Exer19_17_Screen.h

// Screen header from exercise 7.23.
#ifndef EXER19_17_SCREEN_H
#define EXER19_17_SCREEN_H
#include <string>
class Screen{
    // for test, required by exercise 19.12
    friend void ptrTest();
public:
    typedef std::string::size_type pos;
    // type alias for every kind of member function, required by exercise 19.17
    using Action1 = char (Screen::*)() const;
    using Action2 = char (Screen::*)(pos, pos) const;
    using Action3 = Screen& (Screen::*)(pos, pos);
    // return a pointer to data member, required by exercise 19.12
    static const std::string Screen::*data()
        { return &Screen::contents; }
    Screen() = default;
    Screen(pos ht, pos wd, char c) : height(ht), width(wd), contents(ht * wd, c) {}
    char get() const { return contents[cursor]; }
    char get_cursor() const { return contents[cursor]; }
    inline char get(pos ht, pos wd) const;
    Screen &move(pos r, pos c);
private:
    pos cursor = 0;
    pos height = 0, width = 0;
    std::string contents;
};
char Screen::get(pos r, pos c) const
{
    pos row = r * width;
    return contents[row + c];
}
Screen& Screen::move(pos r, pos c)
{
    pos row = r * width;
    cursor = row + c;
    return *this;
}
#endif