From 021df4a46f0c992426eefb1d133c2ca613907c6b Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Wed, 18 Sep 2019 15:32:22 -0600
Subject: [PATCH] dimension_sqrt and dimension_pow support added

---
 src/include/units/dimension.h        | 26 +++++++++++++++++++++++++-
 test/unit_test/test_custom_units.cpp |  3 +++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/include/units/dimension.h b/src/include/units/dimension.h
index 1d5e947d..700452a2 100644
--- a/src/include/units/dimension.h
+++ b/src/include/units/dimension.h
@@ -130,7 +130,11 @@ namespace std::experimental::units {
 
   template<Exponent E, int Num, int Den>
   struct exp_multiply {
-    using type = exp<typename E::dimension, E::num * Num, E::den * Den>;
+    // todo: provide custom implementation for ratio_add
+    using r1 = std::ratio<E::num, E::den>;
+    using r2 = std::ratio<Num, Den>;
+    using r = std::ratio_multiply<r1, r2>;
+    using type = exp<typename E::dimension, r::num, r::den>;
   };
 
   template<Exponent E, int Num, int Den>
@@ -257,4 +261,24 @@ namespace std::experimental::units {
   template<Dimension D1, Dimension D2>
   using dimension_divide_t = dimension_divide<typename D1::base_type, typename D2::base_type>::type;
 
+  // dimension_sqrt
+  template<Dimension D>
+  struct dimension_sqrt;
+
+  template<typename... Es>
+  struct dimension_sqrt<dimension<Es...>> : std::type_identity<downcasting_traits_t<dimension<exp_multiply_t<Es, 1, 2>...>>> {};
+
+  template<Dimension D>
+  using dimension_sqrt_t = dimension_sqrt<typename D::base_type>::type;
+
+  // dimension_pow
+  template<Dimension D, std::size_t N>
+  struct dimension_pow;
+
+  template<typename... Es, std::size_t N>
+  struct dimension_pow<dimension<Es...>, N> : std::type_identity<downcasting_traits_t<dimension<exp_multiply_t<Es, N, 1>...>>> {};
+
+  template<Dimension D, std::size_t N>
+  using dimension_pow_t = dimension_pow<typename D::base_type, N>::type;
+
 }  // namespace std::experimental::units
diff --git a/test/unit_test/test_custom_units.cpp b/test/unit_test/test_custom_units.cpp
index 1d03c421..f8991953 100644
--- a/test/unit_test/test_custom_units.cpp
+++ b/test/unit_test/test_custom_units.cpp
@@ -90,6 +90,9 @@ template<> struct downcasting_traits<downcast_from<volt_per_sqrt_hertz>> : downc
 
 namespace {
 
+  static_assert(std::is_same_v<dimension_sqrt_t<power_spectral_density>, amplitude_spectral_density>);
+  static_assert(std::is_same_v<dimension_pow_t<amplitude_spectral_density, 2>, power_spectral_density>);
+
   //static_assert(sqrt(quantity<sq_volt_per_hertz>(4)) = quantity<volt_per_sqrt_hertz>(2));
 
 }