RE: [PATCH] lisa bug: matching on retracted facts

Ok, I applied your patch and ran it against the mab examples; they continue
to work. I don't have an explanation for the asymmetry either; I'd have to
"re-load" Lisa's rete algorithm into my thought processes. For now, I'd say
continue your testing and make sure your rulesets behave correctly. If
you're successful, please let me know and I'll make a release with this
patch (and some others in the queue).

Thanks very much for your contribution.

Cheers, David

-----Original Message-----
From: Andy Sloane [mailto:[email protected]]
Sent: Friday, July 08, 2005 12:01 AM
To: [email protected]; [email protected]
Subject: [Lisa-users] [PATCH] lisa bug: matching on retracted facts


Andy Sloane wrote:
> I have a much simpler test case which more clearly demonstrates what's 
> going on, and a workaround:

...And now I have a patch.

In the node2 class, there was a specialized defmethod for 
test-against-left-memory when the right token was a remove token, but 
none for test-against-right-memory for the complementary condition. 
Adding it fixes the problem.

I don't really understand the asymmetry between "left tokens" and "right 
token" in the Rete code -- they both seem to contain one token.  Was 
there a reason this method wasn't supposed to exist?

Also, should the first test-against-right-memory method specialize to 
(left-tokens add-token), as all the other *-from-left methods do?

-Andy


diff -u -3 -p -u -r1.2 node2.lisp
--- src/rete/reference/node2.lisp	21 Jun 2005 00:23:40 -0000	1.2
+++ src/rete/reference/node2.lisp	8 Jul 2005 03:37:36 -0000
@@ -33,6 +33,14 @@
             (pass-tokens-to-successor
              self (combine-tokens left-tokens right-token)))))

+(defmethod test-against-right-memory ((self node2) (left-tokens 
remove-token))
+  (loop for right-token being the hash-value
+      of (join-node-right-memory self)
+      do (when (test-tokens self left-tokens right-token)
+           (pass-tokens-to-successor
+            self (combine-tokens
+                  (make-remove-token left-tokens) right-token)))))
+
  (defmethod test-against-left-memory ((self node2) (right-token add-token))
    (loop for left-tokens being the hash-value
        of (join-node-left-memory self)


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