; Function to compute the greatest common divisor of two non-negative integers. 
; Based on Euclidean algorithm. Recursive Scheme version.
(define gcd
  (lambda (a b)
    (if (= b 0)
    	a
    	(gcd b (modulo a b)))))

; Iterative Scheme version.
(define gcd
  (lambda (a b)
    (do ((c 0))					; local variable c initialized to 0
    	((= b 0) a)				; loop until b is 0; then return a
    	(set! c (modulo a b))	; three expressions in body of loop
    	(set! a b)
    	(set! b c))))

# Yuck. That Scheme loop is unholy. Recursive Python version.
def gcd(a, b):
    if b == 0:
        return a
    else:
        return gcd(b, a % b)

# Iterative Python version.
def gcd(a, b):
	while (b != 0):
		c = a % b
		a = b
		b = c
	return a