[racket] Problem with macro

Hi all!
 
I want to create macro for creating a DFA automaton (similar to one described here: http://www.cs.brown.edu/~sk/Publications/Papers/Published/sk-automata-macros/paper.pdf )
 
My desire is that, for example, this form
 
(automaton init
   (init : (c -> more))
   (more : (a -> more)
           (d -> more)
           (r -> END)))
 
expands to:
 
(letrec ([curr-state empty]
           [init
            (lambda (symbol)
              (case symbol
                [(c) (set! curr-state more) 'ok]
                [else 'transition-error]))]
           [more
            (lambda (symbol)
              (case symbol
                [(a) (set! curr-state more) 'ok]
                [(d) (set! curr-state more) 'ok]
                [(r) (set! curr-state END) 'endstate]
                [else 'transition-error]))]
           [END
            (lambda (symbol)
              'reading-past-end-error)])
    (set! curr-state init)
    (lambda (c)
      (curr-state c))))
 
 
I've created the following two macros, but unfortunatelly they are wrong:
 
(define-syntax process-state
  (syntax-rules (: -> END)
    [(_ (label -> END))
     [(label) (set! curr-state END) 'endstate]]
    [(_ (label -> new-state))
     [(label) (set! curr-state new-state) 'ok]]))
 
 
(define-syntax automaton
  (syntax-rules (: -> END)
    [(_ init-state
        (state : transition ...)
        ...)
     (letrec ([curr-state empty]
              [state
               (lambda (symbol)
                 (case symbol
                   [(process-state transition)]
                   ...
                   [else 'transition-error]))]
              ...
              [END
               (lambda (symbol)
                 'reading-past-end-error)])
       (set! curr-state init-state)
       (lambda (c)
         (curr-state c)))]))
 
Reported error is: case: bad syntax (missing expression after datum sequence) in: ((process-state (c -> more)))
It seems to me that macro process-state is not expanding at all.
 
Can somebody tell me what's wrong and how to fix it???
 
Thanks in advance,
Racket Noob 		 	   		  
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