C++Primer第五版 7.4节练习

来源：互联网发布：win7日程安排软件编辑：程序博客网时间：2024/06/07 10:36

练习7.33：如果我们给Screen添加一个如下所示的size成员将发生什么情况？如果出现了问题，请尝试修改它。
pos Screen::size() const
{
return height * width;
}

在类里：
Public:
pos size() const;
类体外：
Screen::pos Screen::size() const
{
return height * width;
}
见云盘程序：练习7.33.cpp
练习7.33

/**练习7.33*2015/7/14*问题描述：练习7.33：如果我们给Screen添加一个如下所示的size成员将发生什么情况？如果出现了问题，请尝试修改它。   pos Screen::size() const{    return height * width;}*功能：修改 *作者：Nick Feng *邮箱：nickgreen23@163.com * */#include <iostream> #include <string>#include <vector> using namespace std;class Screen{public:    typedef std::string::size_type pos;    Screen() = default;    Screen(pos ht, pos wd, char c) : height(ht), width(wd), contents(ht * wd, c){}    char get() const { return contents[cursor]; }    inline char get(pos ht, pos wd) const;    Screen &move(pos r, pos c);    Screen &set(char);    Screen &set(pos, pos, char);    Screen &display(std::ostream &os)            {                do_display(os);                return *this;            }    const Screen &display(std::ostream &os) const            {                do_display(os);                return *this;            }        //extern void Window_mgr::clear(ScreenIndex);       //friend void Window_mgr::clear(ScreenIndex);    //friend void Window_mgr::clear(ScreenIndex);    //extern class Window_mgr;    //friend class Window_mgr;    //extern void Window_mgr::clear(ScreenIndex);    pos size() const;private:    pos cursor = 0;    pos height = 0, width = 0;    std::string contents;    void do_display(std::ostream &os) const { os << contents;}};inline Screen &Screen::move(pos r, pos c){    pos row = r * width;    cursor = row + c;    return *this;}char Screen::get(pos r, pos c) const{    pos row = r * width;    return contents[row + c];}inline Screen &Screen::set(char c){    contents[cursor] = c;    return *this;}inline Screen &Screen::set(pos r, pos col, char ch){    contents[r * width + col] = ch;    return *this;}Screen::pos Screen::size() const{    return height * width;}int main(){    Screen test(5,5,'x');    test.display(cout) ;    cout << endl;    cout << test.size() << endl;    return 0;}

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