Hi,
I've been meaning to try Racket for years, and finally got around to it
when I found myself wanting to program a presentation, rather than
laboriously copy lots of slides in a similar format.
I'm using Racket 6.1.1, and I'm pretty new to Scheme.
I'm trying to illustrate editing fixes in short samples of writing. The
following simple code works fine:
#lang slideshow
(require slideshow/step)
(void
(with-steps
(before after)
(slide
(lt-superimpose
((vonly before) (t "With"))
((vonly after) (t "By"))))))
First I see "With", then "By".
Since I have a lot of slides like this, I want to write a macro. I tried:
#lang slideshow
(require slideshow/step)
(define-syntax-rule (correct from to)
(lt-superimpose
((vonly before) (t from))
((vonly after) (t to))))
(void
(with-steps
(before after)
(slide
(correct "With" "By"))))
but I get the error:
vonly: unbound identifier in module in: vonly
I've experimented with various types of quoting and unquoting, and tried
define-simple-macro instead of define-syntax-rule, but I'm forced to admit
I don't know what I'm doing!
I know that vonly is special and is bound non-hygienically inside the scope
of the with-steps; how do I reference it correctly in a macro?
--
http://rrt.sc3d.org
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