...

cxx/mcc_traits.h

@@ -145,6 +145,19 @@ template <typename T, typename... CtorArgTs>
 concept mcc_output_arg_c = !std::is_const_v<std::remove_reference_t<T>> && std::is_lvalue_reference_v<T> &&
                            std::constructible_from<std::remove_reference_t<T>, CtorArgTs...>;
 
+
+
+// std::tuple or std::pair
+template <typename T>
+concept mcc_tuple_c = requires {
+    requires requires {
+        []<typename... Ts>(std::type_identity<std::tuple<Ts...>>) {}(std::type_identity<std::remove_cvref_t<T>>());
+    } || requires {
+        []<typename T1, typename T2>(std::type_identity<std::pair<T1, T2>>) {
+        }(std::type_identity<std::remove_cvref_t<T>>());
+    };
+};
+
 namespace details
 {