Re: [boost] Math constants for naive and gurus? - which constants do you want?

From: Ed Brey (edbrey_at_[hidden])
Date: 2001-10-24 13:24:03

From: "Greg Colvin" <gcolvin_at_[hidden]>
> 
> However, I'm still not sure why we need the various namespaces.  Why not
> just:
> 
>   template< typename Tag >
>   struct constant {
>      constant() {}
>      operator float() const; // fully specialized for each Tag
>      operator double() const; // fully specialized for each Tag
>   };
> 
>   struct pi_tag {};
>   template<> inline constant< pi_tag >::operator float() const {
>     return 3.14159265358979323846F;
>   }
>   template<> inline constant< pi_tag >::operator double() const {
>     return 3.141592653589793238462643383279502884197;
>   }

It would certainly be nice to find a better alternative to the namespaces.  I like the thought behind the overloading suggestion.  However, it can lead to too much ambiguity, e.g.:

double floor(double);
float floor(float);

double three = floor(pi);
double two_pi_from_int = pi * 2;
double two_pi_from_double = pi * 2.0;

According to my compiler, all three statements result in ambiguity.