fix(vector): bugfix in filter

src/core/CCVector.ml

@@ -471,13 +471,13 @@ let filter' p v =
 *)
 
 let filter p v =
-  if array_is_empty_ v
-  then create ()
-  else (
+  if array_is_empty_ v then (
+    create ()
+  ) else (
     let v' = create_with ~capacity:v.size v.vec.(0) in
-    Array.iter
+    iter
       (fun x -> if p x then push_unsafe_ v' x)
-      v.vec;
+      v;
     v'
   )
 
@@ -486,6 +486,12 @@ let filter p v =
   filter (fun x-> x mod 2=0) (1 -- 1_000_000) |> length = 500_000
 *)
 
+(*$QR
+  Q.(pair (fun1 Observable.int bool) (small_list small_int)) (fun (Q.Fun (_,f),l) ->
+    let v = of_list l in
+    to_list (filter f v) = List.filter f l)
+*)
+
 let fold f acc v =
   let rec fold acc i =
     if i = v.size then acc