From f98c7001e17c114ac0a6feaa74eb510ccd8478c4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fran=C3=A7ois=20Pottier?= <francois.pottier@inria.fr>
Date: Thu, 2 Feb 2017 17:31:51 +0100
Subject: [PATCH] New functions [domain] and [codomain].

---
 src/Atom.ml  | 20 ++++++++++++++++++--
 src/Atom.mli | 11 ++++++++++-
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/src/Atom.ml b/src/Atom.ml
index 7315d86..6a42fbc 100644
--- a/src/Atom.ml
+++ b/src/Atom.ml
@@ -139,6 +139,11 @@ module Set = struct
 
   include Set.Make(Order)
 
+  (* A disjointness test. *)
+
+  let disjoint xs ys =
+    is_empty (inter xs ys)
+
   (* Disjoint union. *)
 
   exception NonDisjointUnion of atom
@@ -194,5 +199,16 @@ module Set = struct
 
 end
 
-module Map =
-  Map.Make(Order)
+module Map = struct
+
+  include Map.Make(Order)
+
+  (* This is O(nlog n), whereas in principle O(n) is possible.
+     The abstraction barrier in OCaml's [Set] module hinders us. *)
+  let domain m =
+    fold (fun a _ accu -> Set.add a accu) m Set.empty
+
+  let codomain f m =
+    fold (fun _ v accu -> Set.union (f v) accu) m Set.empty
+
+end
diff --git a/src/Atom.mli b/src/Atom.mli
index 31e5092..fb51599 100644
--- a/src/Atom.mli
+++ b/src/Atom.mli
@@ -28,6 +28,8 @@ val hash: atom -> int
 module Set : sig
   include Set.S with type elt = atom
 
+  val disjoint: t -> t -> bool
+
   (* Disjoint union. *)
 
   exception NonDisjointUnion of atom
@@ -55,4 +57,11 @@ end
 
 (* Maps. *)
 
-module Map : Map.S with type key = atom
+module Map : sig
+
+  include Map.S with type key = atom
+
+  val domain: 'a t -> Set.t
+  val codomain: ('a -> Set.t) -> 'a t -> Set.t
+
+end
-- 
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