On Jun 11, 2007, at 3:24 AM, Wolfgang Laun wrote:
The following Jess program uses working memory elements as slot
values, and this one doesn't fire the rule crossover, although I
think it should.
....
(defrule crossover
?e <- (side (name ?ename) {occup == FALSE})
?w <- (side (name ?wname) {occup == TRUE})
?br <- (bridge (name ?bname){occup == FALSE}
(east $east){east == ?e}
(west $west){west == ?w})
=>
(printout t ?bname " " ?ename " " ?wname crlf)
)
Unfortunately these "simple patterns" have confusing semantics, so
they're being redefined somewhat for Jess 7.1. The confusing thing is
that a name like "occup" in the above represents a variable that is
bound automatically to the value of the first slot in which its used.
If you use the same name later in the rule, that variable represents
a unification -- i.e., the same value. Therefore it works just the
same as variables in the regular Jess syntax; unfortunately this
syntax makes it easy to believe otherwise. Anyway, the rule above can
never fire, as it requires that the same variable be both TRUE and
FALSE.
---------------------------------------------------------
Ernest Friedman-Hill
Advanced Software Research Phone: (925) 294-2154
Sandia National Labs FAX: (925) 294-2234
PO Box 969, MS 9012 [EMAIL PROTECTED]
Livermore, CA 94550 http://www.jessrules.com
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