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feat: users are now allowed to inherit their ow types from absolute point origins

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Mateusz Pusz
2023-12-03 16:15:38 +01:00
parent 611e380ed4
commit da8721b997
11 changed files with 133 additions and 61 deletions
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docs/users_guide/framework_basics/the_affine_space.md
+10 -3
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@@ -64,9 +64,16 @@ The **absolute point origin** specifies where the "zero" of our measurement's sc
specify such an origin by deriving from the `absolute_point_origin` class template:
```cpp
constexpr struct mean_sea_level : absolute_point_origin<isq::altitude> {} mean_sea_level;
constexpr struct mean_sea_level : absolute_point_origin<mean_sea_level, isq::altitude> {} mean_sea_level;
```
!!! info
The `absolute_point_origin` class template uses CRTP idiom to enforce the uniqueness of such a type.
You should pass the type of a derived class as the first argument of the template instantiation.
*[CRTP]: Curiously Recurring Template Parameter
### `quantity_point`
The `quantity_point` class template specifies an absolute quantity with respect to an origin:
@@ -185,7 +192,7 @@ the distance we will travel. We have to take a taxi to a local airport, fly to D
a stopover in FRA, and, in the end, get a cab to the Gaylord Rockies Resort & Convention Center:
```cpp
constexpr struct home : absolute_point_origin<isq::distance> {} home;
constexpr struct home : absolute_point_origin<home, isq::distance> {} home;
quantity_point<isq::distance[km], home> home_airport = home + 15 * km;
quantity_point<isq::distance[km], home> fra_airport = home_airport + 829 * km;
@@ -246,7 +253,7 @@ two predefined point origins:
```cpp
namespace mp_units::si {
inline constexpr struct absolute_zero : absolute_point_origin<isq::thermodynamic_temperature> {} absolute_zero;
inline constexpr struct absolute_zero : absolute_point_origin<absolute_zero, isq::thermodynamic_temperature> {} absolute_zero;
inline constexpr struct ice_point : relative_point_origin<absolute_zero + 273.15 * kelvin> {} ice_point;
}