Unary Operators Overloading in C++

The unary operators operate on a single operand and following are the examples of Unary operators −

• The increment (++) and decrement (--) operators.
• The unary minus (-) operator.
• The logical not (!) operator.

The unary operators operate on the object for which they were called and normally, this operator appears on the left side of the object, as in !obj, -obj, and ++obj but sometime they can be used as postfix as well like obj++ or obj--.

Following example explain how minus (-) operator can be overloaded for prefix as well as postfix usage.

#include <iostream>
using namespace std;
 
class Distance {
   private:
      int feet;             // 0 to infinite
      int inches;           // 0 to 12
      
   public:
      // required constructors
      Distance() {
         feet = 0;
         inches = 0;
      }
      Distance(int f, int i) {
         feet = f;
         inches = i;
      }
      
      // method to display distance
      void displayDistance() {
         cout << "F: " << feet << " I:" << inches <<endl;
      }
      
      // overloaded minus (-) operator
      Distance operator- () {
         feet = -feet;
         inches = -inches;
         return Distance(feet, inches);
      }
};

int main() {
   Distance D1(11, 10), D2(-5, 11);
 
   -D1;                     // apply negation
   D1.displayDistance();    // display D1

   -D2;                     // apply negation
   D2.displayDistance();    // display D2

   return 0;
}

When the above code is compiled and executed, it produces the following result −

F: -11 I:-10
F: 5 I:-11

Hope above example makes your concept clear and you can apply similar concept to overload Logical Not Operators (!).