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Support `module+` in Syndicate #langs. Closes #2. 

Adding `#'module+` explicitly to the stop-list for local-expand stops
the infinite recursion (problem 1 in the issue description). The code
goes on to treat it like `#'module` and `#'module+`, namely as a
non-action-producing form.

Problem 2 in the issue description is interesting. I haven't done
anything in particular to address the production of unbounded `X` ->
`(begin X)` expansions, but it seems not currently to be a problem;
and, weirdly (?), submodules in a `#lang syndicate` or `#lang
syndicate/actor` module do not seem to inherit the `#%module-begin` of
their container! That is, `(module+ main)`, `(module+ test)` etc. all
seem to have a `racket/base` `#%module-begin`, though I've not looked
very far into this.

Most peculiar on this front is that if the `#,@(reverse final-forms)`
precedes the `(module+ syndicate-main ...)`, and the module being
processed includes, say, a `(module+ main)`, then for some reason the
resulting `main` submodule *is* treated as having a `syndicate/lang`
`#%module-begin` (thus causing problems as suggested in the issue
description)! I *really* don't understand why that might be, and
haven't spent very much time investigating after I noticed that so
long as the `main`-required `syndicate-main` submodule preceded all
other submodule declarations, things seemed to work out.

This whole approach is still a bit dicey: for example, the following
will erroneously treat `(foo quux)` as an expression yielding actions,
rather than a struct declaration:

    #lang syndicate
    (define-syntax-rule (foo x) (struct x ()))
    (foo quux)
This commit is contained in:
Tony Garnock-Jones 2016-07-16 15:40:20 -04:00
parent 75cec37038
commit b6c679afa6
1 changed files with 4 additions and 4 deletions
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8
racket/syndicate/lang.rkt
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@ -39,8 +39,7 @@
(define (accumulate-actions action-ids final-forms forms)
(if (null? forms)
(let ((final-stx
#`(#%module-begin #,@(reverse final-forms)
(module+ syndicate-main
#`(#%module-begin (module+ syndicate-main
(provide boot-actions activate!)
(define activated? #f)
(define boot-actions (list #,@(reverse action-ids)))
@ -48,6 +47,7 @@
(when (not activated?)
(set! activated? #t)
boot-actions)))
#,@(reverse final-forms)
(module+ main
(require (submod ".." syndicate-main))
(run-ground (activate!))))))
@ -55,7 +55,7 @@
final-stx)
(syntax-case (local-expand (car forms)
'module
(kernel-form-identifier-list)) ()
(cons #'module+ (kernel-form-identifier-list))) ()
[(head rest ...)
(if (free-identifier=? #'head #'begin)
(accumulate-actions action-ids
@ -63,7 +63,7 @@
(append (syntax->list #'(rest ...)) (cdr forms)))
(if (ormap (lambda (i) (free-identifier=? #'head i))
(syntax->list #'(define-values define-syntaxes begin-for-syntax
module module*
module module* module+
#%module-begin
#%require #%provide)))
(accumulate-actions action-ids