weird compiler error using bind2nd(): “member function already defined or declared” instead of “reference to reference”

Question

I recently spent quite some time understanding the error message when calling func() in this piece of code:

int main()
{
    vector< vector&l         


        

Answer 1

This behavior is well-defined (every correct C++ compiler will fail to compile your code).

From the standard (N3376) section D.9.3 on class template binder2nd, these two defintions of operator() exist:

typename Fn::result_type
operator()(const typename Fn::first_argument_type& x) const;

typename Fn::result_type
operator()(typename Fn::first_argument_type& x) const;

If first_argument_type is already a const T&, then they will be conflicting.