tail-rec decorator, well still blows the stack...

[David Wahler]

On Mon, Jul 21, 2008 at 10:01 PM, ssecorp <circularfunc at gmail.com> wrote:
> http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/496691
>
> so I try it and when I run:
> @Decorators.tail_recursion
> def fibtr(n):
>    def fibt(a, b, n):
>        if n <= 1:
>            return b
>        else:
>            return fibt(b, a + b, n - 1)
>    if n == 0:
>        return 0
>    else:
>        return fibt(0, 1, n);
>
> it still blows the stack. so what is the point? is it impossible to
> get "real" tail-recursion in Python?

Python does not perform tail-call elimination, and there are currently
no plans to make it do so. See
http://mail.python.org/pipermail/python-dev/2004-July/046171.html and
the ensuing discussion for an explanation.