【C++】【学习笔记】【005】输入输出小结

以你之姓@ 2022-08-13 17:47 108阅读 0赞

对输入数据进行合法性检查：cin对象有几个专门用来报告其工作情况的成员函数，它们将返回一个真/假值来表明cin的状态。

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   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:279px"> <span style="font-family:SimSun; font-size:18px">cin的成员函数</span></td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:279px"> <span style="font-family:SimSun; font-size:18px">作用</span></td> 
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     <span style="font-family:SimSun; font-size:18px">cin.eof()</span> 
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     <span style="font-family:SimSun; font-size:18px">如果到达文件（或输入）末尾，则返回true。</span> 
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     <span style="font-family:SimSun; font-size:18px">cin.fail()</span> 
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     <span style="font-family:SimSun; font-size:18px">如果cin无法工作，则返回true。</span> 
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     <span style="font-family:SimSun; font-size:18px">cin.bad()</span> 
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     <span style="font-family:SimSun; font-size:18px">如果cin因为比较严重的原因（例如：内存不足）而无法工作，则返回true。</span> 
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     <span style="font-family:SimSun; font-size:18px">cin.good()</span> 
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     <span style="font-family:SimSun; font-size:18px">如果以上情况都没有发生，则返回true。</span> 
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题目：写一个程序，向用户剔除一个“Y/N”问题，然后把用户输入的值付给answer变量。

要求：针对用户输入'Y'或'y'和‘N’或‘n’进行过滤。

#include <iostream>
    
    int main()
    {
        char answer;
        std::cout << "Do you like her?(Y/N)";
    
        while (1)
        {
            std::cin >> answer;
            if (answer != 'Y' && answer != 'y' && answer != 'N' && answer != 'n')
            {
                std::cout << "Input error. please input (Y/N).";
                continue;
            }
            else
            {
                break;
            }
        }
        std::cout << "Your input is: " << answer << std::endl;
    
        std::cin.ignore(100, '\n'); // 清空键盘缓冲区
        std::cin.get();
    
        return 0;
    }

题目：编写一个温度单位转换程序，提示用户以【xx.x C】或【xx.x F】的格式输入。

要求：如果用户输入的是32.4 C，程序将自动转换为90.32 F输出；反之，如果用户输入的是90.32 F，程序将自动转换为34.2 C输出。

// 温度单位转换
    // 华氏温度 = 摄氏温度 * 9.0 / 5.0 + 32
    // 摄氏温度 = (华氏温度 - 32) * 5.0 / 9.0
    
    #include <iostream>
    
    int main()
    {
        float num;
        char unit;
        const unsigned short ADD_SUBTRACT = 32;
        const double RATIO = 9.0 / 5.0;
        std::cout << "Please input degree. Format: [xx.x C] or [xx.x F]: ";
        while (1)
        {
            std::cin >> num >> unit;
            if (unit == 'C' || unit == 'c' || unit == 'F' || unit == 'f')
            {
                break;
            }
            std::cout << "Input error. Please input again.\n";
        }
        if ('C' == unit || unit == 'c')
        {
            num = num * RATIO + ADD_SUBTRACT;
            unit = 'F';
        }
        else
        {
            num = (num - ADD_SUBTRACT) / RATIO;
            unit = 'C';
        }
        std::cout << num << " F" << "\n";
        return 0;
    }