(define-syntax symbolic-accessor
  (syntax-rules ()
    ((_ (?var0 ?val0) ...)       
     (let* ((?var0 ?val0) ...)
       (call/cc (lambda (yield)
         (yield (lambda (p)
           (cond ((eq? p '?var0) ?val0) 
                  ...
                  (else (error "input not found")))))))))))