Re: containers and garbage collections.

[Stephen Leake <Stephe.Leake@nasa.gov>]

Martin Krischik <krischik@users.sourceforge.net> writes:

> Hello,
> 
> with this article I want to bring two of my discussions together.
> 
> On one side I am avocating garbage collection and one argument against it is
> that proper container library will make garbage collection unneccesary.

I agree; proper containers (and other algorithms) make garbage
collection unnecessary.

> One the other side I am avocating a more complete container librarys
> and one argument against it is that one can allways use access
> types.

Well, one can always use assembly language, too. Containers are an
excellent replacement for access types.

> Without garbage collection access types are pain in the bud. 

Hmm. I guess I can agree with that. But garbage collection is a "pain
in the bud" also; you can't use Finalization for good stuff, you can't
predict when the garbage will be collected. I far prefer containers.

> And when the container library only stores "type element is
> private;" than one need to use access types as element.

Yes.

> I have proven that both options are possible

I'm not sure which options you mean by "both options".

> I have implemented a garbage collected storrage pool for GNAT.

That's nice, and I hope you had fun doing it :).

> I also have created containers for "type Element (<>) is abstract
> tagged private;" 

Good. I'll have to look at it and compare it to SAL
(http://www.toadmail.com/~ada_wizard/), which provides similar
containers. 

> and I belive "type Element is array (Index range <>) of Item;" is
> possible as well (Enabling collection of Strings). 

Yes; SAL containers can hold Ada strings, with appropriate storage
management. 

Do either of your containers rely on the garbage collected storage
pool?

> Both can't be done with C++ templates - so we should not take the
> all mighty STL as an example.

Hmm. I haven't really looked, but I'd be very surprised if an STL
container can't contain STL Strings.

Of course, there is no such thing as "indefinite abstract tagged
private" in C++. The closest thing is a class with only pure virtual
member functions; that leaves out the "indefinite" part (implied by
the (<>)). So to say "STL" can't do that isn't saying much; you're
really just saying "C++ can't do that".

I'm not clear what you mean by "don't take the STL as an example".
Clearly the STL is limited by the expressiveness of C++; Ada is
better. But the STL has proven to be a very useful library, because of
the functionality it provides; it is reasonable to design an Ada
library that has similar functionality, but takes full advantage of
Ada to do it. I think that is your real goal?

-- 
-- Stephe