Hi,
The answer depends on what you want to do with it when you get
it. Current releases of Jess haven't provided the ready-made tools
to do anything with entire facts once you have a reference to one, so
none of the possibilities are trivial; I expect that one of these days
I'll put in something like the CLIPS "fact-functions" patch from the
early 6.0 days to add things like get-fact-slot, set-fact-slot, etc.
But anyway. You can, for example, pass the fact-index (in ?p) to a
userfunction, and the userfunction can then use the Java API to
manipulate the fact. For example, here's a userfunction that given
the index of a fact and the name of a slot, retrieves the slot's
contents in Jess 5.0aX:
public class FactSlotValue implements Userfunction
{
public String getName() { return "fact-slot-value"; }
public Value call(ValueVector vv, Context context) throws ReteException
{
Fact f = new Fact(context.getEngine().findFactByID(vv.get(1).factIDValue()),
context.getEngine());
return f.findValue(vv.get(2).stringValue());
}
}
Given this function, you can then write deffunctions like
(deffunction print-bar (?id)
"Print the contents of the bar slot in a fact."
(printout t (fact-slot-value ?id bar) crlf))
You could write other UserFunctions to allow you to do other things
with Facts. As I said, expect a future version of Jess to ship with
functions like fact-slot-value.
Unfortunately, the Fact class has changed in the past, and will,
change in the future, so any functions you write of this nature might
need frequent rewriting.
I think H�kan Lindgren wrote:
>
> Is there any way to send a fact from the fact list to a userfunction. I
> would like to do something like this:
>
> (deftemplate XXX (slot A)(slot B))
>
> (defrule YYY
> ?p<-(XXX (A 2)(B 2))
> =>
> (userfunction ?p))
>
> the assert and run commands are done from a java class. I have succeeded
> to send a string but I would like to send the fact.
>
> Thanks in advance for any response. / Hakan
---------------------------------------------------------
Ernest Friedman-Hill
Distributed Systems Research Phone: (925) 294-2154
Sandia National Labs FAX: (925) 294-2234
Org. 8920, MS 9214 [EMAIL PROTECTED]
PO Box 969 http://herzberg.ca.sandia.gov
Livermore, CA 94550
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