Adding through recursion

[martin.clausen at 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