derived_dimension code split to a few smaller files

src/include/units/bits/dim_unpack.h

@@ -0,0 +1,59 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <units/bits/derived_dimension_base.h>
+#include <units/bits/external/type_list.h>
+#include <units/exp.h>
+
+namespace units::detail {
+
+/**
+ * @brief Unpacks the list of potentially derived dimensions to a list containing only base dimensions
+ * 
+ * @tparam Es Exponents of potentially derived dimensions 
+ */
+template<Exponent... Es>
+struct dim_unpack;
+
+template<>
+struct dim_unpack<> {
+  using type = exp_list<>;
+};
+
+template<BaseDimension Dim, int Num, int Den, Exponent... ERest>
+struct dim_unpack<exp<Dim, Num, Den>, ERest...> {
+  using type = type_list_push_front<typename dim_unpack<ERest...>::type, exp<Dim, Num, Den>>;
+};
+
+template<DerivedDimension Dim, int Num, int Den, Exponent... ERest>
+struct dim_unpack<exp<Dim, Num, Den>, ERest...> {
+  using type = dim_unpack<exp<downcast_base_t<Dim>, Num, Den>, ERest...>::type;
+};
+
+template<Exponent... Es, int Num, int Den, Exponent... ERest>
+struct dim_unpack<exp<derived_dimension_base<Es...>, Num, Den>, ERest...> {
+  using type = type_list_push_front<typename dim_unpack<ERest...>::type, exp_multiply<Es, Num, Den>...>;
+};
+
+}  // namespace units::detail