Hi, On Mon, Aug 24, 2009 at 08:46:17AM +0200, Tobias Oetiker wrote: > Friday Bernhard Reutner-Fischer wrote: > > # define isnan(a) (!!(fpclass(a) & (FP_SNAN|FP_QNAN))) […] > hi hi ... thanks ... what do the two ! do ? is this a binary not ?
That makes sure that 'true' is represented by 1 rather than some integer not equal to zero. The latter is interpreted as 'true' as well but boolean operators are expected to return 1. According to the Single Unix Specification this is not required for 'isnan' but it does not hurt either ;-) Cheers, Sebastian -- Sebastian "tokkee" Harl +++ GnuPG-ID: 0x8501C7FC +++ http://tokkee.org/ Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety. -- Benjamin Franklin
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