[Python-Dev] Proper tail recursion (original) (raw)

Andrew Koenig ark-mlist at att.net
Fri Jul 16 16:11:52 CEST 2004

I think it's pretty hard to come up with a problem where the natural solution is tail recursive.

I might agree with you that it isn't easy to come up with a problem where the natural problem is entirely tail recursive -- but my original tree-traversal example is tail-recursive and I think it's more natural to write it that way than it is to eliminate the tail recursion (leaving the other recursion) by hand.

I've also seen examples of functions that begin like this:

def foo(x, y):
    if x < 0:
        return foo(-x, -y)
    ...

which I think is clearer than

def foo(x, y)
    if x < 0:
        x = -x
        y = -y
    ...

especially if there are several such cases to consider. Of course there isn't much to gain by removing this particular tail recursion, but nevertheless it is a tail recursion that I think is more natural to leave in place.

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