Created
          January 26, 2013 21:33 
        
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    Prolog definition of infinite Fibonacci sequence
  
        
  
    
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  | ?- fibs(F), take(F, 20, _). | |
| F = [0, 1, 1, 2, 3, 5, 8, 13, 21|...], | |
| freeze(_G2395, zip_with(plus, [2584, 4181|_G2395], [4181|_G2395], _G2395)). | 
  
    
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  | zip_with(_, [], []). | |
| zip_with(Goal, [A|As], [B|Bs], [C|Cs]) :- | |
| call(Goal, A, B, C), | |
| freeze(Cs, zip_with(Goal, As, Bs, Cs)). | |
| % implementation from SWI pack list_util | |
| take([], N, []) :- | |
| N > 0, | |
| !. | |
| take(_, 0, []) :- | |
| !. | |
| take([H|T], N1, [H|Rest]) :- | |
| N1 > 0, | |
| succ(N0, N1), | |
| take(T, N0, Rest). | |
| % infinite, lazy Fibonacci sequence | |
| fibs([0,1|T]) :- | |
| F = [0,1|T], | |
| F1 = [1|T], | |
| freeze(T, zip_with(plus, F, F1, T)). | 
  
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For anyone finding this later, list_util's iterate/3 makes it quite natural to create infinite, lazy lists:
Can be used like this: