c-按值传递和按引用传递

我正在开发一个项目,该项目通过使用超载为员工计算收入,并且还通过引用传递值.我需要使用程序中的至少一个函数来演示传递值；以及至少一个用于演示带有引用参数的引用传递的功能.这是到目前为止我得到的：

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

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: " << grosspay << endl;

    federaltax = grosspay * .10;
    cout << "Federal Tax is: " << federaltax << endl;

    statetax = grosspay * .05;
    cout << "State Tax is: " << statetax << endl;

    totaltax = federaltax + statetax;
    cout << "Total tax is: " << totaltax << endl;

    netpay = grosspay - totaltax;
    return (netpay);

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

    grosspay = year / 52;
    cout << "Grosspay weekly is: " << grosspay << endl;

    federaltax = grosspay * .10;
    cout << "Federal Tax is: " << federaltax << endl;

    statetax = grosspay * .05;
    cout << "State Tax is: " << statetax << endl;

    totaltax = federaltax + statetax;
    cout << "Total Tax is: " << totaltax << endl;

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

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: " << ID << endl;
            cout << setprecision(2) << fixed;
            cout << "The net pay for hourly employee: " << income(hours, payrate) << endl;
            break;
        case 2:
            cout << "Enter employee ID: " << endl;
            cin >> ID;
            cout << "Enter salary: " << endl;
            cin >> year;

            cout << "Employee ID: " << ID << endl;
            cout << setprecision(2) << fixed;
            cout << "The net pay for salaried employee: " << income(year) << endl;
            break;
        case 3:
            cout << "Exited program" << endl;
            break;
        default:
            cout << "Please try again!" << endl;
            break;
        }
    }
}

这里的一位天才告诉我,我需要将双倍收入(const double& year)作为转介参考.但是我不太确定到底有什么区别！我仍然有相同的输出.谁能帮帮我吗？

解决方法:

以下是一些准则：

>如果值适合处理器的寄存器和
该参数将不会被修改.
>如果功能会修改参数,则按引用传递.
>如果对象大于
处理器的寄存器和参数将不会被修改.

对double,float,int,char和bool之类的类型传递常量引用没有意义,因为它们通常适合处理器的字长.编译器将尝试将这些值传递到寄存器中.这些POD类型没有额外的复制成本.因此,按值传递(需要较少的键入).

标签：c,pass-by-reference,pass-by-value
来源： https://codeday.me/bug/20191012/1898435.html