[rules-users] Using "collect" repeatedly over sub-groups of a fact

[Wolfgang Laun]

You have to establish one representative of each subgroup that is markedly
distinct from all of its siblings in the same subgroup. This triggers a
single firing for a unique a/b combination. Then you can collect all those
that match the representative. With attribute c being what it is in your
example:

Fact( $a: a, $b: b, $c: c )
not Fact( c < $c )
$list: List() from collect ( Fact( a == $a, b == $b ) )

-W

On 14 May 2012 21:05, Mike Goldner <mike at thegoldners.com> wrote:

> I have a single rule that includes a "collect" pattern to pass a
> collection to the RHS.  However, what I now need to do fire this rule for
> multiple collections based on groupings defined by attributes on the fact.
>
> Here is an example:
>
> Fact(a = 1, b = 1, c = 1)
> Fact(a = 1, b = 1, c = 2)
> Fact(a = 2, b = 1, c = 3)
> Fact(a = 2, b = 2, c = 4)
> Fact(a = 2, b = 2, c = 5)
>
> I would like to create sub-groups based on the attributes 'a' and 'b'.  My
> rule should fire three times for the facts listed above, providing the
> corresponding collection of Fact.
>
> The only solution that I can think of is to build a HashSet and add each
> Fact to the HashSet using the attributes as keys.  I suppose it would have
> to be a nested set since I can't define a multi-valued key class within a
> rule.  I could then handle this HashSet in a RHS block.  However, I realize
> that I'm completely subverting the whole rule language…
>
> Any suggestions?
>
> Thanks,
>
> Mike
>
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