Re: Re: Conversion policies

At 14:51 2003-08-05, David Abrahams wrote:
>Daniel Wallin <[email protected]> writes:
>
> > I've checked in a basic framework for conversion policies, like the
> > one we have in luabind.
> >
> >    boost/langbinding/policy.hpp
>
>Q1: Why use a handbuilt cons-list in lieu of mpl::list?

Because I want to overload operator+ to compose the list. Also I want to
be able to have data in the policies.

>Q2: Conversion policies may carry data in them; it seems to me that
>     you need a runtime identification mechanism.  How about CRTP?

Elaborate, where does CRTP apply here?

>     What is the purpose of the "N" argument in find_conversion_policy
>     anyway?  I guess some comments would be illustrative.

It's the parameter index. The idea is that the caller does something like:

typedef typename find_conversion_policy<1, Policies>::type policy1;
typename polic1::template generate_converter<T1, xxx_to_cpp>::type c1;

>     P.S. Metafunctions should take only type parameters, for a variety
>     of reasons, and converter_generator_tag would be more
>     interoperable if its nested type were called "::type" instead of
>     "::index"

Ok.

---
Daniel Wallin



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