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From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.lang.c
Subject: Re: Writing readable code
Message-ID: <22380@sun.uucp>
Date: Tue, 30-Jun-87 01:05:36 EDT
Article-I.D.: sun.22380
Posted: Tue Jun 30 01:05:36 1987
Date-Received: Sat, 4-Jul-87 18:51:14 EDT
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Lines: 44
Keywords: have my cake and eat it too

> >2.  Needless use of the comma operator and parenthesis to demonstrate
> >    manhood to the obliteration of code readability, e.g.
> >	    if((fd=open("foo",1)<0)
> >
> 
> Once again to save instructions. The function return value is usually 
> already in d0, and it needs only check it's status bits for negative, 
> etc.. as opposed to loading -1 into another register, then comparing
> the two register values.

The "< 0" vs. "== -1" may make a difference in the generated code, but if the

	if ((fd = open("foo", 1)) < 0)

vs.

	fd = open("foo", 1);
	if (fd < 0)

makes a difference, you don't have a good compiler.  Our compiler
gives the exact same code for

	if ((fd = open("foo", 1)) < 0)
		die();

and

	fd = open("foo", 1);
	if (fd < 0)
		die();

namely, something similar to:

	pea	1
	pea	"foo"
	jbsr	_open
	addqw	#8,sp
	movl	d0,fd
	jge	1f
	jbsr	_die
1:
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com