From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Thread: 103376,703c4f68db81387d X-Google-Thread: 109fba,703c4f68db81387d X-Google-Thread: 115aec,703c4f68db81387d X-Google-Thread: f43e6,703c4f68db81387d X-Google-Attributes: gid103376,gid109fba,gid115aec,gidf43e6,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news1.google.com!news4.google.com!news.glorb.com!newsfeed00.sul.t-online.de!t-online.de!tsicnews.teliasonera.com!news.otenet.gr!news.grnet.gr!newsfd02.forthnet.gr!not-for-mail From: Ioannis Vranos Newsgroups: comp.lang.ada,comp.lang.c++,comp.realtime,comp.software-eng Subject: Re: Teaching new tricks to an old dog (C++ -->Ada) Date: Thu, 24 Mar 2005 04:47:16 +0200 Organization: FORTHnet S.A., Atthidon 4, GR-17671 Kalithea, Greece, Tel: +30 2109559000, Fax: +30 2109559333, url: http://www.forthnet.gr Message-ID: <1111632436.374702@athnrd02> References: <4229bad9$0$1019$afc38c87@news.optusnet.com.au> <871xau9nlh.fsf@insalien.org> <3SjWd.103128$Vf.3969241@news000.worldonline.dk> <87r7iu85lf.fsf@insalien.org> <1110052142.832650@athnrd02> <1110284070.410136.205090@o13g2000cwo.googlegroups.com> <395uqaF5rhu2mU1@individual.net> <1110329098.642196@athnrd02> <1110361741.551255@athnrd02> <422edaec$0$26554$9b4e6d93@newsread4.arcor-online.net> <1111464133.508323@athnrd02> <423fe9df$0$11476$9b4e6d93@newsread2.arcor-online.net> <1111521825.653841@athnrd02> <424094b0$0$11481$9b4e6d93@newsread2.arcor-online.net> <1111568404.687226@athnrd02> <42416659$0$11476$9b4e6d93@newsread2.arcor-online.net> <1111611226.253249@athnrd02> <4241f47a$0$24073$9b4e6d93@newsread4.arcor-online.net> <1111627358.387482@athnrd02> <424222df$0$24057$9b4e6d93@newsread4.arcor-online.net> NNTP-Posting-Host: athnrd02.forthnet.gr Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Trace: athprx02.forthnet.gr 1111632436 14939 193.92.150.73 (24 Mar 2005 02:47:16 GMT) X-Complaints-To: abuse@forthnet.gr NNTP-Posting-Date: Thu, 24 Mar 2005 02:47:16 +0000 (UTC) User-Agent: Mozilla Thunderbird 1.0 (Windows/20041206) X-Accept-Language: en-us, en In-Reply-To: <424222df$0$24057$9b4e6d93@newsread4.arcor-online.net> Cache-Post-Path: newsfd02!unknown@ppp16-adsl-51.ath.forthnet.gr Xref: g2news1.google.com comp.lang.ada:9876 comp.lang.c++:46977 comp.realtime:1662 comp.software-eng:5268 Date: 2005-03-24T04:47:16+02:00 List-Id: Georg Bauhaus wrote: > You say "of course" now? I don't really understand then > why you asked me why my Ada _array_ code is faster than your > C++ std::_map_ code. I suppose I did not notice that you were comparing with std::map at that point. Direct comparison of an Ada fixed size array should be vs vector or better, valarray. > Actually, there is no negative index in your example. > There are some offset computations, resulting in index > values no less than 0. > By the same argument I could say that a 10-element > C-array can be indexed by the number 100000 by first > decrementing the pointer and then adding 100000 as an > offset. But you do not get the element number 100000, > because there is no such element. Actually this example produces undefined behaviour, since valid behaviour is to point/access within the sequence or point (and not access) one past the end element of the sequence. But in a case where vector vec(10); vector::iterator pi= vec.begin()+4; // ... pi[-2]= 4; it accesses an actual object (there is an actual object) there. I can not understand why in an array with index range [-200, -100] there is an object in -199 "more" than the example above. > Index types are conceptually different from offsets from > the first element. In C++, index is always (has the notion of) an offset. > As a clever trick, this is nice though. I like the power > of assembly think. Yes I think it's cool too. :-) Not to mention that we can treat any part of a built in array or an object as a sequence of unsigned chars (bytes). -- Ioannis Vranos http://www23.brinkster.com/noicys