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From: ddl@husc6.UUCP (Dan Lanciani)
Newsgroups: comp.lang.c
Subject: Re: Writing readable code
Message-ID: <2430@husc6.UUCP>
Date: Tue, 30-Jun-87 20:30:34 EDT
Article-I.D.: husc6.2430
Posted: Tue Jun 30 20:30:34 1987
Date-Received: Wed, 1-Jul-87 07:21:57 EDT
References: <1158@copper.TEK.COM> <6858@auspyr.UUCP> <17171@cca.CCA.COM> <1176@copper.TEK.COM>
Organization: Harvard University Computer Services
Lines: 78

In article <1176@copper.TEK.COM>, stevesu@copper.TEK.COM (Steve Summit) writes:
| It has been pointed out that my original posting had a blatant
| error in it: (!p) and (p != NULL) are not at all equivalent, but
| in fact are exactly opposite.  I was at first acutely embarrassed,
| but I am now flatly amazed that the statements have been argued
| so hotly, by some of the best minds on the network, without
| noting this crucial fact.

	I sincerely doubt that the "best minds on the network" are the
ones doing the arguing.  Nevertheless, I noted this "crucial fact"
and hence my question as to whether you had really mastered the idiom.
I guess I was too subtle and you missed the point.

| The fact that this error is so easy to make (I spent several
| hours on the original posting, and I read through it countless
| times, and I still missed it) ends up illustrating the point very
| well: when coding, say what you mean.

	I really hope you mean the fact that this error is so easy
for YOU to make illustrates the point that YOU need to be very
careful when coding.  The error was immediately obvious to me and
to the only other person I mentioned it to.  When I code "if(!p)"
I say exactly what I mean and I mean what I say.  Your reasoning
is about as good as my saying, "Since I can't fly an airplane, it
is clearly impossible to do so."

| Since I started this, I might as well make my thinking process
| clear: we have a pointer variable, and it either holds or does
| not hold a single "out of band" nil value.  The closest
| transliterations of those English statements into C are
| 
| 	if(p == NULL)
| and
| 	if(p != NULL)
| 
| (assuming a proper #definition of NULL).

	I would claim that the closest transliterations are "if(!p)"
and "if(p)," if only because they DON'T assume a proper #define of
ANYTHING.

| In my opinion, the most important thing is to keep that
| transliteration step simple.

	Again, C has made that step very simple for you by providing the
"if(p)" construct.  Of course, this is my opinion.

| Everything else (compilation time,
| efficiency, source code character count) is secondary.

	Other than the fact that I happen to find less cluttered code
easier to read, the issue of character count is a joke.  Compilation
time is a programmer resource and can often be adjusted...  But efficiency
is not always a secondary issue.  In fact, it is RARELY a secondary issue.
Sometimes efficiency makes the difference between an application's working
or failing.  More often however, this attitude encourages the production
of needlessly slow programs with which users must suffer for years.

| The
| biggest problem in Software Engineering is not code size or
| efficiency but correctness: a program is supposed to do what you
| want it to do, but rarely does.  The more I can make my C code
| "read" like an English description of what the code is supposed to
| do, the fewer transliteration errors I will make, and the easier
| my code will be for me, and others, to read.

	Maybe you should try COBOL.  It was designed to read like an
English description.  C was not.  Why not let C read like a C description
of the problem?  When I program in C I do not transliterate from English
because I find C to provide a better mechanism for describing many
problems.  This is my personal style.  You have your own style.  I have
no trouble reading code written in either style.  Can't we leave it at
that rather than trying to prove that one style somehow encourages
correctness and another style tends to discourage it?


					Dan Lanciani
					ddl@harvard.*