实验三

最新推荐文章于 2020-04-07 12:46:51 发布

陈德志

最新推荐文章于 2020-04-07 12:46:51 发布

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CC 4.0 BY-SA版权

本文链接：https://blog.youkuaiyun.com/qq_41795310/article/details/80842493

实验目的和要求：

1.熟悉类的定义格式和类中成员的访问权限。

2.构造函数与析构函数的调用时机与顺序。

3.掌握对象的定义以及对象的初始化的时机与方法。

实验内容：

1.下面程序sy3-1.cpp中用ERROR标明的语句有错，在不删除和增加代码行的情况下，改正错误语句，使其正确运行。

#include<iostream>
using namespace std;
class Aa
{
 public:
  Aa(int i=0){a=i;cout<<"Constructor"<<a<<endl;}
  ~Aa(){cout<<"Destructor"<<a<<endl;}
void print(){cout<<a<<endl;}
private:
 
int a;
};
int main()
{
  Aa a1(1),a2(2);
 a1.print();
 cout<<a2.a<<endl;//ERROR
 return 0;
}

错误的运行结果如下图：

改正后的程序如下：

#include<iostream>    
using namespace std;    
class Aa    
{    
  public:    
      Aa(int i=0){a=i;cout<<"Constructor"<<a<<endl;}    
      ~Aa(){cout<<"Destructor"<<a<<endl;}    
      void print(){cout<<a<<endl;}    
  private:    
    int a;    
};    
int main()    
{    
    Aa a1(1),a2(2);    
    a1.print();    
    a2.print();    
    return 0;    
}

正确运行结果：

2.调试下列程序：

#include<iostream>  
using namespace std;  
class TPoint  
{  
public:  
    TPoint(int x,int y){X=x,Y=y;}  
    TPoint(TPoint &p);  
    ~TPoint(){cout<<"Destructor is called\n";}  
    int getx(){return X;}  
    int gety(){return Y;}  
private:  
    int X,Y;  
};  
TPoint::TPoint(TPoint &p)  
{  
    X=p.X;  
    Y=p.Y;  
    cout<<"Copy-initialization Constructor is called\n";  
}  
int main()  
{  
    TPoint p1(4,9);  
    TPoint p2(p1);  
    TPoint p3=p2;  
    TPoint p4,p5(2);  
    cout<<"p3=("<<p3.getx()<<","<<p3.gety()<<")\n";  
    return 0;  
}

在该程序中，将TPoint类的两个带有参数的构造函数进行修改，在函数体内增添下述语句：cout<<"Constructor is called.\n";

修改程序如下:

#include<iostream>  
using namespace std;  
class TPoint  
{  
public:  
    TPoint(int x,int y){X=x,Y=y;}  
    TPoint(TPoint &p);  
    ~TPoint(){cout<<"Destructor is called\n";}  
    int getx(){return X;}  
    int gety(){return Y;}  
private:  
    int X,Y;  
};  
TPoint::TPoint(TPoint &p)  
{  
    X=p.X;  
    Y=p.Y;  
    cout<<"Copy-initialization Constructor is called\n";  
    cout<<"Constructor is called\n";  
}  
int main()  
{  
    TPoint p1(4,9);  
    TPoint p2(p1);  
    TPoint p3=p2;  
    cout<<"p3=("<<p3.getx()<<","<<p3.gety()<<")\n";  
    return 0;  
}

结果如下:

（2）按下列要求进行调试：

在主函数体内，添加下列说明语句：

TPoint P4，P5(2);

#include<iostream>  
using namespace std;  
class TPoint  
{  
public:  
    TPoint(int x,int y){X=x,Y=y;}  
    TPoint(TPoint &p);  
    ~TPoint(){cout<<"Destructor is called\n";}  
    int getx(){return X;}  
    int gety(){return Y;}  
private:  
    int X,Y;  
};  
TPoint::TPoint(TPoint &p)  
{  
    X=p.X;  
    Y=p.Y;  
    cout<<"Copy-initialization Constructor is called\n";  
    cout<<"Constructor is called\n";  
}  
int main()  
{  
    TPoint P4,P5(2);  
    TPoint p1(4,9);  
    TPoint p2(p1);  
    TPoint p3=p2;  
    cout<<"p3=("<<p3.getx()<<","<<p3.gety()<<")\n";  
    return 0;  
}

运行如下:

3、对教材中Li3_11.cpp的主函数做如下修改：

（1）将Heapclass *pa1,*pa2 改为Heapclass *pa1,*pa2,*pa3;

（2）在语句pa2=new Heapclass 后增加语句pa3=new Heapclass(5);

（3）将语句 if(!pa1||!pa2) 改为if(!pa1||!pa2||!pa3)

（4）在语句delete pa2 后增加语句delete pa3;

写出程序的输出结果，并解释输出结果。

原程序如下：

#include<iostream>    
using namespace std;    
class Heapclass    
{    
    public:    
    Heapclass(int x);    
    Heapclass();    
    ~Heapclass();    
    private:    
    int i;    
};    
Heapclass::Heapclass(int x)    
{    
    i=x;    
    cout<<"Contstructor is called."<<i<<endl;    
}    
Heapclass::Heapclass()    
{    
cout<<"Default Contstructor is called."<<endl;    
}    
Heapclass::~Heapclass()    
{    
cout<<"Default is called."<<endl;    
}    
int main()    
{    
Heapclass *pa1,*pa2,*pa3;    
pa1=new Heapclass(4);    
pa2=new Heapclass;    
pa3=new Heapclass(5);    
if(!pa1||!pa2||!pa3);    
{    
    cout<<"Out of Memory!"<<endl;    
    return 0;    
}    
cout<<"Exit main"<<endl;    
delete pa1;    
delete pa2;    
delete pa3;    
return 0;    
}

输出结果:

4、请定义一个矩形类（Rectangle），私有数据成员为矩形长度（len）和宽度（wid），无参构造函数置len和wid为0，有参构造函数置len和wid为对应形参的值，另外还包括求矩形的周长、求矩形的面积、取矩形的长度和宽度、修改矩形的长度和宽度为对应形参的值、输出矩形尺寸等公有成员函数。要求输出矩形尺寸的格式为“length:长度，width:宽度”。（sy3_4.cpp）

#include<iostream>  
using namespace std;  
class Rectangle  
{  
public:  
   Rectangle()  
   {  
       len=0;  
       wid=0;  
   }  
   Rectangle(double Len,double Wid)  
   {  
       len=Len;  
       wid=Wid;  
    }  
   double Circumference()  
   {  
       return 2*(len+wid);  
    }  
   double Area()  
   {  
       return len*wid;  
    }  
   double getl()  
   {  
       return len;  
    }  
   double getw()  
   {  
       return wid;  
    }  
   void charge(double a,double b)  
   {  
       len=a;  
       wid=b;  
    }  
   void s()  
   {  
       cout<<"length:"<<len<<"  "<<"width:"<<wid<<endl;  
    }  
private:  
    int len,wid;  
};  
int main()  
{  
  Rectangle q;  
  Rectangle h(5.0,2.0);  
  cout<<"q的矩形尺寸："<<endl;  
  q.s();  
  cout<<"h的矩形尺寸："<<endl;  
  h.s();  
  cout<<"h的周长:"<<h.Circumference()<<endl;  
  cout<<"h的面积："<<h.Area()<<endl;  
  cout<<"h的长度："<<h.getl()<<endl;  
  cout<<"h的宽度："<<h.getw()<<endl;  
  h.charge(8.0,6.0);  
  cout<<"修改后的矩形的尺寸："<<endl;  
   h.s();  
   return 0;  
}

输出结果: