From 4b30aba080c5ab2f36f7b212e42f6f3069372a07 Mon Sep 17 00:00:00 2001
From: Jacques-Pascal Deplaix <jp.deplaix@gmail.com>
Date: Sat, 23 Dec 2017 15:25:00 +0000
Subject: [PATCH] Allow negative indexes in CCList.remove_at_idx

---
 src/core/CCList.ml  | 9 ++++++++-
 src/core/CCList.mli | 4 +++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/core/CCList.ml b/src/core/CCList.ml
index 290dbaa5..bdfddf68 100644
--- a/src/core/CCList.ml
+++ b/src/core/CCList.ml
@@ -1111,12 +1111,19 @@ let remove_at_idx i l0 =
     | y::l' ->
       aux l' (y::acc) (i-1)
   in
-  aux l0 [] i
+  if i < 0 then
+    aux l0 [] (List.length l0 + i)
+  else
+    aux l0 [] i
 
 (*$T
   remove_at_idx 0 [1;2;3;4] = [2;3;4]
   remove_at_idx 3 [1;2;3;4] = [1;2;3]
   remove_at_idx 5 [1;2;3;4] = [1;2;3;4]
+  remove_at_idx (-1) [1;2;3;4] = [1;2;3]
+  remove_at_idx (-2) [1;2;3;4] = [1;2;4]
+  remove_at_idx (-3) [1;2;3;4] = [1;3;4]
+  remove_at_idx (-4) [1;2;3;4] = [2;3;4]
 *)
 
 let range_by ~step i j =
diff --git a/src/core/CCList.mli b/src/core/CCList.mli
index cb5a379b..c380419f 100644
--- a/src/core/CCList.mli
+++ b/src/core/CCList.mli
@@ -359,7 +359,9 @@ val insert_at_idx : int -> 'a -> 'a t -> 'a t
 
 val remove_at_idx : int -> 'a t -> 'a t
 (** Remove element at given index. Does nothing if the index is
-    too high. *)
+    too high.
+    If the index is negative, it will remove element starting from the end
+    of the list. *)
 
 (** {2 Set Operators}