第七章——实验

实验目的和要求

熟悉运算符重载的定义和使用方法。

实验内容

1、调试下列程序。

#include<iostream>    
using namespace std;    
class complex    
{    
    public:    
        complex(){real=imag=0.0;}    
        complex(double r){real=r;imag=0.0;}    
        complex(double r,double i){real=r;imag=i;}    
        complex operator + (const complex &c);    
        complex operator - (const complex &c);    
        complex operator * (const complex &c);    
        complex operator / (const complex &c);    
        friend void print(const complex &c);    
    private:    
        double real,imag;    
};    
inline complex complex::operator + (const complex &c)    
{    
    return complex(real+c.real,imag+c.imag);    
}    
inline complex complex::operator - (const complex &c)    
{    
    return complex(real-c.real,imag-c.imag);    
}    
inline complex complex::operator * (const complex &c)    
{    
    return complex(real*c.real-imag*c.imag,real*c.imag+imag*c.real);    
}    
inline complex complex::operator / (const 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(const complex &c)    
{    
    if(c.imag<0)    
        cout<<c.real<<c.imag<<"i";    
    else    
        cout<<c.real<<"+"<<c.imag<<"i";    
}    
int main()    
{    
    complex c1(2.0),c2(3.0,-1.0),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/c1= ";    
    print(c3);    
    cout<<endl;    
    return 0;    
}  

运行程序如下：

2.调试下列程序:

#include<iostream>    
using namespace std;    
class complex    
{    
    public:    
        complex(){real=imag=0.0;}    
        complex(double r){real=r;imag=0.0;}    
        complex(double r,double i){real=r;imag=i;}    
        friend complex operator + (const complex &c1,const complex &c2);    
        friend complex operator - (const complex &c1,const complex &c2);    
        friend complex operator * (const complex &c1,const complex &c2);    
        friend complex operator / (const complex &c1,const complex &c2);    
        friend void print(const complex &c);    
    private:    
        double real,imag;    
};    
complex operator + (const complex &c1,const complex &c2)    
{    
    return complex(c1.real+c2.real,c1.imag+c2.imag);    
}    
complex operator - (const complex &c1,const complex &c2)    
{    
    return complex(c1.real-c2.real,c1.imag-c2.imag);    
}    
complex operator * (const complex &c1,const complex &c2)    
{    
    return complex(c1.real*c2.real-c1.imag*c2.imag,c1.real*c2.imag+c1.imag*c2.real);    
}    
complex operator / (const complex &c1,const complex &c2)    
{    
    return complex((c1.real*c2.real+c1.imag*c2.imag)/(c2.real*c2.real+c2.imag*c2.imag),(c1.imag*c2.real-c1.real*c2.imag)/(c2.real*c2.real+c2.imag*c2.imag));    
}    
void print(const complex &c)    
{    
    if(c.imag<0)    
        cout<<c.real<<c.imag<<"i";    
    else    
        cout<<c.real<<"+"<<c.imag<<"i";    
}    
int main()    
{    
    complex c1(2.0),c2(3.0,-1.0),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/c1= ";    
    print(c3);    
    cout<<endl;    
    return 0;    
}    

运行程序如下：

3.定义一个Time类用来保存时间（时，分，秒），通过重载操作符“+”实现两个时间的相加。（sy7_3.cpp）
程序如下：

#include <stdio.h>      
  class Time      
  {      
  public:      
    Time(){ hours=0;minutes=0;seconds=0;} //无参构造函数      
    Time(int h, int m,int s) //重载构造函数      
    {      
             hours=h; minutes=m; seconds=s;      
    }      
    Time operator +(Time&); //操作符重载为成员函数，返回结果为Time类      
    void gettime();      
  private:      
    int hours,minutes,seconds;      
  };      
  Time Time::operator +(Time& time)      
  {      
  int h,m,s;      
  s=time.seconds+seconds;      
  m=time.minutes+minutes+s/60;      
  h=time.hours+hours+m/60;      
  Time result(h,m%60,s%60);      
  return result;      
  }      
  void Time::gettime()      
  {      
  printf("%d:%d:%d\n",hours,minutes,seconds);      
  }      
  int main( )      
  {      
  Time t1(9,35,45),t2(12,15,32),t3;      
  t3=t1+t2;      
  t3.gettime();      
  return 0;      
  }    

运行结果如下：

分析与讨论
结合上题中的程序总结运算符重载的形式。
答：运算符函数重载一般有两种形式：重载为类的成员函数和重载为类的非成员函数。非成员函数通常是友元。（可以把一个运算符作为一个非成员、非友元函数重载；但是，这样的运算符函数访问类的私有和保护成员时，必须使用类的公有接口中提供的设置数据和读取数据的函数，调用这些函数时会降低性能。可以内联这些函数以提高性能。）
当运算符重载为类的成员函数时，函数的参数个数比原来的操作数要少一个（后置单目运算符除外），这是因为成员函数用this指针隐式地访问了类的一个对象，它充当了运算符函数最左边的操作数。因此：双目运算符重载为类的成员函数时，函数只显式说明一个参数，该形参是运算符的右操作数。前置单目运算符重载为类的成员函数时，不需要显式说明参数，即函数没有形参。后置单目运算符重载为类的成员函数时，函数要带有一个整型形参。
当运算符重载为类的友元函数时，由于没有隐含的this指针，因此操作数的个数没有变化，所有的操作数都必须通过函数的形参进行传递，函数的参数与操作数自左至右一一对应。