我的计算器出了问题

Question

我是C ++的新手。我的第一个目标是使一个成功的计算器程序成为Win32控制台应用程序，但我一直收到错误。我把这段代码：

cout << "Do you want to continue? N/Y" << endl;
cin  >> ny;

if (ny == "Y") goto start;
if (ny == "N") goto end;

但它继续以任何方式结束。

这是'结束'的代码：

// End - Properties
system("cls");
system("title Basic Calculator -  End");
system("color 4F");

// End - Start
ny == "0";
cout << "Are you sure you want to end? N/Y" << endl;
cin  >> ny;

if (ny == "N") goto start;

cin.get();

return 0();

最后它也总是结束程序。

如果您发现错误，请告诉我。

-Danish Humair

完整代码：

#include <iostream>

using namespace std;

int main()
{
start:
    // Program - Properties
    system("cls");
    system("title Basic Calculator - Main Screen");
    system("color 1F");

    // Program - Setup
    int input;
    int x;
    int y;
    char ny [10];

    // Program - Start
    cout << "Please choose an operation from the following." << endl << endl;
    cout << "1. Addition \n2. Subtraction \n3. Multiplication \n4. Division" <<endl << endl;
    cin  >> input;
    if (input = 1) goto addition;
    if (input = 2) goto subtraction;
    if (input = 3) goto multiplication;
    if (input = 4) goto division;
    cin.get();

addition:

    // Addition - Properties
    system("cls");
    system("title Basic Calculator - Addition");
    system("color 2F");

    // Addition - Start
    cout << "Please input your first number." << endl;
    cin  >> x;
    cout <<endl << "Please input your second number."<< endl << endl;
    cin  >> y;
    cout <<endl <<endl << "The answer is " << x+y << ".\a" << endl << endl;
    cout << "Do you want to continue? N/Y" << endl;
    cin  >> ny;

    if (ny == "Y") goto start;
    if (ny == "N") goto end;

    cin.get();

subtraction:

multiplication:

division:

end:
    // End - Properties
    system("cls");
    system("title Basic Calculator -  End");
    system("color 4F");

    // End - Start
    ny == "0";
    cout << "Are you sure you want to end? N/Y" << endl;
    cin  >> ny;

    if (ny == "N") goto start;

    cin.get();

    return 0();
}

Answer 1

需要解决一些问题。

1）声明ny为std::string ny;您需要添加#include <string>。这样可以避免缓冲区溢出。

2）如前所述，您需要更改if语句。

if (input == 1) goto addition;  // Use '==' for comparison
if (input == 2) goto subtraction;
if (input == 3) goto multiplication;
if (input == 4) goto division;    

3）确保检查小写y和n

if (ny[0] == 'Y' || ny[0] == 'y') goto start;  // notice the single quotes
if (ny[0] == 'N' || ny[0] == 'n') goto end;  

// ...
// Also change the following
ny[0] = '\0';  // Not really necessary since you assign it immediately after
// ...
if (ny[0] == 'N' | ny[0] == 'n')

4）您的return声明不正确。将其更改为：

return 0;  // Doesn't need parenthesis

作为一名专业程序员，我必须建议您不要使用goto语句并将算法封装在函数中。以下是基于原始代码的示例。仅供参考，我已经验证它在Visual Studio 2010专业版上编译

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

// Forward declarations
void addition();
void subtraction();
void multiplication();
void division();

int main()
{
    bool again = true;

    // Program - Setup
    int input;
    std::string ny;

    while(again)
    {
        // Program - Properties
        system("cls");
        system("title Basic Calculator - Main Screen");
        system("color 1F");

        // Program - Start
        cout << "Please choose an operation from the following." << endl << endl;
        cout << "1. Addition \n2. Subtraction \n3. Multiplication \n4. Division" <<endl << endl;
        cin  >> input;
        cin.get();

        if (input == 1) {addition();}
        else if (input == 2) {subtraction();}
        else if (input == 3) {multiplication();}
        else if (input == 4) {division();}
        else 
        {
            cout << "Invalid input\n"; 
            again = false;
        }

        cout << "Do you want to continue? N/Y" << endl;
        cin  >> ny;
        cin.get();

        if (ny[0] == 'Y' || ny[0] == 'y')
        {
            again = true;    
        }
        else
        {
            // Ask if they are sure
            system("cls");
            system("title Basic Calculator -  End");
            system("color 4F");

            cout << "Are you sure you want to end? N/Y" << endl;
            cin  >> ny;
            cin.get();

            if (ny[0] == 'Y' || ny[0] == 'y')
            {
                again = false; 
            }
            else
            {
                again = true;
            }
        }
    }

    return 0;
}

void addition()
{
    int x;
    int y;
    // Addition - Properties
    system("cls");
    system("title Basic Calculator - Addition");
    system("color 2F");

