Re: [rules-users] Locating facts via slot values

Here you go WolfGang rule shoot-3 when $h : Hunter( $target : target) Animal(this == $target) then $h.shoot( $a ); retract( $a ); end 2009/4/3 Wolfgang Laun <wolfgang.laun(a)gmail.com&gt; > Given a working memory containing a large number of rather static facts > which are from several subclasses (Ape, Bear, Crocodile,...) of some base > class (Animal) and a single fact of class Hunter with a field target of type > Animal, the shooting of an animal might be written with a rule like this: > > rule shoot-1 > when > ?h : Hunter( ?target : target ) > ?a : Animal() > eval(?target == ?a) > then > ?h.shoot( ?a ); > retract( ?a ); > end > > Avoiding eval (which is said to be inefficient), it could also be written > as > > rule shoot-2 > when > ?a: Animal() > ?h : Hunter( target == ?a ) > then > ?h.shoot( ?a ); > retract( ?a ); > end > > This, however, places the pattern with many instances up front, which is > (AFAIK) not so good in a Rete implementation. > > Which one is to be preferred in Drools? > > Ideally, one might want to write > > rule shoot-3 > when > ?h : Hunter( ?target : target ) > ?a == ?target : Animal() ### not valid DRL > then > ?h.shoot( ?a ); > retract( ?a ); > end > > This avoids eval, has the single instance fact up front, but it isn't > available. > > -W > > > > > _______________________________________________ > rules-users mailing list > rules-users(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/rules-users > > _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users