Re: [Boost-users] How to add a type to is_arithmetic

From: John Maddock (john_at_[hidden])
Date: 2007-10-13 04:49:30

Peng Yu wrote:
> Hi,
>
> Suppose I define a class fixed_point as
>
> class fixed_point{
> ....some operations are defined here
>
> private:
> int _integer_part;
> unsigned _fractional_part
> }
>
> I want is_arithmetic<fixed_point>::type to be true_

The aim of is_arithmetic is that it returns true only for built-in 
arithmetic types: in other words it's a type introspection tool.  If you 
specialise it for UDT's you will very likely break other code (for example 
has_trivial_XXX assumes that all arithmetic types have trivial 
construct/asign/copy/destroy operations).  Probably the correct traits to be 
specialising (and using to detect "numbers") is std::numeric_limits.

HTH, John.