Re: Where is the maplist built-in predicate ?

[spam . spam . spam . spam]

maplist/2 is a built-in predicate in SWI Prolog.

I try this :

%maplist(?P, ?L) : Apply the predicate P on each element in L
maplist(P, []).
maplist(P, [X|Xn]) :- call(P, X),maplist(P, Xn).

But I get this :
| ?- maplist(odd, [z]).
no

Can you help me to define it correctly?

Selon Paulo Moura <address@hidden>:

>
> On 2010/06/09, at 17:17, address@hidden wrote:
>
> > Hello,
> >
> > I am using GNU Prolog 1.3.1.
> >
> > I use this code :
> >
> > % int(?I) : I is an integer
> > int(z).
> > int(s(X)) :- int(X).
> >
> > % odd(?I) : I is an odd integer
> > odd(s(z)).
> > odd(s(s(X))) :- odd(X).
> >
> > % intzodd(?I) : I is an odd integer or zero (z)
> > intzodd(X) :- X=z.
> > intzodd(X) :- odd(X).
> >
> > % listzodd(?L) : L is a list which each element is an odd integer or zero
> (z)
> > listzodd(X) :- maplist(intzodd, X).
> >
> > And I don't find the maplist built-in predicate.
> >
> > | ?- listzodd([z]).
> > uncaught exception: error(existence_error(procedure,maplist/2),listzodd/1)
> >
> > Where is the maplist built-in predicate, please?
>
> maplist/2 is not a built-in predicate in GNU Prolog and, as far as I know, in
> any other Prolog compiler. Some Prolog compilers, however, provide it in a
> library. You will need to define it yourself. Is easy.
>
> Cheers,
>
> Paulo
>
>
> -----------------------------------------------------------------
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> Assistant Professor
> Dep. of Computer Science, University of Beira Interior
> 6201-001 Covilhã, Portugal
>
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