[rules-users] How to use a result of custom defined function in WHEN part?

[Michael Anstis]

Am I missing something or can't this be achieved purely "in rule":-

rule "Letter counter"
salience -100
when
    Letter( $c: character )
    not LetterCount( character == $c )
    List( $s : size > 1 ) from collect( Letter( character == $c ) )
then
    LetterCount lc = new LetterCount();
    lc.setCharacter($c);
    lc.setDuplications($s);
    insert(lc);
end

rule "Totals"
    salience 0
when
    LetterCount($c : character, $s : duplications);
then
    System.out.println("Letter " + $c + " has " + $s + " duplications"
end

2010/12/18 Wolfgang Laun <wolfgang.laun at gmail.com>

> createCardinality must return a Collection. I think the simplest way of
> solving your problem is to write a simple class LetterCounter implementing
> the counting and a DRL function extracting the collection of Tuples from
> the LetterCounter:
>
> public class LetterCounter extends HashMap<Character,Integer> {
>     public static  Set<Map.Entry<Character,Integer>> counterSet(
> Collection<Character> l ){
>         return new LetterCounter( l ).entrySet();
>     }
>     public LetterCounter( Collection<Character> chars ){
>         super();
>         for( Character c: chars ){
>             Integer count = get( c );
>             put( c, count == null ? 1 : count + 1 );
>         }
>     }
> }
>
> rule "count"
> when
>     $t: Something( $l: collectionOfLetters )
>     Map.Entry(  $key: key, $val: value > 1 ) from LetterCounter.counterSet(
> $l )
> then
>     System.out.println( "letter " + $key + ": " + $val );
> end
>
> -W
>
>
> On 18 December 2010 12:16, AleBu <aleboo at gmail.com> wrote:
>
>>
>> Hi,
>> I am new to Drools and do some experiments on it, and encountered on a
>> problem which can't solve for a last few days, so maybe someone can
>> explain
>> what I am doing wrong?
>> I will probably explain my problem with example. Lets say we have a
>> collection of letters like 'a', 'b', 'c', 'a', 'd', 'e', 'c'. And I want
>> to
>> report all letters that are duplicated, but only once providing a number
>> of
>> duplication. In other words, for each letter which is duplicated I need to
>> do a report by saying 'Letter X is duplicated N times.
>> My idea was to create cardinality collection for letters which is a
>> collection of POJOs Tuple where first is letter and second is cound (first
>> and second are properties). I created a function for it createCardinality(
>> Collection letters ) which returns such cardinality info and tried
>> something
>> like:
>> when
>>        Something( $letters: collectionOfLetters )
>>        Tuple( $letter: first, $count: second > 1 ) from collect( Tuple()
>> from
>> createCardinality( $letters ) )
>> then
>>        System.out.println( "Letter "+letter+" is duplicated "+$count+"
>> times" )
>>
>> But I am reported (at least it looks like this) about the problems with my
>> function createCardinality(). Maybe I misunderstood something about usage
>> of
>> FROM?
>> --
>> View this message in context:
>> http://drools-java-rules-engine.46999.n3.nabble.com/How-to-use-a-result-of-custom-defined-function-in-WHEN-part-tp2110515p2110515.html
>> Sent from the Drools - User mailing list archive at Nabble.com.
>> _______________________________________________
>> rules-users mailing list
>> rules-users at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/rules-users
>>
>
>
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