Iterative vs. Recursive coding

[John Bokma]

Steven D'Aprano <steve at REMOVE-THIS-cybersource.com.au> writes:

> On Sat, 21 Aug 2010 19:09:52 -0500, John Bokma wrote:
>
>> this means that Python should eliminate / optimize tail
>> recursion.
>
> There have been various suggestions to add tail recursion optimization to 
> the language. Two problems:

[snip]

> But this is not the only sort of tail-call recursion, and a traceback 
> like the following is useful:
>
>
>>>> recurse(4)
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
>   File "<stdin>", line 5, in recurse
>   File "<stdin>", line 3, in f
>   File "<stdin>", line 5, in recurse
>   File "<stdin>", line 3, in f
>   File "<stdin>", line 5, in recurse
>   File "<stdin>", line 3, in f
>   File "<stdin>", line 4, in recurse
>   File "<stdin>", line 2, in g
> ValueError
>
>
> If all you saw was the last line (the call to g), debugging the exception 
> would be significantly harder.

Yup, agreed, good example.

> Me personally, I'd like to see either a (preferably) run-time setting or 
> compile-time switch that enables/disables this optimization. Even an 
> explicit decorator would be fine. And lo and behold:
>
> http://hircus.wordpress.com/2008/06/21/python-tail-call-optimization-done-right/
> http://groups.google.com/group/comp.lang.python/msg/9b047d1392f2b8ec
>
>
> Add it to your bag of tricks and have fun.

Thanks for the links. And yes, I will add this to my bag of tricks
(aka local wiki with notes ;-) ).


-- 
John Bokma                                                               j3b

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