// Mementos are used to roll back states arbitrarily
// A memento is simply a token/handle class with (typically) no functions of its own
// A memento is not required to expose directly the state(s) to which it reverts the system
// Can be used to implement undo/redo
public static void AdvancedDemo()
{
var ba = new BankAccountV2(100);
ba.Deposit(50);
ba.Deposit(25);
WriteLine(ba);
ba.Undo();
WriteLine($"Undo 1: {ba}");
ba.Undo();
WriteLine($"Undo 2: {ba}");
ba.Redo();
WriteLine($"Redo 2: {ba}");
}
