Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750731AbVIUHtP (ORCPT ); Wed, 21 Sep 2005 03:49:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750744AbVIUHtP (ORCPT ); Wed, 21 Sep 2005 03:49:15 -0400 Received: from [210.76.114.20] ([210.76.114.20]:15490 "EHLO ccoss.com.cn") by vger.kernel.org with ESMTP id S1750731AbVIUHtO (ORCPT ); Wed, 21 Sep 2005 03:49:14 -0400 Message-ID: <43311071.8070706@ccoss.com.cn> Date: Wed, 21 Sep 2005 15:49:05 +0800 From: liyu User-Agent: Mozilla Thunderbird 1.0.6 (X11/20050716) X-Accept-Language: zh-cn,zh MIME-Version: 1.0 To: LKML Subject: A pettiness question. Content-Type: text/plain; charset=gb18030; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 566 Lines: 23 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 - 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/