From c2e5532ae21bfedb676eec227f6e097fd3f88e6c Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Sun, 10 Nov 2019 00:16:41 +0000
Subject: [PATCH] Basic support for deduced units printing added

---
 src/include/units/dimension.h                 |  6 ++-
 src/include/units/dimensions/acceleration.h   |  2 +-
 src/include/units/dimensions/area.h           |  2 +-
 .../units/dimensions/electric_charge.h        |  2 +-
 src/include/units/dimensions/force.h          |  2 +-
 src/include/units/dimensions/frequency.h      |  2 +-
 src/include/units/dimensions/power.h          |  2 +-
 src/include/units/dimensions/velocity.h       |  2 +-
 src/include/units/dimensions/voltage.h        |  2 +-
 src/include/units/dimensions/volume.h         |  2 +-
 src/include/units/unit.h                      | 46 +++++++++++++------
 11 files changed, 47 insertions(+), 23 deletions(-)

diff --git a/src/include/units/dimension.h b/src/include/units/dimension.h
index 7ac6f7b0..2ff0ca49 100644
--- a/src/include/units/dimension.h
+++ b/src/include/units/dimension.h
@@ -141,9 +141,13 @@ namespace units {
   struct dimension : downcast_base<dimension<Es...>> {};
 
   // same_dim
-  template<Dimension D1, Dimension D2>
+  template<typename D1, Dimension D2>
+    requires BaseDimension<D1> || Dimension<D1>
   inline constexpr bool same_dim = std::is_same_v<typename D1::base_type, typename D2::base_type>;
 
+  template<BaseDimension D1, Dimension D2>
+  inline constexpr bool same_dim<D1, D2> = std::is_same_v<dimension<units::exp<D1, 1>>, typename D2::base_type>;
+
   // dim_invert
   namespace detail {
 
diff --git a/src/include/units/dimensions/acceleration.h b/src/include/units/dimensions/acceleration.h
index de4f9d73..891ad786 100644
--- a/src/include/units/dimensions/acceleration.h
+++ b/src/include/units/dimensions/acceleration.h
@@ -26,7 +26,7 @@
 
 namespace units {
 
-  struct acceleration : derived_dimension<acceleration, exp<velocity, 1>, exp<base_dim_time, -1>> {};
+  struct acceleration : derived_dimension<acceleration, exp<velocity, 1>, exp<time, -1>> {};
 
   template<typename T>
   concept Acceleration = QuantityOf<T, acceleration>;
diff --git a/src/include/units/dimensions/area.h b/src/include/units/dimensions/area.h
index b5d36938..1a8e8830 100644
--- a/src/include/units/dimensions/area.h
+++ b/src/include/units/dimensions/area.h
@@ -26,7 +26,7 @@
 
 namespace units {
 
-  struct area : derived_dimension<area, exp<base_dim_length, 2>> {};
+  struct area : derived_dimension<area, exp<length, 2>> {};
 
   template<typename T>
   concept Area = QuantityOf<T, area>;
diff --git a/src/include/units/dimensions/electric_charge.h b/src/include/units/dimensions/electric_charge.h
index 20586ef8..31cd410f 100644
--- a/src/include/units/dimensions/electric_charge.h
+++ b/src/include/units/dimensions/electric_charge.h
@@ -28,7 +28,7 @@
 
 namespace units {
 
-  struct electric_charge : derived_dimension<electric_charge, exp<base_dim_time, 1>, exp<base_dim_current, 1>> {};
+  struct electric_charge : derived_dimension<electric_charge, exp<time, 1>, exp<current, 1>> {};
 
   template<typename T>
   concept ElectricCharge =  QuantityOf<T, electric_charge>;
diff --git a/src/include/units/dimensions/force.h b/src/include/units/dimensions/force.h
index 798b3220..5ec11f3d 100644
--- a/src/include/units/dimensions/force.h
+++ b/src/include/units/dimensions/force.h
@@ -28,7 +28,7 @@
 
 namespace units {
 
-  struct force : derived_dimension<force, exp<base_dim_mass, 1>, exp<acceleration, 1>> {};
+  struct force : derived_dimension<force, exp<mass, 1>, exp<acceleration, 1>> {};
 
