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!news3.google.com!news.glorb.com!news-in.ntli.net!newsrout1-win.ntli.net!ntli.net!newspeer1-win.ntli.net!newsfe5-gui.ntli.net.POSTED!53ab2750!not-for-mail From: "Dr. Adrian Wrigley" Subject: Re: [OT] Re: Teaching new tricks to an old dog (C++ -->Ada) User-Agent: Pan/0.14.2 (This is not a psychotic episode. It's a cleansing moment of clarity.) Message-Id: Newsgroups: comp.lang.ada,comp.lang.c++,comp.realtime,comp.software-eng References: <4229bad9$0$1019$afc38c87@news.optusnet.com.au> <1110032222.447846.167060@g14g2000cwa.googlegroups.com> <871xau9nlh.fsf@insalien.org> <3SjWd.103128$Vf.3969241@news000.worldonline.dk> <87r7iu85lf.fsf@insalien.org> <1110052142.832650@athnrd02> <42309456$1@news.broadpark.no> <4232ab3a$0$26547$9b4e6d93@newsread4.arcor-online.net> <1110825790.396769@athnrd02> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Date: Mon, 14 Mar 2005 19:29:25 GMT NNTP-Posting-Host: 81.100.88.147 X-Complaints-To: http://www.ntlworld.com/netreport X-Trace: newsfe5-gui.ntli.net 1110828565 81.100.88.147 (Mon, 14 Mar 2005 19:29:25 GMT) NNTP-Posting-Date: Mon, 14 Mar 2005 19:29:25 GMT Organization: ntl Cablemodem News Service Xref: g2news1.google.com comp.lang.ada:9378 comp.lang.c++:45631 comp.realtime:1460 comp.software-eng:5027 Date: 2005-03-14T19:29:25+00:00 List-Id: On Mon, 14 Mar 2005 20:43:08 +0200, Ioannis Vranos wrote: > Dr. Adrian Wrigley wrote: > >> the problem as I suggested in my previous post is that you have to >> pass in the comparison operator or hash function down the tree >> of template/generic instantiation, (composing them along the way) >> if you want to use maps/hashes. > > In the standard library containers and algorithms case you do not pass > any function to the container. operator< is implicitly used. The comparison operator here seems to be a generic formal function parameter with a default value. This must be available at instantiation. The operator becomes part of the interface (implicitly or explicitly) for any code instantiating the std::map. Where does the code for the comparison operator go? It *has* to go at the point the class is defined. This could be at the other end of a hierarchy of generic instantiations. The result is that the implementation requirement (needs a comparison operator) has propagated up the generic hierarchy to some otherwise completely independent code as an interface requirement. I'm sorry I can't explain this any better! (should I give a code example?) -- Adrian