Tail recursion to while iteration in 2 easy steps

[Ian Kelly]

On Fri, Oct 4, 2013 at 4:41 AM, Ian Kelly <ian.g.kelly at gmail.com> wrote:
> There is no doubt that it's a tail call.  Whether it is recursion is
> irrelevant to optimizing it.  The reason we talk about "tail call
> recursion" specifically is because the recursive case is the one that
> makes the optimization worthwhile, not because the recursion is
> necessary to perform the optimization.
>
> It is possible that fact is recursive but that some_decorator adds
> additional stack frames that are not tail calls and not optimizable.
> If this were the case, then the recursion would still eventually hit
> the stack limit, but there would still be benefit in optimizing the
> "fact" frames, as it would increase the allowable depth before the
> stack limit is reached.  So I see no reason to check the identity of
> the called function before optimizing the tail call.

On the other hand, if you start optimizing every tail call and not
just the recursive functions, then I can see where that could start to
get problematic for debugging -- as arbitrary functions get removed
from the stack traces just because they happened to end in tail calls.