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Re: Python is not bad ;-)

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On Sun, May 3, 2015 at 1:45 AM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
> On Sat, May 2, 2015 at 5:42 AM, Marko Rauhamaa <marko@pacujo.net> wrote:
>> Christian Gollwitzer <auriocus@gmx.de>:
>>
>>> That's why I still think it is a microoptimization, which helps only
>>> in some specific cases.
>>
>> It isn't done for performance. It's done to avoid a stack overflow
>> exception.
>
> If your tree is balanced, then the number of items you would need to
> have to get a stack overflow exception would be approximately 2 **
> 1000, which you can't possibly hope to fit into memory.
>
> If your tree is unbalanced and you're getting a stack overflow
> exception, then maybe you should think about balancing it.

That's assuming it's a search tree, where you *can* just "think about
balancing it". What if it's a parse tree? Let's say you're walking the
AST of a Python module, looking for all functions that contain 'yield'
or 'yield from' (ie generator functions). To do that, you need to walk
the entire depth of the tree, no matter how far that goes. I'm not
sure how complex a piece of code would have to be to hit 1000, but it
wouldn't be hard to have each level of tree cost you two or three
stack entries, so that could come down to just a few hundred.

However, while that _is_ more likely to produce an unbalanced tree,
it's also that much less capable of being converted into tail
recursion.

ChrisA

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Thread

Python is not bad ;-) Cecil Westerhof <Cecil@decebal.nl> - 2015-04-30 09:07 +0200
  Re: Python is not bad ;-) Ben Finney <ben+python@benfinney.id.au> - 2015-04-30 19:10 +1000
    Re: Python is not bad ;-) Marko Rauhamaa <marko@pacujo.net> - 2015-04-30 13:16 +0300
      Re: Python is not bad ;-) Chris Angelico <rosuav@gmail.com> - 2015-04-30 20:52 +1000
      Re: Python is not bad ;-) Cecil Westerhof <Cecil@decebal.nl> - 2015-04-30 13:30 +0200
        Re: Python is not bad ;-) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-01 17:03 +1000
          Re: Python is not bad ;-) Cecil Westerhof <Cecil@decebal.nl> - 2015-05-01 09:47 +0200
          Re: Python is not bad ;-) Christian Gollwitzer <auriocus@gmx.de> - 2015-05-01 19:56 +0200
          Re: Python is not bad ;-) Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-05-02 19:44 +1200
          Re: Python is not bad ;-) Cecil Westerhof <Cecil@decebal.nl> - 2015-05-02 10:26 +0200
            Re: Python is not bad ;-) Marko Rauhamaa <marko@pacujo.net> - 2015-05-02 12:10 +0300
              Re: Python is not bad ;-) Chris Angelico <rosuav@gmail.com> - 2015-05-02 19:25 +1000
                Re: Python is not bad ;-) Marko Rauhamaa <marko@pacujo.net> - 2015-05-02 12:58 +0300
                Re: Python is not bad ;-) Dave Angel <davea@davea.name> - 2015-05-02 06:22 -0400
                Re: Python is not bad ;-) Chris Angelico <rosuav@gmail.com> - 2015-05-02 20:42 +1000
                Re: Python is not bad ;-) Christian Gollwitzer <auriocus@gmx.de> - 2015-05-02 13:07 +0200
                Re: Python is not bad ;-) Chris Angelico <rosuav@gmail.com> - 2015-05-02 21:21 +1000
                Re: Python is not bad ;-) Christian Gollwitzer <auriocus@gmx.de> - 2015-05-02 13:32 +0200
                Re: Python is not bad ;-) Marko Rauhamaa <marko@pacujo.net> - 2015-05-02 14:42 +0300
                Re: Python is not bad ;-) Ian Kelly <ian.g.kelly@gmail.com> - 2015-05-02 09:45 -0600
                Re: Python is not bad ;-) Chris Angelico <rosuav@gmail.com> - 2015-05-03 01:55 +1000
                Re: Python is not bad ;-) Joonas Liik <liik.joonas@gmail.com> - 2015-05-02 16:50 +0300
                Re: Python is not bad ;-) Joonas Liik <liik.joonas@gmail.com> - 2015-05-02 18:53 +0300
                Re: Python is not bad ;-) Ian Kelly <ian.g.kelly@gmail.com> - 2015-05-02 11:00 -0600
                Re: Python is not bad ;-) Ian Kelly <ian.g.kelly@gmail.com> - 2015-05-02 11:17 -0600
                Re: Python is not bad ;-) Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-05-02 18:22 +0100
              Re: Python is not bad ;-) Cecil Westerhof <Cecil@decebal.nl> - 2015-05-02 12:29 +0200
            Re: Python is not bad ;-) Cecil Westerhof <Cecil@decebal.nl> - 2015-05-02 11:33 +0200
              Re: Python is not bad ;-) Dave Angel <davea@davea.name> - 2015-05-02 06:35 -0400
                Re: Python is not bad ;-) Cecil Westerhof <Cecil@decebal.nl> - 2015-05-02 13:12 +0200
              Re: Python is not bad ;-) Ian Kelly <ian.g.kelly@gmail.com> - 2015-05-02 09:31 -0600
      Re: Python is not bad ;-) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-01 15:56 +1000
    Re: Python is not bad ;-) Cecil Westerhof <Cecil@decebal.nl> - 2015-04-30 13:10 +0200
  Re: Python is not bad ;-) Michael Torrie <torriem@gmail.com> - 2015-04-30 08:03 -0600
    Re: Python is not bad ;-) Cecil Westerhof <Cecil@decebal.nl> - 2015-04-30 18:11 +0200
      Re: Python is not bad ;-) Christian Gollwitzer <auriocus@gmx.de> - 2015-04-30 19:59 +0200
        Re: Python is not bad ;-) Cecil Westerhof <Cecil@decebal.nl> - 2015-04-30 22:05 +0200

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