[igraph] Using std::vector with Igraph

[Ruben Vacing]

I've been trying to find a really function that let me convert from 
std::vector of vector to igraph_vector_ptr_t and the opposite way.
The reason is, there are different classes like a std::sort, std::unique
 and others, that let us manipulate vectors, this function do not exist 
in Igraph libraries, because the library is a C library.
The next code only show the code to convert from std::vector to  
igraph_vector_ptr_t, the problem is that it doesn't work, please help me
 to help me to improve it. This code it doesn't work :(


#include <igraph.h>
#include <fstream>
#include <iostream>
#include <stdlib.h>
#include <vector>
#include <algorithm>

using namespace std;

void print_vector(igraph_vector_t *v, FILE *f) {
  long int i;
  long int l=igraph_vector_size(v);
  for (i=0; i<l; i++) {
    fprintf(f, " %li", (long int) VECTOR(*v)[i]);
  }
  fprintf(f, "\n");
}

void Stl_To_Igraph_vector_ptr_t(std::vector< std::vector< long int > > & vectR, igraph_vector_ptr_t * vl) {
      long int i,j,n;

      igraph_vector_t vt;
      igraph_vector_init(&vt,4);
      for (i = 0; i< 2; i++) {
            for (j = 0; j< 4; j++) {
                //cout << vectR.at(i).at(j) << " ";
                VECTOR(vt)[j]=vectR.at(i).at(j);
            }
            //cout<<endl;
            igraph_vector_ptr_set(vl, i,&vt);
      }
}

int main() {

  // Set STL Vectors
  std::vector< std::vector< long int > > vectR;
  std::vector<long int> vectRi1,vectRi2;
  long int myarray1 [] = { 1,2,3,4 };
  long int myarray2 [] = { 5,6,7,8 };

  vectRi1.insert(vectRi1.begin(), myarray1,  myarray1+4);
  vectRi2.insert(vectRi2.begin(), myarray2,  myarray2+4);

  vectR.push_back(vectRi1);
  vectR.push_back(vectRi2);

  // Convert From Stl vector to Igraph_vector_ptr_t
  igraph_vector_ptr_t vIgraph;

  igraph_vector_ptr_init(&vIgraph, 2);
  Stl_To_Igraph_vector_ptr_t(vectR, &vIgraph);

  // Print and distroyed
  long int i;
  for (i=0; i<igraph_vector_ptr_size(&vIgraph); i++) {
    print_vector((igraph_vector_t *)VECTOR(vIgraph)[i],stdout);
    igraph_vector_destroy((igraph_vector_t *)VECTOR(vIgraph)[i]);
    free((igraph_vector_t *)VECTOR(vIgraph)[i]);
  }

  return 0;
}