优化Lisp递归随机游走

Question

这个函数导致堆栈溢出超过大约2000步，有没有什么方法可以轻松优化它以减少内存使用？

(defun randomwalk (steps state)
(displaystate state)
(if (equal steps 0) nil
        (if (solved? state) t
            (let ((nrmlstate (normalize state)))
                (randomwalk (- steps 1) (applymove nrmlstate (nth (random 
(length (getallmoves nrmlstate))) (getallmoves nrmlstate))))
            )
        )
    )
)

Answer 1

看起来你只能在尾部位置调用，这意味着你可以轻松地将其重写为完全没有递归：

(defun randomwalk (steps state)
  (loop :if (= steps 0)     
            :do (return nil)
        :if (solved? state) 
            :do (return t)
        :else
            :do (let* ((nrmlstate (normalize state))
                       (moves (getallmoves nrmlstate))
                       (random-move (nth (random (length moves)) moves)))
                  (setf state (applymove nrmlstate random-move))
                  (decf steps))))

由于我没有您使用的功能，除了基本情况之外，我还无法测试它。