类操作初步

#include <iostream>
#include <string>

using namespace std;

class Screen
{
  public:
      typedef string::size_type index;
      char get() const
      {
          return contents[cursor];
      }
      inline char get(index r,index c) const;
      index get_cursor() const;
      Screen(index hght,index wght,const string &cntnts);

      /*以下成员函数的返回类型是Screen&,指明该成员函数返回对其自身
        类类型的对象的引用，即每个函数都返回调用自己的那个对象*/
      Screen& move(index r,index c);
      Screen& set(char);
      Screen& display(ostream &os);
  private:
      std::string contents;
      index cursor;
      index height,width;
};

Screen::Screen(index hght,index wdth,const string &cntnts):
        contents(cntnts),cursor(0),height(hght),width(wdth)
{}

char Screen::get(index r,index c) const
{
    index row = r*width;
    return contents[row + c];
}

/*index属于Screen类，类外使用，必须加“：：“*/
Screen::index Screen::get_cursor() const
{
    return cursor;
}

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::display(ostream &os)
{
    os << contents;
    return *this;
}

int main(int argc,char *argv[])
{
    /*根据屏幕的高度，宽度和内容的值来创建Screen*/
    Screen myScreen(5,6,"aaaaa\naaaaa\naaaaa\naaaaa\naaaaa\n");

    /*将光标移至指定位置，设置字符并显示屏幕内容*/
    myScreen.move(4,0).set('#').display(cout);
    
    return 0;
}