subcurrency.cpp

一、教学目的： 能理解C++中运算符重载的需要性

#include<iomanip.h>
class RMB:public currency
{
public:
	RMB(double v=0.0):currency(v){}
	virtual void display(ostream& out)
	{
		out<<yuan<<'.'
			<<setfill('0')<<setw(2)<<jf<<setfill(' ')
			<<" RMB";
	}
};
class Dmark:public currency//德国马克
{
public:
	Dmark(double v=0.0):currency(v){}
	virtual void display(ostream&out)
	{
		out<<yuan<<'.'
			<<setfill('0')<<setw(2)<<jf<<setfill(' ');
		out<<" DM";
	}
};
class WHQ:public RMB//人民币外汇券
{
public:
	WHQ(double v=0.0):RMB(v){}
	virtual void display(ostream& out)
	{
		RMB::display(out);
		out<<" WHQ";
	}
};