[rrd-developers] rrdtool-1.3.99909060808 configure error

[Sebastian Harl]

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

-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 197 bytes
Desc: Digital signature
Url : http://lists.oetiker.ch/pipermail/rrd-developers/attachments/20090824/d4949f89/attachment.pgp