blob: 84bb67aa47b5b30b55b7614364b4a68014f10ed9 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
|
(***********************************************************************)
(* *)
(* Objective Caml *)
(* *)
(* Xavier Leroy, projet Cristal, INRIA Rocquencourt *)
(* *)
(* Copyright 1996 Institut National de Recherche en Informatique et *)
(* Automatique. Distributed only by permission. *)
(* *)
(***********************************************************************)
(* $Id$ *)
exception Empty
type 'a queue_cell =
Nil
| Cons of 'a * 'a queue_cell ref
type 'a t =
{ mutable head: 'a queue_cell;
mutable tail: 'a queue_cell }
let create () =
{ head = Nil; tail = Nil }
let clear q =
q.head <- Nil; q.tail <- Nil
let add x q =
match q.tail with
Nil -> (* if tail = Nil then head = Nil *)
let c = Cons(x, ref Nil) in
q.head <- c; q.tail <- c
| Cons(_, newtailref) ->
let c = Cons(x, ref Nil) in
newtailref := c;
q.tail <- c
let peek q =
match q.head with
Nil ->
raise Empty
| Cons(x, _) ->
x
let take q =
match q.head with
Nil ->
raise Empty
| Cons(x, rest) ->
q.head <- !rest;
begin match !rest with
Nil -> q.tail <- Nil
| _ -> ()
end;
x
let rec length_aux = function
Nil -> 0
| Cons(_, rest) -> succ (length_aux !rest)
let length q = length_aux q.head
let rec iter_aux f = function
Nil ->
()
| Cons(x, rest) ->
f x; iter_aux f !rest
let iter f q = iter_aux f q.head
|
