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From: aglew@ccvaxa.UUCP
Newsgroups: net.lang.c
Subject: Re: What should be added to C
Message-ID: <2600053@ccvaxa>
Date: Thu, 22-May-86 10:39:00 EDT
Article-I.D.: ccvaxa.2600053
Posted: Thu May 22 10:39:00 1986
Date-Received: Sun, 25-May-86 14:18:33 EDT
References: <1463@mmintl.UUCP>
Lines: 27
Nf-ID: #R:mmintl.UUCP:1463:ccvaxa:2600053:000:1161
Nf-From: ccvaxa.UUCP!aglew    May 22 09:39:00 1986


>/* Written  8:04 pm  May 16, 1986 by franka@mmintl.UUCP in ccvaxa:net.lang.c */
>/* ---------- "Re: What should be added to C" ---------- */
>Something which got forgotten in my original article: I would favor an
>exchange operator.  This one is quite frequently useful, and the
>alternatives are ugly.
>
>Frank Adams                           ihnp4!philabs!pwa-b!mmintl!franka
>Multimate International    52 Oakland Ave North    E. Hartford, CT 06108
>/* End of text from ccvaxa:net.lang.c */

Why not go all the way and implement Dijkstra's concurrent assignment?

    i,j := j,i

for a swap. Course, couldn't use commas, but you get the idea. 
Compilers can generate good code for this, and it makes programs with
complicated pointer manipulations much clearer; I used to teach it, and the
associated code generation algorithm, to U1s in classes I TAed, and it
greatly reduced the noise level of assignments in the wrong order.

#define swap(a,b)  a,b := b,a

does the exchange without having to type the name twice.

Andy "Krazy" Glew. Gould CSD-Urbana.    USEnet:  ihnp4!uiucdcs!ccvaxa!aglew
1101 E. University, Urbana, IL 61801    ARPAnet: aglew@gswd-vms