while (states.eof() == 0)
  {
  std::istringstream complexString;

  getline(states, tmp_str, ':');
  tmp_triplet.row() = stoi(tmp_str);
  getline(states, tmp_str, ':');
  tmp_triplet.col() = stoi(tmp_str);
  getline(states, tmp_str, ':');
  complexString.str (tmp_str);
  complexString >> tmp_triplet.value();
  // Then something useful done with the triplet before moving onto the next one
  }