root/tags/lgt2310/library/loop.lgt

 
:- object(loop,
    implements(loopp)).

    :- info([
        version is 1.1,
        author is 'Paulo Moura',
        date is 2006/9/17,
        comment is 'Loop control structures predicates.']).

    :- meta_predicate(whiledo(::, ::)).
    whiledo(Condition, Action) :-
        (   call(Condition) ->
            \+ \+ call(Action),
            whiledo(Condition, Action)
        ;   true
        ).

    :- meta_predicate(dowhile(::, ::)).
    dowhile(Action, Condition) :-
        \+ \+ call(Action),
        whiledo(Condition, Action).

    :- meta_predicate(forto(*, *, ::)).
    forto(First, Last, Call) :-
        (   First =< Last ->
            \+ \+ call(Call),
            Next is First + 1,
            forto(Next, Last, Call)
        ;   true
        ).

    :- meta_predicate(forto(*, *, *, ::)).
    forto(Count, First, Last, Call) :-
        (   First =< Last ->
            \+ \+ (Count = First, call(Call)),
            Next is First + 1,
            forto(Count, Next, Last, Call)
        ;   true
        ).

    :- meta_predicate(fordownto(*, *, ::)).
    fordownto(First, Last, Call) :-
        (   First >= Last ->
            \+ \+ call(Call),
            Next is First - 1,
            fordownto(Next, Last, Call)
        ;   true
        ).

    :- meta_predicate(fordownto(*, *, *, ::)).
    fordownto(Count, First, Last, Call) :-
        (   First >= Last ->
            \+ \+ (Count = First, call(Call)),
            Next is First - 1,
            fordownto(Count, Next, Last, Call)
        ;   true
        ).

:- end_object.