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From: karl@haddock.UUCP (Karl Heuer)
Newsgroups: comp.lang.c
Subject: Re: Writing readable code
Message-ID: <658@haddock.UUCP>
Date: Tue, 30-Jun-87 16:00:57 EDT
Article-I.D.: haddock.658
Posted: Tue Jun 30 16:00:57 1987
Date-Received: Wed, 1-Jul-87 06:44:38 EDT
References: <1158@copper.TEK.COM> <6858@auspyr.UUCP> <17171@cca.CCA.COM> <22250@sun.uucp> <17193@cca.CCA.COM> <13008@topaz.rutgers.edu>
Reply-To: karl@haddock.ISC.COM (Karl Heuer)
Organization: Interactive Systems, Boston
Lines: 38

In article <13008@topaz.rutgers.edu> ron@topaz.rutgers.edu (Ron Natalie) writes:
>I have always wondered why people think NULL is more mnemonic than 0.
>When I read them as exactly the same (and fortunately in C, they are
>defined to be).

When used properly, NULL refers only to a null pointer constant.  Thus, I can
read "if (x == NULL)" and know without further context that x is a pointer.
(The constant 0 with an explicit (redundant) cast conveys even more
information; I use that notation too.)

>I also wonder about people who define TRUE to be any thing, since it leads to
>things like "if( bool == TRUE )" which is different than "if(!bool)"

There is that danger.  However, the reason *I* define TRUE (actually I prefer
YES, as in K&R) is for assignment ("flag=YES" instead of "flag=1"), not
comparison.  See above paragraph for reason.

>Generally, I use !p when I'm dealing with things that are supposed
>boolean values like "if(!isdigit(c))"

Good idea.  (Btw, note that some implementations of isdigit do not return 1
for success, so "if (isdigit(c) == TRUE)" is bad news.)

>MY PET PEEVES: ...
>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)
>    SCREW this, too difficult, how about writing the code to indicate
>    what is going on:
>	    fd = open("foo", 1);
>	    if(fd == -1)

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.

Karl W. Z. Heuer (ima!haddock!karl or karl@haddock.isc.com), The Walking Lint