mp_units::get_common_reference

template<
    Reference R1,
    Reference R2,
    Reference... Rest>
[[nodiscard]]
consteval
Reference auto
get_common_reference(
    auto u1,
    auto u2,
    auto... rest)
requires (!(MP_UNITS_ASSOCIATED_UNIT_T(R1) && MP_UNITS_ASSOCIATED_UNIT_T(R2) &&
             (... && MP_UNITS_ASSOCIATED_UNIT_T(Rest)))) &&
          requires {
            get_common_quantity_spec(get_quantity_spec(r1), get_quantity_spec(r2), get_quantity_spec(rest)...);
            get_common_unit(get_unit(r1), get_unit(r2), get_unit(rest)...);
          };