anchor.diff:            :parser #'chronicity:parse
             :default default
             :required-p required-p
  -          :if-invalid (or (parse-if-invalid if-invalid)
  +          :if-invalid (or (parse-if-invalid if-invalid error-color)
                             (lambda () (say "Error. Invalid timestamp"
                                             :color error-color)))
             :color color
  
positive.code:               :validator (or (and validator (clavier:&& (clavier:valid-email)
                                                          (make-validator validator)))
                               (clavier:valid-email))
                :if-invalid (or (parse-if-invalid if-invalid)
                                (lambda (&optional value)
                                  (declare (ignore value))
                                  (say "Invalid email" :color error-color)))
  
negative.code:             (prompt msg :default default
                          :required-p required-p
                          :validator (clavier:valid-url)
                          :if-invalid (or (parse-if-invalid if-invalid error-color)
                                          (lambda (&optional value)
                                            (say "Invalid url" :color error-color)))
                          :color color
  