JESS: A rule that must match exactly 3 facts

[Jean-Francois Lassonde]

Hi,

 

I'm starting with JESS and stumbled on a problem.

 

The following rule is supposed to activate when a person have exactly 3 objects. (there is exactly 3 facts "person-have-object"):

 

(defrule person-have-3-objects

    (person-have-object ?person ?object1)
    (person-have-object ?person ?object2)
    (person-have-object ?person ?object3)

    =>

    (printout t ?object1 ?object2 ?object3))

 

In the LHS, I want to express the fact that person-have-object is found exactly 3 times for a unique person in the facts database. And I'd like to have a reference to each object for operation in the RHS.

 

I thought that my LHS was correct but it matches when there is only 1 fact (person-have-object myself computer). It will prints "computer computer computer".

 

How can I explicitly state that I want ?object1, ?object2 and ?object3 to be different?

 

Thank you,

--
Jean-Francois Lassonde

[Ernest Friedman-Hill]

If you want object1, object2, and object3 to be different, then you  
have to say so:


(defrule person-have-3-objects
     (person-have-object ?person ?object1)
     (person-have-object ?person ?object2&~?object1)
     (person-have-object ?person ?object3&~?object2&~?object1)
     =>
     (printout t ?object1 ?object2 ?object3))


On May 12, 2008, at 1:25 PM, Jean-Francois Lassonde wrote:

> Hi,
>
> I'm starting with JESS and stumbled on a problem.
>
> The following rule is supposed to activate when a person have  
> exactly 3 objects. (there is exactly 3 facts "person-have-object"):
>
> (defrule person-have-3-objects
>     (person-have-object ?person ?object1)
>     (person-have-object ?person ?object2)
>     (person-have-object ?person ?object3)
>     =>
>     (printout t ?object1 ?object2 ?object3))
>
> In the LHS, I want to express the fact that person-have-object is  
> found exactly 3 times for a unique person in the facts database. And  
> I'd like to have a reference to each object for operation in the RHS.
>
> I thought that my LHS was correct but it matches when there is only  
> 1 fact (person-have-object myself computer). It will prints  
> "computer computer computer".
>
> How can I explicitly state that I want ?object1, ?object2 and ?
> object3 to be different?
>
> Thank you,
>
> --
> Jean-Francois Lassonde

---------------------------------------------------------
Ernest Friedman-Hill
Informatics & Decision Sciences          Phone: [phone]
Sandia National Labs                FAX:   [phone]
PO Box 969, MS 9012                 ejfried@...
Livermore, CA 94550                 http://www.jessrules.com




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