Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

Struct template unwrap_reference

boost::unwrap_reference — Find the type in a `reference_wrapper`.

// In header: <boost/core/ref.hpp>

template<typename T> 
struct unwrap_reference {
  // types
  typedef T type;
};

The `typedef` type is `T::type` if `T` is a `reference_wrapper`, `T` otherwise.