Boost C++ Libraries

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Struct template is_reference_wrapper

boost::is_reference_wrapper — Determine if a type T is an instantiation of reference_wrapper.

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

template<typename T> 
struct is_reference_wrapper {

  // public data members
  static constexpr bool value;
};

The value static constant will be true if the type T is a specialization of reference_wrapper.