计算个税（定义一个薪水类）

（起征点800）：
#include <iostream>
using namespace std;

#define TAX_THRESHOLD 800

struct Tax {
	double standard;
	double tax_rate;
};

class Salary {
	double income;
public:
	static Tax tax_array[];
	Salary(int m = 0) {
		income = m;
	}
	void operator - (int payout) {
		income -= payout;
		cout << "工资余额：" << income << endl;
	}
	void CalculateSalary(void);
};

Tax Salary::tax_array[] = {
	{0,0.05}, {500, 0.10}, {2000, 0.15}, {5000,0.20}, {20000,0.25}, 
	{40000,0.30}, {60000,0.35}, {80000,0.40}, {100000,0.45}
};

void Salary::CalculateSalary(void)
{
	double tax = 0;
	double x = income - TAX_THRESHOLD;
	if(x > 0) {
		for(int i = sizeof(tax_array) / sizeof(*tax_array) - 1; i >= 0; i--) {
			if(x > tax_array[i].standard) {
				tax += (x - tax_array[i].standard) * tax_array[i].tax_rate;
				x = tax_array[i].standard;
			}
		}
	}
	cout << "税前工资为：" << income << endl;
	cout << "个人所得税为：" << tax << endl;
	income -= tax;
	cout << "实发工资为：" << income << endl;
}

int main(void)
{
	double myincome;
	double mypayout;
	while(cout << "您的月薪为：", cin >> myincome) {
		Salary mysalary(myincome);
		mysalary.CalculateSalary();
		cout << "取款金额：";
		cin >> mypayout;
		mysalary - mypayout;  //  硬性重载减号
		cout << endl;
	}
	
	return 0;
}
运行结果：
要修改的话很方便哦！（我也注意了魔数的问题）