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%%
%% 991202 Slim Abdennadher, LMU
%%
%% ported to hProlog by Tom Schrijvers

:- use_module(library(chr)).
:- chr_option(debug,off).
:- chr_option(optimize,full).
:- chr_constraint fib(+,?). % mode declaration


%:- constraints fib/2.

%% fib(N,M) is true if  M is the Nth Fibonacci number.

%% Top-down Evaluation with Tabulation

fib(N,M1), fib(N,M2) <=> M1 = M2, fib(N,M1).
%fib(N,M1) \ fib(N,M2) <=> M1 = M2.

fib(0,M) ==> M = 1.

fib(1,M) ==> M = 1.

fib(N,M) ==> N > 1 | N1 is N-1, fib(N1,M1), N2 is N-2, fib(N2,M2), M is M1 + M2.

main :-
	main(18).

main(N):-
	cputime(X),
	fib(N,_),
	cputime( Now),
	Time is Now-X,
	write(bench(fib ,N,Time, 0,bp)),write('.'), nl.
                 

cputime(X):-X is cputime.