(define-syntax defrec
  (syntax-rules ()
    ((_ rec-name fields ...)
     (define (rec-name fields ...)
       (case-lambda
         [(slot)
          (case slot
            [(fields) fields] ...
            [else (error 'rec-name "Unrecognized field" slot)])]
         [(slot value)
          (case slot
            [(fields) (set! fields value)] ...
            [else (error 'rec-name "Unrecognized field" slot)])])))))