diff --git a/bench/line_rope_svelte b/bench/line_rope_svelte
deleted file mode 100755
index b623392..0000000
Binary files a/bench/line_rope_svelte and /dev/null differ
diff --git a/src/gap_map.sml b/src/gap_map.sml
new file mode 100644
index 0000000..17a8d2e
--- /dev/null
+++ b/src/gap_map.sml
@@ -0,0 +1,52 @@
+signature GAP_MAP_PAIR =
+sig
+  type key
+  type value
+
+  val l: key * key -> bool
+  val eq: key * key -> bool
+  val g: key * key -> bool
+
+  val maxNodeSize: int
+end
+
+signature GAP_MAP =
+sig
+  structure Fn: GAP_MAP_PAIR
+
+  type t
+
+  val empty: t
+  val isEmpty: t -> bool
+
+  val add: Fn.key * Fn.value * t -> t
+  val remove: Fn.key * t -> t
+
+  val get: Fn.key * t -> Fn.value option
+  val min: t -> (Fn.key * Fn.value) option
+  val max: t -> (Fn.key * Fn.value) option
+
+  val moveToStart: t -> t
+  val moveToEnd: t -> t
+  val moveTo: Fn.key * t -> t
+end
+
+functor MakeGapMap(Fn: GAP_MAP_PAIR): GAP_MAP =
+struct
+  structure Fn = Fn
+
+  type t =
+    { leftKeys: Fn.key vector list
+    , letVals: Fn.value vector list
+    , rightKeys: Fn.key vector list
+    , rightVals: Fn.value vector list
+    }
+
+  val empty = {leftKeys = [], leftVals = [], rightKeys = [], rightVals = []}
+
+  fun isEmpty {leftKeys = [], rightKeys = [], ...} = true
+    | isEmpty _ = false
+
+  fun isLessThanTarget (v1, v2) =
+    Vector.length v1 + Vector.length v2 <= Fn.maxNodeSize
+end
diff --git a/src/gap_set.sml b/src/gap_set.sml
index 99d3bd4..94ab607 100644
--- a/src/gap_set.sml
+++ b/src/gap_set.sml
@@ -18,6 +18,8 @@ sig
   val empty: t
   val isEmpty: t -> bool
 
+  val singleton: Fn.key -> t
+
   val add: Fn.key * t -> t
   val remove: Fn.key * t -> t
   val removeMany: Fn.key * Fn.key * t -> t
@@ -46,7 +48,7 @@ struct
     | isEmpty _ = false
 
   fun singleton x =
-    {left = [], right = Vector.fromList [x]}
+    {left = [], right = [Vector.fromList [x]]}
 
   fun isLessThanTarget (v1, v2) =
     Vector.length v1 + Vector.length v2 <= Fn.maxNodeSize