On 9/21/05, Ustyugov Roman <[email protected]> wrote:
> > Hi, All.
> >
> > I found there are use double operator ! continuously sometimes in
> > kernel.
> > e.g:
> >
> > static inline int is_page_cache_freeable(struct page *page)
> > {
> > return page_count(page) - !!PagePrivate(page) == 2;
> > }
> >
> > Who would like tell me why write like above?
>
> For example,
>
> int test = 5;
> !test will be 0, !!test will be 1.
>
> This give a enum of {0,1}. If test is not 0, !!test will give 1, otherwise 0.
>
> Am I right?
Yes, but what abt the above case/example ??? PagePrivate is defined as
test_bit and test_bit will return 0 or 1 only ...... So y there is (
!! ) ??
--
Fawad Lateef
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
| |
 |