Re: Containers - nontrivial element access

[Matthew Heaney <mheaney@on2.com>]

On Oct 1, 7:52 pm, "Alex R. Mosteo" <devn...@mailinator.com> wrote:
>
> I don't think that's reproducible as-is with the standard containers. It
> must be more verbose. There's no way to get a reference to the element in
> the Ada containers (unless you want to go the 'Unrestricted_Access way
> inside Update_Element, but that would require anyway extending the standard
> containers), so you can have dangling cursors but no dangling pointers.

If this is a vector, you can use index values.


> There was a recent thread (started by myself) on the amount of copying
> involved in the use of the containers. Someone said that returning accesses
> was deemed too unsafe and thus dropped, IIRC. I have not a strong position
> on if dangling cursors is a great improvement over dangling accesses, given
> what we gain/lose; in my experience a dangling cursor has been always as
> bad as a dangling pointer, in the sense that the program was erroneous
> beyond recovery; admittedly I have never got a memory violation using the
> containers so post-hoc diagnostics are quicker.

If you're using GNAT, then compile the container instantiations with -
gnata, and the container will detect dangling cursors.  Try it!