How to read in points from a file

Question

I am reading in a file of the format:

12, 10
15, 20
2, 10000

I want to read these in as x,y points. I've started out, but I'm not sure where to proceed from here... Here is what I have so far:

ifstream input("points.txt");
string line_data;

while (getline(input, line_data))
{
    int d;
    std::cout << line_data << std::endl;
    stringstream line_stream(line_data);
    while (line_stream >> d)
    {
        std::cout << d << std::endl;
    }
}

How can I read each of these lines in as an x,y integer?

score 6 · Accepted Answer · answered Dec 19 '11 at 21:20

6

Say:

int a, b; char comma;

if (line_stream >> a >> comma >> b)
{
  // process pair (a, b)
}

answered Dec 19 '11 at 21:20

Kerrek SB

464,522
92
875
1,084

Or, if line-by-line parsing isn't required, `while(input >> a ...) ...`. – Robᵩ Dec 19 '11 at 21:50
@Rob: Yeah, though it's a bit more robust to split it into lines. At least that way you can recover from an error. – Kerrek SB Dec 19 '11 at 21:57

score 2 · Answer 2 · answered Dec 19 '11 at 21:36

2

what about this ?

#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    std::ifstream input("points.txt");

    while (!input.eof())
    {
        int x, y;
        char separator;

        input >> x  >> separator >> y;

        cout << x << ", " << y << endl;
    }
}

answered Dec 19 '11 at 21:36

n1r3

8,593
3
18
19

1

[This is not a good practice.](http://stackoverflow.com/questions/5605125/why-is-iostreameof-inside-a-loop-condition-considered-wrong) – Blastfurnace Dec 19 '11 at 21:46
Please don't encourage the use of `ios::eof` as a loop condition. Doing so almost always results in buggy code. Prefer `while(input >> x >> separator >> y)`. – Robᵩ Dec 19 '11 at 21:48

score 1 · Answer 3 · answered Dec 19 '11 at 21:34

1

ifstream input("points.txt");
int x, y;
char comma;
while (input >> x >> comma >> y)
{
    cout << x << " " << y << endl;
}

answered Dec 19 '11 at 21:34

Adam Stelmaszczyk

19,665
4
70
110

How to read in points from a file

3 Answers3