Method lower

include/boost/histogram/axis/interval_view.hpp:29–31

  int idx() const noexcept { return idx_; }

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