1.不改变运算符的优先级
2.不改变运算符的结合性
3.不改变运算符所需要的操作数
4.不能创建新的运算符
5.运算符函数可以重载为成员函数或者友元函数
}
类型
类名
默认版本
一元运算符
Object.operator op()
二元运算符
Objectl op objectr
Objectl.operator op (objectr)
用成员函数重载运算符
Class x
};
此时当前对象作为运算符的左操作数，它时通过this指针隐含的传递给函数的。
{
public:
Complex( ){real=0,imag=0;}
Complex(double r,double i){real=r; imag=i;}
void display( );
private:
double real;
double imag;
};
ComplexComplex:: operator + (Complex &c2) {
return Complex(real+c2.real, imag+c2.imag);}
void Complex::display( ){
cout<<"("<<real<<","<<imag<<"i)"<<endl;}
int main( ){
Complex c1(3,4),c2(5,-10),c3;
c3=c1+c2;
cout<<"c1=";c1.display( );
cout<<"c2=";c2.display( );
cout<<"c1+c2 =";c3.display();
return 0;
}
显示调隐式调用
单目运算符重载为成员函数
class Time
{
public:
Time(){minute=0;sec=0;}
private:
intminute;
intsec;
};
{
if(++sec>=60){
++minute;
}
}
{
Timetemp(*this);
sec++;
if(sec>=60) {
sec-=60;
++minute;
}
}
classComplex
{intReal ; intImag ;
public :
Complex ( int a ) { Real = a ;Imag = 0 ; }
Complex ( inta,intb ) { Real = a ;Imag = b ; }
Complexoperator + ( Complex ) ;
};
intf ( )
成员函数与友元运算符函数的比较
前置方式
后置方式
#include<iostream>
using namespace std;
classIncrease
{ public :
Increase () { value=0; }
voiddisplay( )const{ cout<<value<<'\n'; } ;
private:unsignedvalue ;
};
IncreaseIncrease :: operator ++ ( )
{ value ++;return *this ; }
IncreaseIncrease :: operator ++ ( int )
{ Increasetemp;temp.value = value ++ ;returntemp; }
int main( )
int main()
{ Name Obj1( "ZhangSan" ) ;
Name Obj3("NoName" ) ;
}
Name::Name ( char*pN )
{ cout<<" Constructing " << pN << endl ;
pName = newchar[ strlen( pN ) + 1 ] ;
if( pName !=0 ) strcpy( pName,pN ) ;
size =strlen( pN ) ;
}
{ cout << " Copying " <<Obj.pName << " into its own block\n";
pName = new char[strlen( Obj.pName ) + 1 ] ;
if ( pName !=0 ) strcpy( pName, Obj.pName ) ;
size =Obj.size;
}
{ delete[]pName ;
if ( pName !=0 ) strcpy( pName , Obj.pName ) ;
size =Obj.size ;
return *this;
}
Name::~ Name()
{ cout << " Destructing " <<pName << endl ;
delete[]pName ;
size = 0;
}
重载运算符【】和（）
运算符【】和（）时二元运算符
【】和（）只能用成员函数重载，不能使用友元函数重载
1.
x [ y ]
x . operator [ ]( y )
#include<iostream>
using namespacestd;
classvector
{ public :
vector ( intn ){v = newint [ n ] ; size = n ; }
~ vector ( ){ delete [ ] v ; size = 0 ; }
int & operator [ ] ( inti ){returnv [ i ] ; }
private :
int * v ;int size ;
};
int main ( )
{vectora ( 5 ) ;
a [ 2 ] = 12 ;
cout << a [ 2 ] << endl ;
}
2.
#include <iostream>
using namespace std ;
classF
{ public:
doubleoperator ( )( double x ,doubley ) ;
} ;
doubleF ::operator ( )( doublex ,doubley )
{ returnx * x + y * y ; }
int main ( )
{ Ff;
cout <<f ( 5.2 , 2.5 ) << endl ;
}
{
out<<obj.item1;
out<<obj.item2;
.. .
out<<obj.itemn;
return out;
}
{
in>>obj.item1;
in>>obj.item2;
. . .
in>>obj.itemn;
return in;
}
#include<iostream>
#include<cstdlib>
using namespace std;
class vector
{ public :
vector( int size =1 ) ;~vector() ;
int & operator[] ( int i ) ;
friend ostream & operator << ( ostream & output , vector& ) ;
friend istream & operator >> ( istream & input, vector& ) ;
private :
int * v ;int len ;
};
int main(){
int k ;cout <<"Input the length of vector A :\n" ;cin >> k ;
vector A( k ) ;cout <<"Input the elements of vector A :\n" ;
cin >> A ;cout<< "Output the elements of vector A :\n" ;
cout << A ;
}
vector::vector( int size )
{ if (size <= 0 || size > 100 )
v= new int[ size ] ;len = size ;
}
vector :: ~vector() { delete[] v ;len = 0 ; }
int & vector :: operator [] (int i )
{ if( i >=0 && i < len )return v[ i ] ;
cout << "The subscript " << i << " isoutside !\n" ;exit( 0 ) ;
}
ostream & operator << (ostream & output, vector & ary )
{ for(int i = 0 ; i < ary.len ; i ++)output << ary[ i ] <<"" ;
output << endl ;
return output ;
}
istream & operator >> (istream & input, vector & ary )
{ for( int i = 0 ; i < ary.len ; i ++)input >> ary[ i ] ;
returninput ;
}