Re: Rational for not making cursor tagged in Containers

[Robert A Duff <bobduff@shell01.TheWorld.com>]

Georg Bauhaus <bauhaus@futureapps.de> writes:

> On Fri, 2007-04-20 at 17:13 +0200, Dmitry A. Kazakov wrote:
>>  Also I fail to understand why polymorphic objects has to be records
>> and not arrays or access types. Why array or number cannot have
>> discriminants, but records can?
>
> "Uniformity.  Discriminants make sense for any composite type.  In Ada
> 9X, we allow them for any composite type except array types.  The
> array-type restriction is for ease of implementation -- it does not
> simplify the language nor make it easier to use.

Hmm... That sounds like something I would write.

>...Adding another
> restriction for task types would decrease uniformity further.
> Discriminants are allowed for protected types; disallowing them for
> tasks would make tasks a second-class citizen."
> -- http://archive.adaic.com/standards/95lsn/LSN1044.TaskDisc.txt

.... OK, I looked it up, and indeed someone named Bob Duff wrote it.
That's me!  ;-)  Thanks for the link.

In this Language Study Note (LSN), I was arguing that task types should
be allowed to have discriminants.  (And indeed they can in Ada 95 and in
Ada.)

I also thought (and continue to think) that array types should be
allowed to have discriminants.  The quote above was a jab at people
who thought otherwise.  I lost that argument.

- Bob