2 files changed, 22 insertions(+), 0 deletions(-)

M lib/vector.ml
M lib/vector.mli

@@ 207,6 207,24 @@ let update (t : 'a t) (i : int) (value : 'a) : 'a t =
     in
     { t with root = rebuild t.root t.height }
 
+let pop_opt (t : 'a t) : 'a t option =
+  match t.count with
+  | 0 -> None
+  | 1 -> Some (empty ())
+  | count ->
+     (* TODO: handle tree traversal, tail promotion *)
+     if (count - 1) >= (tail_offset t) then
+       (* Shrink tail *)
+       let tail = Array.sub t.tail 0 (Array.length t.tail - 1) in
+       Some { t with tail; count = t.count - 1 }
+     else
+       Some t
+
+let pop (t : 'a t) : 'a t =
+  match pop_opt t with
+  | Some t -> t
+  | None -> invalid_arg "Popping empty vector"
+
 let of_seq (xs : 'a Seq.t) : 'a t =
   Seq.fold_left append (empty ()) xs
 

@@ 17,6 17,10 @@ val append : 'a t -> 'a -> 'a t
 
 val update : 'a t -> int -> 'a -> 'a t
 
+val pop_opt : 'a t -> 'a t option
+
+val pop : 'a t -> 'a t
+
 val of_seq : 'a Seq.t -> 'a t
 
 val to_seq : 'a t -> 'a Seq.t