Thread: parsing in c++

Code:

// reading a text file
#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main () {
  string line;
  ifstream myfile ("example1.txt");
  ofstream myargument ("putonqueue.txt",ios::out | ios::app);
  if (myfile.is_open())
  {
    while (! myfile.eof() )
    {
	 // expects either space-delimited numbers 
    
    
    while( getline(myfile,line) ) {
     
        istringstream ss (line);
        double d;
        while( ss >> d ) {
          cout << "  got a number: " << d << endl;
        }
      }
 }
    myfile.close();
    myargument.close();
  }

  else cout << "Unable to open file"; 

  return 0;
}

Hi I am trying to parse a text file in c++.The above code gives a compiler error:
argque.cpp: In function `int main()':
argque.cpp:20: error: variable `std::istringstream ss' has initializer but incomplete type

what does it mean?
any help or insight is appreciated.
Thanks
shweta