE, otherwise
it returns the symbol FALSE
...
Each
argument of the function is evaluated from left to right
...

Syntax
(or +)

12
...
21 Boolean Not
The not function returns the symbol TRUE if its argument evaluates to FALSE, otherwise it
returns the symbol FALSE
...
2 MULTIFIELD FUNCTIONS
The following functions operate on multifield values
...
2
...

Syntax
(create$ *)

The return value of create$ is a multifield value regardless of the number or types of arguments
(single-field or multifield)
...

Example

CLIPS (create$ hammer drill saw screw pliers wrench)
(hammer drill saw screw pliers wrench)
CLIPS> (create$ (+ 3 4) (* 2 3) (/ 8 4))
(7 6 2)
CLIPS>

CLIPS Basic Programming Guide

157

CLIPS Reference Manual

12
...
2 Specifying an Element
The nth$ function will return a specified field from a multifield value
...
The symbol nil will be returned if the first argument is greater than the number
of fields in the second argument
...
2
...

Syntax

(member$ )

If the first argument is a single field value and is one of the fields within the second argument,
member$ will return the integer position of the field (from 1 to the length of the second
argument)
...
If neither of these
situations is satisfied, then FALSE is returned
...
7 blue))
5
CLIPS> (member$ 4 (create$ red 3 "text" 8
...
2
...
e
...

Syntax

(subsetp )

158

Section 12 - Actions and Functions

CLIPS Reference Manual

If the first argument is a subset of the second argument, the function returns TRUE; otherwise, it
returns FALSE
...
If the first argument is bound to a
multifield of length zero, the subsetp function always returns TRUE
...
2
...

Syntax

(delete$

)

The modified multifield value is returned, which is the same as with the
fields ranging from to removed
...

Example

CLIPS> (delete$ (create$ hammer drill saw pliers wrench) 3 4)
(hammer drill wrench)
CLIPS> (delete$ (create$ computer printer hard-disk) 1 1)
(printer hard-disk)
CLIPS>

12
...
6 Creating Multifield Values from Strings
...

Syntax
(explode$ )

A new multifield value is created in which each delimited field in order in is
taken to be a field in the new multifield value which is returned
...
Fields other than symbols, strings, integer, floats, or instances
names (such as parentheses or variables) are converted to strings
...
2
...

Syntax
(implode$ )

Each field in in order is concatenated into a string value with a single
blank separating fields
...

Example
CLIPS> (implode$ (create$ hammer drill screwdriver))
"hammer drill screwdriver wrench pliers saw"
CLIPS> (implode$ (create$ 1 "abc" def "ghi" 2))
"1 "abc" def "ghi" 2"
CLIPS> (implode$ (create$ "abc
def
ghi"))
""abc
def
ghi""
CLIPS>

12
...
8 Extracting a Sub-sequence from a Multifield Value
This function extracts a specified range from a multifield value and returns a new multifield
value containing just the sub-sequence
...

Example

CLIPS> (subseq$ (create$ hammer drill wrench pliers) 3 4)
(wrench pliers)
CLIPS> (subseq$ (create$ 1 "abc" def "ghi" 2) 1 1)
(1)
CLIPS>

160

Section 12 - Actions and Functions

CLIPS Reference Manual

12
...
9 Replacing Fields within a Multifield Value
This function replaces a range of field in a multifield value with a series of single-field and/or
multifield values and returns a new multifield value containing the replacement values within the
original multifield value
...

Example

CLIPS>
(drill
CLIPS>
(a x y
CLIPS>

(replace$ (create$ drill wrench pliers) 3 3 machete)
wrench machete)
(replace$ (create$ a b c d) 2 3 x y (create$ q r s))
q r s d)

12
...
10 Inserting Fields within a Multifield Value
This function inserts a series of single-field and/or multifield values at a specified location in a
multifield value with and returns a new multifield value containing the inserted values within the
original multifield value
...
This value must
be greater than or equal to 1
...
Any value greater than the length of the
appends the new values to the end of the
...
2
...
2
...

Syntax
(rest$ )

Example

CLIPS> (rest$ (create$ a b c))
(b c)
CLIPS> (rest$ (create$))
()
CLIPS>

12
...
13 Determining the Number of Fields in a Multifield Value
The length$ function returns an integer indicating the number of fields contained in a multifield
value
...

Syntax

(length$ )

Example
CLIPS> (length$ (create$ a b c d e f g))
7
CLIPS>

12
...
14 Deleting Specific Values within a Multifield Value
This function deletes specific values contained within a multifield value and returns the modified
multifield value
...
If
is a multifield value, the entire sequence must be contained within the first
argument in the correct order
...
2
...

Syntax

(replace-member$
+)

where any that is contained within is replaced by

...
3 STRING FUNCTIONS
The following functions perform operations that are related to strings
...
3
...

Syntax

(str-cat *)

CLIPS Basic Programming Guide

163

CLIPS Reference Manual

Each should be one of the following types: symbol, string, float, integer, or
instance-name
...
3
...
It is functionally
identical to the str-cat function with the exception that the returned value is a symbol and not a
string
...

12
...
3 Taking a String Apart
The sub-string function will retrieve a portion of a string from another string
...
If the first argument is greater than the second argument, a null string is returned
...
3
...

Syntax

(str-index

164

)

Section 12 - Actions and Functions

CLIPS Reference Manual

where the second argument is searched for the first occurrence of the first argument
...

Example

CLIPS> (str-index "def" "abcdefghi")
4
CLIPS> (str-index "qwerty" "qwertypoiuyt")
1
CLIPS> (str-index "qwerty" "poiuytqwer")
FALSE
CLIPS>

12
...
5 Evaluating a Function within a String
The eval function evaluates the string as though it were entered at the command prompt
...
NOTE:
eval does not permit the use of local variables (except when the local variables are defined as
part of the command such as with an instance query function), nor will it evaluate any of the
construct definition forms (i
...
, defrule, deffacts, etc
...

The eval function is not available for binary-load only or run-time CLIPS configurations (see the
Advanced Programming Guide)
...
3
...

Syntax
(build

)

where the only argument is the construct to be added
...


CLIPS Basic Programming Guide

165

CLIPS Reference Manual

The build function is not available for binary-load only or run-time CLIPS configurations (see
the Advanced Programming Guide)
...

CLIPS>

12
...
7 Converting a String to Uppercase
The upcase function will return a string or symbol with uppercase alphabetic characters
...
3
...

Syntax
(lowcase )

Example
CLIPS> (lowcase "This is a test of lowcase")
"this is a test of lowcase"
CLIPS> (lowcase A_Word_Test_for_Lowcase)
a_word_test_for_lowcase
CLIPS>

12
...
9 Comparing Two Strings
The str-compare function will compare two strings to determine their logical relationship (i
...
,
equal to, less than, greater than)
...
The positions of
the unequal characters within the ASCII character set are used to determine the logical
relationship of unequal strings
...

Example
CLIPS> (< (str-compare "string1" "string2") 0)
TRUE
; since "1" < "2" in ASCII character set
CLIPS> (str-compare "abcd" "abcd")
0
CLIPS>

12
...
10 Determining the Length of a String
The str-length function returns the length of a string as an integer
...
3
...

Syntax
(check-syntax )

This function returns FALSE if there are no errors or warnings encountered parsing the construct
or function call
...
The symbol EXTRANEOUS-INPUT-AFTER-LAST-PARENTHESIS is
returned if there are additional tokens after the closing right parenthesis of the construct or
function call
...
The first field of the multifield is a string containing the text of the error message (or
the symbol FALSE if no errors were encountered)
...

CLIPS Basic Programming Guide

167

CLIPS Reference Manual

Example
CLIPS> (check-syntax "(defrule example =>)")
FALSE
CLIPS> (check-syntax "(defrule foo (number 40000000000000) =>)")
(FALSE "[SCANNER1] WARNING: Over or underflow of long integer
...

ERROR:
(defrule MAIN::example
(3
" FALSE)
CLIPS>

12
...
12 Converting a String to a Field
The string-to-field function parses a string and converts its contents to a primitive data type
...
Essentially calling string-to-field with its
string argument is equivalent to calling the read function and manually typing the contents of the
string argument or reading it from a file
...

Example
CLIPS> (string-to-field "3
...
4
CLIPS> (string-to-field "a b")
a
CLIPS>

12
...
A
more complete discussion of I/O routers is covered in the Advanced Programming Guide
...
4
...
Logical names allow
reference to an I/O device without having to understand the details of the implementation of the
reference
...
A logical name can be either a
168

Section 12 - Actions and Functions

CLIPS Reference Manual

symbol, a number, or a string
...
These are
Name
stdin
stdout

wclips
wdialog
wdisplay
werror
wwarning
wtrace

Description
The default for all user inputs
...

The default for all user outputs
...

The CLIPS prompt is sent to this logical name
...

Requests to display CLIPS information, such as facts or rules,
are sent to this logical name
...

All warning messages are sent to this logical name
...


Any of these logical names may be used anywhere a logical name is expected
...
4
...

12
...
2
...
This function takes three arguments: (1) the name of the file to be opened; (2) the
logical name which will be used by other CLIPS I/O functions to access the file; and (3) an
optional mode specifier
...
The access mode may not
be meaningful in some operating systems
...
If a
string is used, the backslash (\) and any other special characters that are part of must
be escaped with a backslash
...
The open
function returns TRUE if it was successful, otherwise FALSE
...
clp" writeFile "w")
TRUE
CLIPS> (open "MS-DOS\\directory\\file
...
4
...
2 Close
The close function closes a file stream previously opened with the open command
...

Syntax
(close [])

If close is called without arguments, all open files will be closed
...
If files are not closed, the contents are not guaranteed
correct, however, CLIPS will attempt to close all open files when the exit command is executed
...

Example
CLIPS>
TRUE
CLIPS>
TRUE
CLIPS>
TRUE
CLIPS>
FALSE
CLIPS>
TRUE
CLIPS>
FALSE
CLIPS>

170

(open "myfile
...
clp" readFile)
(close writeFile)
(close writeFile)
(close)
(close)

Section 12 - Actions and Functions

CLIPS Reference Manual

12
...
2
...
The logical name
must be specified and the device must have been prepared previously for output (e
...
, a file must
be opened first)
...
If the logical name nil is
used, the printout function does nothing
...
Each expression is
evaluated and printed (with no spaces added between each printed expression)
...
Similarly, the symbols tab, vtab, and ff will print respectively a
tab, a vertical tab, and a form feed
...
The printout function strips quotation marks from around strings
when it prints them
...
This function has no return value
...
txt" mydata "w")
TRUE
CLIPS> (printout mydata "red green")
CLIPS> (close)
TRUE
CLIPS>

12
...
2
...
All of the standard field
rules (e
...
, multiple symbols must be embedded within quotes) apply
...
If specified, read tries to read from whatever is
attached to the logical file name
...
All the delimiters defined in section 2
...
1 can be used as delimiters
...
Spaces, carriage returns, and tabs only act as
delimiters and are not contained within the return value (unless these characters are included
within double quotes as part of a string)
...
If errors are encountered while reading, the string "*** READ
ERROR ***" will be returned
...
txt" mydata "w")
(printout mydata "red green")
(close)
(open "data
...
4
...
5 Readline
The readline function is similar to the read function, but it allows a whole string to be input
instead of a single field
...
The readline
function only stops when it encounters a carriage return, a semicolon, or an EOF
...
The readline function returns
a string
...
If specified, readline tries to read from
whatever is attached to the logical file name
...
As with the read function, if an EOF is encountered, readline will
return the symbol EOF
...

Example
CLIPS> (open "data
...
txt" mydata)
TRUE
CLIPS> (readline mydata)
"red green"
CLIPS> (readline mydata)
EOF
CLIPS> (close)
TRUE
CLIPS>

172

Section 12 - Actions and Functions

CLIPS Reference Manual

12
...
2
...
It can be used in place of printout when special formatting of output information is
desired
...
The format commands are similar to the printf statement in C
...
A logical name of
nil may be used when the formatted return string is desired without writing to a device
...
The second argument to format, called the control string,
specifies how the output should be formatted
...
Format currently does not allow expressions returning multifield values to be included in
the parameter list
...
Text is output exactly as specified, and
format flags describe how each parameter in the parameter list is to be formatted
...
The format flags must be preceded by a percent sign (%) and are of the general
format
%-M
...
If M is used, at least M characters will be output
...
If
M starts with a 0 (e
...
, %07d), a zero is used as the pad character; otherwise, spaces are used
...
If a minus sign is included
before the M, the value will be left justified; otherwise the value is right justified
...

Display parameter as a long integer
...
)

f

Display parameter as a floating-point number (The N specifier is the
number of digits following the decimal point)
...


g

Display parameter in the most general format, whichever is shorter
(the N specifier is the number of significant digits to be printed)
...
(The N specifier is
the minimum number of digits to be printed
...
(The N
specifier is the minimum number of digits to be printed
...
Strings will have the leading and
trailing quotes stripped
...
Zero also cannot be used for the
pad character
...


r

Put a carriage return in the output
...


Example

CLIPS> (format t "Hello World!%n")
Hello World!
"Hello World!
"
CLIPS> (format nil "Integer:
|%d|" 12)
"Integer:
|12|"
CLIPS> (format nil "Integer:
|%4d|" 12)
"Integer:
| 12|"
CLIPS> (format nil "Integer:
|%-04d|" 12)
"Integer:
|12 |"
CLIPS> (format nil "Integer:
|%6
...
01)
"Float:
|12
...
2f| "12
...
01| "
CLIPS> (format nil "Test:
|%e|" 12
...
201000e+01|"
CLIPS> (format nil "Test:
|%7
...
01)
"Test:
|1
...
23457e+09|"
CLIPS> (format nil "General:
|%6
...
23e+09|"
CLIPS> (format nil "Hexadecimal: |%x|" 12)
"Hexadecimal: |c|"
CLIPS> (format nil "Octal:
|%o|" 12)
"Octal:
|14|"
CLIPS> (format nil "Symbols:
|%s| |%s|" value-a1 capacity)
"Symbols:
|value-a1| |capacity|"
CLIPS>

Portability Note
The format function uses the C function sprintf as a base
...

12
...
2
...

Syntax
(rename )

Both and must either be a string or symbol and may include
directory specifiers
...
The
rename function returns TRUE if it was successful, otherwise FALSE
...

12
...
2
...

Syntax

(remove )

CLIPS Basic Programming Guide

175

CLIPS Reference Manual

The must either be a string or symbol and may include directory specifiers
...
The remove function returns TRUE if it was successful, otherwise
FALSE
...

12
...
2
...

Syntax
(get-char [])

where is an optional parameter
...
If is t or is not specified, the function will
read from stdin
...
The value
of -1 is returned if the end of file is encountered while retrieving a character
...
txt example "w")
(printout example "ABC" crlf)
(close example)
(open example
...
")
(get-char t))
Press any character to continue
...
4
...
10 Read Number
The read-number function allows a user to input a single number using the localized format (if
one has been specified using the set-locale function)
...

Syntax
(read-number [])

where is an optional parameter
...
If is t or is not specified, the
function will read from stdin
...
If an end of file (EOF) is
encountered while reading, read-number will return the symbol EOF
...

Example

CLIPS> (read-number)
34
34
CLIPS> (read-number)
34
...
0
CLIPS> (read-number)
23,0
"*** READ ERROR ***"
CLIPS>

12
...
2
...
Before a number is printed by the format
function or is parsed by the read-number function, the locale is temporarily changed to the last
value specified to the set-locale function (or the default C locale if no value was previously
specified)
...
If is specified, then the value of the
previous locale is returned
...
A value of "" uses the native locale (and the specification of this
locale is dependent on the environment in which CLIPS is run)
...

CLIPS Basic Programming Guide

177

CLIPS Reference Manual

Example
;;; This example assumes that the native
;;; locale has been set to Germany
...
21
3
...
1)
"3
...
21
"*** READ ERROR ***"
CLIPS> (read-number)
3,21
3
...
1)
"3,100000"
CLIPS>

Portability Note
The CLIPS set-locale function uses the ANSI C function setlocale to temporarily change the
locale
...
For example, in Windows XP
the native locale is set by clicking on the Start menu, selecting Control Panel, selecting Regional
and Language Options, selecting the Regional Options tab, and then selecting a region from the
drop-down menu such as German (Germany)
...
5 MATH FUNCTIONS
CLIPS provides several functions for mathematical computations
...

12
...
1 Standard Math Functions
The standard math functions are listed below
...
An error message will be printed if a string argument is passed to a math function
...
5
...
1 Addition
The + function returns the sum of its arguments
...
Addition is performed using the type of the arguments provided unless mixed mode
arguments (integer and float) are used
...
This
function returns a float if any of its arguments is a float, otherwise it returns an integer
...
0 5)
10
...
1 4
...
8
CLIPS>

12
...
1
...

Each of its arguments should be a numeric expression
...
In this case,
the function return value and integer arguments are converted to floats after the first float
argument has been encountered
...

Syntax

(- +)

Example
CLIPS> (- 12 3 4)
5
CLIPS> (- 12 3
...
0
CLIPS> (- 4
...
1)
1
...
5
...
3 Multiplication
The * function returns the product of its arguments
...
Multiplication is performed using the type of the arguments provided unless mixed
mode arguments (integer and float) are used
...
This
function returns a float if any of its arguments is a float, otherwise it returns an integer
...
0 5)
30
...
1 4
...
57
CLIPS>

12
...
1
...
Each of its arguments should be a numeric expression
...
In
this case, the function return value and integer arguments are converted to floats after the first
float argument has been encountered
...

The function set-auto-float-dividend can be used to control this behavior
...
0) evaluates to 0
...
333333333 if this feature were enabled
...

Syntax
(/ +)

Example

CLIPS> (/ 4 2)
2
...
0 2
...
0
CLIPS> (/ 24 3 4)
2
...
5
...
5 Integer Division
The div function returns the value of the first argument divided by each of the subsequent
arguments
...
Each argument is
automatically converted to an integer and integer division is performed
...

Syntax

(div +)

Example
CLIPS> (div 4 2)
2
CLIPS> (div 5 2)
180

Section 12 - Actions and Functions

CLIPS Reference Manual
2
CLIPS> (div 33 2 3 5)
1
CLIPS>

12
...
1
...
Each of its arguments should
be a numeric expression
...
The return value will either be integer or float (depending upon the type of the
largest argument)
...
0 4 2
...
5
...
7 Minimum Numeric Value
The min function returns the value of its smallest numeric argument
...
When necessary, integers are temporarily converted to floats for
comparison
...

Syntax
(min +)

Example
CLIPS> (min 4 0
...
3)
-2
...
5
...
8 Absolute Value
The abs function returns the absolute value of its only argument (which should be a numeric
expression)
...

Syntax

(abs )

Example

CLIPS> (abs 4
...
0
CLIPS> (abs -2)
2
CLIPS>

12
...
1
...

Syntax
(float )

Example
CLIPS> (float 4
...
0
CLIPS> (float -2)
-2
...
5
...
10 Convert To Integer
The integer function converts its only argument (which should be a numeric expression) to type
integer and returns this value
...
0)
4
CLIPS> (integer -2)
-2
CLIPS>

12
...
2 Extended Math Functions
In addition to standard math functions, CLIPS also provides a large number of scientific and
trigonometric math functions for more extensive computations
...

Portability Note
These mathematical functions use the C library math
...
If the user’s system does not support
this library, the user needs to make some adjustments to math
...
The system-dependent math
182

Section 12 - Actions and Functions

CLIPS Reference Manual

functions are called from CosFunction, SinFunction, etc
...
The user also must make sure that the functions CosFunction, SinFunction, etc
...

To link these functions, most compilers provide a separate math library that must be included
during linking
...
5
...
1 Trigonometric Functions
The following trigonometric functions take one numeric argument and return a floating-point
number
...

FUNCTION
acos
acosh
acot
acoth
acsc
acsch
asec
asech
asin
asinh
atan
atanh
cos
cosh
cot
coth
csc
csch
sec
sech
sin
sinh
tan
tanh

RETURNS
arccosine
hyperbolic arccosine
arccotangent
hyperbolic arccotangent
arccosecant
hyperbolic arccosecant
arcsecant
hyperbolic arcsecant
arcsine
hyperbolic arcsine
arctangent
hyperbolic arctangent
cosine
hyperbolic cosine
cotangent
hyperbolic tangent
cosecant
hyperbolic cosecant
secant
hyperbolic secant
sine
hyperbolic sine
tangent
hyperbolic tangent

Example

CLIPS> (cos 0)
1
...
0)
0
...
5
...
2 Convert From Degrees to Grads
The deg-grad function converts its only argument (which should be a numeric expression) from
units of degrees to units of grads (360 degrees = 400 grads)
...

Syntax
(deg-grad )

Example

CLIPS> (deg-grad 90)
100
...
5
...
3 Convert From Degrees to Radians
The deg-rad function converts its only argument (which should be a numeric expression) from
units of degrees to units of radians (360 degrees = 2π radians)
...

Syntax

(deg-rad )

Example
CLIPS> (deg-rad 180)
3
...
5
...
4 Convert From Grads to Degrees
The grad-deg function converts its only argument (which should be a numeric expression) from
units of grads to units of degrees (360 degrees = 400 grads)
...

Syntax
(grad-deg )

Example

CLIPS> (grad-deg 100)
90
...
5
...
5 Convert From Radians to Degrees
The rad-deg function converts its only argument (which should be a numeric expression) from
units of radians to units of degrees (360 degrees = 2π radians)
...

Syntax
(rad-deg )

Example

CLIPS> (rad-deg 3
...
0
CLIPS>

12
...
2
...
141592653589793
...

Syntax

(pi)

Example
CLIPS> (pi)
3
...
5
...
7 Square Root
The sqrt function returns the square root of its only argument (which should be a numeric
expression) as a float
...
0
CLIPS>

12
...
2
...

Syntax

(** )

CLIPS Basic Programming Guide

185

CLIPS Reference Manual

Example
CLIPS> (** 3 2)
9
...
5
...
9 Exponential
The exp function raises the value e (the base of the natural system of logarithms, having a value
of approximately 2
...
) to the power specified by its only argument and returns this value as a
float
...
718281828459045
CLIPS>

12
...
2
...
718281828459045)
0
...
5
...
11 Logarithm Base 10
Given n (the only argument), the log10 function returns the float value x such that the following
equation is satisfied:
n = 10

x

Syntax
(log10 )

Example
CLIPS> (log10 100)
186

Section 12 - Actions and Functions

CLIPS Reference Manual
2
...
5
...
12 Round
The round function rounds its only argument (which should be a numeric expression) toward the
closest integer
...
The return
value of this function is an integer
...
6)
4
CLIPS>

12
...
2
...
It returns an integer if both
arguments are integers, otherwise it returns a float
...
7 1
...
1
CLIPS>

12
...

12
...
1 Binding Variables
Occasionally, it is important to create new variables or to modify the value of previously bound
variables on the RHS of a rule
...

