Initial commit

core-library/traits/function-traits.h

@@ -0,0 +1,61 @@
+#pragma once
+#include <concepts>
+
+namespace core {
+
+template<typename T>
+concept callable = requires { &T::operator(); };
+
+template<typename T>
+struct function_traits
+{
+	using return_type         = void;
+	using first_argument_type = void;
+};
+
+template<typename T>
+	requires callable<T>
+struct function_traits<T>
+{
+	using return_type         = typename function_traits<decltype(&T::operator())>::return_type;
+	using first_argument_type = typename function_traits<decltype(&T::operator())>::first_argument_type;
+};
+
+template<typename Ret, typename Arg0, typename... Args>
+struct function_traits<Ret(Arg0, Args...)>
+{
+	using return_type         = typename Ret;
+	using first_argument_type = typename Arg0;
+};
+
+template<typename Ret, typename Arg0, typename... Args>
+struct function_traits<Ret (*)(Arg0, Args...)>
+{
+	using return_type         = typename Ret;
+	using first_argument_type = typename Arg0;
+};
+
+template<typename Ret, typename Class, typename Arg0, typename... Args>
+struct function_traits<Ret (Class::*)(Arg0, Args...)>
+{
+	using return_type         = typename Ret;
+	using first_argument_type = typename Arg0;
+};
+
+template<typename Ret, typename Class, typename Arg0, typename... Args>
+struct function_traits<Ret (Class::*)(Arg0, Args...) const>
+{
+	using return_type         = typename Ret;
+	using first_argument_type = typename Arg0;
+};
+
+template<typename T>
+using return_type_t = typename function_traits<T>::return_type;
+
+template<typename T>
+using first_argument_type_t = typename function_traits<T>::first_argument_type;
+
+template<typename T, typename Arg>
+concept callable_with_converted_argument = requires(T&& callable, Arg&& arg) { callable(typename traits::first_argument_type_t<T>{arg}); };
+
+}