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From: "Samuel A. Mize" <smize@magellan.bgm.link.com>
Subject: Re: ObjectAda vs Gnat -- bugs
Date: 1997/05/15
Message-ID: <337B4CF4.41C6@magellan.bgm.link.com>#1/1
X-Deja-AN: 241791479
References: <5lf6ka$nbg@service.polymtl.ca>
Organization: PSI Public Usenet Link
Newsgroups: comp.lang.ada
Date: 1997-05-15T00:00:00+00:00
List-Id: <comp.lang.ada>


granger wrote:
> 
> Here is a shortened version of a package that I wrote.
> 
> It compiles without any error with ObjectAda.
> With gnat3.09, I have the following errors:
> 
> rgbcolor.ads:18:41: expect object name in renaming
> rgbcolor.ads:19:49: expect object name in renaming
> 
> Which of the compilers is correct ?
> 
> If gnat is correct ( probably gnat!!!), 

Good guess!

>the internal package RGB_Value does
>  not have any influence,

Also correct.

>how can I have the enumeration values Gray* and
>  Grey* of the same type or subtype with the same internal value ?

You can't, but you can come close.  An enumeration literal is a function
that returns a value of the enumeration type.  For instance, this works:
    function Fred return character renames 'A';

So, you CAN define your own functions that rename enumeration literals.
For instance, this program compiles and works with GNAT:

   with Text_Io;
   procedure Fred is
      type Color_Type is (Gray0);
      function Grey0 return Color_Type renames Gray0;
   begin
      Text_Io.Put_Line (Color_Type'Image ( Grey0 ));
      -- outputs GRAY0, not GREY0
   end fred;

Whether or not this is a good idea I leave to the engineer on the scene.

Sam Mize

> Thank in advance for any suggestion.
> 
> package rgbcolor is
>         package RGB_Value is
>                 type Color3  is
>                 record
>                         red, green, blue : Float;
>                 end record;
>                 Gray0   : constant Color3 := ( 0.000, 0.000, 0.000 );
>                 Grey0   : Color3 renames Gray0;
>                 Gray1   : constant Color3 := ( 0.012, 0.012, 0.012 );
>                 Grey1   : Color3 renames Gray1;
>         end RGB_Value;
> 
>         type Color_Type is ( Gray0, Gray1 );
> 
>         subtype Grey_Color_Type is Color_Type range Gray0 .. Gray1;
> 
>         Grey0   : Color_Type renames    Gray0;  -- line in error---------------
>         Grey1   : Color_Type renames    Gray1;  -- line in error---------------
> end rgbcolor;

-- Samuel Mize           (817) 619-8622               "Team Ada"
-- Hughes Training Inc.  PO Box 6171 m/s 400, Arlington TX 76005