[rules-dev] [rules-users] No eval with backward chaining?

[Wolfgang Laun]

Created a JIRA.
-W

On 24/06/2013, Wolfgang Laun <wolfgang.laun at gmail.com> wrote:
> Below is a self-contained DRL file where Drools crashes during evaluation
> at runtime, even though it compiles and appears to be correct.
>
> package pythagoras;
>
> rule "kickoff"
> salience 100
> when
> then
>     for( Integer i: new Integer[]{3,4,5,12,13 } ){
>        insert( i );
>     }
> end
>
> rule "find triple forward"
> when
>    Integer( $a: intValue )
>    Integer( $b: intValue > $a )
>    Integer( $c: intValue > $b )
>    eval( $a*$a + $b*$b == $c*$c )
> then
>    System.out.println( "fwd: " + $a + " " + $b + " " + $c );
> end
>
> query isTriple( Integer $a, Integer $b, Integer $c )
>    Integer( intValue == $a )
>    Integer( intValue == $b && > $a )
>    Integer( intValue == $c && > $b )
>    eval( $a*$a + $b*$b == $c*$c )
> end
>
> rule "find triple backward"
> when
>    isTriple( $a, $b, $c; )
> then
>    System.out.println( "bwd: " + $a + " " + $b + " " + $c );
> end
>
>
> On 21/06/2013, Mark Proctor <mproctor at codehaus.org> wrote:
>> Can you submit a pull request against master, 6.x, with the test. Put it
>> in
>> BackwardChainingTest. We'll back port the test and fix to 5.x.
>>
>> thanks
>>
>> Mark
>> On 21 Jun 2013, at 16:00, Wolfgang Laun <wolfgang.laun at gmail.com> wrote:
>>
>>> Trying to use eval in a query for backward chaining causes a runtime
>>> crash running Drools 5.5.0. Looks like a bug. The details:
>>>
>>> Given some Integer objects as facts,
>>>  rule "find triple forward"
>>>  when
>>>     Integer( $a: intValue )
>>>     Integer( $b: intValue > $a )
>>>     Integer( $c: intValue > $b )
>>>     eval( $a*$a + $b*$b == $c*$c )
>>>  then
>>>     System.out.println( "fwd: " + $a + " " + $b + " " + $c );
>>>  end
>>> finds Pythagorean triples.
>>>
>>> But
>>>  query isTriple( Integer $a, Integer $b, Integer $c )
>>>     Integer( intValue == $a )
>>>     Integer( intValue == $b && > $a )
>>>     Integer( intValue == $c && > $b )
>>>     eval( $a*$a + $b*$b == $c*$c )
>>>  end
>>> intended to be used in combination with
>>>  rule "find triple backward"
>>>  when
>>>     isTriple( $a, $b, $c; )
>>>  then
>>>     System.out.println( "bwd: " + $a + " " + $b + " " + $c );
>>>  end
>>> causes a nasty runtime error (although DRL compilation succeeds):
>>> Exception in thread "main" java.lang.NoSuchMethodError:
>>> pythagoras.Rule_isTriple_17ac16f7237046ee9562afce35dfe174.eval0(III)Z
>>> 	at
>>> pythagoras.Rule_isTriple_17ac16f7237046ee9562afce35dfe174Eval0InvokerGenerated.evaluate(Unknown
>>> Source)
>>> 	at
>>> pythagoras.Rule_isTriple_17ac16f7237046ee9562afce35dfe174Eval0Invoker.evaluate(Unknown
>>> Source)
>>> 	at org.drools.rule.EvalCondition.isAllowed(EvalCondition.java:114)
>>> 	at
>>> org.drools.reteoo.EvalConditionNode.assertLeftTuple(EvalConditionNode.java:176)
>>> 	at
>>> org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:196)
>>> 	at
>>> org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:71)
>>> 	at org.drools.reteoo.JoinNode.propagateFromRight(JoinNode.java:159)
>>> 	at org.drools.reteoo.JoinNode.assertObject(JoinNode.java:148)
>>> 	at
>>> org.drools.reteoo.CompositeObjectSinkAdapter.doPropagateAssertObject(CompositeObjectSinkAdapter.java:497)
>>> 	at
>>> org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:382)
>>> 	at
>>> org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:235)
>>> 	at
>>> org.drools.reteoo.EntryPointNode.assertObject(EntryPointNode.java:240)
>>> 	at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:350)
>>> 	at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:311)
>>> 	at
>>> org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:903)
>>> 	at
>>> org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:847)
>>> 	at
>>> org.drools.impl.StatefulKnowledgeSessionImpl.insert(StatefulKnowledgeSessionImpl.java:269)
>>> 	at pythagoras.Main.makeFacts(Main.java:94)
>>> 	at pythagoras.Main.execute(Main.java:78)
>>> 	at pythagoras.Main.main(Main.java:103)
>>>
>>> -W
>>> _______________________________________________
>>> rules-users mailing list
>>> rules-users at lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/rules-users
>>
>>
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