Re: mu TECH: an unhurried digression on C pointers vs. arrays

From: Alfie Costa (
Date: Wed May 03 2000 - 22:04:07 CEST

On 28 Apr 2000, at 17:58, Miguel Angel <> wrote:

> To notice such subtle difference (if there is any at all) is better to write the
> loop repeating many times the inner sentences (unless you are also testing the
> loop).

OK, I have tried this. I defined the code like so:

#define C1 line[j]=z;n=line[j];j++;line[j]=y;n=line[j];j--;
#define C2 *l=z;n=*l++;*l=y;n=*l--;

...then inserted about about 150 'C1's and 'C2's in each loop. The result was
that the loop with the pointers really did turn out to be faster, around 30-50%
if I recall correctly -- whatever the exact figure was, the pointers were
always faster. The code was tested with 'gcc', I haven't tried that old Turbo C
compiler yet.
Naturally this was a surprise, given the previous confusing results which used
much more loop overhead. Thanks again for suggesting this.

If anyone wants the code, I'll e-mail it on request...

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