build: core library and each system separated to dedicated CMake targets

Refers to #249

src/core/include/units/customization_points.h

@@ -0,0 +1,101 @@
+// 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/external/hacks.h>
+#include <limits>
+#include <type_traits>
+
+namespace units {
+
+/**
+ * @brief Specifies if a value of a type should be treated as a floating-point value
+ * 
+ * This type trait should be specialized for a custom representation type to specify
+ * that values fo this type should be treated by the library as a floating-point ones
+ * which will enable implicit conversions between quantities.
+ * 
+ * @tparam Rep a representation type for which a type trait is defined
+ */
+template<typename Rep>
+inline constexpr bool treat_as_floating_point = std::is_floating_point_v<Rep>;
+
+template<typename T>
+  requires requires { typename T::value_type; }
+inline constexpr bool treat_as_floating_point<T> = treat_as_floating_point<typename T::value_type>;
+
+/**
+ * @brief A type trait that defines zero, one, min, and max for a representation type
+ * 
+ * The zero, one, min, and max member functions in units::quantity forward their work to
+ * these methods. This type can be specialized if the representation Rep requires a specific
+ * implementation to return these quantity objects.
+ * 
+ * @tparam Rep a representation type for which a type trait is defined
+ */
+template<typename Rep>
+struct quantity_values {
+  static constexpr Rep zero() noexcept
+    requires std::constructible_from<Rep, int>
+  { return Rep(0); }
+
+  static constexpr Rep one() noexcept
+    requires std::constructible_from<Rep, int>
+  { return Rep(1); }
+
+  static constexpr Rep min() noexcept
+    requires requires { { std::numeric_limits<Rep>::lowest() } -> std::same_as<Rep>; }
+  { return std::numeric_limits<Rep>::lowest(); }
+
+  static constexpr Rep max() noexcept
+    requires requires { { std::numeric_limits<Rep>::max() } -> std::same_as<Rep>; }
+  { return std::numeric_limits<Rep>::max(); }
+};
+
+/**
+ * @brief Provides support for external quantity-like types
+ * 
+ * The type trait should provide the following nested type aliases: @c dimension, @c unit, @c rep,
+ * and a static member function @c count(T) that will return the raw value of the quantity.
+ * 
+ * Usage example can be found in @c units/chrono.h header file.
+ * 
+ * @tparam T the type to provide support for
+ */
+template<typename T>
+struct quantity_like_traits;
+
+/**
+ * @brief Provides support for external quantity point-like types
+ * 
+ * The type trait should provide the following nested type aliases: @c dimension, @c unit, @c rep,
+ * and a static member function @c relative(T) that will return the quantity-like value of the quantity point.
+ * 
+ * Usage example can be found in @c units/chrono.h header file.
+ * 
+ * @tparam T the type to provide support for
+ */
+template<typename T>
+struct quantity_point_like_traits;
+
+} // namespace units