Creating a matrix from an input file

[qsqais]

Dear C++ users,

I am very new in C++. I have a question concerning reading an input file, where I have to create a matrix from same elements of the data if a condition is fullfilled.

Here is my input files (matrix.txt)

This is a line, below is another line with numbers
0.15 10.1

*M
2.5  3.01  4.11
*M
6.16  7.17  8.01
*M
10.16 11.133 12.12
*M
14.17 15.110 16.16
Reading should stop in this line
another line
another line
15.0  12.015 13.001

And my code is:

// Reading the input file.
#include <iostream>
#include <fstream>
#include <vector>
#include <sstream>
#include <limits>
#include <iterator>
#include <stdlib.h>
using namespace std;

vector<vector<double> > read(ifstream& fil, string sec,string fir)
{
    string lines;
    vector<vector<double> > data;

        if (fir == sec)
        {
            while (getline(fil,lines))
            {
                istringstream ss(lines);
                //stringstream is(lines);
                data.push_back(vector<double>(istream_iterator<double>(ss),
                                              istream_iterator<double>()));
            }
        }
    return data;
}

int main()
{
    int n, m, c;
    ifstream pa("matrix.txt");

    vector<vector<double> > matr;
    string first, ba("*M");

    while (pa>>first)
    {
        pa.ignore(numeric_limits <streamsize>::max(),'\n');
        matr = read(pa,ba,first);

    }
    n = matr.size();
    m = matr[0].size();


    for ( int i = 0; i<n; i = i+2)
    {
        for (int j = 0; j<m; j++)
        {
            cout << matr[i][j]<< "  ";
        }
        cout << '\n';
    }
    cout << n << '\n';
    cout << m;
    return 0;
}

From input file I should create a matrix as follow:

[2.5 3.01 4.11
6.16 7.17 8.01
10.16 11.133 12.12
14.17 15.110 16.16]

The question is how can I read only those lines after each line of *M? Currently the code reads all lines after the first *M.

Thank you very much in advance!

[TarikNeaj]

Since you know it's 4 lines of numbers. Couldnt you use a for-loop that runs 4 times and reads in all the numbers, that way it will stop where you want it to, no?

[qsqais]

Actually, lines of input file can change. It could be more or less, and I am interested only on those lines after each *M.

[TarikNeaj]

Well then, you can first read the file word by word, using std::cin instead of std::getline. If word is word is ever equal to *M you know that the next line will be numbers. So after you've read 14.17 15.110 16.16 and attempt to read in the next word, if it's not *M, then ignore it. Does that make sense?

[qsqais]

Dear TarikNeaj,

Thank you for suggestions (especially learning on how to debug was very usefull), now everthing is working fine.

[TarikNeaj]

Glad it worked out =) Would you mind posting the full working program So other people that might come across this thread can get help from it?

[qsqais]

Dear TarikNeaj,

Sure I can post the code.
I slightly changed input file (by adding & after each row). Here is the new input file with and the code.
Have a great weekend!

This is a line, below is another line with numbers
0.15 10.1

*M
2.5  3.01  4.11
&
*M
6.16  7.17  8.01
&
*M
10.16 11.133 12.12
&
*M
14.17 15.110 16.16
Reading should stop in this line
another line
another line
15.0  12.015 13.001

The code:

// Reading the input file.
#include <iostream>
#include <fstream>
#include <vector>
#include <sstream>
#include <limits>
#include <iterator>
#include <cmath>
using namespace std;

vector<vector<double> > read(ifstream& fil, string sec,string fir,string last)
{
    string lines;
    vector<vector<double> > data;

        while (fil >> fir)
        {
            fil.ignore(numeric_limits <streamsize>::max(),'\n');
            if (fir == sec)
            {
                while (fil>>lines)
                {
                    if (lines == "&") break;
                    if (lines == last) break;
                    data.push_back(vector<double>());
                    stringstream is(lines);
                    double nm;
                    while (is >> nm)
                    {
                        data.back().push_back(nm);
                    }


                }
            }
        }

    return data;
}


int main()
{
    int n, m;
    ifstream pa("matrix.txt");

    vector<vector<double> > matr, ma;
    string first, ba("*M");
    string fo("Reading");

    matr = read(pa,ba,first,fo);

    n = matr.size();
    m = matr[0].size();

    for ( int i = 0; i<n; i =i+1)
    {
        for (int j = 0; j<m; j++)
        {

                cout << matr[i][j]<< "  ";
        }
        //cout << '\n';
    }

    cout << '\n'<<n << '\n';
    cout << m;
    return 0;
}