[ python-Feature Requests-1684603 ] Add tail recursion

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Feature Requests item #1684603, was opened at 2007-03-20 12:59
Message generated for change (Comment added) made by rhettinger
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>Category: Parser/Compiler
>Group: Python 2.6
>Status: Closed
>Resolution: Wont Fix
Priority: 5
Private: No
Submitted By: Tommy Nordgren (unclezeb)
Assigned to: Nobody/Anonymous (nobody)
Summary: Add tail recursion

Initial Comment:
Consider the following code:
def fac(m):
    def iter(acc,n):
        if n <= 0 :
            return acc
        else:
            return iter(acc * n, n - 1)
    return iter(1,m)

#When called wtih a large parameter, you get exceed the recursion limit

fac(10000)

In a future release, I suggest updating the interpreter and byte code compiler to handle tail recursion properly as in scheme.


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>Comment By: Raymond Hettinger (rhettinger)
Date: 2007-03-20 14:05

Message:
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user_id=80475
Originator: NO

This sort of optimization is one of the many that aren't possible without
changing the semantics of the language.  Recursive calls use a LOAD_GLOBAL
in the function to reference itself.  The value of that global is subject
to change outside the body of the function.



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