Re: Problem with +numberWithBool: ?

[Alexander Malmberg]

Richard Frith-Macdonald wrote:
> On 30 Jan 2004, at 11:26, Helge Hess wrote:
> > On Jan 29, 2004, at 2:12 PM, Richard Frith-Macdonald wrote:
> >> Booleans in objc can be YES or NO ... this is not the same thing as
> >> true/false in C/ObjC conditionals where 0 is false and anything
> >> non-zero is true.
> >
> > Such an assumption (which is probably not backed by the ObjC "spec")
> 
> I have noticed that when you say 'probably' you seem to mean 'I haven't
> checked'  :-)
> 
> Page 178 of the NeXTstep reference, section headed Defined Types ...
> 
> 'BOOL   A boolean value, either YES or NO'

But this isn't a spec, and it tells. That statement is way too vague to
be useful when implementing things. Anyway, the intent here is
irrelevant. objc/objc.h has:

typedef unsigned char  BOOL;

and, in practice, that's what matters.

> I'm sure I've seen arguments about this before

Do you have a link to this prior discussion (if it was public)?

> -  I judged the
> consensus to be that the
> BOOL type is intended to be boolean, and the fact that it's stored as a
> char is an
> implementation detail.

It isn't an implementation detail since it means that BOOL isn't a true
boolean type. Compare this with c99's _Bool, which is a true boolean
type:

#include <objc/Object.h>
int main(int argc,char **argv)
{
        int i=5;
        BOOL objc_bool;
        _Bool c99_bool;

        objc_bool=i;
        c99_bool=i;
        printf("objc_bool=%i  c99_bool=%i\n",objc_bool,c99_bool);
        return 0;
}

This will print:

objc_bool=5  c99_bool=1

- Alexander Malmberg