Structural types

[mpusz]

Structural types are the types that can be used as NTTPs. quantity and quantity_point do not satisfy a current definition of a structural type as it requires a class to have public data members. This means that we cannot put them in template parameters which could be really handy in some cases.

Should we make a data member public (at least until the C++ language will not extend the definition to allow private members as well)?

[JohelEGP]

Why not? There's already the number accessor, which essentially makes it public.

[mpusz]

A use case where I would like to use it right away is a quantity_point definition:

template<Reference auto R, OriginOffset auto OO = 0, RepresentationOf<R.quantity_spec.character> Rep = double>
class quantity_point;

constexpr auto room_reference_temperature = quantity_point{21 * isq::Celsius_temperature[deg_C]};
constexpr auto temperature_controller_delta = 3 * isq::Celsius_temperature[deg_C];

constexpr quantity_point<isq::Celsius_temperature[deg_C], room_reference_temperature> room_default{0};
constexpr quantity_point<isq::Celsius_temperature[deg_C], room_reference_temperature> room_low = room_default - temperature_controller_delta;
constexpr quantity_point<isq::Celsius_temperature[deg_C], room_reference_temperature> room_high = room_default + temperature_controller_delta;

BTW, I hate ISO 80000 for specifying separate quantities for thermodynamic_temperature and Celsius_temperature...

[mpusz]

Why not? There's already the number accessor, which essentially makes it public.

You are right! And actually, you highlighted a new issue #412.