Question

How can correctly use this ‘+=’ function if the function is declared within a namespace?

namespace WinFile
{
     std::stack <tstring> operator += ( std::stack <tstring>& s1, std::stack <tstring> s2 )
     {
        // Post:

     if ( s1 == s2 )
     {
       return s1;
     }

        while ( !s2.empty() )
        {
           s1.push( s2.top() );
           s2.pop();
        } 

        return s1;
   }
}

Now how do I use this function (without saying using namespace WinFile):

std::stack <tstring> s1;
std::stack <tstring> s2;
// ...after adding some values to the stacks
s1 += s2;                // this gets a compile error
s1 WinFile::+= s2        // this says its invalid to have a ':' infront of a +=

Answer 1

As already suggested you can use a “using” clause:

using WinFile::operator+=;

or

using namespace WinFile;

or you can use the function directly with the following code:

s1 = WinFile::operator +=( s1, s2 );

None of which are particularly ideal, but there are no other ways, to my knowledge, to do it.