[rules-users] Reg. Iterating over a list

[Wolfgang Laun]

Note that the CE "forall" in Drools must be applied to a set of facts. For
determining whether a List attribute fulfils some condition, the negated
existential quantifier might be applied.

   p: Project()
   not ( Integer( this <= 2 ) from p.list )

In some cases a direct test of the collection may be preferable:

   p: Project( list contains 3 || contains 4 )   // contains element > 2 and < 5

Also note that Drools permits you to create custom evaluators so that
you might, for instance, create set test operations that can be applied to
all Collection type fields.

-W

 for the list (Project - P; P.list), is each element is
>> greater
>> than 2? (or in e

On 03/09/2012, Mark Proctor <mproctor at codehaus.org> wrote:
>
> On 3 Sep 2012, at 00:56, Phani Saripalli <saripalli.phani at gmail.com> wrote:
>
>> Hi.
>>
>> I tried to identify relevant ways for some container specific operations
>> like exists, forall (or foreach). Basically I have started using for
>> software product line research, and specifically model checking over
>> product
>> line models. The initial results so fat ( considering the time I started)
>> have been wonderful, alas I am tuck at this point.
>>
>>
>> For example, consider :
>> import java.util.List;
>> import java.util.Arrays;
>> import java.util.ArrayList;
>>
>> declare Project
>>    a : int
>>    b : int = 5
>>    list : List =  new java.util.ArrayList(java.util.Arrays.asList(1 , 2 ,
>> 3
>> , 4 , 5))
>> end
>>
>> Now that the element of Project - list is configured, I would like to
>> perform some operations on it like:
>> a) for each - for the list (Project - P; P.list), is each element is
>> greater
>> than 2? (or in essence - evaluating each element using a boolean
>> expression).
>>
>> b) Similarly, a function like exists . for the list, is there any element
>> for which this expression is satisfied -
>> t > 2 && t < 5, where t is the iterator for the list.
> p : Project()
> exists( Number( this > 2 && < 5 ) from p.list )
>>
>> As the elements of the lists are mere numbers (in this case ints), I am
>> not
>> really aware/clear how I can use the Drools operations collect, for all
>> etc.
>>
>> Previously I worked with Jess rule engine, and it has in built lambda
>> functions which nicely provides list iterators and thus evaluating each
>> element of the list against a boolean expression.
>>
>> I am at a very important point in my work, and any hint or solution will
>> be
>> highly appreciated.
>>
>> Many thanks :)
>>
>> Phani
>>
>>
>>
>> --
>> View this message in context:
>> http://drools.46999.n3.nabble.com/Reg-Iterating-over-a-list-tp4019512.html
>> Sent from the Drools: User forum mailing list archive at Nabble.com.
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>
>
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