[plt-scheme] Macro expanding into define-values/invoke-unit?

From: Chongkai Zhu (czhu at cs.utah.edu)
Date: Sun Jul 12 20:52:47 EDT 2009

This is because of hygiene and the way define-values/invoke-unit 
introduces bindings (it inherits the lexical information of either 
itself or it's arguments).

I don't have time to look into the way define-values/invoke-unit expands 
now, but a quick solution works:

#lang scheme

(define-signature foo^ (bar))

(define-unit [email protected]
  (import)
  (export foo^)
  (define (bar x) (* x x)))

(define-syntax (mkfoo stx)
  (syntax-case stx ()
    [(_ x)
     (datum->syntax #'x
                    `(define-values/invoke-unit ,#'x (import) (export 
foo^)))]))

(mkfoo [email protected])

(bar 3)

-
Chongkai


Anthony Cowley wrote:
> How can I get a macro to expand into a (define-values/invoke-unit ...)
> form? That is, I have a macro that constructs syntax that looks
> correct, but is left unexpanded before the rest of the module
> containing my macro invocation is expanded. I think the below
> demonstrates the issue. When run, the module produces the value 9, but
> if the "Works!" line is commented out, while the following line is
> uncommented, then "bar" is an unbound identifier. In my case, my macro
> lives in another module, so if there are some phase gymnastics needed,
> that would be fine, but I haven't been able to discover them yet.
>
> Thanks,
> Anthony
>
> #lang scheme
>
> (define-signature foo^ (bar))
>
> (define-unit [email protected]
>   (import)
>   (export foo^)
>   (define (bar x) (* x x)))
>
> (define-syntax mkfoo
>   (syntax-rules ()
>     [(_ x) (define-values/invoke-unit x (import) (export foo^))]))
>
>
> (define-values/invoke-unit [email protected] (import) (export foo^)) ; Works!
> ;(mkfoo [email protected]) ; Doesn't work!
>
> (bar 3)
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