Editing Operator overloading (section)

==Examples==
In this case, the addition operator is overloaded to allow addition on a user-defined type {{code|Time}} in [[C++]]:

<syntaxhighlight lang=Cpp>
Time operator+(const Time& lhs, const Time& rhs) {
  Time temp = lhs;
  temp.seconds += rhs.seconds;
  temp.minutes += temp.seconds / 60;
  temp.seconds %= 60;
  temp.minutes += rhs.minutes;
  temp.hours += temp.minutes / 60;
  temp.minutes %= 60;
  temp.hours += rhs.hours;
  return temp;
}
</syntaxhighlight>

Addition is a [[binary operation]], which means it has two [[operand]]s. In C++, the arguments being passed are the operands, and the {{code|temp}} object is the returned value.

The operation could also be defined as a class method, replacing {{code|lhs}} by the hidden {{code|this}} argument; However, this forces the left operand to be of type {{code|Time}}:

<syntaxhighlight lang=Cpp>
// The "const" right before the opening curly brace means that |this| is not modified.
Time Time::operator+(const Time& rhs) const {
  Time temp = *this;  // |this| should not be modified, so make a copy.
  temp.seconds += rhs.seconds;
  temp.minutes += temp.seconds / 60;
  temp.seconds %= 60;
  temp.minutes += rhs.minutes;
  temp.hours += temp.minutes / 60;
  temp.minutes %= 60;
  temp.hours += rhs.hours;
  return temp;
}
</syntaxhighlight>

Note that a [[Unary operation|unary]] operator defined as a class method would receive no apparent argument (it only works from {{code|this}}):

<syntaxhighlight lang=Cpp>
bool Time::operator!() const {
  return hours == 0 && minutes == 0 && seconds == 0;
}
</syntaxhighlight>

The less-than (<) operator is often overloaded to sort a structure or class:

<syntaxhighlight lang=Cpp>
class Pair {
 public:
  bool operator<(const Pair& p) const {
    if (x_ == p.x_) {
      return y_ < p.y_;
    }
    return x_ < p.x_;
  }

 private:
  int x_;
  int y_;
};
</syntaxhighlight>

Like with the previous examples, in the last example operator overloading is done within the class. In C++, after overloading the less-than operator (<), [[sort (C++)|standard sorting functions]] can be used to sort some classes.