Re: New aggregates with Ada 2022.

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

On 2022-06-30 07:03, Randy Brukardt wrote:
> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message
> news:t9h4i9$118a$1@gioia.aioe.org...
> ...
>>> A language that provided direct support for these abstractions should not
>>> need to provide arrays.
>>
>> Which is of course impossible considering the variety of maps (e.g. graph
>> is a map etc) and all problem-space specific.
> 
> Nobody uses arrays to implement graphs anyway.

It depends on the type of graph and operations on it, high-connectivity 
graphs (incidence matrix) or b-trees (blocks) certainly would use arrays.

> That's something you do when
> you are using a language like Fortran 66 that doesn't have any abstractions.

But that is unrelated to abstraction. FORTRAN had no access types 
therefore memory management of graph nodes was user-implemented on top 
of large arrays with the array index playing the role of a pointer to 
the node.

Even if FORTRAN had abstract data types, in order to implement a graph 
datatype you would still have to resort to arrays. It is just different 
things: abstraction does not mean you have it implemented and 
conversely. In Ada we have array implementation, but very limited 
abstraction of:

1. formal generic arrays
2. definite/indefinite unification

Index and aggregate hacks in no way support or extend the abstraction as 
the OP noticed.

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