root/tags/lgt2210/library/random.lgt

:- object(random,
    implements(randomp)).


    :- info([
        version is 1.1,
        author is 'Paulo Moura',
        date is 2002/8/7,
        comment is 'Random number generator predicates.']).


    :- initialization(::reset_seed).


    :- private(seed_/3).
    :- dynamic(seed_/3).

    :- mode(seed_(-integer, -integer, -integer), one).

    :- info(seed_/3, [
        comment is 'Stores the current random generator seed values.',
        argnames is ['S0', 'S1', 'S2']]).


    random(Random) :-
        ::retract(seed_(A0, A1, A2)),
        random(A0, A1, A2, B0, B1, B2, Random),
        ::asserta(seed_(B0, B1, B2)).


    random(A0, A1, A2, B0, B1, B2, Random) :-
        B0 is (A0*171) mod 30269,
        B1 is (A1*172) mod 30307,
        B2 is (A2*170) mod 30323,
        Float is A0/30269 + A1/30307 + A2/30323,
        Random is Float - truncate(Float).


    random(Lower, Upper, Random) :-
        integer(Lower),
        integer(Upper),
        Upper >= Lower,
        !,
        random(Float),
        Random is truncate((Float * (Upper-Lower)+Lower)).


    random(Lower, Upper, Random) :-
        float(Lower),
        float(Upper),
        Upper >= Lower,
        random(Float),
        Random is Float * (Upper-Lower)+Lower.


    randseq(Length, Lower, Upper, Sequence) :-
        integer(Length),
        Length >= 0,
        integer(Lower),
        integer(Upper),
        Upper >= Lower,
        !,
        ::retract(seed_(A0, A1, A2)),
        randseq(Length, Lower, Upper, (A0, A1, A2), (B0, B1, B2), [], List),
        ::asserta(seed_(B0, B1, B2)),
        map_truncate(List, Sequence).

    randseq(Length, Lower, Upper, Sequence) :-
        integer(Length),
        Length >= 0,
        float(Lower),
        float(Upper),
        Upper >= Lower,
        ::retract(seed_(A0, A1, A2)),
        randseq(Length, Lower, Upper, (A0, A1, A2), (B0, B1, B2), [], Sequence),
        ::asserta(seed_(B0, B1, B2)).


    randseq(0, _, _, Seed, Seed, List, List) :-
        !.

    randseq(N, Lower, Upper, (A0, A1, A2), (C0, C1, C2), Acc, List) :-
        N2 is N - 1,
        random(A0, A1, A2, B0, B1, B2, R),
        Random is R * (Upper-Lower)+Lower,
        randseq(N2, Lower, Upper, (B0, B1, B2), (C0, C1, C2), [Random| Acc], List).


    map_truncate([], []).

    map_truncate([Float| Floats], [Integer| Integers]) :-
        Integer is truncate(Float),
        map_truncate(Floats, Integers).


    randset(Length, Lower, Upper, Set) :-
        integer(Length),
        Length >= 0,
        integer(Lower),
        integer(Upper),
        Upper >= Lower,
        Length =< Upper - Lower,
        !,
        ::retract(seed_(A0, A1, A2)),
        randset(Length, Lower, Upper, (A0, A1, A2), (B0, B1, B2), [], Set),
        ::asserta(seed_(B0, B1, B2)).

    randset(Length, Lower, Upper, Set) :-
        integer(Length),
        Length >= 0,
        float(Lower),
        float(Upper),
        Upper >= Lower,
        ::retract(seed_(A0, A1, A2)),
        randset(Length, Lower, Upper, (A0, A1, A2), (B0, B1, B2), [], Set),
        ::asserta(seed_(B0, B1, B2)).


    randset(0, _, _, Seed, Seed, List, List) :-
        !.

    randset(N, Lower, Upper, (A0, A1, A2), (C0, C1, C2), Acc, List) :-
        N2 is N - 1,
        random(A0, A1, A2, B0, B1, B2, Float),
        Float2 is Float * (Upper-Lower)+Lower,
        (integer(Lower) ->
            Random is truncate(Float2)
            ;
            Random is Float2),
        (not_member(Acc, Random) ->
            add_ordered(Acc, Random, Acc2),
            randset(N2, Lower, Upper, (B0, B1, B2), (C0, C1, C2), Acc2, List)
            ;
            randset(N, Lower, Upper, (B0, B1, B2), (C0, C1, C2), Acc, List)).


    not_member([], _).

    not_member([H| T], R) :-
        H =\= R,
        not_member(T, R).


    add_ordered([], R, [R]).

    add_ordered([H| T], R, L) :-
        H > R ->
            L = [R, H| T]
            ;
            L = [H| T2],
            add_ordered(T, R, T2).


    reset_seed :-
        ::retractall(seed_(_, _, _)),
        ::asserta(seed_(3172, 9814, 20125)).


    set_seed(Seed) :-
        integer(Seed),
        Seed > 0,
        ::retractall(seed_(_, _, _)),
        S0 is Seed mod 30269,
        S1 is Seed mod 30307,
        S2 is Seed mod 30323,
        ::asserta(seed_(S0, S1, S2)).


:- end_object.