Re: A pettiness question.

[Ustyugov Roman <dr_unique@ymg.ru>]

> 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?
>
>
>     Thanks in advanced.
>
>
> Liyu

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?
-- 
RomanU