C++ 个人银行账户管理程序 const{return} 古怪的用法
#include <iostream>#include <cmath>
using namespace std;
class SavingsAccount
{
private:
int id;
double balance;
double rate;
int lastDate;
double accumulation;
void record(int date, double amount);
double accumulate(int date) const ------------------------------------------------------>//好奇怪的用法，这是数据保护吗？
{
return accumulation + balance * (date - lastDate);
}
public:
SavingsAccount(int date, int id, double rate);
int getId() { return id; }
double getBalance() { return balance; }
double getRate() { return rate; }
void deposit(int date, double amount);
void withdraw(int date, double amount);
void settle(int date);
void show();
};
SavingsAccount::SavingsAccount(int date, int id, double rate) : id(id), balance(0), rate(rate), lastDate(date), accumulation(0)
{
cout << date << "\t#" << id << " is created" << endl;
}
void SavingsAccount::record(int date, double amount)
{
accumulation = accumulate(date);
lastDate = date;
amount = floor(amount * 100 + 0.5) / 100;
balance += amount;
cout << date << "\t#" << id << "\t" << amount << "\t" << balance << endl;
}
void SavingsAccount::deposit(int date, double amount)
{
record(date, amount);
}
void SavingsAccount::withdraw(int date, double amount)
{
if (amount > getBalance())
cout << "Error:not enough money" << endl;
else
record(date, -amount);
}
void SavingsAccount::settle(int date)
{
double interest = accumulate(date) * rate / 365;
if (interest != 0)
record(date, interest);
accumulation = 0;
}
void SavingsAccount::show()
{
cout << "#" << id << "\tBalance:" << balance;
}
int main()
{
SavingsAccount sa0(1, 21325302, 0.015);
SavingsAccount sa1(1, 58320212, 0.015);
sa0.deposit(5, 5000);
sa1.deposit(25, 10000);
sa0.deposit(45, 5500);
sa1.withdraw(60, 4000);
sa0.settle(90);
sa1.settle(90);
sa0.show(); cout << endl;
sa1.show(); cout << endl;
return 0;
}
double accumulate(int date) const 对这个就是对数据的一种保护这种函数叫做常函数因为里面的 变量是不可以改变的，
此外 此函数可以在 const类 对象中使用
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