If Scheme is so good why MIT drops it?

Carl Banks pavlovevidence at gmail.com
Thu Jul 23 23:11:23 EDT 2009

On Jul 23, 4:57 pm, Paul Rubin <http://phr...@NOSPAM.invalid> wrote:
> Carl Banks <pavlovevide... at gmail.com> writes:
> > > I don't think the concept of "drivers" applies to user-mode programs.
> > > For FFI calls you would use an OS thread.
> > That's contrary to the hypothesis, isn't it?
> Yeah, it would have been better to say, green threads are ok for most
> typical forms of i/o concurrency, but OS threads are still necessary
> for some things.  An FFI call in particular isn't exactly under the
> control of your language's runtime system; it has to be treated
> more like an external program.
> OS thread switching is much more expensive than green thread
> switching, so it's still preferable to use green threads when
> possible.

That is reasonable.  Thank you.

> > And Paul, if I'm being a little hard on you here, it's not that I'm
> > taking issue with your own claim so much as with your dismissal of
> > mine.
> Well, the issue was why Python uses native threads pervasively.  As
> far as I can tell, it's just an implementation artifact that has no
> really compelling justification.

Probably for this reason: "Because then they didn't have to arrange
for the I/O to never block."

Carl Banks

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