predecessor [Relation]
Purpose
The predecessor relation returns the element which precedes a specified member of an ordered set.
Syntax
predecessor set member1 member2
Domains
The set argument is a concept defined as an ordered set.
The member1 argument is a numeric or symbolic member of set.
Range
The member2 argument is the numeric or symbolic member which immediately precedes member1 in set.
Examples
(defset Level :is (:the-ordered-set 'LOW 'MEDIUM 'HIGH))
(ask (predecessor Level 'HIGH 'MEDIUM)) ==> T
(retrieve ?x (predecessor Level 'MEDIUM ?x)) ==> (LOW)
See Also
Last modified: Jun 1 1995