/**
  * convert_to_int_list method
  *
  * Convert given input to array of positive integers.
  *
  * @param char  $separator Value used to separate integers, if any
  * @param array $input     Allegedly list of positive integers
  *
  * @return array List of positive integers
  */
 public static function convert_to_int_list($separator, $input)
 {
     return self::map_to_integer(Ai1ec_Utility_Array::opt_explode($separator, $input));
 }