// Fibonacci number
fibt(r, int a, int b) >< (int n)
| n == 0 => r~1
| n == 1 => r~a
| _ => fibt(r, a+b, a) ~ (n-1);

fibMain(r) >< (int n) => fibt(r, 1, 1) ~ n;

fibMain(r)~9;
r;