diff --git a/code/rust/src/stacks/stack.rs b/code/rust/src/stacks/stack.rs
index a71a5a2..893f47e 100644
--- a/code/rust/src/stacks/stack.rs
+++ b/code/rust/src/stacks/stack.rs
@@ -18,7 +18,7 @@ pub struct Stack<T> {
 }
 
 impl<T> Stack<T>
-where T: Clone + ToString {
+where T: Clone + ToString + Eq {
     /// Creates new typed instance of stack.
     pub fn new() -> Stack<T> {
         return Stack {
@@ -53,6 +53,11 @@ where T: Clone + ToString {
         return element;
     }
 
+    /// checks if element in stack:
+    pub fn contains(self: &Self, element: &T) -> bool {
+        return self.elements.contains(element);
+    }
+
     /// convert entries to strings
     #[allow(dead_code)]
     fn repr(self: &Self) -> Vec<String> {