I think John Goalby wrote:
> I understand the approach that you outlined and have got
> someway to implementing it when I realized that I might
> be looking for something a little different.
>
> I want to be able to add up the payments as the facts
> get asserted - as I am doing backchaining.
>
> The payments are asserted separately (assert (PURCHASE 100)).
>
> I want to be able to define a rule such that I can accumulate
> the purchases as they happen. The rule may look like:
>
> (defrule CHECKIT (PURCHASE ?AMT) (test (> ?AMT 80)) => (printout t ?AMT
> crlf))
>
> What I would like is a rule to then specify that if the running
> total is over a certain amount then printout a warning.
>
> (defrule CHECKIT (PURCHASE ?AMT) (test (> ?AMT 80)) (test (> ?TOT 200)) =>
> (printout t WARNING " " ?TOT crlf))
>
> Obviously I have not shown how to calc ?TOT as I don't
> know how!!! This is where my knowledge is very limited.
Well, as always, there are about a million ways to do it. Here's one:
you could put the sum in a defglobal:
(defglobal ?*sum* = 0)
Then you could do something like this:
(defrule CHECKIT
(PURCHASE ?AMT)
(test (> ?AMT 80))
(test (progn (bind ?*sum* (+ ?*sum* ?AMT))
(> ?*sum* 200)))
=>
(printout t WARNING " " ?*sum* crlf))
(progn) just groups function calls together, so you can call more than
one thing during a single (test) CE.
>
> Thanks
>
> John.
>
> ----Original Message Follows----
> This is the trditional CLIPS solution, but it involves lots, lots more
> computational work (both in CLIPS and in Jess.) If the number of
> "purchase" facts is N, then roughly 2(N^2) partial matches will be
> formed. The total number of rule activations is almost as large. The
> defquery solution forms only N partial matches. If N is 50, 2(N^2) is
> 5000, so the traditional solution does ~100 times more computation
> (actually worse since all the activations have to be processed and the
> rule has to fire ~50 times.) Plus, as you say, it's destructive.
>
> Defqueries are a Good Thing for applications like this.
>
> I think Thomas Gentsch wrote:
> >
> > I would have done something like that:
> >
> > (defrule sum
> > ?f1 <- (purchase ?s1)
> > ?f2 <- (purchase ?s2)
> > (test (neq ?f1 ?f2))
> > =>
> > (retract ?f1)
> > (retract ?f2)
> > (assert (purchase (+ ?s1 ?s2)))
> > )
> >
> > Works at least with CLIPS but I suppose with Jess as well. How does that
> > compare performance-wise?
> >
> > (Of course, your initial facts are gone afterwards - if you want to keep
> > them, it gets a little more difficult).
> >
> > tge
> >
> > [EMAIL PROTECTED] wrote:
> > >
> > > The most efficient way to do it would be to use a defquery to find all
> > > the PURCHASE facts, then iterate over the query result directly and
> > > add them up. You could define a deffunction to do this.
> > >
> > > I think John Goalby wrote:
> > > > I would like to be able to have the following facts...
> > > >
> > > > (assert (PURCHASE 100))
> > > > (assert (PURCHASE 150))
> > > > (assert (PURCHASE 70))
> > > >
> > > > and then be able to have a rule that would give me the
> > > > sum of these purchases. Is that possible?
> > > >
> > > > Thanks
> > > >
> > > > John.
> > >
> >
> > --
> > Thomas Gentsch
> >
> >
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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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---------------------------------------------------------
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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