Question

Consider the following code: class one { public: void print() const; //Output the values of x and y protected: void setData(int u, int v); //Postcondition: x = u; y = v; private: int x; int y; }; class two: public one { public: void setData(int a, int b, int c); //Postcondition: x = a; y = b; z = c; void print() const; //Output the values of x, y, and z private: int z; }; a. Write the definition of the function setData of the class two. b. Write the definition of the function print of the class two.

Short answer

Define `setData` by invoking `one::setData(a, b)` and assigning `z = c`; define `print` by outputting `x`, `y`, and `z`.

Step-by-step solution

Understanding the Inheritance

Class `two` inherits the properties and methods of class `one`. This means that class `two` can access public and protected members of class `one`. The `setData` function in class `two` will need to set values for `x`, `y`, and `z`. Since `x` and `y` are private to class `one`, class `two` must use a public or protected method to set these values, like the `setData` function of class `one`.

Define setData in Class Two

Since the `setData` function of class `two` should set `x`, `y`, and `z`, use the protected `setData` method of class `one` to set `x` and `y`. Use direct assignment to set `z`. The definition is as follows: ```cpp void two::setData(int a, int b, int c) { one::setData(a, b); // Set x and y using the inherited setData function z = c; // Set z directly } ```

Define Print in Class Two

The `print` function in class `two` should output the values of `x`, `y`, and `z`. It will override the `print` function of class `one`. As `x` and `y` are inherited, you can directly use them along with `z`. The definition is as follows: ```cpp void two::print() const { std::cout << "x: " << x << ", y: " << y << ", z: " << z << std::endl; } ```

Combining the Implementations

The `setData` in `two` sets all three values, while `print` outputs them. This setup allows an instance of `two` to handle and display its complete state effectively, maintaining encapsulation for inherited members.

Key concepts

Object-Oriented Programming

Object-oriented programming (OOP) is a powerful paradigm used in modern programming. It centers around the concept of objects, which are instances of classes. A class can be thought of as a blueprint for creating objects, providing initial values for member variables and implementations of functions and methods.

OOP offers several advantages:

• **Encapsulation**: Bundling the data and the methods that operate on the data together, restricting the access to some of the object's components.
• **Abstraction**: Hiding the complex implementation details and showing only the necessary features of the object.
• **Inheritance**: Allowing classes to inherit properties and behaviors from other classes.
• **Polymorphism**: Enabling objects to be treated as instances of their parent class, with the ability to override methods.

This paradigm makes code more modular, easier to manage, and reusable, which is why it's widely adopted in languages like C++.

Class Inheritance

Inheritance is a fundamental concept in object-oriented programming, allowing one class to derive properties and behaviors from another. In C++, the new class (known as the "derived" class) can inherit the members of another class (the "base" class).

In the original exercise, class `two` inherits from class `one`. This means:

• Class `two` gains access to all public and protected members of class `one`.
• Class `two` can add new functions or override existing ones from class `one`.
• Member functions in `two` can directly utilize functions and data from `one`, reflecting improved code reuse and logical structuring.

Inheritance enables developers to build more flexible and scalable applications by taking advantage of already implemented functionalities in base classes.

Function Overriding

Function overriding is a key feature of polymorphism in object-oriented programming. It allows a derived class to provide a specific implementation for a function that is already defined in its base class.

In the exercise, class `two` overrides the `print` function of class `one`. When an object of the class `two` calls the `print` function, it executes the overridden version specific to `two`. Overriding ensures that the most derived version of a function is called for an object, enabling specific behavior for objects that are more specialized.

• The function signature in the derived class must match the signature in the base class to correctly override it.
• Overriding allows you to utilize polymorphism, where the same function call can result in different actions depending on the type of object it is called on.

This concept is very powerful in creating flexible code and supporting dynamic method resolution at runtime.

Access Specifiers

In C++, access specifiers define the accessibility of members of a class. They play an important role in achieving encapsulation and data protection in object-oriented programming. C++ has three main access specifiers:

• **Public**: Members declared with the public access specifier can be accessed from outside the class.
• **Protected**: Members can be accessed within the class, by derived classes, but not from external code.
• **Private**: Members are accessible only within the class itself.

In the given exercise, class `one` contains members with different access levels. `setData` is a protected member, meaning it can be accessed by derived classes like `two`, but not from outside the class hierarchy. Private members like `x` and `y` are inaccessible directly from `two`, but can be manipulated indirectly through accessible methods.

Understanding access specifiers is essential for managing class interfaces and ensuring that sensitive data is protected from unintended access.