CLIPS - Programming language

CLIPS, aka C Language Integrated Production System, is a programming language created in 1985.

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CLIPS is a public domain software tool for building expert systems. The name is an acronym for "C Language Integrated Production System." The syntax and name was inspired by Charles Forgy's OPS ("Official Production System," although there was nothing really official about it). The first versions of CLIPS were developed starting in 1985 at NASA-Johnson Space Center (as an alternative for existing system ART*Inference) until the mid-1990s when the development group's responsibilities ceased to focus on expert system technology. Read more on Wikipedia...

Tags: programming language
There are at least 1,638 CLIPS repos on GitHub
Early development of CLIPS happened in NASA
The Google BigQuery Public Dataset GitHub snapshot shows 901 users using CLIPS in 991 repos on GitHub
Explore CLIPS snippets on Rosetta Code
CLIPS on HOPL
GitHub supports syntax highlighting for CLIPS
clipsrules.net was registered in 2016
See also: (5 related languages) OPS5, C, Lisp, Java, ISBN

Example from the web:

 (deftemplate car_problem
     (slot name)
     (slot status))

 (deffacts trouble_shooting
     (car_problem (name ignition_key) (status on))
     (car_problem (name engine) (status wont_start))
     (car_problem (name headlights) (status work)))

 (defrule rule1
     (car_problem (name ignition_key) (status on))
     (car_problem (name engine) (status wont_start))
      =>
     (assert (car_problem (name starter) (status faulty))))

Example from hello-world:

(defrule hw
    (f ?x)
=>
    (printout t ?x crlf))

(assert (f "Hello World"))

(run)

Example from Linguist:

;;; http://www.angusj.com/sudoku/hints
;;; http://www.scanraid.com/BasicStrategies.htm
;;; http://www.sudokuoftheday.com/pages/techniques-overview
;;; http://www.sudokuonline.us/sudoku_solving_techniques
;;; http://www.sadmansoftware.com/sudoku/techniques.htm
;;; http://www.krazydad.com/blog/2005/09/29/an-index-of-sudoku-strategies/

;;; #######################
;;; DEFTEMPLATES & DEFFACTS
;;; #######################

(deftemplate possible
   (slot row)
   (slot column)
   (slot value)
   (slot group)
   (slot id))
   
(deftemplate impossible
   (slot id)
   (slot value)
   (slot priority)
   (slot reason))
   
(deftemplate technique-employed
   (slot reason)
   (slot priority))

(deftemplate technique
   (slot name)
   (slot priority))
   
(deffacts startup
   (phase grid-values))

(deftemplate size-value
   (slot size)
   (slot value))
   
(deffacts values
   (size-value (size 1) (value 1))
   (size-value (size 2) (value 2))
   (size-value (size 2) (value 3))
   (size-value (size 2) (value 4))
   (size-value (size 3) (value 5))
   (size-value (size 3) (value 6))
   (size-value (size 3) (value 7))
   (size-value (size 3) (value 8))
   (size-value (size 3) (value 9))
   (size-value (size 4) (value 10))
   (size-value (size 4) (value 11))
   (size-value (size 4) (value 12))
   (size-value (size 4) (value 13))
   (size-value (size 4) (value 14))
   (size-value (size 4) (value 15))
   (size-value (size 4) (value 16))
   (size-value (size 5) (value 17))
   (size-value (size 5) (value 18))
   (size-value (size 5) (value 19))
   (size-value (size 5) (value 20))
   (size-value (size 5) (value 21))
   (size-value (size 5) (value 22))
   (size-value (size 5) (value 23))
   (size-value (size 5) (value 24))
   (size-value (size 5) (value 25)))
   
;;; ###########
;;; SETUP RULES
;;; ###########

;;; ***********
;;; stress-test
;;; ***********

(defrule stress-test
   
   (declare (salience 10))
   
   (phase match)
   
   (stress-test)
   
   (priority ?last)
   
   (not (priority ?p&:(> ?p ?last)))
   
   (technique (priority ?next&:(> ?next ?last)))
   
   (not (technique (priority ?p&:(> ?p ?last)&:(< ?p ?next))))
   
   =>
   
   (assert (priority ?next)))
   
;;; *****************
;;; enable-techniques
;;; *****************

(defrule enable-techniques

   (declare (salience 10))
   
   (phase match)
   
   (size ?)
   
