From: Bill Davidsen <davidsen@tmr.com>
To: liyu <liyu@ccoss.com.cn>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: A pettiness question.
Date: Wed, 21 Sep 2005 15:11:30 -0400 [thread overview]
Message-ID: <4331B062.10506@tmr.com> (raw)
In-Reply-To: <43311071.8070706@ccoss.com.cn>
liyu 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?
>
!!(N) is easier to write than ((N) ? 1 : 0)
--
-bill davidsen (davidsen@tmr.com)
"The secret to procrastination is to put things off until the
last possible moment - but no longer" -me
next prev parent reply other threads:[~2005-09-21 19:20 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-09-21 7:49 A pettiness question liyu
2005-09-21 8:00 ` Ustyugov Roman
2005-09-21 8:57 ` Eyal Lebedinsky
2005-09-21 9:01 ` Fawad Lateef
2005-09-21 9:30 ` Andrea Arcangeli
2005-09-23 2:36 ` Vadim Lobanov
2005-09-21 15:08 ` Randy.Dunlap
2005-09-21 19:11 ` Bill Davidsen [this message]
-- strict thread matches above, loose matches on Subject: below --
2005-09-21 19:46 Nick Warne
2005-09-21 20:05 ` Vadim Lobanov
2005-09-22 7:10 ` Helge Hafting
2005-09-22 12:21 ` Steven Rostedt
2005-09-22 14:40 ` linux-os (Dick Johnson)
2005-09-22 2:43 ` Fawad Lateef
[not found] <4PiLw-2yn-25@gated-at.bofh.it>
[not found] ` <4Pj4M-3as-1@gated-at.bofh.it>
[not found] ` <4PtnM-1oW-55@gated-at.bofh.it>
[not found] ` <4Pynh-fp-1@gated-at.bofh.it>
2005-09-25 14:38 ` Bodo Eggert
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