[r6rs-discuss] [Formal] Trivial Enhancement of macros in v5.91: capture-syntax

[Abdulaziz Ghuloum]

On Nov 28, 2006, at 7:31 AM, Matthew Flatt wrote:

> Wrong. Your code works just fine with explicit phases.
>
> As is typical, no `for' declarations are necessary, mostly because
> `r6rs' exports into both run and expand phases

I apologize.  If you don't mind me asking, would these two phases be
distinct or the same?  (maybe it doesn't matter for this example, but
I still wonder.)

One more question if you don't mind, would the following work?  (maybe
you don't want it, but I was re-factoring it and realized I didn't want
to regenerate the transformers every time you enter a new [un]trace- 
region.
I'm curious.)

(library tracers-helpers
   (export print-args)
   (import r6rs)
   (define print-args
     (lambda (fml* act*)
       (display "Lambda ")
       (display fml*)
       (display " : ")
       (display act*)
       (newline))))

(library tracers
   (export trace-region untrace-region)
   (import r6rs r6rs::syntax-case tracers-helpers)
   (define trace-transformer
     (lambda (stx)
       (syntax-case stx ()
         [(_ fml* b b* ...)
          #'(lambda act*
              (print-args 'fml* act*)
              (apply (lambda fml* b b* ...) act*))])))
   (define-syntax trace-region
     (lambda (x)
       (syntax-case x ()
         [(kwd b b* ...)
          (with-syntax ([L (datum->syntax #'kwd 'lambda)])
            #'(let-syntax ([L trace-transformer])
                 b b* ...))])))
   (define untrace-transformer
     (lambda (stx)
       (syntax-case stx ()
         [(_ fml* b b* ...)
          #'(lambda fml* b b* ...)])))
   (define-syntax untrace-region
     (lambda (x)
       (syntax-case x ()
         [(kwd b b* ...)
          (with-syntax ([L (datum->syntax #'kwd 'lambda)])
            #'(let-syntax ([L untrace-transformer])
                 b b* ...))]))))

Aziz,,,