Units and dimensions redesigned

src/include/units/base_dimension.h

@@ -0,0 +1,75 @@
+// 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/fixed_string.h>
+#include <units/bits/unit_concept.h>
+#include <units/unit.h>
+#include <type_traits>
+
+namespace units {
+
+/**
+ * @brief A dimension of a base quantity
+ *
+ * Measurement unit that is adopted by convention for a base quantity (a quantity that can not be expressed in terms of
+ * the other quantities within that subset) in a specific system of units.
+ *
+ * Pair of Name and Unit template parameter forms an unique identifier of the base dimension. The same identifiers can
+ * be multiplied and divided which will result with an adjustment of its factor in an Exponent (in case of zero the
+ * dimension will be simplified and removed from further analysis of current expresion). In case the Name is the same
+ * but the Unit differs (i.e. mixing SI and CGS length), there is no automatic simplification but is possible to force
+ * it with a quantity_cast.
+ *
+ * @tparam Name an unique identifier of the base dimension used to provide dimensional analysis support
+ * @tparam U a base unit to be used for this base dimension
+ */
+template<basic_fixed_string Name, Unit U>
+struct base_dimension {
+  using base_type = base_dimension;
+  static constexpr auto name = Name;
+  using coherent_unit = U;
+};
+
+// BaseDimension
+namespace detail {
+
+template<typename T>
+inline constexpr bool is_base_dimension = false;
+
+template<basic_fixed_string Name, typename... Params>
+inline constexpr bool is_base_dimension<base_dimension<Name, Params...>> = true;
+
+}  // namespace detail
+
+template<typename T>
+concept BaseDimension = detail::is_base_dimension<typename T::base_type>;
+
+// base_dimension_less
+// TODO Remove the below when https://bugs.llvm.org/show_bug.cgi?id=32208 is fixed
+// clang-format off
+template<BaseDimension D1, BaseDimension D2>
+struct base_dimension_less : std::bool_constant<D1::name < D2::name> {};
+// clang-format on
+
+}  // namespace units