die roll parser with smug

gistfile1.lisp

(defun die-roll ()
  (=let* ((num-dice (=or (natural-number) (result 1)))
          (_ (=char #\d))
          (die-faces (natural-number)))
    (result (loop repeat num-dice
               summing (random die-faces)))))

(defun chained-roll ()
  (=let* ((first-roll (=or (die-roll)
                           (smug::sophisticated-int)))
          (other-rolls (zero-or-more
                        (=let* ((modifier (=or (=char #\-)
                                               (=char #\+)))
                                (value (=or (die-roll)
                                            (natural-number))))
                          (result (* value
                                     (case modifier
                                       (#\- -1)
                                       (#\+ 1))))))))
    (result (reduce #'+ other-rolls :initial-value first-roll))))