Syntax

(bind *)

CLIPS Basic Programming Guide

187

CLIPS Reference Manual

where the first argument to bind, , is the local or global variable to be bound (it may
have been bound previously)
...

If no is specified, then local variables are unbound and global variables are reset to
their original value
...
If more than one is specified, then all
of the are evaluated and grouped together as a multifield value and the resulting
value is stored in
...

Example 1

CLIPS> (defglobal ?*x* = 3
...
4
CLIPS> (bind ?*x* (+ 8 9))
17
CLIPS> ?*x*
17
CLIPS> (bind ?*x* (create$ a b c d))
(a b c d)
CLIPS> ?*x*
(a b c d)
CLIPS> (bind ?*x* d e f)
(d e f)
CLIPS> ?*x*
(d e f)
CLIPS> (bind ?*x*)
3
...
4
CLIPS>

Example 2

CLIPS>
(defclass A (is-a USER)
(role concrete)
(slot x) (slot y))
CLIPS>
(defmessage-handler A init after ()
(bind ?self:x 3)
(bind ?self:y 4))
CLIPS> (make-instance a of A)
[a]
CLIPS> (send [a] print)
[a] of A
(x 3)
(y 4)
CLIPS>

188

Section 12 - Actions and Functions

CLIPS Reference Manual

12
...
X Foreach
The foreach function performs a set of actions for each field of a multifield value
...
The index of the current
iteration can be examined with -index
...
The return value of this function is the return value of the last
action performed for the last field in the multifield value
...
It is provided for compatibility with Jess (Java
Expert System Shell)
...
6
...
then
...
then
...

Syntax

(if
then
*
[else
*])

Any number of allowable actions may be used inside of the then or else portion, including
another if
...
else structure
...
If evaluates to
anything other than the symbol FALSE, then the actions associated with the then portion are
executed
...
The return value
of the if function is the value of the last or evaluated
...

(defrule closed-valves-number-6
(temp high)
(valve 6 closed)
=>
(printout t "The special valve 6 is closed!" crlf)
(assert (perform special operation)))
(defrule closed-valves-other-than-6
(temp high)
(valve ?v&~6 closed)
=>
(printout t "Valve " ?v " is normally closed" crlf))

12
...
3 While
The while function is provided to allow simple looping
...

Syntax
(while [do]
*)

Again, all predicate functions are available for use in while
...
then
...

The test is performed prior to the first execution of the loop
...
The while may optionally
include the symbol do after the condition and before the first action
...
The return value of this function is
FALSE unless the return function is used to terminate the loop
...
6
...

Syntax
(loop-for-count [do] *)


::= |
( ) |
( )
::=

::=

Performs the given actions the number of times specified by
...
If is greater than , then the body of
the loop is never executed
...
The break and return functions can be used to terminate the loop
prematurely
...
Variables from an outer scope may be used within the loop, but the loop
variable (if specified) masks any outer variables of the same name
...

Example

CLIPS> (loop-for-count 2 (printout t "Hello world" crlf))
Hello world
Hello world
FALSE
CLIPS>
(loop-for-count (?cnt1 2 4) do
(loop-for-count (?cnt2 1 3) do
(printout t ?cnt1 " " ?cnt2 crlf)))
2 1
2 2
2 3
3 1
3 2
3 3
4 1
4 2
4 3
FALSE
CLIPS>

12
...
5 Progn
The progn function evaluates all of its arguments and returns the value of the last argument
...
6
...
The field of
the current iteration can be examined with , if specified
...
The progn$ function can use variables
from outer scopes, and the return and break functions can also be used within a progn$ as long
as they are valid in the outer scope
...

Syntax

(progn$ *)
::=

|
( )

Example

CLIPS> (progn$ (?field (create$ abc def ghi))
(printout t "--> " ?field " " ?field-index " <--" crlf))
--> abc 1 <---> def 2 <---> ghi 3 <-CLIPS>

12
...
7 Return
The return function immediately terminates the currently executing deffunction, generic
function method, message-handler, defrule RHS, or certain instance set query functions
(do-for-instance, do-for-all-instances and delayed-do-for-all-instances)
...
However, if an argument is included, its evaluation is given
as the return value of the deffunction , method or message-handler
...
If used on the
RHS of a rule, the current focus is removed from the focus stack
...
If used within an instance set query function, the
return function is only valid if it is applicable in the outer scope of the query
...
6
...

The break function can only be used within the actions of a while loop, loop-for-count
execution, progn execution, progn$ execution, foreach execution, or the specified instance set
queries previously listed
...
The break cannot be used within a
progn unless it is valid for the outer scope of the progn
...

Syntax
(break)

Example

CLIPS>
(deffunction iterate (?num)
(bind ?i 0)
(while TRUE do
(if (>= ?i ?num) then
(break))
(printout t ?i " ")
(bind ?i (+ ?i 1)))
(printout t crlf))
CLIPS> (iterate 1)
0
CLIPS> (iterate 10)
0 1 2 3 4 5 6 7 8 9
CLIPS>

12
...
9 Switch
The switch function allows a particular group of actions (among several groups of actions) to be
performed based on a specified value
...
None
of the case comparison expressions should be the same
...

Once the evaluation of the
is equivalent to the evaluation of the , the actions of
that case are evaluated (in order) and the switch function is terminated
...

The return value of the switch function is the last action evaluated in the switch function
...

Example
CLIPS> (defglobal ?*x* = 0)
CLIPS> (defglobal ?*y* = 1)
CLIPS>
(deffunction foo (?val)
(switch ?val
(case ?*x* then *x*)
(case ?*y* then *y*)
(default none)))
CLIPS> (foo 0)
*x*
CLIPS> (foo 1)
*y*
CLIPS> (foo 2)
none
CLIPS>

12
...

12
...
1 Gensym
The gensym function returns a special, sequenced symbol that can be stored as a single field
...
Multiple calls to gensym are guaranteed to return different identifiers of
the form
genX

where X is a positive integer
...
Note that gensym is not reset after a call to clear
...

Example

(assert (new-id (gensym) flag1 7))

which, on the first call, generates a fact of the form
(new-id gen1 flag1 7)

12
...
2 Gensym*
The gensym* function is similar to the gensym function, however, it will produce a unique
symbol that does not currently exist within the CLIPS environment
...
7
...
7
...
7
...

Syntax

(setgen )

where must be a positive integer value and is the value returned by this
function
...

Example
CLIPS> (setgen 32)

CLIPS Basic Programming Guide

195

CLIPS Reference Manual
32
CLIPS>

After this, calls to gensym will return gen32, gen33, etc
...
7
...
It is patterned after the ANSI standard
rand library function and therefore may not be available on all platforms
...

Example

(defrule roll-the-dice
(roll-the-dice)
=>
(bind ?roll1 (random 1 6))
(bind ?roll2 (random 1 6))
(printout t "Your roll is:

" ?roll1 " " ?roll2 crlf))

12
...
5 Seed
The seed function seeds the random number generator
...

Syntax

(seed )

where is the integer seed value and the function has no return value
...
7
...

Syntax

(time)

Portability Note
Not all operating systems/compilers provide this function
...
c file,
and the default coding for generic CLIPS is a non-functional stub that returns zero for the time
...
7
...

Syntax

(length )

If the argument given to length is not the appropriate type, a negative one (-1) is returned
...

Example

CLIPS> (length (create$ a b c d e f g))
7
CLIPS> (length "cat")
3
CLIPS>

12
...
8 Determining the Restrictions for a Function
The get-function-restrictions function can be used to gain access to the restriction string
associated with a CLIPS or user defined function
...
See section 3
...

Syntax

(get-function-restrictions )

Example
CLIPS> (get-function-restrictions +)
"2*n"
CLIPS>

12
...
9 Sorting a List of Values
The function sort allows a list of values to be sorted based on a user specified comparison
function
...
The
comparison function used for sorting should accept exactly two arguments and can be a userdefined function, a generic function, or a deffunction
...

Example
CLIPS> (sort > 4 3 5
(2 3 4 5 7 7)
CLIPS>
(deffunction string>
(> (str-compare ?a
CLIPS> (sort string>
(aa ax bk ft m mn)
CLIPS>

7 2 7)

(?a ?b)
?b) 0))
ax aa bk mn ft m)

12
...
10 Calling a Function
The function funcall constructs a function call from its arguments and then evaluates the
function call
...
The remaining arguments are evaluated and then passed to the specified
function when it is evaluated
...

Syntax
(funcall (function-name> *)

Example

CLIPS> (funcall delete$ (create$ a b c) 2 2)
(a c)
CLIPS> (funcall + 1 2 (expand$ (create$ 3 4)))
10
CLIPS>

12
...
11 Timing Functions and Commands
The function timer returns the number of seconds elapsed evaluating a series of expressions
...
0416709999999512
CLIPS>

198

Section 12 - Actions and Functions

CLIPS Reference Manual

12
...

12
...
1 Determining the Module in which a Deftemplate is Defined
This function returns the module in which the specified deftemplate name is defined
...
8
...
If no allowed-… attributes were specified for the slot, then
the symbol FALSE is returned
...

Syntax

(deftemplate-slot-allowed-values )

Example

CLIPS> (clear)
CLIPS>
(deftemplate A
(slot x)
(slot y (allowed-integers 2 3) (allowed-symbols foo)))
CLIPS> (deftemplate-slot-allowed-values A x)
FALSE
CLIPS> (deftemplate-slot-allowed-values A y)
(2 3 foo)
CLIPS>

12
...
3 Getting the Cardinality for a Deftemplate Slot
This function groups the minimum and maximum cardinality allowed for a multifield slot into a
multifield variable
...
A multifield of length zero is returned for
single field slots or if an error occurs
...
8
...
An error is generated
if the specified deftemplate or slot does not exist
...
8
...
If a slot has a dynamic
default, the expression will be evaluated when this function is called
...

Syntax
(deftemplate-slot-default-value )

Example

CLIPS> (clear)
CLIPS>
(deftemplate A

200

Section 12 - Actions and Functions

CLIPS Reference Manual
(slot x (default 3))
(multislot y (default a b c))
(slot z (default-dynamic (gensym))))
CLIPS> (deftemplate-slot-default-value
3
CLIPS> (deftemplate-slot-default-value
(a b c)
CLIPS> (deftemplate-slot-default-value
gen1
CLIPS> (deftemplate-slot-default-value
gen2
CLIPS>

A x)
A y)
A z)
A z)

12
...
6 Deftemplate Slot Existence
This function returns the symbol TRUE if the specified slot is present in the specified
deftemplate, FALSE otherwise
...
8
...
Otherwise, it returns the symbol FALSE
...

Syntax
(deftemplate-slot-multip )

Example
CLIPS>
CLIPS>
CLIPS>
FALSE
CLIPS>
TRUE
CLIPS>

(clear)
(deftemplate A (slot x) (multislot y))
(deftemplate-slot-multip A x)
(deftemplate-slot-multip A y)

CLIPS Basic Programming Guide

201

CLIPS Reference Manual

12
...
8 Determining the Slot Names Associated with a Deftemplate
The deftemplate-slot-names function returns the slot names associated with the deftemplate in a
multifield value
...
FALSE is returned if the specified deftemplate does not exist
...
8
...
A minimum value of infinity is indicated by the symbol -oo (the minus character
followed by two lowercase o’s—not zeroes)
...
The symbol FALSE
is returned for slots in which numeric values are not allowed
...

Syntax

(deftemplate-slot-range )

Example
CLIPS> (clear)
CLIPS>
(deftemplate A
(slot x)
(slot y (type SYMBOL))
(slot z (range 3 10)))
CLIPS> (deftemplate-slot-range A x)
(-oo +oo)
CLIPS> (deftemplate-slot-range A y)
FALSE
CLIPS> (deftemplate-slot-range A z)
(3 10)
CLIPS>

12
...
10 Testing whether a Deftemplate Slot is a Single-Field Slot
This function returns the symbol TRUE if the specified slot in the specified deftemplate is a
single-field slot
...
An error is generated if the specified
deftemplate or slot does not exist
...
8
...
A multifield of length zero is returned if an error occurs
...
8
...
If * is specified as the module name, then all deftemplates are
returned
...
9 FACT FUNCTIONS
The following actions are used for assert, retracting, and modifying facts
...
9
...
Multiple facts may be asserted with
each call
...
2), then an informational message
will be printed each time a fact is asserted
...
If
an identical copy of the fact already exists in the fact-list, the fact will not be added (however,
this behavior can be changed, see sections 13
...
4 and 13
...
5)
...
The first field of a fact must be a symbol
...
If the
assertion of the last fact causes an error, or if an identical copy of the fact already exists in the
fact-list, then the symbol FALSE is returned
...

CLIPS>

12
...
2 Removing Facts from the Fact-list
The retract action allows the user to remove facts from the fact-list
...
The retraction of a fact also removes all rules that
depended upon that fact for activation from the agenda
...
If the facts item is
being watched (see section 13
...

Syntax
(retract + | *)

204

Section 12 - Actions and Functions

CLIPS Reference Manual

::= |

The term includes variables bound on the LHS to fact-addresses as described
in section 5
...
1
...
g
...
If the symbol * is used as an argument, all facts
will be retracted
...
Only variables, fact indices,
or the symbol * may be used in a retract
...
This function has
no return value
...
9
...
Only one fact may be
modified with a single modify statement
...
Therefore, any facts receiving logical support
from a template fact are retracted (assuming no other support) when the template fact is modified
and the new template fact loses any logical support that it previously had
...
4
...
8 or the fact-index of the desired fact (e
...
3 for the fact labeled f-3)
...
Static deftemplate checking is not performed
when a fact-index is used as the since the deftemplate being referenced is
usually ambiguous
...
External functions
may not be called
...
If the assertion of the newly modified fact causes an error, or if an identical copy of the
newly modified fact already exists in the fact-list, then the symbol FALSE is returned
...
9
...
This command allows a new fact to be created by copying most of the
fields of a source fact and then specifying the fields to be changed
...
The duplicate command is similar to the modify
command except the fact being duplicated is not retracted
...
4
...
8 or the fact-index of the desired fact (e
...
3 for the fact labeled f-3)
...
Static deftemplate checking is not performed
when a fact-index is used as the since the deftemplate being referenced is
usually ambiguous
...
External functions
may not be called
...
If the assertion of the newly duplicated fact causes an error, or if an identical copy of the
newly duplicated fact already exists in the fact-list, then the symbol FALSE is returned
...
9
...
However,
assert-string takes a single string representing a fact (expressed in either ordered or deftemplate
format ) and asserts it
...

Syntax

(assert-string )

If an identical copy of the fact already exists in the fact-list, the fact will not be added (however,
this behavior can be changed, see sections 13
...
4 and 13
...
5)
...
Note that this function takes a string
and turns it into fields
...
Global variables and
expressions can be contained within the string
...
If the assertion of the newly created fact causes an error,
or if an identical copy of the newly created fact already exists in the fact-list, then the symbol
FALSE is returned
...

CLIPS>

12
...
6 Getting the Fact-Index of a Fact-address
The fact-index function returns the fact-index (an integer) of a fact-address
...
9
...

Syntax

(fact-existp )

Example
CLIPS> (clear)
CLIPS> (defglobal ?*x* = (assert (example fact)))

CLIPS Basic Programming Guide

207

CLIPS Reference Manual
CLIPS> (facts)
f-0
(example fact)
For a total of 1 fact
...
9
...

FALSE is returned if the specified fact does not exist
...
9
...
The symbol implied is returned for an ordered fact (which has a single implied multifield
slot)
...

Syntax

(fact-slot-names )

Example

CLIPS> (clear)
CLIPS> (deftemplate foo (slot bar) (multislot yak))
CLIPS> (assert (foo (bar 1) (yak 2 3)))

CLIPS> (fact-slot-names 0)
(bar yak)
CLIPS> (assert (another a b c))

CLIPS> (fact-slot-names 1)
(implied)
CLIPS>

208

Section 12 - Actions and Functions

CLIPS Reference Manual

12
...
10 Retrieving the Slot Value of a Fact
The fact-slot-value function returns the value of the specified slot from the specified fact
...

FALSE is returned if the slot name argument is invalid or the specified fact does not exist
...
9
...
If * is specified as the
module name, then all facts are returned
...
9
...
The fact query system in CLIPS provides six functions, each of
which operate on fact-sets determined by user-defined criteria:
Function

Purpose

any-factp

Determines if one or more fact-sets satisfy a query

find-fact

Returns the first fact-set that satisfies a query

find-all-facts

Groups and returns all fact-sets which satisfy a query

do-for-fact

Performs an action for the first fact-set which satisfies a query

do-for-all-facts

Performs an action for every fact-set which satisfies a query as they are found

delayed-do-for-all-facts

Groups all fact-sets which satisfy a query and then iterates an action over this group

Explanations on how to form fact-set templates, queries and actions immediately follow, for
these definitions are common to all of the query functions
...
The following is a complete example of a fact-set query function:
Example

For all of the examples in this section, assume that the commands below have already been
entered:
Example

CLIPS>
(deftemplate girl
(slot name)
(slot sex (default
(slot age (default
CLIPS>
(deftemplate woman
(slot name)
(slot sex (default
(slot age (default
CLIPS>
(deftemplate boy

210

female))
4)))

female))
25)))

Section 12 - Actions and Functions

CLIPS Reference Manual
(slot name)
(slot sex (default male))
(slot age (default 4)))
CLIPS>
(deftemplate man
(slot name)
(slot sex (default male))
(slot age (default 25)))
CLIPS>
(deffacts PEOPLE
(man (name Man-1) (age 18))
(man (name Man-2) (age 60))
(woman (name Woman-1) (age 18))
(woman (name Woman-2) (age 60))
(woman (name Woman-3))
(boy (name Boy-1) (age 8))
(boy (name Boy-2))
(boy (name Boy-3))
(boy (name Boy-4))
(girl (name Girl-1) (age 8))
(girl (name Girl-2)))
CLIPS> (reset)
CLIPS> (facts)
f-0
(initial-fact)
f-1
(man (name Man-1) (sex male) (age 18))
f-2
(man (name Man-2) (sex male) (age 60))
f-3
(woman (name Woman-1) (sex female) (age 18))
f-4
(woman (name Woman-2) (sex female) (age 60))
f-5
(woman (name Woman-3) (sex female) (age 25))
f-6
(boy (name Boy-1) (sex male) (age 8))
f-7
(boy (name Boy-2) (sex male) (age 4))
f-8
(boy (name Boy-3) (sex male) (age 4))
f-9
(boy (name Boy-4) (sex male) (age 4))
f-10
(girl (name Girl-1) (sex female) (age 8))
f-11
(girl (name Girl-2) (sex female) (age 4))
For a total of 12 facts
...
9
...
1 Fact-set Definition
A fact-set is an ordered collection of facts
...
The template restrictions can be
different for each fact-set member
...
A fact-set template is a set of fact-set member variables and their associated template
restrictions
...
Variables may be used to specify the deftemplates for the fact-set
template, but if the constant names of the deftemplates are specified, the deftemplates must
already be defined
...


CLIPS Basic Programming Guide

211

CLIPS Reference Manual

Syntax

::= (+)

::= ( )

::=

::= +

Example
One fact-set template might be the ordered pairs of boys or men and girls or women
...
g
...

12
...
12
...
The rules are as follows:
1) When there is more than one member in a fact-set template, vary the rightmost members first
...

3) Examine facts of a deftemplate in the order that they were defined
...
9
...
1, thirty fact-sets would be generated in the
following order:
1
...

3
...

5
...

7
...

9
...

11
...

13
14
...


212

















16
...

18
...

20
...

22
...

24
...

26
...

28
...

30
...
9
...
3 Query Definition
A query is a user-defined boolean expression applied to a fact-set to determine if the fact-set
meets further user-defined restrictions
...

Syntax
::=

Example
Continuing the previous example, one query might be that the two facts in an ordered pair have
the same age
...
4
...

Syntax

:

Example
The previous example could be rewritten as:
(= ?man-or-boy:age ?woman-or-girl:age)

Since only fact-sets which satisfy a query are of interest, and the query is evaluated for all
possible fact-sets, the query should not have any side-effects
...
9
...
4 Distributed Action Definition
A distributed action is a user-defined expression evaluated for each fact-set which satisfies a
query
...

(printout t "(" ?man-or-boy:name "," ?woman-or-girl:name ")" crlf)

CLIPS Basic Programming Guide

213

CLIPS Reference Manual

12
...
12
...
If a
variable from an outer scope is not masked by a fact-set member variable, then that variable may
be referenced within the query and action
...
However, attempts to rebind fact-set member variables will generate
errors
...
Fact-set query functions can be nested
...
Attempting to
use fact-set member variables in an outer scope will generate an error
...

ERROR:
(deffunction last-fact
(?template)
(any-factp ((?fct ?template))
TRUE)
?fct
)
CLIPS>

12
...
12
...


214

Section 12 - Actions and Functions

CLIPS Reference Manual

12
...
12
...
The return function is only valid if it
is applicable in the outer scope, whereas the break function actually halts the query
...
9
...
8 Fact-set Query Functions
The fact query system in CLIPS provides six functions
...
9
...
2)
...

12
...
12
...
1 Testing if Any Fact-set Satisfies a Query
This function applies a query to each fact-set which matches the template
...

Otherwise, the return value is the symbol FALSE
...
9
...
8
...
If a fact-set satisfies
the query, then the function is immediately terminated, and the fact-set is returned in a multifield
value
...
Each field of the multifield
value is a fact-address representing a fact-set member
...

CLIPS>
(find-fact((?m man) (?w woman)) (= ?m:age ?w:age))
( )

CLIPS Basic Programming Guide

215

CLIPS Reference Manual
CLIPS>

12
...
12
...
3 Determining All Fact-sets Satisfying a Query
This function applies a query to each fact-set which matches the template
...
This multifield value is returned when the query
has been applied to all possible fact-sets
...
The first n
fields correspond to the first fact-set, and so on
...
The multifield value can consume a large amount of
memory due to permutational explosion, so this function should be used judiciously
...

CLIPS>
(find-all-facts ((?m man) (?w woman)) (= ?m:age ?w:age))
( )
CLIPS>

12
...
12
...
4 Executing an Action for the First Fact-set Satisfying a Query
This function applies a query to each fact-set which matches the template
...
The
return value is the evaluation of the action
...

Syntax

(do-for-fact *)

Example
Print out the first triplet of different people that have the same age
...

CLIPS>
(do-for-fact ((?p1 girl boy woman man)
(?p2 girl boy woman man)
(?p3 girl boy woman man))
(and (= ?p1:age ?p2:age ?p3:age)
(neq ?p1 ?p2)
(neq ?p1 ?p3)
(neq ?p2 ?p3))
(printout t ?p1:name " " ?p2:name " " ?p3:name crlf))
Girl-2 Boy-2 Boy-3
216

Section 12 - Actions and Functions

CLIPS Reference Manual
CLIPS>

12
...
12
...
5 Executing an Action for All Fact-sets Satisfying a Query
This function applies a query to each fact-set which matches the template
...
The return value is the evaluation of the action for the
last fact-set which satisfied the query
...

