[plt-scheme] Nested macros and (... ...)

Hi all,

I came across this nested macro expression, found at
http://fabiokung.com/2007/10/24/ruby-dsl-to-describe-automata/ :

(define-syntax automaton (syntax-rules (:)
  [(_ init-state
      [state : response ...]
      ...)
    (let-syntax ([process-state (syntax-rules (-> accept)
                    [(_ accept)
                      (lambda (stream)
                        (cond [(null? stream) #t]
                              [else #f]))]
                    [(_ (label -> target) (... ...))
                      (lambda (stream)
                        (cond [(null? stream) #f]
                              [else (case (car stream)
                                      [(label) (target (cdr stream))]
                                      (... ...)
                                      [else #f])]))])])
      (letrec ([state (process-state response ...)]
               ...)
        init-state))]))

(define cdar-sequence?
  (automaton init
             [init : (c -> more)]
             [more : (a -> more)
                     (d -> more)
                     (r -> end)]
             [end : accept]))

(cdar-sequence? '(c a d a d r)) ; => #t
(cdar-sequence? '(a c a d r c)) ; => #f

Am I right in thinking that (... ...) is a way of placing a literal ... in
the expansion without it being treated as a repetition pattern by the first
expansion?


-- 
James Coglan
http://github.com/jcoglan/heist
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