[Ada] Clean ups in container API

Index: a-cdlili.adb
===================================================================
--- a-cdlili.adb	(revision 183051)
+++ a-cdlili.adb	(working copy)
@@ -219,6 +219,29 @@ 
       pragma Warnings (On);
    end Clear;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased List;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
+
+      pragma Assert (Vet (Position), "bad cursor in Constant_Reference");
+
+      return (Element => Position.Node.Element'Access);
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -1277,31 +1300,22 @@ 
    -- Reference --
    ---------------
 
-   function Constant_Reference
-     (Container : List;
-      Position  : Cursor) return Constant_Reference_Type
+   function Reference
+     (Container : aliased in out List;
+      Position  : Cursor) return Reference_Type
    is
    begin
-      pragma Unreferenced (Container);
-
       if Position.Container = null then
          raise Constraint_Error with "Position cursor has no element";
       end if;
 
-      return (Element => Position.Node.Element'Access);
-   end Constant_Reference;
+      if Position.Container /= Container'Unchecked_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
 
-   function Reference
-     (Container : List;
-      Position  : Cursor) return Reference_Type
-   is
-   begin
-      pragma Unreferenced (Container);
+      pragma Assert (Vet (Position), "bad cursor in function Reference");
 
-      if Position.Container = null then
-         raise Constraint_Error with "Position cursor has no element";
-      end if;
-
       return (Element => Position.Node.Element'Access);
    end Reference;
 
Index: a-cdlili.ads
===================================================================
--- a-cdlili.ads	(revision 183051)
+++ a-cdlili.ads	(working copy)
@@ -90,6 +90,48 @@ 
       Position  : Cursor;
       Process   : not null access procedure (Element : in out Element_Type));
 
+   type Constant_Reference_Type
+      (Element : not null access constant Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Constant_Reference_Type);
+
+   for Constant_Reference_Type'Write use Write;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Constant_Reference_Type);
+
+   for Constant_Reference_Type'Read use Read;
+
+   type Reference_Type
+     (Element : not null access Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Reference_Type);
+
+   for Reference_Type'Write use Write;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Reference_Type);
+
+   for Reference_Type'Read use Read;
+
+   function Constant_Reference
+     (Container : aliased List;
+      Position  : Cursor) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out List;
+      Position  : Cursor) return Reference_Type;
+
    procedure Assign (Target : in out List; Source : List);
 
    function Copy (Source : List) return List;
@@ -222,48 +264,6 @@ 
 
    end Generic_Sorting;
 
-   type Constant_Reference_Type
-      (Element : not null access constant Element_Type) is private
-   with
-      Implicit_Dereference => Element;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Constant_Reference_Type);
-
-   for Constant_Reference_Type'Write use Write;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Constant_Reference_Type);
-
-   for Constant_Reference_Type'Read use Read;
-
-   type Reference_Type (Element : not null access Element_Type) is
-   private
-   with
-      Implicit_Dereference => Element;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Reference_Type);
-
-   for Reference_Type'Write use Write;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Reference_Type);
-
-   for Reference_Type'Read use Read;
-
-   function Constant_Reference
-     (Container : List; Position : Cursor)    --  SHOULD BE ALIASED
-   return Constant_Reference_Type;
-
-   function Reference
-     (Container : List; Position : Cursor)    --  SHOULD BE ALIASED
-   return Reference_Type;
-
 private
 
    pragma Inline (Next);
Index: a-cihama.adb
===================================================================
--- a-cihama.adb	(revision 183051)
+++ a-cihama.adb	(working copy)
@@ -189,6 +189,55 @@ 
       HT_Ops.Clear (Container.HT);
    end Clear;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong map";
+      end if;
+
+      if Position.Node.Element = null then
+         raise Program_Error with
+           "Position cursor has no element";
+      end if;
+
+      pragma Assert
+        (Vet (Position),
+         "Position cursor in Constant_Reference is bad");
+
+      return (Element => Position.Node.Element.all'Access);
+   end Constant_Reference;
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Key       : Key_Type) return Constant_Reference_Type
+   is
+      Node : constant Node_Access := Key_Ops.Find (Container.HT, Key);
+
+   begin
+      if Node = null then
+         raise Constraint_Error with "key not in map";
+      end if;
+
+      if Node.Element = null then
+         raise Program_Error with "key has no element";
+      end if;
+
+      return (Element => Node.Element.all'Access);
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -955,31 +1004,49 @@ 
    -- Reference --
    ---------------
 
-   function Constant_Reference
-     (Container : Map;
-      Key       : Key_Type) return Constant_Reference_Type
+   function Reference
+     (Container : aliased in out Map;
+      Position  : Cursor) return Reference_Type
    is
    begin
-      return (Element =>
-        Container.Find (Key).Node.Element.all'Unrestricted_Access);
-   end Constant_Reference;
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
 
-   function Reference
-     (Container : Map;
-      Key       : Key_Type) return Reference_Type
-   is
-   begin
-      return (Element =>
-         Container.Find (Key).Node.Element.all'Unrestricted_Access);
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong map";
+      end if;
+
+      if Position.Node.Element = null then
+         raise Program_Error with
+           "Position cursor has no element";
+      end if;
+
+      pragma Assert
+        (Vet (Position),
+         "Position cursor in function Reference is bad");
+
+      return (Element => Position.Node.Element.all'Access);
    end Reference;
 
    function Reference
      (Container : aliased in out Map;
-      Position  : Cursor) return Reference_Type
+      Key       : Key_Type) return Reference_Type
    is
-      pragma Unreferenced (Container);
+      Node : constant Node_Access := Key_Ops.Find (Container.HT, Key);
+
    begin
-      return (Element => Element (Position)'Unrestricted_Access);
+      if Node = null then
+         raise Constraint_Error with "key not in map";
+      end if;
+
+      if Node.Element = null then
+         raise Program_Error with "key has no element";
+      end if;
+
+      return (Element => Node.Element.all'Access);
    end Reference;
 
    -------------
Index: a-cihama.ads
===================================================================
--- a-cihama.ads	(revision 183051)
+++ a-cihama.ads	(working copy)
@@ -134,6 +134,55 @@ 
    --  Calls Process with the key (with only a constant view) and element (with
    --  a variable view) of the node designed by the cursor.
 
+   type Constant_Reference_Type
+      (Element : not null access constant Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Constant_Reference_Type);
+
+   for Constant_Reference_Type'Write use Write;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Constant_Reference_Type);
+
+   for Constant_Reference_Type'Read use Read;
+
+   type Reference_Type (Element : not null access Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Reference_Type);
+
+   for Reference_Type'Write use Write;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Reference_Type);
+
+   for Reference_Type'Read use Read;
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Position  : Cursor) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out Map;
+      Position  : Cursor) return Reference_Type;
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Key       : Key_Type) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out Map;
+      Key       : Key_Type) return Reference_Type;
+
    procedure Assign (Target : in out Map; Source : Map);
 
    function Copy (Source : Map; Capacity : Count_Type := 0) return Map;
@@ -255,52 +304,6 @@ 
    --  Returns the result of calling Equivalent_Keys with key Left and the node
    --  designated by Right.
 
-   type Constant_Reference_Type
-      (Element : not null access constant Element_Type) is private
-   with
-      Implicit_Dereference => Element;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Constant_Reference_Type);
-
-   for Constant_Reference_Type'Write use Write;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Constant_Reference_Type);
-
-   for Constant_Reference_Type'Read use Read;
-
-   type Reference_Type (Element : not null access Element_Type) is private
-   with
-      Implicit_Dereference => Element;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Reference_Type);
-
-   for Reference_Type'Write use Write;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Reference_Type);
-
-   for Reference_Type'Read use Read;
-
-   function Constant_Reference
-     (Container : Map;
-      Key       : Key_Type)    --  SHOULD BE ALIASED ???
-      return Constant_Reference_Type;
-
-   function Reference
-     (Container : Map;
-      Key       : Key_Type) return Reference_Type;
-
-   function Reference
-     (Container : aliased in out Map;
-      Position  : Cursor) return Reference_Type;
-
    procedure Iterate
      (Container : Map;
       Process   : not null access procedure (Position : Cursor));
Index: a-coinve.adb
===================================================================
--- a-coinve.adb	(revision 183051)
+++ a-coinve.adb	(working copy)
@@ -673,34 +673,51 @@ 
    ------------------------
 
    function Constant_Reference
-     (Container : Vector;
+     (Container : aliased Vector;
       Position  : Cursor) return Constant_Reference_Type
    is
+      E : Element_Access;
+
    begin
-      pragma Unreferenced (Container);
-
       if Position.Container = null then
          raise Constraint_Error with "Position cursor has no element";
       end if;
 
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with "Position cursor denotes wrong container";
+      end if;
+
       if Position.Index > Position.Container.Last then
          raise Constraint_Error with "Position cursor is out of range";
       end if;
 
-      return
-       (Element => Position.Container.Elements.EA (Position.Index).all'Access);
+      E := Container.Elements.EA (Position.Index);
+
+      if E = null then
+         raise Constraint_Error with "element at Position is empty";
+      end if;
+
+      return (Element => E.all'Access);
    end Constant_Reference;
 
    function Constant_Reference
-     (Container : Vector;
-      Position  : Index_Type) return Constant_Reference_Type
+     (Container : aliased Vector;
+      Index     : Index_Type) return Constant_Reference_Type
    is
+      E : Element_Access;
+
    begin
-      if (Position) > Container.Last then
+      if Index > Container.Last then
          raise Constraint_Error with "Index is out of range";
       end if;
 
-      return (Element => Container.Elements.EA (Position).all'Access);
+      E := Container.Elements.EA (Index);
+
+      if E = null then
+         raise Constraint_Error with "element at Index is empty";
+      end if;
+
+      return (Element => E.all'Access);
    end Constant_Reference;
 
    --------------
@@ -2998,35 +3015,51 @@ 
    ---------------
 
    function Reference
-     (Container : Vector;
+     (Container : aliased in out Vector;
       Position  : Cursor) return Reference_Type
    is
+      E : Element_Access;
+
    begin
-      pragma Unreferenced (Container);
-
       if Position.Container = null then
          raise Constraint_Error with "Position cursor has no element";
       end if;
 
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with "Position cursor denotes wrong container";
+      end if;
+
       if Position.Index > Position.Container.Last then
          raise Constraint_Error with "Position cursor is out of range";
       end if;
 
-      return
-        (Element =>
-           Position.Container.Elements.EA (Position.Index).all'Access);
+      E := Container.Elements.EA (Position.Index);
+
+      if E = null then
+         raise Constraint_Error with "element at Position is empty";
+      end if;
+
+      return (Element => E.all'Access);
    end Reference;
 
    function Reference
-     (Container : Vector;
-      Position  : Index_Type) return Reference_Type
+     (Container : aliased in out Vector;
+      Index     : Index_Type) return Reference_Type
    is
+      E : Element_Access;
+
    begin
-      if Position > Container.Last then
+      if Index > Container.Last then
          raise Constraint_Error with "Index is out of range";
       end if;
 
-      return (Element => Container.Elements.EA (Position).all'Access);
+      E := Container.Elements.EA (Index);
+
+      if E = null then
+         raise Constraint_Error with "element at Index is empty";
+      end if;
+
+      return (Element => E.all'Access);
    end Reference;
 
    ---------------------
Index: a-coinve.ads
===================================================================
--- a-coinve.ads	(revision 183051)
+++ a-coinve.ads	(working copy)
@@ -150,19 +150,21 @@ 
    for Reference_Type'Read use Read;
 
    function Constant_Reference
-     (Container : Vector; Position : Cursor)    --  SHOULD BE ALIASED
-   return Constant_Reference_Type;
+     (Container : aliased Vector;
+      Position  : Cursor) return Constant_Reference_Type;
 
+   function Reference
+     (Container : aliased in out Vector;
+      Position  : Cursor) return Reference_Type;
+
    function Constant_Reference
-     (Container : Vector; Position : Index_Type)
-   return Constant_Reference_Type;
+     (Container : aliased Vector;
+      Index     : Index_Type) return Constant_Reference_Type;
 
-   function Reference (Container : Vector; Position : Cursor)
-   return Reference_Type;
+   function Reference
+     (Container : aliased in out Vector;
+      Index     : Index_Type) return Reference_Type;
 
-   function Reference (Container : Vector; Position : Index_Type)
-   return Reference_Type;
-
    function To_Cursor
      (Container : Vector;
       Index     : Extended_Index) return Cursor;
Index: a-ciorse.adb
===================================================================
--- a-ciorse.adb	(revision 183051)
+++ a-ciorse.adb	(working copy)
@@ -372,6 +372,35 @@ 
       return Node.Color;
    end Color;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased Set;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
+
+      if Position.Node.Element = null then
+         raise Program_Error with "Node has no element";
+      end if;
+
+      pragma Assert
+        (Vet (Container.Tree, Position.Node),
+         "bad cursor in Constant_Reference");
+
+      return (Element => Position.Node.Element.all'Access);
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -733,6 +762,29 @@ 
                  else Cursor'(Container'Unrestricted_Access, Node));
       end Ceiling;
 
