diff --git a/octa/memory.hh b/octa/memory.hh
index 9e447ea..9f07d8e 100644
--- a/octa/memory.hh
+++ b/octa/memory.hh
@@ -1068,10 +1068,51 @@ inline AllocatorType<A> allocator_container_copy(const A &a) {
     >(), a);
 }
 
+/* allocator arg */
+
 struct AllocatorArg {};
 
 constexpr AllocatorArg allocator_arg = AllocatorArg();
 
+/* uses allocator */
+
+namespace detail {
+    template<typename T> struct HasAllocatorType {
+        template<typename U> static char test(typename U::Allocator *);
+        template<typename U> static  int test(...);
+        static constexpr bool value = (sizeof(test<T>(0)) == 1);
+    };
+
+    template<typename T, typename A, bool = HasAllocatorType<T>::value>
+    struct UsesAllocatorBase: IntegralConstant<bool,
+        IsConvertible<A, typename T::Allocator>::value
+    > {};
+
+    template<typename T, typename A>
+    struct UsesAllocatorBase<T, A, false>: False {};
+}
+
+template<typename T, typename A>
+struct UsesAllocator: detail::UsesAllocatorBase<T, A> {};
+
+/* uses allocator ctor */
+
+namespace detail {
+    template<typename T, typename A, typename ...Args>
+    struct UsesAllocCtor {
+        static constexpr bool ua = UsesAllocator<T, A>::value;
+        static constexpr bool ic = IsConstructible<
+            T, AllocatorArg, A, Args...
+        >::value;
+        static constexpr int value = ua ? (2 - ic) : 0;
+    };
+}
+
+template<typename T, typename A, typename ...Args>
+struct UsesAllocatorConstructor: IntegralConstant<int,
+    detail::UsesAllocCtor<T, A, Args...>::value
+> {};
+
 } /* namespace octa */
 
 #endif
\ No newline at end of file