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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Optimizing Boundary Checks
Date: Sat, 14 Jun 2003 10:34:34 +0200
Organization: At home
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Date: 2003-06-14T10:34:34+02:00
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Vinzent Hoefler wrote:

> As an example, currently
> 
> |x : My_Enum;
> |
> |for i in x'Range loop ...
> 
> doesn't work, you have to write
> 
> |for in in My_Enum'Range loop
> 
> each time. Is there any convincing explanation why it isn't allowed to
> use the actual type of a variable instead of the type itself? I can
> imagine situations (especially with subtypes) where it could be handy
> to use the variables' type instead of an explicit type specification.

Another example where getting the actual type could be useful:

procedure Foo (X, Y : Object'Class) is
begin
   if X in Y'Class then -- Illegal ín Ada
      ...

   [However the same effect could be achieved if Tag were comparable.]

declare
   Z : Y'Class; -- Steals discriminants and the tag
                -- of possibly limited Y

-- 
Regards,
Dmitry A. Kazakov
www.dmitry-kazakov.de