Re: !!, what is it?

"Kenneth Brody" <kenbrody@xxxxxxxxxxx> wrote in message
news:4324D57D.44516C35@xxxxxxxxxxxxxx
> Flash Gordon wrote:
> >
> > Cafer ÅzimÅYek wrote:
> [...]
> > > I think, C standarts says something about logical operations resusts;
> > > if the result is false, it's value is 0 (zero). if the result is true,
> > > it's value is non-zero (like -2, -1, 2, 3, ...). So, it must NOT be
> > > one. This difference has seen according to compiler or target
> > > platform.
> >
> > Incorrect. The result of any logical operator is *always* 0 or 1 and
> > this is defined by the standard. What probably has you confused is that
> > any non-zero value will act as true, so all the values you quote will
> > act as true. However, I repeat, the boolean operators will never return
> > any value other than 0 or 1 on *any* implementation.
> [...]
>
> Well, any C89 or later, I assume. I've worked on platforms (prior to
> 1989) where boolean expressions were 0 or -1.

You must have been programming in Basic!

No C implementation ever used -1 as the value of 0==0

One other explanation for this misunderstanding is that you may have been using
1 bit bitfields: it is implementation defined whether these have values 0 and 1
or 0 and -1. As far as I recall, C99 did not change that.

--
Chqrlie.


.

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