Hello,
I am looking for some way to expand syntax (that is, without evaluation,
just syntax -> syntax transform) during another macro expansion (main-test.rkt
in the following example) using the foreign module namespace (need to use
prog and simple-act transformation rules from foreign modules).
I've managed to do the syntax expansion and evaluation with the desired
namespace, but have a hard time with expansion only.
*Expansion and evaluation sample (working):*
------------main-test.rkt------------
#lang racket
(require (for-syntax racket/base syntax/parse racket/syntax)
(for-syntax "foreign.rkt"))
(define-syntax (prog stx)
(syntax-parse stx
[(_ body ...)
(let ((x
(parameterize
([current-namespace (module->namespace "foreign.rkt")])
(eval stx))))
#'(begin body ...))
]))
(define-syntax (simple-act stx)
(syntax-parse stx
[(_ str)
#'(writeln str)
]))
(prog
(simple-act "foo")
(simple-act "bar"))
---------------------------------------
------------foreign.rkt----------------
#lang racket
(require (for-syntax racket/base syntax/parse racket/syntax))
(define-syntax (prog stx)
(syntax-parse stx
[(_ body ...)
#'(begin body ...)
]))
(define-syntax (simple-act stx)
(syntax-parse stx
[(_ str)
#'(writeln (format "foreign expansion: ~a" str))
]))
---------------------------------------
*Separate expansion (not working)*
*I have tried to do something like that:*
------------main-test.rkt--------------
#lang racket
(require (for-syntax racket/base syntax/parse racket/syntax)
(for-syntax "foreign-0.rkt")
(for-syntax "foreign-1.rkt"))
(define-syntax (prog stx)
(syntax-parse stx
[(_ body ...)
(let* ((expanded-by-foreign
(parameterize
([current-namespace (module->namespace "foreign-0.rkt")])
(expand-syntax stx)))* ;; Expect it to expand macros in
foreign-0.rkt, resuling syntax object is expanded later*
(result-of-evaluation
(parameterize
([current-namespace (module->namespace "foreign-1.rkt")])
(eval expanded-by-foreign)))) *;; It should expand with
foreign-1.rkt macros and evaluate expanded code*
#'(begin body ...))
]))
(define-syntax (simple-act stx)
(syntax-parse stx
[(_ str)
#'(writeln str)
]))
(prog
(simple-act "foo")
(simple-act "bar"))
-----------------------------------------
------------foreign-0.rkt----------------
#lang racket
(require (for-syntax racket/base syntax/parse racket/syntax))
(define-syntax (prog stx)
(syntax-parse stx
[(_ body ...)
#'(prog-0 body ...)
]))
(define-syntax (simple-act stx)
(syntax-parse stx
[(_ str)
#'(simple-act-0 str)
]))
-----------------------------------------
------------foreign-1.rkt----------------
#lang racket
(require (for-syntax racket/base syntax/parse racket/syntax))
(define-syntax (prog-0 stx)
(syntax-parse stx
[(_ body ...)
#'(begin body ...)
]))
(define-syntax (simple-act-0 stx)
(syntax-parse stx
[(_ str)
#'(writeln (format "foreign-0 evaluation: ~v" str))
]))
-----------------------------------------
Got an error: ../../../../../Applications/Racket
v7.1/collects/syntax/wrap-modbeg.rkt:46:4: prog: undefined;
cannot reference an identifier before its definition
I've tried to use a `local-expand` instead of `expand-syntax`, but
compilation is running out the memory then (looks like the infinite loop
while compilation, but I do not understand how to prevent it).
Best regards,
Ivan
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