when running the following code, the amount of lines will read on less then there actually is (if the input file is main itself, or otherwise) why is this and how can i change that fact (besides for just adding 1)?

#include <fstream>
#include <iostream>
#include <string>
#include <vector>

using namespace std;

int main()
{
    // open text file for input
    string file_name;

    cout << "please enter file name: ";
    cin  >> file_name;

    // associate the input file stream with a text file
    ifstream infile(file_name.c_str());

    // error checking for a valid filename
    if ( !infile ) {
        cerr << "Unable to open file "
             << file_name << " -- quitting!\n";
        return( -1 );
        }
        else cout << "\n";

    // some data structures to perform the function
    vector<string> lines_of_text;
    string textline;

    // read in text file, line by line
    while (getline( infile, textline, '\n' ))   {
        // add the new element to the vector
        lines_of_text.push_back( textline );

        // print the 'back' vector element - see the STL documentation
        cout << "line read: " << lines_of_text.back() << "\n";
    }
cout<<lines_of_text.size();
    return 0;
}