Re: [boost] [type_erasure] Review started (July 18-27, 2012)

Subject: Re: [boost] [type_erasure] Review started (July 18-27, 2012)
From: Paul A. Bristow (pbristow_at_[hidden])
Date: 2012-08-10 10:20:05

> -----Original Message-----
> From: boost-bounces_at_[hidden] [mailto:boost-bounces_at_[hidden]] On Behalf Of Steven
> Watanabe
> Sent: Wednesday, August 08, 2012 3:29 PM
> To: boost_at_[hidden]
> Subject: Re: [boost] [type_erasure] Review started (July 18-27, 2012)
> 
> AMDG

namespace boost {
namespace type_erasure {

template <typename T1, typename T2>
std::ostream& operator<< (std::ostream& os, const std::pair<T1, T2>& p)
{ /*! Output a pair of values with space as delimiter.
     \details For example: "1.23 3.45".
   */
  os << p.first <<  " "  << p.second;
  return os;
} // std::ostream& operator<< (std::ostream& os, const std::pair<T1, T2>& p)

// Partial specialization of struct ostreamable for pair<T1, T2>:
template<class Os, typename T1, typename T2>
struct ostreamable<Os, std::pair<T1, T2> >
{
    static void apply(Os& out, const std::pair<T1, T2>& arg)
    {
      out << arg; 
   }
};
} // namespace type_erasure
} // namespace boost

Works nicely for anything needing std::pair like map.

Followers of this thread may also be amused to see my fumblings with type_erasure (attached) 

adding a few more bells and whistles and

using with lots of types of things (including User defined types) in various containers.

I can see lots of neat applications just printing things in containers.

Paul

PS I note in fiddling with cosmetic details that boost::tuple only provides a char option for 

std::cout << set_open('[')    << set_delimiter('_')    << set_close(']')    << std::endl;

this prevents, for example ",  " (comma and space) as a delimiter.

Can anyone remember a good reason why a std::string is not also provided?