Asumu,
Your lookup macro's output just tells whether there is a rename somewhere
between the binding for f and its original source binding. Rename
transformers get injected all over the place. To get the real story, turn
your lookup macro into a loop that chases the binding back to the source.
Or, use the macro stepper with hiding off. The let-syntax expression
expands into:
(letrec-syntaxes+values (((f1) (make-set!-transformer values))) ()
(letrec-syntaxes+values (((f) (values (make-rename-transformer
(quote-syntax f1) ()
(lookup f)))
That's where the rename comes from.
Carl Eastlund
On Fri, May 17, 2013 at 7:30 PM, Asumu Takikawa as...@ccs.neu.edu wrote:
Hi all,
I'm confused about an aspect of set! and rename transformers. I'll
explain with this example:
#lang racket
;; a macro that uses `syntax-local-value/immediate`
(define-syntax (lookup stx)
(syntax-case stx ()
[(_ id)
(let-values ([(f _) (syntax-local-value/immediate #'id)])
(displayln (rename-transformer? f))
(displayln (set!-transformer? f))
#'0)]))
;; f is a set!-transformer
(let-syntax ([f (make-set!-transformer values)])
(lookup f))
;; sanity check
(rename-transformer? (make-set!-transformer values))
In this example, `f` is bound to a set!-transformer. The macro `lookup`
will look up the value bound to `f` at compile-time, and I expected that
the result would be the set! transformer.
However, it seems like the set! transformer is somehow being turned into
a rename transformer (note the two print statements produce #t and #f
respectively). The last line suggests that set! transformers are not
actually a subtype of rename transformers though.
Am I confused about set! transformers or is there a bug here?
Cheers,
Asumu
_
Racket Developers list:
http://lists.racket-lang.org/dev
_
Racket Developers list:
http://lists.racket-lang.org/dev
