#include <iostream>
#include <fstream>
#include <string>
using namespace std;
 
int main ()
{
   string line;
   ifstream infile("test_file.txt");
   while ( getline(infile, line) )
   {
      cout << line << endl;
   }
   return 0;
}

#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
#include <vector>
using namespace std;
 
int main()
{
   vector < vector < double > > info;
   ifstream file("file.txt");
   string line;
   while ( getline(file, line) )
   {
      vector < double > data;
      double value;
      istringstream iss(line);
      while (iss >> value)
      {
         data.push_back(value);
      }
      info.push_back(data);
   }
   for ( vector < vector < double > > :: size_type i = 0, size = info.size(); i < size; ++i)
   {
      cout << "line " << i + 1 << ": ";
      for ( vector < double > :: size_type j = 0, length = info[i].size(); j < length; ++j)
      {
         cout << info[i][j] << " ";
      }
      cout << endl;
   }
   return 0;
}
 
/* file.txt
1 2 3
4 5 6 7 8 9
10 11 12 13
14
15 16
*/
 
/* my output
line 1: 1 2 3
line 2: 4 5 6 7 8 9
line 3: 10 11 12 13
line 4: 14
line 5: 15 16
*/