From: Nathan_Johnson AT mail DOT tmmna DOT com
To: djgpp AT delorie DOT com
Message-ID: <852564EA.004B7F0B.00@mail.tmmna.com>
Date: Tue, 5 Aug 1997 09:52:31 -0400
Subject: djgpp daily digest for 04 Aug 1997 2/4
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==============
 Chad Catlett
 dwi AT netc DOT com
==============

------------------------------

From: "Art S. Kagel" <kagel AT bloomberg DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Newbie Question: Index lookup coord. checking...
Date: Fri, 1 Aug 1997 09:55:53 -0400
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On Mon, 28 Jul 1997, Badman wrote:

> Hello, I have a simple question: Can you check coordinates for an index
> lookup (so you don't get an error) and check that same index in the same
> if() statement?
>
> For example:
> if (x > 0 && x < 640 && y > 0 && y < 480 && *(screen+(y * 640)+x) > 3){
>
>    /* do stuff */
> };
>
> or....
>
>
> if (x > 0 && x < 640 && y > 0 && y < 480){
>   if (*(screen+(y * 640)+x)>3){
> };
> };
>
> which is better? Any help would be appreciated...

Both are good in the sense that both will work exactly the same way.
^^^^^^^^^^^^^^^^^^^^^^^^^^                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This isn't necessarily true.  I think that this is compiler /
system dependant.  It is a whole lot safer to break this comparison, and
like you said, makes it much easier to read.  Sometimes when using the
Borland
compiler, I got some strange results that seemed to point to the order that

comparisons in if statements actually followed didn't necessarily follow
the
order that I had coded them in.  Maybe it has something to do with
optimization?