Syntax
(do-for-all-facts *)

Example
Print out all triplets of different people that have the same age
...
Without these
restrictions, two fact-sets which differed only in the order of their members would both satisfy
the query
...
9
...
8
...
If there are no fact-sets which satisfy the query, then
the function returns the symbol FALSE
...
The intermediary multifield value is discarded
...
This function should be
used in lieu of do-for-all-facts when the action applied to one fact-set would change the result of
the query for another fact-set (unless that is the desired effect)
...
The test in this case is another query function which
determines if there are any older boys than the one currently being examined
...

CLIPS> (watch facts)
CLIPS>
(delayed-do-for-all-facts ((?b1 boy))
(not (any-factp ((?b2 boy)) (> ?b2:age
(retract ?b1))
<== f-6
(boy (name Boy-1) (sex male)
CLIPS> (unwatch facts)
CLIPS> (reset)
CLIPS> (watch facts)
CLIPS>
(do-for-all-facts ((?b1 boy))
(not (any-factp ((?b2 boy)) (> ?b2:age
(retract ?b1))
<== f-6
(boy (name Boy-1) (sex male)
<== f-7
(boy (name Boy-2) (sex male)
<== f-8
(boy (name Boy-3) (sex male)
<== f-9
(boy (name Boy-4) (sex male)
CLIPS> (unwatch facts)
CLIPS>

?b1:age)))
(age 8))

?b1:age)))
(age
(age
(age
(age

8))
4))
4))
4))

12
...

12
...
1 Getting the List of Deffacts
The function get-deffacts-list returns a multifield value containing the names of all deffacts
constructs visible to the module specified by or to the current module if none is
specified
...

Syntax

(get-deffacts-list [])

Example
CLIPS> (clear)
CLIPS> (get-deffacts-list)
(initial-fact)
CLIPS> (deffacts foo)
CLIPS> (get-deffacts-list)
(initial-fact foo)
CLIPS>

218

Section 12 - Actions and Functions

CLIPS Reference Manual

12
...
2 Determining the Module in which a Deffacts is Defined
This function returns the module in which the specified deffacts name is defined
...
11 DEFRULE FUNCTIONS
The following functions provide ancillary capabilities for the defrule construct
...
11
...
If * is specified as the module name, then all defrules are returned
...
11
...

Syntax
(defrule-module )

12
...


CLIPS Basic Programming Guide

219

CLIPS Reference Manual

12
...
1 Getting the Current Focus
The function get-focus returns the module name of the current focus
...

Syntax

(get-focus)

Example
CLIPS>
CLIPS>
MAIN
CLIPS>
CLIPS>
CLIPS>
TRUE
CLIPS>
A
CLIPS>

(clear)
(get-focus)
(defmodule A)
(defmodule B)
(focus A B)
(get-focus)

12
...
2 Getting the Focus Stack
The function get-focus-stack returns all of the module names in the focus stack as a multifield
value
...

Syntax

(get-focus-stack)

Example
CLIPS>
CLIPS>
(MAIN)
CLIPS>
CLIPS>
()
CLIPS>
CLIPS>
CLIPS>
TRUE
CLIPS>
(A B)
CLIPS>

(clear)
(get-focus-stack)
(clear-focus-stack)
(get-focus-stack)
(defmodule A)
(defmodule B)
(focus A B)
(get-focus-stack)

12
...
3 Removing the Current Focus from the Focus Stack
The function pop-focus removes the current focus from the focus stack and returns the module
name of the current focus
...

Syntax

(pop-focus)

220

Section 12 - Actions and Functions

CLIPS Reference Manual

Example
CLIPS>
CLIPS>
MAIN
CLIPS>
MAIN
CLIPS>
CLIPS>
CLIPS>
TRUE
CLIPS>
A
B
MAIN
CLIPS>
A
CLIPS>
B
CLIPS>

(clear)
(list-focus-stack)
(pop-focus)
(defmodule A)
(defmodule B)
(focus A B)
(list-focus-stack)

(pop-focus)
(list-focus-stack)

12
...

12
...
1 Getting the List of Defglobals
The function get-defglobal-list returns a multifield value containing the names of all global
variables visible to the module specified by or to the current module if none is
specified
...

Syntax
(get-defglobal-list [])

Example

CLIPS>
CLIPS>
()
CLIPS>
CLIPS>
(x y)
CLIPS>

(clear)
(get-defglobal-list)
(defglobal ?*x* = 3 ?*y* = 5)
(get-defglobal-list)

12
...
2 Determining the Module in which a Defglobal is Defined
This function returns the module in which the specified defglobal name is defined
...
14 DEFFUNCTION FUNCTIONS
The following functions provide ancillary capabilities for the deffunction construct
...
14
...
If * is specified as the module name, then all deffunctions are
returned
...
14
...

Syntax

(deffunction-module )

12
...

12
...
1 Getting the List of Defgenerics
The function get-defgeneric-list returns a multifield value containing the names of all defgeneric
constructs that are currently defined
...
15
...

Syntax
(defgeneric-module )

12
...
3 Getting the List of Defmethods
The function get-defmethod-list returns a multifield value containing method name/indices pairs
for all defmethod constructs that are currently defined
...

Syntax

(get-defmethod-list [])

Example
CLIPS>
CLIPS>
()
CLIPS>
CLIPS>
CLIPS>
CLIPS>
CLIPS>
(foo 1
CLIPS>
(foo 1
CLIPS>

(clear)
(get-defmethod-list)
(defmethod foo ((?x STRING)))
(defmethod foo ((?x INTEGER)))
(defmethod bar ((?x STRING)))
(defmethod bar ((?x INTEGER)))
(get-defmethod-list)
foo 2 bar 1 bar 2)
(get-defmethod-list foo)
foo 2)

12
...
4 Type Determination
The function type returns a symbol which is the name of the type (or class) of its of argument
...
16
...
4), but, unlike the class
function, it is available even when COOL is not installed
...
15
...
5
...
Otherwise, the
function will return the symbol FALSE
...
15
...
15
...
5
...
Otherwise, a method execution error will occur (see section 8
...
4)
...
The shadowed method is passed the same arguments as the
calling method
...
In addition, a method may
make multiple calls to call-next-method, and the same shadowed method will be executed each
time
...
0)
"NUMBER"
CLIPS>

12
...
7 Calling Shadowed Methods with Overrides
The function override-next-method is similar to call-next-method, except that new arguments
can be provided
...
From the set of methods which are more general than the
currently executing one, the most specific method which is applicable to the new arguments is
executed
...
) A recursive call to the generic
function itself should be used in lieu of override-next-method if the most specific of all
methods for the generic function which is applicable to the new arguments should be executed
...

CLIPS> (preview-generic + 1 2)
+ #2 (INTEGER) (INTEGER)
+ #SYS1 (NUMBER) (NUMBER) ($? NUMBER)
CLIPS> (watch methods)
CLIPS> (+ 1 2)
MTH >> +:#2 ED:1 (1 2)
MTH >> +:#SYS1 ED:2 (2 6)
MTH << +:#SYS1 ED:2 (2 6)
MTH << +:#2 ED:1 (1 2)
8
CLIPS> (unwatch methods)
CLIPS>

12
...
8 Calling a Specific Method
The function call-specific-method allows the user to call a particular method of a generic
function without regards to method precedence
...
The method must be applicable to the arguments passed
...

Syntax
(call-specific-method
*)

Example
CLIPS> (clear)
CLIPS>
(defmethod + ((?a INTEGER) (?b
(* (- ?a ?b) (- ?b ?a)))
CLIPS> (list-defmethods +)
+ #2 (INTEGER) (INTEGER)
+ #SYS1 (NUMBER) (NUMBER) ($?
For a total of 2 methods
...
15
...


...


(TRUE or FALSE)



...


...


...




...


...
16 CLIPS OBJECT-ORIENTED LANGUAGE (COOL) FUNCTIONS
The following functions provide ancillary capabilities for COOL
...
16
...
16
...
1 Getting the List of Defclasses
The function get-defclass-list returns a multifield value containing the names of all defclass
constructs visible to the module specified by or to the current module if none is
specified
...

Syntax
(get-defclass-list [])

Example

CLIPS> (clear)
CLIPS> (get-defclass-list)
(FLOAT INTEGER SYMBOL STRING MULTIFIELD EXTERNAL-ADDRESS FACT-ADDRESS
ADDRESS INSTANCE-NAME OBJECT PRIMITIVE NUMBER LEXEME ADDRESS INSTANCE
INITIAL-OBJECT)
CLIPS> (defclass FOO (is-a USER))
CLIPS> (defclass BAR (is-a USER))
CLIPS> (get-defclass-list)
(FLOAT INTEGER SYMBOL STRING MULTIFIELD EXTERNAL-ADDRESS FACT-ADDRESS
ADDRESS INSTANCE-NAME OBJECT PRIMITIVE NUMBER LEXEME ADDRESS INSTANCE
INITIAL-OBJECT FOO BAR)
CLIPS>

CLIPS Basic Programming Guide

INSTANCEUSER

INSTANCEUSER

227

CLIPS Reference Manual

12
...
1
...

Syntax
(defclass-module )

12
...
1
...

Syntax

(class-existp )

12
...
1
...

Syntax
(superclassp )

12
...
1
...

Syntax
(subclassp )

12
...
1
...
If the inherit keyword is specified then the slot may be inherited, otherwise it
must be directly defined in the specified class
...
16
...
7 Testing whether a Slot is Writable
This function returns the symbol TRUE if the specified slot in the specified class is writable (see
section 9
...
3
...
Otherwise, it returns the symbol FALSE
...

Syntax
(slot-writablep )

12
...
1
...
3
...
4)
...
An error is generated if the
specified class or slot does not exist
...
16
...
9 Testing whether a Slot is Public
This function returns the symbol TRUE if the specified slot in the specified class is public (see
section 9
...
3
...
Otherwise, it returns the symbol FALSE
...

Syntax

(slot-publicp )

12
...
1
...
4
...
Otherwise, it returns the symbol FALSE
...

Syntax
(slot-direct-accessp )

12
...
1
...

Syntax
Defaults are outlined
...
16
...
12 Determining if a Class can have Direct Instances
This function returns the symbol TRUE if the specified class is abstract, i
...
the class cannot
have direct instances, FALSE otherwise
...
16
...
13 Determining if a Class can Satisfy Object Patterns
This function returns the symbol TRUE if the specified class is reactive, i
...
objects of the class
can match object patterns, FALSE otherwise
...
16
...
14 Getting the List of Superclasses for a Class
This function groups the names of the direct superclasses of a class into a multifield variable
...
A multifield of
length zero is returned if an error occurs
...
16
...
15 Getting the List of Subclasses for a Class
This function groups the names of the direct subclasses of a class into a multifield variable
...
A multifield of length
zero is returned if an error occurs
...
16
...
16 Getting the List of Slots for a Class
This function groups the names of the explicitly defined slots of a class into a multifield variable
...
A multifield of
length zero is returned if an error occurs
...
16
...
17 Getting the List of Message-Handlers for a Class
This function groups the class names, message names and message types of the
message-handlers attached direct to class into a multifield variable (implicit slot-accessors are
not included)
...
A multifield of length zero is returned if an error occurs
...
16
...
18 Getting the List of Facets for a Slot
This function returns a multifield listing the facet values for the specified slot (the slot can be
inherited or explicitly defined for the class)
...
Following is a table indicating what each field represents and its possible values:
Field
1
2
3
4
5
6
7
8
9
10

Meaning
Field Type
Default Value
Inheritance
Access
Storage
Pattern-Match
Source
Visibility
Automatic Accessors
Override-Message

Values
SGL/MLT
STC/DYN/NIL
INH/NIL
RW/R/INT
LCL/SHR
RCT/NIL
EXC/CMP
PUB/PRV
R/W/RW/NIL


Explanation
Single-field or multifield
Static, dynamic or none
Inheritable by other classes or not
Read-write, read-only or initialize-only
Local or shared
Reactive or non-reactive
Exclusive or composite
Public or private
Read, write, read-write or none
Name of message sent for slot-overrides

See section 9
...
3 for more details on slot facets
...
16
...
19 Getting the List of Source Classes for a Slot
This function groups the names of the classes which provide facets for a slot of a class into a
multifield variable
...
However, composite slots may have facets from many
different classes (see section 9
...
3
...
A multifield of length zero is returned if an error occurs
...
16
...
20 Getting the Primitive Types for a Slot
This function groups the names of the primitive types allowed for a slot into a multifield
variable
...

Syntax

(slot-types )

Example
CLIPS> (clear)
CLIPS> (defclass A (is-a USER) (slot y (type INTEGER LEXEME)))
CLIPS> (slot-types A y)
(INTEGER SYMBOL STRING)
CLIPS>

12
...
1
...
A maximum cardinality of infinity is indicated by the symbol +oo (the plus
character followed by two lowercase o’s—not zeroes)
...

Syntax

(slot-cardinality )

Example

CLIPS> (clear)
CLIPS>
(defclass A (is-a USER)
(slot x)
(multislot y (cardinality ?VARIABLE 5))
(multislot z (cardinality 3 ?VARIABLE)))
CLIPS> (slot-cardinality A x)
()
CLIPS> (slot-cardinality A y)

CLIPS Basic Programming Guide

233

CLIPS Reference Manual
(0 5)
CLIPS> (slot-cardinality A z)
(3 +oo)
CLIPS>

12
...
1
...
If no allowed-… facets were specified for the slot, then the
symbol FALSE is returned
...

Syntax

(slot-allowed-values )

Example

CLIPS> (clear)
CLIPS>
(defclass A (is-a USER)
(slot x)
(slot y (allowed-integers 2 3) (allowed-symbols foo)))
CLIPS> (slot-allowed-values A x)
FALSE
CLIPS> (slot-allowed-values A y)
(2 3 foo)
CLIPS>

12
...
1
...
A minimum value of infinity is indicated by the symbol -oo (the minus character
followed by two lowercase o’s—not zeroes)
...
The symbol FALSE
is returned for slots in which numeric values are not allowed
...

Syntax

(slot-range )

Example
CLIPS> (clear)
CLIPS>
(defclass A (is-a USER)
(slot x)
(slot y (type SYMBOL))
(slot z (range 3 10)))
CLIPS> (slot-range A x)
(-oo +oo)
CLIPS> (slot-range A y)
FALSE

234

Section 12 - Actions and Functions

CLIPS Reference Manual
CLIPS> (slot-range A z)
(3 10)
CLIPS>

12
...
1
...
If a slot has a dynamic default, the
expression will be evaluated when this function is called
...

Syntax

(slot-default-value )

Example
CLIPS> (clear)
CLIPS>
(defclass A (is-a USER)
(slot x (default 3))
(multislot y (default a b c))
(slot z (default-dynamic (gensym))))
CLIPS> (slot-default-value A x)
3
CLIPS> (slot-default-value A y)
(a b c)
CLIPS> (slot-default-value A z)
gen1
CLIPS> (slot-default-value A z)
gen2
CLIPS>

12
...
1
...
The old mode is the return
value of this function
...
By default, the class defaults mode is
convenience
...
If the class defaults mode is
conservation, then the role and reactivity of system-defined classes is unchanged for the purposes
of role and pattern-match inheritance and the default setting for the create-accessor facet of the
class’ slots is ?NONE
...
16
...
26 Getting the Defaults Mode for Classes
This function returns the current defaults mode used when classes are defined (convenience or
conservation)
...
16
...
27 Getting the Allowed Values for a Slot
This function groups the allowed classes for a slot (specified by the allowed-classes facet for the
slot) into a multifield variable
...
A multifield of length zero is returned if an error occurs
...
16
...
16
...
1 Existence of Shadowed Handlers
This function returns the symbol TRUE if there is another message-handler available for
execution, FALSE otherwise
...
5
...
If this function is
called from a primary handler and there are any shadowed primary handlers, the return value is
the symbol TRUE
...

Syntax
(next-handlerp)

236

Section 12 - Actions and Functions

CLIPS Reference Manual

12
...
2
...
Otherwise, a message execution error
(see section 9
...
4) will occur
...
The shadowed handler
is passed the same arguments as the calling handler
...
In addition, a handler may
make multiple calls to call-next-handler, and the same shadowed handler will be executed each
time
...
16
...
3 Calling Shadowed Handlers with Different Arguments
This function is identical to call-next-handler except that this function can change the
arguments passed to the shadowed handler
...
16
...
16
...
1 Getting the List of Definstances
The function get-definstances-list returns a multifield value containing the names of all
definstances constructs visible to the module specified by or to the current
module if none is specified
...

Syntax

(get-definstances-list [])

Example
CLIPS> (clear)
CLIPS> (get-definstances-list)
()
CLIPS> (definstances foo)
CLIPS> (definstances bar)
CLIPS> (get-definstances-list)
(foo bar)
CLIPS>

12
...
3
...

Syntax

(definstances-module )

238

Section 12 - Actions and Functions

CLIPS Reference Manual

12
...
4 Instance Manipulation Functions and Actions

12
...
4
...
4
...
1)
...
6
...
This function should never be called directly unless an init message-handler is
being defined such that the one attached to USER will never be called
...
A user-defined class which does
not inherit indirectly or directly from the class USER will require an init message-handler which
calls this function in order for instances of the class to be created
...
Otherwise, this function will return the symbol FALSE
...
16
...
2 Deleting an Instance
This function deletes the specified instances by sending them a delete message
...
The instance specified by the arguments must exist (except in the case of
“*”)
...
This function returns the symbol TRUE if all instances were
successfully deleted, otherwise it returns the symbol FALSE
...

Syntax

(unmake-instance +)

12
...
4
...
4
...
1) for a message, and
thus can only be called from within the body of a message-handler
...
4
...
2)
...


CLIPS Basic Programming Guide

239

CLIPS Reference Manual

Syntax
(delete-instance)

12
...
4
...
It returns the
symbol FALSE on errors
...
15
...

Syntax
(class )

Example
CLIPS> (class 34)
INTEGER
CLIPS>

12
...
4
...
It returns the symbol
FALSE on errors
...

Syntax

(instance-name )

12
...
4
...
It returns the symbol FALSE on
errors
...
If or * is not specified, the function searches only in the current
module
...
If
is specified, only that module is searched
...

Syntax
(instance-address [ | *] )

12
...
4
...
It returns the
symbol FALSE on errors
...
16
...
8 Converting an Instance-Name to a Symbol
This function returns a symbol which is equivalent to its instance-name argument
...

Syntax

(instance-name-to-symbol )

Example
CLIPS> (instance-name-to-symbol [a])
a
CLIPS>

12
...
4
...
16
...
9
...
Otherwise, it returns the symbol FALSE
...
16
...
9
...

Otherwise, it returns the symbol FALSE
...
16
...
9
...

Otherwise, it returns the symbol FALSE
...
16
...
9
...
Otherwise, it returns the
symbol FALSE
...
If the argument is an instance-address, the function determines if the
specified address is still valid
...
16
...
10 Reading a Slot Value
This function returns the value of the specified slot of the active instance (see section 9
...
1
...
If
the slot does not exist, the slot does not have a value or this function is called from outside a
message-handler, this function will return the symbol FALSE and an error will be generated
...
Thus it is possible to access different slots every time the function is
executed (see section 9
...
2 for more detail)
...

Syntax

(dynamic-get )

12
...
4
...
4
...
1)
...
Otherwise, the new slot value is returned
...
Thus it is possible to access different slots every time the function is executed (see section
9
...
2 for more detail)
...

Syntax
(dynamic-put *)

12
...
4
...
There are three types
of functions: replacing a range of fields with one or more new values, inserting one or more new
values at an arbitrary point, and deleting a range of fields
...
3
...
9), and an internal interface that can only be called from
message-handlers which sets the slot for the active instance (see section 9
...
1
...
Both
forms read the original value of the slot directly without the use of a get- message
...

12
...
4
...
1 Replacing Fields
Allows the replacement of a range of fields in a multifield slot value with one or more new
values
...
n, where n is the number of fields in the multifield
slot’s original value and n > 0
...
16
...
12
...
The index must greater than or equal to 1
...
Any value greater than the length of the slot’s value appends the
new values to the end of the slot’s value
...
16
...
12
...
The range indices must be from
1
...

External Interface Syntax

(slot-delete$
)

Internal Interface Syntax

(slot-direct-delete$ )

Example
CLIPS> (initialize-instance a)
[a]
CLIPS> (slot-delete$ a mfs 2 4)
(a e)
CLIPS>

12
...

12
...
1 Getting the List of Defmodules
The function get-defmodule-list returns a multifield value containing the names of all
defmodules that are currently defined
...
17
...
It returns the name of the previous current module
...

Syntax
(set-current-module )

12
...
3 Getting the Current Module
This function returns the name of the current module
...
18 SEQUENCE EXPANSION
In the past, there has been no distinction between single-field and multifield variable references
within function calls (as opposed to declaring variables for function parameters or variables used
for pattern-matching)
...
1 of CLIPS
...
The $ acts as a
“sequence expansion” operator and has special meaning when applied to a global or local
variable reference within the argument list of a function call
...

For example, using sequence expansion with the expansion rule would give the following output:

CLIPS Basic Programming Guide

245

CLIPS Reference Manual
CLIPS> (assert (foo a b c))

CLIPS> (run)
(a b c)
abc
CLIPS>

Using sequence expansion, the two printout statements on the RHS of the expansion rule are
equivalent to:
(printout t (create$ a b c) crlf)
(printout t a b c crlf)

The $ operator also works with global variables
...
Consider
the ease now of defining a general addition function for strings
...
This allows previously existing CLIPS programs to
work correctly with version 6
...
The behavior can be enabled using the
set-sequence-operator-recognition function described in section 12
...
3
...

12
...
1 Sequence Expansion and Rules
Sequence expansion is allowed on the LHS of rules, but only within function calls
...
For example, the following rule is not
allowed
(defrule bad-rule-1
(pattern $?x ?x $?x)
=>)

The following rules illustrate appropriate use of sequence expansion on the LHS of rules
...
Sequence expansion is not used to pass ?x and ?y to the length$
function since the length$ function expects a single argument of type multifield
...
Sequence expansion
is used for these function calls since the + function expects two or more arguments with numeric
data values
...

12
...
2 Multifield Expansion Function
The $ operator is merely a shorthand notation for the expand$ function call
...

Syntax
(expand$ )

The expand$ function is valid only within the argument list of a function call
...

12
...
3 Setting The Sequence Operator Recognition Behavior
This function sets the sequence operator recognition behavior
...

When this behaviour is enabled, multifield variables are expanded and passed as separate
arguments in the function call
...
e
...
The return value for this function is the old
value for the behavior
...
18
...

