如何使接受整数输入的while语句以特定方式响应非整数输入？

Question

我试图在一个简单的测试程序中创建一个while循环。此程序用于对用户输入的所有整数求和，并在用户按“a”后显示此和并退出循环。如果用户输入的不是整数或“a”，则程序用于响应“无效输入。请重试”，并允许用户输入其他数字。

我的程序成功地对整数求和，但如果输入了“a”以外的非整数，循环将结束，而不允许用户输入其他值。以if（！cin）开头的代码块似乎没有任何作用。

我认为问题出在（！ cin）而不是test=to_string（number）。是否有替代方法来检测允许此程序成功的非整数？

这是程序。一如既往地感谢您的帮助！

#include <iostream>
using namespace std;
#include <string>

int main()
{
int sum = 0;
int number;
string test;
cout << "Enter a series of integers; when you are done entering these integers, press a to display the sum of all integers.\n";
while (cin >> number)
{if (!cin)
    {
    test = to_string(number);
    if (test == "a")
        {break;}
    else 
        {cout << "Invalid input. Please try again.\n";
        continue;}
}
else 
{sum += number;}
}

cout << "The total sum is " << sum << ".\n";

}

Answer 1

这里有一个解决方案，它结合了PhillipSiedler的坎坷之路代码博客中的一个程序(https://bumpyroadtocode.com/2017/07/11/sum-of-integer-range/)Lakshmi使用了while（cin）

这似乎允许程序在输入“a”时中断，并在输入整数或“a”以外的内容时输入无效的输入消息并允许用户重试。

我有点搞不懂为什么。clear（）后接cin

 #include <iostream>
using namespace std;
#include <string>
//Solution borrows significantly from Philipp Siedler's solution for Chapter 5 Exercise 8 of Programming Practice and Principles: https://bumpyroadtocode.com/category/chapter-05-principles-and-practice-using-c/ 


int main()
{
int sum = 0;
int number;
string test;
cout << "Enter a series of integers; when you are done entering these integers, press a to display the sum of all integers.\n";

while (cin)
{
if (cin >> number)
{sum += number;}
else 
 {cin.clear();
    cin >> test;
    if (test == "a")
        {break;}
    else 
        {
        cout << "Invalid input. Please try again.\n";
        continue;}
  }

}

cout << "The total sum is " << sum << ".\n";


}

Answer 2

有关详细信息，请参阅内联注释：

#include <iostream>
using namespace std;
#include <string>

int main()
{
int sum = 0;
char ch; // Since we can't know whether user inputs an int or char
cout << "Enter a series of integers; when you are done entering these integers, press a to display the sum of all integers.\n";
while (cin) // Loop until user inputs
{
    cin >> ch;

if (isalpha(ch)) // Check if input is type char and handle as needed
{   
    if (ch == 'a')
        {
            break;
        }
    else 
        {
            cout << "Invalid input. Please try again.\n";
            std::cin.clear(); // Delete the current stream
            std::cin.ignore(32767,'\n'); // Revert back to previous input
            continue;
        }
}
else 
{
    sum += (ch - '0') % 48; // Since we are converting the char to int, handle it properly

}
}
cout << "The total sum is " << sum << ".\n";
}