<mp-units/framework/quantity_point.h>
template<
PointOrigin PO1,
std::derived_from<quantity_point> QP>
requires QuantityPointOf<quantity_point, PO1{}> &&
ReferenceOf<MP_UNITS_NONCONST_TYPE(reference), PO1::_quantity_spec_>
[[nodiscard]]
constexpr
Quantity auto
operator-(
PO1 po,
QP const& qp);