From 979a00e7041b36368eb4c2c25b9a67bff08fb0f3 Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Mon, 19 Dec 2022 20:35:22 +0100
Subject: [PATCH] fix: `get_canonical_unit()` fixed for powers of derived
 quantities

---
 src/core/include/units/unit.h                 | 42 ++++++++++++-------
 .../{isq-natural => natural}/CMakeLists.txt   | 22 +++++-----
 .../include/units}/natural/acceleration.h     |  0
 .../include/units}/natural/constants.h        |  0
 .../include/units}/natural/energy.h           |  0
 .../include/units}/natural/force.h            |  0
 .../include/units}/natural/length.h           |  0
 .../include/units}/natural/mass.h             |  0
 .../include/units}/natural/momentum.h         |  0
 .../include/units}/natural/natural.h          |  0
 .../include/units}/natural/speed.h            |  0
 .../include/units}/natural/time.h             |  0
 .../include/units}/natural/units.h            |  0
 13 files changed, 39 insertions(+), 25 deletions(-)
 rename src/systems/{isq-natural => natural}/CMakeLists.txt (72%)
 rename src/systems/{isq-natural/include/units/isq => natural/include/units}/natural/acceleration.h (100%)
 rename src/systems/{isq-natural/include/units/isq => natural/include/units}/natural/constants.h (100%)
 rename src/systems/{isq-natural/include/units/isq => natural/include/units}/natural/energy.h (100%)
 rename src/systems/{isq-natural/include/units/isq => natural/include/units}/natural/force.h (100%)
 rename src/systems/{isq-natural/include/units/isq => natural/include/units}/natural/length.h (100%)
 rename src/systems/{isq-natural/include/units/isq => natural/include/units}/natural/mass.h (100%)
 rename src/systems/{isq-natural/include/units/isq => natural/include/units}/natural/momentum.h (100%)
 rename src/systems/{isq-natural/include/units/isq => natural/include/units}/natural/natural.h (100%)
 rename src/systems/{isq-natural/include/units/isq => natural/include/units}/natural/speed.h (100%)
 rename src/systems/{isq-natural/include/units/isq => natural/include/units}/natural/time.h (100%)
 rename src/systems/{isq-natural/include/units/isq => natural/include/units}/natural/units.h (100%)

diff --git a/src/core/include/units/unit.h b/src/core/include/units/unit.h
index ea2a3e2d..89f279ba 100644
--- a/src/core/include/units/unit.h
+++ b/src/core/include/units/unit.h
@@ -479,29 +479,43 @@ template<Unit T, basic_symbol_text Symbol, Unit auto U>
   return get_canonical_unit_impl(U, U);
 }
 
+template<typename F, int Num, int... Den, typename... Us>
+[[nodiscard]] consteval auto get_canonical_unit_impl(const power<F, Num, Den...>&, const type_list<Us...>&)
+{
+  auto mag = (units::mag<1> * ... * pow<Num, Den...>(get_canonical_unit_impl(Us{}, Us{}).mag));
+  auto u = (one * ... * pow<Num, Den...>(get_canonical_unit_impl(Us{}, Us{}).reference_unit));
+  return canonical_unit{mag, u};
+}
+
 template<typename T, typename F, int Num, int... Den>
 [[nodiscard]] consteval auto get_canonical_unit_impl(T, const power<F, Num, Den...>&)
 {
   auto base = get_canonical_unit_impl(F{}, F{});
-  return canonical_unit{
-    pow<power<F, Num, Den...>::exponent>(base.mag),
-    derived_unit<power_or_T<std::remove_const_t<decltype(base.reference_unit)>, power<F, Num, Den...>::exponent>>{}};
+  if constexpr (requires { typename decltype(base.reference_unit)::_num_; }) {
+    auto num = get_canonical_unit_impl(power<F, Num, Den...>{}, typename decltype(base.reference_unit)::_num_{});
+    auto den = get_canonical_unit_impl(power<F, Num, Den...>{}, typename decltype(base.reference_unit)::_den_{});
+    return canonical_unit{pow<power<F, Num, Den...>::exponent>(base.mag) * num.mag / den.mag,
+                          num.reference_unit / den.reference_unit};
+  } else {
+    return canonical_unit{pow<power<F, Num, Den...>::exponent>(base.mag),
+                          derived_unit<power<std::remove_const_t<decltype(base.reference_unit)>, Num, Den...>>{}};
+  }
+}
+
+template<typename... Us>
+[[nodiscard]] consteval auto get_canonical_unit_impl(const type_list<Us...>&)
+{
+  auto mag = (units::mag<1> * ... * get_canonical_unit_impl(Us{}, Us{}).mag);
+  auto u = (one * ... * get_canonical_unit_impl(Us{}, Us{}).reference_unit);
+  return canonical_unit{mag, u};
 }
 
 template<Unit T, typename... Us>
 [[nodiscard]] consteval auto get_canonical_unit_impl(T, const derived_unit<Us...>&)
 {
-  if constexpr (type_list_size<typename derived_unit<Us...>::_den_> != 0) {
-    using num_type = type_list_map<typename derived_unit<Us...>::_num_, derived_unit>;
-    using den_type = type_list_map<typename derived_unit<Us...>::_den_, derived_unit>;
-    auto num = get_canonical_unit_impl(num_type{}, num_type{});
-    auto den = get_canonical_unit_impl(den_type{}, den_type{});
-    return canonical_unit{num.mag / den.mag, num.reference_unit / den.reference_unit};
-  } else {
-    auto num = (one * ... * get_canonical_unit_impl(Us{}, Us{}).reference_unit);
-    auto mag = (units::mag<1> * ... * get_canonical_unit_impl(Us{}, Us{}).mag);
-    return canonical_unit{mag, num};
-  }
+  auto num = get_canonical_unit_impl(typename derived_unit<Us...>::_num_{});
+  auto den = get_canonical_unit_impl(typename derived_unit<Us...>::_den_{});
+  return canonical_unit{num.mag / den.mag, num.reference_unit / den.reference_unit};
 }
 
