getline item returning empty variable - c++

Question

I'm trying to read in a text file and separate the lines into cities and locations. Everything is working for most of the lines, but for I'm getting a
terminate called after throwing and instance of 'std::invalid_argument'
what(): stoi
Aborted (core dumped)
After some investigating, I figured out that it's hanging up on the 2 in Lima, Peru. I could be that the getline function is giving it something it can't handle, but there are instances of exactly the same number in exactly the same position earlier in the document.
...
Hobart, Tasmania: 42 52 S 147 19 E
Hong Kong, China: 22 20 N 114 11 E
Iquique, Chile: 20 10 S 70 7 W
Irkutsk, Russia: 52 30 N 104 20 E
Jakarta, Indonesia: 6 16 S 106 48 E
Johannesburg, South Africa: 26 12 S 28 4 E
Kingston, Jamaica: 17 59 N 76 49 W
Kinshasa, Congo: 4 18 S 15 17 E
Kuala Lumpur, Malaysia: 3 8 N 101 42 E
La Paz, Bolivia: 16 27 S 68 22 W
Leeds, England: 53 45 N 1 30 W
Lima, Peru: 12 0 S 77 2 W
Lisbon, Portugal: 38 44 N 9 9 W
Liverpool, England: 53 25 N 3 0 W
London, England: 51 32 N 0 5 W
Lyons, France: 45 45 N 4 50 E
Madrid, Spain: 40 26 N 3 42 W
...
Here's the section of the code that I think is throwing the error. I can post more if needed, but I think this is the relevant part.
while(is_more_stuff_there(file_to_read))
{
getline(file_to_read, line);
// parse city
index = line.find(':');
city_name = line.substr(0 , line.find(':'));
istringstream position_stream(line.substr(index + 2 , line.find(':')));
cout << city_name << endl;
// initialize an array to store the parsed values from the position_string
string position_array[6];
string item;
int i = 0;
// fill the array, split by spaces
while (getline(position_stream, item, ' '))
{
position_array[i] = item;
i++;
cout << item << endl;
}
cout << position_array[4] << endl;
// initialize the position variables
lat_min = stoi(position_array[0]);
lat_sec = stoi(position_array[1]);
long_min = stoi(position_array[3]);
long_sec = stoi(position_array[4]);
// determine positivity of lats and longs
if (position_array[2] == "S") { lat_min *= -1; lat_sec *= -1; }
if (position_array[5] == "E") { long_min *= -1; long_sec *= -1; }
vertex city(city_name, lat_min, lat_sec, long_min, long_sec);
g.add_vertex(city);
}

Answer 1

There is a non-printing character in your text file, just before the 2 in question. you could find what exactly it is by using od -x (if you're on a unix box). Or simply remove the line and retype it.

Answer 2

One problem that I can see with your code is that the second parameter passed to the substr function seems wrong. It should be the length of the sub-string to extract but that need not coincide with the index of the :. You can simply leave the second parameter out to get the entire remaining sub-string.
std::istringstream position_stream(line.substr(index + 2));
If you only add 1 to index, your code will also parse inputs where there is no space after the colon.
Although not fundamentally wrong, the code could be simplified by using the C++ style extraction operators. You can read in your four fields directly from the stream.
int lat_min, lat_sec, long_min, long_sec;
std::string ns, we;
position_stream >> lat_min >> lat_sec >> ns >> long_min >> long_sec >> we;
Then continue processing them with whatever logic is required.