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Path: utzoo!utgpu!water!watnot!watmath!clyde!rutgers!brl-adm!seismo!mimsy!chris
From: chris@mimsy.UUCP
Newsgroups: comp.lang.c
Subject: Re: Order of evaluation
Message-ID: <5956@mimsy.UUCP>
Date: Wed, 25-Mar-87 12:21:39 EST
Article-I.D.: mimsy.5956
Posted: Wed Mar 25 12:21:39 1987
Date-Received: Fri, 27-Mar-87 05:29:29 EST
References: <4775@brl-adm.ARPA> <7779@utzoo.UUCP> <521@cpocd2.UUCP> <739@xanth.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 69
Summary: A matter of taste

In article <739@xanth.UUCP> kent@xanth.UUCP (Kent Paul Dolan) writes:
>... but C was an ugly language to begin with, because so much of
>it doesn't parse the way it reads, due to _bizarre_ precedence results.

Aside from the results of chongo's contests, I find most C code
quite readable.  The trouble areas are unusual declarations and
`&' and `|' precedence:

	char *(*p[3])();
	...
	if (a & 1 == 0)		/* is not what you expected */

The solution to the latter, of course, is (dramatic music) to Put
In Many Many Parentheses.

>Adding the unary plus, which, to anyone taught mathematics,
>is a no-op, and making that the way to control the order of
>evaluation, just makes an ugly language uglier.

While it is a bit of a kludge, the fact that someone has written
an explicit no-op should give you a hint that something special is
going on.

>ANSI should have mandated respecting parentheses for evaluation
>order, so that code executes the way it reads.

I do not agree.

>This would break _no_ code,

True enough.

>and would let programmers' intuition be of some use ....

Whose intuition?  Certainly not mine.  I expect the compiler to
rip my parentheses to shreds.  I confess to having written some
floating point code in the past, aye, even in FORTRAN.  I used
multiple lines of statments to control evaluation order---even in
FORTRAN, and even before I knew any other language except BASIC.
(A humble start indeed!)

	#define input() \
		((env->c = getc(fin)) == '\n' ? \
		 (env->lineno++, env->c) : env->c)
	#define output(c) \
		(putc(c, env->fout), ferror(env->fout) ? ioerr() : 0)
	output(input())

produces

	((--(env->fout)->_cnt>=0?
	(int)(*(unsigned char*)(env->fout)->_ptr++=(((env->c=(--(fin)->_cnt>=0?
	(int)(*(unsigned char*)(fin)->_ptr++):_filbuf(fin)))=='\n'?
	(env->lineno++,env->c):env->c))):
	(((env->fout)->_flag&0200)&&-(env->fout)->_cnt<(env->fout)->_bufsiz?
	((*(env->fout)->_ptr=(((env->c=(--(fin)->_cnt>=0?
	(int)(*(unsigned char*)(fin)->_ptr++):_filbuf(fin)))=='\n'?
	(env->lineno++,env->c):env->c)))!='\n'?
	(int)(*(unsigned char*)(env->fout)->_ptr++):
	_flsbuf(*(unsigned char*)(env->fout)->_ptr,env->fout)):
	_flsbuf((unsigned char)(((env->c=(--(fin)->_cnt>=0?
	(int)(*(unsigned char*)(fin)->_ptr++):_filbuf(fin)))=='\n'?
	(env->lineno++,env->c):env->c)),env->fout))),
	(((env->fout)->_flag&040)!=0)?ioerr():0)

Ahh, lovely parentheses.  :-)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
UUCP:	seismo!mimsy!chris	ARPA/CSNet:	chris@mimsy.umd.edu