exception Empty_list

let fold fn = function
  | [] -> raise Empty_list
  | head :: tail -> List.fold_left fn head tail

let list_min ls = fold Stdlib.min ls

let list_max ls = fold Stdlib.max ls

let rec repeat n a = if n <= 0 then [] else a :: repeat (n - 1) a

let empty ls = ls = []

let rec zip l1 l2 =
  match (l1, l2) with
  | [], _ -> []
  | _, [] -> []
  | h1 :: t1, h2 :: t2 -> (h1, h2) :: zip t1 t2

let rec transpose = function
  | [] :: _ -> []
  | ls -> List.(map hd ls) :: transpose List.(map tl ls)

let flip f a b = f b a

let rot_right ls = List.(rev ls |> transpose)

let rot_left ls = List.(transpose ls |> rev)

let saturating_sub b a = if a < b then 0 else a - b