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Operator Overloading

• There are actually two forms of the ++ and -- operators.
  • A prefix form:

    ++x;
    

  • A postfix form:

    x++;
    

• Recall that ++x evaluates to x after the increment, and x++ evaluates to x before the increment.

  int i = 0;
  int j = 0;
  vector<double> s(10);
  double a = s[i++]; /* a is s[0], i is 1 */
  double b = s[++j]; /* b is s[1], j is 1 */
  

• In order for the compiler to distinguish between the two versions, the operators must have two different parameter lists.

  void operator++(Time& a) /* prefix operator */
  . . .
  
  
  void operator++(Time& a, int dummy) /* postfix operator */
  

• The int dummy parameter is not used inside the function, it merely serves to differentiate the two operator++ functions.

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