Constructors

Constructors

A constructor is a special member function that runs automatically when an object is created. It has the same name as the class and no return type.

Default Constructor

A constructor with no parameters:

class Counter {
public:
    int count;

    Counter() {
        count = 0;
        cout << "Counter created" << endl;
    }
};

Counter c;  // "Counter created" is printed

Parameterized Constructor

A constructor that takes arguments lets you initialize the object with specific values:

class Point {
public:
    int x;
    int y;

    Point(int x, int y) {
        this->x = x;  // this-> distinguishes parameter from member
        this->y = y;
    }
};

Point p(3, 4);
cout << p.x << " " << p.y << endl;  // 3 4

this Pointer

Inside a member function, this is a pointer to the current object. It's useful when parameter names shadow member names.

Default Parameters

Instead of writing multiple constructors, you can use default parameter values to handle both cases with a single constructor:

class Point {
public:
    int x, y;

    Point(int px = 0, int py = 0) {
        x = px;
        y = py;
        if (px == 0 && py == 0) {
            cout << "Point at origin" << endl;
        } else {
            cout << "Point at (" << px << ", " << py << ")" << endl;
        }
    }

    void print() {
        cout << "(" << x << ", " << y << ")" << endl;
    }
};

Point p1;       // Point at origin
Point p2(3, 4); // Point at (3, 4)
p1.print();     // (0, 0)
p2.print();     // (3, 4)

Member Initializer Lists

A cleaner way to initialize members — runs before the constructor body:

class Point {
public:
    int x, y;
    Point(int x, int y) : x(x), y(y) {}
};

Your Task

Create a Point class with a constructor that uses default parameters (defaulting to 0). If both values are 0, print "Point at origin"; otherwise print "Point at (x, y)". Add a print() method that prints "(x, y)".