Physical units put in the physical namespace (I am sorry)

docs/DESIGN.md

@@ -148,7 +148,7 @@ in the design documentation.
 Coming back to units, here are a few examples of unit definitions:
 
 ```cpp
-namespace units::si {
+namespace units::physical::si {
 
 // prefixes
 struct prefix : prefix_family {};
@@ -170,7 +170,7 @@ struct kilometre_per_hour : deduced_unit<kilometre_per_hour, dim_velocity, kilom
 
 }
 
-namespace units::us {
+namespace units::physical::us {
 
 // length
 struct yard : named_scaled_unit<yard, "yd", no_prefix, ratio<9'144, 10'000>, si::metre> {};
@@ -224,7 +224,7 @@ These identifiers provide total ordering of exponents of base dimensions in a de
 The SI physical units system defines 7 base dimensions:
 
 ```cpp
-namespace units::si {
+namespace units::physical::si {
 
 struct dim_length : base_dimension<"L", metre> {};
 struct dim_mass : base_dimension<"M", kilogram> {};
@@ -244,7 +244,7 @@ base unit is needed for the text output of unnamed derived units. Second, there
 one system of physical units. For example CGS definitions look as follows:
 
 ```cpp
-namespace units::cgs {
+namespace units::physical::cgs {
 
 using si::centimetre;
 using si::gram;
@@ -354,7 +354,7 @@ directly define a barye in terms of pascal or vice versa.
 Below are a few examples of derived dimension definitions:
 
 ```cpp
-namespace units::si {
+namespace units::physical::si {
 
 struct dim_velocity : derived_dimension<dim_velocity, metre_per_second,
                                         exp<dim_length, 1>, exp<dim_time, -1>> {};
@@ -448,8 +448,8 @@ Beside adding new elements a few other changes where applied compared to the `st
 
 To simplify writing efficient generic code quantities of each dimension have associated:
 1. Concept (i.e. `units::Length`) that matches a length dimension of any physical systems.
-2. Per-system quantity alias (i.e. `units::si::length<Unit, Rep>` for
-  `units::quantity<units::si::dim_length, Unit, Rep>`).
+2. Per-system quantity alias (i.e. `units::physical::si::length<Unit, Rep>` for
+  `units::quantity<units::physical::si::dim_length, Unit, Rep>`).
 
 Also, to help instantiate quantities with compile-time known values every unit in the library
 has an associated UDL. For example:
@@ -603,9 +603,9 @@ user. If we will get a compilation error message containing `dim_capacitance` in
 the compiler will print the following type instead of the alias:
 
 ```text
-units::detail::derived_dimension_base<units::exp<units::si::dim_electric_current, 2, 1>,
-units::exp<units::si::dim_length, -2, 1>, units::exp<units::si::dim_mass, -1, 1>,
-units::exp<units::si::dim_time, 4, 1> >
+units::detail::derived_dimension_base<units::exp<units::physical::si::dim_electric_current, 2, 1>,
+units::exp<units::physical::si::dim_length, -2, 1>, units::exp<units::physical::si::dim_mass, -1, 1>,
+units::exp<units::physical::si::dim_time, 4, 1> >
 ```
 
 You can notice that even this long syntax was carefully selected to provide quite good user
@@ -760,8 +760,8 @@ struct unknown_dimension : derived_dimension<unknown_dimension<E, ERest...>,
 with this the error log or a debugger breakpoint involving a `temp1` type will include:
 
 ```text
-units::quantity<units::unknown_dimension<units::exp<units::si::dim_length, 2, 1>,
-units::exp<units::si::dim_time, -1, 1> >, units::unknown_coherent_unit, long int>
+units::quantity<units::unknown_dimension<units::exp<units::physical::si::dim_length, 2, 1>,
+units::exp<units::physical::si::dim_time, -1, 1> >, units::unknown_coherent_unit, long int>
 ```
 
 

docs/design.rst

@@ -6,6 +6,7 @@ Design Deep Dive
     For brevity all the code examples in this chapter assume::
 
         using namespace units;
+        using namespace units::physical;
 
 .. toctree::
     :maxdepth: 2

docs/framework.rst

@@ -6,6 +6,7 @@ Framework Basics
     For brevity all the code examples in this chapter assume::
 
         using namespace units;
+        using namespace units::physical;
 
