pub fn unique(list: List(a)) -> List(a) {
  case list {
    [] -> []
    [x, ..rest] -> [x, ..unique(filter(rest, fn(y) { y != x }))]
  }
}

pub fn unique(xs: List(a)) -> List(a) {
  let #(result_rev, _) =
    xs
    |> list.fold(#([], set.new()), fn(acc, x) {
      let #(result_rev, seen) = acc
      case set.contains(seen, x) {
        False -> #([x, ..result_rev], set.insert(seen, x))
        True -> #(result_rev, seen)
      }
    })
  result_rev |> list.reverse
}