+ (cond ((or (stringp seq) (vectorp seq)) (substring seq start end))
+ ((listp seq)
+ (let (len
+ (errtext (format "Bad bounding indices: %s, %s" start end)))
+ (and end (< end 0) (setq end (+ end (setq len (length seq)))))
+ (if (< start 0) (setq start (+ start (or len (setq len (length seq))))))
+ (unless (>= start 0)
+ (error "%s" errtext))
+ (when (> start 0)
+ (setq seq (nthcdr (1- start) seq))
+ (or seq (error "%s" errtext))
+ (setq seq (cdr seq)))
+ (if end
+ (let ((res nil))
+ (while (and (>= (setq end (1- end)) start) seq)
+ (push (pop seq) res))
+ (or (= (1+ end) start) (error "%s" errtext))
+ (nreverse res))
+ (copy-sequence seq))))
+ (t (error "Unsupported sequence: %s" seq))))
+
+;;;###autoload
+(defun cl-concatenate (type &rest sequences)