The "head" or first field of a fact must be known when a rule is
compiled; it can't be the result of a function call.
I will explain how to do what you're trying to do, without asking why
you're trying to do it. It's very unorthodox, and I can't think of a
case where you'd actually want to do things this way. But the
following ought to work:
(defrule n01
?a <- (solution (bottle wine) (position a))
?b <- (solution (bottle cola) (position b))
(test (and (eq ?a ?*a*) (eq ?b ?*b*)))
=>
(bind ?*status* -1))
Now, given that: why do you need to associate the global ?*a* with the
wine bottle in the first place? I.e., why isn't the following exactly
equivalent?
(defrule n02
(solution (bottle wine) (position a))
(solution (bottle cola) (position b))
=>
(bind ?*status* -1))
n01 is testing many things simultaneously: It's testing the condition
you're interested in, yes, but it's also testing that the wine bottle
is in global ?*a* and the cola bottle in global ?*b*. Why should the
rule care about these last two conditions?
I think Mark Lilly wrote:
[Charset iso-8859-1 unsupported, filtering to ASCII...]
> hi All,
> we had a brain teaser at work and i'm using it to teach myself jess.
>
> I need to be able to compare two instances of facts from the same
> DefTemplate.
>
> I tried:
>
> (deftemplate solution
> (slot position)
> (slot bottle)
> )
>
> (bind ?*a* (assert (solution
> (position a)
> (bottle wine)))
> )
>
> (bind ?*b* (assert (solution
> (position b)
> (bottle cola)))
> )
>
> (defrule n01
> ((call ?*a* getName) (bottle wine))
> ((call ?*a* getName) (position a))
> ((call ?*b* getName) (bottle cola))
> ((call ?*b* getName) (position b))
> =>
> (bind ?*status* -1)
> )
>
> I want to test for,
> "if the wine bottle is in position a, then the cola bottle cannot be in
> position b"
>
> The above two asserted facts would cause the rule to fire, setting status to
> -1, alerting me to the mismatch.
>
> But, the above rule excepts. The (call ?*a*) is not adequate for retrieving
> the particular instance of the rule i am looking for. Substituting
> 'solution' for 'call ?*a*' doesn't work, b/c then it doesn't allow me to
> differentiate between instances.
>
> Any guidance would be most welcome.
>
> Thanks,
> mark
>
> ---------------------------------------------------------------------
> To unsubscribe, send the words 'unsubscribe jess-users [EMAIL PROTECTED]'
> in the BODY of a message to [EMAIL PROTECTED], NOT to the
> list (use your own address!) List problems? Notify [EMAIL PROTECTED]
> ---------------------------------------------------------------------
>
---------------------------------------------------------
Ernest Friedman-Hill
Distributed Systems Research Phone: (925) 294-2154
Sandia National Labs FAX: (925) 294-2234
Org. 8920, MS 9012 [EMAIL PROTECTED]
PO Box 969 http://herzberg.ca.sandia.gov
Livermore, CA 94550
---------------------------------------------------------------------
To unsubscribe, send the words 'unsubscribe jess-users [EMAIL PROTECTED]'
in the BODY of a message to [EMAIL PROTECTED], NOT to the
list (use your own address!) List problems? Notify [EMAIL PROTECTED]
---------------------------------------------------------------------
