On 09/30/2015 07:55 AM, Matthew Flatt wrote:
I'm fixing a bug in the implementation's handling of use-site scopes,
and that makes your example above work correctly. The bug is a holdover
from an earlier, broken idea of how to handle use-site scopes. Getting
rid of it --- bringing the implementation in line with the paper ---
solves the problem while the core test suite still passes and the main
distribution builds.
Thanks!
I think the examples in the paper are still correct, and it's still the
case that
(let ()
(def-m m x)
(m))
resolves the ambiguity. However, with the repaired expander, it's also
the case that
(def-m m x)
(let ()
(m))
resolves the ambiguity, in contrast to my earlier response. The
ambiguity depends (as originally intended) on a single definition
context shared by `def-m`, `m`, and `given-x`.
This makes sense to me now.
Similarly, it's still the case that
(define x 'outer)
(define-syntax-rule (def-m m given-x)
(define-syntax-rule (m)
(begin
(define given-x 'inner)
x)))
(def-m m x)
(m)
produces 'inner with the new expander and 'outer with the old one.
Again, though, the result is 'outer when adding a `(let () ....)`
around the last two lines, around just the `(m)`, or in place of the
`(begin ....)` within the definition of `m` --- any of which introduces
a more nested context for the definition of `given-x`.
I've gone back and forth on this a few times in my head, but I think
I've settled on believing that this makes sense. I will give tomorrow's
snapshot a try and see if my current mental model matches reality.
--
Brian Mastenbrook
[email protected]
https://brian.mastenbrook.net/
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