Syntax
(get-sequence-operator-recognition)

12
...
5 Sequence Operator Caveat
CLIPS normally tries to detect as many constraint errors as possible for a function call at parse
time, such as bad number of arguments or types
...
) For example:
CLIPS> (deffunction foo (?a ?b))
CLIPS> (deffunction bar ($?a) (foo ?a))
ERROR: Function foo expected exactly 2 argument(s)
ERROR:
(deffunction bar
($?a)
(foo ?a)
CLIPS> (deffunction bar ($?a) (foo $?a))
CLIPS> (bar 1)
ERROR: Function foo expected exactly 2 argument(s)
FALSE
CLIPS> (bar 1 2)
FALSE
CLIPS>

248

Section 12 - Actions and Functions

CLIPS Reference Manual

Section 13 - Commands
This section describes commands primarily intended for use from the top-level command
prompt
...

13
...

13
...
1 Loading Constructs From A File
Loads the constructs stored in the file specified by into the environment
...
2), then an informational message (including
the type and name of the construct) will be displayed for each construct loaded
...
This function returns TRUE if the file was successfully
loaded, otherwise FALSE is returned
...
1
...
Error messages are still printed if errors are encountered while loading the file
...

Syntax

(load* )

13
...
3 Saving All Constructs To A File
Saves all of the constructs (defrules, deffacts, deftemplates, etc
...
Note that deffunctions and generic functions are saved twice to
the file
...
This

CLIPS Basic Programming Guide

249

CLIPS Reference Manual

function returns TRUE if the file was successfully saved, otherwise FALSE is returned
...
If pretty-printing has been disabled by the
conserve-mem command, then the save command will have no output
...
1
...
The
specified file must have been created by bsave
...
A bload clears all constructs from the current CLIPS
environment (as well as all facts and instances)
...
g
...
The only
constructive/destructive operation that can occur after a bload is the clear command or the bload
command (which clears the current binary image)
...
In order to add constructs to a binary image, the original
ASCII text file must be reloaded, the new constructs added, and then another bsave must be
performed
...

Binary images can be loaded into different compile-time configurations of CLIPS, as long as the
same version of CLIPS is used and all the functions and constructs needed by the binary image
are supported
...
g
...
However, it is NOT recommended that this be attempted
...
1
...
The
save file is written using a binary format which results in faster load time
...
A bsave may be performed at any time (except when a bload is
in effect)
...
In addition, constraint information associated with constructs is not saved to the binary
image
unless
dynamic
constraint
checking
is
enabled
(using
the
set-dynamic-constraint-checking command)
...


250

Section 13 - Commands

CLIPS Reference Manual

Syntax
(bsave )

13
...
6 Clearing CLIPS
Clears CLIPS
...
A clear may be performed safely at any time, however,
certain constructs will not allow themselves to be deleted while they are in use
...
Note that the clear command does not effect many environment
characteristics (such as the current conflict resolution strategy)
...

Syntax

(clear)

13
...
7 Exiting CLIPS
Quits CLIPS
...

Syntax

(exit [])

The optional argument allows the exit status code to be specified which is
eventually passed to the C exit function
...
1
...
Removes all activations from the agenda, all facts from the fact-list and all
instances of user-defined classes, then assigns global variables their initial values, asserts all
facts listed in deffacts statements into the fact-list, creates all instances listed in definstances
statements, sets the current module to the MAIN module and automatically focuses on the same
module
...
This means that rules can be activated from
facts that were asserted before the rule was defined without performing a reset
...
Note that the reset command does not effect many
environment characteristics (such as the current conflict resolution strategy)
...

Syntax
(reset)

CLIPS Basic Programming Guide

251

CLIPS Reference Manual

13
...
9 Executing Commands From a File
Allows “batch” processing of CLIPS interactive commands by replacing standard input with the
contents of a file
...
The load command should be used
in batch files rather than defining constructs directly
...
The batch command, however,
moves on until it finds the next construct or command (and in the case of a construct this is
likely to generate more errors as the remaining commands and functions in the construct are
parsed)
...
Note that the batch command operates by replacing standard input rather
than by immediately executing the commands found in the batch file
...

Syntax

(batch )

13
...
10 Executing Commands From a File Without Replacing Standard Input
Evaluates the series of commands stored in the file specified by
...
The
batch* command does not replace standard input and thus a batch* file cannot be used to
provide input to functions such as read and readline
...

The batch* command is not available for binary-load only or run-time CLIPS configurations
(see the Advanced Programming Guide)
...
1
...
This function has no
return value
...
1
...
It is patterned after the system
function provided to C on most UNIX systems
...

Syntax

(system *)

Example
(defrule print-directory
(print-directory ?directory)
=>
(system "dir " ?directory));

Note space => "dir"

Note that any spaces needed for a proper parsing of the system command must be added by the
user in the call to system
...
g
...

Portability Note
Not all operating systems/compilers provide this function
...
c file,
and the default coding for generic CLIPS is a nonfunctional stub that will compile on any
machine
...
In such a case, the
command will not be executed and the system command will return with no action taken
...
1
...
When this behavior is enabled (TRUE by
default) the dividend of the division function is automatically converted to a floating point
number
...

Syntax
(set-auto-float-dividend )

13
...
14 Getting The Auto-Float Dividend Behavior
This function returns the current value of the auto-float dividend behavior (TRUE or FALSE)
...
1
...
When this behavior is disabled
(FALSE by default), newly created data objects (such as deftemplate facts and instances) do not
have their slot values checked for constraint violations
...
The return value for this function is the old
value for the behavior
...

Syntax

(set-dynamic-constraint-checking )

13
...
16 Getting the Dynamic Constraint Checking Behavior
This function returns the current value of the dynamic constraint checking behavior (TRUE or
FALSE)
...
1
...
When this behavior is disabled (FALSE),
constraint violations are not checked when function calls and constructs are parsed
...
The return value for this function is the old value for the behavior
...
1
...

Syntax
(get-static-constraint-checking)

13
...
19 Finding Symbols
This command displays all symbols currently defined in CLIPS which contain a specified
substring
...


254

Section 13 - Commands

CLIPS Reference Manual

Syntax
(apropos )

Example

CLIPS> (apropos pen)
dependents
mv-append
open
dependencies
CLIPS>

13
...

13
...
1 Generating Trace Files
Sends all information normally sent to the logical names wclips, wdialog, wdisplay, werror,
wwarning, wtrace, and stdout to as well as to their normal destination
...
This function returns TRUE if the dribble file
was successfully opened, otherwise FALSE is returned
...
2
...
This function returns TRUE if the dribble file
was successfully closed, otherwise FALSE is returned
...
2
...

Syntax

(watch )
::= all |
compilations |
statistics |
focus |

CLIPS Basic Programming Guide

255

CLIPS Reference Manual
messages |
deffunctions * |
globals * |
rules * |
activations * |
facts * |
instances * |
slots * |
message-handlers *
[]) |
generic-functions * |
methods * []
::=

::=
[ []]
::=
::= []

If compilations are watched, the progress of construct definitions will be displayed
...
Optionally, facts
associated with individual deftemplates can be watched by specifying one or more deftemplate
names
...
If activations are watched, all rule
activations and deactivations will be displayed
...
If statistics
are watched, timing information along with other information (average number of facts, average
number of activations, etc
...
Note that the number of rules fired and
timing information is not printed unless this item is being watch
...

If globals are watched, variable assignments to globals variables will be displayed
...
If deffunctions are watched, the start and finish of deffunctions will be
displayed
...

If generic-functions are watched, the start and finish of generic functions will be displayed
...
If methods are watched, the start and finish of
individual methods within a generic function will be displayed
...

When the method index is not specified, then all methods of the specified defgeneric will be
watched
...
If slots are
watched, changes to any instance slot values will be displayed
...
If message-handlers are watched, the start and finish of individual
message-handlers within a message will be displayed
...
When the message-handler name and
message-handler type are not specified, then all message-handlers for the specified class will be
watched
...
If messages are
watched, the start and finish of messages will be displayed
...
If all constructs associated with a watch item are
being watched, then newly defined constructs of the same type will also be watched
...
If all is watched, then all other watch items will be
watched
...
The watch function has no return value
...
2
...

Syntax
(unwatch )

This command is identical to the watch command with the exception that it disables watch items
rather than enabling them
...

Example
CLIPS> (unwatch all)
CLIPS>

13
...
5 Viewing the Current State of Watch Items
This command displays the current state of watch items
...
If called without the
argument, the global watch state of all watch items is displayed
...
This function has no return
value
...
3 DEFTEMPLATE COMMANDS
The following commands manipulate deftemplates
...
3
...
This function has no return value
...
3
...
This function has no return value
...
If is specified, then the names of all deftemplates in the specified
258

Section 13 - Commands

CLIPS Reference Manual

module are displayed
...

13
...
3 Deleting a Deftemplate
This function deletes a previously defined deftemplate
...

Otherwise, no further uses of the deleted deftemplate are permitted (unless redefined)
...
This function has no return value
...
4 FACT COMMANDS
The following commands display information about facts
...
4
...

Syntax
(facts []
[
[
[]]])

If is not specified, then only facts visible to the current module will be
displayed
...
If the symbol * is used for , then facts from any module may be
displayed
...
If the end argument is specified, only facts with fact-indices less
than or equal to this argument are displayed
...
This function has
no return value
...
4
...
It can read files
created with save-facts or any ASCII text file
...
Facts may span across lines and can be written in either ordered or
deftemplate format
...

Syntax

(load-facts )

13
...
3 Saving The Fact-List To A File
This function saves all of the facts in the current fact-list into the file specified by
...
Instance-address fields are
converted to instance-names
...
If
is the symbol visible, then all facts visible to the current module are saved
...
If is not specified, it defaults to local
...
In this event, only those
facts with associated with a corresponding deftemplate in the specified list will be saved
...

Syntax
(save-facts [ *])
::= visible | local

13
...
4 Setting the Duplication Behavior of Facts
This function sets fact duplication behavior
...
When enabled (TRUE),
the duplicate fact is asserted with a new fact-index
...

Syntax
(set-fact-duplication )

Example
CLIPS> (get-fact-duplication)
FALSE
CLIPS> (watch all)
CLIPS> (assert (a))
==> f-0
(a)

CLIPS> (assert (a))
FALSE
CLIPS> (set-fact-duplication TRUE)
FALSE
CLIPS> (assert (a))
==> f-1
(a)
260

Section 13 - Commands

CLIPS Reference Manual

CLIPS>

13
...
5 Getting the Duplication Behavior of Facts
This function returns the current value of the fact duplication behavior (TRUE or FALSE)
...
4
...
Optionally the logical
name to which output is sent can be specified and slots containing their default values can be
excluded from the output
...
If is
FALSE or unspecified, then all of the fact’s slots are displayed, otherwise slots with static
defaults are only displayed if their current slot value differs from their initial default value
...
5 DEFFACTS COMMANDS
The following commands manipulate deffacts
...
5
...
This function has no return value
...
5
...

Syntax

(list-deffacts [])

If is unspecified, then the names of all deffacts in the current module are
displayed
...
If is the symbol *, then the names of all deffacts in all modules
are displayed
...

13
...
3 Deleting a Deffacts
This function deletes a previously defined deffacts
...
If the
symbol * is used for , then all deffacts will be deleted (unless there exists a
deffacts named *)
...

Exceptions: When deffacts are being reset as part of the reset command, they cannot be
removed
...

Important Note
Although the initial-fact deffacts automatically created by CLIPS can be deleted, in practice it
never should be since many conditional elements rely on the existence of the initial-fact fact for
correct operation
...


262

Section 13 - Commands

CLIPS Reference Manual

13
...

13
...
1 Displaying the Text of a Rule
Displays the text of a given rule
...
This function has no return value
...
6
...

Syntax

(list-defrules [])

If is unspecified, then the names of all defrules in the current module are
displayed
...
If is the symbol *, then the names of all defrules in all modules
are displayed
...

13
...
3 Deleting a Defrule
This function deletes a previously defined defrule
...
If the symbol * is
used for , then all defrule will be deleted (unless there is a defrule named *)
...

13
...
4 Displaying Matches for a Rule
For a specified rule, displays the list of the facts or instances which match each pattern in the
rule’s LHS, the partial matches for the rule, and the activations for the rule
...
4
...
When listed as a partial match, the not, exists, and forall CEs are shown as a

CLIPS Basic Programming Guide

263

CLIPS Reference Manual

comma with no following pattern entity identifier (such as a fact-index or instance name)
...
This function has no return value
...
Fact f-1 matches
the first pattern, facts f-2 and f-3 match the the second pattern, and fact f-4 matches the third
pattern
...

CLIPS> (clear)
CLIPS>
(defrule matches-example-1
(a ?)
(b ?)
(c ?)
=>)
CLIPS> (reset)
CLIPS> (assert (a 1) (b 1) (b 2) (c 1))

CLIPS> (facts)
f-0
(initial-fact)
f-1
(a 1)
f-2
(b 1)
f-3
(b 2)
f-4
(c 1)
For a total of 5 facts
...
The initial-fact, f-0, matches the first pattern,
there are no matches for the second pattern (since there are no d facts), facts f-2 and f-3 match
the third pattern, and fact f-4 matches the forth pattern
...
There are two partial matches which satisfy the first two patterns and two
partial matches which satisfy all three patterns
...

264

Section 13 - Commands

CLIPS Reference Manual
CLIPS> (matches matches-example-1)
Matches for Pattern 1
f-1
Matches for Pattern 2
f-2
f-3
Matches for Pattern 3
f-4
Partial matches for CEs 1 - 2
f-1,f-3
f-1,f-2
Partial matches for CEs 1 - 3
f-1,f-2,f-4
f-1,f-3,f-4
Activations
None
CLIPS>

Listing the matches for the rule matches-example-2 displays the matches for the patterns
indicated previously
...
The match for the second CE is indicated by the comma followed
by no additional pattern entity identifier
...
Again, the match for the
third CE is indicated by a comma followed by no additional pattern entity identifier
...
The list of activations will always be
a subset of the partial matches for all of the rule’s CEs
...
6
...

Syntax
(set-break )

CLIPS Basic Programming Guide

265

CLIPS Reference Manual

If a breakpoint is set for a given rule, execution will stop prior to executing that rule
...
This function has no return value
...
6
...

Syntax

(remove-break [])

If no argument is given, then all breakpoints are removed
...

13
...
7 Displaying Rule Breakpoints
This command displays all the rules which have breakpoints set
...

Syntax

(show-breaks [])

If is unspecified, then the names of all rules having breakpoints in the current
module are displayed
...
If is the symbol *, then the
names of all rules having breakpoints in all modules are displayed
...
6
...
This function has no return value
...
6
...
When this behavior is enabled (TRUE by
default), newly defined rules are updated based upon the current state of the fact-list
...

In order to prevent rules from obtaining an inconsistent state, the incremental reset behavior can
only be changed when there are no rules currently defined
...


266

Section 13 - Commands

CLIPS Reference Manual

Syntax
(set-incremental-reset )

13
...
10 Getting the Incremental Reset Behavior
This function returns the current value of the incremental reset behavior (TRUE or FALSE)
...
6
...
This function has no return value
...
4
...
8, the fact-index of the desired fact (e
...
3 for the
fact labeled f-3), or the instance-name (e
...
[object])
...
6
...
This function has no return value
...
4
...
8, the fact-index of the desired fact (e
...
3 for the
fact labeled f-3), or the instance-name (e
...
[object])
...
7 AGENDA COMMANDS
The following commands manipulate agenda
...
7
...
This function has no return value
...
If is specified, then all activations on the agenda of the
specified module are displayed
...

13
...
2 Running CLIPS
Starts execution of the rules
...
If there are
no arguments or the first argument is a negative integer, execution will cease when the agenda
contains no rule activations
...
The run command has no additional effect if evaluated while rules
are executing
...
2)
...
This function has no return value
...
7
...
The specified modules are pushed onto the
focus stack in the reverse order they are listed
...
The current focus is the top module of the focus stack
...
Note
that the current focus is different from the current module
...
Setting the current module
with the set-current-module function changes it without remembering the old module
...
This function returns a boolean value: FALSE if an error occurs, otherwise
TRUE
...
7
...
It is called
without arguments
...
The agenda
is left intact, and execution may be continued with a run command
...

Syntax
(halt)

13
...
5 Setting The Current Conflict Resolution Strategy
This function sets the current conflict resolution strategy
...

Syntax
(set-strategy )

where is either depth, breadth, simplicity, complexity, lex, mea, or random
...
The agenda will be reordered to reflect the new conflict
resolution strategy
...
7
...

Syntax
(get-strategy)

13
...
7 Listing the Module Names on the Focus Stack
The command list-focus-stack list all module names on the focus stack
...

Syntax
(list-focus-stack)

CLIPS Basic Programming Guide

269

CLIPS Reference Manual

13
...
8 Removing all Module Names from the Focus Stack
The command clear-focus-stack removes all module names from the focus stack
...
7
...
By default, salience values are only
evaluated when a rule is defined
...
The return value for this
function is the old value for salience evaluation
...
The value when-activation forces salience evaluation at
the time of rule definition and upon being activated
...

13
...
10 Getting the Salience Evaluation Behavior
This function returns the current salience evaluation behavior (when-defined, when-activated, or
every-cycle)
...
7
...
This function has no return value
...
If
is specified, then the agenda in the specified module is refreshed
...


270

Section 13 - Commands

CLIPS Reference Manual

13
...

13
...
1 Displaying the Text of a Defglobal
Displays the text required to define a given global variable
...
The variable name passed to ppdefglobal should not include the question mark or the
asterisks (e
...
x is the variable name for the global variable ?*x*)
...

Syntax
(ppdefglobal )

13
...
2 Displaying the List of Defglobals
Displays the names of all defglobals
...

Syntax

(list-defglobals [])

If is unspecified, then the names of all defglobals in the current module are
displayed
...
If is the symbol *, then the names of all defglobals in all
modules are displayed
...
8
...

Syntax
(undefglobal )

If the defglobal is in use (for example if it is referred to in a deffunction), then the deletion will
fail
...
If the
symbol * is used for , then all defglobals will be deleted (unless there is a
defglobal named *)
...

13
...
4 Displaying the Values of Global Variables
Displays the names and current values of all defglobals
...


CLIPS Basic Programming Guide

271

CLIPS Reference Manual

Syntax
(show-defglobals [])

If is unspecified, then the names and values of all defglobals in the current
module are displayed
...
If is the symbol *, then the
names and values of all defglobals in all modules are displayed
...
8
...
When this behavior is enabled (TRUE by
default) global variables are reset to their original values when the reset command is performed
...

Syntax
(set-reset-globals )

13
...
6 Getting the Reset Behavior of Global Variables
This function returns the current value of the reset global variables behavior (TRUE or FALSE)
...
9 DEFFUNCTION COMMANDS
The following commands manipulate deffunctions
...
9
...
This function has no return value
...
9
...
This function has no
return value
...
9
...

Syntax
(undeffunction )

If the symbol * is used for , then all deffunctions will be deleted (unless
there exists a deffunction called *)
...
Exceptions: A deffunction may not be deleted when it is executing or
when there is still a reference to it in another loaded construct, such as a rule RHS
...

13
...

13
...
1 Displaying the Text of a Generic Function Header
Displays the text of a given generic function header
...

Syntax

(ppdefgeneric )

13
...
2 Displaying the Text of a Generic Function Method
Displays the text of a given method
...
4
...
This function has no return value
...
10
...

Syntax
(list-defgenerics [])

If is unspecified, then the names of all defgenerics in the current module are
displayed
...
If is the symbol *, then the names of all defgenerics in all
modules are displayed
...

13
...
4 Displaying the List of Methods for a Generic Function
If no name is given, this function lists all generic function methods in the CLIPS environment
...
The methods
are listed in decreasing order of precedence (see section 8
...
2) for each generic function
...
This function has no return value
...
10
...

Syntax
(undefgeneric )

If the symbol * is used for , then all generic functions will be deleted
(unless there exists a generic function called *)
...
The undefgeneric command can be used to remove generic
functions at any time
...
This function has no return value
...
10
...

Syntax

(undefmethod )

where is the index of the method to be deleted for the generic function
...
(This is
different from the undefgeneric command because the header is not removed
...
This function removes the specified method for a generic
function, but even if the method removed is the last one, the generic function header is not
removed
...
Exceptions: A
method may not be deleted when it or any of the other methods for the same generic function are
executing
...

274

Section 13 - Commands

CLIPS Reference Manual

13
...
7 Previewing a Generic Function Call
This debugging function lists all applicable methods for a particular generic function call in order
of decreasing precedence (see section 8
...
2)
...

Syntax
(preview-generic *)

This function does not actually execute any of the methods, but any side-effects of evaluating the
generic function arguments and any query parameter restrictions (see section 8
...
3) in methods
do occur
...
5
...
11 CLIPS OBJECT-ORIENTED LANGUAGE (COOL) COMMANDS
The following commands manipulate elements of COOL
...
11
...

13
...
1
...
This function has no return value
...
11
...
2 Displaying the List of Defclasses
Displays the names of all defclasses stored in the CLIPS environment
...
If
is specified, then the names of all defclasses in the specified module are
displayed
...
This function has no return value
...
11
...
3 Deleting a Defclass
This function deletes a previously defined defclass and all its subclasses from the CLIPS
environment
...
The undefclass command can be used to remove defclasses at any time
...
This function has no return
value
...
11
...
4 Examining a Class
This function provides a verbose description of a class including: abstract role (whether direct
instances can be created or not), direct superclasses and subclasses, class precedence list, slots
with all their facets and sources, and all recognized message-handlers
...

Syntax

(describe-class )

Example
CLIPS>
(defclass CHILD (is-a USER)
(role abstract)
(multislot parents (cardinality 2 2))
(slot age (type INTEGER)
(range 0 18))
(slot sex (access read-only)
(type SYMBOL)
(allowed-symbols male female)
(storage shared)))

276

Section 13 - Commands

CLIPS Reference Manual
CLIPS>
(defclass BOY (is-a CHILD)
(slot sex (source composite)
(default male)))
CLIPS>
(defmessage-handler BOY play ()
(printout t "The boy is now playing
...

Direct Superclasses: USER
Inheritance Precedence: CHILD USER OBJECT
Direct Subclasses: BOY
-------------------------------------------------------------------SLOTS : FLD DEF PRP ACC STO MCH SRC VIS CRT OVRD-MSG
SOURCE(S)
parents : MLT STC INH RW LCL RCT EXC PRV NIL put-parents CHILD
age
: SGL STC INH RW LCL RCT EXC PRV NIL put-age
CHILD
sex
: SGL STC INH R SHR RCT EXC PRV NIL NIL
CHILD
Constraint information for slots:
SLOTS : SYM STR INN INA EXA FTA INT FLT
parents : + + + + + + + + RNG:[-oo
...
2]
age
:
+
RNG:[0
...

MSG
SOURCE(S) + Source of slot (more than one class for composite)
In the constraint information summary for the slots, each of the columns shows one of the
primitive data types
...

A # in the column means that some values of that type are allowed in the slot
...
The following table
explains the abbreviations used in the constraint information summary for the slots:
Abbreviation
SYM
STR
INN
INA
EXA
FTA
INT
FLT
RNG
CRD

Explanation
Symbol
String
Instance Name
Instance Address
External Address
Fact Address
Integer
Float
Range
Cardinality

13
...
1
...
Indentation indicates a subclass
...
Asterisks mark classes which are direct subclasses of more than one
class
...
This function has no
return value
...
11
...

