DDC compiler and effects; better than Haskell? (was Re: [Haskell-cafe] unsafeDestructiveAssign?)

Sebastian Sylvan sebastian.sylvan at gmail.com
Sat Aug 15 19:07:46 EDT 2009

On Sat, Aug 15, 2009 at 11:45 PM, John A. De Goes <john at n-brain.net> wrote:
> Effect system optimizations are about taking programs that are correct, and
> transforming them to faster but equivalent programs that are still correct.

And since reordering access to externally modifiable data (external includes
memory if it's visible to other therads) is *not* safe, that shouldn't be
done. You're arguing for doing unsafe (i.e. they can cause a functioning
program to become non-functioning) transformations!

That said, your reasoning precludes the use of file read buffering, and
> other similar operations that are routinely done. It's only an illusion that
> such programs are "safe", with or without transformation of sequential read
> operations.

Yes, you do have to be very careful about abstractions like that, but the
fact that we have some of that now, which can cause very hard-to-catch bugs
when you rely on ordering, is no good argument that we should add even more
of it!

Sebastian Sylvan
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