输入字符时 cin 跳过

Question

我有一个程序，我必须输入两个双精度数，并且必须在字符“|”时终止被输入。但是，当我输入字符 '|' cin 被跳过，程序将直接运行而不会阻塞。插入字符后如何终止程序？

我的代码是：

#include "std_lib_facilities.h"

int main()
{
    bool start = true;
    while(start)
    {
        double number1, number2 = 0;
        cout << "Enter two doubles\n";
        cin >> number1 >> number2;

        if((number1 == double{'|'}) || (number2 == double{'|'}))
        {
            start = false;
        }

        cout << "The value of number1 is: " << number1 << '\n';
        cout << "The value of number2 is: " << number2 << '\n';
    }
    return 0;
}

Answer 1

您无法将| 字符读入double 变量。 operator>> 将无法提取数字并将在流上设置failbit，您可以对其进行测试，例如：

#include "std_lib_facilities.h"

int main()
{
    do
    {
        double number1, number2;

        cout << "Enter two doubles\n";
        if (!(cin >> number1 >> number2))
            break;

        cout << "The value of number1 is: " << number1 << '\n';
        cout << "The value of number2 is: " << number2 << '\n';
    }
    while (true);

    return 0;
}

否则，首先将输入读取为字符串，然后根据需要验证格式，例如：

#include "std_lib_facilities.h"
#include <string>

int main()
{
    do
    {
        std::string input1, input2;
        double number1, number2;

        cout << "Enter two doubles\n";
        if (!(cin >> input1 >> input2))
            break;

        if ((input == "|") || (input2 == "|"))
            break;

        number1 = std::stod(input1);
        number2 = std::stod(input2);

        cout << "The value of number1 is: " << number1 << '\n';
        cout << "The value of number2 is: " << number2 << '\n';
    }
    while (true);

    return 0;
}

Answer 2

首先，您需要了解 C++ 中的数据类型和字符串。 其次，考虑讲座，为您的输入选择合适的类型。 这样的事情应该可以解决您的问题：

#include "std_lib_facilities.h"
int main()
{
  bool start = true;

 while(start)
  {
    double number1=0, number2 = 0;//here you were initializing only number2 to 0
    cout << "Enter two doubles\n";
    char condition;

    cin >> number1 >> number2;
    cin>>condition;//to continue reading doubles give it something different from |

    if(condition == '|')
     {
      start = false;
     }
    cout << "The value of number1 is: " << number1 << '\n';
    cout << "The value of number2 is: " << number2 << '\n';
  }
 return 0;
}

Answer 3

double 是一种内置数据类型，用于保存从 2.3E-308 到 1.7E+308（包括小数点数字）的数字。另一方面，垂直斜杠（|）是一个字符。 char 可以容纳任何单数字符（例如：'a'、'7'、'#'、'|' 等）。您试图在程序中输入双精度数据类型的字符，这是不可接受的。使用 char 数据类型而不是 double。

//Using char
#include<iostream>

int main() {
    bool start = true;

    while(start) {
        char number1, number2;
        std :: cout << "Enter two characters\n";
        std :: cin >> number1 >> number2;

        if((number1 == '|') || (number2 == '|'))
            start = false;

        std :: cout << "The value of number1 is: " << number1 << std :: endl;
        std :: cout << "The value of number2 is: " << number2 << std :: endl;
    }
    return 0;
}

这里的“number1”和“number2”可以存储单数、字母或特殊字符。如果您想存储双精度字符和字符，请尝试使用“std :: string”而不是 char。

//Using string
#include<iostream>
    
    int main() {
        bool start = true;
        
         while(start) {
            std :: string number1, number2;
            std :: cout << "Enter two characters\n";
            std :: cin >> number1 >> number2;
    
            if((number1 == "|") || (number2 == "|"))
                start = false;
    
            std :: cout << "The value of number1 is: " << number1 << std :: endl;
            std :: cout << "The value of number2 is: " << number2 << std :: endl;
        }
        return 0;
    }