Re: [boost] Re: Optimising assignment using std::swap

From: Jens Maurer (Jens.Maurer_at_[hidden])
Date: 2001-01-24 18:06:50

Stephen Silver wrote:
> The std::swap I have for my GMP mpz_t wrapper is like this:
> 
> namespace std
> {
>     template <>
>     void swap(::Integer& a, ::Integer& b)
>     {
>         ::mpz_swap(a.mpz, b.mpz);
>     }
> }
> 
> This is a specialization, not an overload, and is legal.

This is fine for classes such as the one you describe.  However,
this covers only a small part of the problem, because most
entities in boost are class templates, e.g. rational<T>.
This would require something like

namespace std
{
    template <class T>
    void swap(boost::rational<T>& a, boost::rational<T>& b)
    {
        a.swap(b);
    }
}

which is an overload and not a specialization, partly because
there is no such thing as a partial specialization of
function templates in C++.

And function overloads in namespace std are forbidden, just to
re-iterate once more.

Jens Maurer