Re: Problem with +numberWithBool: ?

[Pascal J . Bourguignon]

Richard Frith-Macdonald writes:
> 
> 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'
> 
> I'm sure I've seen arguments about this before -  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.
> 
> In practice, it matters little as long as you are consistent ... and
> are careful in cases where you interface to unknown code.  Sometimes
> a problem with  categories.  Nevertheless, I'd consider it very poor
> programming to return anything  other than YES or NO from a method
> declared to return BOOL.

It's a C (or Objective-C) question: does a==b (or a<b, etc) return 0/1
or 0/possibly anything else than 0 ?

On 680x0 processors, the instructions that build boolean values give 0
and 0xff  ((char)(-1)). All C  compilers I've see on  these processors
always take care to mask it off to 0/1. 

I  don't have  my ANSI-C  references at  hand, but  if it's  said that
boolean producing  operators always  return 0 or  1, then there  is no
problem,  returning a  boolean expression  will  return a  BOOL (or  a
bool).


In  any  case,  that's  one  more  reason why  it's  better  to  write
if(condition) rather than if(condition==YES).

-- 
__Pascal_Bourguignon__                     http://www.informatimago.com/
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