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OPERATOR OVERLOADING
Customised behaviour of operators
Introduction
Operator overloading Use traditional operators with user-defined
objects Straightforward and natural way to extend
C++ Requires great care
When overloading misused, program difficult to understand
Fundamentals of Operator Overloading Use operator overloading to improve
readability Avoid excessive or inconsistent usage
Format Write function definition as normal Function name is keyword operator
followed by the symbol for the operator being overloaded.
operator+ would be used to overload the addition operator (+)
Restrictions on Operator Overloading
Most of C++’s operators can be overloaded
Operators that can be overloaded
+ - * / % ^ & |
~ ! = < > += -= *=
/= %= ^= &= |= << >> >>=
<<= == != <= >= && || ++
-- ->* , -> [] () new delete
new[] delete[]
Restrictions on Operator Overloading (II)
Arity (number of operands) cannot be changed Urnary operators remain urnary, and binary
operators remain binary Operators *, + and - each have unary and
binary versions Unary and binary versions can be overloaded
separately
Restrictions on Operator Overloading (III)
No new operators can be created Use only existing operators
Built-in types Cannot overload operators You cannot change how two integers are
added
Coding Practices
Example: Operator Overloadingclass OverloadingExample
{ private:
int m_LocalInt;
public:
OverloadingExample(int j) // default constructor
{
m_LocalInt = j;
}
int operator+ (int j) // overloaded + operator
{
return (m_LocalInt + j);
}
};
Example: Operator Overloading (contd.)
void main()
{
OverloadingExample object1(10);
cout << object1 + 10;
}
Types of Operator
Unary operator Binary operator
Unary Operators
Operators attached to a single operand (-a, +a, --a, a--, ++a, a++)
Example: Unary Operators
class UnaryExample
{
private:
int m_LocalInt;
public:
UnaryExample(int j)
{
m_LocalInt = j;
}
int operator++ ()
{
return (m_LocalInt++);
}
};
Example: Unary Operators (contd.)
void main()
{
UnaryExample object1(10);
cout << object1++;
}
Prefix and Postfix Notation
int operator++ () // Prefix{ return (++m_LocalInt);}
int operator++ (int) // postfix{ return (m_LocalInt++);}Only difference is the int in the parenthesis
Binary Operators
Operators attached to two operands a+b, a-b, a*b etc.)
Example: Unary Operators
class UnaryExample
{
private:
int m_LocalInt;
public:
UnaryExample(int j)
{
m_LocalInt = j;
}
int operator++ ()
{
return (m_LocalInt++);
}
};
Binary Operators
Operators attached to two operands (a-b, a+b, a*b, a/b, a%b, a>b, a>=b, a<b, a<=b, a==b)
Example: Binary Operators
class BinaryExample
{
private:
int m_LocalInt;
public:
BinaryExample(int j)
{
m_LocalInt = j;
}
int operator+ (BinaryExample rhsObj)
{
return (m_LocalInt + rhsObj.m_LocalInt);
}
};
Example: Binary Operators (contd.)
void main()
{
BinaryExample object1(10), object2(20);
cout << object1 + object2;
}
Another Way of Doing it!
How to solve object1 + object2 +object3+……?
class BinaryExampleU{ private:
int m_LocalInt; public: BinaryExampleU(int j)
{ m_LocalInt = j;
}BinaryExampleU operator+ (BinaryExampleU rhsObj){ return BinaryExampleU(m_LocalInt +
rhsObj.m_LocalInt);}
void print() {
cout<<m_LocalInt; }};
void main(){ BinaryExampleU object1(10),
object2(20), object3 (30), object4(0); object4 = object1 + object2 +object3 ;
object4.print();}
Case Study: An Array class
Implement an Array class with Range checking Array assignment Arrays that know their size Outputting/inputting entire arrays with <<
and >> Array comparisons with == and !=
Thankyou
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