13
...
2
...
This function has no return value
...

(ppdefmessage-handler
[])
::= around | before | primary | after

13
...
2
...
With one argument, this
function lists all handlers for the specified class
...
This function has no return value
...

CLIPS> (defclass A (is-a USER))
CLIPS> (defmessage-handler A foo ())
CLIPS> (list-defmessage-handlers A)
foo primary in class A
...

CLIPS> (list-defmessage-handlers A inherit)
init primary in class USER
...

create primary in class USER
...

foo primary in class A
...

CLIPS>

13
...
2
...

Syntax
Defaults are outlined
...
(Wildcards will not work
for the class name or handler name if there is a class or handler called *
...
Exceptions: A
handler may not be deleted when it or any of the other handlers for the same class are executing
...

Example
Delete all primary handlers in the system
...
11
...
4 Previewing a Message
Displays a list of all the applicable message-handlers for a message sent to an instance of a
particular class
...
The right double-angle brackets indicate the beginning of handler execution,
and the left double-angle brackets indicate the end of handler execution
...

Syntax
(preview-send )

Example
For the example in section 9
...
3, the output would be:
CLIPS> (preview-send USER my-message)
>> my-message around in class USER
| >> my-message around in class OBJECT
| | >> my-message before in class USER
| | << my-message before in class USER
| | >> my-message before in class OBJECT
| | << my-message before in class OBJECT
| | >> my-message primary in class USER
| | | >> my-message primary in class OBJECT
| | | << my-message primary in class OBJECT
| | << my-message primary in class USER
| | >> my-message after in class OBJECT
| | << my-message after in class OBJECT
| | >> my-message after in class USER
| | << my-message after in class USER
| << my-message around in class OBJECT
<< my-message around in class USER
CLIPS>

13
...
3 Definstances Commands
The following commands manipulate definstances
...
11
...
1 Displaying the Text of a Definstances
Displays the text of a given definstances
...

Syntax

(ppdefinstances )

13
...
3
...
This function has no
return value
...
11
...
3 Deleting a Definstances
This function deletes a previously defined definstances
...
The undefinstances command can be used to remove
definstances at any time
...
This function has no return value
...
Similarly, the initial-object instance created by the
initial-object definstances when a reset command is issued, should never be deleted by a
program
...
11
...

13
...
4
...
If a module
name is given, all instances within the scope of that module are given
...
If a class
name is specified, only the instances for the named class are listed
...
This function has no return value
...
11
...
2 Printing an Instance’s Slots from a Handler
This function operates implicitly on the active instance (see section 9
...
1
...
This function directly prints
the slots of the active instance and is the one used to implement the print handler attached to
class USER (see section 9
...
4
...
This function has no return value
...
11
...
3 Saving Instances to a Text File
This function saves all instances in the CLIPS environment to the specified file in the following
format:
( of *)
::= ( *)

A slot-override is generated for every slot of every instance, regardless of whether the slot
currently holds a default value or not
...
Instance-address slot values are saved as instance-names
...

Syntax
(save-instances
[local | visible [[inherit] +])

By default, save-instances saves only the instances of all defclasses in the current module
...
Also,
particular classes may be specified for saving, but they must be in scope according to the local or
visible option
...
Subclasses
must still be in local or visible scope in order for their instances to be saved
...
At least one class is required for the
inherit option
...

save-instances does not preserve module information, so the instance file should be loaded into
the module which was current when it was saved
...
11
...
4 Saving Instances to a Binary File
The function bsave-instances works exactly like save-instances except that the instances are
saved in a binary format which can only be loaded with the function bload-instances
...
The disadvantage is that the file is not usually portable
to other platforms
...
11
...
5 Loading Instances from a Text File
This function loads instances from a file into the CLIPS environment
...
Each instance should be in the format described in
section 13
...
4
...
Calling load-instances is
exactly equivalent to a series of make-instance calls (in CLIPS version 5
...
This function
returns the number of instances loaded or -1 if it could not access the instance file
...
11
...
6 Loading Instances from a Text File without Message Passing
The function restore-instances loads instances from a file into the CLIPS environment
...
Each instance should be in the
format described in section 13
...
4
...
It is
similar in operation to load-instances, however, unlike load-instances, restore-instances does not
use message-passing for deletions, initialization, or slot-overrides
...
This function returns the number of instances loaded or -1 if it could not
access the instance file
...
11
...
7 Loading Instances from a Binary File
This function is similar to restore-instances except that it can only work with files generated by
bsave-instances
...
11
...
4 for a discussion of the merits of using binary instance
files
...
12 DEFMODULE COMMANDS
The following commands manipulate defmodule constructs
...
12
...
This function has no return value
...
12
...
This function
has no return value
...
13 MEMORY MANAGEMENT COMMANDS
The following commands display CLIPS memory status information
...

13
...
1 Determining the Amount of Memory Used by CLIPS
Returns an integer representing the number of bytes CLIPS has currently in-use or has held for
later use
...

Syntax

(mem-used)

13
...
2 Determining the Number of Memory Requests Made by CLIPS
Returns an integer representing the number of times CLIPS has requested memory from the
operating system
...
13
...
CLIPS will
automatically call this function if it is running low on memory to allow the operating system to
coalesce smaller memory blocks into larger ones
...
This function returns
an integer representing the amount of memory freed to the operating system
...
13
...
This can
save considerable memory in a large system
...

This function has no return value
...

13
...
The help system uses
CLIPS’ external text manipulation capabilities (see section 13
...
Thus, it is possible to add or
change entries in the help file or to construct new help files with information specific to the
user’s system
...
14
...
It then references
the help file for that information
...

Syntax
(help [])

286

Section 13 - Commands

CLIPS Reference Manual

where is the full path leading to a topic in the help tree
...
The help function has no
return value
...
In addition, the entire name of a field does not need to be specified
...
For instance, (help con def) would be
sufficient for the above example
...

^
?

Branch up one level
...

Giving no topic field will branch up one level
...

By default, the help facility comes up in the MAIN topic root menu and the user may make a
choice as described above
...
The
help facility will branch through the help-tree until instructed to exit by a branch-up from the top
level
...

The first call to the help facility will take longer than successive calls while the system loads
help information into an internal lookup table
...

13
...
2 Finding the Help File
The help facility reads help information from a file during execution
...
The help-path function
was provided to allow this
...
If an
argument is specified, the help facility will use the new file name for future help references
during this CLIPS session
...
h file, then CLIPS must be recompiled
...


CLIPS Basic Programming Guide

287

CLIPS Reference Manual

13
...
Each file contains a set of text entries in a special format that CLIPS can later
reference and display
...

13
...
1 External Text File Format
Each external text file to be loaded into CLIPS must be described in a particular way
...

Syntax

BEGIN-ENTRY-
•
•
Topic information in form to be displayed when referenced
...
Embedded white space between the fields of the delimiters is allowed
...

The lower the number, the closer to the root level the topic is; i
...
, the lowest level number
indicates the root level
...
Thus, the tree must be entered in the
file sequentially; i
...
, a topic with all its subtopics must be described before going on to a topic at
the same level
...
The current
topic then will be attached as a subtopic at that level
...
Level number and order of entry in a file can indicate the order of precedence in which a
list of subtopics that are all children of the same topic will be searched
...
Topics with
lower-level numbers will be searched first
...
However, in
searching the children of ROOT, SUBTOPIC2 would be found first
...
14), the root
node must be named MAIN
...

The second parameter in the format defined above, the , must be a single capital
letter, either M (for MENU) or I (for INFORMATION)
...

The third parameter defined above, the , can be any alphanumeric string of up to
80 characters
...

Beginning a line with the delimiter “$$” forces the loader to treat the line as pure text, even if
one of the key delimiters is in it
...

Example

0MBEGIN-ENTRY-ROOT1
-- Root1 Text -END-ENTRY
1MBEGIN-ENTRY-SUBTOPIC1
-- Subtopic1 Text -END-ENTRY
2IBEGIN-ENTRY-SUBTOPIC4
-- Subtopic4 Text -END-ENTRY
1IBEGIN-ENTRY-SUBTOPIC2
-- Subtopic2 Text -END-ENTRY
0IBEGIN-ENTRY-ROOT2
-- Root2 Text -END-ENTRY
-1MBEGIN-ENTRY-ROOT3
-- Root3 Text -END-ENTRY
0IBEGIN-ENTRY-SUBTOPIC3
-- Subtopic3 Text -END-ENTRY

Tree Diagram of Above Example :
-> ROOT3 ---------> ROOT1 ---------> ROOT2
|
/
\
|
/
\
V
V
V
SUBTOPIC3
SUBTOPIC1 SUBTOPIC2
|
CLIPS Basic Programming Guide

289

CLIPS Reference Manual
|
V
SUBTOPIC4

13
...
2 External Text Manipulation Functions
The following functions are used by the help facility (see section 13
...

13
...
2
...
15
...

Syntax

(fetch )

The function returns the number of entries loaded if the fetch succeeded
...

13
...
2
...

Syntax
(print-region *)

where is a name previously attached to an output device
...
is the name of the previously loaded file in
which the entry is to be found, and the optional arguments, *, is the full path of the
topic entry to be found
...
In addition, the entire name of a field does not need to be specified
...

If there is a conflict, the function will pick the first one in the list
...

^
?

Branch up one level
...

Giving no topic field will branch up one level
...
All levels count
from menu only
...
To access an entry at
the root level after branching down several levels in a previous call or series of calls, an equal
number of branches up must be executed
...
lis on the screen, type
(print-region t "foo
...
lis" roo sub)

Only one entry can be accessed per print-region call
...
If the entry was not found, it returns FALSE
...
lis")
7
CLIPS> (print-region t "foo
...
lis" "?")
-- Root3 Text -TRUE
CLIPS> (print-region t "foo
...
lis" sub)
-- Subtopic4 Text -TRUE
CLIPS> (print-region t "foo
...
lis" ^ root2)
-- Root2 Text -TRUE
CLIPS> (toss "foo
...
15
...
3 Get-region
The function get-region looks up a specified entry in a particular file which has been loaded
previously into the lookup table and returns the contents of that entry as a string
...
The
get-region the print-region functions share the same behavior for the special topic fields and
maintaining the level of the tree for a file between function calls
...

13
...
2
...

Syntax

(toss )

The function returns the symbol TRUE if the toss succeeded
...

13
...

13
...
1 Setting the Profiling Report Threshold
The set-profile-percent-threshold command sets the minimum percentage of time that must be
spent executing a construct or user function for it to be displayed by the profile-info command
...
The return value of
this function is the old percent threshold
...
16
...

Syntax

(get-profile-percent-threshold)

13
...
3 Resetting Profiling Information
The profile-reset command resets all profiling information currently collected for constructs and
user functions
...
16
...
Profiling information is displayed in six columns
...
The second column indicates the number of
times the construct or user function was executed
...
The fourth column is the percentage of time spent in the
construct or user function with respect to the total amount of time profiling was enabled
...
The sixth column is the
percentage of this time with respect to the total amount of time profiling was enabled
...
16
...
If
constructs are profiled, then the amount of time spent executing deffunctions, generic functions,
message handlers, and the RHS of defrules is tracked
...
System defined functions
include predefined functions available for your own use such as the < and numberp functions in
addition to low level internal functions which are not available for your use (these will usually
appear in profile-info output in all capital letters or surrounded by parentheses)
...
Enabling one disables the other
...
Profiling can be repeatedly enable and disabled as long as
only one of constructs or user-functions is consistently enabled
...
If profiling is enabled
from the command prompt, it is a good idea to place the calls enabling and disabling profiling
within a single progn function call
...

Syntax
(profile constructs | user-functions | off)

Example

CLIPS> (clear)
CLIPS> (deffacts start (fact 1))
CLIPS>
(deffunction function-1 (?x)
(bind ?y 1)
(loop-for-count (* ?x 10)
(bind ?y (+ ?y ?x))))
CLIPS>
(defrule rule-1
?f <- (fact ?x&:(< ?x 100))
=>
(function-1 ?x)
(retract ?f)
(assert (fact (+ ?x 1))))
CLIPS>
(reset)
CLIPS>
(progn (profile constructs)
(run)
(profile off))
CLIPS> (profile-info)
Profile elapsed time = 0
...
436704

91
...
436704

91
...
027561
CLIPS> (profile-reset)
CLIPS> (reset)
CLIPS>
(progn (profile user-functions)
(run)
(profile off))
CLIPS> (profile-info)
Profile elapsed time = 12
...
80%

0
...
72%

Function Name
------------retract
assert

%
----0
...
10%

Time+Kids
--------0
...
032766

%+Kids
-----0
...
27%

*** Deffunctions ***
function-1

99

*** Defrules ***

294

Entries
------99
99

Time
-----0
...
012160

Section 13 - Commands

CLIPS Reference Manual
run
1
0
...
000049
*
99
0
...
626217
<
99
0
...
353003
loop-for-count
99
1
...
020747
FACT_PN_VAR3
99
0
...
002693
FACT_JN_VAR3
198
0
...
005478
PROC_PARAM
49599
1
...
102682
PROC_BIND
49599
2
...
0
CLIPS> (profile-info)
Profile elapsed time = 12
...
39%
0
...
05%
30
...
04%
19
...
30%
0
...
02%
0
...
04%
0
...
60%
9
...
35%

12
...
000049
0
...
765490
0
...
997880
11
...
943234
0
...
002693
0
...
012857
1
...
102682
8
...
00%
0
...
06%
47
...
06%
99
...
88%
99
...
02%
0
...
04%
0
...
60%
9
...
16%

Function Name
Entries
------------------+
49599
progn
49698
loop-for-count
99
PROC_PARAM
49599
PROC_GET_BIND
49500
PROC_BIND
49599
CLIPS> (profile-reset)
CLIPS> (profile-info)
CLIPS>

%
----30
...
53%
12
...
60%
9
...
35%

Time+Kids
--------5
...
997880
11
...
036460
1
...
089474

%+Kids
-----47
...
61%
98
...
60%
9
...
16%

CLIPS Basic Programming Guide

Time
-----3
...
353003
1
...
036460
1
...
331363

295

CLIPS Reference Manual

Appendix A - Support Information

A
...
net where YYYY is the current year (for example, 2008)
...
ghg
...
html
...
ghg
...

The CLIPS Expert System Group, a forum for the discussion of CLIPS related topics, is
available at http://groups
...
com/group/CLIPSESG
...
2 DOCUMENTATION
The CLIPS Reference Manuals and User's Guide are available in Portable Document Format
(PDF) at the URL http://www
...
net/clips/download/documentation/
...
adobe
...
html, is needed
to view PDF files
...
22 executables (DOS, Windows XP, and Mac OS),
documentation, and source code
...
For more
information, go to Thomson Course Technology at www
...
com and search for ‘expert
systems
...
3 CLIPS SOURCE CODE AND EXECUTABLES
CLIPS executables can be downloaded from http://www
...
net/clips/download/executables/
...
ghg
...


CLIPS Basic Programming Guide

297

CLIPS Reference Manual

Appendix B - Update Release Notes
The following sections denote the changes and bug fixes for CLIPS versions 6
...
02, 6
...
04, 6
...
1, 6
...
6
...
22, 6
...
24, and 6
...

B
...
30
•

Performance Improvements – Rule performance has been improved particularly in
situations with large numbers of fact/instances or partial matches
...


•

Reset after Clear – A reset command is now performed after a clear command (which
includes the clear command issued internally by CLIPS when it is started)
...


•

Pattern Addition – The initial-fact and initial-object patterns are no longer used in
triggering rules
...


•

Module Specifiers – A module specifier can be used in expressions to reference a
deffunction or defgeneric that is exported by a module, but not specifically imported by the
module which is referencing it
...


•

Command Prompt – Local variables bound at the command prompt using the bind
function persist until a reset or clear command is issued (see section 2
...
1)
...


•

New Functions and Commands - Several new functions and commands have been added
...
2 VERSION 6
...
2)
...

They are:
•
•

deftemplate-slot-defaultp (see section 12
...
4)

•

deftemplate-slot-default-value (see section 12
...
5)

•

deftemplate-slot-existp (see section 12
...
6)

•

deftemplate-slot-multip (see section 12
...
7)

•

deftemplate-slot-names (see section 12
...
8)

•

deftemplate-slot-range (see section 12
...
9)

•

deftemplate-slot-singlep (see section 12
...
10)

•

deftemplate-slot-type (see section 12
...
11)

•

get-char (see section 12
...
2
...
15
...
3)

•

ppfact (see section 13
...
6)

•

read-number (see section 12
...
2
...
4
...
11)

•

300

deftemplate-slot-cardinality (see section 12
...
3)

•

•

deftemplate-slot-allowed-values (see section 12
...
2)

slot-allowed-classes (see section 12
...
1
...
4
...
6)
...
The documentation has been updated to
include the effect of the precision argument on the d, g, o, and x format flags
...


Bug Fixes - The following bugs were fixed by the 6
...


•

Link error occurred for the SlotExistError function when OBJECT_SYSTEM is set to 0
in setup
...


•

An error when calling the Eval
DeallocateEnvironmentData to fail
...


•

Incorrect activations could occur with the exists CE
...


•

The AssignFactSlotDefaults function did not correctly handle defaults for multifield
slots
...


•

CLIPS crashed on AMD64 processor in the function used to generate hash values for
integers
...


A syntax error was not generated for the last deffunction or defmethod in a file if it was
missing the final closing right parenthesis
...
See the Interfaces Guide
for more details
...
6 for Mac OS X
...
3 for Mac OS X
...
NET 2003 for Windows
...
3 VERSION 6
...
9
...
The GetNextFactInTemplate function (see
section 4
...
17 of the Advanced Programming Guide) allows iteration from C over the facts
belonging to a specific deftemplate
...
23 release:
•

•

A large file name (at least 60 characters) passed into the fetch command causes a buffer
overrun
...


•

A large defclass or defgeneric name (at least 500 characters) causes a buffer overrun
when the profile-info command is called
...


•

The FalseSymbol and TrueSymbol constants were not defined as described in the
Advanced Programming Guide
...
See the Advanced Programming Guide for more
details
...


The slot-writablep function returns TRUE for slots having initialize-only access
...


funcall (see section 12
...
10)
...
The expand$
function can be placed around an argument to revert to the old behavior
...
See the Interfaces Guide
for more details
...
4 for Mac OS X and Windows
...
2 for Mac OS X
...
4 VERSION 6
...
22 release:
•

Numerous fixes for functions and macros that did not accept the correct number of
arguments as specified in the Advanced Programming Guide
...


B
...
21
•

Bug Fixes - The following bugs were fixed by the 6
...


•

The C RtnArgCount macro did not have the correct number of arguments
...


•

The C Save macro did not have the correct number of arguments
...


•

The progn$ index variable did not always return the correct value
...


•

C++ style comments in the code caused errors when using strict ANSI C compilation
...


•

Prior bug fix to the PutFactSlot C function prevented memory associated with the fact to
be garbage collected after the fact had been retracted
...
See section 1
...


B
...
2
•

Environments – It is now possible in an embedded application to create multiple
environments into which programs can be loaded
...
See section 2 of The
Interfaces Guide for more details
...
0 CLIPS interface is now
available for Macintosh computers
...


•

COOL Default Behavior – For the purpose of role inheritance, system defined classes
behave as concrete classes (see section 9
...
2
...
The default value for the create-accessor
facet is now read-write (see section 9
...
3
...
For the purpose of pattern-match inheritance,
system defined classes behave as reactive classes unless the inheriting class is abstract (see
section 9
...
2
...
This behavior can be restored to CLIPS 6
...
16
...
25)
...

They are:
•

304

Newly created instances are sent a create message (see sections 9
...
4
...
6
...


funcall (see section 12
...
10)
Appendix B – Update Release Notes

CLIPS Reference Manual

•
•

set-class-defaults-mode (see section 12
...
1
...
3
...
16
...
26)

timer (see section 12
...
11)

Command and Function Enhancements - The following commands and functions have
been enhanced:
•

•

printout (see section 12
...
2
...
The logical name nil now has special significance
...
7
...
Multifield as well as single-field values can now be sorted
...
7
...
The integer value returned by the function can now be
restricted to a specified range of values
...
7
...
4)
...


•

do-for-all-instances (see section 9
...
8
...
Multiple actions can be specified in the action
portion of the query (which previously required an explicit progn call)
...
6
...
The requirement of having at least two case statements has
been removed
...
7
...
6)
...


Bug Fixes - The following bugs were fixed by the 6
...
This would happen if the inner member variable name
shared all of its characters with the first N characters of the outer variable name
...


•

Backspaces were not properly handled in the display window of the Windows interface
...


•

Garbage collection triggered by evaluating the arguments to str-cat/sym-cat could
change the value of the arguments already retrieved
...


•

Defrule data structures could end up in an invalid state during a retract if a fact/object
matched two patterns in a rule and one pattern was inside two nested not conditional
elements and the other pattern was inside one not conditional element
...


•

Garbage collection triggered by expression evaluation during an assert-string call could
corrupt the fact being asserted
...


•

The evaluation error flag was not reset before calling the AssertString C function
...


•

The save command did not always properly save constructs when modules using
import/export specifications were used
...
7 VERSION 6
...
Minimally, non-ANSI C compilers must support full ANSI style function
prototypes and the void data type in order to compile CLIPS
...
16)
...
10 release:
•
•

306

Function modify-instance did not work properly under some circumstances
...
Also, an initialize-only
slot of an existing instance could be changed during the creation/initialization of another
...


•

The temporary expression created by an eval function could inadvertently be garbage
collected
...
05 to handle initialization of instances introduced new bug
whereby initialize-only slots could not be set by init after handlers (or any time after the
function init-slots was called)
...


•

The Windows 95 CLIPS interface did not properly display strings containing two
sequential carriage returns
...


Refresh and scroll bar bugs occurredwhen running the Windows 95 CLIPS interface
under Windows NT
...

They are:
check-syntax (see section 12
...
11)
sort (see section 12
...
9)

•

Command and Function Enhancements - The following commands and functions have
been enhanced:
format (see section 12
...
2
...
The c format flag allows a character to be displayed
...
4
...
1)
...


B
...
05
•

Bug Fixes - The following bugs were fixed by the 6
...


CLIPS Basic Programming Guide

307

CLIPS Reference Manual

•

•

Garbage collection was not handled properly for facts in some situations
...


•

Direct slot access in a message-handler did not check to see if the active instance was
stale potentially causing a crash
...


•

The return value of the while and loop-for-count functions could inadvertently be
garbage collected
...
This causes the
affected patterns never to be matched
...


•

Functions insert$, slot-insert$, and direct-slot-insert$ could courrupt memory under
certain circumstances
...


•

Active-instance-only functions, such as ppinstance, could be invalidly executed out of
context by a deffunction, defrule, or defmethod called as a consequence of a messagehandler action
...


