2 files changed, 9 insertions, 0 deletions
diff --git a/lib/option.ml b/lib/option.ml
index 02adc69478..1ef45d232e 100644
--- a/lib/option.ml
+++ b/lib/option.ml
@@ -29,6 +29,12 @@ let equal f x y = match x, y with
 | Some x, Some y -> f x y
 | _, _ -> false
 
+let compare f x y = match x, y with
+| None, None -> 0
+| Some x, Some y -> f x y
+| None, Some _ -> -1
+| Some _, None -> 1
+
 exception IsNone
 
 (** [get x] returns [y] where [x] is [Some y]. It raises IsNone
diff --git a/lib/option.mli b/lib/option.mli
index 0b50c588b1..d390edb63a 100644
--- a/lib/option.mli
+++ b/lib/option.mli
@@ -28,6 +28,9 @@ val is_empty : 'a option -> bool
     [f] is called. Otherwise it returns [false]. *)
 val equal : ('a -> 'a -> bool) -> 'a option -> 'a option -> bool
 
+(** Same as [equal], but with comparison. *)
+val compare : ('a -> 'a -> int) -> 'a option -> 'a option -> int
+
 (** [get x] returns [y] where [x] is [Some y]. It raises IsNone
     if [x] equals [None]. *)
 val get : 'a option -> 'a