相关疑难解决方法(0)

我想转换("USERID=XYZ" "USERPWD=123")为"USERID=XYZ&USERPWD=123".我试过了

(apply #'concatenate 'string '("USERID=XYZ" "USERPWD=123"))

将返回""USERID=XYZUSERPWD=123".

但我不知道如何插入'&'？以下功能有效但似乎有点复杂.

(defun join (list &optional (delim "&"))
    (with-output-to-string (s)
        (when list
            (format s "~A" (first list))
            (dolist (element (rest list))
               (format s "~A~A" delim element)))))