Wypieprzone normalize

module type QUEUE_FUN =
sig
	type 'a t
	exception Empty of string
	val empty: unit -> 'a t
	val enqueue: 'a * 'a t -> 'a t
	val dequeue: 'a t -> 'a t
	val first: 'a t -> 'a
	val isEmpty: 'a t -> bool
end;;

module PairOfListsQueue : QUEUE_FUN =
  struct
    type 'a t = 'a list * 'a list

    exception Empty of string

    let empty () = ([], [])

    let enqueue (element, queue) =
			if(fst queue = []) then (List.rev (element::snd queue),[])
			else (fst queue, element::snd queue)

    let dequeue = function
			| ([], _) -> ([], [])
			| (head :: tail, endOfQueue) -> if(tail = []) then (List.rev endOfQueue,[]) else (tail,endOfQueue)

    let first queue =
			match fst queue with
				| [] -> raise (Empty "module PairOfListsQueue: first")
				| (head :: tail) -> head

    let isEmpty queue =
			fst queue = []
end;;