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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%
%% 16 June 2003 Bart Demoen, Tom Schrijvers, K.U.Leuven
%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
:- module(fibonacci,[]).
:- use_module(library(chr)).
:- constraints fibonacci/2.
%% fibonacci(N,M) is true iff M is the Nth Fibonacci number.
%% Top-down Evaluation with effective Tabulation
%% Contrary to the version in the SICStus manual, this one does "true"
%% tabulation
fibonacci(N,M1) # Id \ fibonacci(N,M2) <=> var(M2) | M1 = M2 pragma passive(Id).
fibonacci(0,M) ==> M = 1.
fibonacci(1,M) ==> M = 1.
fibonacci(N,M) ==>
N > 1 |
N1 is N-1,
fibonacci(N1,M1),
N2 is N-2,
fibonacci(N2,M2),
M is M1 + M2.
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