From 17eab9c3f441c297f904fe6c474c687c7f77d97d Mon Sep 17 00:00:00 2001
From: Master Builder <gylfi@stebbi.is>
Date: Thu, 11 Jan 2024 16:24:50 +0000
Subject: [PATCH] CCVector: Add function foldi

---
 src/core/CCVector.ml   | 12 ++++++++++++
 src/core/CCVector.mli  |  5 +++++
 tests/core/t_vector.ml | 14 ++++++++++++++
 3 files changed, 31 insertions(+)

diff --git a/src/core/CCVector.ml b/src/core/CCVector.ml
index 8771e74b..f1d9d240 100644
--- a/src/core/CCVector.ml
+++ b/src/core/CCVector.ml
@@ -412,6 +412,18 @@ let fold f acc v =
   in
   fold acc 0
 
+let foldi f acc v =
+  let { vec; size } = v in
+  let rec fold acc i =
+    if i = size then
+      acc
+    else (
+      let x = Array.unsafe_get vec i in
+      fold (f i acc x) (i + 1)
+    )
+  in
+  fold acc 0
+
 let exists p v =
   let n = v.size in
   let rec check i =
diff --git a/src/core/CCVector.mli b/src/core/CCVector.mli
index 7e858453..c8fddf6e 100644
--- a/src/core/CCVector.mli
+++ b/src/core/CCVector.mli
@@ -206,6 +206,11 @@ val filter_in_place : ('a -> bool) -> ('a, rw) t -> unit
 val fold : ('b -> 'a -> 'b) -> 'b -> ('a, _) t -> 'b
 (** Fold on elements of the vector *)
 
+val foldi : (int -> 'b -> 'a -> 'b) -> 'b -> ('a, _) t -> 'b
+(** [foldi f init v] is just like {!fold}, but it also passes in the index
+    of each element as the first argument to the function [f].
+    @since NEXT_RELEASE *)
+
 val exists : ('a -> bool) -> ('a, _) t -> bool
 (** Existential test (is there an element that satisfies the predicate?). *)
 
diff --git a/tests/core/t_vector.ml b/tests/core/t_vector.ml
index 75fed217..a3f6236c 100644
--- a/tests/core/t_vector.ml
+++ b/tests/core/t_vector.ml
@@ -737,3 +737,17 @@ t @@ fun () -> of_list CCList.(1 -- 300_000) |> to_list = CCList.(1 -- 300_000)
 t @@ fun () ->
 let v = 1 -- 10 in
 to_list v = Gen.to_list (to_gen v)
+;;
+
+t @@ fun () ->
+let v = create () in
+0 = foldi (fun i acc _ -> acc + i) 0 v
+;;
+
+t @@ fun () ->
+let v = create () in
+push v 0;
+push v 0;
+push v 0;
+push v 0;
+6 = foldi (fun i acc _ -> acc + i) 0 v