如何从文件 C++ 中读取带有科学计数法的浮点数？

Question

我有一个格式如下的文件：

-0.0064785667 0.73900002 0.028505694 4.7858757e-39 315 218
-0.0051828534 0.73900002 0.028505694 4.6936954e-39 316 218
-0.0038818798 0.73799998 0.028467119 5.1546736e-39 317 218
-0.0025879198 0.73799998 0.028467119 5.6160217e-39 318 218
-0.0012939599 0.73799998 0.028467119 6.4461411e-39 319 218

我用这段代码读过它：

using namespace std;   

ifstream inputFile;

//Opens data file for reading.
inputFile.open(filePath.c_str());

//Creates vector, initially with 0 points.
vector<Point> data(0);
float temp_x,temp_y,temp_z,rgb=0,discard_1=0,discard_2=0;

//Read contents of file till EOF.
while (inputFile.good()){

    inputFile >> temp_x >> temp_y >> temp_z >> rgb >> discard_1 >> discard_2;

    data.push_back(Point(temp_x,temp_y,temp_z,rgb));

}

if (!inputFile.eof())
    if (inputFile.fail()) cout << "Type mismatch during parsing." << endl;
    else cout << "Unknow problem during parsing." << endl;

//Close data file.
inputFile.close();

读取科学记数法浮点数会导致类型不匹配。

如何读取所有数字，包括科学记数法浮点数？

Answer 1

问题可能是你的while循环。永远不要使用while(inputFile.good())。使用这个：

while (inputFile >> temp_x >> temp_y >> temp_z 
                 >> rgb >> discard_1 >> discard_2) {}

This answer 到另一个问题解释了原因。您可能还对this answer 感兴趣，它提出了一个更优雅的解决方案。

Answer 2

在Björn Pollex's answer 上扩展一个示例没有任何错误处理：

#include <iostream>
#include <fstream>
#include <iterator>
#include <vector>

struct point
{
    double x, y, z, rgb;
};

struct point_line: public point
{
    int discard[2];
};

std::istream& operator >>(std::istream& is, point_line& in)
{
    is >> in.x >> in.y >> in.z >> in.rgb >> in.discard[0] >> in.discard[1];
    // TODO: Add your error-handlin

    return is;
}

std::ostream& operator <<(std::ostream& os, const point& out)
{
    os << " X: " << out.x
       << " Y: " << out.y
       << " Z: " << out.z
       << " RGB: " << out.rgb
       ;

    return os;
}

int main()
{
    std::ifstream points_file("points.txt");
    std::vector<point> points;
    std::copy(std::istream_iterator<point_line>(points_file),
              std::istream_iterator<point_line>(),
              std::back_inserter(points));

    std::copy(points.begin(),
              points.end(),
              std::ostream_iterator<point>(std::cout, "\n"));
}