无聊，发点代码晾晾……

 

// a Screen class

#include<iostream>
#include<string>
using namespace std;

class Screen
{
public:
 typedef string ::size_type index;
 //the constructor
 Screen();
 Screen(index hh,index ww): height(hh),width(ww),cursor(hh),contents(hh*ww,' '),access_ctr(0){ }
 char get() const
 {
  return contents[cursor];
 }
 char get(index ht,index wd) const;
 inline index get_cursor() const;  //inline declared in the class declaration,but can be defined inline later
 Screen& move(index r,index c);
 Screen& set(char);
 Screen& set(index,index,char);
 //display overloaded on whether the object is const or not
 Screen& display(ostream &os)
 {
  do_display(os);
  return *this;
 }
 const Screen& display(ostream &os) const
 {
  do_display(os);
  return *this;
 } 
private:
 string contents;
 index cursor;
 index height,width;
 mutable size_t access_ctr;  //may change in a const members
 void do_display(ostream &os) const
 {
  ++access_ctr;
  os<<contents;
 }
};

Screen::Screen(): height(0),width(0),cursor(0),contents(""),access_ctr(0) { }//constructor
inline char Screen::get(index r,index c) const  //not declared inline in the class declaration,but ok to make inline in definition
{
 index row=r*width;
 return contents[row+c];
}
Screen& Screen::move(index r,index c)
{
 index row=r*width;
 cursor=row+c;
 return *this;
}
Screen& Screen::set(char c)
{
 contents[cursor]=c;
 return *this;
}
Screen& Screen::set(index r,index c,char ch)
{
 index row=r*width;
 cursor=row+c;
 contents[cursor]=ch;
 return *this;
}

int main()
{
 Screen myscreen(5,3);
 const Screen blank(5,3);
 myscreen.move(4,0);
 myscreen.set('#');
 myscreen.move(4,0).set('&');  //move cursor to given position,and set that character
 //calls nonconst version
 myscreen.move(4,0).set('*').display(cout);  //move cursor to given position,set that character and display the screen
 //calls const version
 blank.display(cout);
 myscreen.get(5,3);
// cout<<myscreen.access_ctr<<endl;
 return 0;
}