(
     (rule rulelist (plus (alt rule (seq (star c_wsp) c_nl))))
     (rule rule (seq rulename defined_as elements c_nl))
     (rule elements (seq alternation (star c_wsp)))
     (rule alternation
      (seq concatenation (star (seq (star c_wsp) "/" (star c_wsp) concatenation))))
     (rule concatenation (seq repetition (star (seq (plus c_wsp) repetition))))
     (rule repetition (seq (opt repeat) element))
     (rule repeat (alt (seq (star DIGIT) "*" (star DIGIT)) (plus DIGIT)))
     (rule element (alt rulename group option char_val num_val prose_val))
     (rule group (seq "(" (star c_wsp) alternation (star c_wsp) ")"))
     (rule option (seq "[" (star c_wsp) alternation (star c_wsp) "]"))
     (rule char_val (alt case_insensitive_string case_sensitive_string))
     (rule case_insensitive_string (seq (opt "%i") quoted_string))
     (rule case_sensitive_string (seq "%s" quoted_string))
     (rule num_val (seq "%" (alt bin_val dec_val hex_val)))
     (terminals _terminals (seq))
     (terminal rulename (seq ALPHA (star (alt ALPHA DIGIT "-"))))
     (terminal defined_as (seq (star c_wsp) (alt "=" "=/") (star c_wsp)))
     (terminal c_wsp (alt WSP (seq c_nl WSP)))
     (terminal c_nl (alt COMMENT CRLF))
     (terminal comment (seq ";" (star (alt WSP VCHAR)) CRLF))
     (terminal quoted_string (seq DQUOTE (star (range "#x20-#x21#x23-#x7E")) DQUOTE))
     (terminal bin_val (seq "b" (plus BIT) (opt (alt (plus (seq "." (plus BIT))) (seq "-" (plus BIT))))))
     (terminal dec_val
      (seq "d" (plus DIGIT) (opt (alt (plus (seq "." (plus DIGIT))) (seq "-" (plus DIGIT))))))
     (terminal hex_val
      (seq "x" (plus HEXDIG) (opt (alt (plus (seq "." (plus HEXDIG))) (seq "-" (plus HEXDIG))))))
     (terminal prose_val (seq "<" (star (range "#x20-#x3D#x3F-#x7E")) ">"))
     (terminal ALPHA (range "#x41-#x5A#x61-#x7A"))
     (terminal BIT (alt '0' '1'))
     (terminal CHAR (range "#x01-#x7F"))
     (terminal CR (hex "#x0D"))
     (terminal CRLF (seq (opt CR) LF))
     (terminal CTL (alt (range "#x00-#x1F") (hex "#x7F")))
     (terminal DIGIT (range "#x30-#x39"))
     (terminal DQUOTE (hex "#x22"))
     (terminal HEXDIG (alt DIGIT "A" "B" "C" "D" "E" "F"))
     (terminal HTAB (hex "#x09"))
     (terminal LF (hex "#x0A"))
     (terminal LWSP (star (alt WSP (seq CRLF WSP))))
     (terminal OCTET (range "#x00-#xFF"))
     (terminal SP (hex "#x20"))
     (terminal VCHAR (range "#x21-#x7E"))
     (terminal WSP (alt SP HTAB)))