effects in scheme

effect.scm

(define string-parser
  (let* ((escaped-char (effect (run parse-char #\\)
                               (run any-char)))
         (string-char (alternative (none-of '(#\" #\\))
                                   escaped-char))
         (parse-quote (parse-char #\")))
    (effect
     (let* ((_ (run parse-quote))
            (chars (run many string-char))
            (_ (run parse-quote)))
       (apply string chars)))))