0 QTRS
plus(0, x) → x plus(s(x), y) → s(plus(p(s(x)), y)) times(0, y) → 0 times(s(x), y) → plus(y, times(p(s(x)), y)) p(s(0)) → 0 p(s(s(x))) → s(p(s(x))) fac(0, x) → x fac(s(x), y) → fac(p(s(x)), times(s(x), y)) factorial(x) → fac(x, s(0))