def fac(n):
	| 0 => 1
	| n => n * fac n

(def fac (n)
	(match 0 (1))
	(match n (n * (fac n))))

def fac(n):
	if n == 0: 1
	else:
		n * fac n

(def fac (n)
	(if (n == 0)
		1
		(n * (fac n))))