+      ------------------------
+      -- Constant_Reference --
+      ------------------------
+
+      function Constant_Reference
+        (Container : aliased Set;
+         Key       : Key_Type) return Constant_Reference_Type
+      is
+         Node : constant Node_Access :=
+                  Key_Keys.Find (Container.Tree, Key);
+
+      begin
+         if Node = null then
+            raise Constraint_Error with "Key not in set";
+         end if;
+
+         if Node.Element = null then
+            raise Program_Error with "Node has no element";
+         end if;
+
+         return (Element => Node.Element.all'Access);
+      end Constant_Reference;
+
       --------------
       -- Contains --
       --------------
@@ -889,6 +941,74 @@ 
          Replace_Element (Container.Tree, Node, New_Item);
       end Replace;
 
+      ----------
+      -- Read --
+      ----------
+
+      procedure Read
+        (Stream : not null access Root_Stream_Type'Class;
+         Item   : out Reference_Type)
+      is
+      begin
+         raise Program_Error with "attempt to stream reference";
+      end Read;
+
+      ------------------------------
+      -- Reference_Preserving_Key --
+      ------------------------------
+
+      function Reference_Preserving_Key
+        (Container : aliased in out Set;
+         Position  : Cursor) return Reference_Type
+      is
+      begin
+         if Position.Container = null then
+            raise Constraint_Error with "Position cursor has no element";
+         end if;
+
+         if Position.Container /= Container'Unrestricted_Access then
+            raise Program_Error with
+              "Position cursor designates wrong container";
+         end if;
+
+         if Position.Node.Element = null then
+            raise Program_Error with "Node has no element";
+         end if;
+
+         pragma Assert
+           (Vet (Container.Tree, Position.Node),
+            "bad cursor in function Reference_Preserving_Key");
+
+         --  Some form of finalization will be required in order to actually
+         --  check that the key-part of the element designated by Position has
+         --  not changed.  ???
+
+         return (Element => Position.Node.Element.all'Access);
+      end Reference_Preserving_Key;
+
+      function Reference_Preserving_Key
+        (Container : aliased in out Set;
+         Key       : Key_Type) return Reference_Type
+      is
+         Node : constant Node_Access :=
+                  Key_Keys.Find (Container.Tree, Key);
+
+      begin
+         if Node = null then
+            raise Constraint_Error with "Key not in set";
+         end if;
+
+         if Node.Element = null then
+            raise Program_Error with "Node has no element";
+         end if;
+
+         --  Some form of finalization will be required in order to actually
+         --  check that the key-part of the element designated by Key has not
+         --  changed.  ???
+
+         return (Element => Node.Element.all'Access);
+      end Reference_Preserving_Key;
+
       -----------------------------------
       -- Update_Element_Preserving_Key --
       -----------------------------------
@@ -955,42 +1075,10 @@ 
          raise Program_Error with "key was modified";
       end Update_Element_Preserving_Key;
 
-      function Reference_Preserving_Key
-        (Container : aliased in out Set;
-         Key       : Key_Type) return Constant_Reference_Type
-      is
-         Position : constant Cursor := Find (Container, Key);
+      -----------
+      -- Write --
+      -----------
 
-      begin
-         if Position.Container = null then
-            raise Constraint_Error with "Position cursor has no element";
-         end if;
-
-         return (Element => Position.Node.Element);
-      end Reference_Preserving_Key;
-
-      function Reference_Preserving_Key
-        (Container : aliased in out Set;
-         Key       : Key_Type) return Reference_Type
-      is
-         Position : constant Cursor := Find (Container, Key);
-
-      begin
-         if Position.Container = null then
-            raise Constraint_Error with "Position cursor has no element";
-         end if;
-
-         return (Element => Position.Node.Element);
-      end Reference_Preserving_Key;
-
-      procedure Read
-        (Stream : not null access Root_Stream_Type'Class;
-         Item   : out Reference_Type)
-      is
-      begin
-         raise Program_Error with "attempt to stream reference";
-      end Read;
-
       procedure Write
         (Stream : not null access Root_Stream_Type'Class;
          Item   : Reference_Type)
@@ -1653,22 +1741,6 @@ 
       raise Program_Error with "attempt to stream reference";
    end Read;
 
-   ---------------
-   -- Reference --
-   ---------------
-
-   function Constant_Reference (Container : Set; Position : Cursor)
-   return Constant_Reference_Type
-   is
-      pragma Unreferenced (Container);
-   begin
-      if Position.Container = null then
-         raise Constraint_Error with "Position cursor has no element";
-      end if;
-
-      return (Element => Position.Node.Element.all'Access);
-   end Constant_Reference;
-
    -------------
    -- Replace --
    -------------
Index: a-ciorse.ads
===================================================================
--- a-ciorse.ads	(revision 183051)
+++ a-ciorse.ads	(working copy)
@@ -67,27 +67,6 @@ 
    package Set_Iterator_Interfaces is new
      Ada.Iterator_Interfaces (Cursor, Has_Element);
 
-   type Constant_Reference_Type
-     (Element : not null access constant Element_Type) is
-   private with
-      Implicit_Dereference => Element;
-
-   function Constant_Reference
-     (Container : Set;
-      Position  : Cursor) return Constant_Reference_Type;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Constant_Reference_Type);
-
-   for Constant_Reference_Type'Read use Read;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Constant_Reference_Type);
-
-   for Constant_Reference_Type'Write use Write;
-
    function "=" (Left, Right : Set) return Boolean;
 
    function Equivalent_Sets (Left, Right : Set) return Boolean;
@@ -111,6 +90,27 @@ 
      (Position : Cursor;
       Process  : not null access procedure (Element : Element_Type));
 
+   type Constant_Reference_Type
+     (Element : not null access constant Element_Type) is
+   private with
+      Implicit_Dereference => Element;
+
+   function Constant_Reference
+     (Container : aliased Set;
+      Position  : Cursor) return Constant_Reference_Type;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Constant_Reference_Type);
+
+   for Constant_Reference_Type'Read use Read;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Constant_Reference_Type);
+
+   for Constant_Reference_Type'Write use Write;
+
    procedure Assign (Target : in out Set; Source : Set);
 
    function Copy (Source : Set) return Set;
@@ -292,6 +292,10 @@ 
 
       function Reference_Preserving_Key
         (Container : aliased in out Set;
+         Position  : Cursor) return Reference_Type;
+
+      function Constant_Reference
+        (Container : aliased Set;
          Key       : Key_Type) return Constant_Reference_Type;
 
       function Reference_Preserving_Key
Index: a-coorma.adb
===================================================================
--- a-coorma.adb	(revision 183051)
+++ a-coorma.adb	(working copy)
@@ -323,11 +323,38 @@ 
    ------------------------
 
    function Constant_Reference
+     (Container : aliased Map;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong map";
+      end if;
+
+      pragma Assert (Vet (Container.Tree, Position.Node),
+                     "Position cursor in Constant_Reference is bad");
+
+      return (Element => Position.Node.Element'Access);
+   end Constant_Reference;
+
+   function Constant_Reference
      (Container : Map;
       Key       : Key_Type) return Constant_Reference_Type
    is
+      Node : constant Node_Access := Key_Ops.Find (Container.Tree, Key);
+
    begin
-      return (Element => Container.Element (Key)'Unrestricted_Access);
+      if Node = null then
+         raise Constraint_Error with "key not in map";
+      end if;
+
+      return (Element => Node.Element'Access);
    end Constant_Reference;
 
    --------------
@@ -1250,14 +1277,40 @@ 
    ---------------
 
    function Reference
-     (Container : Map;
-      Key       : Key_Type)
-      return Reference_Type
+     (Container : aliased in out Map;
+      Position  : Cursor) return Reference_Type
    is
    begin
-      return (Element => Container.Element (Key)'Unrestricted_Access);
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong map";
+      end if;
+
+      pragma Assert (Vet (Container.Tree, Position.Node),
+                     "Position cursor in function Reference is bad");
+
+      return (Element => Position.Node.Element'Access);
    end Reference;
 
+   function Reference
+     (Container : aliased in out Map;
+      Key       : Key_Type) return Reference_Type
+   is
+      Node : constant Node_Access := Key_Ops.Find (Container.Tree, Key);
+
+   begin
+      if Node = null then
+         raise Constraint_Error with "key not in map";
+      end if;
+
+      return (Element => Node.Element'Access);
+   end Reference;
+
    -------------
    -- Replace --
    -------------
Index: a-coorma.ads
===================================================================
--- a-coorma.ads	(revision 183051)
+++ a-coorma.ads	(working copy)
@@ -51,7 +51,7 @@ 
    function Equivalent_Keys (Left, Right : Key_Type) return Boolean;
 
    type Map is tagged private with
-      constant_Indexing => Constant_Reference,
+      Constant_Indexing => Constant_Reference,
       Variable_Indexing => Reference,
       Default_Iterator  => Iterate,
       Iterator_Element  => Element_Type;
@@ -96,6 +96,31 @@ 
       Process   : not null access
                    procedure (Key : Key_Type; Element : in out Element_Type));
 
+   type Constant_Reference_Type
+      (Element : not null access constant Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   type Reference_Type (Element : not null access Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Position  : Cursor) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out Map;
+      Position  : Cursor) return Reference_Type;
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Key       : Key_Type) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out Map;
+      Key       : Key_Type) return Reference_Type;
+
    procedure Assign (Target : in out Map; Source : Map);
 
    function Copy (Source : Map) return Map;
@@ -182,23 +207,6 @@ 
 
    function ">" (Left : Key_Type; Right : Cursor) return Boolean;
 
-   type Constant_Reference_Type
-      (Element : not null access constant Element_Type) is private
-   with
-      Implicit_Dereference => Element;
-
-   type Reference_Type (Element : not null access Element_Type) is private
-   with
-      Implicit_Dereference => Element;
-
-   function Constant_Reference
-     (Container : Map;
-      Key       : Key_Type)    --  SHOULD BE ALIASED???
-      return Constant_Reference_Type;
-
-   function Reference (Container : Map; Key : Key_Type)
-   return Reference_Type;
-
    procedure Iterate
      (Container : Map;
       Process   : not null access procedure (Position : Cursor));
@@ -234,7 +242,7 @@ 
       Right   : Node_Access;
       Color   : Red_Black_Trees.Color_Type := Red_Black_Trees.Red;
       Key     : Key_Type;
-      Element : Element_Type;
+      Element : aliased Element_Type;
    end record;
 
    package Tree_Types is
Index: a-cborma.adb
===================================================================
--- a-cborma.adb	(revision 183051)
+++ a-cborma.adb	(working copy)
@@ -402,6 +402,53 @@ 
       return Node.Color;
    end Color;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong map";
+      end if;
+
+      pragma Assert (Vet (Container, Position.Node),
+                     "Position cursor in Constant_Reference is bad");
+
+      declare
+         N : Node_Type renames Container.Nodes (Position.Node);
+      begin
+         return (Element => N.Element'Access);
+      end;
+   end Constant_Reference;
+
+   function Constant_Reference
+     (Container : Map;
+      Key       : Key_Type) return Constant_Reference_Type
+   is
+      Node : constant Count_Type := Key_Ops.Find (Container, Key);
+
+   begin
+      if Node = 0 then
+         raise Constraint_Error with "key not in map";
+      end if;
+
+      declare
+         N : Node_Type renames Container.Nodes (Node);
+      begin
+         return (Element => N.Element'Access);
+      end;
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -1318,20 +1365,47 @@ 
    -- Reference --
    ---------------
 
-   function Constant_Reference
-     (Container : Map;
-      Key       : Key_Type) return Constant_Reference_Type
+   function Reference
+     (Container : aliased in out Map;
+      Position  : Cursor) return Reference_Type
    is
    begin
-      return (Element => Container.Element (Key)'Unrestricted_Access);
-   end Constant_Reference;
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
 
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong map";
+      end if;
+
+      pragma Assert (Vet (Container, Position.Node),
+                     "Position cursor in function Reference is bad");
+
+      declare
+         N : Node_Type renames Container.Nodes (Position.Node);
+      begin
+         return (Element => N.Element'Access);
+      end;
+   end Reference;
+
    function Reference
-     (Container : Map;
+     (Container : aliased in out Map;
       Key       : Key_Type) return Reference_Type
    is
+      Node : constant Count_Type := Key_Ops.Find (Container, Key);
+
    begin
-      return (Element => Container.Element (Key)'Unrestricted_Access);
+      if Node = 0 then
+         raise Constraint_Error with "key not in map";
+      end if;
+
+      declare
+         N : Node_Type renames Container.Nodes (Node);
+      begin
+         return (Element => N.Element'Access);
+      end;
    end Reference;
 
