Re: [boost] is_nan

From: Howard Hinnant (hinnant_at_[hidden])
Date: 2006-07-25 09:26:21

On Jul 25, 2006, at 8:31 AM, John Maddock wrote:

> Johan Råde wrote:
>> So it would make sense to have the functions
>>
>>    is_finite()
>>    is_normal()
>>    is_subnormal()
>>
>>    is_infinity()
>>    is_plus_infinity()
>>    is_minus_infinity()
>>
>>    is_nan()
>
> Do we really want to use gratuitously different names from those in  
> C99:
>
> isfinite
> isnorm
> isinf
> isnan

If we use the C99 names, do we intend on #undef'ing the C99 macros if  
they exist (C99 says these are macros, not functions)?  If we don't  
then the macros will trash our functions.  There's an easy technique  
for converting the macro (if it exists) into a function (demonstrated  
by gcc's <cmath>).  If we do #undef the C99 macros, this is  
observable behavior which we should document (lest the client be  
testing #ifndef isnan after the boost header gets included).

I recommend restricting these templates to floating point types.   
Otherwise they are overly generic, and could easily be called  
accidently, especially isnormal, is_normal, isnorm (or whatever, C99  
and C++0X call it isnormal).

-Howard