Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!gegeweb.org!de-l.enfer-du-nord.net!feeder2.enfer-du-nord.net!tudelft.nl!txtfeed1.tudelft.nl!multikabel.net!newsfeed20.multikabel.net!news2.euro.net!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Return-Path: <python.list@tim.thechases.com>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.002
X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'suppose': 0.05; 'python': 0.08; 'dict': 0.09; 'folks': 0.15; '(modulo': 0.16; '-tkc': 0.16; 'from:addr:python.list': 0.16; 'from:addr:tim.thechases.com': 0.16; 'from:name:tim chase': 0.16; 'message- id:@tim.thechases.com': 0.16; 'okay,': 0.16; 'received:70.251': 0.16; 'received:dsl.rcsntx.swbell.net': 0.16; 'received:rcsntx.swbell.net': 0.16; 'received:swbell.net': 0.16; 'subject:independent': 0.16; 'values?': 0.16; 'cc:addr:python- list': 0.16; 'wrote:': 0.18; 'cc:no real name:2**0': 0.20; 'header :In-Reply-To:1': 0.22; 'interface': 0.23; 'tree.': 0.23; 'cc:2**0': 0.24; 'tree': 0.25; 'classes': 0.26; 'tried': 0.27; 'work.': 0.28; 'cc:addr:python.org': 0.29; 'hash': 0.30; "it'd": 0.30; 'chris': 0.30; 'subject:?': 0.31; 'implement': 0.32; 'header :User-Agent:1': 0.33; 'rather': 0.33; 'probably': 0.34; 'surprised': 0.34; 'things,': 0.37; 'but': 0.37; 'reasons': 0.37; 'useful': 0.38; 'correctly': 0.39; "couldn't": 0.39; 'define': 0.39; 'might': 0.40; 'addressing': 0.67; 'comply': 0.67; 'perspective,': 0.84; 'technically': 0.93
Date: Sun, 04 Dec 2011 12:57:50 -0600
From: Tim Chase <python.list@tim.thechases.com>
User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.24) Gecko/20111120 Icedove/3.1.16
MIME-Version: 1.0
To: Chris Angelico <rosuav@gmail.com>
Subject: Re: order independent hash?
X-Priority: 4 (Low)
References: <jb57p7$b1j$1@dough.gmane.org>	<mailman.3156.1322657239.27778.python-list@python.org>	<30715729.411.1322753732534.JavaMail.geo-discussion-forums@pret21>	<4ED7A2CE.6070306@davea.name>	<mailman.3203.1322756312.27778.python-list@python.org>	<6366868.86.1322800180523.JavaMail.geo-discussion-forums@pret21>	<mailman.3216.1322802013.27778.python-list@python.org>	<87k46fb8pg.fsf@xemacs.org>	<mailman.3239.1322862043.27778.python-list@python.org>	<87aa78bfvv.fsf@xemacs.org> <CAPTjJmqrYLnhgCCDW3FdjOyqyUttW3cZu-=S1eW30217djgY8Q@mail.gmail.com>
In-Reply-To: <CAPTjJmqrYLnhgCCDW3FdjOyqyUttW3cZu-=S1eW30217djgY8Q@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
X-AntiAbuse: This header was added to track abuse, please include it with any abuse report
X-AntiAbuse: Primary Hostname - boston.accountservergroup.com
X-AntiAbuse: Original Domain - python.org
X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12]
X-AntiAbuse: Sender Address Domain - tim.thechases.com
X-Source: 
X-Source-Args: 
X-Source-Dir: 
Cc: python-list@python.org
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe: <http://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive: <http://mail.python.org/pipermail/python-list>
List-Post: <mailto:python-list@python.org>
List-Help: <mailto:python-list-request@python.org?subject=help>
List-Subscribe: <http://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups: comp.lang.python
Message-ID: <mailman.3277.1323025080.27778.python-list@python.org>
Lines: 23
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1323025080 news.xs4all.nl 6908 [2001:888:2000:d::a6]:49220
X-Complaints-To: abuse@xs4all.nl
Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:16624

On 12/04/11 08:08, Chris Angelico wrote:
> 2011/12/5 Hrvoje Niksic<hniksic@xemacs.org>:
>> If a Python
>> implementation tried to implement dict as a tree, instances of classes
>> that define only __eq__ and __hash__ would not be correctly inserted in
>> such a dict.
>
> Couldn't you just make a tree of hash values? Okay, that's probably
> not the most useful way to do things, but technically it'd comply with
> the spec.

 From an interface perspective, I suppose it would work.  However 
one of the main computer-science reasons for addressing by a hash 
is to get O(1) access to items (modulo pessimal hash 
structures/algorithms which can approach O(N) if everything 
hashes to the same value/bucket), rather than the O(logN) time 
you'd get from a tree. So folks reaching for a hash/map might be 
surprised if performance degraded with the size of the contents.

-tkc