[rrd-developers] rrdtool-1.3.99909060808 configure error

[Tobias Oetiker]

Today Sebastian Harl wrote:

> 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 ;-)

thank you
tobi

>
> Cheers,
> Sebastian
>
>

-- 
Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland
http://it.oetiker.ch tobi at oetiker.ch ++41 62 775 9902 / sb: -9900