Be careful when using '$' prefixed variables. It they are used in conjuction
with a drool function then the parse will fail because the regular
expression cannot handle it. Michael Neale recommended not using '$'.
On 4/27/06, Edson Tirelli <[EMAIL PROTECTED]> wrote:
>
>
> Alberto,
>
> The "$" symbol is just a convention. Using it to name your variables
> makes easy to anyone looking at the rule to know that it is a bound
> variable. But it is not mandatory.
>
> Seems that we are suffering from a side effect of a feature
> implemented some time ago and not caught by our unit tests. Would you
> please open a Jira for it, attach your code and assign the issue to me?
> I'm working on it and shall solve it for RC3.
>
> Thank you,
>
> []s
> Edson
>
> Alberto Siena wrote:
>
> >Edson Tirelli <tirelli <at> post.com> writes:
> >
> >
> >
> >> Alberto,
> >>
> >> Follow my comments:
> >>
> >>1. In case 1, the only difference between the rules is that inside
> >>eval() you are using java code, so "==" means identity compare. When you
> >>use Relation( startnode == n1), it will effectivelly call equals()
> >>method on the startnode attribute value with n1 as a parameter. This
> >>way, the first thing would be to check if equals() method and hashcode()
> >>method are correctly implemented in Node class. If this does not work,
> >>please send me a self contained code and I will run and find out what is
> >>happening.
> >> For now, if you want to use identity compare in Drools, you can also
> >>use predicates as I show bellow. We don't have an identity operator yet,
> >>but we will.
> >>
> >>r : Relation ( sn : startnode -> ( sn == n1 ), en : endnode -> ( en ==
> >>n2 ) )
> >>
> >>2. For mathematical operators, you can use a "return value" constraint.
> >>As Drools boxes primitive types, the code is not that clean in java 1.4,
> >>but it is the best option for now. Look at the return value integration
> >>test (that I paste bellow) for a sample. Also, you can always use
> >>predicates and embed java code there.
> >>
> >>------
> >>package org.drools.test;
> >>
> >>import org.drools.Person;
> >>
> >>global java.util.List list;
> >>global java.lang.Integer two;
> >>
> >>rule "returnvalue rule test"
> >> when
> >> $person1:Person( $age1 : age )
> >> // We have no autoboxing of primtives, so have to do by hand
> >> person2:Person( age == ( new Integer( $age1.intValue() +
> >>two.intValue() ) ) )
> >> then
> >> list.add( $person1 );
> >> list.add( person2 );
> >>end
> >>-----------
> >>
> >> Hope it helps, and let me know if case 1 does not work after
> >>checking the equals() and hashcode() methods.
> >>
> >> []s
> >> Edson
> >>
> >>
> >>[cut]
> >>
> >>
> >
> >
> >Many thanks to both of you for your replies
> >
> >Here below I attach the full Java code. The classes Node and Relation
> have all
> >the accessors, are derived simply from Object and don't override equals()
> nor
> >hashcode().
> >
> >Using the getMetric() function actually works. (even if I would prefer a
> total
> >indipendence from Java :-)
> >
> >Last question: $person1:Person( $age1 : age )
> >What the $ symbol stand for? I don't see it in the user manual.
> >
> >Alberto
> >
> >
> >//////////////////////////////
> >
> >package tropostest;
> >
> >public class Node
> >{
> > public String name = "";
> > public float value = 0;
> >
> > public Node() {}
> > public Node( String a_name )
> > {
> > name = a_name;
> > }
> >
> > public float getValue()
> > {
> > return value;
> > }
> > public void setValue( float f )
> > {
> > value = f;
> > }
> >
> > public String getName()
> > {
> > return name;
> > }
> > public void setName( String n )
> > {
> > name = n;
> > }
> >}
> >
> >//////////////////////////////////////////
> >
> >package tropostest;
> >
> >public class Relation
> >{
> > public Node startnode;
> > public Node endnode;
> >
> > public float metric = 1.0f;
> >
> > public Node getStartnode()
> > {
> > return startnode;
> > }
> > public void setStartnode( Node n )
> > {
> > startnode = n;
> > }
> > public Node getEndnode()
> > {
> > return endnode;
> > }
> > public void setEndnode( Node n )
> > {
> > endnode = n;
> > }
> >
> > public float getMetric()
> > {
> > return metric;
> > }
> > public void setMetric( float m )
> > {
> > metric = m;
> > }
> >}
> >
> >/////////////////////////////////////
> >
> >public class Test
> >{
> > public static final void main(String[] args) {
> > try {
> >
> > //load up the rulebase
> > RuleBase ruleBase = readRule();
> > WorkingMemory workingMemory = ruleBase.newWorkingMemory();
> >
> > //go !
> > Node n1 = new Node( "N1" );
> > Node n2 = new Node( "N2" );
> > Node n3 = new Node( "N3" );
> > Node n4 = new Node( "N4" );
> >
> > Relation r1 = new Relation();
> > r1.setStartnode( n1 );
> > r1.setEndnode( n2 );
> >
> > Relation r2 = new Relation();
> > r2.setStartnode( n2 );
> > r2.setEndnode( n3 );
> >
> > Relation r3 = new Relation();
> > r3.setStartnode( n4 );
> > r3.setEndnode( n3 );
> >
> > n1.setValue( 0.5f );
> > n4.setValue( 0.7f );
> >
> > workingMemory.assertObject( n1 );
> > workingMemory.assertObject( n2 );
> > workingMemory.assertObject( n3 );
> > workingMemory.assertObject( n4 );
> > workingMemory.assertObject( r1 );
> > //workingMemory.assertObject( r2 );
> > //workingMemory.assertObject( r3 );
> >
> > System.out.println( "Initial state ( " +
> > n1.name + ":" + n1.value + ", " +
> > n2.name + ":" + n2.value + ", " +
> > n3.name + ":" + n3.value + ")" );
> >
> > workingMemory.fireAllRules();
> >
> > System.out.println( "Final state ( " +
> > n1.name + ":" + n1.value + ", " +
> > n2.name + ":" + n2.value + ", " +
> > n3.name + ":" + n3.value + ")" );
> > }
> > catch (Throwable t)
> > {
> > t.printStackTrace();
> > }
> > }
> >
> > /**
> > * Please note that this is the "low level" rule assembly API.
> > */
> > private static RuleBase readRule() throws Exception {
> > //read in the source
> > Reader source = new InputStreamReader(
> Test.class.getResourceAsStream(
> >"/BasicTropos.drl" ) );
> >
> > //optionally read in the DSL (if you are using it).
> > //Reader dsl = new InputStreamReader(
> DroolsTest.class.getResourceAsStream(
> >"/mylang.dsl" ) );
> >
> > //Use package builder to build up a rule package.
> > //An alternative lower level class called "DrlParser" can
> also be used...
> >
> > PackageBuilder builder = new PackageBuilder();
> >
> > //this wil parse and compile in one step
> > //NOTE: There are 2 methods here, the one argument one is
> for normal DRL.
> > builder.addPackageFromDrl( source );
> >
> > //Use the following instead of above if you are using a
> DSL:
> > //builder.addPackageFromDrl( source, dsl );
> >
> > //get the compiled package (which is serializable)
> > Package pkg = builder.getPackage();
> >
> > //add the package to a rulebase (deploy the rule package).
> > RuleBase ruleBase = RuleBaseFactory.newRuleBase();
> > ruleBase.addPackage( pkg );
> > return ruleBase;
> > }
> >}
> >
> >
> >
> >
> >
>
>