 [[nodiscard]] consteval auto get_canonical_unit(Unit auto u) { return get_canonical_unit_impl(u, u); }
diff --git a/src/systems/isq-natural/CMakeLists.txt b/src/systems/natural/CMakeLists.txt
similarity index 72%
rename from src/systems/isq-natural/CMakeLists.txt
rename to src/systems/natural/CMakeLists.txt
index e968bdff..f48268bc 100644
--- a/src/systems/isq-natural/CMakeLists.txt
+++ b/src/systems/natural/CMakeLists.txt
@@ -23,17 +23,17 @@
 cmake_minimum_required(VERSION 3.19)
 
 add_units_module(
-    isq-natural
+    natural
     DEPENDENCIES mp-units::isq
     HEADERS include/units/isq/natural/acceleration.h
-            include/units/isq/natural/constants.h
-            include/units/isq/natural/energy.h
-            include/units/isq/natural/force.h
-            include/units/isq/natural/length.h
-            include/units/isq/natural/mass.h
-            include/units/isq/natural/momentum.h
-            include/units/isq/natural/natural.h
-            include/units/isq/natural/speed.h
-            include/units/isq/natural/time.h
-            include/units/isq/natural/units.h
+    include/units/isq/natural/constants.h
+    include/units/isq/natural/energy.h
+    include/units/isq/natural/force.h
+    include/units/isq/natural/length.h
+    include/units/isq/natural/mass.h
+    include/units/isq/natural/momentum.h
+    include/units/isq/natural/natural.h
+    include/units/isq/natural/speed.h
+    include/units/isq/natural/time.h
+    include/units/isq/natural/units.h
 )
diff --git a/src/systems/isq-natural/include/units/isq/natural/acceleration.h b/src/systems/natural/include/units/natural/acceleration.h
similarity index 100%
rename from src/systems/isq-natural/include/units/isq/natural/acceleration.h
rename to src/systems/natural/include/units/natural/acceleration.h
diff --git a/src/systems/isq-natural/include/units/isq/natural/constants.h b/src/systems/natural/include/units/natural/constants.h
similarity index 100%
rename from src/systems/isq-natural/include/units/isq/natural/constants.h
rename to src/systems/natural/include/units/natural/constants.h
diff --git a/src/systems/isq-natural/include/units/isq/natural/energy.h b/src/systems/natural/include/units/natural/energy.h
similarity index 100%
rename from src/systems/isq-natural/include/units/isq/natural/energy.h
rename to src/systems/natural/include/units/natural/energy.h
diff --git a/src/systems/isq-natural/include/units/isq/natural/force.h b/src/systems/natural/include/units/natural/force.h
similarity index 100%
rename from src/systems/isq-natural/include/units/isq/natural/force.h
rename to src/systems/natural/include/units/natural/force.h
diff --git a/src/systems/isq-natural/include/units/isq/natural/length.h b/src/systems/natural/include/units/natural/length.h
similarity index 100%
rename from src/systems/isq-natural/include/units/isq/natural/length.h
rename to src/systems/natural/include/units/natural/length.h
diff --git a/src/systems/isq-natural/include/units/isq/natural/mass.h b/src/systems/natural/include/units/natural/mass.h
similarity index 100%
rename from src/systems/isq-natural/include/units/isq/natural/mass.h
rename to src/systems/natural/include/units/natural/mass.h
diff --git a/src/systems/isq-natural/include/units/isq/natural/momentum.h b/src/systems/natural/include/units/natural/momentum.h
similarity index 100%
rename from src/systems/isq-natural/include/units/isq/natural/momentum.h
rename to src/systems/natural/include/units/natural/momentum.h
diff --git a/src/systems/isq-natural/include/units/isq/natural/natural.h b/src/systems/natural/include/units/natural/natural.h
similarity index 100%
rename from src/systems/isq-natural/include/units/isq/natural/natural.h
rename to src/systems/natural/include/units/natural/natural.h
diff --git a/src/systems/isq-natural/include/units/isq/natural/speed.h b/src/systems/natural/include/units/natural/speed.h
similarity index 100%
rename from src/systems/isq-natural/include/units/isq/natural/speed.h
rename to src/systems/natural/include/units/natural/speed.h
diff --git a/src/systems/isq-natural/include/units/isq/natural/time.h b/src/systems/natural/include/units/natural/time.h
similarity index 100%
rename from src/systems/isq-natural/include/units/isq/natural/time.h
rename to src/systems/natural/include/units/natural/time.h
diff --git a/src/systems/isq-natural/include/units/isq/natural/units.h b/src/systems/natural/include/units/natural/units.h
similarity index 100%
rename from src/systems/isq-natural/include/units/isq/natural/units.h
rename to src/systems/natural/include/units/natural/units.h