Re: Behavior of Stream Attributes On Access Types.

["Marin David Condic" <dont.bother.mcondic.auntie.spam@[acm.org>]

"Ted Dennison" <dennison@telepath.com> wrote in message
news:4519e058.0206110547.526d2369@posting.google.com...
> "Marin David Condic" <dont.bother.mcondic.auntie.spam@[acm.org> wrote in
message news:<ae2v7f$r12$1@nh.pace.co.uk>...
> > My inclination is to think that the sensible thing would be to call the
> > 'Read or 'Write for the thing pointed to by the access type, but this
has
>
> You can pretty much count on it *not* doing that. For instance, what
> would happen in that case with a circularly-referenced structure like
> a doubly-linked list?
>
Giving it a few minutes of thought after I posted, this case occurred to me.
Initially, I was thinking about what would make sense and certainly storing
the access value is of minimal use the instant it goes out to a file or down
a wire. Hence, I thought, "Well maybe it should store the object pointed
to..." But clearly, as you point out, its an interesting opportunity to
create infinite recursion.


>
> > implications for dynamically allocated objects. Will it write/read a
> > (totally useless) access value?
>
> Pretty much. It isn't *totally* useless. It will work just fine within
> the same execution (assuming you don't deallocate the memory).
> However, it is next to useless.
>
Yeah, I just can't think of many cases where I want to write something into
a stream and not have it persist across executions or partitions or
whatever, wherein the address starts becoming a totally useless piece of
information. In the same execution? Why wouldn't I just keep referencing the
data structure I've already got? I suppose the language needs to do
*something* if it encounters an access type going into or out of a stream,
but its hard to imagine how one might make use of it.


> If you want better behavior, its up to you to override 'Write and
> 'Read for your pointer type. Then you can code it to handle things
> like circular references and deallocating the target's old value on a
> 'Read.
>
>
Basically, that's been the story. I was just wondering what the ARM had to
say about the default case & couldn't spot something explicit enough to
clear through the fog. Thanks for the help.

MDC
--
Marin David Condic
Senior Software Engineer
Pace Micro Technology Americas    www.pacemicro.com
Enabling the digital revolution
e-Mail:    marin.condic@pacemicro.com