OBJECT ORIENTED PROGRAMMING AND DATA STRUCTURES

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Marvin Chapman
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1 Polymorphism: It allows a single name/operator to be associated with different operations depending on the type of data passed to it. An operation may exhibit different behaviors in different instances. Types of Polymorphism 1. Compile time polymorphism 1.1 Function Overloading 1.2 Operator Overloading 2. Run time polymorphism 2.1 Virtual Functions 1. Compile time polymorphism When the Program Compile at the time itself the compiler knows which function should be call to the object. 1.1 Function Overloading: Function Overloading means we can use the same function name and passing different arguments to that function and then perform different operation. return-type function-name 1 (argument list); return-type function-name 2 (argument list); return-type function-name 3 (argument list); M.EZHILVENDAN [AP/IT] [Jawahar Engineering College - Chennai] Page 1

2 Example: // Function Overloading #include <iostream.h> int volume(int); // cube volume int volume(int, int, int); // box volume float volume(int, int); // cylinder volume const float pi = 3.14; int main() cout << "Cube volume : " << volume(5) << "\n"; cout << "Box volume : " << volume(9, 3, 4) << "\n"; cout << "Cylinder volume : " << volume(5, 6) << "\n"; return 0; int volume(int a) return (a*a*a); int volume(int l, int b, int h) return (l * b * h); float volume(int r, int h) return (pi * r * r * h); Output: Cube volume : 125 Box volume : 10 Cylinder volume : 471 M.EZHILVENDAN [AP/IT] [Jawahar Engineering College - Chennai] Page 2

3 OPERATOR OVERLOADING Operator overloading is a way of defining additional task to an existing operator so that it could be applied to user-defined types. An operator's semantic can be extended but its syntax cannot be altered. Overloading is done with the help of a special operator function. Return-type class-name :: operator op(arguments) Operators that cannot be overloaded are. ::?: sizeof.* Friend function cannot be used for operators = () [] -> Types of Operator Overloading: 1. Overloading Unary Operators 2. Overloading Binary Operators 1. Overloading Unary Operators: Unary operator overloaded using member function takes no arguments and return type is void One operant and One operator to be involved and it should be directly communicated to object Operator : -,++,-- returntype classname :: operator op(no arguments) M.EZHILVENDAN [AP/IT] [Jawahar Engineering College - Chennai] Page 3

4 Example : // Overloading Unary Operators #include<iostream.h> #include<conio.h> class space int x,y,z; public: void getdata() cout<<"enter the values\n"; cin>>x>>y>>z; void display() cout<<x<<" "; cout<<y<<" "; cout<<z<<" "; void operator-() x=-x; y=-y; z=-z; ; void main() clrscr(); space s; s.getdata(); cout<<"s:"; s.display(); -s; cout<<"\ns:"; s.display(); getch(); M.EZHILVENDAN [AP/IT] [Jawahar Engineering College - Chennai] Page 4

5 Output: Enter the values S:1-2 3 S: Overloading Binary Operators: Binary operators overloaded using member function takes a user-defined argument and do return. The left operand is passed implicitly to the operator function and only the right operand is explicitly passed. One operator and two Operant to be involved and it should be directly communicated to object Operator : +, *, / returntype classname :: operator op(one arguments) Example: //Binary Operator Overloading #include<iostream.h> #include<conio.h> class complex float x; float y; public: complex() complex(float real,float imag) x=real; y=imag; M.EZHILVENDAN [AP/IT] [Jawahar Engineering College - Chennai] Page 5

6 complex operator+(complex c); void display(void); ; complex complex::operator+(complex c) complex temp; temp.x=x+c.x; temp.y=y+c.y; return (temp); void complex :: display(void) cout<<x<<"+j"<<y<<"\n"; void main() complex C1,C2,C3; C1=complex(2.5,3.5); C2=complex(1.6,2.7); C3=C1+C2; clrscr(); cout<<"c1 ="; C1.display(); cout<<"c2 ="; C2.display(); cout<<"c3 ="; C3.display(); getch(); Output: C1=2.5+j3.5 C2=1.6+J2.7 C3=4.1+J6.2 Operator Overloading Rules 1. Only existing operators can be overloaded. 2. The overloaded operator must have at least one operand of user-defined type. 3. Overloaded operators follow the syntax of original operators 4. For unary operators there is no return and for binary operators a class type is returned 5. Operators that cannot be overloaded are. ::?: sizeof.* 6. Friend function cannot be used for operators = () [] -> M.EZHILVENDAN [AP/IT] [Jawahar Engineering College - Chennai] Page 6

7 2. Run time polymorphism The Compiler do not having any knowledge about which function should be call to object, so it should be decided at the run time itself this known as Run time Polymorphism 2.1 Virtual Function: When the form of a member function is changed at run time that member function is referred to as virtual function. Virtual Function-Name ( ); Example: // Virtual Function #include<iostream.h> #include<conio.h> class base public: void display() cout<<"\n display base"; virtual void show() ; cout<<"\n show base"; //Virtual Function Defined M.EZHILVENDAN [AP/IT] [Jawahar Engineering College - Chennai] Page 7

8 class derived:public base public: void display() cout<<"\n display derived"; void show() cout<<"\n show derived"; ; void main() base b; derived d; base *bptr; clrscr(); cout<<"\n bptr points to base:"; bptr=&b; bptr->display(); bptr->show(); cout<<"\n bptr points to derived:"; bptr=&d; bptr->display(); bptr->show(); getch(); Output bptr points to base: display base show base bptr points to derived: display base show derived M.EZHILVENDAN [AP/IT] [Jawahar Engineering College - Chennai] Page 8

Data type of a pointer must be same as the data type of the variable to which the pointer variable is pointing. Here are a few examples:

Data type of a pointer must be same as the data type of the variable to which the pointer variable is pointing. Here are a few examples: Unit IV Pointers and Polymorphism in C++ Concepts of Pointer: A pointer is a variable that holds a memory address of another variable where a value lives. A pointer is declared using the * operator before