mp_units::system_reference

System-specific reference

Synopsis

Declared in <mp-units/framework/system_reference.h>

template<
    QuantitySpec auto Q,
    Unit auto CoU>
requires (!MP_UNITS_ASSOCIATED_UNIT_T(decltype(CoU))) || (CoU == one)
struct system_reference;

Member Functions

Name	Description
`operator[]`	Subscript operator

Static Data Members

Name
`coherent_unit`
`quantity_spec`

Description

This type is used in rare cases where more than one base quantity in a specific system of units uses the same unit. For example in a hypothetical system of natural units where constant for speed of light c = 1, length and time could be measured in seconds. In such cases system_reference has to be used to explicitly express such a binding.

For example:


{.cpp}
 // hypothetical natural system of units for c=1

 inline constexpr struct second final : named_unit<"s"> {} second;
 inline constexpr struct minute final : named_unit<"min", mag<60> * second> {} minute;
 inline constexpr struct gram final : named_unit<"g"> {} gram;
 inline constexpr auto kilogram = si::kilo;

 inline constexpr struct time : system_reference {} time;
 inline constexpr struct length : system_reference {} length;
 inline constexpr struct speed : system_reference {} speed;
 inline constexpr struct force : system_reference {} force;

Template Parameters