c++ - Error when attempting to input strings into dynamically allocated array -

i'm trying code following program read single word per line text document, print same words text document, reason encountering rather large error after adding in:

for(int = 0; < num_lines; i++) {     getline (myfile_in, line);     stringstream(line) >> arr[i]; } 

im not sure why causing error because copied loop program wrote previously. error goes away once remove stringstream line, far i'm aware, need in order copy contents on array. appreciated :)

#include <fstream> #include <string> #include <sstream> #include <assert.h>  using namespace std;  int main(void) {    ifstream myfile_in; myfile_in.open ("words_in.txt"); ofstream myfile_out; myfile_out.open ("words_out.txt");  string line; int num_lines = 0; string *arr;  assert (!myfile_in.fail()); myfile_in >> line;  while (!myfile_in.eof()) {     getline (myfile_in, line);     num_lines++; }  arr = new string[num_lines];  for(int = 0; < num_lines; i++) {     getline (myfile_in, line);     stringstream(line) >> arr[i]; }  for(int = 0; < num_lines; i++) {     myfile_out << arr[i] << endl; }  myfile_in.close(); myfile_out.close(); return 0; } 

why not getline (myfile_in, arr[i]); ?