 .. toctree::
     :maxdepth: 2

docs/framework/quantities.rst

@@ -47,7 +47,7 @@ values the library provides :abbr:`UDL (User Defined Literal)` s for each
 :term:`unit` of every :term:`dimension`. Thanks to them the same code can
 be as simple as::
 
-    using namespace si::literals;
+    using namespace units::physical::si::literals;
     constexpr auto d1 = 123q_km;    // si::length<si::kilometre, std::int64_t>
     constexpr auto d2 = 123.q_km;   // si::length<si::kilometre, long double>
 
@@ -66,7 +66,7 @@ In case the user does not care about the specific unit and representation but
 requires quantity of a concrete dimension than dimension-specific concepts can
 be used::
 
-    using namespace si::literals;
+    using namespace units::physical::si::literals;
     constexpr Length auto d = 123q_km;  // si::length<si::kilometre, std::int64_t>
 
 .. note::
@@ -80,8 +80,8 @@ assume that the user wants to implement an ``avg_speed`` function that will
 be calculating the average speed based on provided distance and duration
 quantities. The usage of such a function can look as follows::
 
-    using namespace si::literals;
-    using namespace international::literals;
+    using namespace units::physical::si::literals;
+    using namespace units::physical::international::literals;
     constexpr Velocity auto v1 = avg_speed(220q_km, 2q_h);
     constexpr Velocity auto v2 = avg_speed(140q_mi, 2q_h);
 

docs/framework/text_output.rst

@@ -12,8 +12,8 @@ Output Streams
 The easiest way to print a quantity is to provide its object to the output
 stream::
 
-    using namespace si::literals;
-    using namespace international::literals;
+    using namespace units::physical::si::literals;
+    using namespace units::physical::international::literals;
     constexpr Velocity auto v1 = avg_speed(220.q_km, 2q_h);
     constexpr Velocity auto v2 = avg_speed(140.q_mi, 2q_h);
     std::cout << v1 << '\n';  // 110 km/h

docs/framework/units.rst

@@ -161,8 +161,8 @@ of ``N/m``):
     :emphasize-lines: 2
 
     struct dim_surface_tension : derived_dimension<dim_surface_tension, newton_per_metre,
-                                                    exp<si::dim_force, 1>,
-                                                    exp<si::dim_length, -1>> {}; // N/m
+                                                   exp<si::dim_force, 1>,
+                                                   exp<si::dim_length, -1>> {}; // N/m
 
 If we defined the above in terms of base units we would end up with
 a ``kg/s²`` derived unit symbol.
@@ -361,7 +361,7 @@ and user should not instantiate it by him/her-self. However the user can sometim
 observe this type in case an unit/dimension conversion expression will end up with an
 unknown/undefined unit type like in the below example::
 
-    using namespace si::literals;
+    using namespace units::physical::si::literals;
 
     Length auto l = 100q_km_per_h * 10q_s;
 

docs/quick_start.rst

@@ -32,7 +32,7 @@ of basic library features::
     #include <units/physical/international/velocity.h>
     #include <iostream>
 
-    using namespace units;
+    using namespace units::physical;
 
     constexpr Velocity auto avg_speed(Length auto d, Time auto t)
     {
@@ -41,7 +41,7 @@ of basic library features::
 
     int main()
     {
-      using namespace si::literals;
+      using namespace units::physical::si::literals;
       Velocity auto v1 = avg_speed(220q_km, 2q_h);
       Velocity auto v2 = avg_speed(si::length<international::mile>(140), si::time<si::hour>(2));
       Velocity auto v3 = quantity_cast<si::metre_per_second>(v2);

docs/reference/systems.rst

@@ -8,7 +8,7 @@ Systems
 SI
 --
 
-.. doxygennamespace:: units::si
+.. doxygennamespace:: units::physical::si
     :members:
     :undoc-members:
     :outline:

docs/use_cases.rst

@@ -6,6 +6,7 @@ Use Cases
     For brevity all the code examples in this chapter assume::
 
         using namespace units;
+        using namespace units::physical;
 
 .. toctree::
     :maxdepth: 2

docs/use_cases/legacy_interfaces.rst

@@ -21,7 +21,7 @@ pass it to the library's output:
     #include "legacy.h"
     #include <units/physical/si/velocity.h>
 
-    using namespace units;
+    using namespace units::physical;
 
     constexpr Velocity auto avg_speed(Length auto d, Time auto t)
     {