NULL as a string terminator

[Isaac Rabinovitch]

In <1990Aug20.073554.9537 at zoo.toronto.edu> henry at zoo.toronto.edu (Henry Spencer) writes:

>>>In many cases the object itself becomes familiar enough that it's
>>>instantly recognized.  '\0' is one such object.  If I saw in your
>>>code
>>>
>>>	*p = EOS;
>>>
>>>I'd have to run off to your .h files to find the definition of EOS.
>>
>>  Perhaps a comment in an appropriate place might alleviate this.

>Comments are not a substitute for using familiar practices instead of
>unfamiliar ones.  Familiar ones should be preferred unless there is
>a *substantial* advantage to be had.  I don't see one here.

I agree with you in principle, and also in this instance (does anyone
seriously intend to put a comment at every end-of-string comparison?).
The problem is with the concept of "familiar".  This business of
strings always terminating with a null is fundamental to C programming
-- if you don't know that '\0' means "end-of-string" then you simply
don't know how C strings work at all!  (Note that nobody ever uses
an (int) 0 in place of '\0', even though the two are equivalent!)

On the other hand, you can say (and I used to) that using 1 and
0 instead of TRUE and FALSE is a similar "familiar practice", since any
competant C programmer knows that C booleans are just integers.  
In this case it probably makes a big difference that TRUE and FALSE are
ordinary English words, not obscure acronyms.

I recently came up against a similar clash of "familiar concepts" in
C.  People were arguing (was it in this group?) over why programmers
use "i" instead of "i == 0".  I asserted that this shorter expression
usually generated tighter code, at least on stupider compilers.  I
think I might have been right about this 10 years ago, but even if I
was I'd only shown I was out of date in the current state of compiler
writing.  I got one private message from a guy at a certain Big
Software Company who told me that reducing such comparisons was the
first optimization any compiler writer implemented.  True enough, but
what I found especially interesting was all the public and private
flames fired at me by folks who insisted not just that I was wrong
(which, of course, I was) but that the C language was *defined* to
include such a reduction!
-- 

ergo at netcom.uucp			Isaac Rabinovitch
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