•

308

Version 6
...
04, but this situation was
not detected
...

Appendix B – Update Release Notes

CLIPS Reference Manual

•

•

A crash could occur when objects matching patterns contained within a not conditional
element were changed
...
h conflicted with an identical constant in an OS/2
header file
...


•

Initialization of instances could override slot changes made in put- message-handlers
...


•

•

Binary files were incorrectly saved when the environment contained more than 16,384
symbols, 16,384 integers, or 16,384 floating point
numbers
...


COOL Changes - The following changes have been made to instance behavior:
•
•

•

A multifield value of length 1 is now a legal value for a single-field instance slot
...
This used to be illegal for single-field slots and caused multifield slots to be
assigned a multifield value of zero length
...
4
...
3)
...


•

member$ (see section 12
...
3)
...


•

exit (see section 13
...
7)
...


•

load-instances and restore-instances (see sections 13
...
4
...
11
...
6)
...


CLIPS Basic Programming Guide

309

CLIPS Reference Manual

•

New Functions and Commands - Several new functions and commands have been added
...
2
...
2
...
16
...
24)

B
...
04
•

New Functions and Commands - Several new functions and commands have been added
...
1
...
9
...
9
...
9
...
9
...
9
...
1
...
1
...


•

Bug Fixes - The following bugs were fixed by the 6
...


•

Embedding exclusively test CEs within not and/or and CEs did not work properly
...


•

The GetNthWatchValue and GetNthWatchName functions in watch
...


•

310

CLIPS would hang during an unwatch command if a binary file had been loaded that
contained an or conditional element
...


Appendix B – Update Release Notes

CLIPS Reference Manual

•

Nested calls to CLIPSFunctionCall and other functions from an embedded application
could cause premature garbage collection while a function is executing
...
10 VERSION 6
...
03 release:
•

The error message [INSMNGR11] was incorrectly labeled as [INSMNGR1111]
...


•

Instance name restriction and type constraint conflicts were not detected
...


•

There were symbol garbage collection problems when using CLIPSFunctionCall from
an embedded application
...


•

Link errors were generated by the file factrhs
...


•

Conflicts between the type and allowed-values attributes were not detected
...


•

Memory allocation problems existed on machines with architectures utilizing pointers
and integers larger than 32-bits
...


•

The explicit getenv definition in edterm
...
h definition
...


CLIPS Basic Programming Guide

311

CLIPS Reference Manual

•

Errors generated when calling the Send C function from an embedded application would
prevent subsequent calls from working correctly
...
1 CLIPS interface dialog window caused a ‘_’ to
appear instead
...


•

The isalpha library function did not return the correct value in the scanner
...
h is included after stdio
...
0
...


•

Memory deallocation could work improperly if BLOCK_MEMORY was used and a
memory block larger than the block memory table is deallocated
...


•

Redefining a deftemplate could cause a crash under some conditions
...
1
CLIPS interface would cause a crash
...


•

Messages could be sent to out of scope instances
...


B
...
02
•

Bug Fixes - The following bugs were fixed by the 6
...


Appendix B – Update Release Notes

CLIPS Reference Manual

•

The code generated by the constructs-to-c command for rules with logical or or
conditional elements would not compile
...


•

The use of the object-pattern-match-delay function could cause extraneous activations
of rules
...


•

The function slot-types could corrupt memory when called for any slot that could hold
an instance name
...
Thus, if
one of the instances is from an imported class, other operations on that variable may not
be able to access the instance
...


•

The slot-cardinality function caused a crash when called for single-field slots
...
c when the DEFRULE_CONSTRUCT flag was disabled,
but the LOGICAL_DEPENDENCIES flag was enabled in setup
...


•

Changing the focus on the RHS of a rule and then issuing a return command would
remove the newly focused module and not the rule’s module from the focus stack
...
h header file was not included in some of the distribution packages
...


•

The instance-set query functions generated an invalid slot reference when the ‘:’ is the
last character in a instance-set member variable name longer than two characters
...
12 VERSION 6
...
01 release:

CLIPS Basic Programming Guide

313

CLIPS Reference Manual

•
•

Calling the refresh-agenda command under certain circumstances would change the
current setting of the salience evaluation attribute
...


•

Under some situations, the wrong pattern CE number was printed when an error
occurred in a rule
...


•

Some internal CLIPS routines for accessing values from facts would cause crashes under
some circumstances
...


•

There were erroneous and missing error messages associated with constraint checking
on the LHS of rules
...


•

Global variables were not exported properly by modules
...
c generated an error
using some compilers
...


•

Or CEs within not CEs were not always handled properly
...


•

Memory was not garbage collected when some embedded functions were used at the
equivalent of the top-level command prompt
...


Using the return command to return a multifield value from within the while or
loop-for-count functions did not work properly
...

abstraction

The definition of new classes to describe the common properties
and behavior of a group of objects
...


activation

A rule is activated if all of its conditional elements are satisfied
and it has not yet fired based on a specific set of matching pattern
entities that caused it to be activated
...
An activated
rule that is placed on the agenda is called an activation
...


agenda

A list of all rules that are presently ready to fire
...
The
rule at the top of the agenda is the next rule that will fire
...


bind

The action of storing a value in a variable
...


class precedence list

A linear ordering of classes which describes the path of
inheritance for a class
...


command prompt

In the interactive interface, the “CLIPS>” prompt which indicates
that CLIPS is ready for a command to be entered
...


CLIPS Basic Programming Guide

315

CLIPS Reference Manual

conditional
element

A restriction on the LHS of a rule which must be satisfied in order
for the rule to be applicable (also referred to as a CE)
...
There are seven different
conflict resolution strategies: depth, breadth, simplicity,
complexity, lex, mea, and random
...


constant

A non-varying single field value directly expressed as a series of
characters
...
For example, the ~red constraint is
satisfied if the field to which the constraint is applied is not the
symbol red
...


construct

A high level CLIPS abstraction used to add components to the
knowledge base
...


current module

The module to which newly defined constructs that do not have a
module specifier are added
...


daemon

A message-handler which executes implicitly whenever some
action is taken upon an object, such as initialization, deletion, or
slot access
...


deftemplate fact

A deftemplate name followed by a list of named fields (slots) and
specific values used to represent a deftemplate object
...
Also called a non-ordered
fact
...
A

316

Appendix C - Glossary

CLIPS Reference Manual

deftemplate object is simply an informal term for the collections
of slots (without specific values) which define a deftemplate
...
A deftemplate
pattern describes the attributes and associated values of a
deftemplate object
...


delimiter

A character which indicates the end of a symbol
...


dynamic binding

The deferral of which message-handlers will be called for a
message until run-time
...


expression

A function call with arguments specified
...
3
...


external function

A function written in an external language (such as C or Ada)
defined by the user or provided by CLIPS and called from within
CLIPS rules
...
g
...


fact

An ordered or deftemplate (non-ordered) fact
...


fact-address

A pointer to a fact obtained by binding a variable to the fact which
matches a pattern on the LHS of a rule
...
It consists of the

CLIPS Basic Programming Guide

317

CLIPS Reference Manual

character “f”, followed by a dash, followed by the fact-index of
the fact
...


fact-list

The list of current facts
...


fire

A rule is said to have fired if all of its conditions are satisfied and
the actions then are executed
...

A floating point number must have at least one digit in it (not
including the exponent) and must either contain a decimal point or
an exponent (see section 2
...
1 for more details)
...
As a noun, refers
to the current focus
...
The module at
the top of the focus stack is the current focus
...


function

A piece of executable code identified by a specific name which
returns a useful value or performs a useful side effect
...


generic dispatch

The process whereby applicable methods are selected and
executed for a particular generic function call
...


inference engine

The mechanism provided by CLIPS which automatically matches
patterns against the current state of the fact-list and list of
instances and determines which rules are applicable
...


instance

An object is an instance of a class
...


instance (of a
user-defined class)

An object which can only be manipulated via messages, i
...


instance-address

The address of an instance of a user-defined class (see section
2
...
1 for more details)
...
3
...
An instance-name refers to an object of the
specified name which is an instance of a user-defined class
...
Each
member of an instance-set is an instance of a set of classes, where
the set can be different for each member
...


instance-set query

A user-defined boolean expression applied to an instance-set to
see if it satisfies further user-defined criteria
...
3
...


LHS

Left-Hand Side
...


list

A group of items with no implied order
...


message

The mechanism used to manipulate an object
...


message-handler

An implementation of a message for a particular class of objects
...


method

An implementation of a generic function for a particular set of
argument restrictions
...


method precedence

The property used by the generic dispatch to select a method when
more than one is applicable to a particular generic function call
...
Also used to control the
flow of execution of rules through the use of the focus command
...
It consists of a module name
followed by two colons
...


multifield

A sequence of unnamed placeholders each having a value
...


non-ordered fact

A deftemplate fact
...


object

A symbol, a string, a floating-point or integer number, a multifield
value, an external address or an instance of a user-defined class
...


ordered fact

A sequence of unnamed fields
...


overload

The process whereby a generic function can do different things
depending on the types and number of its arguments, i
...
the
generic function has multiple methods
...


pattern entity

An item that is capable of matching a pattern on the LHS of a rule
...


pattern-matching

The process of matching facts or instances to patterns on the LHS
of rules
...


primitive type object

A symbol, string, integer, float, multifield or external-address
...
Synonomous with the
associated deftemplate name
...
The actions to be performed when the LHS of a
rule is satisfied
...
When all patterns are
satisfied, the actions will be taken
...
When multiple rules are ready
for firing, they are fired in order of priority
...
Rules with the same salience are fired according to the
current conflict resolution strategy
...


shadowed
message-handler

A message-handler that must be explicitly called by another
message-handler in order to execute
...


CLIPS Basic Programming Guide

321

CLIPS Reference Manual

single-field value

One of the primitive data types: float, integer, symbol, string,
external-address, instance-name, or instance-address
...
To write a slot give the field
name (attribute) followed by the field value
...
Note
that a multifield slot with one value is strictly not the same as a
single field slot
...


slot-accessor

Implicit message-handlers which provide read and write access to
slots of an object
...
A class is more specific than any of its
superclasses
...
The specificity is determined by the
number of constants, variables, and function calls used within
LHS conditional elements
...
3
...


subclass

If a class inherits from a second class, the first class is a subclass
of the second class
...


symbol

Any sequence of characters that starts with any printable ASCII
character and is followed by zero or more characters (see section
2
...
1 for more details)
...


value

A single or multifield value
...


322

Appendix C - Glossary

CLIPS Reference Manual

Appendix D - Integrated Editor
CLIPS includes a fully integrated version of the full screen MicroEMACS editor
...
Since the editor is full
screen, portions of it are highly machine dependent
...

The editor may be called from CLIPS with the following command:
(edit [""])

The file name is optional
...
If no file name is given, the
editor is entered without loading a file
...
To exit the editor and clear all buffers, use or
...
To
compile a rules section, mark a region and type
...
The editor can use extensive amounts of memory, and a flag is available in
clips
...

When using the editor on multiuser machines like the VAX or many UNIX environments, be
careful with the control S and control Q commands; they could conflict with terminal
XON/XOFF communications
...

The save file command, normally , is also Z
...
The control Q command is rarely needed in a
CLIPS file and, therefore, has no substitute
...
1 SPECIAL CHARACTERS



CLIPS Basic Programming Guide

Delete previous character (also on some terminals)
...


323

CLIPS Reference Manual

D
...

Move cursor to beginning of line
...

Start a new interactive command shell
...

Move cursor to END of line
...

Abort any command
...

Insert a TAB
...

KILL (delete) to end of line
...

Insert a CR-LF
...

OPEN a new line
...

QUOTE the next character (insert the next character typed)
...

Forward SEARCH (also )
...

Enter repeat count for next command
...

KILL region (all text between cursor and last mark set)
...

YANK (undelete) last text killed
...


Appendix D - Integrated Editor

CLIPS Reference Manual

D
...

End keyboard Macro
...

Show current cursor column and line number
...

Display current window only
...

Switch to a different BUFFER
...

Set FILL column
...

MATCH parenthesis (or {} or [])
...

Move to PREVIOUS window
...

Global SEARCH and replace (forwards)
...

Show active BUFFERS
...

FIND file
...

Scroll current window up by repeat count lines
...

RENAME file
...

SAVE (write) current buffer into its file
...
Read file and display in current window
...
Option to change name of file
...


325

CLIPS Reference Manual

D
...

B
C
D
F
J
L
R
S
U
V
W
Z


326

Move current line to repeat count lines from top of window
...

Move cursor to beginning of buffer
...

Move cursor BACK one word
...

DELETE next word
...

SEARCH forward (same as )
...

Query search and REPLACE (backwards)
...

UPPERCASE (uppercase) next word
...

COPY region into kill buffer
...

DELETE previous word
...
Included are discussions of pattern ordering in rules, use of deffunctions
in lieu of non-overloaded generic functions, parameter restriction ordering in generic function
methods, and various approaches to improving the speed of message-passing and reading slots of
instances
...
1 ORDERING OF PATTERNS ON THE LHS
The issues which affect performance of a rule-based system are considerably different from
those which affect conventional programs
...

CLIPS is a rule language based on the RETE algorithm
...
CLIPS has attempted to implement this
algorithm in a manner that combines efficient performance with powerful features
...
However,
to use CLIPS properly requires some understanding of how the pattern-matcher works
...
As facts and instances of reactive classes (referred
to collectively as pattern entities) are created, they are filtered through the pattern network
...
When pattern entities exist that match all patterns on the LHS of the
rule, variable bindings (if any) are considered
...
e
...
If the variable
bindings for all patterns are consistent with the constraints applied to the variables, the rules are
activated and placed on the agenda
...
A number
of important considerations come out of this
...
The time involved in doing this is fairly constant
...
Therefore, the single
most important performance factor is the ordering of patterns on the LHS of the rule
...
At
best, there seem to be three “quasi” methods for ordering the patterns
...
The more wildcards or unbound variables there are in a
pattern, the lower it should go
...
This technique often is used to provide control structure in an expert
system; e
...
, some kind of “phase” fact
...
This is most effective if
the single pattern consists only of literal constraints
...
The use of phase
facts is not recommended for large programs if they are used solely for controlling the flow
of execution (use modules instead)
...
A large number of patterns of a particular form in the fact-list or instance-list can
cause numerous partial instantiations of a rule that have to be “weeded” out by comparing
the variable bindings, a slower operation
...
Every time a pattern entity is
created, it must be filtered through the network
...
By putting volatile patterns last, the
variable bindings only will be checked if all of the rest of the patterns already exist
...
At best, they provide
some rough guidelines
...
The best
approach is to develop the rules with minimal consideration of ordering
...

Another performance issue is the use of multifield variables and wildcards ($?)
...
Since they can bind to zero or
more fields, they can cause multiple instantiations of a single rule
...

Some final notes on rule performance
...
” The list of pattern entities should not be used as a data base for storage
of extraneous information
...
Keep the pattern-matching to a minimum and be as specific as possible
...

E
...
If a generic function has
only one method, a deffunction probably would be better
...
In addition, if recompiling and
328

Appendix E - Performance Considerations

CLIPS Reference Manual

relinking CLIPS is not prohibitive, user-defined external functions are even more efficient than
deffunctions
...
For more details, see sections 7 and 8
...

E
...
The programmer can take advantage of this by placing parameter restrictions which are
less frequently satisfied than others first in the list
...
If a group of
restrictions are all equally likely to be satisfied, placing the simpler restrictions first, such as
those without queries, will also allow the generic dispatch to conclude more quickly for a method
that is not applicable
...
4
...

E
...

However, when an instance is referenced by name, CLIPS must perform an internal lookup to
find the instance-address anyway
...
This will allow
CLIPS to always go directly to the instance
...
4
...
16
...
6
...
5 READING INSTANCE SLOTS DIRECTLY
Normally, message-passing must be used to read or set a slot of an instance
...
Accessing slots directly is significantly faster than message-passing
...
For more details, see sections 9
...
2, 9
...
3, 9
...
4, 9
...
3, 9
...
4 and 9
...
3
...
This appendix describes some of the
more common warning messages and what they mean
...

[CONSCOMP1] WARNING: Base file name exceeds 3 characters
...

The constructs-to-c command generates file names using the file name prefix supplied as an
argument
...

[CONSCOMP2] WARNING: Array name exceeds 6 characters in length
...

The constructs-to-c command generates arrays for storing data structures
...

[CSTRCPSR1] WARNING: Redefining :
This indicates that a previously defined construct of the specified type has been redefined
...
Constraints attached to deftemplate and defclass slots will not be
saved with the runtime or binary image in these cases since it is assumed that dynamic constraint
checking is not required
...

[DFFNXFUN1] WARNING: Deffunction only partially deleted due to usage by
other constructs
...

Example:
CLIPS>

CLIPS Basic Programming Guide

331

CLIPS Reference Manual
(deffunction foo ()
(printout t "Hi there!" crlf))
CLIPS>
(deffunction bar ()
(foo)
(undeffunction *))
CLIPS> (bar)

[GENRCBIN1] WARNING: COOL not installed! User-defined class in method restriction
substituted with OBJECT
...
The
restriction containing the defclass will match any of the primitive types
...

This warning occurs when an around message-handler is loaded using the bload command into
a CLIPS configuration not supporting imperative message-handlers
...

This warning occurs when a before or an after message-handler is loaded using the bload
command into a CLIPS configuration not supporting auxiliary message-handlers
...
This appendix describes some of the
more common error messages and what they mean
...

[AGENDA1] Salience value must be an integer value
...

Example:
CLIPS> (defrule error (declare (salience a)) =>)

[AGENDA2] Salience value out of range to
The range of allowed salience has an explicit limit; this error message will result if the value is
out of that range
...

[ANALYSIS1] Duplicate pattern-address found in CE
...

Example:
CLIPS> (defrule error ?f <- (a) ?f <- (b) =>)

[ANALYSIS2] Pattern-address used in CE #2 was previously bound
within a pattern CE
...

Example:
CLIPS> (defrule error (a ?f) ?f <- (b) =>)

[ANALYSIS3] Variable is used as both a single and multifield variable
...

Example:
CLIPS> (defrule error (a ?x $?x) =>)

[ANALYSIS4] Variable [found in the expression ]
was referenced in CE before being defined
A variable cannot be referenced before it is defined and, thus, results in this error message
...

[ARGACCES2] Function was unable to open file
This error occurs when the specified function cannot open a file
...

[ARGACCES4] Function expected exactly argument(s)
This error occurs when a function that expects a precise number of argument(s) receives an
incorrect number of arguments
...

[ARGACCES4] Function expected no more than argument(s)
This error occurs when a function receives more than the maximum number of argument(s)
expected
...

[ARGACCES6] Function received a request from function for
argument # which is not of type
This error occurs when a function requests from another function the wrong type of argument,
typically a string or symbol, when expecting a number or vice versa
...

If the bload command was used to load in a binary image, then the named construct cannot be
entered until a clear command has been performed to remove the binary image
...


334

Appendix G - CLIPS Error Messages

CLIPS Reference Manual

[BLOAD3] File is an incompatible binary construct file
This error occurs when the bload command is used to load a file that was created with the bsave
command using a different version of CLIPS
...

Binary load cannot continue
...

[BLOAD5] Some constructs are still in use by the current binary image:



...

This error occurs when the current binary image cannot be cleared because some constructs are
still being used
...

[BLOAD6] The following undefined functions are referenced by this binary image:



...

[BSAVE1] Cannot perform a binary save while a binary load is in effect
...

[CLASSEXM1] Inherited slot from class is not valid for function
slot-publicp
This error message occurs when the function slot-publicp is given an inherited slot
...

Example:
CLIPS>
(defclass FOO (is-a USER)
(slot woz (visibility private)))
CLIPS>
(defclass BAR (is-a FOO))
CLIPS> (slot-publicp BAR woz)

[CLASSFUN1] Unable to find class in function
...


CLIPS Basic Programming Guide

335

CLIPS Reference Manual

Example:
CLIPS> (class-slots FOO)

[CLASSFUN2] Maximum number of simultaneous class hierarchy traversals exceeded

...
g
...
The direct or indirect nesting of instance-set query functions is limited in
the following way:
Ci is the number of members in an instance-set for the ith nested instance-set query function
...

N

! Ci
i=1

<= 128 (the default upper limit)

Example:
CLIPS>
(deffunction my-func ()
(do-for-instance ((?a USER) (?b USER) (?c USER)) TRUE
(printout t ?a " " ?b " " ?c crlf))
; The sum here is C1 = 3 which is OK
...


The default upper limit of 128 should be sufficient for most if not all applications
...
H and recompiling CLIPS
...

Only concrete classes can be reactive
...

Predefined system classes cannot be modified by the user
...

This error occurs when an attempt to redefine a class is made under one or both of the following
two circumstances:
1) The class (or any of its subclasses) has instances
...

Before the class can be redefined, all such instances and methods must be deleted
...

Only one specification of a class attribute is allowed
...

Slots in a defclass must be unique
...

Only one occurrence of a facet per slot is allowed
...

Example:
CLIPS Basic Programming Guide

337

CLIPS Reference Manual
CLIPS>
(defclass A (is-a USER)
(slot foo (cardinality 3 5)))

[CLSLTPSR4] read-only slots must have a default value
Since slots cannot be unbound and read-only slots cannot be set after initial creation of the
instance, read-only slots must have a default value
...

Example:
CLIPS>
(defclass A (is-a USER)
(slot foo (access read-only)
(create-accessor write)))

[CLSLTPSR6] no-inherit slots cannot also be public
no-inherit slots are by definition not accessible to subclasses and thus only visible to the parent
class
...

Example:
CLIPS> )

[COMMLINE2] Expected a command
...

Example:

CLIPS> ("facts"

338

Appendix G - CLIPS Error Messages

CLIPS Reference Manual

[CONSCOMP1] Invalid file name contains '
...
' cannot be used in the file name prefix that is passed to the constructs-to-c command since
this prefix is used to generate file names and some operating systems do not allow more than one
'
...

[CONSTRCT1] Some constructs are still in use
...

This error occurs when the clear command is issued when a construct is in use (such as a rule
that is firing)
...

This error occurs when the load command expects a left parenthesis followed a construct type
and these token types are not found
...

Example:
CLIPS> (defgeneric ())

[CSTRCPSR3] Cannot define because of an
import/export conflict
...

A construct cannot be defined if defining the construct would allow two different definitions of
the same construct type and name to both be visible to any module
...

A construct cannot be redefined while it is being used by another construct or other data structure
(such as a fact or instance)
...


CLIPS Basic Programming Guide

339

CLIPS Reference Manual

Example:

CLIPS> (deftemplate foo (slot x (type SYMBOL)))
CLIPS> (assert (foo (x 3)))

[CSTRNPSR1] The attribute conflicts with the name> attribute
...

Example:

CLIPS> (deftemplate foo (slot x (type SYMBOL) (range 0 2)))

[CSTRNPSR2] Minimum value must be less than
or equal to the maximum value
...

