Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!amgraf!cpsolv!rhg
From: rhg@cpsolv.UUCP (Richard H. Gumpertz)
Newsgroups: comp.lang.c
Subject: Re: Obfuscated SWAP: not portable!
Message-ID: <149@cpsolv.UUCP>
Date: 1 Sep 89 08:43:30 GMT
References: <784@skye.ed.ac.uk> <1267@levels.sait.edu.au>
Reply-To: rhg@cpsolv.uucp (Richard H. Gumpertz)
Organization: Computer Problem Solving, Leawood, Kansas
Lines: 11

The exchange of x and y that has been under discussion:
    x ^= y ^= x ^= y
is non-portable because it depends on right-to-left evaluation which is NOT
specified in the C standard.  To be portable, use
    (x ^= y, x ^= y ^= x)    or    (y ^= x ^= y, x ^= y)
either of which forces the two assignments to x to be done in a well-defined
order.

		Richard H. Gumpertz

I am the company, so no disclaimer is needed! :-)