7.23.cpp

#include <string>

class Screen {
public:
  using pos = std::string::size_type;
  using content_type = char;

  Screen() = default;
  Screen(pos ht, pos wd)
      : height(ht), width(wd), contents(ht * wd, ' ') {}
  Screen(pos ht, pos wd, content_type c)
      : height(ht), width(wd), contents(ht * wd, c) {}

  const content_type &get() const { return contents[cursor]; }
  content_type &get() { return contents[cursor]; }
  const content_type &get(pos row, pos col) const;
  content_type &get(pos row, pos col);

  Screen &move(pos row, pos col);

private:
  pos cursor = 0;
  pos width = 0;
  pos height = 0;
  std::string contents;
};

inline
const Screen::content_type &Screen::get(pos row, pos col) const {
  return contents[row * width + col];
}

inline
Screen::content_type &Screen::get(pos row, pos col) {
  return contents[row * width + col];
}

inline
Screen &Screen::move(pos row, pos col) {
  cursor = row * width + col;
  return *this;
}

int main() {
  return 0;
}