Re: XML DOM Binding for Ada 95 - matter of style

["Matthew Heaney" <matthewjheaney@earthlink.net>]

"Marin David Condic" <nobody@noplace.com> wrote in message
news:3F2A5303.6080902@noplace.com...
>
> IMHO, something like the DOM - an OOD expression of a desired
> functionality - is exactly the reason Ada invented tagged records.

The purpose of tagged records is to implement dynamic binding.

If the problem calls for dynamic binding, then maybe a tagged type is
appropriate (but maybe not).

If the problem does not require dynamic binding of operations, then you
probably don't need tagged types.

> To
> implement it with discriminated records (a feature I always found to
> have too many "gotchas!" built into it anyway) seems awkward and clumsy.
> If you don't think using tagged records to implement something like this
> design is appropriate, what are you saving them for? :-)

I have never had a problem with discriminated records, so I don't know what
"gotchas" you're referring to.

Tagged types are one tool among many.  Use them when they make sense.

It probably doesn't make sense to use a tagged type when there is no dynamic
binding.

Even when there is dynamic binding, using case statements or subprogram
pointers is often simpler.  It depends on the problem.

Note that the Charles library implements the full view of the container type
as tagged, but only to add controlledness to the type, so that memory
management is automatic.  The partial view of the type is not tagged, and
there is no dynamic binding.

http://home.earthlink.net/~matthewjheaney/charles/