From e530547356f9b6a5cf9caeb4b90320cb45ec3382 Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Thu, 26 Jul 2018 04:39:06 -0500
Subject: [PATCH] feat(vector): add `Vector.{filter,filter_map}_in_place`

---
 src/core/CCVector.ml  | 41 +++++++++++++++++++++++++++++++++++++++++
 src/core/CCVector.mli |  8 ++++++++
 2 files changed, 49 insertions(+)

diff --git a/src/core/CCVector.ml b/src/core/CCVector.ml
index 696c2bc1..cf19390b 100644
--- a/src/core/CCVector.ml
+++ b/src/core/CCVector.ml
@@ -483,6 +483,24 @@ let map f v =
   to_list (map string_of_int v) = ["1"; "2"; "3"]
 *)
 
+(*$QR
+  Q.(pair (fun1 Observable.int small_int) (small_list small_int)) (fun (Q.Fun (_,f),l) ->
+    let v = of_list l in
+    to_list (map f v) = List.map f l)
+*)
+
+let map_in_place f v =
+  iteri
+    (fun i x -> Array.unsafe_set v.vec i (f x))
+    v
+
+(*$QR
+  Q.(pair (fun1 Observable.int small_int) (small_list small_int)) (fun (Q.Fun (_,f),l) ->
+    let v = of_list l in
+    map_in_place f v;
+    to_list v = List.map f l)
+*)
+
 let filter' p v =
   let i = ref 0 in (* cur element *)
   let j = ref 0 in  (* cur insertion point *)
@@ -638,6 +656,29 @@ let filter_map f v =
     to_list (filter_map f v) = CCList.filter_map f l)
 *)
 
+let filter_map_in_place f v =
+  let i = ref 0 in (* cur element *)
+  let j = ref 0 in  (* cur insertion point *)
+  let n = v.size in
+  while !i < n do
+    match f v.vec.(!i) with
+      | None -> incr i (* drop *)
+      | Some y ->
+        (* move element i at the first empty slot.
+           invariant: i >= j*)
+        v.vec.(!j) <- y;
+        incr i;
+        incr j
+  done;
+  v.size <- !j
+
+(*$QR
+  Q.(pair (fun1 Observable.int (option small_int)) (small_list small_int)) (fun (Q.Fun (_,f),l) ->
+    let v = of_list l in
+    filter_map_in_place f v;
+    to_list v = CCList.filter_map f l)
+*)
+
 let flat_map f v =
   let v' = create () in
   iter (fun x -> iter (push v') (f x)) v;
diff --git a/src/core/CCVector.mli b/src/core/CCVector.mli
index 3b1f4f17..80ed0a2f 100644
--- a/src/core/CCVector.mli
+++ b/src/core/CCVector.mli
@@ -141,6 +141,10 @@ val iteri : (int -> 'a -> unit) -> ('a,_) t -> unit
 val map : ('a -> 'b) -> ('a,_) t -> ('b, 'mut) t
 (** Map elements of the vector, yielding a new vector. *)
 
+val map_in_place : ('a -> 'a) -> ('a,_) t -> unit
+(** Map elements of the vector in place
+    @since NEXT_RELEASE *)
+
 val filter : ('a -> bool) -> ('a,_) t -> ('a, 'mut) t
 (** Filter elements from the vector. [filter p v] leaves [v] unchanged but
     returns a new vector that only contains elements of [v] satisfying [p]. *)
@@ -172,6 +176,10 @@ val find_map : ('a -> 'b option) -> ('a,_) t -> 'b option
 val filter_map : ('a -> 'b option) -> ('a,_) t -> ('b, 'mut) t
 (** Map elements with a function, possibly filtering some of them out. *)
 
+val filter_map_in_place : ('a -> 'a option) -> ('a,_) t -> unit
+(** Filter-map elements of the vector in place
+    @since NEXT_RELEASE *)
+
 val flat_map : ('a -> ('b,_) t) -> ('a,_) t -> ('b, 'mut) t
 (** Map each element to a sub-vector. *)