The next step is to distinguish between reading file A and reading
file B, between reading file A and writing file A, between reading one
part of file A and writing another part of file A, etc. When the
effect system can carry that kind of information, and not just for
files, but network, memory, etc., then you'll be able to do some
extremely powerful parallelization & optimization.
But for now providing course grained information on the class to which
an effect belongs is pretty interesting in its own right.
Regards,
John A. De Goes
N-Brain, Inc.
The Evolution of Collaboration
http://www.n-brain.net | 877-376-2724 x 101
On Aug 12, 2009, at 9:41 PM, Ben Lippmeier wrote:
Dan Doel wrote:
For instance: what effects does disciple support? Mutation and IO?
You can create your own top-level effects which interfere
will all others, for example:
effect !Network;
effect !File;
readFile :: String -(!e)> String
:- !e = !File
Now any function that calls readFile will also have a !File effect.
What if I want non-determinism, or continuations, etc.? How do I as
a user add those effects to the effect system, and specify how they
should interact with the other effects? As far as I know, there
aren't yet any provisions for this, so presumably you'll end up
with effect system for effects supported by the compiler, and
monads for effects you're writing yourself.
Yep.
In Disciple, a computation has an effect if its evaluation cannot
safely be reordered with others having the same effect. That is,
computations have effects if they might "interfere" with others.
One of the goals of the work has been to perform compiler
optimisations without having to use IO-monad style state threading.
"IO" is very coarse grained, and using the IO monad for everything
tends to introduce more data-dependencies than strictly needed, which
limits what optimisations you can do.
Non-determinism and continuations are tricker things than the simple
notion of "effects-as-interference", which I haven't got a good
solution for.
Ben.
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