> fun f(0) = 0 > | f(1) = 1 > | f(x + 15 handle Overflow => if x mod 2 = 0 then 0 else 1) Did you mean the following? fun f(0) = 0 | f(1) = 1 | f(x) = f(x + 15 handle Overflow => if x mod 2 = 0 then 0 else 1)