为什么 cin 不在 for 循环内执行？

Question

#include <iostream>
#include <vector>
using namespace std;
typedef vector<double> vec;                    //vec now acts like a datatype
int main()
{
    vec powers;                                //stores powers of x in the objective function
    vec coefficients;                          //stores coefficients of x in the objective function
    double pow;
    double coeff = 0;
    cout << "Enter powers of x present in the objective function and enter any character to stop" << endl;
    cout << "REMEMBER TO ENTER 0 IF CONSTANT EXISTS!" << endl;
    while (cin >> pow)
        powers.push_back(pow);                //Working fine
    cout << endl;
    for (vec::iterator iter_p = powers.begin(); iter_p != powers.end(); iter_p++)
    {
        double coeff;
        cout << "Enter coefficient of the (x^" << *iter_p << ") term: ";
        cin >> coeff;                          //THIS IS NOT EXECUTING
        coefficients.push_back(coeff);         //NOT WORKING EITHER
    }
    cout << endl;
    return 0;
    system("pause");
}

我想输入多项式方程的幂和系数。我能够将权力存储在向量中。但是在我用来输入系数的 for 循环中，cin 根本没有执行。如果有人能找出导致跳过 cin 语句的确切原因，我将不胜感激。

Answer 1

这里的问题是你告诉用户输入一个字符来结束

while (cin >> pow)
    powers.push_back(pow);

虽然这有效，但它也会使 cin 处于错误状态并将字符留在缓冲区中。您需要清除该错误状态并删除输入中留下的字符。您可以通过添加

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

在 while 循环之后。 clear 清除错误，忽略输入中的所有字符。

为什么 cin 不在 for 循环内执行？

Why is cin not executing inside for loop?

c++

for-loop

cin