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Path: utzoo!mnetor!seismo!rutgers!topaz.rutgers.edu!ron
From: ron@topaz.rutgers.edu (Ron Natalie)
Newsgroups: comp.lang.c
Subject: Re: Writing readable code
Message-ID: <13112@topaz.rutgers.edu>
Date: Thu, 2-Jul-87 13:25:54 EDT
Article-I.D.: topaz.13112
Posted: Thu Jul  2 13:25:54 1987
Date-Received: Sat, 4-Jul-87 06:35:29 EDT
References: <1158@copper.TEK.COM> <6858@auspyr.UUCP>
Organization: Rutgers Univ., New Brunswick, N.J.
Lines: 25


> The main advantage of this idiom is for "while" statements.  The usual
> example is "while ((c = getchar()) != EOF) ...", which cannot be
> written cleanly without the embedded assignment.  The use in "if"
> statements often permits one to collapse nested ifs, which can
> *improve* code readability.

If "c" is of type "char" this is still not written cleanly.  EOF is
type int.  The assignment into a character causes getchar's int return
to be changed to char, invalidating the following comparison.  The
effect is that characters of value 0xFF will cause erroneous end of
file indication.  This is a common error in C, but it is fortunate
that most text this is used on never contains any characters with the
most significant bit set.

To do this right you need an extra int temporary value

	while ((i = getchar()) != EOF)
	    or
	while( i = getchar(), i != EOF)

followed by
	    c = i;

-Ron