Hi Noah,
Noah Lavine <[email protected]> writes:
> Perhaps this is obvious to everyone else, but it just occurred to me
> that (capture-local-environment) is just
> (call-with-current-continuation), but running in the environment of
> the evaluator instead of the program being evaluated. It's as though
> the evaluator was going to look in a tree for more code, but hit a
> special node and did a (call/cc). I hope other people find this
> interesting.
Ah yes, that's an excellent point!
In fact it makes me wonder whether `the-environment' and `local-eval'
could actually be implemented this way. I see some complications that
might make this strategy impractical or fragile, most notably that we
must be assured that the (call/cc) does not happen until
(the-environment) would have been _evaluated_, whereas the
expander/memoizer/evaluator will want to see what code is there _before_
evaluation. I'll have to think about this. There might be an easy and
robust way to do this, or maybe not.
Regardless, this is a great way to _think_ about these primitives in
terms that Schemers can understand, and maybe a selling point too. I
hope we can agree that first-class continuations are insanely great.
They carry a significant maintenance cost, but they also add great power
when they are needed. So why not first-class continuations for the
evaluator itself? :)
Thanks!
Mark
