Question

i have a problem with reading from a file, and converting content to double. I have read the solutions from stackoverflow but nothing works.

i have this input file:

1291.23
291.493
558.089
309.266
513.656
491.44
429.234
851.345
589.192
535.873
802.469
713.604
1002.42
997.973
513.656
313.709
407.018
624.738
460.337
526.986
473.667
1202.36

and the program:

#include <math.h> 
#include <string> 
#include <iostream> 
#include <fstream> 
#include <stdio.h> 
#include <sstream> 

using namespace std; 
void main() { 
    char* filename = "mr1.txt"; 
    ifstream fin; 
    fin.open(filename); 
    float d;// = 0.0; 
    int v = 0; 
    while (v < 21){ 
        fin>>d; 
        if(v >= 2 || v < 15){ 
            cout<<d<<endl;
        } 
        v++; 
    } 
}

the output is: 1291 for 12 times

How can i convert from these file to double without problem? Thanks!

Answer 1

As a quick sanity check, try just copying the entire file to standard output, something like this:

#include <iostream>
#include <iterator>
#include <algorithm>

int main() {    
    std::ifstream in("mr1.txt");
    std::copy(std::istream_iterator<double>(in),
              std::istream_iterator<double>(),
              std::ostream_iterator<double>(std::cout, "\n"));
    return 0;
}