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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: renames usage
Date: Sat, 02 Jan 2021 17:22:27 +0000
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"G.B." <bauhaus@notmyhomepage.invalid> writes:

> On 01.01.21 13:39, DrPi wrote:
>
>> Reading all the answers, I understand that :
>>      X : Float renames Random (Seed);
>> is equivalent to :
>>      X : constant Float := Random (Seed);
>> Right ?
>
> Also remember that limited types do not permit copying,
> whether constant or not. Renaming avoids having to move
> an object at all:

Another reason for renaming, which includes the above, would be
remembering a view conversion. The example to hand involves
Timing_Events.

The spec

   --  Support flashing an LED (for example, to indicate that a
   --  packet has been received from the controller).

   type Flasher (The_LED : not null access Crazyflie_LED)
     is tagged limited private;

   procedure Set (The_Flasher : in out Flasher);
   --  Lights the associated LED for 5 ms.

In the private part

   type Flasher (The_LED : not null access Crazyflie_LED)
     is new Ada.Real_Time.Timing_Events.Timing_Event with null record;

In the body

   protected Flasher_Handler is
      pragma Interrupt_Priority;
      procedure Turn_Off_The_LED            -- the Timing_Event_Handler
        (Event : in out ARTTE.Timing_Event);
      --  We "know" that the Event is actually a Flasher.
   end Flasher_Handler;

.. and finally

   protected body Flasher_Handler is
      procedure Turn_Off_The_LED
        (Event : in out ARTTE.Timing_Event) is
         The_Flasher : Flasher                                  -- <<<<
           renames Flasher (ARTTE.Timing_Event'Class (Event));  -- <<<<
      begin
         Set (The_Flasher.The_LED.all, False);
      end Turn_Off_The_LED;
   end Flasher_Handler;