From -6911123349293094099 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,e94695845965b249 X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 1992-12-12 09:07:14 PST Newsgroups: comp.std.c++ Path: sparky!uunet!munnari.oz.au!metro!extro.ucc.su.OZ.AU!maxtal From: maxtal@extro.ucc.su.OZ.AU (John MAX Skaller) Subject: Re: Zero-length structures and pointer comparisons Message-ID: <1992Dec12.155417.2628@ucc.su.OZ.AU> Sender: news@ucc.su.OZ.AU Nntp-Posting-Host: extro.ucc.su.oz.au Organization: MAXTAL P/L C/- University Computing Centre, Sydney References: <1992Dec8.103218.27689@lth.se> <9234423.15066@mulga.cs.mu.OZ.AU> <1992Dec9.133956.29659@lth.se> Date: Sat, 12 Dec 1992 15:54:17 GMT Lines: 28 In article <1992Dec9.133956.29659@lth.se> dag@seldon.control.lth.se (Dag Bruck) writes: >In fjh@munta.cs.mu.OZ.AU (Fergus James HENDERSON) writes: >> >>What I propose is that we define a *standard library function* which computes >>a total ordering on pointers. >> >>int compare_pointers(const void *, const void *); >> /* Returns negative, zero, or positive in the same manner as strcmp(). >> Perhaps in the interests of tradition and unreadability it should >> be called ptrcmp() instead of compare_pointers() :-) */ > >Suggested semantics: for any pointers p and q: > > p == q <=> ptrcmp(p,q) == 0 Are you SURE you need this? Why should == and ptrcmp be in any way related? In particular, on the 8086 if ptrcmp was a bitwise compare it would yield a total order, but we would have p == q && ptrcmp(p,q) !=0 -- ;---------------------------------------------------------------------- JOHN (MAX) SKALLER, maxtal@extro.ucc.su.oz.au Maxtal Pty Ltd, 6 MacKay St ASHFIELD, NSW 2131, AUSTRALIA ;--------------- SCIENTIFIC AND ENGINEERING SOFTWARE ------------------