4 files changed, 21 insertions, 0 deletions
diff --git a/lib/loc.ml b/lib/loc.ml
index 06da13d44f..4a935a9d9c 100644
--- a/lib/loc.ml
+++ b/lib/loc.ml
@@ -62,6 +62,8 @@ let merge_opt l1 l2 = match l1, l2 with
 
 let unloc loc = (loc.bp, loc.ep)
 
+let shift_loc kb kp loc = { loc with bp = loc.bp + kb ; ep = loc.ep + kp }
+
 (** Located type *)
 type 'a located = t option * 'a
 
diff --git a/lib/loc.mli b/lib/loc.mli
index d4061e0446..fde490cc8a 100644
--- a/lib/loc.mli
+++ b/lib/loc.mli
@@ -40,6 +40,11 @@ val merge : t -> t -> t
 val merge_opt : t option -> t option -> t option
 (** Merge locations, usually generating the largest possible span *)
 
+val shift_loc : int -> int -> t -> t
+(** [shift_loc loc n p] shifts the beginning of location by [n] and
+    the end by [p]; it is assumed that the shifts do not change the
+    lines at which the location starts and ends *)
+
 (** {5 Located exceptions} *)
 
 val add_loc : Exninfo.info -> t -> Exninfo.info
diff --git a/lib/util.ml b/lib/util.ml
index 36282b2dac..6de012da0e 100644
--- a/lib/util.ml
+++ b/lib/util.ml
@@ -171,3 +171,12 @@ let open_utf8_file_in fname =
   let s = Bytes.make 3 ' ' in
   if input in_chan s 0 3 < 3 || not (is_bom s) then seek_in in_chan 0;
   in_chan
+
+(** A trick which can typically be used to store on the fly the
+   computation of values in the "when" clause of a "match" then
+   retrieve the evaluated result in the r.h.s of the clause *)
+
+let set_temporary_memory () =
+  let a = ref None in
+  (fun x -> assert (!a = None); a := Some x; x),
+  (fun () -> match !a with Some x -> x | None -> assert false)
diff --git a/lib/util.mli b/lib/util.mli
index d910e7e28e..c54f5825cd 100644
--- a/lib/util.mli
+++ b/lib/util.mli
@@ -137,3 +137,8 @@ val sym : ('a, 'b) eq -> ('b, 'a) eq
 
 val open_utf8_file_in : string -> in_channel
 (** Open an utf-8 encoded file and skip the byte-order mark if any. *)
+
+val set_temporary_memory : unit -> ('a -> 'a) * (unit -> 'a)
+(** A trick which can typically be used to store on the fly the
+   computation of values in the "when" clause of a "match" then
+   retrieve the evaluated result in the r.h.s of the clause *)