[plt-scheme] Problem with syntax-case macro under MzScheme 352

From: Sam Tobin-Hochstadt (samth at ccs.neu.edu)
Date: Sat Sep 9 13:58:29 EDT 2006

On Sat, 2006-09-09 at 09:34 -0500, Blake McBride wrote:
> Never mind, I figured it out.  The macro should have been:
> (define-syntax m4
>   (lambda (x)
>     (syntax-case x ()
>                  ((_ v)
>                   (with-syntax ((name (datum->syntax-object (syntax v)
> (string->symbol (string-append (symbol->string (syntax-object->datum
> (syntax v))) ":g")))))
>                                 (syntax (begin
>                                          (define name '())
>                                          (define v '()))))))))

How about the following:

(define-syntax (m4 stx)
   (define (symbol-append . args)
      (string->symbol (apply string-append (map symbol->string args))))
   (define (add-suffix stx suf)
      (datum->syntax-object stx (symbol-append (syntax-e stx) suf))))
   (syntax-case stx ()
      [(_ v) (with-syntax ([name (add-suffix #'v ':g)])
                 #'(begin (define name '())
                          (define v '())))]))

That seems simple enough, especially since `symbol-append' really ought
to be in a standard macro-writing library.  

And if you're having trouble debugging your macros, I recommend Ryan
Culpepper's excellent macro debugger, which is available in the nightly

sam th

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