OPERATOR OVERLOADING Introduction Rules Types Programs Introduction Allows

OPERATOR OVERLOADING Introduction Rules Types Programs

Introduction Allows us to define the behavior of operators when applied to objects of a class � Operator Overloading does not allow us to alter the meaning of operators when applied to built-in types ◦ Example: 2+3 addition, 2*3 multiplication By operator overloading, we can apply the operators to our own abstract data type like this ◦ Example; Class A{ main() int a, b; { public: A obj 1(2, 3); A(int x, int y){a=x; b=y; } -obj 1; }; }

To Overload an Operator � Steps � Overloading an operator �Write function definition as normal �Function name : operator keyword followed by the symbol �Operator+ () � Applying operators on objects ◦ Create objects for the class ◦ Apply the operator on objects �object 1 + object 2 �-object 1

Rules to Overload an operator � Rules ◦ Precedence of an operator cannot be changed ◦ Associativity of an operator cannot be changed ◦ Arity (number of operands) cannot be changed ◦ No new operators can be created ( Ex: +-) �Use only existing operators ◦ No overloading operators for built-in types �Cannot change how two integers are added ◦ Produces a syntax error (Ex; 2+3) Operator functions can be member or nonmember functions

Rules to Overloade an operator � C++ operators that can be overloaded � C++ Operators that cannot be overloaded

Types � Syntax Return type class name : : operator symbol(args){ } Using Member Function � Unary Operator Overloading Ex: A operator –() ( ) � Binary Operator Overloading Ex: A operator –(A object) ( ) Using Non Member Function (use Friend Keyword) � Unary Operator Overloading Ex: A operator –(A object) ( ) � Binary Operator Overloading Ex: A operator –(A object 1, A object 2) ( )

Unary operator : Member Function class A { int inches, feet; public: A(int x, int y) { inches=x; feet=y; } void display() { cout <<"n"<<inches<<" "<<feet; } void operator-() { inches=-inches; feet=-feet; } }; int main() { A obj 1(20, 10); obj 1. display(); -obj 1; obj 1. display(); }

Binary operator Using Member Function class A { int a, b; public: A(int x, int y) { a=x; b=y; } void display() { cout <<"n"<<inches<<" "<<feet; } void operator+(A o 1); }; Void A : : operator +(A o 1) { a=a+o 1. a; b=b+o 1. b; }

int main() { A obj 1(20, 10); A. obj 2(10, 20); obj 1+obj 2; obj 1. display(); }

Unary operator : Non Member Function class A { int a, b public: A() { a=b=0; } A(int x, int y) { a=x; b =y; } void display() { cout <<"n"<<a<<" "<<b; } friend A operator-(A) }; A operator-(A d 1) { A d 2; d 2. a=-d 1. a; d 2. b=-d 1. b; return d 2; }

int main() { A obj 1(20, 10); obj 1. display(); A C; C=-obj 1; C. display(); }

Unary operator : Non Member Function class A { int a, b public: A() { a=b=0; } A(int x, int y) { a=x; b =y; } void display() { cout <<"n"<<a<<" "<<b; } friend A operator+(A, A) }; A operator+(A d 1, A d 2) { A d 3; d 3. a=-d 1. a+d 2. a; d 3. b=-d 1. b+d 2. b; return d 3; }

int main() { A obj 1(20, 10); A obj 2(20, 10); obj 1. display(); Obj 2. display(); A C; C=obj 1+obj 2; C. display(); }