Index: src/natools-constant_indefinite_ordered_maps.adb
==================================================================
--- src/natools-constant_indefinite_ordered_maps.adb
+++ src/natools-constant_indefinite_ordered_maps.adb
@@ -570,10 +570,28 @@
      return Map_Iterator_Interfaces.Reversible_Iterator'Class is
    begin
       return Iterator'(Backend => Container.Backend, Start => Start);
    end Iterate;
 
+
+   function Iterate (Container : in Constant_Map; First, Last : in Cursor)
+     return Map_Iterator_Interfaces.Reversible_Iterator'Class is
+   begin
+      if Is_Empty (Container)
+        or else not Has_Element (First)
+        or else not Has_Element (Last)
+        or else First > Last
+      then
+         return Iterator'(Backend => Backend_Refs.Null_Immutable_Reference,
+           Start => No_Element);
+      else
+         return Range_Iterator'(Backend => Container.Backend,
+                                First_Position => First,
+                                Last_Position => Last);
+      end if;
+   end Iterate;
+
 
    function Last (Container : Constant_Map) return Cursor is
    begin
       if Container.Is_Empty then
          return No_Element;
@@ -726,6 +744,42 @@
             Backend => Object.Backend,
             Index => Object.Backend.Query.Data.Size);
       end if;
    end Last;
 
+
+   overriding function First (Object : Range_Iterator) return Cursor is
+   begin
+      return Object.First_Position;
+   end First;
+
+
+   overriding function Last  (Object : Range_Iterator) return Cursor is
+   begin
+      return Object.Last_Position;
+   end Last;
+
+
+   overriding function Next
+     (Object   : Range_Iterator;
+      Position : Cursor) return Cursor is
+   begin
+      if Has_Element (Position) and then Position < Object.Last_Position then
+         return Next (Position);
+      else
+         return No_Element;
+      end if;
+   end Next;
+
+
+   overriding function Previous
+     (Object   : Range_Iterator;
+      Position : Cursor) return Cursor is
+   begin
+      if Has_Element (Position) and then Position > Object.First_Position then
+         return Previous (Position);
+      else
+         return No_Element;
+      end if;
+   end Previous;
+
 end Natools.Constant_Indefinite_Ordered_Maps;

Index: src/natools-constant_indefinite_ordered_maps.ads
==================================================================
--- src/natools-constant_indefinite_ordered_maps.ads
+++ src/natools-constant_indefinite_ordered_maps.ads
@@ -171,10 +171,13 @@
      return Map_Iterator_Interfaces.Reversible_Iterator'Class;
 
    function Iterate (Container : in Constant_Map; Start : in Cursor)
      return Map_Iterator_Interfaces.Reversible_Iterator'Class;
 
+   function Iterate (Container : in Constant_Map; First, Last : in Cursor)
+     return Map_Iterator_Interfaces.Reversible_Iterator'Class;
+
 
    type Constant_Reference_Type
      (Element : not null access constant Element_Type) is private
      with Implicit_Dereference => Element;
 
@@ -340,12 +343,41 @@
 
    overriding function Previous
      (Object   : Iterator;
       Position : Cursor) return Cursor
      is (Previous (Position))
+     with Pre => Position.Is_Empty
+        or else Backend_Refs."=" (Position.Backend, Object.Backend);
+
+
+   type Range_Iterator is new Map_Iterator_Interfaces.Reversible_Iterator
+   with record
+      Backend : Backend_Refs.Immutable_Reference;
+      First_Position : Cursor;
+      Last_Position : Cursor;
+   end record;
+--   with Dynamic_Predicate => not Range_Iterator.Backend.Is_Empty
+--      and then Has_Element (Range_Iterator.First_Position)
+--      and then Has_Element (Range_Iterator.Last_Position)
+--      and then not Range_Iterator.First_Position
+--         > Range_Iterator.Last_Position;
+
+   overriding function First (Object : Range_Iterator) return Cursor;
+
+   overriding function Last  (Object : Range_Iterator) return Cursor;
+
+   overriding function Next
+     (Object   : Range_Iterator;
+      Position : Cursor) return Cursor
+     with Pre => Position.Is_Empty
+        or else Backend_Refs."=" (Position.Backend, Object.Backend);
+
+   overriding function Previous
+     (Object   : Range_Iterator;
+      Position : Cursor) return Cursor
      with Pre => Position.Is_Empty
         or else Backend_Refs."=" (Position.Backend, Object.Backend);
 
 
    No_Element : constant Cursor := (Is_Empty => True);
 
 end Natools.Constant_Indefinite_Ordered_Maps;