option(guard_simplification,off).
option(mode,tak_chr(+,+,+,?)).

:- constraints tak_chr/4.

tak_chr(X,Y,Z,A) <=> X =< Y | Z = A.

tak_chr(X,Y,Z,A) <=> X > Y | X1 is X - 1,
        tak_chr(X1,Y,Z,A1),
        Y1 is Y - 1,
        tak_chr(Y1,Z,X,A2),
        Z1 is Z - 1,
        tak_chr(Z1,X,Y,A3),
        tak_chr(A1,A2,A3,A).

repeat(_N).
repeat(N):-
	N > 1, 
	N1 is N-1, 
	repeat(N1).

go :-
	measure(tak(1000),true,Utime,Gtime,System),
        write(bench(tak_prolog,1000,Utime,Gtime,System)),write('.'),nl,fail.
go :-
	measure(tak_chr(1000),true,Utime,Gtime,System),
        write(bench(tak_CHR,1000,Utime,Gtime,System)),write('.'),nl,fail.

tak(N) :- repeat(N),tak ,fail ;true.
tak :- tak(18,12,6,_),fail.

tak_chr(N) :- repeat(N),tak_chr ,fail ;true.
tak_chr :- tak_chr(18,12,6,_),fail.


% generated: 17 November 1989
% option(s): SOURCE_TRANSFORM_1
%
%   tak
%
%   Evan Tick (from Lisp version by R. P. Gabriel)
%
%   (almost) Takeuchi function (recursive arithmetic)

tak(X,Y,Z,A):-
        X =< Y,!,
        Z = A.

tak(X,Y,Z,A):-
        X1 is X - 1,
        tak(X1,Y,Z,A1),
        Y1 is Y - 1,
        tak(Y1,Z,X,A2),
        Z1 is Z - 1,
        tak(Z1,X,Y,A3),
        tak(A1,A2,A3,A).