Messages in this thread | | | Date | Wed, 21 Sep 2005 14:01:11 +0500 | From | Fawad Lateef <> | Subject | Re: A pettiness question. |
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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/
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