Adding through recursion

[martin.clausen@gmail.com]

There is problaly a really simple answer to this, but why does this
function print the correct result but return "None":

def add(x, y):
if x == 0:
print y
return y
else:
x -= 1
y += 1
add(x, y)

print add(2, 4)

result:
6
None

Martin