(* This code extends 'mini_prelude'. *)

type ('a) queue = 
    Queue of ('a) list * ('a) list * ('a) list ;;

let empty = (Queue (Nil, Nil, Nil)) ;;

let is_empty = 
  (fun v6 -> 
    (match v6 with 
        (Queue (v5, v4, v3)) -> 
          (match v5 with 
              Nil -> true 
            | (Cons (v2, v1)) -> false))) ;;

let rec rotate x = 
  (match x with 
      (Queue (v9, v8, v7)) -> 
        (match v9 with 
            Nil -> 
              (match v8 with 
                  Nil -> (raise (Match_failure (string_of_bool true, 0, 0))) 
                | (Cons (v2, v1)) -> (Cons (v2, v7))) 
          | (Cons (v6, v5)) -> 
              (match v8 with 
                  Nil -> (raise (Match_failure (string_of_bool true, 0, 0))) 
                | (Cons (v4, v3)) -> (Cons (v6, (rotate (Queue (v5, v3, (Cons (v4, v7)))))))))) ;;

let exec = 
  (fun v7 -> 
    (match v7 with 
        (Queue (v6, v5, v4)) -> 
          (match v4 with 
              Nil -> 
                (let v1 = (rotate (Queue (v6, v5, Nil))) 
                in (Queue (v1, Nil, v1))) 
            | (Cons (v3, v2)) -> (Queue (v6, v5, v2))))) ;;

let snoc = 
  (fun v4 -> 
    (fun v5 -> 
      (match v4 with 
          (Queue (v3, v2, v1)) -> (exec (Queue (v3, (Cons (v5, v2)), v1)))))) ;;

let head = 
  (fun x -> 
    (match x with 
        (Queue (v5, v4, v3)) -> 
          (match v5 with 
              Nil -> (raise (Match_failure (string_of_bool true, 0, 0))) 
            | (Cons (v2, v1)) -> v2))) ;;

let tail = 
  (fun x -> 
    (match x with 
        (Queue (v5, v4, v3)) -> 
          (match v5 with 
              Nil -> (raise (Match_failure (string_of_bool true, 0, 0))) 
            | (Cons (v2, v1)) -> (exec (Queue (v1, v4, v3)))))) ;;