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From: Matthew Heaney <matthew_heaney@acm.org>
Subject: Re: Question (was Re: How to write TYPECASE in Ada 95?)
Date: 1999/02/24
Message-ID: <m31zjf4ryv.fsf@mheaney.ni.net>#1/1
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NNTP-Posting-Date: Wed, 24 Feb 1999 09:41:05 PDT
Newsgroups: comp.lang.ada
Date: 1999-02-24T00:00:00+00:00
List-Id: <comp.lang.ada>

"Samuel T. Harris" <sam_harris@hso.link.com> writes:

> I just wish Ada didn't use the term class-wide type.
> It is a term with too much overloaded meaning.

The term "class" already had that meaning in Ada83: the class of float
point types, the class of integer types, etc.  It was Tucker's vision
for Ada95 that it preserve as much as possible that Ada83 way of doing
things.

I just wish Ada allowed the attribute T'Class for non-tagged types too.
That would be a way to solve the problem of simultaneous derivation.

For example, if New_Line had been declared something like this:

   procedure New_Line 
    (File    : in File_Type; 
     Spacing : in Positive_Count'Class := 1);

then if we did this:

  package P is

      type File_Type is new Text_IO.File_Type;

      type Positive_Count is new Text_IO.Positive_Count;

  end P;

then you'd get a New_Line at the point of declaration of P.File_Type
that works with type P.Positive_Count.