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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Variant records..
Date: 16 Feb 2004 20:14:42 +0000
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ganesh.ramasivan@gdcanada.com (Ganesh Ramasivan) writes:

> type RADAR_TYPE_CHOICE is (RADAR_A, RADAR_B, RADAR_C);
>     
> type RADAR_A_COMMAND_CHOICE is (RADAR_A_STATE,
>                                 RADAR_A_MODE,
>                                 RADAR_A_DISPLAY_RANGE_SELECT);
>                                       
> type RADAR_B_COMMAND_CHOICE is (RADAR_B_STATE,
>                                 RADAR_B_MODE,
>                                 RADAR_B_DISPLAY_RANGE_SELECT);
> 
> type RADAR_C_COMMAND_CHOICE is (RADAR_C_STATE,
>                                 RADAR_C_MODE,
>                                 RADAR_C_DISPLAY_RANGE_SELECT);

I would say you seem to have a basic concept Radar with a set of
Commands that might apply to any Radar, and three instances of Radar.

   type Radar_Kind is (Radar_A, Radar_B, Radar_C);
   type Radar_Command is (State, Mode, Display_Range_Select);

I can see that you might have different sets of states for Radar_A
than those for Radar_B, but so far your code doesn't say that.

> type RADAR_CHOICE(RADAR_TYPE : RADAR_TYPE_CHOICE :=
> RADAR_TYPE_CHOICE'FIRST) is
>       record   
>         case RADAR_TYPE is
>     	  when  RADAR_A =>
>             null;
>     	  when  RADAR_B  =>
>             null;
>     	  when  RADAR_C =>
>             null;            
>         end case;
>       end record;
> 
> How would I specify a variant record which will only allow me to
> select RADAR_A for the RADAR_TYPE_CHOICE and RADAR_A_STATE for the
> command choice but not RADAR_C_STATE?

I don't see any command choice here?

I don't really grasp why you want this Radar_Choice thing, perhaps it
would help if you could say what you would like to appear in the
places you've marked 'null' ... is it

type RADAR_CHOICE
  (RADAR_TYPE : RADAR_TYPE_CHOICE := RADAR_TYPE_CHOICE'FIRST) is
      record   
        case RADAR_TYPE is
    	  when  RADAR_A =>
            Radar_A_Command : Radar_A_Command_Choice;
    	  when  RADAR_B  =>
            Radar_B_Command : Radar_B_Command_Choice;
    	  when  RADAR_C =>
            Radar_C_Command : Radar_C_Command_Choice;
        end case;
      end record;



Sorry that I'm querying your design intent rather than your actual
question, I haven't understood the question properly!

-- 
Simon Wright                               100% Ada, no bugs.