Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!texbell!ficc!peter
From: peter@ficc.uu.net (Peter da Silva)
Newsgroups: comp.lang.c
Subject: Re: Pointer arithmetic and comparisons.
Message-ID: <7302@ficc.uu.net>
Date: 14 Dec 89 14:25:24 GMT
References: <257ECDFD.CDD@marob.masa.com> <232@bohra.cpg.oz> <2908@murtoa.cs.mu.oz.au> <2241@dataio.Data-IO.COM>
Reply-To: peter@ficc.uu.net (Peter da Silva)
Organization: Xenix Support, FICC
Lines: 14

> <Now a beef.  Why check for (p <= pend)?  Why not just ( p == pend) ?

In article <2241@dataio.Data-IO.COM> bright@dataio.Data-IO.COM (Walter Bright) writes:
> (p <= pend) generates more efficient code (on PC's) than (p == pend), because
> on the former only the offset portions of the pointer need to be compared,
> while on the latter both the segment and the offset must be compared.

Implementation-dependent micro-optimisation isn't a good reason. A good
one is that !p <= pend! is a broader termination condition, and thus safer.
-- 
`-_-' Peter da Silva. +1 713 274 5180. <peter@ficc.uu.net>.
 'U`  Also <peter@ficc.lonestar.org> or <peter@sugar.lonestar.org>.
"Scientific progress is predicated on name-calling and intolerance, not to
 mention asking lots of stupid questions." -- Mark S Madsen