Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!usc!snorkelwacker.mit.edu!bloom-beacon!eru!hagbard!sunic!chalmers.se!mathrt0.math.chalmers.se!d9erikb
From: d9erikb@dtek.chalmers.se (Erik Bergersjo)
Newsgroups: comp.lang.c
Subject: Re: When do you use "if ( a = b )"? (was Re: Funny mistake)
Message-ID: <1991Mar21.213027.24314@mathrt0.math.chalmers.se>
Date: 21 Mar 91 21:30:27 GMT
References: <15481@smoke.brl.mil> <775@camco.Celestial.COM> <65837@eerie.acsu.Buffalo.EDU>
Sender: d9erikb@dtek.chalmers.se
Organization: Chalmers University of Technology, Gothenburg, Sweden.
Lines: 24


In article <65837@eerie.acsu.Buffalo.EDU> chu@acsu.buffalo.edu (john c chu)
writes:

>[concerning "if ( a = b )"
>
>Is there a good use for this?

There sure is. I can think of two major uses:

(I)	b is a function, perhaps returning a pointer to something
	on success and NULL otherwise.
(II)	b is a hardware register, cleared on reading.

Of course, in both cases "a = b; if( a )..." would do, but if you don't
have a good optimizing compiler the final code might get worse.
Besides, I think "if(a = b)" is more readable. It's clearly one of those
extra features / pecularities that make C the special language it is!

===============================================================================
Chalmers University |                         . .         | "A message worth
of Technology       | Real life: Erik Bergersj o          |  spreading is
Sweden              | E-mail:    d9erikb@dtek.chalmers.se |  worth reading"
===============================================================================