Index: src/natools-s_expressions-generic_caches.adb
==================================================================
--- src/natools-s_expressions-generic_caches.adb
+++ src/natools-s_expressions-generic_caches.adb
@@ -179,10 +179,23 @@
       end Dup_Tree;
    begin
       return Reference'(Exp => Trees.Create (Dup_Tree'Access));
    end Duplicate;
 
+
+   function Move (Source : in out S_Expressions.Descriptor'Class)
+     return Reference
+   is
+      Result : Reference;
+   begin
+      Printers.Transfer
+        (Source => Source,
+         Target => Result,
+         Check_Level => True);
+      return Result;
+   end Move;
+
 
 
    -----------------------
    -- Printer Interface --
    -----------------------

Index: src/natools-s_expressions-generic_caches.ads
==================================================================
--- src/natools-s_expressions-generic_caches.ads
+++ src/natools-s_expressions-generic_caches.ads
@@ -53,10 +53,14 @@
    overriding procedure Close_List (Output : in out Reference);
 
    function Duplicate (Cache : Reference) return Reference;
       --  Create a new copy of the S-expression held in Cache and return it
 
+   function Move (Source : in out S_Expressions.Descriptor'Class)
+     return Reference;
+      --  Build a new cache by (destructively) reading Original
+
 
    type Cursor is new Lockable.Descriptor and Replayable.Descriptor
      with private;
    pragma Preelaborable_Initialization (Cursor);
 
@@ -84,10 +88,15 @@
 
    overriding function Duplicate (Object : Cursor) return Cursor;
 
    function First (Cache : Reference'Class) return Cursor;
       --  Create a new Cursor pointing at the beginning of Cache
+
+   function Move (Source : in out S_Expressions.Descriptor'Class) return Cursor
+     is (Move (Source).First);
+      --  Return a cursor holding a copy of Original (which is
+      --  destructively read)
 
 private
 
    type Atom_Access is access Atom;
    for Atom_Access'Storage_Pool use Atom_Pool;