(s-expression
 . (choice
    comment

    (comment "Expression is read in case-sensitive mode"
	     (seq "#cs" s-expression))
    (comment "Expression is read in case-insensitive mode"
	     (seq "#ci" s-expression))

    (comment "SRFI-10 constructor" (seq "#,(" symbol (zero-or-more expression) ")"))

    (comment "Improper list" (seq "(" (one-or-more s-expression) "." s-expression ")"))
    (comment "Proper list" (seq "(" (zero-or-more s-expression) ")"))
    (comment "Vector" (seq "#(" (zero-or-more s-expression) ")"))

    string

    shorthand

    keyword

    symbol

    (comment "Special EOF object" "#!eof")

    number
))

(comment
 . (choice
    (comment "Script marker comment"
	     (choice
	      (seq "#!/" (zero-or-more character) newline)
	      (seq "#!" whitespace (zero-or-more character) newline)))
    (comment "Multi-line block comment" (seq "#|" (zero-or-more character) "|#"))
    (comment "Expression comment" (seq "#;" s-expression))
    (comment "Traditional comment" (seq ";" (zero-or-more character) newline))

))

(string
 . (choice
    (comment "String" (seq "\"" (zero-or-more string-character) "\""))
    (comment "Multiline tagged string" (seq "#<<" symbol newline (zero-or-more character) symbol newline))
    (comment "Multiline tagged string\nAllows embedded #<expr> or #{<expr>}" (seq "#<#" symbol newline (zero-or-more character) symbol newline))))

(shorthand
 . (choice
    (comment "(cond-expand (<symbol> <s-expression>) (else))"
	     (seq "#+" symbol s-expression))
    (comment "(location <sexpr>)" (seq "#$" s-expression))
    (comment "(foreign-declare \"...\")"  (seq "#>" (zero-or-more string-character) "<#"))
    (comment "(quote <s-expression>" (seq "'" s-expression))
    (comment "(quasiquote <s-expression>" (seq "`" s-expression))
    (comment "(unquote <s-expression>" (seq "," s-expression))
    (comment "(unquote-splicing <s-expression>" (seq ",@" s-expression))
))

(keyword
 . (choice
    (seq ":" symbol)
    (seq "#:" symbol)
    (seq symbol ":")))

(symbol
 . (choice
    (seq "|" (one-or-more character) "|")
    (seq "#%" (one-or-more symbol-subsequent-character))
    (seq symbol-first-character (zero-or-more symbol-subsequent-character))
    "+"
    "-"
    "..."
    "#!optional"
    "#!rest"
    "#!key"))

(symbol-first-character . "[a-zA-Z!$%&*/:<=>^?_]")

(symbol-subsequent-character . (choice symbol-first-character "[0-9+-.@]"))