[boost] Re: [type_traits] request for decayed<T>::type

From: Pavel Vozenilek (pavel_vozenilek_at_[hidden])
Date: 2005-01-01 10:40:42

"Thorsten Ottosen" wrote:

> The following trait is supposed to make it easier to forward
> arguments in generic code and in particular string literals. For example, 
> I
> will use it when I update boost.assign
> to use const T& arguments instead of T arguments. It could also be used to
> make a better version of std::make_pair():
>
>  template< class F, class S >
>    inline std::pair< typename decayed<F>::type,
>                      typename decayed<S>::type >
>    make_pair( const F& f, const S& s )
>    {
>        return std::pair< typename decayed<F>::type,
>                          typename decayed<S>::type >( f, s );
>    }
>
> Any thoughts from the type_traits authors?
> Do anybody mind if I add this to the cvs and make some docs for the
> type-traits library?
>
Attached is file which works on VC6 / Intel 7 / BCB6.4.
Only tiny changes were needed.

This boost::make_pair would be very useful.

Questions:

 - maybe other name than decayed could be found

 - isn't parameter passing suboptimal for e.g.
   boost::make_pair(0, 0)?

- following compiles:

struct ABC {
    explicit ABC(int) {}
};
std::pair<ABC, ABC> p5 = boost::make_pair(1, 2);
std::pair<ABC, ABC> p5 = std::make_pair(1, 2); // also compiles

Maybe the boost::make_pair could be coded
somehow to disable this behavior (ABC constructor
is explicit).

/Pavel

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`
end