std::reference_wrapper::operator() (3) Linux Manual Page
std::reference_wrapper<T>::operator= – std::reference_wrapper<T>::operator=
Synopsis
reference_wrapper &operator=(const reference_wrapper<T> &other) noexcept;
(since C++ 11)Copy assignment operator. Drops the current reference and stores a reference to other.get().
Parameters
other – reference wrapper to copy
Return values
*this