From: "Campbell, Rolf [SKY:1U32:EXCH]" <moscoop AT americasm01 DOT nt DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: odd or even?
Date: Thu, 02 Mar 2000 09:45:01 -0500
Organization: Nortel Networks
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To: djgpp AT delorie DOT com
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Chris Mears wrote:

> That Trancelucid <trancelucid AT videotron DOT ca> really knows where his
> towel is.  On Thu, 02 Mar 2000 06:07:49 -0500, he wrote:
>
> >DAVID JACOBS wrote:
> >>
> >> What is the fastest way to check wether an int/long is odd or even?
> >> I've checked my C/C++ manual, but I didn't find anything....
> >
> >Just mask the bit 0..
> >
> >if(i & 0x01) {
> >   printf("odd");
> >}
> >else {
> >   printf("even");
> >}
>
> I don't know how well this will work with signed integers.

It should work fine with signed integers....
-1 = 0xFFFFFFFF (lowest bit set)
-2 = 0xFFFFFFFE (lowest bit not set)

>  I believe
> the fastest[*] way is:
>
> #define EVEN(x) (((x) % 2) == 0)
> #define ODD(x) (((x) % 2) != 0)

A literal "%" requires a divide (which is slow).  I suspect that with
optimizations on it would be reduced to (x&1) anyways.

--
(\/) Rolf Campbell (\/)