From 0a58e552878a78a62dacfa71e0bfb4eec71c2671 Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Wed, 10 May 2017 20:26:29 +0200
Subject: [PATCH] large refactor of `CCSimple_queue` (close #125)

---
 src/data/CCSimple_queue.ml  | 158 ++++++++++++++++++++++++++++++++----
 src/data/CCSimple_queue.mli |  37 ++++++++-
 2 files changed, 174 insertions(+), 21 deletions(-)

diff --git a/src/data/CCSimple_queue.ml b/src/data/CCSimple_queue.ml
index 0b16449b..7bc68efd 100644
--- a/src/data/CCSimple_queue.ml
+++ b/src/data/CCSimple_queue.ml
@@ -3,6 +3,11 @@
 
 (** {1 Functional queues (fifo)} *)
 
+type 'a sequence = ('a -> unit) -> unit
+type 'a printer = Format.formatter -> 'a -> unit
+type 'a klist = unit -> [`Nil | `Cons of 'a * 'a klist]
+type 'a gen = unit -> 'a option
+
 type 'a t = {
   hd : 'a list;
   tl : 'a list;
@@ -14,19 +19,19 @@ let empty = {
 }
 
 (* invariant: if hd=[], then tl=[] *)
-let _make hd tl = match hd with
+let make_ hd tl = match hd with
   | [] -> {hd=List.rev tl; tl=[] }
   | _::_ -> {hd; tl; }
 
 let is_empty q = q.hd = []
 
-let push x q = {q with tl = x :: q.tl; }
+let push x q = make_ q.hd (x :: q.tl)
 
 let snoc q x = push x q
 
 let peek_exn q =
   match q.hd with
-    | [] -> assert (q.tl = []); raise (Invalid_argument "Queue.peek")
+    | [] -> assert (q.tl = []); invalid_arg "Queue.peek"
     | x::_ -> x
 
 let peek q = match q.hd with
@@ -35,45 +40,162 @@ let peek q = match q.hd with
 
 let pop_exn q =
   match q.hd with
-    | [] -> assert (q.tl = []); raise (Invalid_argument "Queue.peek")
+    | [] -> assert (q.tl = []); invalid_arg "Queue.peek"
     | x::hd' ->
-      let q' = _make hd' q.tl in
+      let q' = make_ hd' q.tl in
       x, q'
 
 let pop q =
   try Some (pop_exn q)
   with Invalid_argument _ -> None
 
+(*$Q
+  Q.(list small_int) (fun l -> \
+    let q = of_list l in \
+    equal CCInt.equal (Gen.unfold pop q |> of_gen) q)
+  *)
+
 let junk q =
   try
     let _, q' = pop_exn q in
     q'
   with Invalid_argument _ -> q
 
-(** Append two queues. Elements from the second one come
-    after elements of the first one *)
-let append q1 q2 =
-  { hd=q1.hd;
-    tl=q2.tl @ (List.rev_append q2.hd q1.tl);
-  }
-
 let map f q = { hd=List.map f q.hd; tl=List.map f q.tl; }
 
-let size q = List.length q.hd + List.length q.tl
+let rev q = make_ q.tl q.hd
 
-let (>|=) q f = map f q
+(*$Q
+  Q.(list small_int) (fun l -> \
+    equal CCInt.equal (of_list l |> rev) (of_list (List.rev l)))
+  Q.(list small_int) (fun l -> \
+    let q = of_list l in \
+    equal CCInt.equal q (q |> rev |> rev))
+*)
+
+let length q = List.length q.hd + List.length q.tl
+
+(*$Q
+  Q.(list small_int)(fun l -> \
+    length (of_list l) = List.length l)
+*)
+
+(*$Q
+  Q.(list small_int)(fun l -> \
+    equal CCInt.equal (of_list l) (List.fold_left snoc empty l))
+*)
 
 let fold f acc q =
   let acc' = List.fold_left f acc q.hd in
   List.fold_right (fun x acc -> f acc x) q.tl acc'
 
-let iter f q = fold (fun () x -> f x) () q
+(* iterate on a list in reverse order *)
+let rec rev_iter_ f l = match l with
+  | [] -> ()
+  | x :: tl -> rev_iter_ f tl; f x
 
-type 'a sequence = ('a -> unit) -> unit
+let iter f q =
+  List.iter f q.hd;
+  rev_iter_ f q.tl
+
+let to_list q = fold (fun acc x->x::acc) [] q |> List.rev
+
+let add_list q l = List.fold_left snoc q l
+let of_list l = add_list empty l
 
