From -5618769921869759875 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,e94695845965b249 X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 1992-12-16 20:23:52 PST Newsgroups: comp.std.c++ Path: sparky!uunet!elroy.jpl.nasa.gov!usc!zaphod.mps.ohio-state.edu!uunet.ca!frumious!pat From: pat@frumious.uucp (Patrick Smith) Subject: Re: Zero-length structures and pointer comparisons Message-ID: Date: Thu, 17 Dec 1992 00:08:15 GMT Reply-To: uunet.ca!frumious!pat References: <1992Dec9.191606.5665@lucid.com> <1992Dec16.202711.22367@bcrka451.bnr.ca> Organization: None Lines: 36 sjm@bcrki65.bnr.ca (Stuart MacMartin) writes: |In article pat@frumious.uucp (Patrick Smith) writes: |> |>jss@lucid.com (Jerry Schwarz) writes: |>|And |>| |>| if p < q is defined, ptrcmp(p,q) < 0 <=> p < q |> |> |>This strikes me as nice to have, but not essential. | |It makes me nervous to disagree with you, but haven't we already |hammered to death the concept that p < q might be defined (but |not generate a total ordering) if some ps and qs are not in the |same segment? Or do the PC compilers only permit p < q for ps |and qs in the same array? Please don't be nervous, Stuart! I make _lots_ of mistakes. (No smiley here, because it's quite true.) This seems to depend on what one means by "p < q is defined". I can't say what Jerry meant, but (without thinking about it too much), I took him to mean something something like "if the standard defines what p < q means". Which I _thought_ meant p and q had to point to objects in the same array or subobjects of the same object. And p < q does have to behave as expected in those cases (with some of the "subobjects of the same object" cases being legal exceptions). The emphasis on _thought_ is because then I looked at the draft standard. More on that in another posting... -- Patrick Smith uunet.ca!frumious!pat pat%frumious.uucp@uunet.ca