diff --git a/src/dune b/src/dune
index 540a6bb..3725251 100644
--- a/src/dune
+++ b/src/dune
@@ -1,5 +1,5 @@
 (library
   (name mew)
   (public_name mew)
-  (libraries result)
+  (libraries result trie)
   (flags (:standard -safe-string)))
diff --git a/src/trie.ml b/src/trie.ml
deleted file mode 100644
index 00b6a24..0000000
--- a/src/trie.ml
+++ /dev/null
@@ -1,78 +0,0 @@
-(*
- * trie.ml
- * -----------
- * Copyright : (c) 2019 - 2020, ZAN DoYe <zandoye@gmail.com>
- * Licence   : MIT
- *
- * This file is a part of mew.
- *)
-
-module type S = sig
-  type path
-  type 'a node
-  val create : 'a option -> 'a node
-  val get : 'a node -> path -> 'a option
-  val set : 'a node -> path -> 'a -> unit
-  val unset : 'a node -> path -> unit
-  val sub: 'a node -> path -> 'a node option
-  val is_leaf: 'a node -> bool
-end
-
-module Make (H:Hashtbl.HashedType): (S with type path= H.t list) = struct
-  module Path = Hashtbl.Make(H)
-
-  type path= H.t list
-
-  type 'a node= {
-    mutable value: 'a option;
-    next: 'a node Path.t
-  }
-
-  let create value= { value; next= Path.create 0 }
-
-  let append ?(value=None) node key=
-    match Path.find node.next key with
-    | child-> child
-    | exception Not_found->
-        let child= create value in
-        Path.replace node.next key child;
-        child
-
-  let rec set node path value=
-    match path with
-    | []-> node.value <- Some value
-    | hd::tl-> match Path.find node.next hd with
-      | child-> set child tl value
-      | exception Not_found-> set (append node hd) tl value
-
-  let rec get node path=
-    match path with
-    | []-> node.value
-    | hd::tl-> match Path.find node.next hd with
-      | child-> get child tl
-      | exception Not_found-> None
-
-  let unset node path=
-    let rec unset node path=
-      match path with
-      | []-> node.value <- None; true
-      | hd::tl-> match Path.find node.next hd with
-        | child->
-          if unset child tl then
-            if Path.length child.next = 0 && child.value = None
-            then (Path.remove node.next hd; true)
-            else false
-          else false
-        | exception Not_found-> false
-    in unset node path |> ignore
-
-  let rec sub node path=
-    match path with
-    | []-> Some node
-    | hd::tl-> match Path.find node.next hd with
-      | child-> sub child tl
-      | exception Not_found-> None
-
-  let is_leaf node= Path.length node.next = 0
-end
-
diff --git a/src/trie.mli b/src/trie.mli
deleted file mode 100644
index 7b0d44f..0000000
--- a/src/trie.mli
+++ /dev/null
@@ -1,39 +0,0 @@
-(*
- * trie.mli
- * -----------
- * Copyright : (c) 2019 - 2020, ZAN DoYe <zandoye@gmail.com>
- * Licence   : MIT
- *
- * This file is a part of mew.
- * This module implements strict impure trie tree data structure.
- *)
-
-module type S =
-  sig
-    (** type of path point *)
-    type path
-
-    (** type of trie node *)
-    type 'a node
-
-    (** create a new trie tree with or without an element *)
-    val create : 'a option -> 'a node
-
-    (** returns the value associated with the path *)
-    val get : 'a node -> path -> 'a option
-
-    (** associate the value with the path *)
-    val set : 'a node -> path -> 'a -> unit
-
-    (** remove an association of the path *)
-    val unset : 'a node -> path -> unit
-
-    (** returns the sub node associated with the path *)
-    val sub: 'a node -> path -> 'a node option
-
-    (** [is_leaf node] returns whether the [node] is leaf *)
-    val is_leaf: 'a node -> bool
-  end
-
-module Make (H : Hashtbl.HashedType): S with type path= H.t list
-