Re: JESS: [EXTERNAL] Dynamic rule matching in the LHS

Thank you for this tip. It is not what I am trying to achieve, however. I=
 must apologize if my original email was misunderstood.

My goal is to write a rule that would fire for any 'bag-of-items' fact wh=
ose item names, as listed in a multislot, are all represented by 'item' f=
acts. The rule should not fire if one or more of these items are absent f=
rom the fact list:

	(item (name A))
	(item (name B))
	(bag-of-items (item-names A))
	(bag-of-items (item-names A B))
	(bag-of-items (item-names A B C))

In this example the two first 'bag-of-items' facts would fire my hypothet=
ical rule, while the third would not, because there is no 'item' fact wit=
h name C.

The 'forall' approach suggested by M. Friedman-Hill is quite close to thi=
s, however it seems that the rule will fire only if _all_ the 'bag-of-ite=
ms' facts have all of their items represented by facts. I.e., in my examp=
le above it would not fire until I remove the third bag-of-items fact. On=
ce again, it is close but no cigar.

Best,
Aur=E9lien

On Jul 30, 2013, at 10:54 AM, "Jason Morris" <[email protected]> w=
rote:

> Another "old skool" way of doing it using predicate constraints is...
>=20
> (clear)
> (deftemplate item (slot name))
> (deftemplate bag-of-items (multislot item-names))
>=20
> (defrule fire-for-all-members-in-bag
>  ; If you have a bag of item names ...
>  (bag-of-items (item-names $?item-names))
>  ; and there is an item whose name is member of this bag ...
>  ?item <-(item (name ?name&:(member$ ?name $?item-names)))
> =3D>
>  ; ...then do something interesting
>  (printout t ?name " is in the bag!" crlf))
>=20
> ;; Program
> (reset)
> (assert (item (name A)))
> (assert (item (name B)))
> (assert (item (name C)))
> (assert (bag-of-items (item-names A B C)))
> (run)
>=20
> *Jason C. Morris*
> President, Principal Consultant
> Morris Technical Solutions LLC
> President, Rules Fest Association
> Chairman, IntelliFest 2013: International Conference on Reasoning
> Technologies



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