Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!yale!cmcl2!kramden.acf.nyu.edu!brnstnd
From: brnstnd@kramden.acf.nyu.edu (Dan Bernstein)
Newsgroups: comp.lang.c
Subject: Re: p[1] vs. *(p+1)
Message-ID: <29605:Aug3120:51:0290@kramden.acf.nyu.edu>
Date: 31 Aug 90 20:51:02 GMT
References: <26D952F5.4E44@tct.uucp> <1745@io.UUCP> <1990Aug31.190103.15043@laguna.ccsf.caltech.edu>
Organization: IR
Lines: 17

In article <1990Aug31.190103.15043@laguna.ccsf.caltech.edu> bruce@seismo.gps.caltech.edu (Bruce Worden) writes:
> In article <1745@io.UUCP> prs@eng.ileaf.com (Paul Schmidt) writes:
> >I must confess that I use p[1] in these cases, and count on the compiler
> >to optimize for me.
> In a simple case like p[1] the compiler may well optimize, but then it isn't 
> a particularly time consuming operation.

Huh? p[1] means exactly the same thing as *(p+1). At least two compilers
here (neither pcc-based) do that translation as the very first step.
There's no ``optimization'' involved.

>    *p1++ = *a1++ * *b1++;  
>     p2[i] = a2[i] * b2[i]; 

Note that on vector machines the latter is much faster in a loop.

---Dan