important news: refocusing discussion

[Ross Paterson]

On Sat, Mar 25, 2006 at 05:31:04PM -0800, isaac jones wrote:
> I have no idea if it would work, but one solution that Simon didn't
> mention in his enumeration (below) is that we could find a group of
> people willing to work hard to implement concurrency in Hugs, for
> example, under Ross's direction.

I'm no expert on Hugs internals, and certainly not qualified to direct
such an effort, but I don't have great hopes for it.  Apart from the
fact that Hugs is written in a legacy language and uses a quite a bit
of global state, it also makes heavy use of the C stack, and any
implementation that does that will have trouble, I think.

I think it's clear that the proposed concurrency model is feasible for
some implementations but not for others.

I've been assuming that Haskell' was intended to encompass a wide range
of implementations.  If that's the case, the key point is that a Haskell'
module that does not use concurrency, but is thread-safe, ought to work
with non-concurrent implementations too.

To make that work, we'd need two interfaces:
 * one for applications that make use of concurrency.  This would be
   unavailable on some implementations.
 * one for thread-safe use of state.  This would be available on all
   implementations, and authors not requiring concurrency would be
   encouraged to use it for maximum portability.