#include <iostream>

 using namespace std;

 class A{

 public:

     A &set(char);

     const A &display();

 //private:

     char a1 = 'l';

 };

 inline A &A::set(char c)

 {

     a1 = c;

     return *this;

 }

 inline const A &A::display()

 {

     cout << a1 << endl;

     return *this;

 }

 int main()

 {

 A screen;

 screen.display().set('a');   //错误,不能修改const对象;

 screen.a1 = 'z';

 //.set('l');

 return ;

 }