Re: [Boost-users] [Test] Template specialization problems with BOOST_CHECK_EQUAL_COLLECTIONS

From: Vladimir Prus (ghost_at_[hidden])
Date: 2005-09-01 03:24:53

Will Bryant wrote:

> I get a compiler error along the lines of
> "h:\libraries\boost\boost\test\utils\wrap_stringstream.hpp(66) : error
> C2679: binary '<<' : no operator found which takes a right-hand operand
> of type 'const std::basic_string<_Elem,_Traits,_Ax>' (or there is no
> acceptable conversion)" (with _Elem being wchar_t in this case, and
> _Traits and _Ax having the usual defaults).
......
>     template <typename CharT, typename T>
>     inline basic_wrap_stringstream<CharT>&
>     operator<<( basic_wrap_stringstream<CharT>& targ, T const& t )
>     {
>         targ.stream() << t;
>         return targ;
>     }
........
> 
> Since that backing ostringstream descends from ostream, I would have
> thought that all I needed to do was to ensure that there is a operator
> << (ostream&, wstring const&) defined, like this:
> 
>     ostream& operator << (ostream& ostr, wstring const& str)
>     {
>         ostr << "I'd put a wstring-to-string function here instead of
> this constant";
>         return ostr;
>     }

I think you need to define this in "namespace std". The 

        targ.stream() << t;

code is inside operator<< in namespace boost. That operator hides all global
operators<< you might have. The only way your operator for wstring can be
found is via ADL, so you need to put it in namespace std.

- Volodya