Operator Overloading - Examples

Examples

In this case, the addition operator is overloaded to allow addition on a user-defined type "Time" (in C++):

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; }

Addition is a binary operation, which means it has left and right operands. In C++, the arguments being passed are the operands, and the temp object is the returned value.

The operation could also be defined as a class method, replacing lhs by the hidden this argument; however this forces the left operand to be of type Time and supposes this to be a potentially modifiable lvalue:

Time Time::operator+(const Time& rhs) const { const Time temp = *this; /* Copy 'this' which is not to be modified */ 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; }

Note that a unary operator defined as a class method would receive no apparent argument (it only works from this):

bool Time::operator! const { return ((hours == 0) && (minutes == 0) && (seconds == 0)); }