# Structs
Book is a concrete implementation of Element for books.
Circle is a concrete implementation of Shape for circles.
ConcreteElementA is a concrete implementation of Element for element A.
ConcreteElementB is another concrete implementation of Element for element B.
ConcreteVisitor1 is a concrete implementation of Visitor.
ConcreteVisitor2 is another concrete implementation of Visitor.
Fruit is another concrete implementation of Element for fruits.
ObjectsStructure is the structure holding a collection of shapes.
Rectangle is another concrete implementation of Shape for rectangles.
SaleDiscount is another concrete implementation of Visitor for sale discounts.
ShoppingCart is the structure holding a list of items.
SundayDiscount is a concrete implementation of Visitor for Sunday discounts.
TextVisitor is another concrete implementation of Visitor for generating text representation.
XMLVisitor is a concrete implementation of Visitor for generating XML representation.
# Interfaces
Element is the abstract class defining the accept method.
Element is the abstract class defining the accept method.
Shape is the abstract class defining the accept method.
Visitor is the abstract class defining the visit methods.
Visitor is the abstract class defining the visit methods.
Visitor is the abstract class defining the visit methods.