Re: Getting the index for an element in mutually referencing containers

[Mart van de Wege <mvdwege@gmail.com>]

"Randy Brukardt" <randy@rrsoftware.com> writes:

> "Mart van de Wege" <mvdwege@gmail.com> wrote in message 
> news:86wpbxneuz.fsf@gaheris.avalon.lan...
>> Simon Wright <simon@pushface.org> writes:
> ...
>>> But, I really think you're going to need to use access types here. A
>>> Person is a unique object, and should only exist once in your data
>>> structures. A Child should hold references to its Parent(s) and vice
>>> versa; if a Child holds *copies* of its Parents, what happens when you
>>> change the Parent's data in one place? how are you going to find all the
>>> copies and change all of them?
>>>
>> That was what I was afraid of. I like the way Ada usually takes care of
>> this for you, but I've been trying to work it out during downtime today
>> at work, and I'm afraid it's indeed time to grab the access types out of
>> the toolbox.
>
> The trick in such cases is to have a global "person" vector, which contains 
> all of the actual Person objects. Then use the cursors into that array in 
> your other data structures. That's gives the needed level of indirection 
> without involving any actual access types (meaning that you let Ada do the 
> storage management, and depending on your container implementation, also 
> reduce/eliminate the danger of dangling access types).
>
Hmm. Given that any roleplaying *campaign*, let alone a single session,
will not have a lot of characters to make that a memory issue, and that
characters are global to the campaign anyway, that makes a good deal of
sense.

Mart

-- 
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