    // Addition - Start
    cout << "Please input your first number." << endl;
    cin  >> x;
    cout <<endl << "Please input your second number."<< endl << endl;
    cin  >> y;
    cout <<endl <<endl << "The answer is " << x+y << ".\a" << endl << endl;
}

void subtraction()
{

}

void multiplication()
{

}

void division()
{

}

Answer 2

if（input = 1）goto addition

我认为你应该检查（输入== 1），但是你将它分配给输入（输入= 1）。

代码应该是： -

if (input == 1) goto addition;
if (input == 2) goto subtraction;
if (input == 3) goto multiplication;
if (input == 4) goto division;

Answer 3

我做了一些改动，  1）声明ny为字符而不是数组。  2）检查小写和大写字母。

无论我做了哪些更改，我都添加了评论。 我希望这会有所帮助。

    // #include "stdafx.h" //If you get error include this
    #include <iostream>

    using namespace std;

    int main()
    {
    start:
        // Program - Properties
        system("cls");
        system("title Basic Calculator - Main Screen");
        system("color 1F");

        // Program - Setup
        int input;
        int x;
        int y;
        char ny;  //Dont declare it as array ny[10]

        // Program - Start
        cout << "Please choose an operation from the following." << endl << endl;
        cout << "1. Addition \n2. Subtraction \n3. Multiplication \n4. Division" <<endl << endl;
        cin  >> input;
        if (input == 1) goto addition;
        if (input == 2) goto subtraction;
        if (input == 3) goto multiplication;
        if (input == 4) goto division;
        cin.get();

    addition:

        // Addition - Properties
        system("cls");
        system("title Basic Calculator - Addition");
        system("color 2F");

        // Addition - Start
        cout << "Please input your first number." << endl;
        cin  >> x;
        cout <<endl << "Please input your second number."<< endl << endl;
        cin  >> y;
        cout <<endl <<endl << "The answer is " << x+y << ".\a" << endl << endl;
        cout << "Do you want to continue? N/Y" << endl;
        cin  >> ny;

        if (ny == 'Y'|| ny == 'y') goto start;   //Check for both Y & y
        if (ny == 'N' || ny == 'n') goto end;    //Check for both N & n

        cin.get();

    subtraction:

    multiplication:

    division:

    end:
        // End - Properties
        system("cls");
        system("title Basic Calculator -  End");
        system("color 4F");

        // End - Start

        cout << "Are you sure you want to end? N/Y" << endl;
        cin  >> ny;

        if (ny == 'N' || ny == 'n') goto start;

        cin.get();

        return 0;
    }

Answer 4

除了1）和3）之外，所有事情都是jmstoker说的。而是将代码更改为

if (ny[0] == 'Y') goto start;
if (ny[0] == 'N') goto end;

至少在我的编译器（Microsoft Visual C ++ 2011 Express）中起作用

这是完整的代码

#include <iostream>

using namespace std;

int main()
{
start:
    // Program - Properties
    system("cls");
    system("title Basic Calculator - Main Screen");
    system("color 1F");

    // Program - Setup
    int input;
    int x;
    int y;
    char ny [10];

    // Program - Start
    cout << "Please choose an operation from the following." << endl << endl;
    cout << "1. Addition \n2. Subtraction \n3. Multiplication \n4. Division" <<endl << endl;
    cin  >> input;
    if (input == 1) goto addition;
    if (input == 2) goto subtraction;
    if (input == 3) goto multiplication;
    if (input == 4) goto division;
    cin.get();

addition:

    // Addition - Properties
    system("cls");
    system("title Basic Calculator - Addition");
    system("color 2F");

    // Addition - Start
    cout << "Please input your first number." << endl;
    cin  >> x;
    cout <<endl << "Please input your second number."<< endl << endl;
    cin  >> y;
    cout <<endl <<endl << "The answer is " << x+y << ".\a" << endl << endl;
    cout << "Do you want to continue? N/Y" << endl;
    cin  >> ny;

    if (ny[0] == 'Y') goto start;
    if (ny[0] == 'N') goto end;

    cin.get();

subtraction:

multiplication:

division:

end:
    // End - Properties
    system("cls");
    system("title Basic Calculator -  End");
    system("color 4F");

    // End - Start
    cout << "Are you sure you want to end? N/Y" << endl;
    cin  >> ny;

    if (ny[0] == 'N') goto start;

    cin.get();

    return 0;
}