Re: Trees

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From	Ian Kelly <ian.g.kelly@gmail.com>
Date	Tue, 20 Jan 2015 10:19:40 -0700
Subject	Re: Trees
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On Tue, Jan 20, 2015 at 6:33 AM, Rustom Mody <rustompmody@gmail.com> wrote:
> from enum import Enum
> class TreeTag(Enum):
>     I = 0  # An internal node
>     L = 1  # A leaf node
>     def __repr__(self):  return self.name
>
> I = TreeTag.I
> L = TreeTag.L

Explicitly tagging nodes as internal or leaves is kind of ugly and
also prone to getting out of sync with the reality, which is that a
node is a leaf if it doesn't have any other nodes hanging off of it.

> def dfs(t):
>     if t[0] == L:
>         return [t[1]]
>     else:
>         return [t[1]] + dfs(t[2]) + dfs(t[3])

Over the entire tree, this will do O(n) list additions which implies
O(n) list *copies*, which is rather inefficient. This would probably
be better implemented as a recursive generator.

def dfs(t):
    yield t[0]
    yield from chain.from_iterable(map(dfs, islice(t, 1, None)))

> # Converting to generators is trivial
> =====================

:-)

Thread

Re: Trees Terry Reedy <tjreedy@udel.edu> - 2015-01-20 01:08 -0500
  Re: Trees Marko Rauhamaa <marko@pacujo.net> - 2015-01-20 11:45 +0200
    Re: Trees Paul Rubin <no.email@nospam.invalid> - 2015-01-20 10:14 -0800
      Re: Trees Marko Rauhamaa <marko@pacujo.net> - 2015-01-20 22:26 +0200
    Re: Trees Stephen Hansen <me+python@ixokai.io> - 2015-01-20 23:56 -0800
      Re: Trees Marko Rauhamaa <marko@pacujo.net> - 2015-01-21 10:35 +0200
      Re: Trees Rustom Mody <rustompmody@gmail.com> - 2015-01-21 04:09 -0800
        Re: Trees Chris Angelico <rosuav@gmail.com> - 2015-01-21 23:35 +1100
          Re: Trees Rustom Mody <rustompmody@gmail.com> - 2015-01-21 07:24 -0800
        Re: Trees Tim Chase <python.list@tim.thechases.com> - 2015-01-21 06:55 -0600
        Re: Trees Chris Angelico <rosuav@gmail.com> - 2015-01-22 00:01 +1100
        Re: Trees Tim Chase <python.list@tim.thechases.com> - 2015-01-21 08:26 -0600
        Re: Trees Chris Angelico <rosuav@gmail.com> - 2015-01-22 01:31 +1100
        Re: Trees Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-22 01:47 +1100
          Re: Trees Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-21 09:15 -0700
          Re: Trees Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-21 10:27 -0700
  Re: Trees Rustom Mody <rustompmody@gmail.com> - 2015-01-20 05:33 -0800
    Re: Trees Rustom Mody <rustompmody@gmail.com> - 2015-01-20 05:51 -0800
    Re: Trees Marko Rauhamaa <marko@pacujo.net> - 2015-01-20 16:15 +0200
      Re: Trees Rustom Mody <rustompmody@gmail.com> - 2015-01-20 06:35 -0800
    Re: Trees Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-20 10:19 -0700
      Re: Trees Rustom Mody <rustompmody@gmail.com> - 2015-01-20 10:15 -0800
        Re: Trees Rustom Mody <rustompmody@gmail.com> - 2015-01-20 10:35 -0800
    Re: Trees Mario <marfig@gmail.com> - 2015-01-20 22:47 +0100
      Re: Trees Rustom Mody <rustompmody@gmail.com> - 2015-01-20 17:23 -0800
        Re: Trees Paul Rubin <no.email@nospam.invalid> - 2015-01-20 17:49 -0800
          Re: Trees Rustom Mody <rustompmody@gmail.com> - 2015-01-20 18:03 -0800
            Re: Trees Paul Rubin <no.email@nospam.invalid> - 2015-01-21 14:27 -0800
              Re: Trees Rustom Mody <rustompmody@gmail.com> - 2015-01-21 21:17 -0800
        Re: Trees Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-21 15:54 -0700
          Re: Trees Rustom Mody <rustompmody@gmail.com> - 2015-01-21 21:20 -0800
            Re: Trees Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-22 00:01 -0700
            Re: Trees Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-21 23:56 -0700
          Re: Trees Paul Rubin <no.email@nospam.invalid> - 2015-01-21 23:16 -0800
            Re: Trees Rustom Mody <rustompmody@gmail.com> - 2015-01-22 08:54 -0800
      Re: Trees Terry Reedy <tjreedy@udel.edu> - 2015-01-20 21:19 -0500
        Re: Trees Mario Figueiredo <marfig@gmail.com> - 2015-01-21 14:05 +0000

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