template <class T>
struct add_reference
{
   typedef see-below type;
};

type: If T is not a reference type then T&, otherwise T.

C++ Standard Reference: 8.3.2.

Compiler Compatibility: If the compiler does not support partial specialization of class-templates then this template will compile, but the member type will always be the same as type T except where compiler workarounds have been applied.

Header: #include <boost/type_traits/add_reference.hpp> or #include <boost/type_traits.hpp>