eam0-4.cpp

一个简单的数值计算程序所使用的数据是一些实数或整数

#include <iostream.h>
#include <stdlib.h>
enum sign{minus, plus};      //正负数的符号标识

//类Money定义部分
class Money					//类Money定义
{
private:													//私有部分
	friend ostream& operator<<(ostream& out, const Money& x);  
//运算符<<重载，设计成类的友元
long amount;							//类Money的属性，以分为单位
public:														//公有部分
	//构造函数
	Money(sign s  = plus, unsigned long d = 0, unsigned long c = 0);
	~Money(){};											//析构函数

	bool Set(sign s, unsigned long d, unsigned long c);	//设置成员函数
			Money operator+(const Money& x) const;				//加运算符
	Money& operator+=(const Money& x)					//加等于运算符
	{amount += x.amount; return *this;}//this是默认的当前对象指针
};

//类Money实现部分
Money::Money(sign s, unsigned long d, unsigned long c)
//构造函数。s为符号， d为元值，c为分值
{
	if(c > 99)
	{
		cerr << "分必须小于等于99" << endl;
		exit(1);
	}
	amount = d * 100 + c;
	if(s == minus) amount = -amount;
}

bool Money::Set(sign s, unsigned long d, unsigned long c)
//设置函数。s为符号， d为元值，c为分值
{
	if(c > 99)
	{
		cerr << "分必须小于等于99" << endl;
		false;
	}
	amount = d * 100 + c;
	if(s == minus) amount = -amount;
	return true;
}

Money Money::operator+(const Money& x) const				//加运算符
{
	Money y;
	y.amount = amount + x.amount;
	return y;
}

ostream& operator<<(ostream& out, const Money& x)  		//运算符<<重载
{
	Money temp = x;	
	if(x.amount < 0 )
	{
		out << "-";
		temp.amount = -temp.amount;			//temp为x的绝对值
	}
	int d = temp.amount / 100;			//d为amount的元值
	out << "￥" << d << ".";
	int c = temp.amount - d * 100;		//c为amount的分值
	if(c < 10) out << "0";		//分值小于10时在十位上添0
	out << c;
	return out;
}

//主函数部分
void main(void)
{
	Money g, h(plus, 3, 30), hg;

	g.Set(minus, 2, 25);
	hg = h + g;								//h和g的值均不变
	g += h;									//g的值被改变
	cout << "h + g = " << hg <<endl;			//可直接用运算符<<输出类hg
	cout << "g = " << g << endl;
}