   (not (possible (value any)))
   
   =>
   
   (assert (priority 1)))

;;; **********
;;; expand-any
;;; **********

(defrule expand-any

   (declare (salience 10))

   (phase expand-any)
   
   ?f <- (possible (row ?r) (column ?c) (value any) (group ?g) (id ?id))
  
   (not (possible (value any) (id ?id2&:(< ?id2 ?id))))
   
   (size ?s)
   
   (size-value (size ?as&:(<= ?as ?s)) (value ?v))
   
   (not (possible (row ?r) (column ?c) (value ?v)))
  
   (not (and (size-value (value ?v2&:(< ?v2 ?v)))
               
             (not (possible (row ?r) (column ?c) (value ?v2)))))
   
   =>
   
   (assert (possible (row ?r) (column ?c) (value ?v) (group ?g) (id ?id))))
   
;;; *****************
;;; position-expanded
;;; *****************

(defrule position-expanded

   (declare (salience 10))

   (phase expand-any)
   
   ?f <- (possible (row ?r) (column ?c) (value any) (group ?g) (id ?id))
     
   (size ?s)
   
   (not (and (size-value (size ?as&:(<= ?as ?s)) (value ?v))
   
             (not (possible (row ?r) (column ?c) (value ?v)))))

   =>
   
   (retract ?f))
   
;;; ###########
;;; PHASE RULES
;;; ###########

;;; ***************
;;; expand-any-done
;;; ***************

(defrule expand-any-done

   (declare (salience 10))

   ?f <- (phase expand-any)

   (not (possible (value any)))
   
   =>
   
   (retract ?f)
   
   (assert (phase initial-output))
   (assert (print-position 1 1)))
   
;;; ***********
;;; begin-match
;;; ***********

(defrule begin-match

   (declare (salience -20))
   
   ?f <- (phase initial-output)
      
   =>
   
   (retract ?f)
   
   (assert (phase match)))

;;; *****************
;;; begin-elimination
;;; *****************

(defrule begin-elimination

   (declare (salience -20))
   
   ?f <- (phase match)
   
   (not (not (impossible)))
   
   =>
   
   (retract ?f)
   
   (assert (phase elimination)))

;;; *************
;;; next-priority
;;; *************

(defrule next-priority

   (declare (salience -20))
   
   (phase match)
   
   (not (impossible))
   
   (priority ?last)
   
   (not (priority ?p&:(> ?p ?last)))
   
   (technique (priority ?next&:(> ?next ?last)))
   
   (not (technique (priority ?p&:(> ?p ?last)&:(< ?p ?next))))
   
   =>
   
   (assert (priority ?next)))

;;; ************
;;; begin-output
;;; ************

(defrule begin-output

   (declare (salience -20))
   
   ?f <- (phase match)
   
   (not (impossible))
   
   (priority ?last)
   
   (not (priority ?p&:(> ?p ?last)))

   (not (technique (priority ?next&:(> ?next ?last))))
   
   =>
   
   (retract ?f)
   
   (assert (phase final-output))
   (assert (print-position 1 1)))

Example from Wikipedia:

(deftemplate car_problem
     (slot name)
     (slot status))

 (deffacts trouble_shooting
     (car_problem (name ignition_key) (status on))
     (car_problem (name engine) (status wont_start))
     (car_problem (name headlights) (status work)))

 (defrule rule1
     (car_problem (name ignition_key) (status on))
     (car_problem (name engine) (status wont_start))
      =>
     (assert (car_problem (name starter) (status faulty))))

Language features

Feature	Supported	Example	Token
Strings	✓	"Hello world"	"
Comments	✓	; A comment
Line Comments	✓	; A comment	;
Semantic Indentation	X

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