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BatArray.remove_at #996

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Dec 23, 2020
Merged

BatArray.remove_at #996

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6 changes: 6 additions & 0 deletions src/batArray.mliv
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Expand Up @@ -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 ->
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16 changes: 16 additions & 0 deletions src/batArray.mlv
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Expand Up @@ -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
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For the record: In theory, Array.init would permit to initialize dst only once taher than twice (first with x, second with actual values). In practice IIRC it's the same under the hood.

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I thought about this.
If it's faster, why not.
I think it might also make the code more readable.
Thanks for the review by the way.

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
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