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Sun Feb 4 22:48:32 GMT 2007

syntax transformation


1. one pattern i've been trying to solve is this

(definitions
	(some (special) structure here)
	(same (special) structure there))

it's easy enough to write the first transformation, but how do you do
the next one without having to explicitly recurse using names etc.. ?

in other words: "now just accept more of the same".
this seems to be the answer:

(define-syntax shift-to
  (syntax-rules ()
    ((shift-to (from0 from ...) (to0 to ...))
     (let ((tmp from0))
       (set! to from) ...
       (set! to0 tmp))    )))

one ellipsis in the pattern for every ellipsis on the same
level. or something like that.. need to explain better.


2. what's the real significance of the argument of syntax-rules ?

"Identifiers that appear in <literals> are interpreted as literal
identifiers to be matched against corresponding subforms of the
input."


3. how to get plain and ordinary s-exp macro transformers using
define-syntax?

i was thinking about something like this:

(define-syntax nofuss
  (syntax-rules ()
    ((_ (pat ...) expr)
     (lambda (stx)
       (match (syntax-object->datum stx)
              ((_ pat ...)
               (datum->syntax-object stx expr)))))))

(define-syntax snarf-lambda
  (nofuss (args fn)
          `(lambda (,@(reverse args) . stack)
             (cons (,fn ,@args) stack))))


but that doesnt work, since nofuss is not defined at expansion
time.. but it should work. there has to be some way of doing this.





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