Method operator==

include/dmlc/optional.h:112–115

! \brief equal comparison */

  }
  /*! \brief equal comparison */
  bool operator==(const optional<T>& other) const {
    return this->is_none == other.is_none &&
           (this->is_none == true || this->value() == other.value());
  }
  /*! \brief return the holded value.
   *         throws std::logic_error if holding no value
   */