    -------------
Index: a-cborma.ads
===================================================================
--- a-cborma.ads	(revision 183051)
+++ a-cborma.ads	(working copy)
@@ -50,7 +50,7 @@ 
    function Equivalent_Keys (Left, Right : Key_Type) return Boolean;
 
    type Map (Capacity : Count_Type) is tagged private with
-      constant_Indexing => Constant_Reference,
+      Constant_Indexing => Constant_Reference,
       Variable_Indexing => Reference,
       Default_Iterator  => Iterate,
       Iterator_Element  => Element_Type;
@@ -97,6 +97,55 @@ 
       Process   : not null access
                     procedure (Key : Key_Type; Element : in out Element_Type));
 
+   type Constant_Reference_Type
+      (Element : not null access constant Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Constant_Reference_Type);
+
+   for Constant_Reference_Type'Read use Read;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Constant_Reference_Type);
+
+   for Constant_Reference_Type'Write use Write;
+
+   type Reference_Type (Element : not null access Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Reference_Type);
+
+   for Reference_Type'Read use Read;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Reference_Type);
+
+   for Reference_Type'Write use Write;
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Position  : Cursor) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out Map;
+      Position  : Cursor) return Reference_Type;
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Key       : Key_Type) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out Map;
+      Key       : Key_Type) return Reference_Type;
+
    procedure Assign (Target : in out Map; Source : Map);
 
    function Copy (Source : Map; Capacity : Count_Type := 0) return Map;
@@ -183,46 +232,6 @@ 
 
    function ">" (Left : Key_Type; Right : Cursor) return Boolean;
 
-   type Constant_Reference_Type
-      (Element : not null access constant Element_Type) is private
-   with
-      Implicit_Dereference => Element;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Constant_Reference_Type);
-
-   for Constant_Reference_Type'Read use Read;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Constant_Reference_Type);
-
-   for Constant_Reference_Type'Write use Write;
-
-   type Reference_Type (Element : not null access Element_Type) is private
-   with
-      Implicit_Dereference => Element;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Reference_Type);
-
-   for Reference_Type'Read use Read;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Reference_Type);
-
-   for Reference_Type'Write use Write;
-
-   function Constant_Reference
-     (Container : Map;
-      Key       : Key_Type)    --  SHOULD BE ALIASED ???
-      return Constant_Reference_Type;
-
-   function Reference (Container : Map; Key : Key_Type) return Reference_Type;
-
    procedure Iterate
      (Container : Map;
       Process   : not null access procedure (Position : Cursor));
@@ -251,7 +260,7 @@ 
       Right   : Count_Type;
       Color   : Red_Black_Trees.Color_Type := Red_Black_Trees.Red;
       Key     : Key_Type;
-      Element : Element_Type;
+      Element : aliased Element_Type;
    end record;
 
    package Tree_Types is
Index: a-cidlli.adb
===================================================================
--- a-cidlli.adb	(revision 183051)
+++ a-cidlli.adb	(working copy)
@@ -242,6 +242,33 @@ 
       Free (X);
    end Clear;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased List;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
+
+      if Position.Node.Element = null then
+         raise Program_Error with "Node has no element";
+      end if;
+
+      pragma Assert (Vet (Position), "bad cursor in Constant_Reference");
+
+      return (Element => Position.Node.Element.all'Access);
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -1303,27 +1330,26 @@ 
    -- Reference --
    ---------------
 
-   function Constant_Reference (Container : List; Position : Cursor)
-   return Constant_Reference_Type is
+   function Reference
+     (Container : aliased in out List;
+      Position  : Cursor) return Reference_Type
+   is
    begin
-      pragma Unreferenced (Container);
-
       if Position.Container = null then
          raise Constraint_Error with "Position cursor has no element";
       end if;
 
-      return (Element => Position.Node.Element.all'Access);
-   end Constant_Reference;
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
 
-   function Reference (Container : List; Position : Cursor)
-   return Reference_Type is
-   begin
-      pragma Unreferenced (Container);
-
-      if Position.Container = null then
-         raise Constraint_Error with "Position cursor has no element";
+      if Position.Node.Element = null then
+         raise Program_Error with "Node has no element";
       end if;
 
+      pragma Assert (Vet (Position), "bad cursor in function Reference");
+
       return (Element => Position.Node.Element.all'Access);
    end Reference;
 
Index: a-cidlli.ads
===================================================================
--- a-cidlli.ads	(revision 183051)
+++ a-cidlli.ads	(working copy)
@@ -90,6 +90,48 @@ 
       Position  : Cursor;
       Process   : not null access procedure (Element : in out Element_Type));
 
+   type Constant_Reference_Type
+      (Element : not null access constant Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Constant_Reference_Type);
+
+   for Constant_Reference_Type'Write use Write;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Constant_Reference_Type);
+
+   for Constant_Reference_Type'Read use Read;
+
+   type Reference_Type
+     (Element : not null access Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Reference_Type);
+
+   for Reference_Type'Write use Write;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Reference_Type);
+
+   for Reference_Type'Read use Read;
+
+   function Constant_Reference
+     (Container : aliased List;
+      Position  : Cursor) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out List;
+      Position  : Cursor) return Reference_Type;
+
    procedure Assign (Target : in out List; Source : List);
 
    function Copy (Source : List) return List;
@@ -203,50 +245,6 @@ 
       Start     : Cursor)
       return List_Iterator_Interfaces.Reversible_Iterator'class;
 
-   type Constant_Reference_Type
-      (Element : not null access constant Element_Type) is private
-   with
-      Implicit_Dereference => Element;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Constant_Reference_Type);
-
-   for Constant_Reference_Type'Write use Write;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Constant_Reference_Type);
-
-   for Constant_Reference_Type'Read use Read;
-
-   type Reference_Type (Element : not null access Element_Type) is
-   private
-   with
-      Implicit_Dereference => Element;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Reference_Type);
-
-   for Reference_Type'Write use Write;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Reference_Type);
-
-   for Reference_Type'Read use Read;
-
-   function Constant_Reference
-     (Container : List;
-      Position  : Cursor)    --  SHOULD BE ALIASED ???
-      return Constant_Reference_Type;
-
-   function Reference
-     (Container : List;
-      Position  : Cursor)    --  SHOULD BE ALIASED ???
-      return Reference_Type;
-
    generic
       with function "<" (Left, Right : Element_Type) return Boolean is <>;
    package Generic_Sorting is
Index: a-cimutr.adb
===================================================================
--- a-cimutr.adb	(revision 183051)
+++ a-cimutr.adb	(working copy)
@@ -441,6 +441,40 @@ 
       pragma Assert (Children_Count = Container_Count);
    end Clear;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased Tree;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
+
+      if Position.Node = Root_Node (Container) then
+         raise Program_Error with "Position cursor designates root";
+      end if;
+
+      if Position.Node.Element = null then
+         raise Program_Error with "Node has no element";
+      end if;
+
+      --  Implement Vet for multiway tree???
+      --  pragma Assert (Vet (Position),
+      --                 "Position cursor in Constant_Reference is bad");
+
+      return (Element => Position.Node.Element.all'Access);
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -1980,24 +2014,34 @@ 
    -- Reference --
    ---------------
 
-   function Constant_Reference
-     (Container : aliased Tree;
-      Position  : Cursor) return Constant_Reference_Type
-   is
-   begin
-      pragma Unreferenced (Container);
-
-      return (Element => Position.Node.Element.all'Unchecked_Access);
-   end Constant_Reference;
-
    function Reference
-     (Container : aliased Tree;
+     (Container : aliased in out Tree;
       Position  : Cursor) return Reference_Type
    is
    begin
-      pragma Unreferenced (Container);
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
 
-      return (Element => Position.Node.Element.all'Unchecked_Access);
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
+
+      if Position.Node = Root_Node (Container) then
+         raise Program_Error with "Position cursor designates root";
+      end if;
+
+      if Position.Node.Element = null then
+         raise Program_Error with "Node has no element";
+      end if;
+
+      --  Implement Vet for multiway tree???
+      --  pragma Assert (Vet (Position),
+      --                 "Position cursor in Constant_Reference is bad");
+
+      return (Element => Position.Node.Element.all'Access);
    end Reference;
 
    --------------------
Index: a-cimutr.ads
===================================================================
--- a-cimutr.ads	(revision 183051)
+++ a-cimutr.ads	(working copy)
@@ -109,6 +109,14 @@ 
      (Element : not null access Element_Type) is private
         with Implicit_Dereference => Element;
 
+   function Constant_Reference
+     (Container : aliased Tree;
+      Position  : Cursor) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out Tree;
+      Position  : Cursor) return Reference_Type;
+
    procedure Assign (Target : in out Tree; Source : Tree);
 
    function Copy (Source : Tree) return Tree;
@@ -400,14 +408,6 @@ 
 
    for Reference_Type'Write use Write;
 
-   function Constant_Reference
-     (Container : aliased Tree;
-      Position  : Cursor) return Constant_Reference_Type;
-
-   function Reference
-     (Container : aliased Tree;
-      Position  : Cursor) return Reference_Type;
-
    Empty_Tree : constant Tree := (Controlled with others => <>);
 
    No_Element : constant Cursor := (others => <>);
Index: a-cihase.adb
===================================================================
--- a-cihase.adb	(revision 183051)
+++ a-cihase.adb	(working copy)
@@ -204,6 +204,33 @@ 
       HT_Ops.Clear (Container.HT);
    end Clear;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased Set;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
+
+      if Position.Node.Element = null then
+         raise Program_Error with "Node has no element";
+      end if;
+
+      pragma Assert (Vet (Position), "bad cursor in Constant_Reference");
+
+      return (Element => Position.Node.Element.all'Access);
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -1220,19 +1247,6 @@ 
          raise;
    end Read_Node;
 
-   ---------------
-   -- Reference --
-   ---------------
-
-   function Constant_Reference
-     (Container : aliased Set;
-      Position  : Cursor) return Constant_Reference_Type
-   is
-      pragma Unreferenced (Container);
-   begin
-      return (Element => Position.Node.Element.all'Access);
-   end Constant_Reference;
-
    -------------
    -- Replace --
    -------------
@@ -1892,6 +1906,29 @@ 
            Hash      => Hash,
            Equivalent_Keys => Equivalent_Key_Node);
 
+      ------------------------
+      -- Constant_Reference --
+      ------------------------
+
+      function Constant_Reference
+        (Container : aliased Set;
+         Key       : Key_Type) return Constant_Reference_Type
+      is
+         Node : constant Node_Access :=
+                  Key_Keys.Find (Container.HT, Key);
+
+      begin
+         if Node = null then
+            raise Constraint_Error with "Key not in set";
+         end if;
+
+         if Node.Element = null then
+            raise Program_Error with "Node has no element";
+         end if;
+
+         return (Element => Node.Element.all'Access);
+      end Constant_Reference;
+
       --------------
       -- Contains --
       --------------
@@ -2001,6 +2038,74 @@ 
          return Key (Position.Node.Element.all);
       end Key;
 
+      ----------
+      -- Read --
+      ----------
+
+      procedure Read
+        (Stream : not null access Root_Stream_Type'Class;
+         Item   : out Reference_Type)
+      is
+      begin
+         raise Program_Error with "attempt to stream reference";
+      end Read;
+
+      ------------------------------
+      -- Reference_Preserving_Key --
+      ------------------------------
+
+      function Reference_Preserving_Key
+        (Container : aliased in out Set;
+         Position  : Cursor) return Reference_Type
+      is
+      begin
+         if Position.Container = null then
+            raise Constraint_Error with "Position cursor has no element";
+         end if;
+
+         if Position.Container /= Container'Unrestricted_Access then
+            raise Program_Error with
+              "Position cursor designates wrong container";
+         end if;
+
+         if Position.Node.Element = null then
+            raise Program_Error with "Node has no element";
+         end if;
+
+         pragma Assert
+           (Vet (Position),
+            "bad cursor in function Reference_Preserving_Key");
+
+         --  Some form of finalization will be required in order to actually
+         --  check that the key-part of the element designated by Position has
+         --  not changed.  ???
+
+         return (Element => Position.Node.Element.all'Access);
+      end Reference_Preserving_Key;
+
+      function Reference_Preserving_Key
+        (Container : aliased in out Set;
+         Key       : Key_Type) return Reference_Type
+      is
+         Node : constant Node_Access :=
+                  Key_Keys.Find (Container.HT, Key);
+
+      begin
+         if Node = null then
+            raise Constraint_Error with "Key not in set";
+         end if;
+
+         if Node.Element = null then
+            raise Program_Error with "Node has no element";
+         end if;
+
+         --  Some form of finalization will be required in order to actually
+         --  check that the key-part of the element designated by Key has not
+         --  changed.  ???
+
+         return (Element => Node.Element.all'Access);
+      end Reference_Preserving_Key;
+
       -------------
       -- Replace --
       -------------
@@ -2022,6 +2127,10 @@ 
          Replace_Element (Container.HT, Node, New_Item);
       end Replace;
 
