Indeed, this seems useful; but what should ?x be bound to if there are
2 matches, or 100?
I think Alan Littleford wrote:
> Ernest,
>
> I suspected as much. However it would seem that, implementation aside, it
> _should_ bind variables - (exists (foo ?x)) means: is there at least one x which
> satisfies the asserted fact ? and here it is. As a practical matter it means I can
> do:
>
> (defrule foo-rule
> (exists (foo ?x))
> =>
> (do something with x that has side-effects that I only want to do once)
> )
>
> otherwise I have to do
>
> (defrule foo-rule
> (not (done-it))
> (exists foo ?x))
> =>
> ( .. ditto ..)
> (assert (done-it))
> )
>
> friedman_hill ernest j wrote:
>
> > Hi Alan,
> >
> > Thanks. This is, as you probably guessed, a documentation error. The
> > imaginary example was apparently too cute to resist, irregardless of the
> > fact that it doesn't work! It can't work because of the not-not
> > implementation, as you state.
> >
> > I think Alan Littleford wrote:
> > > Ernest,
> > >
> > > The 5.1. documents seem to imply (2.8.1.7) that (exists) binds
> > > variables:
> > >
> > > Jess> (defrule exists-demo
> > > (exists (honest ?m))
> > > =>
> > > (printout t ?m " is an honest man!" crlf))
> > >
> > >
> >
> >
> > ---------------------------------------------------------
> > 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]
> ---------------------------------------------------------------------
>
---------------------------------------------------------
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]
---------------------------------------------------------------------
