From 57b8e68cb57a320e99574ba70a5f3548dc85c824 Mon Sep 17 00:00:00 2001
From: Francois Berenger <unixjunkie@sdf.org>
Date: Fri, 18 Dec 2020 13:34:28 +0900
Subject: [PATCH] BatArray.remove_at

---
 src/batArray.mliv |  6 ++++++
 src/batArray.mlv  | 16 ++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/src/batArray.mliv b/src/batArray.mliv
index ab8309f12..b58d67045 100644
--- a/src/batArray.mliv
+++ b/src/batArray.mliv
@@ -558,6 +558,12 @@ val insert : 'a array -> 'a -> int -> 'a array
     @raise Invalid_argument
     if [i < 0 || i > Array.length xs]. *)
 
+val remove_at : int -> 'a array -> 'a array
+(** [remove_at i a] returns the array [a] without the element at index [i].
+
+    @raise Invalid_argument if [i] is outside of [a] bounds.
+    @since NEXT_RELEASE *)
+
 (** {6 Boilerplate code}*)
 
 val print : ?first:string -> ?last:string -> ?sep:string ->
diff --git a/src/batArray.mlv b/src/batArray.mlv
index f1fcbadc1..9a9290cfe 100644
--- a/src/batArray.mlv
+++ b/src/batArray.mlv
@@ -822,6 +822,22 @@ let insert xs x i =
      with Invalid_argument _ -> true
 *)
 
+let remove_at i src =
+  let x = src.(i) in (* keep the bound check in there *)
+  let n = length src in
+  let dst = make (n - 1) x in
+  blit src 0 dst 0 i;
+  blit src (i + 1) dst i (n - i - 1);
+  dst
+(*$T remove_at
+    try remove_at 0 [||] = [|1|] \
+      with Invalid_argument _ -> true
+    remove_at 0 [|1;2;3|] = [|2;3|]
+    remove_at 1 [|1;2;3|] = [|1;3|]
+    remove_at 2 [|1;2;3|] = [|1;2|]
+    try remove_at 3 [|1;2;3|] = [|1|] \
+      with Invalid_argument _ -> true
+*)
 
 (* helper function; only works for arrays of equal length *)
 let eq_elements eq_elt a1 a2 = for_all2 eq_elt a1 a2