C Style

[Barry Margolin]

In article <3583 at haddock.ISC.COM> karl at haddock.ima.isc.com (Karl Heuer) writes:
>>There are times when a var can very intentionally have a non-zero (true)
>>value other than TRUE (1).  The classic kind of case of this is [isalpha].
>
>Then isalpha() is not a boolean, in my book.  I'm not convinced there's any
>good reason for this; it would be trivial to rewrite the function to return a
>true boolean.  In most instances this would have zero run-time cost.

Well, if you're coding in C, you'll have to live with C's quirks.
Nowhere does the C language specify that any particular non-zero value
should be returned by the isXXX functions to indicate truth.  The
person who wrote isalpha() might have done #define TRUE 2, and you
might have done #define TRUE 1.  Who is to say that you are right and
he is wrong?  The only thing that C specifies is that you must both do
#define FALSE 0.  Remember, C doesn't have real booleans, and #define
TRUE 1 isn't going to change that fact.

I can think of one reason, however, why 1 should be used as a standard
truth value.  Single-bit fields in structures are generally used as
flags, and it would be nice to be able to say flag = isXXX(...) rather
than flag = (isXXX(...) != FALSE).  But this is just a wish; portable
code must currently use the more verbose version.

Barry Margolin
Thinking Machines Corp.

barmar at think.com
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