I am trying to read a file of the following format

id1 1 2 3
id2 2 4 6
id3 5 6 7
...

using this code

Dataset::Dataset(ifstream &file) {
    string token;
    int i = 0;
    while (!file.eof() && (file >> token)){
        // read line tokens one-by-one
        string ID = token;
        vector<int> coords;
        while ((file.peek()!='\n') && (!file.eof()) && (file >> token)) {
            coords.push_back(atoi(token.c_str()));
        }
        points.push_back(new Point(ID, coords));
        i  ;
    }
    cout << "Loaded " << i << " points." << endl;
}

But it tells me I have read 0 points. What am I doing wrong?

Edit: I am openning this using input_stream.open(input_file) and file.good() returns true.

Edit #2: actually .good() returns true the first time and then false. What is that all about?

Edit #3: GUYS. IT'S FREAKING WINDOWS. When i put the path as Dataset/test.txt by cin it works and when I do it like Dataset\test.txt by the commandline it doesn't...

Now the problem is it seems not stop at new lines!

Edit #4: Freaking windows again! It was peeking '\r' instead of '\n'.

CodePudding user response：

Here's an idea: overload operator>>:

struct Point
{
    int x, y, z;
    friend std::istream& operator>>(std::istream& input, Point& p);
};

std::istream& operator>>(std::istream& input, Point& p)
{
    input >> p.x;
    input >> p.y;
    input >> p.z;
    input.ignore(10000, '\n'); // eat chars until end of line.
    return input;
}

struct Point_With_ID 
  : public Point
{
    std::string id;
    friend std::istream& operator>>(std::istream& input, Point_With_ID& p);
};


std::istream& operator>>(std::istream& input, Point_With_ID& p)
{
    input >> p.id;
    input >> static_cast<Point&>(p);  // Read in the parent items.
    return input;
}

Your input could look like this:

std::vector<Point_With_ID> database;
Point_With_ID p;
while (file >> p)
{
    database.push_back(p);
}

I separated the Point class so that it can be used in other programs or assignments.

CodePudding user response：

You should not use eof() in a loop condition. See Why is iostream::eof inside a loop condition considered wrong? for details. You can instead use the following program to read into the vector of Point*.

#include <iostream>
#include <sstream>
#include <fstream>
#include <vector>
class Point 
{
    public:
        std::string ID = 0;
        std::vector<int> coords;
    Point(std::string id, std::vector<int> coord): ID(id), coords(coord)
    {
        
    }
};
int main()
{
    
    std::vector<Point*> points;
    std::ifstream file("input.txt");
    std::string line;
    int var = 0;
    while (std::getline(file, line, '\n'))//read line by line
    {
        int j = 0;
        std::istringstream ss(line);
        
        std::string ID;
        ss >> ID;
        
        std::vector<int> coords(3);//create vector of size 3 since we already know only 3 elements needed
        
        while (ss >> var) { 
            coords.at(j) = var;
            
              j;
        }
        
        points.push_back(new Point(ID, coords));

    }
    std::cout<<points.size()<<std::endl;

    //...also don't forget to free the memory using `delete` or use smart pointer instead
    return 0;
}

The output of the above program can be seen here.

Note that if you're using new then you must use delete to free the memory that you've allocated. This was not done in the above program that i have given since i only wanted to show how you can read the data in your desired manner.

CodePudding user response：

I managed to make it work by accounting for both '\r' and '\n' endings and ignoring trailing whitespace like this:

Dataset::Dataset(ifstream &file) {
  string token;
  int i = 0;
  while (file >> token){
      // read line tokens one-by-one
      string ID = token;
      vector<int> coords;
      while ((file.peek()!='\n' && file.peek()!='\r') && (file >> token)) {   // '\r' for windows, '\n' for unix
        coords.push_back(atoi(token.c_str()));
        if (file.peek() == '\t' || file.peek() == ' ') {   // ignore these
            file.ignore(1);
        }
      }
      Point p(ID, coords);
      points.emplace_back(p);
      i  ;
      // ignore anything until '\n'
      file.ignore(32, '\n');
   }
   cout << "Loaded " << i << " points." << endl;
}

Probably not the best of the solutions suggested but it's working!