Introduction to ProgrammingIntroduction to Programming

Lecture 31Lecture 31

Operator Operator OverloadingOverloading

Today’s LectureToday’s Lecture

– OperatorsOperators– Syntax for overloading Syntax for overloading

operatorsoperators– How to overload How to overload operators ?operators ?

Complex Complex NumberNumber

complex c1 , c2 , x ;complex c1 , c2 , x ;

x = cadd ( c1 , c2 ) ;x = cadd ( c1 , c2 ) ;

x = cadd ( cadd ( a , b ) , c ) ;x = cadd ( cadd ( a , b ) , c ) ;

OperatorsOperators The complete list of C++ operators that are The complete list of C++ operators that are

overloaded is as followsoverloaded is as follows

+ - * / % ^ & + - * / % ^ & | ~ ! = < > += | ~ ! = < > += -= *= /= %= ^= &= |= -= *= /= %= ^= &= |= << >> >>= <<= = = != <= << >> >>= <<= = = != <= >= && | | ++ - - -> * , >= && | | ++ - - -> * , -> [ ] ( ) new new[ ] delete -> [ ] ( ) new new[ ] delete delete [ ]delete [ ]

a + ba + b

Date.dayDate.day

Example Example

Return_type operator + Return_type operator + (Argument_List)(Argument_List)

{{

// Body of function// Body of function

}}

a * b + c ;a * b + c ;

x = y + z ;x = y + z ;

Example Example class Complexclass Complex{{

private :private :double real ;double real ;double imag ;double imag ;

public :public :// member function// member function

}}

ExampleExampleComplex c1 , c2 ;Complex c1 , c2 ;

c1 = c2 ;c1 = c2 ;

Is equivalent toIs equivalent to

c1.real = c2.real ;c1.real = c2.real ;

c1.imag = c2.imag ; c1.imag = c2.imag ;

Complex operator + ( Argument_ Complex operator + ( Argument_ list ) ;list ) ;

Complex Complex :: operator + ( Complex Complex Complex :: operator + ( Complex c )c )

{{

Complex temp ;Complex temp ;

temp.real = real + c.real ;temp.real = real + c.real ;

temp.imag = imag + c.imag ;temp.imag = imag + c.imag ;

return temp ;return temp ;

}}

ExampleExample

Complex x , y , Complex x , y , z ;z ;

z = x + y ;z = x + y ;

z = x + d ;z = x + d ;Complex Number

Complex Number

DoublePrecision Number

Complex operator + ( double d Complex operator + ( double d ) ;) ;

z = x + y ;z = x + y ;z = x + d ;z = x + d ;

Complex Complex :: operator + ( Complex Complex Complex :: operator + ( Complex c )c )

{{

Complex temp ;Complex temp ;

temp.real = real + d ; temp.real = real + d ;

temp.imag = imag ;temp.imag = imag ;

return temp ;return temp ;

}}

ExampleExample

z = d + z = d + x ;x ;

Complex Number Double

Precision Number

Complex Number

Friend Friend FunctionFunction

User DefinedUser Defined

Data typesData types

<<<<

Example Example main ( )main ( )

{{

Complex c1 ( 1 , 2 ) , c2 ( 3 , 4 ) , Complex c1 ( 1 , 2 ) , c2 ( 3 , 4 ) , c3 ;c3 ;

c3 = c1 + c2 ;c3 = c1 + c2 ;

c1.display ( ) ;c1.display ( ) ;

c2.display ( ) ;c2.display ( ) ;

c3.display ( ) ;c3.display ( ) ;

}}

Complex operator + ( Complex & c Complex operator + ( Complex & c ) ;) ;

C is a reference to a complex number

i += 2 ;i += 2 ;

i = i + 2 ;i = i + 2 ;

c1 += c1 += c2 ;c2 ;

ExampleExample

Complex operator += ( Complex & Complex operator += ( Complex & c )c )

ExampleExampleComplex Complex :: operator += ( Complex & c )Complex Complex :: operator += ( Complex & c ){{

real += c.real ;real += c.real ;imag += c.imag ;imag += c.imag ;

}}

Complex operator + ( Complex & c1 , Complex & c2 )Complex operator + ( Complex & c1 , Complex & c2 )

{{Complex temp ;Complex temp ;temp.real = c1.getreal ( ) + c2.getreal ( ) ;temp.real = c1.getreal ( ) + c2.getreal ( ) ;temp.imag = c1.getimag ( ) + c2.getimag ( ) temp.imag = c1.getimag ( ) + c2.getimag ( ) ;;return temp ;return temp ;

}}

ExampleExample

ExampleExampleclass Stringclass String{{ private :private :

char s [ 30 ] ;char s [ 30 ] ;

public :public :

String ( ) String ( ) {{ strcpy ( s , "" ) ;strcpy ( s , "" ) ; }}

// Declaration (prototype) of overloaded sum operator// Declaration (prototype) of overloaded sum operator

String operator + ( String c ) ;String operator + ( String c ) ;} ;} ;

Example Example String String :: operator + ( String c )String String :: operator + ( String c )

{ {

String temp ;String temp ;

strcpy ( temp.s , "" ) ;strcpy ( temp.s , "" ) ;

strcat ( temp.s , s ) ;strcat ( temp.s , s ) ;

strcat ( temp.s , c.s ) ;strcat ( temp.s , c.s ) ;

return temp ;return temp ;

}}