Get the node ids in the current view as a CSV

function get_current_view_results_as_csv($position_only = false, $nid = 0) {
  $view = views_get_current_view();
  $result_nids = array();
  foreach($view->result as $row_id => $row){
    $result_nids[] = $row->nid;
  }
  if($position_only){
    return array_search($nid, $result_nids);
  }else{
    return implode(',', $result_nids);
  }
}

The above function will give you the result node ids in the current view as a CSV list. If $position_only = TRUE then you need to pass the nid and the functiton will return the position of the given nodeid in the current view results.