Adding a "get" primitive to map signature.

It is similar to find but raises an assertion failure instead of a Not_found
when the element is not encountered. Using it will give stronger invariants.

3 files changed, 7 insertions, 0 deletions

diff --git a/lib/cMap.ml b/lib/cMap.ml
index d1a32b7aa..4b058380c 100644
--- a/lib/cMap.ml
+++ b/lib/cMap.ml
@@ -25,6 +25,7 @@ module type ExtS =
 sig
   include CSig.MapS
   module Set : CSig.SetS with type elt = key
+  val get : key -> 'a t -> 'a
   val update : key -> 'a -> 'a t -> 'a t
   val modify : key -> (key -> 'a -> 'a) -> 'a t -> 'a t
   val domain : 'a t -> Set.t
@@ -207,4 +208,5 @@ module Make(M : Map.OrderedType) =
 struct
   include Map.Make(M)
   include MapExt(M)
+  let get k m = try find k m with Not_found -> assert false
 end
diff --git a/lib/cMap.mli b/lib/cMap.mli
index 464dc503b..3ef7fa2c8 100644
--- a/lib/cMap.mli
+++ b/lib/cMap.mli
@@ -31,6 +31,9 @@ sig
   module Set : CSig.SetS with type elt = key
   (** Sets used by the domain function *)
 
+  val get : key -> 'a t -> 'a
+  (** Same as {!find} but fails an assertion instead of raising [Not_found] *)
+
   val update : key -> 'a -> 'a t -> 'a t
   (** Same as [add], but expects the key to be present, and thus faster.
       @raise Not_found when the key is unbound in the map. *)
diff --git a/lib/hMap.ml b/lib/hMap.ml
index 220adc28f..778c366fd 100644
--- a/lib/hMap.ml
+++ b/lib/hMap.ml
@@ -286,6 +286,8 @@ struct
     let m = Int.Map.find h s in
     Map.find k m
 
+  let get k s = try find k s with Not_found -> assert false
+
   let split k s = assert false (** Cannot be implemented efficiently *)
 
   let map f s =