如何使用cin.fail()编写函数以确保main中的有效输入? [英] how to write a function using cin.fail() to ensure valid input in main?

问题描述

部分要求是该函数不应带有任何参数.但是问题是我可以在哪里存储cin输入?我在这里遇到了无限循环.

Part of the requirement is that the function should not take any arguments. But the problem is that where can I store the cin input? I got an infinite loop here.

double getValidDouble(){
    string invalid_input;
    while (cin.fail()){
        cout << "You entered a value of the wrong type!" << endl;
        getline(cin,invalid_input);
        cout << "Enter a double this time: " << endl;  
    }
}

推荐答案

也许我并不完全关注，但是为什么不声明局部变量并返回它呢?

Maybe I'm not totally following but why not just declare a local variable and return it?

double getValidDouble(){
    string invalid_input;
    double val;
    cin >> val;
    while (cin.fail()){
        cout << "You entered a value of the wrong type!" << endl;
        cin.clear();
        getline(cin,invalid_input);
        cout << "Enter a double this time: " << endl;  
        cin >> val;
    }
    return val;
}

无限循环可能是由于您在错误发生后未执行 cin.clear()而引起的.

Infinite loop is probably due to you not doing cin.clear() after the error.

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