Path: utzoo!utgpu!water!watmath!clyde!rutgers!rochester!udel!burdvax!sdcrdcf!ism780c!news
From: news@ism780c.UUCP (News system)
Newsgroups: comp.lang.c
Subject: Re: == vs =
Message-ID: <8836@ism780c.UUCP>
Date: 2 Feb 88 21:12:16 GMT
References: <11523@brl-adm.ARPA> <1202@eneevax.UUCP>
Reply-To: marv@ism780.UUCP (Marvin Rubenstein)
Organization: Interactive Systems Corp., Santa Monica CA
Lines: 36

In article <1202@eneevax.UUCP> noise@eneevax.umd.edu.UUCP (Johnson Noise) writes:
>	No.  I don't understand what the big problem is about = and ==.
>I made that mistake once and only once (it took 15 mins. to find it, but
>I never did it again) when I was still learning the language.  If I can
>remember what to use when, I should think most people can.


I decided to find out about the = and == problem by looking at an actual
program written in C.  I counted the number of assignment and equality
operations that appeared in the source text of an experimental compiler that
I have working on.  Below are the statistics:

    1455 assigns
     422 equality compares
  197498 total source characters.

Now, if assign required two characters and compare required one, the compiler
would have 1033 more characters in its source representation.  I am a very
slow typist (80 chars/min).  Even so, having a two character symbol for
assignment operator would have added only about 13 minutes to the total
development effort for the compiler.

On the other hand, I once received a bug report that was eventually traced to
a single = appearing in in a comparison.  The program in error was a C
compiler!  This error caused the compiler to generate a bad code sequence for
certain obscure cases (one of the cases appeared in the FORTRAN compiler that
was written in C).  I leave it to you to guess the cost finding the bug,
correcting the C compiler, recompiling every program in the system that had
been developed with the compiler, and distributing a corrected system.

My conclusion: if = had been chosen for the equality operator and any two
character symbol (e.g. ::) had been chosen for the assignment operator, the
cost of developing a program in C would be less even though the character
count in a program might be 0.5% greater.

     Marv Rubinstein -- Interactive Systems