:- module main. :- interface. :- import_module io. :- pred main(io::di, io::uo) is det. :- implementation. :- import_module int. main(!IO) :- factorial(10, Result), io.write_string("Factorial de 10 es: ", !IO), io.write_int(Result, !IO), io.nl(!IO). :- pred factorial(int::in, int::out) is det. factorial(N, Result) :- ( if N = 0 then Result = 1 else factorial(N - 1, SubResult), Result = N * SubResult ).