案例和转换问题

Question

我正在编写一个模拟ATM的程序。因此，它可以非常基本地跟踪帐户余额，取款和存款。

在第一次迭代中，一切工作都很好，但是如果我要进行两次或两次以上的存款或取款，则帐户余额默认会恢复为原始金额。

以下是当前情况的一个示例：我的帐户最初有$ 1,000。我存了50美元。它显示我的帐户中现在有$ 1,050，并询问是否要执行其他任何操作。 （这一切都很好）。如果我选择再次存入$ 100，则表示我的新帐户余额为$ 1,100，而不是$ 1,150。当我执行新的提款或存款时，它不会存储我的最新帐户余额。

第二个（不太重要）的问题是，每次进行提款时，每次提款都会产生$ 2.50的费用，这笔费用也会从我的帐户余额中扣除。

我还没有学习过循环，只有Cases，If语句和If Else语句。

可以做我想做的事吗？下面是我的代码。先感谢您！这是我第一次发布，因此，如果我粘贴的代码错误，我深表歉意。

#include <iostream>

#include <string>
using namespace std; // opens library for "cout"

int main()
{
    float test;
    int logout;
    string name;
    float balance;
    float fee;
    int choice;
    float withdraw;
    float deposit;
    float bonus;
    bonus = 2.50;
    balance = 1572.36;
    fee = 12.50;
    char answer;

    cout << "Hello, thank you for banking with Pallet Town Bank.\n";

    cout << "Please enter your name. ";

    cin >> name;

    cout << "Hello " << name << ". Your current balance is $" << balance << ".\n";
    cout << "There will be a a service fee of $12.50 subtracted from your "
            "account.\n";
    cout << "Your updated balance will be $" << balance - fee << " \n";
    cout << "What would you like to do today?\n";
    do
    {
        cout << "\n1 - Current Balance\n2 - Withdraw\n3 - deposit\n4 - Log "
                "Out\nOption: ";
        cin >> choice;

        switch (choice) 
        {
        case 1:
            cout << "\nCurrent Balance is " << balance - fee - withdraw + deposit
                 << " \n";
            cout << "Would you like to take any other actions today?\n";

            break;

        case 2:
            cout << "\nWithdraw - How much would you like to withdraw? $";
            cin >> withdraw;
            cout << "Your new balance after withdrawing $" << withdraw << " will be $"
                 << balance - fee - withdraw + deposit << "\n";
            cout << "Would you like to take any other actions today?\n";

            break;

        case 3:
            cout << "\nDeposit - How much would you like to deposit? $";
            cin >> deposit;

            test = balance - fee - withdraw + deposit;
            cout << "Your new balance after depositing $" << deposit << " will be $"
                 << test << endl; //<<balance - fee - withdraw + deposit<<"\n";
            cout << "Would you like to take any other actions today? Y or N \n";
            cin >> answer;

            cout << answer;
            if (answer == 'y' || 'Y')
            {
                test = balance - fee - withdraw + deposit + deposit;
                cout << "Your new balance after depositing $" << deposit << " will be $"
                     << test << endl;
            }
            // cout <<"Your new balance after depositing $"<<deposit<<" will be $"
            // <<test<< endl; //<<balance - fee - withdraw + deposit<<"\n";
            // cout <<"Would you like to take any other actions today?\n";

            break;

        case 4:
            cout << "\nLog Out - Thank you for banking with Pallet Town Bank. Have "
                    "a great day!";
        }
    } while (choice != 4);
}

Answer 1

正如艾伦·伯特尔斯（Alan Birtles）指出的那样，主要问题是您永远不会更新balance值。您只需将临时计算存储在test变量中即可。

这是更改代码的方式。我尝试从文本中尽力解释程序的预期行为：

#include <iostream>
#include <string>
using namespace std;


int main()
{
    const double fee = 12.50;
    double balance = 1572.36;

    cout << "Hello, thank you for banking with Pallet Town Bank.\n";

    cout << "Please enter your name. ";

    string name;
    cin >> name;

    cout << "Hello " << name << ". Your current balance is $" << balance << ".\n";
    cout << "There will be a a service fee of $12.50 subtracted from your "
            "account.\n";
    cout << "Your updated balance will be $" << (balance -= fee) << " \n";
    cout << "What would you like to do today?\n\n";

    while (true)
    {
        cout << "1 - Current Balance" << '\n'
             << "2 - Withdraw" << '\n'
             << "3 - deposit" << '\n'
             << "4 - Log Out" << '\n'
             << "Option: ";
        int choice;
        cin >> choice;
        cout << endl;
        if (choice == 4) break;

        switch (choice) 
        {
        case 1:
            cout << "Current Balance is " << balance << '\n';
            break;

        case 2:
            cout << "Withdraw - How much would you like to withdraw? $";
            double withdraw;
            cin >> withdraw;
            cout << "Your new balance after withdrawing $" << withdraw << " will be $"
                 << (balance -= withdraw) << '\n';
            break;

        case 3:
            cout << "Deposit - How much would you like to deposit? $";
            double deposit;
            cin >> deposit;
            cout << "Your new balance after depositing $" << deposit << " will be $"
                 << (balance += deposit) << '\n';
            break;            
        }

        cout << "Would you like to take any other actions today? ";
        char answer;
        cin >> answer;
        cout << endl;
        if (toupper(answer) == 'N') break;
    }

    cout << "Log Out - Thank you for banking with Pallet Town Bank. Have a great day!" << endl;
}

Live demo

更改

• 首先，每次进行修改（取款/存款）时，我们都需要实际更新balance。我们可以使用+=或-=运算符（称为“复合赋值”运算符）来实现：在编写balance += x时，我们在{{1}上添加了x }，而在写balance时我们就是在减去。这些表达式分别等效于balance -= x和balance = balance + x。

• 我将balance = balance - x部分移到了"Would you like to [...]"语句之外，以避免在每种情况下都重复。

• 如注释中所指出，switch与answer == 'Y' || 'y'不同。我将其更改为answer == 'Y' || answer == 'y'。

• 我将注销处理移到了toupper(answer) == 'Y'循环之外，以便无论循环何时终止，总是显示注销消息。这样一来，我们就可以从while语句中删除case 4，方法是先检查是否switch，然后choice == 4相应地退出循环。这也意味着该循环变为break循环。也许有一种更优雅的方式。

更好

如果您对函数感到满意，我建议您重构代码，分别隔离每个操作：

while (true)

Live demo