diff --git a/impl_queue_array.go b/impl_queue_array.go
index de1a399..ed6f605 100644
--- a/impl_queue_array.go
+++ b/impl_queue_array.go
@@ -1,8 +1,13 @@
 package ds
 
-type ArrayQueue[T any] ListQueue[T]
+type ArrayQueue[T any] struct {
+	*ListQueue[T]
+}
+
+var _ Queue[int] = &ArrayQueue[int]{}
 
 func NewArrayQueue[T any]() *ArrayQueue[T] {
-	stack := NewListQueue[T](new(ArrayList[T]))
-	return (*ArrayQueue[T])(stack)
+	return &ArrayQueue[T]{
+		ListQueue: NewListQueue[T](NewArrayList[T](0)),
+	}
 }
diff --git a/impl_queue_linked_list.go b/impl_queue_linked_list.go
index e500260..9fbb5fa 100644
--- a/impl_queue_linked_list.go
+++ b/impl_queue_linked_list.go
@@ -1,8 +1,13 @@
 package ds
 
-type LinkedListQueue[T any] ListQueue[T]
+type LinkedListQueue[T any] struct {
+	*ListQueue[T]
+}
+
+var _ Queue[int] = &LinkedListQueue[int]{}
 
 func NewLinkedListQueue[T any]() *LinkedListQueue[T] {
-	stack := NewListQueue[T](new(LinkedList[T]))
-	return (*LinkedListQueue[T])(stack)
+	return &LinkedListQueue[T]{
+		ListQueue: NewListQueue[T](NewLinkedList[T]()),
+	}
 }
diff --git a/impl_stack_array.go b/impl_stack_array.go
index 13fbd2a..bdc7745 100644
--- a/impl_stack_array.go
+++ b/impl_stack_array.go
@@ -1,8 +1,13 @@
 package ds
 
-type ArrayStack[T any] ListStack[T]
+type ArrayStack[T any] struct {
+	*ListStack[T]
+}
+
+var _ Stack[int] = &ArrayStack[int]{}
 
 func NewArrayStack[T any]() *ArrayStack[T] {
-	stack := NewListStack[T](new(ArrayList[T]))
-	return (*ArrayStack[T])(stack)
+	return &ArrayStack[T]{
+		ListStack: NewListStack[T](NewArrayList[T](0)),
+	}
 }
diff --git a/impl_stack_linked_list.go b/impl_stack_linked_list.go
index 46698a9..cfbe572 100644
--- a/impl_stack_linked_list.go
+++ b/impl_stack_linked_list.go
@@ -1,8 +1,13 @@
 package ds
 
-type LinkedListStack[T any] ListStack[T]
-
-func NewLinkedListStack[T any]() *ArrayStack[T] {
-	stack := NewListStack[T](new(LinkedList[T]))
-	return (*ArrayStack[T])(stack)
+type LinkedListStack[T any] struct {
+	*ListStack[T]
+}
+
+var _ Stack[int] = &LinkedListStack[int]{}
+
+func NewLinkedListStack[T any]() *LinkedListStack[T] {
+	return &LinkedListStack[T]{
+		ListStack: NewListStack[T](NewLinkedList[T]()),
+	}
 }
diff --git a/int_map.go b/int_map.go
index 0ffdd02..85ad324 100644
--- a/int_map.go
+++ b/int_map.go
@@ -1 +1,2 @@
+package ds
 // TODO
\ No newline at end of file
diff --git a/int_tree.go b/int_tree.go
index 0ffdd02..85ad324 100644
--- a/int_tree.go
+++ b/int_tree.go
@@ -1 +1,2 @@
+package ds
 // TODO
\ No newline at end of file