diff --git a/cn-lsp/server/lib/lspCn.ml b/cn-lsp/server/lib/lspCn.ml
index 0332912..ca8b8f3 100644
--- a/cn-lsp/server/lib/lspCn.ml
+++ b/cn-lsp/server/lib/lspCn.ml
@@ -6,10 +6,8 @@ module CF = Cerb_frontend
 module CG = Cerb_global
 
 (* LSP *)
-module LspDocumentUri = Lsp.Types.DocumentUri
-module LspPosition = Lsp.Types.Position
-module LspRange = Lsp.Types.Range
 module LspDiagnostic = Lsp.Types.Diagnostic
+module LspDocumentUri = Lsp.Types.DocumentUri
 
 module CerbM = struct
   type error = CF.Errors.error
@@ -28,21 +26,16 @@ end
 module Cerb = struct
   open CerbM
 
-  let loc_to_source_range (loc : Cerb_location.t) : (string * LspRange.t) option =
-    let posn_to_lsp (p : Lexing.position) : LspPosition.t =
-      LspPosition.create ~line:(p.pos_lnum - 1) ~character:(p.pos_cnum - p.pos_bol)
+  let loc_to_source_range (loc : Cerb_location.t) : (string * Range.t) option =
+    let path_opt =
+      match Cn.Locations.start_pos loc, Cn.Locations.end_pos loc with
+      | Some pos, _ | _, Some pos -> Some pos.pos_fname
+      | _ -> None
     in
-    match Cn.Locations.start_pos loc, Cn.Locations.end_pos loc with
-    | Some start, Some end_ ->
-      (* TODO: handle when start and end have different filenames? *)
-      let path = start.pos_fname in
-      let range = LspRange.create ~start:(posn_to_lsp start) ~end_:(posn_to_lsp end_) in
-      Some (path, range)
-    | Some pos, None | None, Some pos ->
-      let path = pos.pos_fname in
-      let range = LspRange.create ~start:(posn_to_lsp pos) ~end_:(posn_to_lsp pos) in
-      Some (path, range)
-    | None, None -> None
+    let range_opt = Range.of_cerb_loc loc in
+    match path_opt, range_opt with
+    | Some path, Some range -> Some (path, range)
+    | _ -> None
   ;;
 
   let error_to_string ((loc, cause) : error) : string = CF.Pp_errors.to_string (loc, cause)
diff --git a/cn-lsp/server/lib/position.ml b/cn-lsp/server/lib/position.ml
new file mode 100644
index 0000000..1b2087e
--- /dev/null
+++ b/cn-lsp/server/lib/position.ml
@@ -0,0 +1,20 @@
+open! Base
+
+type t = Lsp.Types.Position.t
+
+let create ~(line : int) ~(character : int) = Lsp.Types.Position.create ~line ~character
+let eq (p1 : t) (p2 : t) : bool = p1.line = p2.line && p1.character = p2.character
+
+let lt (p1 : t) (p2 : t) : bool =
+  p1.line < p2.line || (p1.line = p2.line && p1.character < p2.character)
+;;
+
+let le (p1 : t) (p2 : t) : bool = lt p1 p2 || eq p1 p2
+
+let gt (p1 : t) (p2 : t) : bool =
+  p1.line > p2.line || (p1.line = p2.line && p1.character > p2.character)
+;;
+
+let ge (p1 : t) (p2 : t) : bool = gt p1 p2 || eq p1 p2
+let compare (p1 : t) (p2 : t) : int = if lt p1 p2 then -1 else if gt p1 p2 then 1 else 0
+let to_string (p : t) : string = Printf.sprintf "%i:%i" p.line p.character
diff --git a/cn-lsp/server/lib/position.mli b/cn-lsp/server/lib/position.mli
new file mode 100644
index 0000000..f9c1e51
--- /dev/null
+++ b/cn-lsp/server/lib/position.mli
@@ -0,0 +1,12 @@
+open! Base
+
+type t = Lsp.Types.Position.t
+
+val create : line:int -> character:int -> t
+val compare : t -> t -> int
+val lt : t -> t -> bool
+val le : t -> t -> bool
+val eq : t -> t -> bool
+val ge : t -> t -> bool
+val gt : t -> t -> bool
+val to_string : t -> string
diff --git a/cn-lsp/server/lib/range.ml b/cn-lsp/server/lib/range.ml
new file mode 100644
index 0000000..3337005
--- /dev/null
+++ b/cn-lsp/server/lib/range.ml
@@ -0,0 +1,26 @@
+open! Base
+
+type t = Lsp.Types.Range.t
+
+let create ~(start : Position.t) ~(end_ : Position.t) : t =
+  Lsp.Types.Range.create ~start ~end_
+;;
+
+let to_string (range : t) : string =
+  Printf.sprintf "%s-%s" (Position.to_string range.start) (Position.to_string range.end_)
+;;
+
+let ( |--| ) ((l1, c1) : int * int) ((l2, c2) : int * int) : t =
+  create
+    ~start:(Position.create ~line:l1 ~character:c1)
+    ~end_:(Position.create ~line:l2 ~character:c2)
+;;
+
+let of_cerb_loc (loc : Cerb_location.t) : t option =
+  match Cerb_location.to_cartesian loc with
+  | None -> None
+  | Some ((l1, c1), (l2, c2)) ->
+    let start = Position.create ~line:l1 ~character:c1 in
+    let end_ = Position.create ~line:l2 ~character:c2 in
+    Some (create ~start ~end_)
+;;
diff --git a/cn-lsp/server/lib/range.mli b/cn-lsp/server/lib/range.mli
new file mode 100644
index 0000000..9f94d5d
--- /dev/null
+++ b/cn-lsp/server/lib/range.mli
@@ -0,0 +1,11 @@
+open! Base
+
+type t = Lsp.Types.Range.t
+
+val create : start:Position.t -> end_:Position.t -> t
+val to_string : t -> string
+
+(** Convenience notation: [(begin_line, begin_char) |--| (end_line, end_char)] *)
+val ( |--| ) : int * int -> int * int -> t
+
+val of_cerb_loc : Cerb_location.t -> t option