Re: A generic list package

[Florian Weimer <fw@deneb.enyo.de>]

Jeffrey Carter <jrcarter@acm.org> writes:

>> > I find it curious that you expect the client to provide the "next"
>> > field/operation, rather than declaring a Node_Type containing the
>> > user's type and a Next field. Can you elaborate on this?
>
> I would say that this approach does not qualify as an ADT. The client
> must understand the internal representation to be used in the list and
> declare a set of types and operations appropriately. That does not seem
> "abstract".

All the data types you can express in Ada cannot qualify as abstract
data types. ;-)

Ada can only provide implementations of abstract data types, and in
the implementation process, some abstraction is always lost.  However,
I agree that the Next_Of/Set_Next interface as at a very low
abstraction level, and it does not represent an implementation of the
usual 'list' ADT (but of another ADT).