Re: private "subtype"s

[Ted Dennison <dennison@telepath.com>]

In article <8rsubg$ka7$1@news-hrz.uni-duisburg.de>,
  sb463ba@l1-hrz.uni-duisburg.de (Georg Bauhaus) wrote:
> package Whoops is  -- illegal!
>
>    subtype Constr is private;
>    --  [[Constr]] is constrained, but the constraints need
>    -- not be known outside
>
> private
>    subtype Constr is Natural range 0..99;
> end Whoops;

That makes a little bit of sense. After all, if the client doesn't know
that Constr is a subtype of Natural, then what should the compiler do if
the client tries to assign a Constr to an Integer? The most probable
answer is "report an error". But if that's the case, Constr is really no
better to the client than a derived type. If fact, its worse. So why not
just use a derived type and be done with it?

--
T.E.D.

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