+      -----------------------------------
+      -- Update_Element_Preserving_Key --
+      -----------------------------------
+
       procedure Update_Element_Preserving_Key
         (Container : in out Set;
          Position  : Cursor;
@@ -2123,28 +2232,18 @@ 
          raise Program_Error with "key was modified";
       end Update_Element_Preserving_Key;
 
-      ------------------------------
-      -- Reference_Preserving_Key --
-      ------------------------------
+      -----------
+      -- Write --
+      -----------
 
-      function Reference_Preserving_Key
-        (Container : aliased in out Set;
-         Position  : Cursor) return Reference_Type
+      procedure Write
+        (Stream : not null access Root_Stream_Type'Class;
+         Item   : Reference_Type)
       is
-         pragma Unreferenced (Container);
       begin
-         return (Element => Position.Node.Element.all'Access);
-      end Reference_Preserving_Key;
+         raise Program_Error with "attempt to stream reference";
+      end Write;
 
-      function Reference_Preserving_Key
-        (Container : aliased in out Set;
-         Key       : Key_Type) return Reference_Type
-      is
-         Position : constant Cursor := Find (Container, Key);
-      begin
-         return (Element => Position.Node.Element.all'Access);
-      end Reference_Preserving_Key;
-
    end Generic_Keys;
 
 end Ada.Containers.Indefinite_Hashed_Sets;
Index: a-cihase.ads
===================================================================
--- a-cihase.ads	(revision 183051)
+++ a-cihase.ads	(working copy)
@@ -150,8 +150,7 @@ 
 
    function Constant_Reference
      (Container : aliased Set;
-      Position  : Cursor)
-   return Constant_Reference_Type;
+      Position  : Cursor) return Constant_Reference_Type;
 
    procedure Assign (Target : in out Set; Source : Set);
 
@@ -420,6 +419,10 @@ 
         (Container : aliased in out Set;
          Position  : Cursor) return Reference_Type;
 
+      function Constant_Reference
+        (Container : aliased Set;
+         Key       : Key_Type) return Constant_Reference_Type;
+
       function Reference_Preserving_Key
         (Container : aliased in out Set;
          Key       : Key_Type) return Reference_Type;
@@ -427,6 +430,20 @@ 
    private
       type Reference_Type (Element : not null access Element_Type)
          is null record;
+
+      use Ada.Streams;
+
+      procedure Read
+        (Stream : not null access Root_Stream_Type'Class;
+         Item   : out Reference_Type);
+
+      for Reference_Type'Read use Read;
+
+      procedure Write
+        (Stream : not null access Root_Stream_Type'Class;
+         Item   : Reference_Type);
+
+      for Reference_Type'Write use Write;
    end Generic_Keys;
 
 private
Index: a-cohama.adb
===================================================================
--- a-cohama.adb	(revision 183051)
+++ a-cohama.adb	(working copy)
@@ -188,6 +188,46 @@ 
       HT_Ops.Clear (Container.HT);
    end Clear;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong map";
+      end if;
+
+      pragma Assert
+        (Vet (Position),
+         "Position cursor in Constant_Reference is bad");
+
+      return (Element => Position.Node.Element'Access);
+   end Constant_Reference;
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Key       : Key_Type) return Constant_Reference_Type
+   is
+      Node : constant Node_Access := Key_Ops.Find (Container.HT, Key);
+
+   begin
+      if Node = null then
+         raise Constraint_Error with "key not in map";
+      end if;
+
+      return (Element => Node.Element'Access);
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -861,38 +901,40 @@ 
    -- Reference --
    ---------------
 
-   function Constant_Reference
-     (Container : aliased Map;
-      Position  : Cursor) return Constant_Reference_Type
-   is
-      pragma Unreferenced (Container);
-   begin
-      return (Element => Element (Position)'Unrestricted_Access);
-   end Constant_Reference;
-
    function Reference
      (Container : aliased in out Map;
       Position  : Cursor) return Reference_Type
    is
-      pragma Unreferenced (Container);
    begin
-      return (Element => Element (Position)'Unrestricted_Access);
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong map";
+      end if;
+
+      pragma Assert
+        (Vet (Position),
+         "Position cursor in function Reference is bad");
+
+      return (Element => Position.Node.Element'Access);
    end Reference;
 
-   function Constant_Reference
-     (Container : aliased Map;
-      Key       : Key_Type) return Constant_Reference_Type
-   is
-   begin
-      return (Element => Container.Element (Key)'Unrestricted_Access);
-   end Constant_Reference;
-
    function Reference
      (Container : aliased in out Map;
       Key       : Key_Type) return Reference_Type
    is
+      Node : constant Node_Access := Key_Ops.Find (Container.HT, Key);
+
    begin
-      return (Element => Container.Element (Key)'Unrestricted_Access);
+      if Node = null then
+         raise Constraint_Error with "key not in map";
+      end if;
+
+      return (Element => Node.Element'Access);
    end Reference;
 
    ---------------
Index: a-cohama.ads
===================================================================
--- a-cohama.ads	(revision 183051)
+++ a-cohama.ads	(working copy)
@@ -148,6 +148,55 @@ 
    --  Calls Process with the key (with only a constant view) and element (with
    --  a variable view) of the node designed by the cursor.
 
+   type Constant_Reference_Type
+      (Element : not null access constant Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Constant_Reference_Type);
+
+   for Constant_Reference_Type'Write use Write;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Constant_Reference_Type);
+
+   for Constant_Reference_Type'Read use Read;
+
+   type Reference_Type (Element : not null access Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Reference_Type);
+
+   for Reference_Type'Write use Write;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Reference_Type);
+
+   for Reference_Type'Read use Read;
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Position  : Cursor) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out Map;
+      Position  : Cursor) return Reference_Type;
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Key       : Key_Type) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out Map;
+      Key       : Key_Type) return Reference_Type;
+
    procedure Assign (Target : in out Map; Source : Map);
 
    function Copy (Source : Map; Capacity : Count_Type := 0) return Map;
@@ -277,55 +326,6 @@ 
    --  Returns the result of calling Equivalent_Keys with key Left and the node
    --  designated by Right.
 
-   type Constant_Reference_Type
-      (Element : not null access constant Element_Type) is private
-   with
-      Implicit_Dereference => Element;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Constant_Reference_Type);
-
-   for Constant_Reference_Type'Write use Write;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Constant_Reference_Type);
-
-   for Constant_Reference_Type'Read use Read;
-
-   type Reference_Type (Element : not null access Element_Type) is private
-   with
-      Implicit_Dereference => Element;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Reference_Type);
-
-   for Reference_Type'Write use Write;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Reference_Type);
-
-   for Reference_Type'Read use Read;
-
-   function Constant_Reference
-     (Container : aliased Map;
-      Position  : Cursor) return Constant_Reference_Type;
-
-   function Reference
-     (Container : aliased in out Map;
-      Position  : Cursor) return Reference_Type;
-
-   function Constant_Reference
-     (Container : aliased Map;
-      Key       : Key_Type) return Constant_Reference_Type;
-
-   function Reference
-     (Container : aliased in out Map;
-      Key       : Key_Type) return Reference_Type;
-
    procedure Iterate
      (Container : Map;
       Process   : not null access procedure (Position : Cursor));
@@ -354,7 +354,7 @@ 
 
    type Node_Type is limited record
       Key     : Key_Type;
-      Element : Element_Type;
+      Element : aliased Element_Type;
       Next    : Node_Access;
    end record;
 
Index: a-coorse.adb
===================================================================
--- a-coorse.adb	(revision 183051)
+++ a-coorse.adb	(working copy)
@@ -331,6 +331,31 @@ 
       return Node.Color;
    end Color;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased Set;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
+
+      pragma Assert
+        (Vet (Container.Tree, Position.Node),
+         "bad cursor in Constant_Reference");
+
+      return (Element => Position.Node.Element'Access);
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -658,6 +683,25 @@ 
                  else Cursor'(Container'Unrestricted_Access, Node));
       end Ceiling;
 
+      ------------------------
+      -- Constant_Reference --
+      ------------------------
+
+      function Constant_Reference
+        (Container : aliased Set;
+         Key       : Key_Type) return Constant_Reference_Type
+      is
+         Node : constant Node_Access :=
+                  Key_Keys.Find (Container.Tree, Key);
+
+      begin
+         if Node = null then
+            raise Constraint_Error with "key not in set";
+         end if;
+
+         return (Element => Node.Element'Access);
+      end Constant_Reference;
+
       --------------
       -- Contains --
       --------------
@@ -784,6 +828,66 @@ 
          return Key (Position.Node.Element);
       end Key;
 
+      ----------
+      -- Read --
+      ----------
+
+      procedure Read
+        (Stream : not null access Root_Stream_Type'Class;
+         Item   : out Reference_Type)
+      is
+      begin
+         raise Program_Error with "attempt to stream reference";
+      end Read;
+
+      ------------------------------
+      -- Reference_Preserving_Key --
+      ------------------------------
+
+      function Reference_Preserving_Key
+        (Container : aliased in out Set;
+         Position  : Cursor) return Reference_Type
+      is
+      begin
+         if Position.Container = null then
+            raise Constraint_Error with "Position cursor has no element";
+         end if;
+
+         if Position.Container /= Container'Unrestricted_Access then
+            raise Program_Error with
+              "Position cursor designates wrong container";
+         end if;
+
+         pragma Assert
+           (Vet (Container.Tree, Position.Node),
+            "bad cursor in function Reference_Preserving_Key");
+
+         --  Some form of finalization will be required in order to actually
+         --  check that the key-part of the element designated by Position has
+         --  not changed.  ???
+
+         return (Element => Position.Node.Element'Access);
+      end Reference_Preserving_Key;
+
+      function Reference_Preserving_Key
+        (Container : aliased in out Set;
+         Key       : Key_Type) return Reference_Type
+      is
+         Node : constant Node_Access :=
+                  Key_Keys.Find (Container.Tree, Key);
+
+      begin
+         if Node = null then
+            raise Constraint_Error with "key not in set";
+         end if;
+
+         --  Some form of finalization will be required in order to actually
+         --  check that the key-part of the element designated by Position has
+         --  not changed.  ???
+
+         return (Element => Node.Element'Access);
+      end Reference_Preserving_Key;
+
       -------------
       -- Replace --
       -------------
@@ -867,42 +971,10 @@ 
          raise Program_Error with "key was modified";
       end Update_Element_Preserving_Key;
 
-      function Reference_Preserving_Key
-        (Container : aliased in out Set;
-         Key       : Key_Type) return Constant_Reference_Type
-      is
-         Position : constant Cursor := Find (Container, Key);
+      -----------
+      -- Write --
+      -----------
 
-      begin
-         if Position.Container = null then
-            raise Constraint_Error with "Position cursor has no element";
-         end if;
-
-         return (Element => Position.Node.Element'Access);
-      end Reference_Preserving_Key;
-
-      function Reference_Preserving_Key
-        (Container : aliased in out Set;
-         Key       : Key_Type) return Reference_Type
-      is
-         Position : constant Cursor := Find (Container, Key);
-
-      begin
-         if Position.Container = null then
-            raise Constraint_Error with "Position cursor has no element";
-         end if;
-
-         return (Element => Position.Node.Element'Access);
-      end Reference_Preserving_Key;
-
-      procedure Read
-        (Stream : not null access Root_Stream_Type'Class;
-         Item   : out Reference_Type)
-      is
-      begin
-         raise Program_Error with "attempt to stream reference";
-      end Read;
-
       procedure Write
         (Stream : not null access Root_Stream_Type'Class;
          Item   : Reference_Type)
@@ -1536,22 +1608,6 @@ 
       raise Program_Error with "attempt to stream reference";
    end Read;
 
-   ---------------
-   -- Reference --
-   ---------------
-
-   function Constant_Reference (Container : Set; Position : Cursor)
-   return Constant_Reference_Type
-   is
-      pragma Unreferenced (Container);
-   begin
-      if Position.Container = null then
-         raise Constraint_Error with "Position cursor has no element";
-      end if;
-
-      return (Element => Position.Node.Element'Access);
-   end Constant_Reference;
-
    -------------
    -- Replace --
    -------------
Index: a-coorse.ads
===================================================================
--- a-coorse.ads	(revision 183051)
+++ a-coorse.ads	(working copy)
@@ -68,28 +68,6 @@ 
    package Set_Iterator_Interfaces is new
      Ada.Iterator_Interfaces (Cursor, Has_Element);
 
