Mathematical Operations and Logic

Mathematical Operations

• Mathematical operations in CLIPS can be represented in prefix notation, where the operator is written before the operands.
• Examples of mathematical operations include:
• 2*2 => (* 2 2)
• 4/2 => (/ 4 2)
• 1+3 => (+ 1 3)
• 4>3 => (> 4 3)
• 2=2 => (= 2 2)

String Operations

• The str-cat function concatenates its arguments into a single string.
• Example: (str-cat “Micro “ Computer) => “Micro Computer”
• The length function returns the length of a string.
• Example: (length “a b c d”) => 4
• The sub-string function retrieves a portion of a string from another string.

Defining Classes and Instances

• A class can be defined using the defclass function, which specifies the slots and their types.
• Example: (defclass student (is-a USER) (slot name) (slot age) (slot address))
• An instance can be created using the make-instance function, which specifies the class and the values for the slots.
• Example: (make-instance [y1] of student (name ahmed) (age 44) (address tanta))

Rules

• A rule can be defined using the defrule function, which specifies the conditions and actions.
• Example: (defrule r2 => (make-instance [y1] of student (name ahmed) (age 44) (address tanta)) ... )
• Rules can be used to create instances, print messages, and delete instances.
• Example: (defrule delete ?inst => (unmake-instance ?inst) (printout t “this instance was deleted “ ?inst crlf))

Modifying Instances

• An instance can be modified using the send or modify function.
• Example: (send [c1] put-age 30) or (modify-instance c1 (age 30))

I/O System

• A file can be opened using the open function, which specifies the file name and mode.
• Example: (open "d:\text.txt f1 "r")
• The readline function can be used to read a line from a file.
• Example: (bind ?d (readline f1)) (if (eq ?d EOF) then (break)) (printout t ?d crlf)
• The format function can be used to send formatted output to a device.
• Example: (format t "10tHello, World!%" )