root/tags/lgt2311/library/numberlist.lgt

:- object(numberlist,
    implements(numberlistp),
    extends(list)).

    :- info([
        version is 1.1,
        author is 'Paulo Moura',
        date is 2007/4/20,
        comment is 'List of numbers predicates.']).

    average([], 0.0).
    average([N| Ns], Average) :-
        average(Ns, 1, N, Average).

    average([], Length, Sum, Average) :-
        Average is Sum / Length.
    average([N| Ns], Lacc, Sacc, Average) :-
        Lacc2 is Lacc + 1,
        Sacc2 is Sacc + N,
        average(Ns, Lacc2, Sacc2, Average).

    min([N| Ns], Min) :-
        min(Ns, N, Min).

    min([], Min, Min).
    min([N| Ns], Aux, Min) :-
        (   N < Aux ->
            min(Ns, N, Min)
        ;   min(Ns, Aux, Min)
        ).

    max([N| Ns], Max) :-
        max(Ns, N, Max).

    max([], Max, Max).
    max([N| Ns], Aux, Max) :-
        (   N > Aux ->
            max(Ns, N, Max)
        ;   max(Ns, Aux, Max)
        ).

    product(List, Product) :-
        product(List, 1, Product).

    product([], Product, Product).
    product([N| Ns], Acc, Product) :-
        Acc2 is Acc * N,
        product(Ns, Acc2, Product).

    sum(List, Sum) :-
        sum(List, 0, Sum).

    sum([], Sum, Sum).
    sum([N| Ns], Acc, Sum) :-
        Acc2 is Acc + N,
        sum(Ns, Acc2, Sum).

    valid(List) :-
        nonvar(List),
        \+ \+ valid2(List).

    valid2([]).
    valid2([Head| Tail]) :-
        number(Head),
        valid2(Tail).

:- end_object.