From d242d12a27d84971f5e89405bb09fc36def77510 Mon Sep 17 00:00:00 2001
From: Vasilis Papavasileiou <git@vasilis.airpost.net>
Date: Thu, 22 Oct 2015 14:34:52 +0200
Subject: [PATCH 1/2] Linear-time patch operation, if the patch format permits

---
 src/reactiveData.ml | 55 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 54 insertions(+), 1 deletion(-)

diff --git a/src/reactiveData.ml b/src/reactiveData.ml
index 06e81e0..9886ec3 100644
--- a/src/reactiveData.ml
+++ b/src/reactiveData.ml
@@ -206,7 +206,60 @@ module DataList = struct
       end;
       Array.to_list a
 
-  let merge p l = List.fold_left (fun l x -> merge_p x l) l p
+  (* accumulates into acc i unmodified elements from l *)
+  let rec linear_merge_fwd i l ~acc =
+    assert (i >= 0);
+    if i > 0 then
+      match l with
+      | h :: l ->
+        let acc = h :: acc in
+        linear_merge_fwd (i - 1) l ~acc
+      | [] ->
+        failwith "linear_merge_fwd"
+    else
+      l, acc
+
+  let rec linear_merge ?(acc = []) i0 p l =
+    let l, acc =
+      match p with
+      | (I (i, _) | R i | U (i, _)) :: _ when i > i0 ->
+        linear_merge_fwd (i - i0) l ~acc
+      | _ ->
+        l, acc
+    in
+    match p, l with
+    | I (i, x) :: p, _ ->
+      linear_merge ~acc i p (x :: l)
+    | R i :: p, _ :: l ->
+      linear_merge ~acc i p l
+    | R _ :: _, [] ->
+      failwith "ReactiveData.RList.linear_merge: remove from empty"
+    | U (i, x) :: p, _ :: l ->
+      linear_merge ~acc i p (x :: l)
+    | U (_, _) :: _, [] ->
+      failwith "ReactiveData.RList.linear_merge: update empty"
+    | [], l ->
+      List.rev_append acc l
+    | X (_, _) :: _, _ ->
+      failwith "ReactiveData.RList.linear_merge: X not supported"
+
+  let rec linear_mergeable ?(n = 0) p =
+    assert (n >= 0);
+    match p with
+    | (I (i, _) | R i | U (i, _)) :: p when i >= n ->
+      (* negative i's ruled out (among others) *)
+      linear_mergeable ~n:i p
+    | _ :: _ ->
+      false
+    | [] ->
+      true
+
+  let merge p l =
+    if linear_mergeable p then
+      linear_merge 0 p l
+    else
+      List.fold_left (fun l x -> merge_p x l) l p
+
 end
 
 module RList = struct

From 113f5b3ea6ecb96af47d31ae52d0eca8507da9d9 Mon Sep 17 00:00:00 2001
From: Vasilis Papavasileiou <git@vasilis.airpost.net>
Date: Wed, 28 Oct 2015 14:57:38 +0100
Subject: [PATCH 2/2] linear_merge: invalid_arg where applicable; all args
 non-optional

---
 src/reactiveData.ml | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/src/reactiveData.ml b/src/reactiveData.ml
index 9886ec3..dc4db93 100644
--- a/src/reactiveData.ml
+++ b/src/reactiveData.ml
@@ -215,11 +215,11 @@ module DataList = struct
         let acc = h :: acc in
         linear_merge_fwd (i - 1) l ~acc
       | [] ->
-        failwith "linear_merge_fwd"
+        invalid_arg "invalid index"
     else
       l, acc
 
-  let rec linear_merge ?(acc = []) i0 p l =
+  let rec linear_merge i0 p l ~acc =
     let l, acc =
       match p with
       | (I (i, _) | R i | U (i, _)) :: _ when i > i0 ->
@@ -229,34 +229,34 @@ module DataList = struct
     in
     match p, l with
     | I (i, x) :: p, _ ->
-      linear_merge ~acc i p (x :: l)
+      linear_merge i p (x :: l) ~acc
     | R i :: p, _ :: l ->
-      linear_merge ~acc i p l
+      linear_merge i p l ~acc
     | R _ :: _, [] ->
-      failwith "ReactiveData.RList.linear_merge: remove from empty"
+      invalid_arg "merge: invalid index"
     | U (i, x) :: p, _ :: l ->
-      linear_merge ~acc i p (x :: l)
+      linear_merge i p (x :: l) ~acc
     | U (_, _) :: _, [] ->
-      failwith "ReactiveData.RList.linear_merge: update empty"
+      invalid_arg "merge: invalid index"
     | [], l ->
       List.rev_append acc l
     | X (_, _) :: _, _ ->
-      failwith "ReactiveData.RList.linear_merge: X not supported"
+      failwith "linear_merge: X not supported"
 
-  let rec linear_mergeable ?(n = 0) p =
+  let rec linear_mergeable p ~n =
     assert (n >= 0);
     match p with
     | (I (i, _) | R i | U (i, _)) :: p when i >= n ->
       (* negative i's ruled out (among others) *)
-      linear_mergeable ~n:i p
+      linear_mergeable p ~n:i
     | _ :: _ ->
       false
     | [] ->
       true
 
   let merge p l =
-    if linear_mergeable p then
-      linear_merge 0 p l
+    if linear_mergeable p ~n:0 then
+      linear_merge 0 p l ~acc:[]
     else
       List.fold_left (fun l x -> merge_p x l) l p