$values: ();
$limit: 10;

foo {
  $num: random($limit);
  $is-digit: type-of($num) == number and floor($num) == $num;
  $is-within-range: $num >= 1 and $num <= $limit;
  $is-random: index($values, $num) == null;
  $values: append($values, $num);

  @for $i from 1 through 1000 {
    $num: random($limit);
    $is-digit: $is-digit and type-of($num) == number and floor($num) == $num;
    $is-within-range: $is-within-range and $num >= 1 and $num <= $limit;
    $is-random: $is-random and index($values, $num) == null;
    $values: append($values, $num);
  }

  is-defined: $num != "random(10)";
  is-digit: $is-digit;
  is-within-range: $is-within-range;
    is-random: $is-random;
}