Thanks for the explanation. I think i understand now what i did wrong.
The 3D syntax was a good hint for further reading. I digged up a thread*
where you already had to explain it 10 years ago :)
Tobias
* http://www.cs.utah.edu/plt/mailarch/plt-scheme-2002/msg00111.html
On Thu, 26 Jul 2012 15:36:44 +0200, Matthew Flatt <mfl...@cs.utah.edu>
wrote:
I agree that it's a bug, in a sense, that your program runs even though
it cannot be compiled.
This is an example of "3-D syntax": you're embedding a value (i.e., an
instance of `s') that you can't write as a literal into the result of a
macro expansion. I think 3-D syntax probably should not be allowed, but
the macro system currently allows it.
Most likely, using 3-D syntax is a bad idea. It's possible that you
want to replace `#:transparent' with `#:prefab' in your example, since
a prefab structure can be written as a literal. More likely, I think
you want to generate an expression that constructs an `s' instead of
generating an `s' instance in the macro expansion.
At Thu, 26 Jul 2012 14:59:41 +0200, Tobias Hammer wrote:
Hi,
i have the following two files, one that only requires the other and
calls a macro and the other one that defines that macro:
=== main.rkt
#lang racket
(require "err.rkt")
(a)
=== err.rkt
#lang racket
(begin-for-syntax
(struct s (arg) #:transparent)
(define (fun arg)
(printf "arg: ~a\n" arg)))
(define-syntax (a stx)
(syntax-case stx ()
[(_)
(with-syntax ([v #`#,(s 123)])
#'(begin
(begin-for-syntax
(fun v))))]))
(provide a)
When executing 'racket main.rkt' directly i get the expected output
arg: #(struct:s 123)
but when i try to call 'raco make main.rkt' instead, i get this strange
error:
arg: #(struct:s 123)
write: cannot marshal value that is embedded in compiled code
value: (s 123)
context...:
/home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/cm.rkt:388:6
/home_local/hamm_to/racket/racket-5.3.0.16/collects/racket/private/more-scheme.r
kt:151:2:
call-with-break-parameterization
/home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/cm.rkt:188:5
/home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/cm.rkt:508:26
/home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/cm.rkt:501:42
/home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/cm.rkt:466:0:
maybe-compile-zo
/home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/cm.rkt:579:2:
do-check
/home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/cm.rkt:653:4
/home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/commands/make.rkt:7
7:8:
for-loop
/home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/commands/make.rkt:
[running body]
/home_local/hamm_to/racket/racket-5.3.0.16/collects/raco/raco.rkt:
[running body]
/home_local/hamm_to/racket/racket-5.3.0.16/collects/raco/main.rkt:
[running body]
I think i need a little help to understand what is happening here
and what i am doing wrong. I had expected that running and compiling
works on the same set of programs.
Thanks for any clarification.
Tobias
--
---------------------------------------------------------
Tobias Hammer
DLR / Institute of Robotics and Mechatronics
Tel.: 08153/28-1487
Mail: tobias.ham...@dlr.de
_________________________
Racket Developers list:
http://lists.racket-lang.org/dev
_________________________
Racket Developers list:
http://lists.racket-lang.org/dev