-   type Constant_Reference_Type
-      (Element : not null access constant Element_Type) is
-   private
-   with
-      Implicit_Dereference => Element;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Constant_Reference_Type);
-
-   for Constant_Reference_Type'Write use Write;
-
-   function Constant_Reference
-     (Container : Set; Position : Cursor)
-   return Constant_Reference_Type;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Constant_Reference_Type);
-
-   for Constant_Reference_Type'Read use Read;
-
    function "=" (Left, Right : Set) return Boolean;
 
    function Equivalent_Sets (Left, Right : Set) return Boolean;
@@ -113,6 +91,28 @@ 
      (Position : Cursor;
       Process  : not null access procedure (Element : Element_Type));
 
+   type Constant_Reference_Type
+      (Element : not null access constant Element_Type) is
+   private
+   with
+      Implicit_Dereference => Element;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Constant_Reference_Type);
+
+   for Constant_Reference_Type'Write use Write;
+
+   function Constant_Reference
+     (Container : aliased Set;
+      Position  : Cursor) return Constant_Reference_Type;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Constant_Reference_Type);
+
+   for Constant_Reference_Type'Read use Read;
+
    procedure Assign (Target : in out Set; Source : Set);
 
    function Copy (Source : Set) return Set;
@@ -278,6 +278,10 @@ 
 
       function Reference_Preserving_Key
         (Container : aliased in out Set;
+         Position  : Cursor) return Reference_Type;
+
+      function Constant_Reference
+        (Container : aliased Set;
          Key       : Key_Type) return Constant_Reference_Type;
 
       function Reference_Preserving_Key
Index: a-cbhama.adb
===================================================================
--- a-cbhama.adb	(revision 183051)
+++ a-cbhama.adb	(working copy)
@@ -190,6 +190,53 @@ 
       HT_Ops.Clear (Container);
    end Clear;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong map";
+      end if;
+
+      pragma Assert (Vet (Position),
+                     "Position cursor in Constant_Reference is bad");
+
+      declare
+         N : Node_Type renames Container.Nodes (Position.Node);
+      begin
+         return (Element => N.Element'Access);
+      end;
+   end Constant_Reference;
+
+   function Constant_Reference
+     (Container : Map;
+      Key       : Key_Type) return Constant_Reference_Type
+   is
+      Node : constant Count_Type := Key_Ops.Find (Container, Key);
+
+   begin
+      if Node = 0 then
+         raise Constraint_Error with "key not in map";
+      end if;
+
+      declare
+         N : Node_Type renames Container.Nodes (Node);
+      begin
+         return (Element => N.Element'Access);
+      end;
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -916,16 +963,47 @@ 
    -- Reference --
    ---------------
 
-   function Constant_Reference (Container : Map; Key : Key_Type)
-   return Constant_Reference_Type is
+   function Reference
+     (Container : aliased in out Map;
+      Position  : Cursor) return Reference_Type
+   is
    begin
-      return (Element => Container.Element (Key)'Unrestricted_Access);
-   end Constant_Reference;
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
 
-   function Reference (Container : Map; Key : Key_Type)
-   return Reference_Type is
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong map";
+      end if;
+
+      pragma Assert (Vet (Position),
+                     "Position cursor in function Reference is bad");
+
+      declare
+         N : Node_Type renames Container.Nodes (Position.Node);
+      begin
+         return (Element => N.Element'Access);
+      end;
+   end Reference;
+
+   function Reference
+     (Container : aliased in out Map;
+      Key       : Key_Type) return Reference_Type
+   is
+      Node : constant Count_Type := Key_Ops.Find (Container, Key);
+
    begin
-      return (Element => Container.Element (Key)'Unrestricted_Access);
+      if Node = 0 then
+         raise Constraint_Error with "key not in map";
+      end if;
+
+      declare
+         N : Node_Type renames Container.Nodes (Node);
+      begin
+         return (Element => N.Element'Access);
+      end;
    end Reference;
 
    -------------
Index: a-cbhama.ads
===================================================================
--- a-cbhama.ads	(revision 183051)
+++ a-cbhama.ads	(working copy)
@@ -134,6 +134,56 @@ 
    --  Calls Process with the key (with only a constant view) and element (with
    --  a variable view) of the node designed by the cursor.
 
+   type Constant_Reference_Type
+      (Element : not null access constant Element_Type) is
+   private
+   with
+      Implicit_Dereference => Element;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Constant_Reference_Type);
+
+   for Constant_Reference_Type'Write use Write;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Constant_Reference_Type);
+
+   for Constant_Reference_Type'Read use Read;
+
+   type Reference_Type (Element : not null access Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Reference_Type);
+
+   for Reference_Type'Write use Write;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Reference_Type);
+
+   for Reference_Type'Read use Read;
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Position  : Cursor) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out Map;
+      Position  : Cursor) return Reference_Type;
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Key       : Key_Type) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out Map;
+      Key       : Key_Type) return Reference_Type;
+
    procedure Assign (Target : in out Map; Source : Map);
    --  If Target denotes the same object as Source, then the operation has no
    --  effect. If the Target capacity is less then the Source length, then
@@ -286,47 +336,6 @@ 
    function Iterate (Container : Map)
       return Map_Iterator_Interfaces.Forward_Iterator'class;
 
-   type Constant_Reference_Type
-      (Element : not null access constant Element_Type) is
-   private
-   with
-      Implicit_Dereference => Element;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Constant_Reference_Type);
-
-   for Constant_Reference_Type'Write use Write;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Constant_Reference_Type);
-
-   for Constant_Reference_Type'Read use Read;
-
-   type Reference_Type (Element : not null access Element_Type) is private
-   with
-      Implicit_Dereference => Element;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Reference_Type);
-
-   for Reference_Type'Write use Write;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Reference_Type);
-
-   for Reference_Type'Read use Read;
-
-   function Constant_Reference
-     (Container : Map;
-      Key       : Key_Type)    --  SHOULD BE ALIASED???
-      return Constant_Reference_Type;
-
-   function Reference (Container : Map; Key : Key_Type) return Reference_Type;
-
 private
    pragma Inline (Length);
    pragma Inline (Is_Empty);
@@ -342,7 +351,7 @@ 
 
    type Node_Type is record
       Key     : Key_Type;
-      Element : Element_Type;
+      Element : aliased Element_Type;
       Next    : Count_Type;
    end record;
 
Index: a-cborse.adb
===================================================================
--- a-cborse.adb	(revision 183051)
+++ a-cborse.adb	(working copy)
@@ -402,6 +402,35 @@ 
       return Node.Color;
    end Color;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased Set;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
+
+      pragma Assert
+        (Vet (Container, Position.Node),
+         "bad cursor in Constant_Reference");
+
+      declare
+         N : Node_Type renames Container.Nodes (Position.Node);
+      begin
+         return (Element => N.Element'Access);
+      end;
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -697,6 +726,28 @@ 
                  else Cursor'(Container'Unrestricted_Access, Node));
       end Ceiling;
 
+      ------------------------
+      -- Constant_Reference --
+      ------------------------
+
+      function Constant_Reference
+        (Container : aliased Set;
+         Key       : Key_Type) return Constant_Reference_Type
+      is
+         Node : constant Count_Type := Key_Keys.Find (Container, Key);
+
+      begin
+         if Node = 0 then
+            raise Constraint_Error with "key not in set";
+         end if;
+
+         declare
+            N : Node_Type renames Container.Nodes (Node);
+         begin
+            return (Element => N.Element'Access);
+         end;
+      end Constant_Reference;
+
       --------------
       -- Contains --
       --------------
@@ -822,6 +873,69 @@ 
          return Key (Position.Container.Nodes (Position.Node).Element);
       end Key;
 
+      ----------
+      -- Read --
+      ----------
+
+      procedure  Read
+        (Stream : not null access Root_Stream_Type'Class;
+         Item   : out Reference_Type)
+      is
+      begin
+         raise Program_Error with "attempt to stream reference";
+      end Read;
+
+      ------------------------------
+      -- Reference_Preserving_Key --
+      ------------------------------
+
+      function Reference_Preserving_Key
+        (Container : aliased in out Set;
+         Position  : Cursor) return Reference_Type
+      is
+      begin
+         if Position.Container = null then
+            raise Constraint_Error with "Position cursor has no element";
+         end if;
+
+         if Position.Container /= Container'Unrestricted_Access then
+            raise Program_Error with
+              "Position cursor designates wrong container";
+         end if;
+
+         pragma Assert
+           (Vet (Container, Position.Node),
+            "bad cursor in function Reference_Preserving_Key");
+
+         --  Some form of finalization will be required in order to actually
+         --  check that the key-part of the element designated by Position has
+         --  not changed.  ???
+
+         declare
+            N : Node_Type renames Container.Nodes (Position.Node);
+         begin
+            return (Element => N.Element'Access);
+         end;
+      end Reference_Preserving_Key;
+
+      function Reference_Preserving_Key
+        (Container : aliased in out Set;
+         Key       : Key_Type) return Reference_Type
+      is
+         Node : constant Count_Type := Key_Keys.Find (Container, Key);
+
+      begin
+         if Node = 0 then
+            raise Constraint_Error with "key not in set";
+         end if;
+
+         declare
+            N : Node_Type renames Container.Nodes (Node);
+         begin
+            return (Element => N.Element'Access);
+         end;
+      end Reference_Preserving_Key;
+
       -------------
       -- Replace --
       -------------
@@ -900,46 +1014,10 @@ 
          raise Program_Error with "key was modified";
       end Update_Element_Preserving_Key;
 
-      function Reference_Preserving_Key
-        (Container : aliased in out Set;
-         Key       : Key_Type) return Constant_Reference_Type
-      is
-         Position : constant Cursor := Find (Container, Key);
+      -----------
+      -- Write --
+      -----------
 
-      begin
-         if Position.Node = 0 then
-            raise Constraint_Error with "Position cursor has no element";
-         end if;
-
-         return
-           (Element =>
-              Container.Nodes (Position.Node).Element'Unrestricted_Access);
-      end Reference_Preserving_Key;
-
-      function Reference_Preserving_Key
-        (Container : aliased in out Set;
-         Key       : Key_Type) return Reference_Type
-      is
-         Position : constant Cursor := Find (Container, Key);
-
-      begin
-         if Position.Node = 0 then
-            raise Constraint_Error with "Position cursor has no element";
-         end if;
-
-         return
-           (Element =>
-              Container.Nodes (Position.Node).Element'Unrestricted_Access);
-      end Reference_Preserving_Key;
-
-      procedure  Read
-        (Stream : not null access Root_Stream_Type'Class;
-         Item   : out Reference_Type)
-      is
-      begin
-         raise Program_Error with "attempt to stream reference";
-      end Read;
-
       procedure Write
         (Stream : not null access Root_Stream_Type'Class;
          Item   : Reference_Type)
@@ -1585,22 +1663,6 @@ 
       raise Program_Error with "attempt to stream reference";
    end Read;
 
-   ---------------
-   -- Reference --
-   ---------------
-
-   function Constant_Reference (Container : Set; Position : Cursor)
-   return Constant_Reference_Type
-   is
-   begin
-      if Position.Container = null then
-         raise Constraint_Error with "Position cursor has no element";
-      end if;
-
-      return (Element =>
-        Container.Nodes (Position.Node).Element'Unrestricted_Access);
-   end Constant_Reference;
-
    -------------
    -- Replace --
    -------------
Index: a-cborse.ads
===================================================================
--- a-cborse.ads	(revision 183051)
+++ a-cborse.ads	(working copy)
@@ -65,16 +65,6 @@ 
    package Set_Iterator_Interfaces is new
      Ada.Iterator_Interfaces (Cursor, Has_Element);
 
-   type Constant_Reference_Type
-      (Element : not null access constant Element_Type) is
-   private
-   with
-      Implicit_Dereference => Element;
-
-   function Constant_Reference
-     (Container : Set; Position : Cursor)
-   return Constant_Reference_Type;
-
    function "=" (Left, Right : Set) return Boolean;
 
    function Equivalent_Sets (Left, Right : Set) return Boolean;
@@ -98,6 +88,16 @@ 
      (Position : Cursor;
       Process  : not null access procedure (Element : Element_Type));
 
