GeeksforGeeks App
Open App
Browser
Continue

Operator overloading is a feature in object-oriented programming which allows a programmer to redefine a built-in operator to work with user-defined data types.

Let’s say we have defined a class Integer for handling operations on integers. We can have functions add(), subtract(), multiply() and divide() for handling the respective operations. However, to make the code more intuitive and enhance readability, it is preferred to use operators that correspond to the given operations(+, -, *, / respectively) i.e. we can replace the following code.
Example:

```Replace
i5 = divide(add(i1, i2), subtract(i3, i4))

by a simpler code:
i5 = (i1 + i2) / (i3 - i4) ```

The operator symbol for both prefix(++i) and postfix(i++) are the same. Hence, we need two different function definitions to distinguish between them. This is achieved by passing a dummy int parameter in the postfix version.
Here is the code to demonstrate the same.

## CPP

 `// C++ program to demonstrate``// prefix increment operator overloading` `#include ``using` `namespace` `std;` `class` `Integer {``private``:``    ``int` `i;` `public``:``    ``// Parameterised constructor``    ``Integer(``int` `i = 0)``    ``{``        ``this``->i = i;``    ``}` `    ``// Overloading the prefix operator``    ``Integer& operator++()``    ``{``        ``++i;``        ``// returned value should be a reference to *this``        ``return` `*``this``;``    ``}` `    ``// Function to display the value of i``    ``void` `display()``    ``{``        ``cout << ``"i = "` `<< i << endl;``    ``}``};` `// Driver function``int` `main()``{``    ``Integer i1(3);` `    ``cout << ``"Before increment: "``;``    ``i1.display();` `    ``// Using the pre-increment operator``    ``Integer i2 = ++i1;` `    ``cout << ``"After pre increment: "` `<< endl;``    ``cout << ``"i1: "``;``    ``i1.display();``    ``cout << ``"i2: "``; ``    ``i2.display();``}`

Output

```Before increment: i = 3
After post decrement:
i1: i = 4
i2: i = 4```

## CPP

 `// C++ program to demonstrate``// postfix increment operator``// overloading``#include ``using` `namespace` `std;` `class` `Integer {``private``:``    ``int` `i;` `public``:``    ``// Parameterised constructor``    ``Integer(``int` `i = 0)``    ``{``        ``this``->i = i;``    ``}` `    ``// Overloading the postfix operator``    ``Integer operator++(``int``)``    ``{``        ``// returned value should be a copy of the object before increment``        ``Integer temp = *``this``;``        ``++i;``        ``return` `temp;``    ``}` `    ``// Function to display the value of i``    ``void` `display()``    ``{``        ``cout << ``"i = "` `<< i << endl;``    ``}``};` `// Driver function``int` `main()``{``    ``Integer i1(3);` `    ``cout << ``"Before increment: "``;``    ``i1.display();` `    ``// Using the post-increment operator``    ``Integer i2 = i1++;` `    ``cout << ``"After post increment: "` `<< endl;``    ``cout << ``"i1: "``;``    ``i1.display();``    ``cout << ``"i2: "``; ``    ``i2.display();``}`

Output

```Before increment: i = 3
After post increment:
i1: i = 4
i2: i = 3```

Similarly, we can also overload the decrement operator as follows:

## CPP

 `// C++ program to demonstrate``// prefix decrement operator``// overloading` `#include ``using` `namespace` `std;` `class` `Integer {``private``:``    ``int` `i;` `public``:``    ``// Parameterised constructor``    ``Integer(``int` `i = 0)``    ``{``        ``this``->i = i;``    ``}` `    ``// Overloading the prefix operator``    ``Integer& operator--()``    ``{``        ``--i;``        ``// returned value should be a reference to *this``        ``return` `*``this``;``    ``}` `    ``// Function to display the value of i``    ``void` `display()``    ``{``        ``cout << ``"i = "` `<< i << endl;``    ``}``};` `// Driver function``int` `main()``{``    ``Integer i1(3);` `    ``cout << ``"Before decrement: "``;``    ``i1.display();` `    ``// Using the pre-decrement operator``    ``Integer i2 = --i1;` `    ``cout << ``"After pre decrement: "` `<< endl;``    ``cout << ``"i1: "``;``    ``i1.display();``    ``cout << ``"i2: "``; ``    ``i2.display();``}`

Output

```Before decrement: i = 3
After pre decrement:
i1: i = 2
i2: i = 2```

 `// C++ program to demonstrate``// postfix decrement operator``// overloading``#include ``using` `namespace` `std;` `class` `Integer {``private``:``    ``int` `i;` `public``:``    ``// Parameterised constructor``    ``Integer(``int` `i = 0)``    ``{``        ``this``->i = i;``    ``}` `    ``// Overloading the postfix operator``    ``Integer operator--(``int``)``    ``{``        ``// returned value should be a copy of the object before decrement``        ``Integer temp = *``this``;``        ``--i;``        ``return` `temp;``    ``}` `    ``// Function to display the value of i``    ``void` `display()``    ``{``        ``cout << ``"i = "` `<< i << endl;``    ``}``};` `// Driver function``int` `main()``{``    ``Integer i1(3);` `    ``cout << ``"Before decrement: "``;``    ``i1.display();` `    ``// Using the post-decrement operator``    ``Integer i2 = i1--;` `    ``cout << ``"After post decrement: "` `<< endl;``    ``cout << ``"i1: "``;``    ``i1.display();``    ``cout << ``"i2: "``; ``    ``i2.display();``}`
```Before decrement: i = 3