Hi,
I have tried the straightforward example below. I define two simple
deftemplates and a rule that compares their slots, which are assumed to
be numeric. Then, I incidentally assert a fact on which I do not define
a value for a slot.
When the rule is evaluated (after the second assertion), I immediately
get an error.
Now, I understand the error. But maybe Jess should be nicer by noticing
that if the comparison cannot be made, then it should simply not fire
the rule (quietly).
Henrique
---
Jess, the Rule Engine for the Java Platform
Copyright (C) 2008 Sandia Corporation
Jess Version 7.1RC1 6/23/2008
Jess> (deftemplate a (slot s))
TRUE
Jess> (deftemplate b (slot s))
TRUE
Jess> (defrule r1 (a (s ?sa)) (b {s < ?sa}) => (printout t "Yes!" crlf))
TRUE
Jess> (assert (a))
<Fact-0>
Jess> (assert (b (s 1)))
Jess reported an error in routine <
while executing (< ?__synth0(1,0,-1) ?sa(0,0,-1))
while executing rule LHS (Node2)
while executing rule LHS (TECT)
while executing (assert (MAIN::b (s 1))).
Message: Not a number: nil.
Program text: ( assert ( b ( s 1 ) ) ) at line 5.
Jess>
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