Sharing in D

[Sean Kelly]

== Quote from downs (default_357-line at yahoo.de)'s article
> superdan wrote:
> > Walter Bright Wrote:
> >
> >> Jason House wrote:
> >>> Walter Bright Wrote:
> >>>
> >>>> http://www.reddit.com/comments/6u7k0/sharing_in_d/
> >>> This is one of my 3 big wishes for the D language.
> >>>
> >>> The artical talks about shared being transitive just like
> >>> const/invariant. I certainly hope it's more like pure than transitive
> >>> invariant.
> >> Pure doesn't apply to data types, it applies to functions. I don't know
> >> what you mean.
> >
> > looks 2 me more like more of the confusion in yesterthread.
> >
> >>> Allowing access to thread-local globals is a bad idea.
> >> Why? Global thread local storage is even enshrined into C++0x.
> >
> > 99% of the global shit i ever defined i wanted to be thread local. i had to
take special measures to make it so.
> >
> > dealing with globals in one thread is shitty to boot. using globals to
communicate across threads is sheer suicide.
> What about cases that depend on external resources, like a global buffer object
for HTTP downloads?
> In that case you want cached results to be available to as many threads as
possible, especially if the respective server has a high latency.

Yup.  This is pretty much the only time I use globals in my apps--
if there's some huge data structure I want to reference in all my
threads.  A user list... something like that.  In a language like
Erlang, that user list would probably be managed by a distinct
process and would serve requests from other processes that wanted
to perform operations on it.  Without shared data in D I'd do
pretty much the same thing.  All D would need is a solid messaging
system.  libd has one built-in, but we avoided this with Tango
because it would effectively change the language.


Sean