From 1250259243162651489 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,bf65828a2bbbc32e X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 1993-12-13 15:41:20 PST Path: gmd.de!urmel.informatik.rwth-aachen.de!hathi!dak From: dak@hathi.informatik.rwth-aachen.de (David Kastrup) Newsgroups: comp.std.c++ Subject: Re: bool run-time performance impact Date: 13 Dec 1993 18:04:13 GMT Organization: Rechnerbetrieb Informatik - RWTH Aachen Lines: 21 Distribution: world Message-ID: <2eiaqt$s87@urmel.informatik.rwth-aachen.de> References: <9334701.20716@mulga.cs.mu.OZ.AU> <2eh58b$fg6@nic.lth.se> NNTP-Posting-Host: hathi.informatik.rwth-aachen.de Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Keywords: bool dag@control.lth.se (Dag Bruck) writes: >In fjh@munta.cs.mu.OZ.AU (Fergus Henderson) writes: >>It would be quite reasonable for compilers to use a non-canonical >>representation where anything non-zero is true. In this case, >>conversion from int to bool would be a no-op. >Not quite; the proposal explicitly says that a bool, when promoted to >int, yields the values 0 or 1. Well, what of it? Which of the two conversions has the work of unifying was not specified, or was it? Is it told anywhere that a pointer to a true bool has to convert to a pointer to a numeric 1? Certainly not. And the representation might differ between CPUs. For 68xxx, I could imagine using the byte 0xff for true, 0x00 for false, and usually bytewise logical operations for logic, if that proves faster and without sideeffect. -- David Kastrup dak@pool.informatik.rwth-aachen.de Tel: +49-241-72419 Fax: +49-241-79502 Goethestr. 20, D-52064 Aachen