Re: special floats generate incorrect C code when used as compile-time constants

Hi,

Greg Ewing wrote:
> Stefan Behnel wrote:
>> As of 2.6, float('inf') and float('nan') will be guaranteed to work
> 
> Does it also provide a way of testing whether a value
> is an inf or nan?
> 
> I tried this on MacOSX using 2.3:
> 
>>>> x = float('nan')
>>>> y = float('nan')
>>>> x == y
> True
> 
> But isn't that wrong? Aren't nans supposed to compare
> unequal to anything else, including themselves? What
> does 2.6 do here?

That looks platform specific to me. At least in 2.5, I don't get that:

  Python 2.5.1 (r251:54863, Mar  7 2008, 04:10:12)
  [GCC 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)] on linux2
  Type "help", "copyright", "credits" or "license" for more information.
  >>> a = float('nan')
  >>> b = float('nan')
  >>> a == b
  False

Same for the C code in Cython. That's why the test case doesn't check it:

http://hg.cython.org/cython-devel/file/02e2efe1bce5/tests/run/specialfloat.pyx

Stefan