RosettaCodeData/Task/Fibonacci-sequence/Prolog/fibonacci-sequence-3.pro

10 lines
303 B
Prolog

%:- dynamic fib/2. % This is ISO, but GNU doesn't like it.
:- dynamic(fib/2). % Not ISO, but works in SWI, YAP and GNU unlike the ISO declaration.
fib(1, 1) :- !.
fib(0, 0) :- !.
fib(N, Value) :-
A is N - 1, fib(A, A1),
B is N - 2, fib(B, B1),
Value is A1 + B1,
asserta((fib(N, Value) :- !)).