c++ - 为什么这个简单的逻辑不起作用？

Question

我只是想不通为什么 while 循环中的这个简单逻辑不起作用。

基本上这个函数的作用是，它接受一个参数，并在 while 循环中检查它是否不是"is"或“否”，然后继续循环。

void getAnswer(string answer) {

    string newAnswer = "";
    newAnswer = answer;
    while (newAnswer != "Yes" || newAnswer != "yes" || newAnswer != "Y" || newAnswer != "y" || newAnswer != "No" || newAnswer != "no") {
            cout << "Enter yes or no.." << endl;
            cin >> newAnswer;

        }

        if (newAnswer == "Yes" || newAnswer == "yes" || newAnswer == "Y" || newAnswer == "y") {
            chooseOptions();
        } else {
            cout << "Bye See you again " << endl;
            exit(1);
        } 
}

但即使我输入“yes”或“no”，它仍然会循环。

Answer 1

De Morgan's laws声明:

"not (A and B)" is the same as "(not A) or (not B)"

根据您的情况应用此法律:

newAnswer != "Yes" || newAnswer != "yes" || ...

⇔

!(newAnswer == "Yes" && newAnswer == "yes" && ...)

现在更容易看出错误的原因。

如果 newAnswer 不是“Yes”或“yes”，它将被评估为 true，这不是您想要的。

解决方案是将 || 更改为 &&。