Question

你好我在C ++上划分两个双打有问题，在基本的C ++上运行正常，例如

double DfirstNumber = 4.3;
double DsecondNumber = 2.0;
double DthirdNumber = DfirstNumber/DsecondNumber;
std::cout << DthirdNumber;

但不在下面的代码中：

    #include <iostream>
    #include <fstream>
    #include <string>
    #include <Windows.h>
    #include <regex>
    std::string getLastLine(std::ifstream& in)
    {
        std::string line;
        while (in >> std::ws && std::getline(in, line)) // skip empty lines
            ;

        return line;
    }

    int main()
    {
        double DfirstNumber;
        double DsecondNumber;
        while(true){
            std::ifstream file("C:\\Users\\Admin\\Documents\\myfile.txt");

            if (file)
            {
                std::string line = getLastLine(file);
                Sleep(1000);
                try {
                    std::regex re("\\d*\\.\\d*");
                    std::sregex_iterator next(line.begin(), line.end(), re);
                    int i = 0;
                    std::string firstNumber;
                    std::string secondNumber;
                    while (i < 3) {
                        std::smatch match = *next;
                        if (i == 1) {
                            firstNumber = match.str();
                            DfirstNumber = std::stof(firstNumber);
                        }
                        if (i == 2) {
                            secondNumber = match.str();
                            DsecondNumber = std::stof(secondNumber);
                        }
                        next++;
                        i++;
                    }
                }
                catch (std::regex_error&) {
                    std::cout << "regex error";
                }
                double DthirdNumber = DsecondNumber) / DfirstNumber;
                std::cout << DthirdNumber << std::endl;
            }
            else{
                std::cout << "Can't Open the file.\n";
            }
        }
    }

我每秒都会在myfile.txt上获得一个新行，所以我必须检查文件的最后一行，然后使用正则表达式获取所需的数据并将它们存储到C ++变量中。

这就是myfile.txt的外观

Hello Name Name0.00042Surname NameSurname Name0.00042$100.03
Hello Name Name0.00143Surname NameSurname Name0.00143$100.53
Hello Name Name0.00342Surname NameSurname Name0.00342$100.32
..............................................^1stNr^.^2ndNr^
... and another program just continues to extract lines like these  every second!

有人可以向我解释为什么会发生这种情况，因为如果我试图分裂的话 DfirstNumber = 407.33 DsecondNumber = 0.015982 我没有收到25486.79764735327，但我收到25489.8

为什么在C ++上划分两个双打并没有显示正确的结果？

0 个答案: