clojure 尾递归中的 java.lang.StackOverflowError

发布于 2024-12-22 21:22:04 字数 432 浏览 0 评论 0原文

我遇到了以下代码的 StackOverflowError：

(defn recursive-reverse
  ([coll] (recursive-reverse [coll nil]))
  ([coll acc]
    (if (= coll '()) acc
        (recur (rest coll) (cons (first coll) acc)))))

尽管使用循环可以使其工作：

(defn recursive-reverse [lst]
  (loop [coll lst acc nil]
    (if (= coll '()) acc
        (recur (rest coll) (cons (first coll) acc)))))

没有循环的先前代码出了什么问题？

原文

I encountered the StackOverflowError for the following code:

(defn recursive-reverse
  ([coll] (recursive-reverse [coll nil]))
  ([coll acc]
    (if (= coll '()) acc
        (recur (rest coll) (cons (first coll) acc)))))

though using loop would make it work:

(defn recursive-reverse [lst]
  (loop [coll lst acc nil]
    (if (= coll '()) acc
        (recur (rest coll) (cons (first coll) acc)))))

What goes wrong with the prior code without loop?

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

淡淡绿茶香 2024-12-29 21:22:04

您的错误在这里：

([coll] (recursive-reverse [coll nil]))

您正在使用一个参数（一个向量）调用recursive-reverse。这会调用函数的相同参数列表，因此它会递归执行并每次都会创建一个堆栈帧。

将其更改为：

([coll] (recursive-reverse coll nil))

你应该是对的。

（另外，单独的问题，但我通常会检查 nil 而不是 '() 并使用 next 而不是 rest< /code>。我认为它在性能或其他方面没有任何真正的优势，但对我来说似乎更干净。）

Your bug is here:

([coll] (recursive-reverse [coll nil]))

You're calling recursive-reverse with one argument (a vector). This calls the same argument list of the function, so it does it recursively and creates a stack frame every time.

Change it to:

([coll] (recursive-reverse coll nil))

and you should be right.

(Also, separate issue, but I would generally do checking for nil rather than '() and using next rather than rest. I don't think it has any real advantage in terms of performance or anything, but it seems cleaner to me.)

回复收藏 0 原文

剪不断理还乱 2024-12-29 21:22:04

这对我有用：

(defn recursive-reverse
  ([coll] (recursive-reverse coll nil))
  ([coll acc]
    (if (= coll '()) acc
        (recur (rest coll) (cons (first coll) acc)))))

您将参数传递给了几个不必要的括号内的 recursive-reverse ，仅此而已。

This worked for me:

(defn recursive-reverse
  ([coll] (recursive-reverse coll nil))
  ([coll acc]
    (if (= coll '()) acc
        (recur (rest coll) (cons (first coll) acc)))))

You passed the arguments to recursive-reverse inside a couple of unnecessary brackets, that's all.

回复收藏 0 原文

~没有更多了~