From 5c11f945b9c02ca77c5ee6959e5e721fece59de5 Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Wed, 15 May 2013 17:59:19 +0200
Subject: [PATCH] update of Bij.version

---
 bij.ml  | 26 +++++++++++++++-----------
 bij.mli |  7 +++----
 2 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/bij.ml b/bij.ml
index d8038505..e9e5da5a 100644
--- a/bij.ml
+++ b/bij.ml
@@ -67,17 +67,6 @@ let guard f t = Guard (f, t)
 let map ~inject ~extract b = Map (inject, extract, b)
 let switch ~inject ~extract = Switch (inject, extract)
 
-(** {2 Helpers} *)
-
-let fix f =
-  let rec bij = lazy (f (fun () -> Lazy.force bij)) in
-  Lazy.force bij
-
-type 'a versioned = string * 'a
-
-let with_version v t =
-  pair (guard (fun v' -> v = v') string_) t
-
 (** {2 Exceptions} *)
 
 exception EOF
@@ -88,6 +77,21 @@ exception EncodingError of string
 exception DecodingError of string
   (** Raised when decoding is impossible *)
 
+(** {2 Helpers} *)
+
+let fix f =
+  let rec bij = lazy (f (fun () -> Lazy.force bij)) in
+  Lazy.force bij
+
+let with_version v t =
+  map
+    ~inject:(fun x -> v, x)
+    ~extract:(fun (v', x) ->
+      if v = v'
+        then x
+        else raise (DecodingError ("expected version " ^ v)))
+    (pair string_ t)
+
 (** {2 Source of parsing} *)
 
 module type SOURCE = sig
diff --git a/bij.mli b/bij.mli
index 14dc0525..41d8217a 100644
--- a/bij.mli
+++ b/bij.mli
@@ -64,10 +64,9 @@ val switch : inject:('a -> char * 'a inject_branch) ->
 val fix : ((unit -> 'a t) -> 'a t) -> 'a t
   (** Helper for recursive encodings *)
 
-type 'a versioned = string * 'a
-
-val with_version : string -> 'a t -> 'a versioned t
-  (** Guards the values with a given version *)
+val with_version : string -> 'a t -> 'a t
+  (** Guards the values with a given version. Only values encoded with
+      the same version will fit. *)
 
 (** {2 Exceptions} *)