Question

im not sure if i understand correctly how this class works. its an example of stack.

ref class Stack
{
   private:

      ref struct Item // Defines items to store in the stack
      {
         Object^ Obj; // Handle for the object in this item
         Item^ Next; // Handle for next item in the stack or nullptr

         Item(Object^ obj, Item^ next): Obj(obj), Next(next){} // Constructor
      };

      Item^ Top; // Handle for item that is at the top

   public:

      void Push(Object^ obj) // Push an object onto the stack
      {
         Top = gcnew Item(obj, Top); // Create new item and make it the top
      }

      Object^ Pop() // Pop an object off the stack
      {
         if(Top == nullptr) // If the stack is empty
         return nullptr; // return nullptr
         Object^ obj = Top->Obj; // Get object from item
         Top = Top->Next; // Make next item the top
         return obj;
      }
};

i cant figure out how exactly Push function works. in the class definition its Top=gcnew Item(obj, Top)so basically it says that Top equals Next. So how does the Stack class determine the Next item if its always the one on the top of the stack?

Answer 1

I think you misinterpret the line:

     Top = gcnew Item(obj, Top);

It means:

• make the new item the top of the stack (which is ultimately what you want for a stack)
• set Next of the new Item to what was previously the Top

so by calling Top->Next you get to the previous item (the one “underneath” Top)