lkml.org 
[lkml]   [2005]   [Sep]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: A pettiness question.
On 9/21/05, Ustyugov Roman <dr_unique@ymg.ru> 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 majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-09-21 11:03    [W:1.927 / U:0.156 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site