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From: Shark8 <OneWingedShark@gmail.com>
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Subject: Re: Your wish list for Ada 202X
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You can do that already, with explicitly defined subtypes -- consider:

Input : Integer;

-- ...

Case Input of
   When Integer'First..-1 => -- Handle negative numbers
   When others =>
    Case Natural'(Input) is
     When Natural'First =>   -- Handle 0.
     When Positive'Range =>  -- Handle positives.
    end case;
end case;

But I *do* see how a "implicit subrange" could be interesting/useful.