   template<typename T>
   concept Force =  QuantityOf<T, force>;
diff --git a/src/include/units/dimensions/frequency.h b/src/include/units/dimensions/frequency.h
index ff01380f..3594a22b 100644
--- a/src/include/units/dimensions/frequency.h
+++ b/src/include/units/dimensions/frequency.h
@@ -28,7 +28,7 @@
 
 namespace units {
 
-  struct frequency : derived_dimension<frequency, exp<base_dim_time, -1>> {};
+  struct frequency : derived_dimension<frequency, exp<time, -1>> {};
 
   template<typename T>
   concept Frequency =  QuantityOf<T, frequency>;
diff --git a/src/include/units/dimensions/power.h b/src/include/units/dimensions/power.h
index d83642da..afffb2d2 100644
--- a/src/include/units/dimensions/power.h
+++ b/src/include/units/dimensions/power.h
@@ -28,7 +28,7 @@
 
 namespace units {
 
-  struct power : derived_dimension<power, exp<energy, 1>, exp<base_dim_time, -1>> {};
+  struct power : derived_dimension<power, exp<energy, 1>, exp<time, -1>> {};
 
   template<typename T>
   concept Power =  QuantityOf<T, power>;
diff --git a/src/include/units/dimensions/velocity.h b/src/include/units/dimensions/velocity.h
index 9b58a118..e583fba9 100644
--- a/src/include/units/dimensions/velocity.h
+++ b/src/include/units/dimensions/velocity.h
@@ -27,7 +27,7 @@
 
 namespace units {
 
-  struct velocity : derived_dimension<velocity, exp<base_dim_length, 1>, exp<base_dim_time, -1>> {};
+  struct velocity : derived_dimension<velocity, exp<length, 1>, exp<time, -1>> {};
 
   template<typename T>
   concept Velocity = QuantityOf<T, velocity>;
diff --git a/src/include/units/dimensions/voltage.h b/src/include/units/dimensions/voltage.h
index b4581061..f862a873 100644
--- a/src/include/units/dimensions/voltage.h
+++ b/src/include/units/dimensions/voltage.h
@@ -30,7 +30,7 @@
 
 namespace units {
 
-  struct voltage : derived_dimension<voltage, exp<power, 1>, exp<base_dim_current, -1>> {};
+  struct voltage : derived_dimension<voltage, exp<power, 1>, exp<current, -1>> {};
 
   template<typename T>
   concept Voltage =  QuantityOf<T, voltage>;
diff --git a/src/include/units/dimensions/volume.h b/src/include/units/dimensions/volume.h
index 3e2a55c3..bdd549d4 100644
--- a/src/include/units/dimensions/volume.h
+++ b/src/include/units/dimensions/volume.h
@@ -26,7 +26,7 @@
 
 namespace units {
 
-  struct volume : derived_dimension<volume, exp<base_dim_length, 3>> {};
+  struct volume : derived_dimension<volume, exp<length, 3>> {};
 
   template<typename T>
   concept Volume = QuantityOf<T, volume>;
diff --git a/src/include/units/unit.h b/src/include/units/unit.h
index 218e80c8..62aa9f75 100644
--- a/src/include/units/unit.h
+++ b/src/include/units/unit.h
@@ -53,7 +53,7 @@ namespace units {
       std::is_empty_v<T> &&
       detail::is_unit<downcast_base_t<T>>;
 
-  // make_derived_unit
+  // deduced_derived_unit
 
   namespace detail {
 
@@ -110,7 +110,7 @@ namespace units {
     };
 
     template<Dimension D, Unit... Us>
-    using make_derived_unit = unit<D, typename detail::derived_ratio<typename D::base_type, Us...>::ratio>;
+    using deduced_derived_unit = unit<D, typename detail::derived_ratio<typename D::base_type, Us...>::ratio>;
 
