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From: random832@fastmail.us
To: Terry Reedy <tjreedy@udel.edu>, python-list@python.org
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Subject: Re: Tail recursion to while iteration in 2 easy steps
Date: Thu, 03 Oct 2013 10:09:25 -0400
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Xref: csiph.com comp.lang.python:55411

On Wed, Oct 2, 2013, at 17:33, Terry Reedy wrote:
> 5. Conversion of apparent recursion to iteration assumes that the 
> function really is intended to be recursive.  This assumption is the 
> basis for replacing the recursive call with assignment and an implied 
> internal goto. The programmer can determine that this semantic change is 
> correct; the compiler should not assume that. (Because of Python's late 
> name-binding semantics, recursive *intent* is better expressed in Python 
> with iterative syntax than function call syntax. )

Speaking of assumptions, I would almost say that we should make the
assumption that operators (other than the __i family, and
setitem/setattr/etc) are not intended to have visible side effects. This
would open a _huge_ field of potential optimizations - including that
this would no longer be a semantic change (since relying on one of the
operators being allowed to change the binding of fact would no longer be
guaranteed).