Re: Lives there a boolean integer?

["Sandy Harris" <sharris -at- dkl -dot- com>]

"Mark L. Levinson" wrote:
> 
> I'd like to hear from people who are familiar with
> C and with Perl.

I know C well, but don't use Perl.

> I'm documenting a number of functions
> that return the integer 1 to indicate success and the
> integer 0 to indicate failure.  Because these are the
> only two values ever returned, I'm being encouraged
> to refer to them as boolean values, and I'm
> being told that there's no real confusion involved
> because neither C nor Perl supports a true boolean
> data type.

C doesn't, not in the sense that Pascal or other more strongly
typed languages do.
 
> Should I stand on the principle that an integer
> is not boolean?

I'd use the term Boolean, but be quite careful with it.

If your function returns are being used in C flow control contexts:

	if( myfunction() )
               ....
        else
               ....
or
	while( myfunction() )
or
	for( i = 0 ; myfunction() ; i++ )

Then zero is treated as false and /any non-0 value/ is true. You can
combine these with Boolean operators, ! for not, && for AND, || for OR.
eg. with:

	if( functionA() || functionB() )
		x = 1 ;
	else
		x = 2 ;

x is set to one if either function returns non-zero.
(And functionB() isn't even called if A returns non-zero, but that's
off-topic.)

That's one type of Boolean operator in C, but there's another and it
is very different.

C also has bitwise Boolean operations: ^, &, | and ~ for XOR, AND, OR
and NOT respectively, which operate on individual bits of an integer's
binary represenation. so, with four-bit integers, if:

	a = 1001
	b = 1100
then
	~a  = 0110
	~b  = 0011
	a&b = 1000
	a|b = 1101
	a^b = 0101

As long as you carefully avoid confusing the two classes of Boolean
operations (use the word "bitwise" whenever you talk about the 2nd!),
you should be fine.