[rules-users] using forall to validate same field value from a list

[Wolfgang Laun]

You have to establish the age of one applicant as bound to a variable so
that you
can ascertain this being equal to the age of all Applicants.

rule "age-2"
when
    $list : List( size > 0 )  # ensure non-empty so that get(0) doesn't NPE
    forall( Applicant( $age : age == ( ((Applicant)$list.get(0)).getAge() )
) from $list )
then
    System.out.println( "success" );
end

On 15 September 2010 09:52, tushmish <Tushar.Mishra at lntinfotech.com> wrote:

>
> rule "age"
>        when
>                $list : List();
>                forall( $app : Applicant( $age : age) from $list
>                   Applicant( this == $app, age == $age ) );
>        then
>                System.out.println("success" );
> end
>
>
It's noteworthy that this rule would fire if you insert all Applicant
objects that are in the List as 1st order facts. What is does is

   forall( $app | $app in List &
                         forall ( $f | $f in WM & $f instanceof Applicant &
$f == $app & $f.age == $app.age ) )

where the inner "forall" is implied by the general fact matching algorithm.
The last term of the inner conjunction is redundant as we have established
the identity by $f == $app - the pattern just matches all list elements with
themselves.

-W
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