From b9cc91fb96bf3a7b8c5d80a736b20c21339afdfa Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Sun, 7 Jan 2024 23:21:32 -0500
Subject: [PATCH] pvec: implement `iter_rev` directly

---
 src/pvec/containers_pvec.ml  | 25 +++++++++++++++++++++++--
 src/pvec/containers_pvec.mli |  4 ++++
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/src/pvec/containers_pvec.ml b/src/pvec/containers_pvec.ml
index 5902c03e..ac83d9e3 100644
--- a/src/pvec/containers_pvec.ml
+++ b/src/pvec/containers_pvec.ml
@@ -268,6 +268,24 @@ let iteri f (self : 'a t) : unit =
     f (i + tail_off) (Array.unsafe_get self.tail i)
   done
 
+let rec iter_rev_rec_ f (self : _ tree) =
+  match self with
+  | Empty -> ()
+  | Leaf a ->
+    for i = A.length a - 1 downto 0 do
+      f (Array.unsafe_get a i)
+    done
+  | Node a ->
+    for i = A.length a - 1 downto 0 do
+      iter_rev_rec_ f (Array.unsafe_get a i)
+    done
+
+let iter_rev f (self : 'a t) : unit =
+  for i = A.length self.tail - 1 downto 0 do
+    f (Array.unsafe_get self.tail i)
+  done;
+  iter_rev_rec_ f self.t
+
 let rec iteri_rev_rec_ f idx (self : _ tree) =
   match self with
   | Empty -> ()
@@ -294,12 +312,15 @@ let fold_lefti f x m =
   iteri (fun i x -> acc := f !acc i x) m;
   !acc
 
-let foldi_rev f x m =
+let fold_revi f x m =
   let acc = ref x in
   iteri_rev (fun i x -> acc := f !acc i x) m;
   !acc
 
-let fold_rev f x m = foldi_rev (fun acc _ x -> f acc x) x m
+let fold_rev f x m =
+  let acc = ref x in
+  iter_rev (fun x -> acc := f !acc x) m;
+  !acc
 
 let rec map_t f (self : _ tree) : _ tree =
   match self with
diff --git a/src/pvec/containers_pvec.mli b/src/pvec/containers_pvec.mli
index dd3cd71a..6c40b497 100644
--- a/src/pvec/containers_pvec.mli
+++ b/src/pvec/containers_pvec.mli
@@ -63,6 +63,9 @@ val drop_last : 'a t -> 'a t
 
 val iter : ('a -> unit) -> 'a t -> unit
 
+val iter_rev : ('a -> unit) -> 'a t -> unit
+(** Iterate on elements but starting from the end. *)
+
 val iteri : (int -> 'a -> unit) -> 'a t -> unit
 (** Iterate on elements with their index, in increasing order. *)
 
@@ -72,6 +75,7 @@ val iteri_rev : (int -> 'a -> unit) -> 'a t -> unit
 val fold_left : ('b -> 'a -> 'b) -> 'b -> 'a t -> 'b
 val fold_rev : ('b -> 'a -> 'b) -> 'b -> 'a t -> 'b
 val fold_lefti : ('b -> int -> 'a -> 'b) -> 'b -> 'a t -> 'b
+val fold_revi : ('b -> int -> 'a -> 'b) -> 'b -> 'a t -> 'b
 
 val append : 'a t -> 'a t -> 'a t
 (** [append a b] adds all elements of [b] at the end of [a]. This is