Clojure-适用于除第n个元素以外的所有元素

我有一个向量，看起来像：

[ "1" "2" "3" "4" ]

我希望编写一个函数，将向量返回到：

[ 1 "2" 3 4 ]
; Note that the second element is still a string

---

请注意，没有任何更改，将返回一个全新的向量。在clojure中最简单的方法是什么？

映射索引是一个不错的选择。调用传递的函数，其中包含来自输入的某个项的值以及找到该项的索引（索引优先）。该函数可以选择生成新值或返回现有值

user> (map-indexed (fn [i v]
                     (if-not (= 1 i)
                       (Integer/parseInt v)
                       v))
                   [ "1" "2" "3" "4"])
(1 "2" 3 4)

当

if

返回v时，它在结果映射中的值完全相同，因此您可以在选择保留的零件中保留结构共享的好处。如果希望输出保持为向量，则可以使用mapv并自行传递索引序列

user> (mapv (fn [i v]
              (if-not (= 1 i)
                (Integer/parseInt v)
                v))
            (range)
            [ "1" "2" "3" "4"])
[1 "2" 3 4]

---

写这篇文章有很多方法，下面是我的方法。请注意，索引是以零为基础的：

(defn map-not-nth 
  "Transform all elements of coll except the one corresponding to idx (zero-based)."
  [func coll idx]   
  {:pre  [ (<= 0 idx (count coll)) ]
   :post [ (= (count %) (count coll)) 
           (= (nth coll idx) (nth % idx) ) ] }
  (let [coll-tx (map func coll)   ; transform all data
        result  (flatten  [ (take idx coll-tx)        ; [0..idx-1]
                            (nth coll idx)            ; idx
                            (drop (inc idx) coll-tx)  ; [idx+1..N-1]
                          ] ) ]
    result ))

(def xx [ 0 1 2 3 4 ] )

(prn (map-not-nth str xx 0))
(prn (map-not-nth str xx 1))
(prn (map-not-nth str xx 2))
(prn (map-not-nth str xx 3))
(prn (map-not-nth str xx 4))

user=> (prn (map-not-nth str xx 0))
(0 "1" "2" "3" "4")
user=> (prn (map-not-nth str xx 1))
("0" 1 "2" "3" "4")
user=> (prn (map-not-nth str xx 2))
("0" "1" 2 "3" "4")
user=> (prn (map-not-nth str xx 3))
("0" "1" "2" 3 "4")
user=> (prn (map-not-nth str xx 4))
("0" "1" "2" "3" 4)