Example:

CLIPS> (deftemplate foo (slot x (range 8 1)))

[CSTRNPSR3] The attribute cannot be used in conjunction with
the attribute
...

Example:

CLIPS> (deftemplate foo (slot x (allowed-values a)
(allowed-symbols b)))

[CSTRNPSR4] Value does not match the expected type for the attribute
...
g
...

Example:

CLIPS> (deftemplate example (slot x (allowed-integers 3
...

The cardinality attribute can only be used for slots defined with the multislot keyword
...

Example:

CLIPS> (deftemplate error (slot x (default)))

340

Appendix G - CLIPS Error Messages

CLIPS Reference Manual

[DFFNXPSR1] Deffunctions are not allowed to replace constructs
...

Example:
CLIPS> (deffunction defgeneric ())

[DFFNXPSR2] Deffunctions are not allowed to replace external functions
...

Example:
CLIPS> (deffunction + ())

[DFFNXPSR3] Deffunctions are not allowed to replace generic functions
...

Example:

CLIPS> (defgeneric foo)
CLIPS> (deffunction foo ())

[DFFNXPSR4] Deffunction may not be redefined while it is executing
...

Example:
CLIPS>
(deffunction foo ()
(build "(deffunction foo ())"))
CLIPS> (foo)

[DFFNXPSR5] Defgeneric imported from module conflicts with
this deffunction
...

Example:
CLIPS>
CLIPS>
CLIPS>
CLIPS>

(defmodule MAIN (export ?ALL))
(defmethod foo ())
(defmodule FOO (import MAIN ?ALL))
(deffunction foo)

[DRIVE1] This error occurred in the join network
Problem resides in join # in rule(s):
+
This error pinpoints other evaluation errors associated with evaluating an expression within the
join network
...


CLIPS Basic Programming Guide

341

CLIPS Reference Manual

[EMATHFUN1] Domain error for function
This error occurs when an argument passed to a math function is not in the domain of values for
which a return value exists
...

[EMATHFUN3] Singularity at asymptote in function
This error occurs when an argument to a trigonometric math function would cause a singularity
...

Example:

CLIPS> (progn ?error)

[EVALUATN2] No function, generic function or deffunction of name exists for
external call
...


[EXPRNPSR1] A function name must be a symbol
In the following example, '~' is recognized by CLIPS as an operator, not a function:
Example:
CLIPS> (+ (~ 3 4) 4)

[EXPRNPSR2] Expected a constant, variable, or expression
In the following example, '~' is an operator and is illegal as an argument to a function call:
Example:

CLIPS> (<= ~ 4)

[EXPRNPSR3] Missing function declaration for
CLIPS does not recognize as a declared function and gives this error message
...

The sequence expansion operator cannot be used with certain functions
...
The specific pattern and field of the problem rules are identified
...

Example:
CLIPS>
(defrule error
(test (assert (blah)))
=>)
CLIPS> (reset)

[FACTRHS1] Template does not exist for assert
...
In other situations, CLIPS will create an implied deftemplate if one does
not already exist
...
bin)
(bload error
...

This error occurs when the generic function name passed to the undefmethod function does not
exist
...

This error occurs when an invalid method index is passed to undefmethod (e
...
a negative integer
or a symbol other than *)
...

It is illegal to specify a non-wildcard method index when a wildcard is given for the generic
function in the function undefmethod
...

A method corresponding to a system defined function cannot be deleted
...

CLIPS> (undefmethod integer 1)

[GENRCEXE1] No applicable methods for
...

Example:
CLIPS> (defmethod foo ())
CLIPS> (foo 1 2)

[GENRCEXE2] Shadowed methods not applicable in current context
...

Example:

CLIPS> (call-next-method)

[GENRCEXE3] Unable to determine class of in generic function
...

Example:
CLIPS> (defmethod foo ((?a INTEGER)))
CLIPS> (foo [bogus-instance])

344

Appendix G - CLIPS Error Messages

CLIPS Reference Manual

[GENRCEXE4] Generic function method # is not applicable to the given
arguments
...

Example:

CLIPS> (defmethod foo ())
CLIPS> (call-specific-method foo 1 abc)

[GENRCFUN1] Defgeneric cannot be modified while one of its methods is
executing
...

Example:

CLIPS> (defgeneric foo)
CLIPS> (defmethod foo () (build "(defgeneric foo)"))
CLIPS> (foo)

[GENRCFUN2] Unable to find method # in function
...

Example:
CLIPS> (defmethod foo 1 ())
CLIPS> (ppdefmethod foo 2)

[GENRCFUN3] Unable to find generic function in function
...

Example:
CLIPS> (preview-generic balh)

[GENRCPSR1] Expected ')' to complete defgeneric
...

Example:

CLIPS> (defgeneric foo ())

[GENRCPSR2] New method # would be indistinguishable from method
#
...

Example:

CLIPS> (defmethod foo 1 ((?a INTEGER)))
CLIPS> (defmethod foo 2 ((?a INTEGER)))

CLIPS Basic Programming Guide

345

CLIPS Reference Manual

[GENRCPSR3] Defgenerics are not allowed to replace constructs
...

[GENRCPSR4] Deffunction imported from module conflicts with
this defgeneric
...

Example:

CLIPS>
CLIPS>
CLIPS>
CLIPS>

(defmodule MAIN (export ?ALL))
(deffunction foo ())
(defmodule FOO (import MAIN ?ALL))
(defmethod foo)

[GENRCPSR5] Generic functions are not allowed to replace deffunctions
...

[GENRCPSR6] Method index out of range
...

Example:

CLIPS> (defmethod foo 0 ())

[GENRCPSR7] Expected a '(' to begin method parameter restrictions
...

Example:

CLIPS> (defmethod foo)

[GENRCPSR8] Expected a variable for parameter specification
...

Example:
CLIPS> (defmethod foo ((abc)))

[GENRCPSR9] Expected a variable or '(' for parameter specification
...

Example:
CLIPS> (defmethod foo (abc))

[GENRCPSR10] Query must be last in parameter restriction
...

Example:

CLIPS> (defmethod foo ((?a (< ?a 1) INTEGER)))

346

Appendix G - CLIPS Error Messages

CLIPS Reference Manual

[GENRCPSR11] Duplicate classes/types not allowed in parameter restriction
...

Example:

CLIPS> (defmethod foo ((?a INTEGER INTEGER)))

[GENRCPSR12] Binds are not allowed in query expressions
...

Example:
CLIPS> (defmethod foo ((?a (bind ?b 1))))

[GENRCPSR13] Expected a valid class/type name or query
...

Example:

CLIPS> (defmethod foo ((?a 34)))

[GENRCPSR14] Unknown class/type in method
...

Example:
CLIPS> (defmethod foo ((?a bogus-class)))

[GENRCPSR15] class is redundant
...

Example:
CLIPS> (defmethod foo ((?a INTEGER NUMBER)))

[GENRCPSR16] The system function cannot be overloaded
...

Example:

CLIPS> (defmethod if ())

[GENRCPSR17] Cannot replace the implicit system method #
...

Example:
CLIPS> (defmethod integer ((?x NUMBER)) (* 2 ?x))

CLIPS Basic Programming Guide

347

CLIPS Reference Manual

[GLOBLDEF1] Global variable is unbound
...

Example:
CLIPS> (clear)
CLIPS> ?*x*

[GLOBLPSR1] Global variable was referenced, but is not defined
...

Example:
CLIPS> (clear)
CLIPS> ?*x*

[INCRRSET1] The incremental reset behavior cannot be changed with rules loaded
...

[INHERPSR1] A class may not have itself as a superclass
...

Example:

CLIPS> (defclass A (is-a A))

[INHERPSR2] A class may inherit from a superclass only once
...

Example:

CLIPS> (defclass A (is-a USER USER))

[INHERPSR3] A class must be defined after all its superclasses
...

Example:
CLIPS> (defclass B (is-a A))

[INHERPSR4] Must have at least one superclass
...

Example:
CLIPS> (defclass A (is-a))

[INHERPSR5] Partial precedence list formed: …
Precedence loop in superclasses: …
No class precedence list satisfies the rules specified in section 9
...
1
...
The message shows a conflict for because the precedence implies that
348

Appendix G - CLIPS Error Messages

CLIPS Reference Manual

must both precede and succeed through
...
This loop is not necessarily the
only loop in the precedence list; it is the first one detected
...

Example:

CLIPS> (defclass A (is-a MULTIFIELD FLOAT SYMBOL))
CLIPS> (defclass B (is-a SYMBOL FLOAT))
CLIPS> (defclass C (is-a A B))

[INHERPSR6] A user-defined class cannot be a subclass of
...

Example:

CLIPS> (defclass A (is-a INSTANCE))

[INSCOM1] Undefined type in function
...

[INSFILE1] Function could not completely process file
...

Example:

CLIPS> (load-instances bogus
...

or
[INSFILE3] file is not a compatible binary instances file
...

Example:
CLIPS> (reset)
CLIPS> (save-instances foo
...
ins)

[INSFILE4] Function bload-instances unable to load instance
...

Example:
CLIPS> (defclass A (is-a USER) (role concrete))
CLIPS> (make-instance of A)
[gen1]

CLIPS Basic Programming Guide

349

CLIPS Reference Manual
CLIPS>
1
CLIPS>
CLIPS>
CLIPS>

(bsave-instances foo
...
bin)

[INSFUN1] Expected a valid instance in function
...

Example:

CLIPS> (initialize-instance 34)

[INSFUN2] No such instance in function
...

Example:

CLIPS> (instance-address [bogus-instance])

[INSFUN3] No such slot in function
...

Example:
CLIPS> (defclass A (is-a USER))
CLIPS> (slot-writablep A b)

[INSFUN4] Invalid instance-address in function
...

Example:

CLIPS>
CLIPS>
[a]
CLIPS>
CLIPS>
[a]
CLIPS>

(defclass A (is-a USER))
(make-instance a of A)
(defglobal ?*x* = (instance-address a))
(make-instance a of A)
(class ?*x*)

[INSFUN5] Cannot modify reactive instance slots while pattern-matching is in process
...
Functions used on the LHS of a rule should not have side effects (such as the changing
slot values)
...

This error occurs when the number of simultaneous class hierarchy traversals is exceeded while
pattern-matching on a shared slot
...

[INSFUN7] illegal for single-field slot of instance
found in
...

Example:
CLIPS> (set-static-constraint-checking FALSE)
TRUE
CLIPS>
(defclass FOO (is-a USER)
(role concrete)
(slot foo))
CLIPS>
(defmessage-handler FOO error ()
(bind ?self:foo 1 2 3))
CLIPS> (make-instance foo of FOO)
[foo]
CLIPS> (send [foo] error)

[INSFUN8] Void function illegal value for slot of instance found in

...

Example:
CLIPS> (set-static-constraint-checking FALSE)
TRUE
CLIPS>
(defclass FOO (is-a USER)
(role concrete)
(slot foo))
CLIPS>
(defmessage-handler FOO error ()
(bind ?self:foo (instances)))
CLIPS> (make-instance foo of FOO)
[foo]
CLIPS> (send [foo] error)

[INSMNGR1] Expected a valid name for new instance
...

Example:
CLIPS> (make-instance 34 of A)

CLIPS Basic Programming Guide

351

CLIPS Reference Manual

[INSMNGR2] Expected a valid class name for new instance
...

Example:

CLIPS> (make-instance a of 34)

[INSMNGR3] Cannot create instances of abstract class
...

Example:
CLIPS> (make-instance [foo] of USER)

[INSMGNR4] The instance has a slot-value which depends on the instance
definition
...

Example:
CLIPS>
(defclass A (is-a USER)
(slot foo))
CLIPS>
(make-instance a of A (foo (make-instance a of A)))

[INSMNGR5] Unable to delete old instance
...
This error
occurs if that deletion fails
...

The evaluation of a slot-override in make-instance or initialize-instance attempted to delete the
instance
...

An instance cannot be reinitialized during initialization
...

This message is displayed when an evaluation error occurs while the init message is executing
for an instance
...

make-instance and initialize-instance expect symbols for slot names
...

CLIPS does not allow instances of reactive classes to be created while pattern-matching is taking
place
...

Example:

CLIPS> (defclass FOO (is-a USER) (role concrete) (pattern-match reactive))
CLIPS> (defrule BAR (x) (test (make-instance of FOO)) =>)
CLIPS> (assert (x))

[INSMNGR11] Invalid module specifier in new instance name
...

Example:

CLIPS> (defclass FOO (is-a USER) (role concrete))
CLIPS> (make-instance BOGUS::x of FOO)

CLIPS Basic Programming Guide

353

CLIPS Reference Manual

[INSMNGR12] Cannot delete instances of reactive classes while pattern-matching is in
process
...
Functions used on the LHS of a rule should not have side effects (such as the deletion of a
new instance or the retraction of a fact)
...

This error occurs when the slot name of a slot override does not correspond to any of the valid
slot names for an instance
...

If the ?NONE keyword was specified with the default attribute for a slot, then a slot override
must be provided when an instance containing that slot is created
...

The special function init-slots (for initializing slots of an instance to the class default values) can
only be called during the dispatch of an init message for an instance, i
...
, in an init
message-handler
...

The direct-modify and message-modify message-handlers attached to the class USER can only
be called as a result of the appropriate message being sent
...
Additional handlers may be defined, but the message can
only be sent in this context
...

The direct-duplicate and message-duplicate message-handlers attached to the class USER can
only be called as a result of the appropriate message being sent
...
Additional handlers may be defined, but the message can
only be sent in this context
...

If an instance-name is specified for the new instance in the call to duplicate-instance, it must be
different from the source instance’s name
...

The functions described in section 12
...
4
...

Example:

CLIPS>
(defclass A (is-a USER)
(slot foo))
CLIPS> (make-instance a of A)
[a]
CLIPS> (slot-insert$ a foo 1 abc def)

[INSQYPSR1] Duplicate instance-set member variable name in function
...

Example:

CLIPS> (any-instancep ((?a OBJECT) (?a OBJECT)) TRUE)

[INSQYPSR2] Binds are not allowed in instance-set query in function
...


CLIPS Basic Programming Guide

355

CLIPS Reference Manual

Example:
CLIPS>
(any-instancep ((?a OBJECT) (?b OBJECT))
(bind ?c 1))

[INSQYPSR3] Cannot rebind instance-set member variable in function
...

Example:
CLIPS>
(do-for-all-instances ((?a USER))
(if (slot-existp ?a age) then
(> ?a:age 30))
(bind ?a (send ?a get-brother)))

[IOFUN1] Illegal logical name used for function
...

Example:
(printout (create$ a b c) x)

[IOFUN2] Logical name already in use
...

Example:
CLIPS> (open "foo
...
txt" foo "w")

[MEMORY1] Out of memory
This error indicates insufficient memory exists to expand internal structures enough to allow
continued operation (causing an exit to the operating system)
...

[MEMORY3] Unable to allocate memory block > 32K
This error occurs when the bload function attempts to allocate a block of memory larger than
32K and the operating system does not permit blocks greater than 32K to be allocated
...
When this
error occurs, CLIPS exits to the operating system
...

The expand$ function may not be called unless it is within the argument list of another function
...

The module specifier can only be used as part of a defined construct’s name or as an argument to
a function
...

or
[MODULPSR1] Module does not export any constructs
...

A construct cannot be imported from a module unless the defmodule exports that construct
...

It is illegal to specify a non-wildcard handler index when a wildcard is given for the class in the
external C function UndefmessageHandler()
...

[MSGCOM2] Unable to find message-handler for class in function

...

Example:
CLIPS> (ppdefmessage-handler USER foo around)

[MSGCOM3] Unable to delete message-handlers
...

Example:

CLIPS>
CLIPS>
CLIPS>
TRUE
CLIPS>
TRUE

(defclass FOO (is-a USER) (role concrete))
(defmessage-handler FOO bar ())
(bsave foo
...
bin)

CLIPS Basic Programming Guide

357

CLIPS Reference Manual
CLIPS> (undefmessage-handler FOO bar)

[MSGFUN1] No applicable primary message-handlers found for
...

Example:
CLIPS> (defclass A (is-a USER))
CLIPS> (make-instance a of A)
[a]
CLIPS> (send [a] bogus-message)

[MSGFUN2] Message-handler in class expected exactly/at least
argument(s)
...

Example:

CLIPS>
CLIPS>
CLIPS>
[a]
CLIPS>

(defclass A (is-a USER))
(defmessage-handler USER foo (?a ?b))
(make-instance a of A)
(send [a] foo)

[MSGFUN3] slot in instance : write access denied
...

Example:

CLIPS>
(defclass A (is-a USER)
(slot foo (default 100)
(read-only)))
CLIPS> (make-instance a of A)
[a]
CLIPS> (send [a] put-foo)

[MSGFUN4] may only be called from within message-handlers
...

Example:
CLIPS> (ppinstance)

[MSGFUN5] operates only on instances
...

Example:

CLIPS>
(defmessage-handler INTEGER print ()

358

Appendix G - CLIPS Error Messages

CLIPS Reference Manual
(ppinstance))
CLIPS> (send 34 print)

[MSGFUN6] Private slot of class cannot be accessed directly by
handlers attached to class
A subclass which inherits private slots from a superclass may not access those slots using the
?self variable
...

Example:

CLIPS> (defclass FOO (is-a USER) (role concrete) (slot x))
CLIPS> (defclass BAR (is-a FOO))
CLIPS> (defmessage-handler BAR yak () ?self:x)

[MSGFUN7] Unrecognized message-handler type in defmessage-handler
...

Example:
CLIPS> (defmessage-handler USER foo behind ())

[MSGFUN8] Unable to delete message-handler(s) from class
...

Example:
CLIPS> (reset)
CLIPS>
(defmessage-handler INITIAL-OBJECT error ()
(undefmessage-handler INITIAL-OBJECT error primary))
CLIPS> (send [initial-object] error)

[MSGPASS1] Shadowed message-handlers not applicable in current context
...

Example:
CLIPS> (call-next-handler)

[MSGPASS2] No such instance in function
...

Example:

CLIPS> (instance-address [bogus-instance])

CLIPS Basic Programming Guide

359

CLIPS Reference Manual

[MSGPASS3] Static reference to slot of class does not apply to
of
...

Static slot references always refer to the slot defined in the class to which the message-handler is
attached
...

A message-handler can only be attached to an existing class
...

No message-handlers for a class can be loaded while any current message-handlers attached to
the class are executing
...

There are four primary message-handlers attached to the class USER which cannot be modified:
init, delete, create and print
...

Direct slot references are allowed only within message-handler bodies
...

?self is a reserved parameter for the active instance
...

The symbol following the ?self: reference must be a valid slot for the class
...

The symbol following the ?self: reference must be a symbol
...

Message-handlers cannot be attached to the INSTANCE, INSTANCE-ADDRESS, or
INSTANCE-NAME classes
...
in function
or
[MULTIFUN1] Multifield index range
...
in
function
This error occurs when a multifield manipulation function is passed a single index or range of
indices that does not fall within the specified range of allowed indices
...

The field variable (if specified) cannot be rebound within the body of the progn$ function
...

No objects of existing classes could possibly satisfy the pattern
...

Example:
CLIPS> (defclass A (is-a INITIAL-OBJECT) (slot foo))
CLIPS> (defrule error (object (foo ?) (is-a ~A)) =>)

[OBJRTBLD2] No objects of existing classes can satisfy restriction in
object pattern
...

Example:

CLIPS> (defrule error (object (bad-slot ?)) =>)

[OBJRTBLD3] No objects of existing classes can satisfy pattern #
...
This error occurs when the
constraints for a slot as given in the defclass(es) are incompatible with the constraints imposed
by the pattern
...

Only one restriction per attribute is allowed per object pattern
...

Object patterns are applicable only to classes of objects which are already defined
...
The specific pattern and field of the problem rules are identified
...

Certain keywords have special meaning to CLIPS and may not be used in situations that would
cause an ambiguity
...

Example:

CLIPS> (defrule foo (a ?x $?y ?x&~$?y) =>)

[PRCCODE1] Attempted to call a which does not exist
...

[PRCCODE2] Functions without a return value are illegal as arguments
...

Example:
CLIPS> (defmethod foo (?a))
CLIPS> (foo (instances))

CLIPS Basic Programming Guide

363

CLIPS Reference Manual

[PRCCODE3] Undefined variable referenced in
...

Example:

CLIPS> (defrule foo => (+ ?a 3))

[PRCCODE4] Execution halted during the actions of
...

[PRCCODE5] Variable unbound [in ]
...

Example:

CLIPS> (deffunction foo () (bind ?a) ?a)
CLIPS> (foo)

[PRCCODE6] This error occurred while evaluating arguments for the

...

Example:
CLIPS> (deffunction foo (?a))
CLIPS> (foo (+ (eval "(gensym)") 2))

[PRCCODE7] Duplicate parameter names not allowed
...

Example:
CLIPS> (defmethod foo ((?x INTEGER) (?x FLOAT)))

[PRCCODE8] No parameters allowed after wildcard parameter
...

Example:

CLIPS> (defmethod foo (($?x INTEGER) (?y SYMBOL)))

[PRCDRPSR1] Cannot rebind count variable in function loop-for-count
...

Example:
364

Appendix G - CLIPS Error Messages

CLIPS Reference Manual
CLIPS> (loop-for-count (?count 10) (bind ?count 3))

[PRCDRPSR2] The return function is not valid in this context
...

The return and break functions can only be used within certain contexts (e
...
the break function
can only be used within a while loop and certain instance set query functions)
...

A case may be specified only once in a switch statement
...

[PRNTUTIL2] Syntax Error: Check appropriate syntax for
This error occurs when the appropriate syntax is not used
...

This error may have occurred from errors in user defined code
...
If the problem cannot be located within user defined code,
then the should be reported
...
g
...

One example which will cause this error is an attempt to delete a deffunction or generic function
which is used in another construct (such as the RHS of a defrule or a default-dynamic facet of a
defclass slot)
...

This error occurs when CLIPS has already parsed an attribute or declaration
...

This error occurs when a local variable is used by a function or construct that cannot use global
variables
...

This error occurs when a function attempts to divide by zero
...

Example:
CLIPS> (printout "Hello" crlf)

[RULECSTR1] Variable in CE # slot
has constraint conflicts which make the pattern unmatchable
...

or
[RULECSTR1] CE # slot
has constraint conflicts which make the pattern unmatchable
...

This error occurs when slot value constraints (such as allowed types) prevents any value from
matching the slot constraint for a pattern
...

This error occurs when previous variable bindings and constraints prevent a variable from
containing a value which satisfies the type constraints for one of a function’s parameters
...

This error occurs when previous variable bindings and constraints prevent a variable from
containing a value which satisfies the type constraints for one of a function’s parameters
...

Logical CEs can be placed outside, but not inside, a not/exists/forall CE
...

Example:
CLIPS> (defrule error (not ?f <- (fact)) =>)

[RULEPSR1] Logical CEs must be placed first in a rule
If logical CEs are used, then the first CE must be a logical CE
...

