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