Well,
I suppose the answer is that it is officially non-deterministic. A value is bound
for
which such a fact exists. Period.
Tnx
Alanl
[EMAIL PROTECTED] wrote:
> 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
> >
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> >
>
> ---------------------------------------------------------
> 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
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