The racket-lexer function returns 5 values:
- Either a string containing the matching text or the eof object.
Block comments and specials currently return an empty string.
This may change in the future to other string or non-string data. 
- A symbol in '(error comment sexp-comment white-space constant string no-color parenthesis hash-colon-keyword symbol eof other). 
- A symbol in '(|(| |)| |[| |]| |{| |}|) or #f. 
- A number representing the starting position of the match (or #f if eof). 
- A number representing the ending position of the match (or #f if eof). 
Like 
racket-lexer, but uses the extended lexer protocol to
track and report regions that are commented out with 
#;.
Added in version 1.2 of package syntax-color-lib.
Like 
racket-lexer, but returns an extra value. The last
return value indicates whether the consumed token should count as a
datum, an opening parenthesis (or similar starting token to group
other tokens), a closing parenthesis (or similar), or a prefix (such
as whitespace) on a datum.
Added in version 1.2 of package syntax-color-lib.
Added in version 1.2 of package syntax-color-lib.