NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c-part2/13290

Internet Message Format | 1996-08-05 | 1.6 KB

Path: solon.com!not-for-mail
From: [e-mail] (Konrad Schwarz)
Newsgroups: comp.lang.c,comp.lang.c.moderated,hp.unix,comp.sys.hp.apps,comp.sys.hp.hpux
Subject: Re: C coding problem
Date: 6 Apr 1996 08:41:56 -0600
Organization: TU Wien
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Approved: [e-mail]
Message-ID: <4k5vrk$[e-mail]>
References: <4j06na$[e-mail]> <4jttan$[e-mail]> <4jv6st$[e-mail]> <4k1qh3$[e-mail]>
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In article <4k1qh3$[e-mail]>, [e-mail] writes:

|> However it is not always so that the machine does a distinct
|> add or multiply in order to handle a[i].  The "*p++" idiom may look
|> shot in the C code, and on a PDP-11 it usually resulted in nice
|> short code.  However, there is no guarentee that this is true of all
|> hardware.  It is not all that uncommon to have an architecture where
|> adding 1 to an int is much cheaper than adding one to a pointer,

Examples?  The dominant trend in computer architecture seems to be the
reduced instruction set with simple addressing modes; Mips and Alpha
are two architectures that do not have an indexed addressing mode.

|> In such and environment,
|>       *q++ = *p++;
|> loses badly to
|>       q[i] = p[i], ++i;
|> if the hardware indexing works in terms of the objects being
|> referenced.

Note that indexed addressing often works only for small
powers of two, e.g., x86 family.

|> Pointer notation can greatly reduce program
|> clutter so you can see what is happening.

Agreed. :)

Konrad Schwarz