fibonacci iterative - a problem

From: Grzegorz Rumatowski (grumatow_at_ZERO__SPAMpoczta.onet.pl)
Date: 11/26/03 

Date: Wed, 26 Nov 2003 19:35:01 +0100

Hello NewsGroup!

Because a recursive definition of fibonacci predicate has some limitations,
I've defined following iterative predicate:

fib(0,1).
fib(1,1).
fib(N,F) :- N > 1, fib(N,1,1,F)

fib(2,F1,F2,F) :- F is F1 + F2.
fib(N,F1,F2,F) :- N > 2, N1 is N - 1, NF1 is F1 + F2,
    fib(N1,NF1,F1,F).

The problem is: it's not workin' at all. Any ideas? 

-- 
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for Calculation and Hazardous Utility
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