Abdulaziz Ghuloum wrote:
#|1|# (define VAR (MAC))
#|2|# (set! VAR (MAC))
#|3|# (list (MAC))
#|4|# (MAC)
#|5|# (define VAR (lambda () (MAC)))
#|6|# (set! VAR (lambda () (MAC)))
#|7|# (define-syntax MAC ...)
So, your proposal makes #1 invalid (currently valid) and makes #6 valid
(currently invalid).
Correct.
* There are also anomalies with expanding top-level forms. In
the above example, the expansion of MAC is deferred in #1, #2, #3,
but not #4. This could lead to subtle differences. In my proposal
all of these would be expanded eagerly, which removes surprises.
I don't see the surprise since MAC can expand to other top-level
definitions or other top-level macro definitions which are needed to
continue the expansion of the remaining forms.
But that is an "implementation reason". *We* understand we it is so,
and *once explained* it makes sense. But it is still an inconsistency
and wart, which my proposal avoids.
What's so special about expanding a lambda anyways? What about
case-lambda,
delay, forms that expand to some occurrence of lambda (e.g. let, cond,
etc.),
lambdas embedded in other expressions, e.g. (cons (lambda () (MAC)) 12),
etc.? What does your proposal say about these?
I believe there are all derived forms, defined in terms of lambda.
(Or at least they can be, and were in R5RS.)
Last I checked, the spec does not say anything about a repl, so you're free
to do as you please in your repl implementation. I don't see why the
report
should try to provide better support for things not in the report to begin
with.
Others have made this argument, and it seems wrong-headed to me: Most
Scheme implementations have a REPL, and I expect this will remain the
case, even after they implement R6RS. I.e. most implementations of
R6RS will have REPLs, and thus a specification of R6RS that
"plays better" with REPLs is more useful in the real world.
--
--Per Bothner
[EMAIL PROTECTED] http://per.bothner.com/
_______________________________________________
r6rs-discuss mailing list
[email protected]
http://lists.r6rs.org/cgi-bin/mailman/listinfo/r6rs-discuss
