此代码中的函数是否有错误？

Question

该程序应该使用单个函数来返回多个值。但是，由于函数一次只能返回一个值，因此我实现了一个开关。但是，当我运行代码时，总工资，税金和净工资默认为0而不是加起来。有谁知道为什么会这样？我只允许使用带开关的单个函数来返回不同的值。

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <iomanip>
#include <string.h>
using namespace std;

double paycalculations(double, double, double, double, int);

double paycalculations(double hrs, double pay, double fedrate, double staterate, int option)
{
    switch (option)
    {
        case 1:
            double reg;
                if (hrs < 0)
                {
                    hrs = hrs * (-1);
                }
                if (hrs <= 40)
                {
                    reg = hrs * pay;
                }
                else
                {
                    reg = 40 * pay;
                }
            return reg;
            break;
        case 2:
            double overtime;
                overtime = (hrs - 40) * (1.5 * pay);
            return overtime;
            break;
        case 3:
            double gross;
                if (overtime > 0)
                {
                    gross = reg + overtime;
                }
                else
                {
                    gross = reg;
                }
            return gross;
            break;
        case 4:
            double ftaxes;
            ftaxes = gross * fedrate;
            return ftaxes;
            break;
        case 5:
            double staxes;
            staxes = gross * staterate;
            return staxes;
            break;
        case 6:
            double socialsectaxes;
            socialsectaxes = gross * 0.062;
            return socialsectaxes;
            break;
        case 7:
            double medtaxes;
            medtaxes = gross * 0.0145;
            return medtaxes;
            break;
        case 8:
            double net;
            net = gross - (ftaxes + staxes + socialsectaxes + medtaxes);
            return net;
            break;
    }
}
int main ()
{
    string employeeID;
    double hours, payrate, fedtaxrate, statetaxrate, regpay, overtimepay, grosspay, fedtaxes, statetaxes, sosectaxes, meditaxes, netpay;
    const int SIZE = 100;
    char again = 'y', fullname[SIZE] = {" "};
    while (again == 'y')
    {
        hours = payrate = fedtaxrate = statetaxrate = regpay = overtimepay = fedtaxes = statetaxes = sosectaxes = meditaxes = netpay = 0;
        system("reset");
        cout <<"Employee Full Name: ";
        cin.getline(fullname, SIZE);
        cout << "\nEmployee ID: ";
        cin >> employeeID;
        cout << "\nHours Worked (Maximum of 60): ";
        cin >> hours;
        cout << "\nEmployee Payrate: $";
        cin >> payrate;
        cout << "\nFederal Tax Rate (Maximum of 0.5 or 50%): ";
        cin >> fedtaxrate;
        cout << "\nState Tax Rate (Maximum of 0.3 or 30%): ";
        cin >> statetaxrate;

        cout.setf(ios::fixed | ios::showpoint);

        system("reset");
        cout << "\t\t\t\t\tPayroll";
        cout << "\n\nEmployee ID: " << employeeID;
        cout << "\t\nEmployee Name: " << fullname;
        cout.precision(1);
        cout << "\n\nTotal Hours Worked: " << "\t\t\t\t" << hours;

        cout.precision(2);
        regpay = paycalculations(hours, payrate, fedtaxrate, statetaxrate, 1);
        if (hours <= 40)
        {
            cout << "\nRegular Hours Worked: " << hours << " @ $" << payrate << "/hour" << "\t" << "$" << regpay;
        }
        overtimepay = paycalculations(hours, payrate, fedtaxrate, statetaxrate, 2);
        if (hours > 40)
        {
            cout << "\nRegular Hours Worked: " << "40.00 @ $" << payrate << "/hour" << "\t" << "$" << regpay;
            cout << "\nOvertime Hours Worked: " << (hours - 40) << " @ $" << (payrate * 1.5) << "/hour" << "\t" << "$" << overtimepay;
        }
        grosspay = paycalculations(hours, payrate, fedtaxrate, statetaxrate, 3);
        cout << "\nGross Pay: " << "\t\t\t\t\t" << "$" << grosspay;
        fedtaxes = paycalculations(hours, payrate, fedtaxrate, statetaxrate, 4);
        cout << "\nFederal Taxes Withheld @" << (fedtaxrate * 100) << "%" << "\t\t\t" << "$" << fedtaxes;
        statetaxes = paycalculations(hours, payrate, fedtaxrate, statetaxrate, 5);
        cout << "\nState Taxes Withheld @" << (statetaxrate * 100) << "%" << "\t\t\t" << "$" << statetaxes;
        sosectaxes = paycalculations(hours, payrate, fedtaxrate, statetaxrate, 6);
        cout << "\nSocial Security Withheld @" << (0.062 * 100) << "%" << "\t\t\t" << "$" << sosectaxes;
        meditaxes = paycalculations(hours, payrate, fedtaxrate, statetaxrate, 7);
        cout << "\nMedicare Withheld @" << (0.0145 * 100) << "%" << "\t\t\t" << "$" << meditaxes;
        netpay = paycalculations(hours, payrate, fedtaxrate, statetaxrate, 8);
        cout << "\nNet Pay: " << "\t\t\t\t\t" << "$" << netpay;

        cout << "\n\nWould you like to compute another employee's pay check? (Y or N): ";
        cin >> again;
        again = tolower(again);
    }
}