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C++ program to overload unary pre-increment operator

Learn: How to overload a unary pre-increment operator in C++? This post contains program on it with the example and explanation.

Read: operator overloading and its rules

Overloading unary pre-increment operator

Here, we are implementing/defining unary pre-increment operator overloading in C++ programming, to define it: use operator keyboard as function name and then write operator symbol.

Syntax

return_type operator++(function_argument)
{
  //body
}

C++ program to overload unary pre-increment operator

using namespace std;
#include <iostream>

class Sample {
  // private data member
 private:
  int count;

 public:
  // default constructor
  Sample() { count = 0; }
  // parameterized constructor
  Sample(int c) { count = c; }

  // operator overloading
  void operator++() { ++count; }

  // printing the value
  void printValue() { cout << "Value of count : " << count << endl; }
};

// main program
int main() {
  int i = 0;
  // object creation
  Sample S1(10);

  for (i = 0; i < 10; i++) {
    // Incrementing object
    ++S1;
    // S1++; //Error
    S1.printValue();
  }

  return 0;
}

Output

Value of count : 11
Value of count : 12
Value of count : 13
Value of count : 14
Value of count : 15
Value of count : 16
Value of count : 17
Value of count : 18
Value of count : 19
Value of count : 20

Explanation

In this program, we have created a class named Sample. It contains a data member value. And we have implemented a function to overload pre-increment operator.

We cannot use post-increment with this method of operator overloading.

++S1 is the statement which is calling the pre-incremented overloaded operator, which will increase the value of private data member (value) .

We can use below statement also in place of ++S1: S1.operator++();