1. Operator Overloading

2. Outline Revision What is Operator Overloading Why Operator Overloading
Overloading Unary operators
Overloading Binary operators
Overloading Assignment operator

3. Revision
Operator Overloading is a mechanism to redefine built-in operations for user defined types
It allows to give normal C++ operators such as +,-,==,< additional meanings
Operator Overloading should be used to perform the same function or similar function on class objects as the built-in behavior

4. Revision
Operator overloading is a very neat feature of object oriented programming in C++
Each individual operator must be overloaded for use with user defined types
Overloading the assignment operator and the subtraction operator does not overload the -= operator.

5. Things to keep in mind
At least one of the operands in any overloaded operator must be a user-defined type
operator + for one integer and one double, NOT possible
Can only overload the operators that exist.
All operators keep their current precedence and associativity, regardless of what they're used for

6. Operator Functions
Operator functions may be defined as either member functions or as non-member functions.
Non-member functions are usually made friends for performance reasons.
Member functions usually use the this pointer implicitly.

7. Commonly Overloaded Operators
Unary
++, --, (increment, decrement)
Binary
+, -, *, /, % (arithmetic)
=, +=, -=, *=, /=, %= (assignment)
==, !=, >, <, >=, <= (relational)
<<, >> (I/O)
||, && (logical)
&, |, ^, ^=, &=, |= (bitwise)

8. Non-overloadable Operators
. (dot operator / member selector)
:: (scope resolution operator)
?: (conditional operator / arithematic if)
.* (member pointer selector)
sizeof

9. Overloading Unary Operator
Increment Operators ( ++)
Unary Operators ( --)

10. Example #include <iostream> using namespace std;
////////////////////////////////////////////////////////////////
class Counter {
private:
unsigned int count; //count
public:
Counter() : count(0) //constructor
{ }
unsigned int get_count() //return count
{ return count; }
void operator ++ () //increment (prefix)
++count; } };

11. int main() {
Counter c1, c2; //define and initialize
cout << “\nc1=” << c1.get_count(); //display
cout << “\nc2=” << c2.get_count();
++c1; //increment c1
++c2; //increment c2
cout << “\nc1=” << c1.get_count(); //display again
cout << “\nc2=” << c2.get_count() << endl;
return 0; }

12. Overloading Binary Operators
Arithmetic Operators
Assignment Operators
Comparison Operators
Arithmetic Assignment Operators