 let to_seq q = fun k -> iter k q
 
-let of_seq seq =
-  let q = ref empty in
+let add_seq q seq =
+  let q = ref q in
   seq (fun x -> q := push x !q);
   !q
+
+let of_seq s = add_seq empty s
+
+(*$Q
+  Q.(list small_int) (fun l -> \
+    equal CCInt.equal \
+      (of_seq (Sequence.of_list l)) \
+      (of_list l))
+  Q.(list small_int) (fun l -> \
+    l = (of_list l |> to_seq |> Sequence.to_list))
+*)
+
+let rec klist_iter_ k f = match k() with
+  | `Nil -> ()
+  | `Cons (x,tl) -> f x; klist_iter_ tl f
+
+let add_klist q l = add_seq q (klist_iter_ l)
+let of_klist l = add_klist empty l
+
+let to_klist q =
+  let rec aux1 l () = match l with
+    | [] -> aux2 (List.rev q.tl) ()
+    | x :: tl -> `Cons (x, aux1 tl)
+  and aux2 l () = match l with
+    | [] -> `Nil
+    | x :: tl -> `Cons (x, aux2 tl)
+  in
+  aux1 q.hd
+
+let rec gen_iter g f = match g() with
+  | None -> ()
+  | Some x -> f x; gen_iter g f
+
+let add_gen q g = add_seq q (gen_iter g)
+let of_gen g = add_gen empty g
+
+let to_gen q =
+  let st = ref (`Left q.hd) in
+  let rec aux () = match !st with
+    | `Stop -> None
+    | `Left [] -> st := `Right q.tl; aux()
+    | `Left (x::tl) -> st := `Left tl; Some x
+    | `Right [] -> st := `Stop; None
+    | `Right (x::tl) -> st := `Right tl; Some x
+  in
+  aux
+
+let rec klist_equal eq l1 l2 = match l1(), l2() with
+  | `Nil, `Nil -> true
+  | `Nil, _
+  | _, `Nil -> false
+  | `Cons (x1,l1'), `Cons (x2,l2') ->
+    eq x1 x2 && klist_equal eq l1' l2'
+
+let equal eq q1 q2 = klist_equal eq (to_klist q1) (to_klist q2)
+
+(*$Q
+  Q.(pair (list small_int)(list small_int)) (fun (l1,l2) -> \
+    equal CCInt.equal (of_list l1)(of_list l2) = (l1=l2))
+*)
+
+let append q1 q2 =
+  add_seq q1
+    (fun yield ->
+       to_seq q2 yield)
+
+(*$Q
+  Q.(pair (list small_int)(list small_int)) (fun (l1,l2) -> \
+    equal CCInt.equal \
+      (append (of_list l1)(of_list l2)) \
+      (of_list (List.append l1 l2)))
+  *)
+
+module Infix = struct
+  let (>|=) q f = map f q
+  let (<::) = snoc
+  let (@) = append
+end
+
+include Infix
+
+(** {2 IO} *)
+
+let pp ?(sep=fun out () -> Format.fprintf out ",@ ") pp_item out l =
+  let first = ref true in
+  iter
+    (fun x ->
+       if !first then first := false else sep out ();
+       pp_item out x)
+    l
diff --git a/src/data/CCSimple_queue.mli b/src/data/CCSimple_queue.mli
index 1b3085af..35dc801b 100644
--- a/src/data/CCSimple_queue.mli
+++ b/src/data/CCSimple_queue.mli
@@ -6,6 +6,11 @@
 (** Simple implementation of functional queues
     @since NEXT_RELEASE *)
 
+type 'a sequence = ('a -> unit) -> unit
+type 'a printer = Format.formatter -> 'a -> unit
+type 'a klist = unit -> [`Nil | `Cons of 'a * 'a klist]
+type 'a gen = unit -> 'a option
+
 type +'a t
 (** Queue containing elements of type 'a *)
 
@@ -44,16 +49,42 @@ val append : 'a t -> 'a t -> 'a t
 val map : ('a -> 'b) -> 'a t -> 'b t
 (** Map values *)
 
-val (>|=) : 'a t -> ('a -> 'b) -> 'b t
+val rev : 'a t -> 'a t
+(** Reverse the queue. Constant time. *)
 
-val size : 'a t -> int
+val equal : ('a -> 'a -> bool) -> 'a t -> 'a t -> bool
+
+module Infix : sig
+  val (>|=) : 'a t -> ('a -> 'b) -> 'b t (** Alias to {!map} *)
+  val (@) : 'a t -> 'a t -> 'a t (** Alias to {!append} *)
+  val (<::) : 'a t -> 'a -> 'a t (** Alias to {!snoc} *)
+end
+
+include module type of Infix
+
+val length : 'a t -> int
 (** Number of elements in the queue (linear in time) *)
 
 val fold : ('b -> 'a -> 'b) -> 'b -> 'a t -> 'b
 
 val iter : ('a -> unit) -> 'a t -> unit
 
-type 'a sequence = ('a -> unit) -> unit
+val to_list : 'a t -> 'a list
+val add_list : 'a t -> 'a list -> 'a t
+val of_list : 'a list -> 'a t
+
 val to_seq : 'a t -> 'a sequence
+val add_seq : 'a t -> 'a sequence -> 'a t
 val of_seq : 'a sequence -> 'a t
 
+val to_klist : 'a t -> 'a klist
+val add_klist : 'a t -> 'a klist -> 'a t
+val of_klist : 'a klist -> 'a t
+
+val of_gen : 'a gen -> 'a t
+val add_gen : 'a t -> 'a gen -> 'a t
+val to_gen : 'a t -> 'a gen
+
+(** {2 IO} *)
+
+val pp : ?sep:unit printer -> 'a printer -> 'a t printer