id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
2128,Add the ability to implicitly traverse reference wrappers,mgoldshteyn@…,Peter Dimov,"Please add the following to boost:

namespace boost
{

template<class T> T* get_pointer( reference_wrapper<T> const & r )
{
    return r.get_pointer();
}

}

----

Code demonstrating the issue:

#include <boost/bind.hpp>
#include <boost/ref.hpp>
#include <string>

// Define a simple class for our example class Crayon {
public:
  explicit Crayon(const std::string &color=std::string()):m_color(color) {}
  const std::string &GetColor() const {return m_color;}

private:
  std::string m_color;
};

int main(int argc, char *argv[])
{
  using namespace std;
  using namespace boost;

  Crayon cr(""blue"");
  boost::reference_wrapper<const Crayon> crefCr(cr);

  // This doesn't compile, however, even though the reference_wrapper class template has
  // an overloaded operator T& () const function
  std::string colorFromConstRef2(boost::bind(&Crayon::GetColor,_1)(crefCr));
}

----

Peter Dimov's reply:

It doesn't because of the mem_fn behavior that bind inherits. The argument 
is not a reference to Crayon and so is assumed to be a smart pointer to 
Crayon. mem_fn then tries to invoke get_pointer() on it to obtain a Crayon*. 
You should be able to make it compile by adding a get_pointer overload for 
reference_wrapper:

namespace boost
{

template<class T> T* get_pointer( reference_wrapper<T> const & r )
{
    return r.get_pointer();
}

}
",Feature Requests,closed,Boost 1.39.0,bind,Boost 1.35.0,Problem,fixed,implicitly traverse reference_wrappers,