Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!usc!brutus.cs.uiuc.edu!jarthur!aqdata!sullivan
From: sullivan@aqdata.uucp (Michael T. Sullivan)
Newsgroups: comp.lang.c
Subject: Re: Is this swap() macro correct?
Message-ID: <1990Jan18.002842.441@aqdata.uucp>
Date: 18 Jan 90 00:28:42 GMT
References: <21068@stealth.acf.nyu.edu>
Distribution: usa
Organization: aQdata, Inc.  Western Region -- San Dimas, CA
Lines: 15

From article <21068@stealth.acf.nyu.edu>, by brnstnd@stealth.acf.nyu.edu:
> Say swap() is defined as
> 
> #define block do {
> #define endblock } while(0)
> #define swap(x,y,typ) block typ *_MV_x = x; typ *_MV_y = y; typ tmp;\
>                     tmp = *_MV_x; *_MV_x = *_MV_y; *_MV_y = tmp; endblock

Why are "block" and "endblock" even bothered with here.  Why not just
put the "do {" and "} while (0)" in the definition of swap?  Could
somebody please enlighten me.
-- 
Michael Sullivan          uunet!jarthur!aqdata!sullivan
aQdata, Inc.              sullivan@aqdata.uucp
San Dimas, CA