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Re: Trees

From Paul Rubin <no.email@nospam.invalid>
Newsgroups comp.lang.python
Subject Re: Trees
Date 2015-01-20 17:49 -0800
Organization A noiseless patient Spider
Message-ID <87iog0aonw.fsf@jester.gateway.sonic.net> (permalink)
References <CAG=hEY1L-39EmuWpdEh_n-BNfs=qG9nL=MrMT0ar72yGBrkoUA@mail.gmail.com> <mailman.17884.1421734095.18130.python-list@python.org> <d34dbfbe-fe82-47dc-8bc3-c8773e2b70dd@googlegroups.com> <MPG.2f28eb55d73ef68c989680@nntp.aioe.org> <ba69cad8-68c0-421e-af79-e381ca179015@googlegroups.com>

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Rustom Mody <rustompmody@gmail.com> writes:
> ## The depth first algorithm
> dfs (L x)   = [x]
> dfs (B x lst rst) = [x]  ++  dfs lst  ++  dfs rst

Cute.  I can't resist posting the similar breadth first algorithm:

bfs (L x)   = [x]
bfs (B x lst rst) = bfs lst  ++ [x] ++  bfs rst

> *Main> dfs t
> [6,2,1,4,3,5,8,7,9]

*Main> bfs t
[1,2,3,4,5,6,7,8,9]

> The Haskell is bullseye¹ in capturing the essense of a tree because
> conceptually a tree of type t is recursive in the sense that it can contain
> 2 subtrees -- (B x lst rst) -- or its a base case -- L x.

You might like this discussion of a red-black tree implementation whose
datatype makes sure the RB tree invariants are preserved.  The data
definition is kind of verbose, but with more recent GHC versions it can
be made a lot crisper, with datakinds and type-level numeric literals.

https://www.reddit.com/r/haskell/comments/ti5il/redblack_trees_in_haskell_using_gadts_existential/

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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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