Re: lexical_cast again

From: d.frey_at_[hidden]
Date: 2000-12-04 12:42:55

--- In boost_at_[hidden], "Peter Dimov" <pdimov_at_m...> wrote:
> Try this:
> 
> template<std::size_t N> string lexical_cast_helper<string, char[N]>
> {
>     static std::string call(char const * s)
>     {
>         return s;
>     }
> };

Fantastic, thanks! I changed "string" to "class" in the first line and
it worked! Now, I think it's worth to resend the whole code. Kevlin,
you're reading this? I also added a specialization for T == S. Here it
is:

#include <iostream>
#include <string>

#include <strstream>
#include <typeinfo>

class bad_lexical_cast : public std::bad_cast
{
public:
   virtual const char* what() const throw()
   {
      return "bad_lexical_cast";
   }
};

template< typename T, typename S > class lexical_cast_helper
{
public:
   static T call( const S& arg )
   {
      std::strstream interpreter;
      T result;

      if(!(interpreter << arg) ||
         !(interpreter >> result) ||
         !(interpreter >> std::ws).eof())
      {
         throw bad_lexical_cast();
      }

      return result;
   }
};

template< typename T, typename S > T lexical_cast( const S& arg )
{
   return lexical_cast_helper< T, S >::call( arg );
}

template< typename U > class lexical_cast_helper< U, U >
{
public:
   static U call( const U& arg )
   {
      return arg;
   }
};

template< typename T, size_t N > class lexical_cast_helper< T, char[N]
>
{
public:
    static T call( const char* arg )
    {
       return lexical_cast< T >( std::string( arg ) );
    }
};

int main()
{
   try {
      
      std::cout << lexical_cast< std::string >( std::string("Hello,
world!") ) << endl;
      std::cout << lexical_cast< std::string >( "Hello, world!" ) <<
endl;
      
   }
   catch( std::exception& e ){
      cerr << e.what();
   }
   
   return 0;
}

Regards, Daniel