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From: Victor Porton <porton@narod.ru>
Newsgroups: comp.lang.ada
Subject: Re: 'Size hack for enumerated types
Date: Sun, 06 Jul 2014 01:18:08 +0300
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Date: 2014-07-06T01:18:08+03:00
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I tried to implement it in a memory savvy way. But GNAT does not compile it. 
It would be good if a future version of Ada supported it.

-- rds.ads
package RDF is
end RDF;

-- rdf-auxilary.ads
with Interfaces.C;

package RDF.Auxilary is

   generic
      type Enum_Type is range <>;
   package Convert_Enum is
      function To_C(Argument: Enum_Type) return Interfaces.C.int;
      function From_C(Argument: Interfaces.C.int) return Enum_Type;
   end;

end RDF.Auxilary;

-- rdf-auxilary.adb
with Ada.Unchecked_Conversion;

package body RDF.Auxilary is

   package body Convert_Enum is
      
      type Small is mod 2**(Enum_Type'Size);
      
      function To_C_Internal is
        new Ada.Unchecked_Conversion (Source => Enum_Type, Target => Small);

      function From_C_Internal is
        new Ada.Unchecked_Conversion (Source => Small, Target => Enum_Type);
      
      function To_C(Argument: Enum_Type) return Interfaces.C.int is
      begin
         return Interfaces.C.int(To_C_Internal(Argument));
      end;
            
      function From_C(Argument: Interfaces.C.int) return Enum_Type is
      begin
         return From_C_Internal(Small(Argument));
      end;

   end;

end RDF.Auxilary;

gnatmake -q -c -gnatc -u -P/home/porton/Projects/redland-
bindings/ada/test.gpr -XRUNTIME=full -XMODE=Install rdf-auxilary.adb
rdf-auxilary.adb:7:25: non-static expression used for modular type bound
rdf-auxilary.adb:7:38: size attribute is only static for static scalar type 
(RM 4.9(7,8))
gnatmake: "/home/porton/Projects/redland-bindings/ada/src/rdf-auxilary.adb" 
compilation error


-- 
Victor Porton - http://portonvictor.org