On Wed, Apr 23, 2008 at 4:28 PM, Anstis, Michael (M.) <manstis1@ford.com> wrote:

Thanks Steve,

This fixed the problem!

For Cheng Wei Lee's benefit this is the complete solution (I had to fix another part):-

public class DBUtils {

    public Collection getNumbers() {

        Integer[] numbers = new Integer[10];
        for (int i = 0; i < numbers.length; i++) {
            numbers[i] = (int)Math.random() * 100;
        }
        return Arrays.asList(numbers);
    }
}

rule "a1"
    when
        $max : Number() from accumulate( Number( $v : intValue ) from dbutils.getNumbers(), max($v) )
    then
        System.out.println($max.intValue());
    end

With kind regards,

Mike

From: rules-users-bounces@lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Steven Williams
Sent: 23 April 2008 09:07
To: Rules Users List
Subject: Re: [rules-users] Re: Is this scenario suitable for using Drools?

change DBUtils to return a Collection and it should work I think.

On Wed, Apr 23, 2008 at 5:50 PM, Anstis, Michael (M.) <manstis1@ford.com> wrote:

So, in my usual helpful manner I thought Drools would be a perfect match and put together what I thought would be a simple example:-

package com.sample

global com.sample.DBUtils dbutils;

rule "a1"
    when

        $max : Integer() from accumulate( Integer( $v : intValue ) from dbutils.getNumbers(), max($v) )

    then
        System.out.println($max);

end

public class DBUtils {

    public Integer[] getNumbers() {

        Integer[] numbers = new Integer[10];
        for (int i = 0; i < numbers.length; i++) {
            numbers[i] = (int) (Math.random() * 100);
        }
        return numbers;
    }
}

However this led to some errors:-

org.drools.RuntimeDroolsException: java.lang.ClassCastException: [Ljava.lang.Integer; incompatible with java.lang.Integer
at org.drools.rule.Accumulate.accumulate(Accumulate.java:131)
at org.drools.reteoo.AccumulateNode.assertTuple(AccumulateNode.java:127)
at org.drools.reteoo.CompositeTupleSinkAdapter.createAndPropagateAssertTuple(CompositeTupleSinkAdapter.java:73)
at org.drools.reteoo.LeftInputAdapterNode.assertObject(LeftInputAdapterNode.java:116)
at org.drools.reteoo.SingleObjectSinkAdapter.propagateAssertObject(SingleObjectSinkAdapter.java:22)
at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:153)
at org.drools.reteoo.Rete.assertObject(Rete.java:177)
at org.drools.reteoo.ReteooRuleBase.assertObject(ReteooRuleBase.java:192)
at org.drools.reteoo.ReteooWorkingMemory$WorkingMemoryReteAssertAction.execute(ReteooWorkingMemory.java:179)
at org.drools.common.AbstractWorkingMemory.executeQueuedActions(AbstractWorkingMemory.java:1292)
at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:891)
at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:858)
at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:659)
at com.sample.DroolsTest.main(DroolsTest.java:36)
Caused by: java.lang.ClassCastException: [Ljava.lang.Integer; incompatible with java.lang.Integer
at org.drools.base.java.lang.Integer968047027$intValue.getIntValue(Unknown Source)
at org.drools.base.ClassFieldExtractor.getIntValue(ClassFieldExtractor.java:197)
at org.drools.rule.Declaration.getIntValue(Declaration.java:230)
at com.sample.Rule_a1_0AccumulateExpression0Invoker.evaluate(Rule_a1_0AccumulateExpression0Invoker.java:16)
at org.drools.base.accumulators.JavaAccumulatorFunctionExecutor.accumulate(JavaAccumulatorFunctionExecutor.java:74)
at org.drools.rule.Accumulate.accumulate(Accumulate.java:123)
... 13 more

Have I done something really stupid and is Drools a fit?

Cheers,

Mike

From: rules-users-bounces@lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Cheng Wei Lee
Sent: 22 April 2008 17:27
To: rules-users@lists.jboss.org
Subject: [rules-users] Re: Is this scenario suitable for using Drools?

I've 2 algorithms to calculate the cost of a product. At any one time, there is only 1 algorithm in use. Initially algorithm 1 will be the default. Subsequently, the decision to use which algorithm will depend on customers feedback. The algorithms are:

Algorithm 1:
Cost = MAX(P1, T1, P2, T2, P3, T3, ...)

Algorithm 2:
Cost = MIN(P1, P2, P3, ...) + MIN(T1, T2, T3, ...)

The values of P1, P2, ... are stored within a database. The number of Ps & Ts are unknown but can be determined by querying the database, Would drools be a good option to use to store the algorithms? If so, how could I be able to retrieve the values of P1, P2, etc from the database from within drools?

Thanks!

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