mp_units::quantity::numerical_value_ref_in

template<Unit U>
requires (equivalent(U{}, unit))
constexpr
rep const&&
numerical_value_ref_in(U) const && noexcept = delete;

template<Unit U>
requires (equivalent(U{}, unit))
[[nodiscard]]
constexpr
rep const&
numerical_value_ref_in(U) const & noexcept;

template<Unit U>
requires (equivalent(U{}, unit))
[[nodiscard]]
constexpr
rep&
numerical_value_ref_in(U) & noexcept;