Path: csiph.com!newsfeed.hal-mli.net!feeder3.hal-mli.net!newsfeed.hal-mli.net!feeder1.hal-mli.net!newsfeed.xs4all.nl!newsfeed4.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Return-Path: <python-python-list@m.gmane.org>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.000
X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'encoding': 0.05; 'string.': 0.05; '*not*': 0.07; 'utf-8': 0.07; 'string': 0.09; 'assuming': 0.09; 'lookup': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'scheme.': 0.09; 'strings.': 0.09; 'width': 0.09; 'python': 0.11; 'jan': 0.12; 'posted': 0.15; 'easier.': 0.16; 'encodings,': 0.16; 'lookups.': 0.16; 'notation,': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'reedy': 0.16; 'slice.': 0.16; 'slow,': 0.16; 'subject:unicode': 0.16; 'so.': 0.16; 'wrote:': 0.18; 'variable': 0.18; 'coding': 0.22; 'header:User-Agent:1': 0.23; 'unicode': 0.24; 'least': 0.26; 'header:X-Complaints-To:1': 0.27; 'header:In-Reply-To:1': 0.27; 'michael': 0.29; 'chris': 0.29; 'am,': 0.29; 'array': 0.29; "i'm": 0.30; 'comments': 0.31; 'languages': 0.32; 'says': 0.33; 'cases': 0.33; 'but': 0.35; 'method': 0.36; 'similar': 0.36; 'should': 0.36; 'application': 0.37; 'being': 0.38; 'to:addr:python-list': 0.38; 'does': 0.39; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'space': 0.40; 'days': 0.60; 'ago,': 0.61; 'ago.': 0.61; 'length': 0.61; 'received:173': 0.61; 'more': 0.64; 'below.': 0.71; 'received:fios.verizon.net': 0.84; 'unacceptable': 0.84
X-Injected-Via-Gmane: http://gmane.org/
To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: FSR and unicode compliance - was Re: RE Module Performance
Date: Sun, 28 Jul 2013 13:36:00 -0400
References: <mailman.4618.1373613834.3114.python-list@python.org> <571a6dfe-fd66-42cf-92fc-8b97cbe6e9e4@googlegroups.com> <51DFDE65.5040001@Gmail.com> <CAN1F8qUFP3uX57HhiiUPaYqO3h_HiT8Q_YD=vCYky3EAWsdE7Q@mail.gmail.com> <mailman.4666.1373670835.3114.python-list@python.org> <4f1067f6-bc99-42ad-9166-37fb228b90e8@googlegroups.com> <mailman.5094.1374759404.3114.python-list@python.org> <51f14395$0$29971$c3e8da3$5496439d@news.astraweb.com> <mailman.5106.1374766576.3114.python-list@python.org> <51f15e03$0$29971$c3e8da3$5496439d@news.astraweb.com> <mailman.5127.1374808181.3114.python-list@python.org> <8203e802-9dc5-44c5-9547-6e1947ee224b@googlegroups.com> <mailman.5160.1374890711.3114.python-list@python.org> <f4bb2528-930e-4c0a-820e-66f00ac2b5b6@googlegroups.com> <51F53E4F.8080104@gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
X-Gmane-NNTP-Posting-Host: pool-173-75-251-66.phlapa.fios.verizon.net
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130620 Thunderbird/17.0.7
In-Reply-To: <51F53E4F.8080104@gmail.com>
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.15
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.5193.1375032989.3114.python-list@python.org>
Lines: 33
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1375032989 news.xs4all.nl 15997 [2001:888:2000:d::a6]:43732
X-Complaints-To: abuse@xs4all.nl
Xref: csiph.com comp.lang.python:51389

On 7/28/2013 11:52 AM, Michael Torrie wrote:
>
> 3. UTF-8 and UTF-16 encodings, being variable width encodings, mean that
> slicing a string would be very very slow,

Not necessarily so. See below.

> and that's unacceptable for
> the use cases of python strings.  I'm assuming you understand big O
> notation, as you talk of experience in many languages over the years.
> FSR and UTF-32 both are O(1) for slicing and lookups.

Slicing is at least O(m) where m is the length of the slice.

> UTF-8, 16 and any variable-width encoding are always O(n).\

I posted about a week ago, in response to Chris A., a method by which 
lookup for UTF-16 can be made O(log2 k), or perhaps more accurately, 
O(1+log2(k+1)), where k is the number of non-BMP chars in the string.

This uses an auxiliary array of k ints. An auxiliary array of n ints 
would make UFT-16 lookup O(1), but then one is using more space than 
with UFT-32. Similar comments apply to UTF-8.

The unicode standard says that a single strings should use exactly one 
coding scheme. It does *not* say that all strings in an application must 
use the same scheme. I just rechecked a few days ago. It also does not 
say that an application cannot associate additional data with a string 
to make processing of the string easier.

-- 
Terry Jan Reedy