Question

编写以下函数的惯用方法是什么？

(split-first #"." "abc.def.ghi") ;;=>["abc", "def.ghi"]
(split-last #"." "abc.def.ghi") ;;=>["abc.def", "ghi"]

使用split有一个明显的（丑陋？）解决方案，但我确定有更优雅的解决方案吗？也许使用正则表达式/ indexOf / split-with？

Answer 1

对于分裂优先，最好的方法是：

select title, cost, pageUrl
from products
where cost between 100 and 125
      and (title like '%something%' or pageUrl like '%something%');

split-last的一种方法是使用否定先行断言：

(defn split-first [re s]
  (clojure.string/split s re 2))

(split-first #"\." "abc.def.ghi") 
=> ["abc" "def.ghi"]

(split-first #"<>" "abc<>def<>ghi")
=> ["abc" "def<>ghi"]

Answer 2

如果你不一定需要正则表达式匹配，那么这将起作用：

(defn index-of
  [^String s c]
  (.indexOf s c))

(defn last-index-of
  [^String s c]
  (.lastIndexOf s c))

(defn split-at-index-fn
  [f c s]
  (let [i (f s c)]
    ; I do not know what you want returned if no match is found
    (when-not (neg? i)
      [(.substring s 0 i) (.substring s (inc i))])))

(def split-first
  (partial split-at-index-fn index-of))

(def split-last
  (partial split-at-index-fn last-index-of))

这不是很惯用，因为它主要只是Java互操作。

Clojure - 写分裂优先和分裂最后的惯用方法

2 个答案: