Index: src/natools-s_expressions-enumeration_io.adb
==================================================================
--- src/natools-s_expressions-enumeration_io.adb
+++ src/natools-s_expressions-enumeration_io.adb
@@ -1,7 +1,7 @@
 ------------------------------------------------------------------------------
--- Copyright (c) 2015, Natacha Porté                                        --
+-- Copyright (c) 2015-2019, Natacha Porté                                   --
 --                                                                          --
 -- Permission to use, copy, modify, and distribute this software for any    --
 -- purpose with or without fee is hereby granted, provided that the above   --
 -- copyright notice and this permission notice appear in all copies.        --
 --                                                                          --
@@ -58,9 +58,18 @@
 
       function Value (Data : Atom) return Enum is
       begin
          return Enum'Value (To_Image (Data));
       end Value;
+
+      function Value (Data : Atom; Default : Enum) return Enum is
+         Img : constant String := To_Image (Data);
+      begin
+         return Enum'Value (Img);
+      exception
+         when Constraint_Error =>
+            return Default;
+      end Value;
 
    end Typed_IO;
 
 end Natools.S_Expressions.Enumeration_IO;

Index: src/natools-s_expressions-enumeration_io.ads
==================================================================
--- src/natools-s_expressions-enumeration_io.ads
+++ src/natools-s_expressions-enumeration_io.ads
@@ -1,7 +1,7 @@
 ------------------------------------------------------------------------------
--- Copyright (c) 2015, Natacha Porté                                        --
+-- Copyright (c) 2015-2019, Natacha Porté                                   --
 --                                                                          --
 -- Permission to use, copy, modify, and distribute this software for any    --
 -- purpose with or without fee is hereby granted, provided that the above   --
 -- copyright notice and this permission notice appear in all copies.        --
 --                                                                          --
@@ -38,9 +38,13 @@
       function Image (T : Enum) return Atom;
          --  Convert an enumeration value into an atom
 
       function Value (Data : Atom) return Enum;
          --  Convert an atom into an enumeration value
+
+      function Value (Data : Atom; Default : Enum) return Enum;
+         --  Convert an atom into an enumeration value,
+         --  with a default value on invalid atom images
 
    end Typed_IO;
 
 end Natools.S_Expressions.Enumeration_IO;