Quantity reference type
<mp-units/framework/reference.h>template<
QuantitySpec Q,
Unit U>
struct reference;Quantity reference describes all the properties of a quantity besides its representation type.
In most cases this class template is not explicitly instantiated by the user. It is implicitly instantiated by the library's framework while binding a quantity specification with a compatible unit.
{.cpp}
Reference auto kmph = isq::speed[km / h];
QuantityOf<isq::speed[km / h]> auto speed = 90 * kmph;
The following syntaxes are not allowed: 2 / kmph, kmph * 3, kmph / 4, 70 * isq::length[km] / isq:time[h].