call(Next, State0, State1, Head)

The example below uses this predicate to define a lazy list holding the Fibonacci numbers. Our state keeps the two previous Fibonacci numbers.

fibonacci_numbers(L) :-
    lazy_list(fib, state(-,-), L).

fib(state(-,-), state(0,-), 0) :- !.
fib(state(0,-), state(1,0), 1) :- !.
fib(state(P,Q), state(F,P), F) :-
    F is P+Q.

The above can be used to retrieve the Nth Fibonacci number. As fib/2 provides no access to the complete list of Fibonacci numbers, this can be used to generate large Fibonacci numbers.

fib(N, F) :-
    fibonacci_numbers(L),
    nth1(N, L, F).