Re: [Boost-users] Re: B is_convertible to A<T> for some T

From: Aleksey Gurtovoy (agurtovoy_at_[hidden])
Date: 2005-01-12 01:45:42

Tom Widmer writes:
> Aleksey Gurtovoy wrote:
>
>  > Agoston Bejo writes:
>  >
>  >> Hello,
>  >>
>  >> how do I express through template metaprogramming or in a similar
>  >> way that a class is convertible to a template class for some T1?
>  >> I.e., the condition: "There exists some T1 such that B is
>  >> convertible to A<T1>".
>  >
>  >
>  >
>  > Use overload resolution. The easiest way would probably be to take
>  > 'is_convertible' implementation for your compiler and replace the
>  > overload used to detect 'To' type convertibility with with a function
>  > temlate accepting 'A<T1>'.
>
>
> But template argument deduction will fail, won't it, since user defined 
> conversions aren't considered when deducing template arguments? 

Yes, it will.

> Obviously, if the class is derived from A<T1> for some T1, then it 
> should work, since the derived-to-base conversion is considered.

This was the case with the OP code, and what I was thinking of when I
wrote the above.

Thanks for the correction,
-- 
Aleksey Gurtovoy
MetaCommunications Engineering