7_68.cpp

a programme set to teach you how to use c

#include<iostream.h>
class sample
{
private:
	const int &r;
	const int x;
	static const int y;
	int z;
public:	
	sample(int i,int j);
	void disp()
	{
		cout<<"x="<<x<<",y="<<y<<",r="<<r<<",z="<<z<<endl;
		z++;
		cout<<"x="<<x<<",y="<<y<<",r="<<r<<",z="<<z<<endl;
		cout<<"x+y+z+r="<<gettotal()<<endl;  //调用成员函数gettotal()
		cout<<"一般成员函数可更新对象的数据成员！"<<endl;
	}
	int gettotal()  {return x+y+z+r;}
	void disp() const;
};
sample::sample(int i,int j):x(i),r(x)
{
	z=j;
}
void sample::disp()const
{
	//z++;  //error C2166: l-value specifies const object
	cout<<"x="<<x<<",y="<<y<<",r="<<r<<",z="<<z<<endl;
   // cout<<"x+y+z+r="<<gettotal()<<endl;
 //error C2662: 'gettotal' : cannot convert 'this' pointer from 'const class sample' to 'class //sample &'  Conversion loses qualifiers
    cout<<"常成员函数不可更新对象的数据成员！"<<endl;
	cout<<"常成员函数也不能调用该类中没有用const修饰的成员函数！"<<endl;
}
const int sample::y=10;
void main()
{
	sample a(1,2);
	a.disp();
	cout<<endl<<"常对象只能调用它的常成员函数，不能调用其它成员函数！"<<endl;
	const sample b(3,4);
	b.disp();
	cout<<"x+y+z+r="<<a.gettotal()<<endl;
//	cout<<"x+y+z+r="<<b.gettotal()<<endl;
// error C2662: 'gettotal' : cannot convert 'this' pointer from 'const class sample' to 'class //sample &'     Conversion loses qualifiers            
}