cond-expand does not isolate code at expansion time

[Marie-Joseph]

cond-expand does not isolate code at expansion time

[mnieper]

cond-expand is evaluated during expansion time, which happens after reading. Any R7RS implementation is free to reject the code posted in the beginning. The correct way is to use include in the cond-expand branch. The file which include references won't be read if that cond-expand branch is not evaluated.

[ashinn]

Yes, this is working as expected. To be able to process the cond-expand form we need to be able to read it first, and the #: syntax is not valid R7RS. include allows you to conditionally load code with non-portable read syntax.

Alternatively, use a separate module file for Guile.

• R7RS library polyglot.sld

(define-library (polyglot)
  (import (scheme base)
          (scheme write))
  (include "polyglot-impl.scm")
  (export test))

• Guile library polyglot.scm (or R6RS library polyglot.sls)

(define-module (polyglot)
          #:export (test))
(include-from-path "polyglot-impl.scm")

• Implementation polyglot-impl.scm

(define (test)
  (display "Worked")
  (newline))

[Marie-Joseph]

fwiw the workaround to this issue is to use R7RS-style library definitions even within the Guile branch. Guile accepts this just fine. However, this still feels like it shouldn't be necessary.

(and from the Guile side, Guile should accept .sld files by default but doesn't without the right flags, so you have to have a library/module definition at the top of the .scm file anyway. just so y'all know I'm not picking on Chibi ;) )

[Marie-Joseph]

Thanks for the guidance!