C++ 中的重载错误 [按值传递和按引用传递]

Question

我正在做一个项目，该项目使用超载计算两种类型的员工（受薪和小时）的收入。这个项目有 3 个文件，这里是主要来源：

#include <iostream>
#include "Grosspay.h"
using namespace std;

void Grosspay::determineGrosspay()
{
    cout << "Enter 1 - Calculate payroll for hourly employee" << endl;
    cout << "Enter 2 - Calculate payroll for salary employee" << endl;
    cout << "Enter 3 - Exit" << endl;

    cout << "Federal Tax is 10% of Grosspay" << endl;
    cout << "State Tax is 5% of Grosspay" << endl;
    while (choice != 3)
    {
        cout << "\nEnter your choice: " << endl;
        cin >> choice;
        switch (choice)
        {
        case 1:
            cout << "Enter employee ID: " << endl;
            cin >> ID;
            cout << "Enter hours: " << endl;
            cin >> hours;
            cout << "Enter payrate: " << endl;
            cin >> payrate;

            cout << "Employee ID: %d" << ID << endl;
            cout << "The net pay for hourly employee: %.2f\n" << income(hours, payrate) << endl;
            break;
        case 2:
            cout << "Enter employee ID: " << endl;
            cin >> ID;
            cout << "Enter salary: " << endl;
            cin >> year;

            cout << "The net pay for salaried employee: %.2f\n" << income(year) << endl;
            break;
        case 3:
            cout << "Exited program" << endl;
            break;
        default:
            cout << "Please try again!" << endl;
            break;
        }
    }
}
double income(double hours, double payrate)
{
    double grosspay = 0;
    double federaltax = .10;
    double statetax = .05;
    double totaltax;
    double netpay;
    if (hours <= 40)
    {
        grosspay = payrate * hours;
    }if (hours > 40 && hours <= 50)
    {
        grosspay = (payrate * 40) + ((hours - 40) * payrate * 1.5);
    }
    if (hours > 50)
    {
        grosspay = (payrate * 40) + (10 * payrate * 1.5) + ((hours - 50) * payrate * 2);
    }
    cout << "Grosspay weekly is %.2f\n" << grosspay << endl;

    federaltax = grosspay * .10;
    cout << "Federal Tax is: %.2f\n" << federaltax << endl;

    statetax = grosspay * .05;
    cout << "State Tax is: %.2f\n" << statetax << endl;

    totaltax = federaltax + statetax;
    cout << "Total tax is: %.2f\n" << totaltax << endl;

    netpay = grosspay - totaltax;
    return (netpay);

}
double income(double year)
{
    double grosspay;
    double federaltax = .10;
    double statetax = .05;
    double totaltax;
    double netpay;

    grosspay = year / 52;
    cout << "Grosspay weekly is %.2f\n" << grosspay << endl;

    federaltax = grosspay * .10;
    cout << "Federal Tax is: %.2f\n" << federaltax << endl;

    statetax = grosspay * .05;
    cout << "State Tax is: %.2f\n" << statetax << endl;

    totaltax = federaltax + statetax;
    cout << "Total Tax is: %.2f\n" << totaltax << endl;

    netpay = grosspay - totaltax;
    return (netpay);
}

我不知道为什么程序找不到收入 来自

cout << "The net pay for hourly employee: %.2f\n" << income(hours, payrate) << endl;
cout << "The net pay for salaried employee: %.2f\n" << income(year) << endl;

另外，我需要使用程序中的至少一个函数来演示传值；并且至少是使用引用参数演示通过引用传递的函数之一。我不知道如何把它放在源代码中。有人帮忙吗？

Answer 1

由于income 函数未在Grosspay 类中定义，因此应在调用它们之前对其进行定义。尝试在 determineGrosspay 方法之前移动 income 的定义。

另一种解决方案是使用function prototype，方法是将原型移动到determineGrosspay 函数“之前”，然后再执行它。

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由于您在 cmets 中询问了按引用传递和按值传递，因此我将其包含在此答案中。您为income 函数编写的内容是按值传递。这意味着将变量的副本传递给函数。

通过引用传递意味着您将变量的引用传递给函数而不是它的副本。引用传递假定您的应用程序具有以下函数签名：income(const double &year) 如果您不想修改函数中的年份变量，income(double &year) 如果您想修改 year 的值。

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在您的应用程序中使用double income(const double &year)。

请研究一下这是什么意思，因为它是语言的重要组成部分。