   }
 
@@ -214,11 +214,11 @@ namespace units {
       }
     }
 
-    template<typename E, std::size_t Idx>
+    template<typename E, basic_fixed_string Symbol, std::size_t Idx>
     constexpr auto exp_text()
     {
       // get calculation operator + symbol
-      const auto txt = operator_text<E::num < 0, Idx>() + E::dimension::symbol;
+      const auto txt = operator_text<E::num < 0, Idx>() + Symbol;
       if constexpr(E::den != 1) {
         // add root part
         return txt + basic_fixed_string("^(") + regular<abs(E::num)>() + basic_fixed_string("/") + regular<E::den>() + basic_fixed_string(")");
@@ -233,15 +233,35 @@ namespace units {
     }
 
     template<typename... Es, std::size_t... Idxs>
-    constexpr auto symbol_text_impl(dimension<Es...>, std::index_sequence<Idxs...>)
+    constexpr auto base_symbol_text_impl(dimension<Es...>, std::index_sequence<Idxs...>)
     {
-      return (exp_text<Es, Idxs>() + ...);
+      return (exp_text<Es, Es::dimension::symbol, Idxs>() + ...);
     }
 
     template<typename... Es>
-    constexpr auto symbol_text(dimension<Es...> d)
+    constexpr auto base_symbol_text(dimension<Es...> d)
     {
-      return symbol_text_impl<>(d, std::index_sequence_for<Es...>());
+      return base_symbol_text_impl(d, std::index_sequence_for<Es...>());
+    }
+
+    template<typename E, typename U, std::size_t Idx>
+    constexpr auto exp_validate_and_text()
+    {
+      static_assert(same_dim<typename E::dimension, typename U::dimension>);
+      return exp_text<E, U::symbol, Idx>();
+    }
+
+    template<typename... Us, typename... Es, std::size_t... Idxs>
+    constexpr auto deduced_symbol_text_impl(dimension<Es...>, std::index_sequence<Idxs...>)
+    {
+      return (exp_validate_and_text<Es, Us, Idxs>() + ...);
+    }
+
+    template<typename... Us, typename... Es>
+    constexpr auto deduced_symbol_text(dimension<Es...> d)
+    {
+      static_assert(sizeof...(Us) == sizeof...(Es), "`deduced_derived_unit<Us...>` should get the same number of exponents as provided to `derived_dimension<>`");
+      return deduced_symbol_text_impl<Us...>(d, std::index_sequence_for<Es...>());
     }
 
     template<typename Unit>
@@ -263,7 +283,7 @@ namespace units {
         }
         else {
           // print as a ratio of a coherent unit + coherent unit dimensions and their exponents
-          return ratio_text<ratio>() + symbol_text(dim{});
+          return ratio_text<ratio>() + base_symbol_text(dim{});
         }
       }
     }
@@ -281,7 +301,7 @@ namespace units {
 
   template<typename Child, Dimension Dim>
   struct coherent_derived_unit : downcast_child<Child, unit<Dim, ratio<1>>> {
-    static constexpr auto symbol = detail::symbol_text(Dim());
+    static constexpr auto symbol = detail::base_symbol_text(Dim());
     using prefix_type = no_prefix;
   };
 
@@ -292,14 +312,14 @@ namespace units {
   };
 
   template<typename Child, Dimension Dim, basic_fixed_string Symbol, PrefixType PT, Unit U, Unit... Us>
-  struct named_deduced_derived_unit : downcast_child<Child, detail::make_derived_unit<Dim, U, Us...>> {
+  struct named_deduced_derived_unit : downcast_child<Child, detail::deduced_derived_unit<Dim, U, Us...>> {
     static constexpr auto symbol = Symbol;
     using prefix_type = PT;
   };
 
   template<typename Child, Dimension Dim, Unit U, Unit... Us>
-  struct deduced_derived_unit : downcast_child<Child, detail::make_derived_unit<Dim, U, Us...>> {
-    static constexpr auto symbol = basic_fixed_string("bbb");
+  struct deduced_derived_unit : downcast_child<Child, detail::deduced_derived_unit<Dim, U, Us...>> {
+    static constexpr auto symbol = detail::deduced_symbol_text<U, Us...>(Dim());
     using prefix_type = no_prefix;
   };