mp_units::RepresentationOf

template<
    typename T,
    auto V>
concept RepresentationOf = (QuantitySpec<MP_UNITS_REMOVE_CONST(decltype(V))> &&
   detail::QuantityKindSpec<MP_UNITS_REMOVE_CONST(decltype(V> && detail::SomeRepresentation<T>) ||
    (detail::RepresentationOfOrder<T, detail::order_of(get_character(V))> &&
     detail::RepresentationOfField<T, detail::field_of(get_character(V))>))) ||
  detail::RepresentationOfCharacter<T, V>;