+   type Constant_Reference_Type
+      (Element : not null access constant Element_Type) is
+   private
+   with
+      Implicit_Dereference => Element;
+
+   function Constant_Reference
+     (Container : aliased Set;
+      Position  : Cursor) return Constant_Reference_Type;
+
    procedure Assign (Target : in out Set; Source : Set);
 
    function Copy (Source : Set; Capacity : Count_Type := 0) return Set;
@@ -263,6 +263,10 @@ 
 
       function Reference_Preserving_Key
         (Container : aliased in out Set;
+         Position  : Cursor) return Reference_Type;
+
+      function Constant_Reference
+        (Container : aliased Set;
          Key       : Key_Type) return Constant_Reference_Type;
 
       function Reference_Preserving_Key
@@ -297,7 +301,7 @@ 
       Left    : Count_Type;
       Right   : Count_Type;
       Color   : Red_Black_Trees.Color_Type := Red_Black_Trees.Red;
-      Element : Element_Type;
+      Element : aliased Element_Type;
    end record;
 
    package Tree_Types is
Index: a-comutr.adb
===================================================================
--- a-comutr.adb	(revision 183051)
+++ a-comutr.adb	(working copy)
@@ -437,6 +437,36 @@ 
       pragma Assert (Children_Count = Container_Count);
    end Clear;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased Tree;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
+
+      if Position.Node = Root_Node (Container) then
+         raise Program_Error with "Position cursor designates root";
+      end if;
+
+      --  Implement Vet for multiway tree???
+      --  pragma Assert (Vet (Position),
+      --                 "Position cursor in Constant_Reference is bad");
+
+      return (Element => Position.Node.Element'Access);
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -2000,24 +2030,30 @@ 
    -- Reference --
    ---------------
 
-   function Constant_Reference
-     (Container : aliased Tree;
-      Position  : Cursor) return Constant_Reference_Type
-   is
-   begin
-      pragma Unreferenced (Container);
-
-      return (Element => Position.Node.Element'Unrestricted_Access);
-   end Constant_Reference;
-
    function Reference
-     (Container : aliased Tree;
+     (Container : aliased in out Tree;
       Position  : Cursor) return Reference_Type
    is
    begin
-      pragma Unreferenced (Container);
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
 
-      return (Element => Position.Node.Element'Unrestricted_Access);
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
+
+      if Position.Node = Root_Node (Container) then
+         raise Program_Error with "Position cursor designates root";
+      end if;
+
+      --  Implement Vet for multiway tree???
+      --  pragma Assert (Vet (Position),
+      --                 "Position cursor in Constant_Reference is bad");
+
+      return (Element => Position.Node.Element'Access);
    end Reference;
 
    --------------------
Index: a-comutr.ads
===================================================================
--- a-comutr.ads	(revision 183051)
+++ a-comutr.ads	(working copy)
@@ -108,6 +108,14 @@ 
      (Element : not null access Element_Type) is private
         with Implicit_Dereference => Element;
 
+   function Constant_Reference
+     (Container : aliased Tree;
+      Position  : Cursor) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out Tree;
+      Position  : Cursor) return Reference_Type;
+
    procedure Assign (Target : in out Tree; Source : Tree);
 
    function Copy (Source : Tree) return Tree;
@@ -341,7 +349,7 @@ 
       Prev     : Tree_Node_Access;
       Next     : Tree_Node_Access;
       Children : Children_Type;
-      Element  : Element_Type;
+      Element  : aliased Element_Type;
    end record;
    pragma Convention (C, Tree_Node_Type);
 
@@ -445,14 +453,6 @@ 
 
    for Reference_Type'Write use Write;
 
-   function Constant_Reference
-     (Container : aliased Tree;
-      Position  : Cursor) return Constant_Reference_Type;
-
-   function Reference
-     (Container : aliased Tree;
-      Position  : Cursor) return Reference_Type;
-
    Empty_Tree : constant Tree := (Controlled with others => <>);
 
    No_Element : constant Cursor := (others => <>);
Index: a-ciorma.adb
===================================================================
--- a-ciorma.adb	(revision 183051)
+++ a-ciorma.adb	(working copy)
@@ -358,12 +358,46 @@ 
    ------------------------
 
    function Constant_Reference
+     (Container : aliased Map;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong map";
+      end if;
+
+      if Position.Node.Element = null then
+         raise Program_Error with "Node has no element";
+      end if;
+
+      pragma Assert (Vet (Container.Tree, Position.Node),
+                     "Position cursor in Constant_Reference is bad");
+
+      return (Element => Position.Node.Element.all'Access);
+   end Constant_Reference;
+
+   function Constant_Reference
      (Container : Map;
       Key       : Key_Type) return Constant_Reference_Type
    is
-      Node : aliased Element_Type := Element (Container, Key);
+      Node : constant Node_Access := Key_Ops.Find (Container.Tree, Key);
+
    begin
-      return (Element => Node'Access);
+      if Node = null then
+         raise Constraint_Error with "key not in map";
+      end if;
+
+      if Node.Element = null then
+         raise Program_Error with "Node has no element";
+      end if;
+
+      return (Element => Node.Element.all'Access);
    end Constant_Reference;
 
    --------------
@@ -1305,15 +1339,48 @@ 
    ---------------
 
    function Reference
-     (Container : Map;
-      Key       : Key_Type)
-      return Reference_Type
+     (Container : aliased in out Map;
+      Position  : Cursor) return Reference_Type
    is
-      Node : aliased Element_Type := Element (Container, Key);
    begin
-      return (Element => Node'Access);
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong map";
+      end if;
+
+      if Position.Node.Element = null then
+         raise Program_Error with "Node has no element";
+      end if;
+
+      pragma Assert (Vet (Container.Tree, Position.Node),
+                     "Position cursor in function Reference is bad");
+
+      return (Element => Position.Node.Element.all'Access);
    end Reference;
 
+   function Reference
+     (Container : aliased in out Map;
+      Key       : Key_Type) return Reference_Type
+   is
+      Node : constant Node_Access := Key_Ops.Find (Container.Tree, Key);
+
+   begin
+      if Node = null then
+         raise Constraint_Error with "key not in map";
+      end if;
+
+      if Node.Element = null then
+         raise Program_Error with "Node has no element";
+      end if;
+
+      return (Element => Node.Element.all'Access);
+   end Reference;
+
    -------------
    -- Replace --
    -------------
Index: a-cobove.adb
===================================================================
--- a-cobove.adb	(revision 183051)
+++ a-cobove.adb	(working copy)
@@ -378,6 +378,52 @@ 
       Container.Last := No_Index;
    end Clear;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased Vector;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with "Position cursor denotes wrong container";
+      end if;
+
+      if Position.Index > Position.Container.Last then
+         raise Constraint_Error with "Position cursor is out of range";
+      end if;
+
+      declare
+         A : Elements_Array renames Container.Elements;
+         I : constant Count_Type := To_Array_Index (Position.Index);
+      begin
+         return (Element => A (I)'Access);
+      end;
+   end Constant_Reference;
+
+   function Constant_Reference
+     (Container : aliased Vector;
+      Index     : Index_Type) return Constant_Reference_Type
+   is
+   begin
+      if Index > Container.Last then
+         raise Constraint_Error with "Index is out of range";
+      end if;
+
+      declare
+         A : Elements_Array renames Container.Elements;
+         I : constant Count_Type := To_Array_Index (Index);
+      begin
+         return (Element => A (I)'Access);
+      end;
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -2071,76 +2117,46 @@ 
    -- Reference --
    ---------------
 
-   function Constant_Reference
-     (Container : Vector;
-      Position  : Cursor)    --  SHOULD BE ALIASED
-      return Constant_Reference_Type
+   function Reference
+     (Container : aliased in out Vector;
+      Position  : Cursor) return Reference_Type
    is
    begin
-      pragma Unreferenced (Container);
-
       if Position.Container = null then
          raise Constraint_Error with "Position cursor has no element";
       end if;
 
-      if Position.Index > Position.Container.Last then
-         raise Constraint_Error with "Position cursor is out of range";
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with "Position cursor denotes wrong container";
       end if;
 
-      return
-       (Element =>
-          Position.Container.Elements
-            (To_Array_Index (Position.Index))'Access);
-   end Constant_Reference;
-
-   function Constant_Reference
-     (Container : Vector;
-      Position  : Index_Type)
-      return Constant_Reference_Type
-   is
-   begin
-      if (Position) > Container.Last then
-         raise Constraint_Error with "Index is out of range";
-      end if;
-
-      return (Element =>
-                Container.Elements (To_Array_Index (Position))'Access);
-   end Constant_Reference;
-
-   function Reference
-     (Container : Vector;
-      Position  : Cursor)
-      return Reference_Type
-   is
-   begin
-      pragma Unreferenced (Container);
-
-      if Position.Container = null then
-         raise Constraint_Error with "Position cursor has no element";
-      end if;
-
       if Position.Index > Position.Container.Last then
          raise Constraint_Error with "Position cursor is out of range";
       end if;
 
-      return
-        (Element =>
-           Position.Container.Elements
-             (To_Array_Index (Position.Index))'Access);
+      declare
+         A : Elements_Array renames Container.Elements;
+         I : constant Count_Type := To_Array_Index (Position.Index);
+      begin
+         return (Element => A (I)'Access);
+      end;
    end Reference;
 
    function Reference
-     (Container : Vector;
-      Position  : Index_Type)
-      return Reference_Type
+     (Container : aliased in out Vector;
+      Index     : Index_Type) return Reference_Type
    is
    begin
-      if Position > Container.Last then
+      if Index > Container.Last then
          raise Constraint_Error with "Index is out of range";
-      else
-         return (Element =>
-           Container.Elements (To_Array_Index (Position))'Unrestricted_Access);
       end if;
+
+      declare
+         A : Elements_Array renames Container.Elements;
+         I : constant Count_Type := To_Array_Index (Index);
+      begin
+         return (Element => A (I)'Access);
+      end;
    end Reference;
 
    ---------------------
Index: a-ciorma.ads
===================================================================
--- a-ciorma.ads	(revision 183051)
+++ a-ciorma.ads	(working copy)
@@ -50,7 +50,7 @@ 
    function Equivalent_Keys (Left, Right : Key_Type) return Boolean;
 
    type Map is tagged private
-   with constant_Indexing => Constant_Reference,
+   with Constant_Indexing => Constant_Reference,
         Variable_Indexing => Reference,
         Default_Iterator  => Iterate,
         Iterator_Element  => Element_Type;
@@ -96,6 +96,31 @@ 
       Process   : not null access procedure (Key     : Key_Type;
                                              Element : in out Element_Type));
 
+   type Constant_Reference_Type
+      (Element : not null access constant Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   type Reference_Type (Element : not null access Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Position  : Cursor) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out Map;
+      Position  : Cursor) return Reference_Type;
+
+   function Constant_Reference
+     (Container : aliased Map;
+      Key       : Key_Type) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out Map;
+      Key       : Key_Type) return Reference_Type;
+
    procedure Assign (Target : in out Map; Source : Map);
 
    function Copy (Source : Map) return Map;
@@ -176,23 +201,6 @@ 
 
    function ">" (Left : Key_Type; Right : Cursor) return Boolean;
 
-   type Constant_Reference_Type
-      (Element : not null access constant Element_Type) is private
-   with
-      Implicit_Dereference => Element;
-
-   type Reference_Type (Element : not null access Element_Type) is private
-   with
-      Implicit_Dereference => Element;
-
-   function Constant_Reference
-     (Container : Map;
-      Key       : Key_Type) return Constant_Reference_Type;
-
-   function Reference
-     (Container : Map;
-       Key      : Key_Type) return Reference_Type;
-
    procedure Iterate
      (Container : Map;
       Process   : not null access procedure (Position : Cursor));
Index: a-cobove.ads
===================================================================
--- a-cobove.ads	(revision 183051)
+++ a-cobove.ads	(working copy)
@@ -142,6 +142,56 @@ 
       Position  : Cursor;
       Process   : not null access procedure (Element : in out Element_Type));
 
+   type Constant_Reference_Type
+      (Element : not null access constant Element_Type) is
+   private
+   with
+      Implicit_Dereference => Element;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Constant_Reference_Type);
+
+   for Constant_Reference_Type'Read use Read;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Constant_Reference_Type);
+
+   for Constant_Reference_Type'Write use Write;
+
+   type Reference_Type (Element : not null access Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Reference_Type);
+
+   for Reference_Type'Read use Read;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Reference_Type);
+
+   for Reference_Type'Write use Write;
+
+   function Constant_Reference
+     (Container : aliased Vector;
+      Position  : Cursor) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out Vector;
+      Position  : Cursor) return Reference_Type;
+
+   function Constant_Reference
+     (Container : aliased Vector;
+      Index     : Index_Type) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out Vector;
+      Index     : Index_Type) return Reference_Type;
+
    procedure Assign (Target : in out Vector; Source : Vector);
 
    function Copy (Source : Vector; Capacity : Count_Type := 0) return Vector;
@@ -308,54 +358,6 @@ 
       Start     : Cursor)
       return Vector_Iterator_Interfaces.Reversible_Iterator'class;
 
