c++沉思录第十章的例子

关于虚函数和纯虚函数的知识需要我们好好注意。

#ifndef NEWPICTURE_H#define NEWPICTURE_H#include<iostream>using namespace std;class P_Node{friend class Picture;protected:P_Node();virtual ~P_Node(){};virtual int width()const=0;virtual int height()const=0;virtual void display(ostream &, int, int)const=0;int max(int x, int y)const { return x > y ? x : y; }void pad(ostream & os, int x, int y)const ;private:int use;};class Picture{friend class String_Pic;friend class Frame_Pic;friend class Hcat_Pic;friend class Vcat_Pic;public:Picture();Picture(const char * const *, int);Picture(const Picture &);~Picture();Picture & operator =(const Picture &);P_Node * p;Picture(P_Node * m);int height()const;int width()const;void display(ostream &, int, int)const;friend ostream & operator <<(ostream & os, const Picture & p);friend Picture frame(const Picture & p);friend Picture operator & (const Picture & p, const Picture & q);friend Picture operator | (const Picture & p, const Picture & q);};class String_Pic :public P_Node{friend class Picture;String_Pic(const char* const * arr, int n);~String_Pic();char** data;int size;int height()const;int width()const;void display(ostream &, int, int)const;};class Frame_Pic :public P_Node{friend Picture frame(const Picture &);int height()const;int width()const;void display(ostream &, int, int)const;Frame_Pic(const Picture &);Picture p;};class Vcat_Pic :public P_Node{friend Picture operator &(const Picture & n, const Picture & m);Vcat_Pic(const Picture & n, const Picture & m);int height()const;int width()const;void display(ostream &, int, int)const;Picture top, bottom;};class Hcat_Pic :public P_Node{friend Picture operator |(const Picture & n, const Picture & m);Hcat_Pic(const Picture & n, const Picture & m);int height()const;int width()const;void display(ostream &, int, int)const;Picture left,right;};Picture::Picture(const Picture & m) :p(m.p){m.p->use++;}Picture::Picture(P_Node * m) : p(m){}Picture::~Picture(){if (--p->use == 0)delete p;}Picture& Picture::operator=(const Picture & q){q.p->use++;if (--p->use == 0)delete p;p = q.p;return *this;}int Picture::height()const{ return p->height(); }int Picture::width()const { return p->width(); }void Picture::display(ostream & os, int n, int m)const{p->display(os, n, m);}Picture::Picture(const char* const * arr, int n) :p(new String_Pic(arr, n)){}P_Node::P_Node() :use(1){}String_Pic::String_Pic(const char * const * arr, int n): data(new char*[n]), size(n){for (int i = 0; i < n; ++i){data[i] = new char[strlen(arr[i]) + 1];strcpy_s(data[i],strlen(arr[i])+1,arr[i]);}}String_Pic::~String_Pic(){for (int i = 0; i < size; ++i)delete[]data[i];delete[]data;}int String_Pic::height()const{ return size; }int String_Pic::width()const{int n = 0;for (int i = 0; i < size; ++i)n = max(n, strlen(data[i]));return n;}void String_Pic::display(ostream & os, int row, int width)const{int start = 0;if (row >= 0 && row < height()){os << data[row];start = strlen(data[row]);}pad(os, start, width);}int Frame_Pic::height()const{ return p.height() + 2; }int Frame_Pic::width()const{ return p.width() + 2; }void Frame_Pic::display(ostream& os, int row, int wd)const{if (row < 0 || row >= height()){pad(os, 0, wd);}else{if ( 0 == row  || row == height() - 1){os << "+";int i = p.width();while (--i >= 0)os << "-";os << "+";}else{os << "|";p.display(os, row - 1, p.width());os << "|";}pad(os, width(), wd);}}Frame_Pic::Frame_Pic(const Picture & m) :p(m){}Picture frame(const Picture & m){return new Frame_Pic(m);}Vcat_Pic::Vcat_Pic(const Picture & t, const Picture & b) : top(t), bottom(b){}Hcat_Pic::Hcat_Pic(const Picture & l, const Picture & r) : left(l),right(r){}Picture operator &(const Picture & n, const Picture & m){return new Vcat_Pic(n, m);}Picture operator |(const Picture & n, const Picture & m){return new Hcat_Pic(n, m);}int Vcat_Pic::height()const{ return top.height() + bottom.height(); }int Vcat_Pic::width()const{ return max(top.width(), bottom.width()); }int Hcat_Pic::height()const{ return max(left.height(), right.height()); }int Hcat_Pic::width()const{ return left.width()+ right.width(); }void Vcat_Pic::display(ostream& os, int row, int wd)const{if (row >= 0 && row < top.height())top.display(os, row, wd);else{if (row < top.height() + bottom.height())bottom.display(os, row - top.height(), wd);elsepad(os, 0, wd);}}void Hcat_Pic::display(ostream & os, int row, int wd)const{left.display(os, row, left.width());right.display(os, row, right.width());pad(os, width(), wd);}void P_Node::pad(ostream & os, int x, int y)const{for (int i = x; i < y; ++i)os << " ";}ostream & operator <<(ostream & os, const Picture & p){int ht = p.height();for (int i = 0; i < ht; ++i){p.display(os, i, 0); os << endl;}return os;}#endif

#include"NewPicture.h"#include<iostream>using namespace std;int main(){char * init[] = { "Summer", "love", "Xieweizhong" };Picture p(init, 3);cout << p << endl;cout << frame((p | frame(p)) | (p | frame(p))) << endl;cout << frame((p & frame(p)) | (p | frame(p))) << endl;cout << frame((p | frame(p)) | (p & frame(p))) << endl;cout << frame((p & frame(p)) | (p & frame(p))) << endl;cout << frame((p | frame(p)) & (p | frame(p))) << endl;cout << frame((p & frame(p)) & (p | frame(p))) << endl;cout << frame((p | frame(p)) & (p & frame(p))) << endl;cout << frame((p & frame(p)) & (p & frame(p))) << endl;return 0;}