mp_units::quantity::operator‐‐

constexpr
quantity&
operator‐‐() &
requires requires(rep& v) {
      { ‐‐v } ‐> std::same_as<rep&>;
    };

[[nodiscard]]
constexpr
QuantityOf<quantity_spec> auto
operator‐‐(int)
requires requires(rep& v) {
      { v‐‐ } ‐> std::common_with<rep>;
    };