Re: New aggregates with Ada 2022.

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2022-06-29 06:07, Randy Brukardt wrote:
> What you say here is precisely how they should work. But you would make the
> cost of supporting that necessary on every array object, because one could
> not know when an array is passed as a parameter what sort of representation
> it has. So one has to use dispatching helper operations to implement all
> assignments. And that's way more expensive than traditional array
> implementation.

It is already there because Ada 83 arrays have definite and indefinite 
representations. Adding a user-defined representation on top is nothing.

> If you didn't have slices that could be passed as array parameters, then
> that problem does not exist. And I don't think slices are sufficiently
> worthwhile to force expensive, unoptimizable code.

You still must be able to pass a definite array for indefinite argument 
and conversely. Slices change nothing.

The language must expose subtype conversions per adding removing 
constraints to the user. This is what definite/indefinite and slicing 
does. But also, it is what the type tag could be for class-wide arrays 
or scalar types. I am talking about Integer'Class. And it is what 
measurement units constraints are.

There should be a universal mechanism of dealing with type constraints 
unifying discriminants/tags/bounds.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de