Re: [boost] [intrusive] Comments on interface changes and stateful value_traits (long)

From: Steven Watanabe (steven_at_[hidden])
Date: 2007-08-25 12:00:28

AMDG

Ion Gaztañaga <igaztanaga <at> gmail.com> writes:

> before
> 
> class my_value_traits
> {
>     node_ptr to_node_ptr(value_type &val)
>     //...
> };
> 
> after
> 
> class my_value_traits
> {
>     template<class Container>
>     node_ptr to_node_ptr(value_type &val, const Container& cont)
>     //...
> };
> 
> So if there is any metaprogramming hack (if increases compilation time 
> too much, forget it  ) I would like to receive suggestions. 
> 

typedef char no;
struct yes { no dummy[2]; };

template<class T>
yes convert_result(const T&);

no convert_result(const no&);

template<class T>
T make();

template<class Base>
struct has_plain_to_node_ptr_impl : Base {
    no to_node_ptr(...);
    using Base::to_node_ptr;
};

template<class T>
struct has_plain_to_node_ptr {
    enum { value =
        (sizeof(convert_result(
            has_plain_to_node_ptr_impl<T>::to_node_ptr(
                make<const value_type&>()
         ))) == 
         sizeof(yes))};
};

In Christ,
Steven Watanabe