fixes

include/util/function.hpp

@@ -0,0 +1,63 @@
+#pragma once
+
+#include <tuple>
+#include <concepts>
+
+namespace ztu {
+
+	template<typename F, typename R, typename... Args>
+	concept callable = std::same_as<std::invoke_result_t<F, Args...>, R>;
+
+	template<typename T>
+	concept runnable = callable<T, void>;
+
+	template<typename T, typename R>
+	concept supplier = callable<T, R>;
+
+	template<typename T, typename... Args>
+	concept consumer = callable<T, void, Args...>;
+
+	template<typename T, typename... Args>
+	concept predicate = callable<T, bool, Args...>;
+
+
+	template<typename>
+	struct function_meta;
+
+	template<typename R, typename... Args>
+	struct function_meta<R(*)(Args...)> {
+		using ret_t = R;
+		using args_t = std::tuple<Args...>;
+		static constexpr bool is_const = false;
+	};
+
+	template<class C, typename R, typename... Args>
+	struct function_meta<R(C::*)(Args...)> {
+		using class_t = C;
+		using ret_t = R;
+		using args_t = std::tuple<Args...>;
+		static constexpr bool is_const = false;
+	};
+
+	template<class C, typename R, typename... Args>
+	struct function_meta<R(C::*)(Args...) const> {
+		using class_t = C;
+		using ret_t = R;
+		using args_t = std::tuple<Args...>;
+		static constexpr bool is_const = true;
+	};
+
+	namespace function {
+		template<typename F>
+		using class_t = typename function_meta<F>::class_t;
+
+		template<typename F>
+		using ret_t = typename function_meta<F>::ret_t;
+
+		template<typename F>
+		using args_t = typename function_meta<F>::args_t;
+
+		template<typename F>
+		constexpr bool is_const_v = function_meta<F>::is_const;
+	}
+}