-   type Constant_Reference_Type
-      (Element : not null access constant Element_Type) is
-   private
-   with
-      Implicit_Dereference => Element;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Constant_Reference_Type);
-
-   for Constant_Reference_Type'Read use Read;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Constant_Reference_Type);
-
-   for Constant_Reference_Type'Write use Write;
-
-   type Reference_Type (Element : not null access Element_Type) is private
-   with
-      Implicit_Dereference => Element;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Reference_Type);
-
-   for Reference_Type'Read use Read;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Reference_Type);
-
-   for Reference_Type'Write use Write;
-
-   function Constant_Reference
-     (Container : Vector; Position : Cursor)    --  SHOULD BE ALIASED
-   return Constant_Reference_Type;
-
-   function Constant_Reference
-     (Container : Vector; Position : Index_Type)
-   return Constant_Reference_Type;
-
-   function Reference (Container : Vector; Position : Cursor)
-   return Reference_Type;
-
-   function Reference (Container : Vector; Position : Index_Type)
-   return Reference_Type;
-
    generic
       with function "<" (Left, Right : Element_Type) return Boolean is <>;
    package Generic_Sorting is
Index: a-convec.adb
===================================================================
--- a-convec.adb	(revision 183051)
+++ a-convec.adb	(working copy)
@@ -478,6 +478,42 @@ 
       end if;
    end Clear;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased Vector;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with "Position cursor denotes wrong container";
+      end if;
+
+      if Position.Index > Position.Container.Last then
+         raise Constraint_Error with "Position cursor is out of range";
+      end if;
+
+      return (Element => Container.Elements.EA (Position.Index)'Access);
+   end Constant_Reference;
+
+   function Constant_Reference
+     (Container : aliased Vector;
+      Index     : Index_Type) return Constant_Reference_Type
+   is
+   begin
+      if Index > Container.Last then
+         raise Constraint_Error with "Index is out of range";
+      else
+         return (Element => Container.Elements.EA (Index)'Access);
+      end if;
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -2538,64 +2574,35 @@ 
    -- Reference --
    ---------------
 
-   function Constant_Reference
-     (Container : Vector;
-      Position  : Cursor)    --  SHOULD BE ALIASED
-      return Constant_Reference_Type
+   function Reference
+     (Container : aliased in out Vector;
+      Position  : Cursor) return Reference_Type
    is
    begin
-      pragma Unreferenced (Container);
-
       if Position.Container = null then
          raise Constraint_Error with "Position cursor has no element";
       end if;
 
-      if Position.Index > Position.Container.Last then
-         raise Constraint_Error with "Position cursor is out of range";
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with "Position cursor denotes wrong container";
       end if;
 
-      return
-       (Element =>
-          Position.Container.Elements.EA (Position.Index)'Access);
-   end Constant_Reference;
-
-   function Constant_Reference
-     (Container : Vector;
-      Position  : Index_Type)
-      return Constant_Reference_Type
-   is
-   begin
-      if Position > Container.Last then
-         raise Constraint_Error with "Index is out of range";
-      else
-         return (Element => Container.Elements.EA (Position)'Access);
-      end if;
-   end Constant_Reference;
-
-   function Reference (Container : Vector; Position : Cursor)
-   return Reference_Type is
-   begin
-      pragma Unreferenced (Container);
-
-      if Position.Container = null then
-         raise Constraint_Error with "Position cursor has no element";
-      end if;
-
       if Position.Index > Position.Container.Last then
          raise Constraint_Error with "Position cursor is out of range";
       end if;
 
-      return
-        (Element => Position.Container.Elements.EA (Position.Index)'Access);
+      return (Element => Container.Elements.EA (Position.Index)'Access);
    end Reference;
 
-   function Reference (Container : Vector; Position : Index_Type)
-   return Reference_Type is
+   function Reference
+     (Container : aliased in out Vector;
+      Index     : Index_Type) return Reference_Type
+   is
    begin
-      if Position > Container.Last then
+      if Index > Container.Last then
          raise Constraint_Error with "Index is out of range";
       else
-         return (Element => Container.Elements.EA (Position)'Access);
+         return (Element => Container.Elements.EA (Index)'Access);
       end if;
    end Reference;
 
Index: a-convec.ads
===================================================================
--- a-convec.ads	(revision 183051)
+++ a-convec.ads	(working copy)
@@ -189,19 +189,21 @@ 
    for Reference_Type'Read use Read;
 
    function Constant_Reference
-     (Container : Vector; Position : Cursor)    --  SHOULD BE ALIASED
-   return Constant_Reference_Type;
+     (Container : aliased Vector;
+      Position  : Cursor) return Constant_Reference_Type;
 
+   function Reference
+     (Container : aliased in out Vector;
+      Position  : Cursor) return Reference_Type;
+
    function Constant_Reference
-     (Container : Vector; Position : Index_Type)
-   return Constant_Reference_Type;
+     (Container : aliased Vector;
+      Index     : Index_Type) return Constant_Reference_Type;
 
-   function Reference (Container : Vector; Position : Cursor)
-   return Reference_Type;
+   function Reference
+     (Container : aliased in out Vector;
+      Index     : Index_Type) return Reference_Type;
 
-   function Reference (Container : Vector; Position : Index_Type)
-   return Reference_Type;
-
    procedure Assign (Target : in out Vector; Source : Vector);
 
    function Copy (Source : Vector; Capacity : Count_Type := 0) return Vector;
Index: a-cohase.adb
===================================================================
--- a-cohase.adb	(revision 183051)
+++ a-cohase.adb	(working copy)
@@ -198,6 +198,29 @@ 
       HT_Ops.Clear (Container.HT);
    end Clear;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased Set;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
+
+      pragma Assert (Vet (Position), "bad cursor in Constant_Reference");
+
+      return (Element => Position.Node.Element'Access);
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -1126,19 +1149,6 @@ 
          raise;
    end Read_Node;
 
-   ---------------
-   -- Reference --
-   ---------------
-
-   function Constant_Reference
-     (Container : aliased Set;
-      Position  : Cursor) return Constant_Reference_Type
-   is
-      pragma Unreferenced (Container);
-   begin
-      return (Element => Position.Node.Element'Unrestricted_Access);
-   end Constant_Reference;
-
    -------------
    -- Replace --
    -------------
@@ -1720,6 +1730,25 @@ 
            Hash      => Hash,
            Equivalent_Keys => Equivalent_Key_Node);
 
+      ------------------------
+      -- Constant_Reference --
+      ------------------------
+
+      function Constant_Reference
+        (Container : aliased Set;
+         Key       : Key_Type) return Constant_Reference_Type
+      is
+         Node : constant Node_Access :=
+                  Key_Keys.Find (Container.HT, Key);
+
+      begin
+         if Node = null then
+            raise Constraint_Error with "Key not in set";
+         end if;
+
+         return (Element => Node.Element'Access);
+      end Constant_Reference;
+
       --------------
       -- Contains --
       --------------
@@ -1831,6 +1860,66 @@ 
          return Key (Position.Node.Element);
       end Key;
 
+      ----------
+      -- Read --
+      ----------
+
+      procedure Read
+        (Stream : not null access Root_Stream_Type'Class;
+         Item   : out Reference_Type)
+      is
+      begin
+         raise Program_Error with "attempt to stream reference";
+      end Read;
+
+      ------------------------------
+      -- Reference_Preserving_Key --
+      ------------------------------
+
+      function Reference_Preserving_Key
+        (Container : aliased in out Set;
+         Position  : Cursor) return Reference_Type
+      is
+      begin
+         if Position.Container = null then
+            raise Constraint_Error with "Position cursor has no element";
+         end if;
+
+         if Position.Container /= Container'Unrestricted_Access then
+            raise Program_Error with
+              "Position cursor designates wrong container";
+         end if;
+
+         pragma Assert
+           (Vet (Position),
+            "bad cursor in function Reference_Preserving_Key");
+
+         --  Some form of finalization will be required in order to actually
+         --  check that the key-part of the element designated by Position has
+         --  not changed.  ???
+
+         return (Element => Position.Node.Element'Access);
+      end Reference_Preserving_Key;
+
+      function Reference_Preserving_Key
+        (Container : aliased in out Set;
+         Key       : Key_Type) return Reference_Type
+      is
+         Node : constant Node_Access :=
+                  Key_Keys.Find (Container.HT, Key);
+
+      begin
+         if Node = null then
+            raise Constraint_Error with "Key not in set";
+         end if;
+
+         --  Some form of finalization will be required in order to actually
+         --  check that the key-part of the element designated by Key has not
+         --  changed.  ???
+
+         return (Element => Node.Element'Access);
+      end Reference_Preserving_Key;
+
       -------------
       -- Replace --
       -------------
@@ -1952,27 +2041,18 @@ 
          raise Program_Error with "key was modified";
       end Update_Element_Preserving_Key;
 
-      ------------------------------
-      -- Reference_Preserving_Key --
-      ------------------------------
+      -----------
+      -- Write --
+      -----------
 
-      function Reference_Preserving_Key
-        (Container : aliased in out Set;
-         Position  : Cursor) return Reference_Type
+      procedure Write
+        (Stream : not null access Root_Stream_Type'Class;
+         Item   : Reference_Type)
       is
-         pragma Unreferenced (Container);
       begin
-         return (Element => Position.Node.Element'Unrestricted_Access);
-      end Reference_Preserving_Key;
+         raise Program_Error with "attempt to stream reference";
+      end Write;
 
-      function Reference_Preserving_Key
-        (Container : aliased in out Set;
-         Key       : Key_Type) return Reference_Type
-      is
-         Position : constant Cursor := Find (Container, Key);
-      begin
-         return (Element => Position.Node.Element'Unrestricted_Access);
-      end Reference_Preserving_Key;
    end Generic_Keys;
 
 end Ada.Containers.Hashed_Sets;
Index: a-cohase.ads
===================================================================
--- a-cohase.ads	(revision 183051)
+++ a-cohase.ads	(working copy)
@@ -52,7 +52,7 @@ 
 
    type Set is tagged private
    with
-      constant_Indexing => Constant_Reference,
+      Constant_Indexing => Constant_Reference,
       Default_Iterator  => Iterate,
       Iterator_Element  => Element_Type;
 
@@ -145,10 +145,6 @@ 
    --  Calls Process with the element (having only a constant view) of the node
    --  designed by the cursor.
 
-   procedure Assign (Target : in out Set; Source : Set);
-
-   function Copy (Source : Set; Capacity : Count_Type := 0) return Set;
-
    type Constant_Reference_Type
      (Element : not null access constant Element_Type) is private
         with Implicit_Dereference => Element;
@@ -157,6 +153,10 @@ 
      (Container : aliased Set;
       Position  : Cursor) return Constant_Reference_Type;
 
+   procedure Assign (Target : in out Set; Source : Set);
+
+   function Copy (Source : Set; Capacity : Count_Type := 0) return Set;
+
    procedure Move (Target : in out Set; Source : in out Set);
    --  Clears Target (if it's not empty), and then moves (not copies) the
    --  buckets array and nodes from Source to Target.
@@ -422,14 +422,32 @@ 
         (Container : aliased in out Set;
          Position  : Cursor) return Reference_Type;
 
+      function Constant_Reference
+        (Container : aliased Set;
+         Key       : Key_Type) return Constant_Reference_Type;
+
       function Reference_Preserving_Key
         (Container : aliased in out Set;
-         Key  : Key_Type) return Reference_Type;
+         Key       : Key_Type) return Reference_Type;
 
    private
       type Reference_Type (Element : not null access Element_Type)
          is null record;
 
+      use Ada.Streams;
+
+      procedure Read
+        (Stream : not null access Root_Stream_Type'Class;
+         Item   : out Reference_Type);
+
+      for Reference_Type'Read use Read;
+
+      procedure Write
+        (Stream : not null access Root_Stream_Type'Class;
+         Item   : Reference_Type);
+
+      for Reference_Type'Write use Write;
+
    end Generic_Keys;
 
 private
@@ -439,7 +457,7 @@ 
    type Node_Access is access Node_Type;
 
    type Node_Type is limited record
-      Element : Element_Type;
+      Element : aliased Element_Type;
       Next    : Node_Access;
    end record;
 
Index: a-cbdlli.adb
===================================================================
--- a-cbdlli.adb	(revision 183051)
+++ a-cbdlli.adb	(working copy)
@@ -296,6 +296,33 @@ 
       Free (Container, X);
    end Clear;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased List;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
+
+      pragma Assert (Vet (Position), "bad cursor in Constant_Reference");
+
+      declare
+         N : Node_Type renames Container.Nodes (Position.Node);
+      begin
+         return (Element => N.Element'Access);
+      end;
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -1537,34 +1564,27 @@ 
    -- Reference --
    ---------------
 
-   function Constant_Reference
-     (Container : List;
-      Position  : Cursor) return Constant_Reference_Type
+   function Reference
+     (Container : aliased in out List;
+      Position  : Cursor) return Reference_Type
    is
    begin
-      pragma Unreferenced (Container);
-
       if Position.Container = null then
          raise Constraint_Error with "Position cursor has no element";
       end if;
 
-      return (Element =>
-         Position.Container.Nodes (Position.Node).Element'Unrestricted_Access);
-   end Constant_Reference;
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
 
-   function Reference
-     (Container : List;
-      Position  : Cursor) return Reference_Type
-   is
-   begin
-      pragma Unreferenced (Container);
+      pragma Assert (Vet (Position), "bad cursor in function Reference");
 
