C++ 指定来自 istream 的输入并测试它

Question

我有一个基本上表示元组(双 x，双 y)的类，我已经重载了 << 运算符，所以我可以打印该类。现在我想对 >> 做同样的事情，所以它只支持以下格式:x, (x) 和 (x,y)。

我有以下代码:

std::ostream & operator<< (std::ostream &output, tuple &c){
    output << "(" << c.x << "," << c.y << ")" << endl;
    return output;
}

std::istream & operator>> (std::istream & input, tuple &c){
    // Check for following patterns: x, (x) or (x,y)
}

我可以遍历输入和正则表达式匹配吗？那怎么办呢？另外我怎么能测试它是否真的有效，就像这样 std::cin >> "(10.2,5.5)"
还是我需要从文件中读取以进行测试？

编辑:给出的答案确实解决了这个问题，但我想添加一种方法来测试它，因为它可能会使用除我以外的其他人:

tuple x(6,2);
stringstream ss;
ss << x;
ASSERT_EQUALS(ss.str(), "(6,2)\n");

Answer 1

正则表达式对于像这样的简单输入任务来说是不必要的。以下是我的做法，不检查输入是否有效，只是解析:

std::istream & operator>> (std::istream & input, tuple &c){
    // Check for following patterns: x, (x) or (x,y)
    char firstCharacter;
    input >> firstCharacter; // See what the first character is, since it varies

    if (firstCharacter == '(')
    {   // The simplest case, since the next few inputs are of the form n,n)
        char delimiters;
        input >> c.x >> delimiters >> c.y >> delimiters;
        //        N        ,           N        )
        // You also here have to check whether the above inputs are valid, 
        // such as if the user enters a string instead of a number
        // or if the delimeters are not commas or parentheses
    }
    else if (isdigit(firstCharacter) || firstCharacter == '-')
    {   //                               For negative numbers
        char delimiters;
        input.unget(); // Put the number back in the stream and read a number
        input >> c.x >> delimiters >> delimiters >> c.y >> delimiters;
        //        N           ,         (            N          )
        // You also here have to check whether the above inputs are valid, 
        // such as if the user enters a string instead of a number
        // or if the delimeters are not commas or parentheses
    }
    else
    { 
        // Handle some sort of a parsing error where the first character 
        // is neither a parenthesis or a number
    }

    return input;
}