如何让cin只取数字

How to make cin take only numbers(如何让cin只取数字)

问题描述

这是代码

double enter_number()
{
  double number;
  while(1)
  {

        cin>>number;
        if(cin.fail())
        {
            cin.clear();
            cin.ignore(numeric_limits<streamsize>::max(), '
');
            cout << "Invalid input " << endl;
        }
        else
        break;
        cout<<"Try again"<<endl;
  }
  return number;
}

我的问题是，当我输入 1x 之类的东西时，1 被当作输入，而没有注意到另一个运行时被遗漏的字符.有什么方法可以使它与任何实数一起使用，例如1.8?

My problem is that when I enter something like 1x, then 1 is taken as input without noticing the character that is left out for another run. Is there any way how to make it work with any real number e.g. 1.8?

推荐答案

我会使用 std::getline 和 std::string 读取整行然后仅当您可以将整行转换为双精度时才跳出循环.

I would use std::getline and std::string to read the whole line and then only break out of the loop when you can convert the entire line to a double.

#include <string>
#include <sstream>

int main()
{
    std::string line;
    double d;
    while (std::getline(std::cin, line))
    {
        std::stringstream ss(line);
        if (ss >> d)
        {
            if (ss.eof())
            {   // Success
                break;
            }
        }
        std::cout << "Error!" << std::endl;
    }
    std::cout << "Finally: " << d << std::endl;
}

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