[m-users.] Generic predicate for enumeration types

[Philippe de Rochambeau]

Hello,

I would like to create a predicate called small which works for the cat and dog types show below.

I’ve tried to create a generic predicate, but to no avail:

:- pred cat(T::out) is multi.
cat(X) :- small(X).


Any help would be much appreciated.

Many thanks.

Philippe

-----------------------------------------------------------------------------------

:- implementation.

:- type cat
        --->  bill
        ;     harry
        ;     mary
        ;     steve.

:- type dog
        --->  fido
        ;     fred
        ;     henry
        ;     jane
        ;     rover
        ;     tom.

:- pred cat(cat::out) is multi.
cat(Cat) :- small(Cat).

:- pred dog(dog::out) is multi.
dog(Dog) :- small(Dog).

:- pred small(cat).
:- mode small(in) is semidet.
:- mode small(out) is multi.
small(steve).
small(harry).
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