用clojure中的定界符分割一个序列？

split a sequence by delimiter in clojure?

说我有一个Clojure序列，例如

1	'(1 2 3 6 7 8)

我想将其拆分，以便每当遇到一个可被3整除的元素时拆分列表，以便结果看起来像

1	'((1 2) (3) (6 7 8))

(编辑：我真正需要的是

1	[[1 2] [3] [6 7 8]]

，但我也将使用序列版本：)

在Clojure中执行此操作的最佳方法是什么？

partition-by没有帮助：

1 2	(partition-by #(= (rem % 3) 0) '(1 2 3 6 7 8)) ; => ((1 2) (3 6) (7 8))

split-with关闭：

1 2	(split-with #(not (= (rem % 3) 0)) '(1 2 3 6 7 8)) ; => [(1 2) (3 6 7 8)]

相关讨论

以及另一种基于还原的老派解决方案：

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user> (defn split-all [pred items]
(when (seq items)
(apply conj (reduce (fn [[acc curr] x]
(if (pred x)
[(conj acc curr) [x]]
[acc (conj curr x)]))
[[] []] items))))
#'user/split-all

user> (split-all #(zero? (rem % 3)) '(1 2 3 6 7 8 10 11 12))
;;=> [[1 2] [3] [6 7 8 10 11] [12]]

这是一个有趣的问题。我最近在图珀洛(Tupelo)库中添加了函数split-using，在这里看起来很合适。我在下面的代码中保留了spyx调试语句，以便您可以看到进展情况：

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(ns tst.clj.core
(:use clojure.test tupelo.test)
(:require
[tupelo.core :as t] ))
(t/refer-tupelo)

(defn start-segment? [vals]
(zero? (rem (first vals) 3)))

(defn partition-using [pred vals-in]
(loop [vals vals-in
result []]
(if (empty? vals)
result
(t/spy-let [
out-first (take 1 vals)
[out-rest unprocessed] (split-using pred (spyx (next vals)))
out-vals (glue out-first out-rest)
new-result (append result out-vals)]
(recur unprocessed new-result)))))

给我们的输出如下：

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out-first => (1)
(next vals) => (2 3 6 7 8)
[out-rest unprocessed] => [[2] (3 6 7 8)]
out-vals => [1 2]
new-result => [[1 2]]
out-first => (3)
(next vals) => (6 7 8)
[out-rest unprocessed] => [[] [6 7 8]]
out-vals => [3]
new-result => [[1 2] [3]]
out-first => (6)
(next vals) => (7 8)
[out-rest unprocessed] => [[7 8] ()]
out-vals => [6 7 8]
new-result => [[1 2] [3] [6 7 8]]

(partition-using start-segment? [1 2 3 6 7 8]) => [[1 2] [3] [6 7 8]]

或更大的输入向量：

1 2	(partition-using start-segment? [1 2 3 6 7 8 9 12 13 15 16 17 18 18 18 3 4 5]) => [[1 2] [3] [6 7 8] [9] [12 13] [15 16 17] [18] [18] [18] [3 4 5]]

您也可以使用嵌套的loop/recur创建解决方案，但是该解决方案已经在split-using函数中进行了编码：

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(defn split-using
"Splits a collection based on a predicate with a collection argument.
Finds the first index N such that (pred (drop N coll)) is true. Returns a length-2 vector
of [ (take N coll) (drop N coll) ]. If pred is never satisified, [ coll [] ] is returned."
[pred coll]
(loop [left []
right (vec coll)]
(if (or (empty? right) ; don't call pred if no more data
(pred right))
[left right]
(recur (append left (first right))
(rest right)))))

实际上，上述功能似乎将来会很有用。 partition-using现在已添加到Tupelo库中。