On 01/17/2013 04:46 PM, Vincent Lefevre wrote:
On 2013-01-17 16:33:56 +0100, Mischa Baars wrote:
Actually it is the correct way, as long as you stick to the
conventions. A QNaN is not supposed to change into anything, also
not with the pow(). Only the other way around. Normal numbers can
change into QNaN's.
The C standard specified pow(NaN,0) = 1, pow(1,NaN) = 1, and
hypot(inf,NaN) = +inf. You may consider that these are bad choices
(I don't like them much either), but this is how these cases have
been specified. You are free to write wrappers for your own programs
and never call pow and hypot directly...
Again, personally I think that might just be not the smartest choice.
QNaN are only useful when normal numbers can be changed into QNaN's but
not the other way around. Then you can see at the end of any calculation
if something went wrong or if it gave you the answer you had expected.
