如何在给定字符串中每隔n个字符插入一个给定字符

Question

我正在寻找一种效率最高的Elisp代码，该代码可以在给定字符串中每隔n个字符插入一个给定字符。

Answer 1

(defun jea-insert-character-every-n-characters (beginstr insert-char count)
  (let ((blen (length beginstr))
        (result '())
        (c 1)
        (i 0))
    (while (< i blen)
      (push (elt beginstr i) result)
      (if (= c count)
          (progn
            (push insert-char result)
            (setq c 0)))
      (setq i (1+ i))
      (setq c (1+ c)))
    (concat (reverse result))))


(jea-insert-character-every-n-characters "This is the first test" ?X 3)  ;; "ThiXs iXs tXhe XfirXst XtesXt"
(jea-insert-character-every-n-characters "This is the second test" ?X 1) ;; "TXhXiXsX XiXsX XtXhXeX XsXeXcXoXnXdX XtXeXsXtX"
(jea-insert-character-every-n-characters "Boop the snoot" ?z 7)          ;; "Boop thze snootz"

可能有一种更有效的方法（我的elisp生锈了）。