std :: cin的char造成无限循环 [英] std::cin of char causing infinite loop

问题描述

我使用cout语句之后，在切换之前，确定我有一个问题，第二个数字和字符操作，由于某种原因，我陷入无限循环！
我有一种感觉，我在语法上犯了一个小错误，但我不能弄清楚它是什么。

I've used the cout statement after the cin's before the switch to determine that I'm having a problem with the second number and the character op and for some reason I get into an infinite loop!!! I have a feeling that I'm making a small mistake in the syntax but I cant figure out what is it.

#include<iostream>
using namespace std;
int main()
{
    float a, b;
    char op, ans;
    do {
    cout << "Enter first number, operator, second number: ";
    cin >> a;
    cin >> b;
    cin >> op;
    cout << "first number is: " << a << "second number is: " << b << "operator is: " << op;
    switch (op) {
    case '/':
        cout << "answer = " << a / b << endl;
        break;
    case '*':
        cout << "answer = " << a * b << endl;
        break;
    case '+':
        cout << "answer = " << a + b << endl;
        break;
    case '-':
        cout << "answer = " << a - b << endl;
        break;
    }
    cout << "again? Y/N";
    cin >> ans;
    } while (ans != 'N' || ans != 'n');

    cout << endl;
    system("pause");
    return 0;
}

推荐答案

：

} while (ans != 'N' && ans != 'n');

不能同时为N和n。如果是这样的话，世界可能会消失在厄运的漩涡中。

It can't not be 'N' and 'n' simultaneously. If that were the case, the world would probably disappear into a vortex of doom.

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