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Re: order independent hash?

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From Lie Ryan <lie.1296@gmail.com>
Subject Re: order independent hash?
Date Mon, 05 Dec 2011 00:29:15 +1100
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On 12/02/2011 03:29 PM, 88888 Dihedral wrote:
>
> I clear my point a hash is a collection of (key, value) pairs that have
> well defined methods and behavior to be used in programming.
>
> The basic operations of a hash normally includes the following:
>
> 1. insertion of a (key, value) pair  into the hash
> 2. deletion of a (key, value) from the hash
> 3. inquiring  a hash by a key to retrieve the value if the (key, value)
> pair available in the hash. If no key matched, the hash will return
> a not found result.
>
> The hash can grow with (k,v) pairs accumulated in the run time.
> An auto memory management mechanism is required for a hash of a non-fixed size of (k,v) pairs.
>
> Some implementations of a hash might pose some restrictions of k and v
> for some reasons. But in object programming k and v can be objects
> to be manipulated by the programmer.

Strictly speaking, what you're describing is just a dictionary/mapping 
abstract data type (ADT), not a hashtable. Hashtable is a particular way 
to implement the dictionary/mapping ADT. Python's dictionary is 
implemented as hashtable, but there are other ways to implement a 
dictionary/mapping, such as using a sorted tree.

For a data structure to be considered a Hashtable, in addition to having 
the properties of a dictionary that you described, the data structure 
must also uses a "hashing function" to encode the dictionary's keys into 
integer that will be used to calculate the index for the corresponding 
value in its internal array. A hashtable also must provide mechanism to 
deal with hash collisions to maintains its invariants as a dictionary.

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Thread

Re: order independent hash? Peter Otten <__peter__@web.de> - 2011-11-30 13:47 +0100
  Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-01 07:35 -0800
  Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-01 07:35 -0800
    Re: order independent hash? Dave Angel <d@davea.name> - 2011-12-01 10:52 -0500
      Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-01 08:17 -0800
      Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-01 08:17 -0800
    Re: order independent hash? Chris Angelico <rosuav@gmail.com> - 2011-12-02 03:18 +1100
      Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-01 20:29 -0800
        Re: order independent hash? Chris Angelico <rosuav@gmail.com> - 2011-12-02 16:00 +1100
          Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-01 21:48 -0800
            Re: order independent hash? Lie Ryan <lie.1296@gmail.com> - 2011-12-05 00:40 +1100
          Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-01 21:48 -0800
            Re: order independent hash? Roel Schroeven <rschroev_nospam_ml@fastmail.fm> - 2011-12-04 14:41 +0100
              Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-04 07:39 -0800
                Re: order independent hash? Ian Kelly <ian.g.kelly@gmail.com> - 2011-12-04 10:41 -0700
                Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-04 10:06 -0800
                Re: order independent hash? Ian Kelly <ian.g.kelly@gmail.com> - 2011-12-04 13:13 -0700
                Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-04 15:17 -0800
                Re: order independent hash? Matt Joiner <anacrolix@gmail.com> - 2011-12-05 10:21 +1100
                Re: order independent hash? Ian Kelly <ian.g.kelly@gmail.com> - 2011-12-04 16:24 -0700
                Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-04 16:52 -0800
                Re: order independent hash? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-12-05 02:00 +0000
                Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-04 16:52 -0800
                Re: order independent hash? Lie Ryan <lie.1296@gmail.com> - 2011-12-05 12:59 +1100
                Re: order independent hash? Ethan Furman <ethan@stoneleaf.us> - 2011-12-04 18:08 -0800
                Re: order independent hash? Ben Finney <ben+python@benfinney.id.au> - 2011-12-05 15:52 +1100
                Re: order independent hash? Matt Joiner <anacrolix@gmail.com> - 2011-12-05 14:02 +1100
                Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-06 21:24 -0800
                Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-06 21:24 -0800
                Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-04 15:17 -0800
                Re: order independent hash? Terry Reedy <tjreedy@udel.edu> - 2011-12-04 19:28 -0500
                Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-04 10:06 -0800
          Re: order independent hash? Hrvoje Niksic <hniksic@xemacs.org> - 2011-12-02 10:53 +0100
            Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-02 03:48 -0800
            Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-02 09:00 -0800
            Re: order independent hash? Terry Reedy <tjreedy@udel.edu> - 2011-12-02 16:40 -0500
              Re: order independent hash? Hrvoje Niksic <hniksic@xemacs.org> - 2011-12-04 14:55 +0100
                Re: order independent hash? Chris Angelico <rosuav@gmail.com> - 2011-12-05 01:08 +1100
                Re: order independent hash? Hrvoje Niksic <hniksic@xemacs.org> - 2011-12-07 14:28 +0100
                Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-07 09:48 -0800
                Re: order independent hash? Tim Chase <python.list@tim.thechases.com> - 2011-12-04 12:57 -0600
                Re: order independent hash? Hrvoje Niksic <hniksic@xemacs.org> - 2011-12-08 10:30 +0100
                Re: order independent hash? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-12-09 11:27 +0000
                Re: order independent hash? Hrvoje Niksic <hniksic@xemacs.org> - 2011-12-09 17:51 +0100
                Re: order independent hash? Chris Angelico <rosuav@gmail.com> - 2011-12-10 04:13 +1100
                Re: order independent hash? Lie Ryan <lie.1296@gmail.com> - 2011-12-11 10:58 +1100
                Re: order independent hash? Chris Angelico <rosuav@gmail.com> - 2011-12-11 11:17 +1100
                Re: order independent hash? Lie Ryan <lie.1296@gmail.com> - 2011-12-11 14:04 +1100
        Re: order independent hash? Lie Ryan <lie.1296@gmail.com> - 2011-12-05 00:29 +1100
      Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-01 20:29 -0800
      Re: order independent hash? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-12-02 04:33 +0000

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