[Haskell-cafe] Re: FFI to double constants, printf

[wren ng thornton]

Brandon S. Allbery KF8NH wrote:
> On Jul 17, 2009, at 22:27 , Maurí cio wrote:
>> Is there maybe some way to check if a double or
>> long double do have a "proper" value?
> 
> 
> isNaN :: a -> Bool
> True if the argument is an IEEE "not-a-number" (NaN) value
> 
> isInfinite :: a -> Bool
> True if the argument is an IEEE infinity or negative infinity
> 
> isDenormalized :: a -> Bool
> True if the argument is too small to be represented in normalized format
> 
> isNegativeZero :: a -> Bool
> True if the argument is an IEEE negative zero
> 
> isIEEE :: a -> Bool
> True if the argument is an IEEE floating point number
> 
> (in Prelude, even.  Class RealFloat)

But don't trust the Prelude in Hugs (Sept2006)! The isInfinite and isNaN 
methods are hard-coded to answer False, ignoring the argument entirely. 
The logfloat package has the module Hugs.RealFloat[1] which provides 
correct versions (defaulting to the Prelude definitions for non-Hugs 
compilers).


[1] 
http://hackage.haskell.org/packages/archive/logfloat/0.12.0.1/doc/html/Hugs-RealFloat.html

-- 
Live well,
~wren