背景：私有继承
源代码：//rectangle.h
class point {private: float X,Y;
public: void InitP(float xx = 0, float yy = 0) { X = xx; Y = yy; }
void Move(float xff,float yff) { X += xff; Y += yff; } float GetX() {return X;} float GetY() {return Y;}};
class rectangle:private point{private: int W,H;
public: void InitR(float x,float y,float w,float h) { InitP(x,y); W = w; H = h; }
void Move(float xff,float yff) { point::Move(xff,yff); }
float GetX() {return X;} float GetY() {return Y;} //float GetX() {return point::GetX();} //去掉之后能访问X，Y //float GetY() {return point::GetY();} float GetW() {return W;} float GetH() {return H;}
};
//main()
#include <iostream>#include "rectangle.h"using namespace std;
int main(){ rectangle rect; rect.InitR(1,2,3,4); rect.Move(1,2); cout << rect.GetX() << "," << rect.GetY() << "," << rect.GetW() << "," << rect.GetH() << endl; return 0;}
错误提示：error C2248: 'X' : cannot access private member declared in class 'point'see declaration of 'X'error C2248: 'Y' : cannot access private member declared in class 'point'see declaration of 'Y'
错误分析：不能在类外用rectangle的对象访问GetX(),GetY(),原因何在？
研究结果（知识扩展）：私有继承后，派生类成员可以访问到从基类继承过来的公有和保护成员，但在类外部通过派生类的对象无法直接访问到基类的任何成员可以用派生类把基类的外部接口封装起来
