使用說明：
(defvar json-string "[a,b,c:{c:1,d:2},e]")
(print (json-cvt json-string))
解析結果：
實現：
;;;; json convert
;;;; WHJ.20180916
(defun define-macro-character-function (char-end)
(lambda (stream char)
(let ((cnt 0))
(coerce
(loop for x = (read-char stream char-end)
if (char= x char)
collect x
and
do (incf cnt)
else if (zerop cnt)
if (char= x char-end)
do (loop-finish)
else
collect x
else
if (char= x char-end)
collect x
and
do (incf cnt -1)
else
collect x)
'string))))
(defun macro-character-comma (stream char)
'null)
(defun macro-character-colon (stream char)
'null)
(defun json-cvt-1 (json-string)
(let ((*readtable* (copy-readtable)))
(set-macro-character #\{ (define-macro-character-function #\}))
(set-macro-character #\[ (define-macro-character-function #\]))
(set-macro-character #\, #'macro-character-comma)
(set-macro-character #\: #'macro-character-colon)
(with-input-from-string (in json-string)
(loop for x = (read in nil)
while x
if (not (eq x 'null))
collect x))))
(defun json-cvt (json-string)
(let ((json-obj-list (json-cvt-1 json-string)))
(loop for i from 0 below (length json-obj-list)
for x = (nth i json-obj-list)
if (stringp x)
do (setf (nth i json-obj-list) (json-cvt x)))
(if (cdr json-obj-list)
json-obj-list
(car json-obj-list))))