Re: Discriminant within discriminants

[Stephen Leake <stephen_leake@acm.org>]

"stuart clark" <stuart.clark@baesystems.com> writes:

> package message_types
>
>   type id_type is range 1..8;
>
>  type dispense_ack (size:id_type:=id_Type'first) is
>    record
>      dispense_acks:array(1..size) of acks;
>    end record;
>
>   type message_types(dispense_acknowledgement, dispense_request);
>
>   type in_messages(kind :msg_types:=msg_types'first) is
>    record
>     case type is
>       when dispense_acknowledgement =>
>          acknowledgements:dispense_ack;
>       when dispense_request
>          request:integer;
>     end case
>   end record;
>
> end message_types;
>
> i want to declare a message that is of dispense_acknowledgment type
> with a size of 8

Try:

procedure Message_Acks is
   type Id_Type is range 1 .. 8;

   type Acks is new Boolean;

   type Ack_List is array (Id_Type range <>) of Acks;

   type Dispense_Ack (Size : Id_Type := Id_Type'First) is record
      Dispense_Acks : Ack_List (1 .. Size);
   end record;

   type Message_Types is (Dispense_Acknowledgement, Dispense_Request);

   type In_Messages
     (Kind : Message_Types := Message_Types'First;
      Size : ID_Type := Id_Type'First) is
      record
         case Kind is
         when Dispense_Acknowledgement =>
            Acknowledgements : Dispense_Ack (Size);
         when Dispense_Request =>
            Request : Integer;
         end case;
      end record;

    Msg : In_Messages (Dispense_Acknowledgement, Size => 8);
begin -- Message_Test
    null;
end Message_Acks;

-- 
-- Stephe