Post by Lizzie Crowdagger in Hoot example project

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Hey!

I'm struggling using conditional expand with guile hoot. E.g., I want to have a "message" function display stuff either to terminal (when called there) or to a HTML element (when called in wasm).

I tried something like:

(cond-expand
 (hoot 
  (define-module (ui ui)
    #:use-module (web dom)
    #:export (message)))
 (else
  (define-module (ui ui)
    #:export (message))))
(cond-expand
 (hoot
  (define (message msg)
    "Display a text message"
    (append-child! (document-body) (make-text-node msg))))
 (else
  (define (message msg)
    "Display a text message"
    (display msg)
    (newline))))
(message "Foo")

This works when called in normal guile, but not when trying to build wasm ("hoot/library-group.scm:604:5: In procedure parse-library:invalid module forms (lot of stuff)")

I'd be really thankful if I could have any pointer on the way to do that cleanly :)

(Thought in any case given the deadline I'm afraid I won't be able to send more than a hello world to this jam 😭 )

David Thompson140 days ago

You can't cond-expand a module definition because you need the module definition in order to know what names are imported, including cond-expand. Rather than wrapping define-module in cond-expand, you need an inner cond-expand. Unfortunately, Guile's define-module doesn't support a cond-expand form. Fortunately, R7RS's define-library does! So, you'd want to do something like this:

(define-library
  (cond-expand
    (hoot (import (web dom)))
    (else))
  (export message)
  ...)

Lizzie Crowdagger140 days ago

Thanks a lot!

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