c++ - 如何正确使用 cin.clear 和 cin.ignore

Question

    int main()
{
    int oddeven = 1;
    int modulotwo;
    // Simple loop since no reason to check 0
    while(oddeven != 0){
        //user input
        cout << "\n\nIn while loop\n";
        cout << "Input number to determine if it is odd or even.\n";
        cin >> oddeven;
        //check to see if input succesful
        if(!(cin.fail())) {
            cout << "In if loop\n";
            cout << "Divide by two and put in modulotwo.\n";
            //check to see if odd or even by dividing by 2
            modulotwo = oddeven % 2;
            cout << "Output modulotwo: ";
            //visual confirmation of remainder
            cout << modulotwo << "\n";
            if (modulotwo == 0) {
                cout << "Check modulotwo against 0\n";
                cout << "The number " << oddeven << " is even.\n";

            }
            else {
                cout << "The number " << oddeven << " is odd.\n";

            }
        }
        //If input not succesful
        else {
            cout << "In else statement. Set oddeven to 1\n";
            //set oddeven to 1 to stop exit
            oddeven = 1;
            cout << "Not a usable number, please input integer number." << endl;
            cout << "Run cin.clear\n";
            cin.clear();
            cout << "Run cin.ignore\n";
            cin.ignore(std::numeric_limits<std::streamsize>::max());

        }
    }

}

我在上面有一个“简单”的代码来检查数字是奇数还是偶数。我正在尝试向其添加纠错以确保输入的类型正确。我被指向 cin.clear 和 cin.ignore。我的问题是，如果我导致错误，它会正确地放入 else 语句中，仅此而已。它将不再运行其余部分。我假设它来自 cin.ignore。如何让它正确清除错误并返回输入循环？如果我删除 cin.ignore，我会得到一个连续的循环，告诉我 1 是奇数，而无需等待任何输入。

额外的输出文本是我尝试跟踪代码的位置和作用的方式。

编辑。在发帖之前，我实际上已经将 cin.ignore 注释掉了。我试图自己研究这个问题并且遇到了关于它寻找换行符的评论，但正如你们都发现的那样，它不起作用。输入字母而不是任何数字时会出现问题，无论是太大还是其他。

Answer 1

My issue is, if I cause an error it correctly drops into the else statement, but that is it. It will no longer run the rest.

问题出在线路上

cin.ignore(std::numeric_limits<std::streamsize>::max(), "\n");

第二个参数需要是一个字符，而不是一个字符串。

cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');

提高编译器的警告级别以检测此类错误。

通过使用 g++ -std=c++11 -Wall，我收到以下警告/错误消息。

socc.cc: In function ‘int main()’:
socc.cc:43:70: error: invalid conversion from ‘const char*’ to ‘std::basic_istream<char>::int_type {aka int}’ [-fpermissive]
          cin.ignore(std::numeric_limits<std::streamsize>::max(), "\n");
                                                                      ^
In file included from /usr/include/c++/5/iostream:40:0,
                 from socc.cc:1:
/usr/include/c++/5/istream:657:5: note:   initializing argument 2 of ‘std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::ignore(std::streamsize, std::basic_istream<_CharT, _Traits>::int_type) [with _CharT = char; _Traits = std::char_traits<char>; std::streamsize = long int; std::basic_istream<_CharT, _Traits>::int_type = int]’
     basic_istream<char>::