:- object(ack).

:- info([
        version is 1:0:0,
        author is 'Paulo Moura',
        date is 2008-3-31,
        comment is 'Ackermann function (general recursive function).'
]).

:- public(ack/3).
:- mode(ack(+integer, +integer, -integer), one).
:- info(ack/3, [
        comment is 'Ackermann function.',
        argnames is ['M', 'N', 'V']
]).

ack(0, N, V) :-
        !,
        V is N + 1.
ack(M, 0, V) :-
        !,
        M2 is M - 1,
        ack(M2, 1, V).
ack(M, N, V) :-
        M2 is M - 1,
        N2 is N - 1,
        ack(M, N2, V2),
        ack(M2, V2, V).

:- end_object.