Example:

CLIPS> (defrule error (logical (a)) (b) (logical (c)) =>)

[STRNGFUN1] Function build does not work in run time modules
...

The build and eval functions do not work in run time modules because the code required for
parsing is not available
...

Local variables cannot be accessed by the eval function
...

Example:
clips -f

[TEXTPRO1] Could not open file
...

Example:

CLIPS> (fetch “bogus
...

If a slot definition is specified in a template pattern or fact, the contents of the slot must be
capable of matching against or evaluating to a single value
...

Fact indexes may only be used with the modify and duplicate commands when the command is
issued from the top-level command prompt
...

A multifield value cannot be stored in a single field slot
...

The (default ?NONE) attribute requires that a slot value be supplied whenever a new fact is
created
...
3
...
3
...
3
...
3
...
3
...
-name>

::= A < sy mb o l> wh er e t h e e l li ps i s
in d ic at e w h at t h e s y mb o l re p re s en ts
...


Variables and Expressions
::= ?


CLIPS Basic Programming Guide

::= $?

371

CLIPS Reference Manual


::= ?**



::= |
|




::= ( *)



::= | |




::=

<
...
F or e xa m pl e,
s h ou l d
re t ur n a n i nt eg er
...
They should be considered reserved function names, and users should not create
user-defined functions with any of these names
...
, and Riley, G
...

Gonzalez, A
...
, and Dankel, D
...
Engineering of Knowledge-basedSystems: Theory and
Practice, Prentice Hall, 1993
...
Introduction to Expert Systems, 3rd Edition, Reading, Addison-Wesley, 1998
...
“The Art of Production Systems,” AI Expert, January 1992
...
“Software Review,” AI Expert, April 1988
...
“Shell Review Monthly,” AI Today, March/April 1988
...
“A Comparative Evaluation of Expert System Tools,” Computer, February 1991
...
“CLIPS: NASA’s COSMIC Shell,” Artificial Intelligence Research, August 1,
1988
...
“Two PC–based Expert System Shells for the First–time Developer,” Computer,
November 1988
...
, et al
...

Riley, G
...
Edited by A
...
G
...
New York, Marcel Dekker,
Inc
...

Riley, G
...
Edited by
J
...
Irwin
...

Riley, G
...

Riley, G
...

CLIPS Basic Programming Guide

385

CLIPS Reference Manual

Riley G
...
“Advanced CLIPS Capabilities,” Proceedings of The Fourth Annual
Workshop on Space Operations Applications and Research (SOAR ’90), Albuquerque, NM, June
1990
...
, et al
...

Riley, G
...
, “CLIPS: An Expert System Tool for Delivery and Training,” Proceedings of the
Third Conference on Artificial Intelligence for Space Applications, Huntsville, AL, November
1987
...
A
...
A
...

Cheatham, J
...
, et al
...

Chen, Y
...
C
...

“CLIPS: A NASA Developed Expert System Tool,” NASA Tech Briefs, November/December
1987
...
“HUB SIAASHING: A Knowledge–Based System for Severe, Temporary Airline
Schedule Reduction,” Innovative Applications of Artificial Intelligence 4, Klahr, Philip, and
Scott, A
...
, 1992
...
B
...
S
...

Fink, P
...
T
...

Fink, P
...

Flamm, R
...
, et al
...
2, 1991
...
, et al
...
C
...
, et al
...
1, Spring, 1994
...
, et al
...

Germain, D
...
“Turning Up the Heat on Space Station Training: The Active
Thermal Control System ICAT,” Proceedings of Contributed Sessions 1991 Conference on
Intelligent Computer Aided Training, Houston, TX, November 1991
...
G
...
“Virtual Environment Architecture for Rapid Application Development,”
Proceedings of The Contributed Sessions 1993 Conference on Intelligent Computer Aided
Training and Virtual Environment Technology (ICAT-VET ’93), Houston, TX, May 1993
...
, et al
...

Hill, T
...
“Intelligent Fault Management for the Space Station Active Thermal
Control System,” Proceedings of The Fifth Annual Workshop on Space Operations Applications
and Research (SOAR ’91), Houston, TX, July 1991
...
P
...
S
...

Hughes, P
...
“CLEAR: Automating Control Centers with Expert System Technology,”
Proceedings of The Third Annual Workshop on Space Operations Automation and Robotics
(SOAR ’89), Houston, TX, July 1989
...
B
...
“An Intelligent Tutoring System for Space Shuttle Diagnosis,”
Proceedings of The Second Annual Workshop on Space Operations Automation and Robotics
(SOAR ’88), Albuquerque, NM, July 1988
...
G
...
“An Expert System for Culture-Based Infection Control Surveillance,”
Proceedings of The Seventeenth Annual Symposium on Computer Applications in Medical Care
(SCAMC ’93), Washington, D
...
, October 1993
...
“Pragmatic KADS: A methodological approach to a small knowledge based systems
project,” Expert Systems: The International Journal of Knowledge Engineering, 4, 4, November
1992
...
P
...
D
...

Kosta, C
...
, and Krolak, P
...
“An Artificial Reality Environment for Remote Factory Control
and Monitoring,” Vision 21: Interdisciplinary Science and Engineering in the Era of
Cyberspace, NASA/Lewis Research Center, December 1993
...
J
...

Lauriente, M
...
“Diagnosing Anomalies of Spacecraft for Space Maintenance and
Servicing,” Proceedings of The Seventh Annual Workshop on Space Operations Applications
and Research (SOAR ’93), Houston, TX, August 1993
...
, and Hill, R
...
, “Process Control and Recovery in the Link Monitor and Control
Operator Assistant,” Proceedings of The Sixth Annual Workshop on Space Operations
Applications and Research (SOAR ’92), Houston, TX, August 1992
...
“Finance,” Expert Systems and Artificial Intelligence: Applications and
Management, Howard W
...
C
...
, 1988
...
C
...
“The Application of Integrated Knowledge–Based Systems for the
Biomedical Risk Accessment Intelligent Network (BRAIN),” Proceedings of Technology 2002:
The Third National Technology Transfer Conference and Exposition, Washington D
...
,
February 1993
...
B
...
T
...

Loftin, R
...
, et al
...

Loftin, R
...
, et al
...

Lucas, T
...
, and Lewis, G
...


388

Appendix J - Bibliography of CLIPS Publications

CLIPS Reference Manual

McCarthy, L
...
“Spatial Considerations for Instructional Development in a Virtual
Environment,” Proceedings of The Contributed Sessions 1993 Conference on Intelligent
Computer Aided Training and Virtual Environment Technology (ICAT-VET ’93), Houston, TX,
May 1993
...

Mitchell, P
...

Mitchell, R
...

Mortenson, P
...

Mueller, S
...

Muratore, J
...
“Space Shuttle Telemetry Monitoring,” Innovative Applications of Artificial
Intelligence, 1989, AAAI Press/The MIT Press, Menlo Press, Schoor, Herbert, and Rappaport,
Alain ed
...
“Expert Systems: A New Partnership,” AI Expert, December 1992
...
E
...
“Microcomputer Intelligence for Technical Training (MITT): The Evolution
of an Intelligent Tutoring System,” Proceedings of Contributed Sessions 1991 Conference on
Intelligent Computer Aided Training, Houston, TX, November 1991
...

Proceedings of the Second CLIPS Conference, Houston, Texas, September 1991
...

Robey, B
...
“The DRAIR Advisor: A Knowledge–Based System for Materiel Deficiency
Analysis,” Proceedings of the Fifth Innovative Applications of Artificial Intelligence Conference,
July 11–15, 1993, Washington, D
...

Robey, B
...
“DRAIR Advisor: A Knowledge-Based System for Materiel-Deficiency
Analysis,” AI magazine, Volume 15, No
...

Rolincik, M, et al
...


CLIPS Basic Programming Guide

389

CLIPS Reference Manual

Rolincik, M
...
“An Expert System for Diagnosing Environmentally Induced Spacecraft
Anomolies,” Proceedings of The Fifth Annual Workshop on Space Operations Applications and
Research (SOAR ’91), Houston, TX, July 1991
...
, et al
...

Saito, T
...
“On the Acquisition and Representation of Procedural Knowledge,” Proceedings
of The Fifth Annual Workshop on Space Operations Applications and Research (SOAR ’91),
Houston, TX, July 1991
...
“The State Transition Diagram with Path Priority and it’s Applications,” M
...
Thesis,
Naval Postgraduate School, Monterey, CA, September 1993
...
D, and Stobie, I
...

Spelt, P
...
“Learning by an Autonomous Robot at a Process Control Panel,” IEEE Expert,
Winter 1989
...
88, 102, 120–121, 1994
...
121, 1993
...
110–111, 1992
...
, et al
...

Szatkowski, G
...
, and Levin, B
...
“Expert System Decision Support for Low–cost Launch
Vehicle Operations,” Proceedings of The Fourth Annual Workshop on Space Operations
Applications and Research (SOAR ’90), Albuquerque, NM, June 1990
...
“Advances in Knowledge–Based Software Engineering,” Proceedings of the
Technology 2001Conference, San Jose, CA, December 1991
...
K
...

Wang, L
...
“Space Shuttle Onboard Navigation Console Expert/Trainer
System,” Proceedings of The First Annual Workshop on Space Operations Automation and
Robotics (SOAR ’87), Houston, TX, August 1987
...
C
...
A
...

Wiederholt, B
...
“MITT Writer: An Authoring System for Developing Intelligent Tutors for
Complex Technical Domains,” Proceedings of Contributed Sessions 1991 Conference on
Intelligent Computer Aided Training, Houston, TX, November 1991
...
“Space Station Freedom: Embedding AI,” AI Expert, April 1992
...
, “Object/rule Integration in CLIPS,” Expert Systems: The International Journal of
Knowledge Engineering and Neural Networks, Learned Information, New Jersey, February
1994, Vol
...
1, ISSN 0266-4720, pp
...

Franke, J
...
, et al
...

Le, T
...
“Portable Inference Engine: An Extended CLIPS for Real–Time
Production Systems,” Proceedings of The Second Annual Workshop on Space Operations
Automation and Robotics (SOAR ’88), Albuquerque, NM, July 1988
...
P
...

Odette, L
...
, Intelligent Embedded Systems, Addison–Wesley Publishing Company, pp
...

Riley, G
...

Riley, G
...

Salzgeber, M
...
, et al
...

Eick, C
...
, et al
...

CLIPS Basic Programming Guide

391

CLIPS Reference Manual

Rete Pattern Matching Algorithm
Forgy, C
...
17–37, 1982
...
“On the Efficient Implementation of Production Systems,” Ph
...
Thesis,
Carnegie-Mellon University, 1979
...
“The Rete Matching Algorithm,” AI Expert, pp
...


392

Appendix J - Bibliography of CLIPS Publications

CLIPS Reference Manual

Index

-
...
7
&
...
7
)
...
179
**
...
180
:
...
7
?DERIVE
...
22
?self
...
7, 40
~
...
178
<
...
156
<>
...
45, 154
=>
...
155
>=
...
181
abstraction
...
183
acosh
...
183
acoth
...
183
acsch
...
15, 27, 151
activated
...
82, 111, 125
active-initialize-instance
...
82, 116, 117
active-message-duplicate-instance
...
82, 111, 124
CLIPS Basic Programming Guide

active-modify-instance
...
iv, 7, 9, 15
Advanced Programming Guide iv, v, 1, 3, 5,
8, 50, 153, 168, 182, 285
agenda
...
146
allowed-instance-names
...
147
ampersand
...
156
antecedent
...
215, 302
any-instancep
...
255
arrow
...
iii
Artificial Intelligence Section
...
183
asech
...
183
asinh
...
11, 22, 82, 198, 203, 206, 247, 311
assert-string
...
183
atanh
...
22
auto-focus
...
7, 170, 175, 176, 206
Basic Programming Guide
...
3, 4, 252
batch*
...
38, 67, 82, 107, 120, 187
bload
...
284, 285
break
...
278
bsave
...
284
build
...
iii, 7, 9, 12, 15, 16, 21
call-next-handler
...
81, 82, 85, 224, 225
call-specific-method
...
7
case sensitive
...
167, 307
class
...
87, 92, 235, 276
concrete
...
227
immediate
...
92
precedence
...
88, 92, 235
specific
...
87
ADDRESS
...
87
FACT-ADDRESS
...
87
INITIAL-OBJECT
...
87
INSTANCE-ADDRESS
...
87
INTEGER
...
87
MULTIFIELD
...
87
OBJECT
...
87
STRING
...
87
USER
...
8, 282
user-defined
...
223, 240
class-abstractp
...
228
class-reactivep
...
231
394

class-subclasses
...
230
clear11, 25, 67, 118, 137, 139, 143, 250, 251
clear-focus-stack
...
iii
CLIPSFunctionCall
...
75, 87
close
...
3, 151, 249
command prompt
...
7, 10
Common Lisp Object System
...
15
conditional element
...
27, 33, 52
exists
...
33, 56
logical
...
33, 53
or
...
27, 33
initial-fact
...
27, 52, 53
literal
...
30, 33, 49
conflict resolution strategy
...
29
complexity
...
29
lex
...
31
random
...
29
consequent
...
235
conserve-mem
...
3, 8
constraint
...
34, 40
field
...
34
predicate
...
34, 45
construct
...
293
constructs-to-c
...
235
COOL
...
183
cosh
...
183
coth
...
157
crlf
...
183
csch
...
108, 116, 131
deactivated
...
85, 103, 114
declare
...
22
defclass
...
227
deffacts
...
218
deffunction
...
74
advantages over generic functions
...
74
recursion
...
73
return value
...
73
deffunction-module
...
9, 10, 75, 76
defgeneric-module
...
10, 14, 67, 271
defglobal-module
...
10, 14, 88, 117, 281
initial-object
...
238
defmessage-handler
...
9, 10, 75, 76
CLIPS Basic Programming Guide

defmodule
...
17
defrule
...
219
deftemplate
...
12, 21, 205
deftemplate-module
...
199, 300
deftemplate-slot-cardinality
...
200, 300
deftemplate-slot-default-value
...
201, 300
deftemplate-slot-multip
...
201, 300
deftemplate-slot-range
...
202, 300
deftemplate-slot-type
...
203
deg-grad
...
184
delayed-do-for-all-facts
...
159
delete-instance
...
163, 309
delimiter
...
267
dependents
...
90, 276
direct-insert$
...
180
do-for-all-facts
...
82, 133, 135, 192, 305
do-for-fact
...
82, 133, 134, 192, 305
double quote
...
255
dribble-on
...
11, 13, 23, 82, 205, 247
duplicate-instance
...
18
dynamic-get
...
120, 242, 359
edit
...
5
encapsulation
...
302
EnvTrueSymbol
...
171, 172, 177
eq
...
165, 303
evenp
...
4, 170, 251, 309
exp
...
82, 105, 247, 302
explode$
...
6
exporting constructs
...
10
external-address
...
4
-f2
...
88, 93, 276
access
initialize-only
...
95
read-write
...
100, 235, 304
?NONE
...
100
read-write
...
100
default
...
93
multislot
...
101
pattern-match
non-reactive
...
98
propagation
inherit
...
92, 96
shared
...
93
slot
...
92, 97
exclusive
...
94
shared
...
99
private
...
99
fact
...
11
fact-address
...
207, 310
fact-index
...
11, 13, 25, 27
fact-relation
...
259
fact-set
...
213
distributed action
...
211
member variable
...
212, 213
query execution error
...
214
template
...
211
fact-slot-names
...
208, 310
FALSE
...
302
fetch
...
171, 309
field
...
216, 217, 302
find-all-instances
...
215, 302
find-instance
...
27
first$
...
6, 8, 182
floatp
...
28, 65, 143, 269
Index

CLIPS Reference Manual

format
...
9
funcall
...
3, 9, 16, 75, 132, 151, 213
call
...
5, 38, 45, 50
predicate
...
379
system defined
...
7, 9, 50, 365
generic dispatch
...
14, 16, 75, 273
disadvantages
...
76, 77
order dependence
...
329
performance penalty
...
85
gensym
...
116, 124, 195
get-auto-float-dividend
...
176, 300
get-class-defaults-mode
...
245
get-defclass-list
...
218
get-deffunction-list
...
222
get-defglobal-list
...
303
get-definstances-list
...
231
get-defmethod-list
...
244
get-defrule-list
...
203
get-dynamic-constraint-checking
...
261
get-fact-list
...
219
get-focus-stack
...
81, 197
get-incremental-reset
...
82, 226
GetNextFactInTemplate
...
310
GetNthWatchValue
...
293
get-region
...
272
get-salience-evaluation
...
248
get-static-constraint-checking
...
269
grad-deg
...
269
help
...
287
I/O router
...
82, 189, 247
if portion
...
85, 103, 114
implode$
...
139
incremental reset
...
iii
inference engine
...
14, 18, 88, 92
class precedence list
...
103
is-a
...
14, 18, 87, 89, 90, 278
initial-fact pattern
...
82, 94, 101, 108, 118, 239
initial-object pattern
...
108, 116, 119, 239
insert$
...
8, 13, 14, 92, 94, 276, 282
active
...
112, 115
deletion
...
87, 88, 92, 96
initialization
...
115
printing
...
6, 8, 9, 49, 171, 240, 241,
329
instance-addressp
...
242
instance-list
...
6, 8, 129, 240, 241
instance-namep
...
241
instancep
...
282
instance-set
...
132
class restriction
...
131
member
...
129, 132
query
...
132
query functions
...
128
integer
...
151
integration
...
v, 3
-l
...
15
length
...
93, 105, 162, 196
less than
...
152
LHS
...
7
LISP
...
276
list-deffacts
...
272
list-defgenerics
...
271
list-definstances
...
280
list-defmethods
...
285
list-defrules
...
258
list-focus-stack
...
257
load
...
249, 310
load-facts
...
304
load-instances
...
260
log
...
186
logical name
...
171, 173
stdin
...
169, 171, 173, 255
t
...
169, 255
wdialog
...
169, 255
werror
...
169, 255
wwarning
...
58, 204, 205, 267
loop-for-count
...
166
make-instance
...
63, 264
math functions
...
181
max-number-of-elements
...
158, 303, 309
mem-requests
...
285
message
...
104
execution error
...
114
Index

CLIPS Reference Manual

implementation
...
115
message dispatch
...
82, 101, 112, 125
message-handler
...
106
applicability
...
102
existence
...
102
regular parameter
...
115
shadow
...
112, 113, 115
system
create
...
109, 116, 117, 121, 124
direct-duplicate
...
110, 122, 123
init
...
112, 125, 126
message-modify
...
110
type
after
...
103, 113, 114, 115, 236
before
...
103, 113, 114, 115
wildcard parameter
...
229
message-modify-instance
...
16, 75, 76, 87
action
...
79, 85, 275
execution error
...
75, 79, 81
implicit
...
75
index
...
78
CLIPS Basic Programming Guide

parameter restriction
...
78
precedence
...
78, 79
return value
...
85, 224, 280
wildcard parameter
...
76
MicroEMACS editor
...
181
min-number-of-elements
...
187
modify
...
82, 110, 122
module specifier
...
8, 9
multifield wildcard
...
153
named fields
...
iii
neq
...
82, 236, 237
next-methodp
...
43
non-ordered fact
...
157
nth$
...
151
object
...
13, 16, 17, 18, 75, 88, 103
primitive type
...
13, 14, 17, 18, 88
reference
...
47, 82, 121, 247,
313
oddp
...
293
open
...
30
options
...
157
ordered fact
...
9, 16, 73, 75, 76, 328
override-next-handler
...
81, 82, 85, 225
parenthesis
...
12, 16, 21
pattern
...
27
pattern-address
...
15, 67, 68
performance
...
185
pointerp
...
18
pop-focus
...
154, 155, 156, 175
mathematical functions
...
176
rename
...
253
time
...
275
ppdeffacts
...
272
ppdefgeneric
...
271
ppdefinstances
...
279
ppdefmethod
...
285
ppdefrule
...
258
ppfact
...
283
pprule
...
10
preview-generic
...
281
printout
...
290
profile
...
292, 293
profile-reset
...
82, 121, 131, 191, 192, 247, 294, 305
progn$
...
7
rad-deg
...
195, 305
read
...
169, 172, 252
read-number
...
v, vii
refresh
...
270, 313
release-mem
...
175
remove-break
...
175
replace$
...
163, 309
reset
...
162
restore-instances
...
327
retract
...
28, 82, 133, 143, 190, 192, 214, 247,
313, 314
RHS
...
15
round
...
6
RtnArgCount
...
15, 27
run
...
28, 29, 64, 270
dynamic
...
250, 286, 303
save-facts
...
283, 284
scientific math functions
...
183
sech
...
33, 196
semicolon
...
17, 18, 103, 112, 114, 115, 280, 311,
329
sequence expansion
...
153
set-auto-float-dividend
...
265
set-class-defaults-mode
...
139, 245, 268
set-dynamic-constraint-checking
...
260
setgen
...
267
set-locale
...
292
set-reset-globals
...
64, 270, 314
set-sequence-operator-recognition
...
23, 101, 145,
254
set-strategy
...
266
show-defglobals
...
6
sin
...
8
single-field wildcard
...
183
slot
...
95, 100, 228, 229
accessor
...
116
default value
...
106, 120, 131, 188
existence
...
93, 97
inheritance propagation
...
242
overlay
...
96
visibility
...
329
slot-allowed-classes
...
234
slot-cardinality
...
235, 310
slot-delete$
...
229
slot-direct-delete$
...
243
slot-existp
...
232
slot-initablep
...
93, 243
slot-override
...
229
slot-range
...
243
slot-sources
...
233, 313
slot-writablep
...
iv, 75, 87
sort
...
7
specificity
...
185
standard math functions
...
163
str-compare
...
164
string
...
152
string-to-field
...
167
subclass
...
228
subseq$
...
158
sub-string
...
88, 89, 92, 103, 228, 276
direct
...
228
switch
...
6, 7, 8, 240, 241
reserved
...
12
declare
...
12
forall
...
12
not
...
12
or
...
12
symbolp
...
240
sym-cat
...
253
tab
...
183
tanh
...
205
then portion
...
7
time
...
198
timer
...
3
toss
...
182
TrueSymbol
...
58
type function
...
58
undefclass
...
262
undeffunction
...
274
undefglobal
...
282

402

undefmessage-handler
...
274
undefrule
...
259
unmake-instance
...
257, 310
upcase
...
v, vii
user-functions
...
9
variable
...
3, 14, 64, 67, 188, 251
vertical bar
...
260
vtab
...
255, 257, 313
watch item
activations
...
257
compilations
...
256
facts
...
256
generic-functions
...
67, 256
instances
...
257
messages
...
256
rules
...
257
statistics
...
82, 190, 247, 314
wildcard
...
152

Index



---

Title: Clips (Artificial Intelligence)
Description: In subject of (Artificial Intelligence) in computer science Defination of CLIPS

Buy These NotesPreview