Re: Generic Collection

[andrew <andrew.carroll@okstate.edu>]

On May 11, 4:28 pm, Georg Bauhaus <bauh...@futureapps.de> wrote:
> If you don't care that there is only one type of collection for
> all kinds of objects, then indeed references to DB_thing'class
> objects seem a plausible choice for storing table objects in
> collection. Where
>
>    type DB_thing is abstract tagged private;
>    type DB_thing_ref is access DB_thing'class;
>
>    type attribute is new DB_thing with private;
>    type tuple is new DB_thing with private;
>    ...
>
>    package DB_collections is new Containers.Hashed_Sets
>       (Element_Type => DB_thing_ref, ...);
>
>    subtype collection is DB_collections.Set;
I'm going to have to look at this more.  So far it looks promising.


> Is there really a sufficiently common algorithm for schemas,
> tables, tuples, and attributes?
add, remove, getnext, find, sort, search, etcetera.  So yeah, the
basic collection of things type of operations.


> > > > I don't understand why I would have run-time errors.  Please expand
> > > > that thought.
>
> > > Just think of the consequences of Java pre-1.5 collections delivering
> > > nothing but Object objects.
> > There was a problem with delivering objects of type Object?
>
> Yes, there was a problem with everything being of type Object.
> For example, retrieving references from collections forces
> type checking at run time and throwing ClassCastException
> when there is a mismatch.
>     some_ref = (IKnowWhatType) container.get(some_key);
> That is a reason why Java now has generics.
OOOHHHHH, that...shoot, you had me going there for a minute.  I
thought it was something _serious_ that somehow is related to a
problem that Ada would have.