Mercurial > ldforge / file diff

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/generics/oneof.h	Sat Aug 04 21:46:58 2018 +0300
@@ -0,0 +1,65 @@
+#pragma once
+#include <array>
+
+namespace detail
+{
+	template<typename T, typename Vt>
+	constexpr bool oneOfCompare(const T& value, Vt *first, Vt *last)
+	{
+		return (first == last)
+			? false
+			: (*first) == value
+				? true
+				: detail::oneOfCompare(value, first + 1, last);
+	}
+
+	template<typename Vt, std::size_t N>
+	struct OneOfClass
+	{
+		std::array<Vt, N> parameters;
+
+		template<typename... Ts>
+		constexpr OneOfClass(Ts&&... parameters) :
+			parameters {{parameters...}} {}
+
+		template<typename T>
+		constexpr bool operator==(const T& value) const
+		{
+			return detail::oneOfCompare(value, &parameters[0], &parameters[N]);
+		}
+
+		template<typename T>
+		constexpr bool operator!=(const T& value) const
+		{
+			return !(*this == value);
+		}
+
+		template<typename T>
+		constexpr friend bool operator==(const T& value, const OneOfClass<Vt, N>& array)
+		{
+			return array == value;
+		}
+
+		template<typename T>
+		constexpr friend bool operator!=(const T& value, const OneOfClass<Vt, N>& array)
+		{
+			return array != value;
+		}
+	};
+};
+
+/*
+ * Returns such an object that compares equal to some value if and only if any of the parameters do.
+ * Example: (x == any(1, 2, 3)) is equivalent to (x == 1 || x == 2 || x == 3) other than the lack of lazy-evaluation
+ */
+template<typename... Ts>
+constexpr auto oneOf(Ts&&... parameters)
+{
+	using Vt = typename std::common_type<Ts...>::type;
+	return detail::OneOfClass<Vt, sizeof...(Ts)>({parameters...});
+}
+
+static_assert(oneOf(1,2,3) == 3, "oneOf unit test");
+static_assert(oneOf(1,2,3) != 5, "oneOf unit test");
+static_assert(3 == oneOf(1,2,3), "oneOf unit test");
+static_assert(5 != oneOf(1,2,3), "oneOf unit test");