Re: "maplist" for DCG?

Once ago I have a similar need, and implemented a set of maplist_dcg//N
predicates in one of my libraries, basically is the code Richard wrote for
mapnt, but using the call/(N+1) predicates:

:- module(maplist_dcg, [maplist_dcg/4,
                        maplist_dcg/5,
                        maplist_dcg/6,
                        maplist_dcg/7,
                        maplist_dcg/8,
                        maplist_dcg/9]).

:- meta_predicate maplist_dcg(3, ?, ?, ?).

maplist_dcg(Goal, List) -->
    maplist_dcg_(List, Goal).

:- meta_predicate maplist_dcg_(?, 3, ?, ?).

maplist_dcg_([],    _) --> [].
maplist_dcg_([E|T], Goal) -->
    call(Goal, E),
    maplist_dcg_(T, Goal).

:- meta_predicate maplist_dcg(4, ?, ?, ?, ?).

maplist_dcg(Goal, List1, List2) -->
    maplist_dcg_(List1, List2, Goal).

:- meta_predicate maplist_dcg_(?, ?, 4, ?, ?).

maplist_dcg_([],       [],      _) --> [].
maplist_dcg_([E1|T1] , [E2|T2], Goal) -->
    call(Goal, E1, E2),
    maplist_dcg_(T1, T2, Goal).
...

The source is part of the refactoring tool I made:
https://github.com/edisonm/refactor/blob/master/prolog/maplist_dcg.pl
Regards,

Edison <http://edisonm.com/>


2013/11/21 Michael Ben Yosef <[email protected]>

> > maplist(F, In, Out) is one thing, but how do you do the equivalent with
> a DCG, so the effect is something//2
> > something(f, [In1, In2, In3])
> > is equivalent to
> > f(In1), f(In2), f(In3)
> >
> > where f/1 might be:
> > f(X) --> { code(X,Y)}, [Y].
> >
> > In other words each input gets processed and appended to the DCG list.
>  I feel like there's probably a standard predicate for this.
> >
> >
> > Alan Baljeu
>
> Is the something//2 you're looking for not simply foldl/4? (Sorry I'm
> late to this thread.)
>
> Michael
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