class Empty

 {

   public:

       Empty(); //缺省构造函数 Empty e;

       Empty( const Empty& ); //拷贝构造函数 Empty e2(e1);

       ~Empty(); //析构函数

       Empty& operator=( const Empty& ); //赋值运算符 Empty e2 = e1;

       Empty* operator&(); //取址运算符 &e

       const Empty* operator&() const; //取址运算符const &e

 };

 class MyString

 {

 public:

     MyString(const char *str = NULL);//默认参数，不传递的该参数的时候发挥作用。

     MyString(const MyString &other);

     MyString& operator=(const MyString &other);

     ~MyString();

 private:

     char *m_data;

 };

 MyString::~MyString()

 {

     delete [] m_data;

 }

 MyString::MyString(const char *str)

 {

     if(NULL == str)

     {    cout<<"调用普通构造函数1"<<endl;

         m_data = new char[];

         *m_data = '\0';

     }

     else

     {

         cout<<"调用普通构造函数2"<<endl;

         size_t length = strlen(str);

         m_data = new char[length+];

         strcpy(m_data,str);

     }

 }

 MyString::MyString(const MyString &other)

 {    cout<<"调用拷贝构造函数"<<endl;

     size_t length = strlen(other.m_data);

     m_data = new char[length+];

     strcpy(m_data,other.m_data);

 }

 MyString& MyString::operator =(const MyString &other)

 {

     cout<<"调用赋值函数"<<endl;

     //检查自赋值

     if(this == &other)

         return *this;

     //释放原有的内存资源

     delete [] m_data;

     int length = strlen(other.m_data);

     m_data = new char[length+];

     strcpy(m_data,other.m_data);

     return *this;

 }

 int _tmain(int argc, _TCHAR* argv[])

 {

     MyString s0;//"调用普通构造函数1"

     MyString s1 = "hi";//"调用普通构造函数2"

     MyString s2("hi");//"调用普通构造函数2"

     MyString s3 = s1;//"调用拷贝构造函数"上述实现为深拷贝。

     MyString s4(s2);//"调用拷贝构造函数"

     s4 = "hello!";//将"hello!"传入赋值函数形参时，要调用普通构造函数2;接着调用赋值函数。

     s4 = s3;//"调用赋值函数"

     return ;

 }