Question

当我声明int weight然后输入双值165.1时，第二个cin >> height;不起作用，并且没有任何错误消息。你能告诉我为什么吗？

使用VS2010控制台应用程序。

#include <iostream>

using namespace std;

const double lbs_to_kg = 2.2046, inches_to_meter = 39.370;

int main()
{
    int weight, height;
    double kilograms, meters;

    cout << "\nEnter weight in pounds: ";
    cin >> weight;
    kilograms = weight / lbs_to_kg;
    cout << "\nEnter height in inches: ";
    cin >> height;
    meters = height / inches_to_meter;
    cout << "\nYour BMI is approximately "
        << "\nbody fat ratio is "
        << kilograms / (meters * meters)
        << ". Under 25 is good."
        << endl;

}

output:

Enter weight in pounds: 165.1

Enter height in inches:
Your BMI is approximately
body fat ratio is 1.57219e-013. Under 25 is good.

Answer 1

如果您尝试将cin数据提取到无法保存的变量中，则数据会保留在输入流中，并且cin会被标记为失败。您需要使用!cin检查它是否失败，并使用cin.clear()清除失败标志，以便您可以再次读取（将来的提取操作将自动失败，直到标志被清除）。您可以将数据提取到能够容纳它的另一个变量中，或者使用cin.ignore()将其丢弃

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