Method upper

include/boost/histogram/axis/interval_view.hpp:32–34

    return axis_.lower(idx_);
  }
  auto upper() const noexcept -> decltype(std::declval<Axis&>().lower(0)) {
    return axis_.lower(idx_ + 1);
  }
  typename Axis::value_type width() const noexcept {
    return upper() - lower();
  }