Path: utzoo!utgpu!water!watmath!clyde!rutgers!husc6!hao!oddjob!gargoyle!ihnp4!ihlpg!tainter
From: tainter@ihlpg.ATT.COM (Tainter)
Newsgroups: comp.lang.c
Subject: Re: swap via xor
Message-ID: <4721@ihlpg.ATT.COM>
Date: 29 Jan 88 16:48:00 GMT
References: <8801200422.AA19420@decwrl.dec.com> <3061@killer.UUCP> <10366@mimsy.UUCP>
Organization: AT&T Bell Laboratories - Naperville, Illinois
Lines: 23

In article <10366@mimsy.UUCP>, chris@mimsy.UUCP (Chris Torek) writes:
> Let me see if I can lay this to rest.

If you hadn't said this I probably would have let it go. :-)

> 	a ^= b; b ^= a; a ^= b;
> will swap `a' and `b' if the `^' operator can be applied at all.
> There is no way within C (short of `#define a b' or equivalent) to
> make this fail.

Actually if a or be are expressions with side effects you have a problem.
i.e.

	given
	char *a, *b; 

	swap(a++,b++);

	defined as above goes splooot.

> In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)

--j.a.tainter