[dmd-concurrency] shared arrays

[Steve Schveighoffer]

----- Original Message ----
> From: Andrei Alexandrescu <andrei at erdani.com>
> To: Discuss the concurrency model(s) for D <dmd-concurrency at puremagic.com>
> Sent: Thu, January 14, 2010 2:36:47 PM
> Subject: Re: [dmd-concurrency] shared arrays
> 
> Steve Schveighoffer wrote:
> > What about shared(T)[] where T.sizeof >= 2*(size_t.sizeof) ?  If copying an 
> array reference is unusable, then why is copying large array elements usable?  
> This whole point has confused me...
> > 
> > Should the runtime throw an exception when asked to copy such arrays?
> 
> It's a compile-time error. Assignment of shared values is defined only for types 
> up to word-size that don't define constructors. If this doesn't compile:
> 
> foreach (i; 0 .. a.length) b[i] = a[i];
> 
> then this shouldn't compile either:
> 
> b[] = a[];

or these?

b.dup;
T t;
b ~= t;
b ~= a;

But really, I don't understand why it's ok to copy i.e. a shared(char)[] where half of it might have changed, but it's not OK to copy an array of large types.

Does this also mean that shared(long) isn't usable?  Isn't that a bit limiting?

-Steve