如何在 C++ 中将用户输入验证为双精度值? [英] how do I validate user input as a double in C++?

问题描述

我如何检查输入是否真的是双精度的?

How would I check if the input is really a double?

double x;

while (1) {
    cout << '>';
    if (cin >> x) {
        // valid number
        break;
    } else {
        // not a valid number
        cout << "Invalid Input! Please input a numerical value." << endl;
    }
}
//do other stuff...

上面的代码无限输出Invalid Input! 语句，所以它不会提示另一个输入.我想提示输入，检查它是否合法......如果它是双重的，继续......如果它不是双重的，再次提示.

The above code infinitely outputs the Invalid Input! statement, so its not prompting for another input. I want to prompt for the input, check if it is legitimate... if its a double, go on... if it is NOT a double, prompt again.

有什么想法吗?

推荐答案

试试这个:

while (1) {
  if (cin >> x) {
      // valid number
      break;
  } else {
      // not a valid number
      cout << "Invalid Input! Please input a numerical value." << endl;
      cin.clear();
      while (cin.get() != '
') ; // empty loop
  }
}

这基本上会清除错误状态，然后读取并丢弃上一行输入的所有内容.

This basically clears the error state, then reads and discards everything that was entered on the previous line.

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