string - 在 Clojure 中以函数式方式重写这个修剪函数

Question

我有这个功能(来自 program 的摘录)，我想以更具吸引力/功能性/惯用的方式重写。
它应该从 s 表达式中删除任何不必要的空格。

(defn trim 
  " Trim whitespace from code:
        (trim (trim \" d ' (    print   (   +   1   1 )  )\")
    ==> d '(print (+ 1 1))
    The replaced string is passed repeatedly to every call.
    Functional version
"
  [string] 
  (clojure.string/replace
   (clojure.string/replace
    (clojure.string/replace
     (clojure.string/replace
      (clojure.string/replace
       (clojure.string/replace
        (clojure.string/replace
         (clojure.string/replace
          (clojure.string/replace
           (clojure.string/replace
            string #"([^\\(\[{@~`'])(\(|\[|\{)" "$1 $2")
           #"(\)|\]|})(\[|\(|\{)" "$1 $2")
          #"[ \t]*(\)|\]|\})" "$1")
         #"[ \t]{2,}" " ")
        #"(\)|\]|\})[ \t]*(?=(\)|\]|\}))" "$1")
       #"(\(|\[|\{)[ \t]*(?=(\(|\[|\{))" "$1")
      #"^[ \t]*" "")
     #"(\\\{|\\\(|\\\[) " "$1  ")
    #"(\{|\(|\[) " "$1")
   #" ('|`) (\(|\[|\{)" " $1$2"))

我对它现在的样子不是很满意，因为乍一看很难弄清楚它是如何工作的(布局可能是问题所在)，如果我想添加它会带来问题更多正则表达式/替换。

这是另一个更友好(和命令式)并且有效但看起来平庸的版本:

(defn trim1 
  " Not so functional version"
  [raw-string]
  (def string (atom raw-string))
  (reset! string (clojure.string/replace @string #"([^\\(\[{@~`'])(\(|\[|\{)" "$1 $2"))
  (reset! string (clojure.string/replace @string #"(\)|\]|})(\[|\(|\{)" "$1 $2"))
  (reset! string (clojure.string/replace @string #"[ \t]*(\)|\]|\})" "$1"))
  (reset! string (clojure.string/replace @string #"[ \t]{2,}" " "))
  (reset! string (clojure.string/replace @string #"(\)|\]|\})[ \t]*(?=(\)|\]|\}))" "$1"))
  (reset! string (clojure.string/replace @string #"(\(|\[|\{)[ \t]*(?=(\(|\[|\{))" "$1"))
  (reset! string (clojure.string/replace @string #"^[ \t]*" ""))
  (reset! string (clojure.string/replace @string #"(\\\{|\\\(|\\\[) " "$1  "))
  (reset! string (clojure.string/replace @string #"(\{|\(|\[) " "$1"))
  (reset! string (clojure.string/replace @string #" ('|`) (\(|\[|\{)" " $1$2")))

我希望有一个看起来像这样的解决方案:

• 将正则表达式和替换存储在关联列表中:['(#"^[\t]*""")]
• 然后执行类似(reduce trim-fn replacement-list string)
的操作

reduce 部分如果可以实现的话会非常棒。但是，如果不可能，我会欢迎任何其他比这两个更好的解决方案。

Answer 1

(def trim-patterns 
  [[#"([^\\(\[{@~`'])(\(|\[|\{)" "$1 $2"]
   [#"(\)|\]|})(\[|\(|\{)" "$1 $2"]
   [#"[ \t]*(\)|\]|\})" "$1"]
   [#"[ \t]{2,}" " "]
   [#"(\)|\]|\})[ \t]*(?=(\)|\]|\}))" "$1"]
   [#"(\(|\[|\{)[ \t]*(?=(\(|\[|\{))" "$1"]
   [#"^[ \t]*" ""]
   [#"(\\\{|\\\(|\\\[) " "$1  "]
   [#"(\{|\(|\[) " "$1"]
   [#" ('|`) (\(|\[|\{)" " $1$2"]])

(defn trim
  [s]
  (reduce
    (fn [s [match replacement]]
      (clojure.string/replace s match replacement))
    s trim-patterns))