Source file deque.ml
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module Basic =
struct
type 'a t = {
front: 'a list;
rear: 'a list;
}
let empty: 'a t =
{front = []; rear = [];}
let push_front (e: 'a) (fifo: 'a t): 'a t =
{fifo with front = e :: fifo.front}
let push_rear (e: 'a) (fifo: 'a t): 'a t =
{fifo with rear = e :: fifo.rear}
let pop_front (fifo: 'a t): ('a * 'a t) option =
match fifo.front with
| hd :: front ->
Some (hd, {fifo with front})
| [] ->
match List.rev fifo.rear with
| [] ->
None
| hd :: front ->
Some (hd, {front; rear = []})
let prepend (fifo: 'a t) (lst: 'a list): 'a list =
fifo.front @ List.rev_append fifo.rear lst
end
type 'a t =
| Empty
| Nonempty of 'a Basic.t * 'a
let is_empty (f: 'a t): bool =
match f with
| Empty ->
true
| _ ->
false
let has_some (f: 'a t): bool =
not (is_empty f)
let empty: 'a t =
Empty
let push_front (e: 'a) (f: 'a t): 'a t =
match f with
| Empty ->
Nonempty (Basic.empty, e)
| Nonempty (lf, last) ->
Nonempty (Basic.push_front e lf, last)
let push_rear (e: 'a) (f: 'a t): 'a t =
match f with
| Empty ->
Nonempty (Basic.empty, e)
| Nonempty (lf, last) ->
Nonempty (Basic.push_rear last lf, e)
let pop_front (f: 'a t): ('a * 'a t) option =
match f with
| Empty ->
None
| Nonempty (lf, last) ->
match Basic.pop_front lf with
| None ->
Some (last, empty)
| Some (first, lf) ->
Some (first, Nonempty (lf, last))
let update_first (f: 'a -> 'a) (fifo: 'a t): 'a t =
match fifo with
| Empty ->
Empty
| Nonempty (lf, last) ->
match Basic.pop_front lf with
| None ->
Nonempty (lf, f last)
| Some (first, lf) ->
Nonempty (Basic.push_front (f first) lf, last)
let update_last (f: 'a -> 'a) (fifo: 'a t): 'a t =
match fifo with
| Empty ->
Empty
| Nonempty (lf, last) ->
Nonempty (lf, f last)
let to_list (fifo: 'a t): 'a list =
match fifo with
| Empty ->
[]
| Nonempty (lf, last) ->
Basic.prepend lf [last]
let%test _ =
to_list
(empty |> push_rear 0 |> push_rear 1 |> push_rear 2)
=
[0; 1; 2]
let%test _ =
empty |> push_rear 0 |> pop_front
=
Some (0, empty)
let%test _ =
match
empty
|> push_rear 0 |> push_rear 1
|> update_first (fun _ -> 10) |> pop_front
with
| Some (10, fifo ) ->
pop_front fifo = Some (1, empty)
| _ ->
false
let%test _ =
match
empty
|> push_rear 0 |> push_rear 1
|> update_last (fun _ -> 10) |> pop_front
with
| Some (0, fifo ) ->
pop_front fifo = Some (10, empty)
| _ ->
false