Question

Consider the definition of the following class: class CC { public : CC(); //Line 1 CC(int); //Line 2 CC(int, int); //Line 3 CC(double, int); //Line 4 . . . private: int u; double v; }; a. Give the line number containing the constructor that is executed in each of the following declarations. i. CC one; ii. CC two(5, 6); iii. CC three(3.5, 8); b. Write the definition of the constructor in Line 1 so that the private member variables are initialized to 0. c. Write the definition of the constructor in Line 2 so that the private member variable u is initialized according to the value of the parameter, and the private member variable v is initialized to 0. d. Write the definition of the constructors in Lines 3 and 4 so that the private member variables are initialized according to the values of the parameters.

Short answer

(i) Line 1; (ii) Line 3; (iii) Line 4.

Step-by-step solution

Identify Constructors for Declarations

For the statement `CC one;`, the default constructor on Line 1 is used since no parameters are passed. For `CC two(5, 6);`, the constructor on Line 3 is used since it matches two integer parameters `(int, int)`. For `CC three(3.5, 8);`, the constructor on Line 4 is selected since it matches the parameters `(double, int)`.

Define the Constructor on Line 1

The constructor on Line 1 is defined to initialize both member variables to 0: ```cpp CC::CC() : u(0), v(0.0) {} ```

Define the Constructor on Line 2

The constructor on Line 2 is defined to initialize `u` using the parameter and `v` to 0.0: ```cpp CC::CC(int param_u) : u(param_u), v(0.0) {} ```

Define the Constructor on Line 3

The constructor on Line 3 initializes `u` and `v` with the passed parameters: ```cpp CC::CC(int param_u, int param_v) : u(param_u), v(static_cast(param_v)) {} ```

Define the Constructor on Line 4

The constructor on Line 4 initializes `u` and `v` directly from the parameters provided: ```cpp CC::CC(double param_v, int param_u) : v(param_v), u(param_u) {} ```

Key concepts

Class Definition

In C++, a class is a blueprint for creating objects. It defines a data type by bundling data and methods that work on the data into a single unit. This concept of encapsulation is fundamental to object-oriented programming. A class typically consists of both public and private members. Public members can be accessed from outside the class, while private members are only accessible within the class itself.

In the given exercise, the class `CC` is defined with both public and private sections. The public section contains constructors, which allow for initializing the objects, while the private section includes two data members, `int u` and `double v`, which store the internal state of the object. The class keyword followed by a class name and braces is the typical syntax for defining a class.

Constructor Overloading

Constructor overloading is a feature in C++ that allows multiple constructors to be defined in a class, each having different parameter lists. This enables objects of a class to be initialized in multiple ways. The compiler differentiates between these constructors by the number and types of their parameters.

In the class `CC`, constructor overloading is utilized with four different constructors. Each is designed to handle different initialization scenarios. For example, `CC()` is a default constructor with no parameters, while `CC(int)` accepts one integer parameter. Another constructor `CC(int, int)` caters to two integer parameters, and finally, `CC(double, int)` manages a double and an integer parameter. This flexibility allows users to create objects according to their specific needs.

Member Initialization

Member initialization is an efficient way to initialize variables in a constructor using an initialization list. This approach not only simplifies the constructor body but also improves performance by directly initializing members rather than assigning them later.

In C++, you define an initialization list after the constructor name, preceding the constructor body with a colon. For instance, `CC::CC() : u(0), v(0.0) {}` initializes `u` and `v` to 0 right when an object is constructed, which is often better practice than assigning values within the constructor body. This pattern is reflected in all the constructors provided for the class `CC` from the exercise, ensuring that member variables are appropriately initialized according to the passed parameters.

Default Constructor

The default constructor is a special type of constructor that can be invoked without any arguments. It is typically used to initialize data members to default or zero values, ensuring that the object starts in a known state.

In the `CC` class, the default constructor `CC::CC() : u(0), v(0.0) {}` is specifically set to initialize the member variables `u` and `v` to zero. In scenarios where no explicit values are provided at object creation, the default constructor plays a crucial role by automatically setting sensible initial values. Such constructors are especially useful in scenarios where an object needs to be declared but the actual values will be assigned later during program execution.