1 重载为类的成员函数：
格式： < 类名 > operator < 运算符 >(< 参数表 >)
例如：利用重载运算符实现复数类对象的算术四则运算。
#include
class complex
{
public:
complex(){ real=imag=0;}
complex(double r,double I)
{
real=r;imag=I;
}
complex operator +(complex &c);
complex operator -(complex &c);
complex operator *(complex &c);
complex operator /(complex &c);
friend void print(complex &c);
private:
double real,imag;
};
inline complex complex::operator +(complex &c)
{
return complex(real+c.real,imag+c.imag);
}
inline complex complex::operator (complex &c)
{
return complex(real-c.real,imag-c.imag);
}
inline complex complex::operator *(complex &c)
{
return complex(real*c.real-imag*c.imag,real*c.imag+imag*c.real);
}
inline complex complex::operator /(complex &c)
{
return complex((real*c.real+imag*c.imag)/(c.real*c.real+c.imag*c.imag),
(imag*c.real-real*c.imag)/(c.real*c.real+c.imag*c.imag));
}
void print(complex &c)
{
if(c.imag<0)
cout<
else
cout<
}
void main()
{
complex c1(2.0,3.0),c2(4.0,-2.0),c3;
c3=c1+c2;
cout<<”\nc1+c2=”;
print(c3);
c3=c1-c2;
cout<<”\nc1-c2=”;
print(c3);
c3=c1*c2;
cout<<”\nc1*c2=”;
print(c3);
c3=c1/c2;
cout<<”\nc1/c2=”;
print(c3);
c3=(c1+c2)*(c1-c2)*c2/c1;
cout<<”\n(c1+c2)*(c1-c2)*c2/c 1” ;
print(c3);
cout<
｝
说明：①程序中的表达式： c1+c2 ，编译程序将解释 c1.operator+(c2)
②当重载成为成员函数时，双目运算符仅有一个参数。对单目运算符，重载为成员函数时，总是隐含了一个 参数，该参数是 this 指针。 This 指针指向调用该成员函数对象的指针。
2、重载为友员函数：
当重载友员函数时，将没有隐含的参数 this 指针。这样，对双目运算符，友员函数有２个参数，对单目运算符，友员函数有一个参数。
格式： friend < 类型说明符 >operaotr < 运算符 >(< 参数表 >)
{……..}
例如：重写上例：
#include
class complex
{
public:
complex (){real=imag=0;}
complex(double r,double I)
{
real=r;imag=I;
}
friend complex operator +(complex &c1,complex &c2);
friend complex operator -(complex &c1,complex &c2);
friend complex operator *(complex &c1,complex &c2);
friend complex operator /(complex &c1,complex &c2);
friend void print(complex &c);
private:
double real,imag;
};
complex operator +(complex &c1,complex &c2)
{
return complex(c1real+c2.real,c1.imag+c2.imag);
}
complex operator (complex &c1,complex &c2)
{
return complex(c1.real-c2.real,c1.imag-c2.imag);
}
complex operator *(complex &c1,complex &c2)
{
return complex(c1real*c2.real-c1.imag*c2.imag,c1.real*c2.imag+c1.imag*c2.real);
}
complex operator /(complex &c1,complex &c2)
{
return complex((c1.real*c2.real+c1.imag*c2.imag)/(c1.real*c2.real+c1.imag*c2.imag),
(c1.imag*c2.real-c1.real*c2.imag)/(c1.real*c2.real+c1.imag*c2.imag));
}
void print(complex &c)
{
if(c.imag<0)
cout<
else
cout<
}
void main()
{
complex c1(2.0,3.0),c2(4.0,-2.0),c3;
c3=c1+c2;
cout<<”\nc1+c2=”;
print(c3);
c3=c1-c2;
cout<<”\nc1-c2=”;
print(c3);
c3=c1*c2;
cout<<”\nc1*c2=”;
print(c3);
c3=c1/c2;
cout<<”\nc1/c2=”;
print(c3);
c3=(c1+c2)*(c1-c2)*c2/c1;
cout<<”\n(c1+c2)*(c1-c2)*c2/c 1” ;
print(c3);
cout<
｝
说明： c1+c2 编译程序结实为 operator+(c1,c2), 将调用 complex operator +(complex &c1,complex &c2) 求值。
同理， c1-c2 理解为 operator (c1,c2), 调用 complex operator (complex &c1,complex &c2) 实现上述表达式的求值。
3 、两种重载形式的比较：