Lazy lists in Prolog?

Question

Is it possible to have lazy lists in Prolog? Something like the following:

ones([1 | Y]) :- ones(Y).

Although this obviously doesn\'t work

Answer 1

% A simple generic solution using SWI-Prolog 

% Returns a prefix of a lazy sequence

prefix(Prefix,PrefixLength,LazySequenceName) :-
    apply(LazySequenceName,[LazySequence]),
    length(Prefix,PrefixLength),
    append(Prefix,_,LazySequence).

% Lazy sequence of natural numbers

nat(LazySequence) :- 
    nat(0,LazySequence).
nat(Item,LazySequence) :-
    freeze(LazySequence,
      (LazySequence=[Item|Rest], Next is Item+1, nat(Next,Rest)) ).

% Lazy sequence of Fibonacci numbers

fib(LazySequence) :- 
    fib(1,0,LazySequence).
fib(A,B,LazySequence) :-
    freeze(LazySequence,
       (LazySequence=[C|Rest], C is A+B, fib(B,C,Rest))).

% Examples

test :-
    prefix(N,10,nat), format('Ten first natural numbers: ~w~n',[N]),
    prefix(F,10,fib), format('Ten first Fibonacci numbers: ~w~n',[F]),
    fib(S), nth1(100,S,X), format('The hundredth Fibonacci number: ~w~n',[X]).