...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
boost::forward
// In header: <boost/move/utility_core.hpp> template<typename T> output_reference forward(input_reference);
This function provides limited form of forwarding that is usually enough for in-place construction and avoids the exponential overloading for achieve the limited forwarding in C++03.
For compilers with rvalue references this function provides perfect forwarding.
Otherwise:
If input_reference binds to const ::boost::rv<T> & then it output_reference is ::boost::rv<T> &
Else, output_reference is equal to input_reference.