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(a)codehaus.org&gt; 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(a)gmail.com&gt; 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(a)lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/rules-users > > > _______________________________________________ > rules-users mailing list > rules-users(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/rules-users >