-      if Position.Container = null then
-         raise Constraint_Error with "Position cursor has no element";
-      end if;
-
-      return (Element =>
-         Position.Container.Nodes (Position.Node).Element'Unrestricted_Access);
+      declare
+         N : Node_Type renames Container.Nodes (Position.Node);
+      begin
+         return (Element => N.Element'Access);
+      end;
    end Reference;
 
    ---------------------
Index: a-cbdlli.ads
===================================================================
--- a-cbdlli.ads	(revision 183051)
+++ a-cbdlli.ads	(working copy)
@@ -88,6 +88,48 @@ 
       Position  : Cursor;
       Process   : not null access procedure (Element : in out Element_Type));
 
+   type Constant_Reference_Type
+      (Element : not null access constant Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Constant_Reference_Type);
+
+   for Constant_Reference_Type'Write use Write;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Constant_Reference_Type);
+
+   for Constant_Reference_Type'Read use Read;
+
+   type Reference_Type
+     (Element : not null access Element_Type) is private
+   with
+      Implicit_Dereference => Element;
+
+   procedure Write
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : Reference_Type);
+
+   for Reference_Type'Write use Write;
+
+   procedure Read
+     (Stream : not null access Root_Stream_Type'Class;
+      Item   : out Reference_Type);
+
+   for Reference_Type'Read use Read;
+
+   function Constant_Reference
+     (Container : aliased List;
+      Position  : Cursor) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out List;
+      Position  : Cursor) return Reference_Type;
+
    procedure Assign (Target : in out List; Source : List);
 
    function Copy (Source : List; Capacity : Count_Type := 0) return List;
@@ -223,48 +265,6 @@ 
 
    end Generic_Sorting;
 
-   type Constant_Reference_Type
-      (Element : not null access constant Element_Type) is private
-   with
-      Implicit_Dereference => Element;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Constant_Reference_Type);
-
-   for Constant_Reference_Type'Write use Write;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Constant_Reference_Type);
-
-   for Constant_Reference_Type'Read use Read;
-
-   type Reference_Type (Element : not null access Element_Type) is
-   private
-   with
-      Implicit_Dereference => Element;
-
-   procedure Write
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : Reference_Type);
-
-   for Reference_Type'Write use Write;
-
-   procedure Read
-     (Stream : not null access Root_Stream_Type'Class;
-      Item   : out Reference_Type);
-
-   for Reference_Type'Read use Read;
-
-   function Constant_Reference
-     (Container : List;       -- SHOULD BE ALIASED ???
-      Position  : Cursor) return Constant_Reference_Type;
-
-   function Reference
-     (Container : List;       -- SHOULD BE ALIASED ???
-      Position  : Cursor) return Reference_Type;
-
 private
 
    pragma Inline (Next);
@@ -273,7 +273,7 @@ 
    type Node_Type is record
       Prev    : Count_Type'Base;
       Next    : Count_Type;
-      Element : Element_Type;
+      Element : aliased Element_Type;
    end record;
 
    type Node_Array is array (Count_Type range <>) of Node_Type;
Index: a-cbmutr.adb
===================================================================
--- a-cbmutr.adb	(revision 183051)
+++ a-cbmutr.adb	(working copy)
@@ -588,6 +588,36 @@ 
       pragma Assert (Count = Container_Count);
    end Clear;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased Tree;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
+
+      if Position.Node = Root_Node (Container) then
+         raise Program_Error with "Position cursor designates root";
+      end if;
+
+      --  Implement Vet for multiway tree???
+      --  pragma Assert (Vet (Position),
+      --                 "Position cursor in Constant_Reference is bad");
+
+      return (Element => Container.Elements (Position.Node)'Access);
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -2464,26 +2494,30 @@ 
    -- Reference --
    ---------------
 
-   function Constant_Reference
-     (Container : aliased Tree;
-      Position  : Cursor) return Constant_Reference_Type
-   is
-      pragma Unreferenced (Container);
-   begin
-      return
-        (Element =>
-           Position.Container.Elements (Position.Node)'Unchecked_Access);
-   end Constant_Reference;
-
    function Reference
-     (Container : aliased Tree;
+     (Container : aliased in out Tree;
       Position  : Cursor) return Reference_Type
    is
-      pragma Unreferenced (Container);
    begin
-      return
-        (Element =>
-           Position.Container.Elements (Position.Node)'Unchecked_Access);
+      if Position.Container = null then
+         raise Constraint_Error with
+           "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
+
+      if Position.Node = Root_Node (Container) then
+         raise Program_Error with "Position cursor designates root";
+      end if;
+
+      --  Implement Vet for multiway tree???
+      --  pragma Assert (Vet (Position),
+      --                 "Position cursor in Constant_Reference is bad");
+
+      return (Element => Container.Elements (Position.Node)'Access);
    end Reference;
 
    --------------------
Index: a-cbmutr.ads
===================================================================
--- a-cbmutr.ads	(revision 183051)
+++ a-cbmutr.ads	(working copy)
@@ -107,6 +107,14 @@ 
      (Element : not null access Element_Type) is private
         with Implicit_Dereference => Element;
 
+   function Constant_Reference
+     (Container : aliased Tree;
+      Position  : Cursor) return Constant_Reference_Type;
+
+   function Reference
+     (Container : aliased in out Tree;
+      Position  : Cursor) return Reference_Type;
+
    procedure Assign (Target : in out Tree; Source : Tree);
 
    function Copy (Source : Tree; Capacity : Count_Type := 0) return Tree;
@@ -375,6 +383,7 @@ 
 
    type Reference_Type
      (Element : not null access Element_Type) is null record;
+
    procedure Write
      (Stream : not null access Root_Stream_Type'Class;
       Item   : Reference_Type);
@@ -385,14 +394,6 @@ 
       Item   : out Reference_Type);
    for Reference_Type'Read use Read;
 
-   function Constant_Reference
-     (Container : aliased Tree;
-      Position  : Cursor) return Constant_Reference_Type;
-
-   function Reference
-     (Container : aliased Tree;
-      Position  : Cursor) return Reference_Type;
-
    Empty_Tree : constant Tree := (Capacity => 0, others => <>);
 
    No_Element : constant Cursor := Cursor'(others => <>);
Index: a-cbhase.adb
===================================================================
--- a-cbhase.adb	(revision 183051)
+++ a-cbhase.adb	(working copy)
@@ -210,6 +210,33 @@ 
       HT_Ops.Clear (Container);
    end Clear;
 
+   ------------------------
+   -- Constant_Reference --
+   ------------------------
+
+   function Constant_Reference
+     (Container : aliased Set;
+      Position  : Cursor) return Constant_Reference_Type
+   is
+   begin
+      if Position.Container = null then
+         raise Constraint_Error with "Position cursor has no element";
+      end if;
+
+      if Position.Container /= Container'Unrestricted_Access then
+         raise Program_Error with
+           "Position cursor designates wrong container";
+      end if;
+
+      pragma Assert (Vet (Position), "bad cursor in Constant_Reference");
+
+      declare
+         N : Node_Type renames Container.Nodes (Position.Node);
+      begin
+         return (Element => N.Element'Access);
+      end;
+   end Constant_Reference;
+
    --------------
    -- Contains --
    --------------
@@ -1145,21 +1172,6 @@ 
       raise Program_Error with "attempt to stream reference";
    end Read;
 
-   ---------------
-   -- Reference --
-   ---------------
-
-   function Constant_Reference
-     (Container : aliased Set;
-      Position  : Cursor) return Constant_Reference_Type
-   is
-      pragma Unreferenced (Container);
-      S : Set renames Position.Container.all;
-      N : Node_Type renames S.Nodes (Position.Node);
-   begin
-      return (Element => N.Element'Unrestricted_Access);
-   end Constant_Reference;
-
    -------------
    -- Replace --
    -------------
@@ -1581,6 +1593,28 @@ 
            Hash      => Hash,
            Equivalent_Keys => Equivalent_Key_Node);
 
+      ------------------------
+      -- Constant_Reference --
+      ------------------------
+
+      function Constant_Reference
+        (Container : aliased Set;
+         Key       : Key_Type) return Constant_Reference_Type
+      is
+         Node : constant Count_Type := Key_Keys.Find (Container, Key);
+
+      begin
+         if Node = 0 then
+            raise Constraint_Error with "key not in set";
+         end if;
+
+         declare
+            N : Node_Type renames Container.Nodes (Node);
+         begin
+            return (Element => N.Element'Access);
+         end;
+      end Constant_Reference;
+
       --------------
       -- Contains --
       --------------
@@ -1686,6 +1720,69 @@ 
          return Key (Position.Container.Nodes (Position.Node).Element);
       end Key;
 
+      ----------
+      -- Read --
+      ----------
+
+      procedure  Read
+        (Stream : not null access Root_Stream_Type'Class;
+         Item   : out Reference_Type)
+      is
+      begin
+         raise Program_Error with "attempt to stream reference";
+      end Read;
+
+      ------------------------------
+      -- Reference_Preserving_Key --
+      ------------------------------
+
+      function Reference_Preserving_Key
+        (Container : aliased in out Set;
+         Position  : Cursor) return Reference_Type
+      is
+      begin
+         if Position.Container = null then
+            raise Constraint_Error with "Position cursor has no element";
+         end if;
+
+         if Position.Container /= Container'Unrestricted_Access then
+            raise Program_Error with
+              "Position cursor designates wrong container";
+         end if;
+
+         pragma Assert
+           (Vet (Position),
+            "bad cursor in function Reference_Preserving_Key");
+
+         --  Some form of finalization will be required in order to actually
+         --  check that the key-part of the element designated by Position has
+         --  not changed.  ???
+
+         declare
+            N : Node_Type renames Container.Nodes (Position.Node);
+         begin
+            return (Element => N.Element'Access);
+         end;
+      end Reference_Preserving_Key;
+
+      function Reference_Preserving_Key
+        (Container : aliased in out Set;
+         Key       : Key_Type) return Reference_Type
+      is
+         Node : constant Count_Type := Key_Keys.Find (Container, Key);
+
+      begin
+         if Node = 0 then
+            raise Constraint_Error with "key not in set";
+         end if;
+
+         declare
+            N : Node_Type renames Container.Nodes (Node);
+         begin
+            return (Element => N.Element'Access);
+         end;
+      end Reference_Preserving_Key;
+
       -------------
       -- Replace --
       -------------
@@ -1806,29 +1903,18 @@ 
          raise Program_Error with "key was modified";
       end Update_Element_Preserving_Key;
 
-      ------------------------------
-      -- Reference_Preserving_Key --
-      ------------------------------
+      -----------
+      -- Write --
+      -----------
 
-      function Reference_Preserving_Key
-        (Container : aliased in out Set;
-         Position  : Cursor) return Reference_Type
+      procedure Write
+        (Stream : not null access Root_Stream_Type'Class;
+         Item   : Reference_Type)
       is
-         N : Node_Type renames Container.Nodes (Position.Node);
       begin
-         return (Element => N.Element'Unrestricted_Access);
-      end Reference_Preserving_Key;
+         raise Program_Error with "attempt to stream reference";
+      end Write;
 
-      function Reference_Preserving_Key
-        (Container : aliased in out Set;
-         Key       : Key_Type) return Reference_Type
-      is
-         Position : constant Cursor := Find (Container, Key);
-         N        : Node_Type renames Container.Nodes (Position.Node);
-      begin
-         return (Element => N.Element'Unrestricted_Access);
-      end Reference_Preserving_Key;
-
    end Generic_Keys;
 
 end Ada.Containers.Bounded_Hashed_Sets;
Index: a-cbhase.ads
===================================================================
--- a-cbhase.ads	(revision 183051)
+++ a-cbhase.ads	(working copy)
@@ -433,6 +433,10 @@ 
         (Container : aliased in out Set;
          Position  : Cursor) return Reference_Type;
 
+      function Constant_Reference
+        (Container : aliased Set;
+         Key       : Key_Type) return Constant_Reference_Type;
+
       function Reference_Preserving_Key
         (Container : aliased in out Set;
          Key       : Key_Type) return Reference_Type;
@@ -441,13 +445,27 @@ 
       type Reference_Type (Element : not null access Element_Type)
          is null record;
 
+      use Ada.Streams;
+
+      procedure Read
+        (Stream : not null access Root_Stream_Type'Class;
+         Item   : out Reference_Type);
+
+      for Reference_Type'Read use Read;
+
+      procedure Write
+        (Stream : not null access Root_Stream_Type'Class;
+         Item   : Reference_Type);
+
+      for Reference_Type'Write use Write;
+
    end Generic_Keys;
 
 private
    pragma Inline (Next);
 
    type Node_Type is record
-      Element : Element_Type;
+      Element : aliased Element_Type;
       Next    : Count_Type;
    end record;