$4\mathrm{.}26$ LAB: Grocery list editor with undo stack

In this lab a grocery list editor with undo functionality is implemented.

Step $1$: Inspect the UndoCommand abstract base class

The read$-$only UndoCommand. py file has a declaration for the UndoCommand abstract base class. Ac on the orange arrow next to

main.py at the top of the coding window. The UndoCommand class repres that stores all needed information to execute an action at a later point in time. For this lab, a command grocery list change made by the user.

Step $2$: Inspect the incomplete GroceryList class

The GroceryList class is declared in

GroceryList.py$.$ Two attributes are declared:

A list of strings for list items

A stack of UndoCommand references for undo commands

A simple list implementation of stack ADT is provided in

Stack.py$.$

Note that the add$\_$with$\_$undo$()$ method is already implemented. The method adds a new item to the list a RemoveLastCommand object onto the undo stack.