Merge pull request #544 from UnixJunkie/batlist_remove_at

added remove_at with its unit tests, ocamldoc and interface

src/batList.ml

@@ -593,6 +593,31 @@ let remove_assq x lst =
   loop dummy lst;
   dummy.tl
 
+let remove_at i lst =
+  let rec loop dst i = function
+    | [] -> invalid_arg "BatList.remove_at"
+    | x :: xs ->
+      if i = 0 then
+        dst.tl <- xs
+      else
+        loop (Acc.accum dst x) (i - 1) xs
+  in
+  if i < 0 then
+    invalid_arg "BatList.remove_at"
+  else
+    let dummy = Acc.dummy () in
+    loop dummy i lst;
+    dummy.tl
+
+(*$T remove_at
+  try ignore (remove_at 0 []) ; false with Invalid_argument _ -> true
+  try ignore (remove_at 1 [0]); false with Invalid_argument _ -> true
+  remove_at 0 [0]       = []
+  remove_at 0 [0; 1; 2] = [1; 2]
+  remove_at 1 [0; 1; 2] = [0; 2]
+  remove_at 2 [0; 1; 2] = [0; 1]
+*)
+
 let rfind p l = find p (rev l)
 
 let find_all p l =

src/batList.mli

@@ -529,6 +529,14 @@ val remove_if : ('a -> bool) -> 'a list -> 'a list
 (** [remove_if cmp l] is similar to [remove], but with [cmp] used
     instead of ( = ). *)
 
+val remove_at : int -> 'a list -> 'a list
+(** [remove_at i l] returns the list [l] without the element at index [i].
+    @raise Invalid_argument if [i] is outside of [l] size bounds.
+
+    @since NEXT_RELEASE
+
+*)
+
 val remove_all : 'a list -> 'a -> 'a list
 (** [remove_all l x] is similar to [remove] but removes all elements that
     are equal to [x] and not only the first one. *)
@@ -544,7 +552,7 @@ val ntake : int -> 'a list -> 'a list list
     Each list in the result has size n, except the last
     one which may have fewer elements in case [l] was too short.
     Example: [ntake 2 [1; 2; 3; 4; 5] = [[1; 2]; [3; 4]; [5]]]
-    
+
     @since 2.2.0 *)
 
 val drop : int -> 'a list -> 'a list