CODEWITHSUNDEEP
clips
DieGrysWolf
DieGrysWolf

Reputation: 47

Compare one value to another to test if file exists in CLIPS

I'm trying to get user to input a book name, then test if the book exists in the library. If not the program should ask him to enter the book details. But the program sees all input as a new book. Is my comparing the two values wrong or my readline?

Code so far:

(deftemplate book (slot name) (slot author) (slot code))

(deffacts current-lib
  (book (name "Alice in Wonderland") (author Lewis-Carroll) (code CAR))
  (book (name "The Bourne Supremacy") (author Robert-Ludlum) (code LUD)))

(defrule readnew "inputs potential new book details"
=>


(printout t "Enter the name of the book:")
  (bind ?b_name (readline))
  (assert (potential ?b_name)))

(defrule add-book "determine if book already exists otherwise add"
  ?out <- (potential ?newname)
  (and (potential ?newname)
       (not (book (name ?b_name&?newname) (author $?))))
=>
  (printout t "Book is new, please enter the author's name:" crlf)
  (bind ?auth (readline))
  (printout t "Please enter a three letter code for the book:" crlf)
  (bind ?coode (read))
  (assert (book (name ?newname) (author ?auth) (code ?coode)))
  (retract ?out))

Upvotes: 0

Views: 114

Answers (1)

Gary Riley
Gary Riley

Reputation: 10757

You provided code, but not the steps you took to run it so I'll have to guess at the cause of your problem. The simplest explanation would be that you did not issue a reset command to assert the facts in your current-lib deffacts.

I made a few changes to your code. In your current-lib deffacts, the author names should be strings since you're using readline in your add-book rule to get the names. There is also unnecessary code in the conditions of your add-book rule.

         CLIPS (6.31 2/3/18)
CLIPS> 
(deftemplate book 
   (slot name)
   (slot author) (slot code))
CLIPS> 
(deffacts current-lib
   (book (name "Alice in Wonderland") (author "Lewis Carroll") (code CAR))
   (book (name "The Bourne Supremacy") (author "Robert Ludlum") (code LUD)))
CLIPS> 
(defrule readnew
   =>
   (printout t "Enter the name of the book:" crlf)
   (bind ?b_name (readline))
   (assert (potential ?b_name)))
CLIPS> 
(defrule add-book
  ?out <- (potential ?newname)
  (not (book (name ?newname)))
  =>
  (printout t "Book is new, please enter the author's name:" crlf)
  (bind ?auth (readline))
  (printout t "Please enter a three letter code for the book:" crlf)
  (bind ?coode (read))
  (assert (book (name ?newname) (author ?auth) (code ?coode)))
  (retract ?out))
CLIPS>

Now, if you add a book that doesn't exist you'll be ask for the additional information.

CLIPS> (reset)
CLIPS> (run)
Enter the name of the book:
Ringworld
Book is new, please enter the author's name:
Larry Niven
Please enter a three letter code for the book:
RNG
CLIPS>

If you try to add a book that doesn't exist, the add-book rule won't execute.

CLIPS> (reset)
CLIPS> (run)
Enter the name of the book:
Alice in Wonderland
CLIPS>

Upvotes: 1

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