+;; This function returns a sequence of article numbers based on the
+;; difference between the ranges of read articles in this group and
+;; the range of active articles.
+(defun gnus-sequence-of-unread-articles (group)
+ (let* ((read (gnus-info-read (gnus-get-info group)))
+ (active (or (gnus-active group) (gnus-activate-group group)))
+ (last (cdr active))
+ first nlast unread)
+ ;; If none are read, then all are unread.
+ (if (not read)
+ (setq first (car active))
+ ;; If the range of read articles is a single range, then the
+ ;; first unread article is the article after the last read
+ ;; article. Sounds logical, doesn't it?
+ (if (and (not (listp (cdr read)))
+ (or (< (car read) (car active))
+ (progn (setq read (list read))
+ nil)))
+ (setq first (max (car active) (1+ (cdr read))))
+ ;; `read' is a list of ranges.
+ (when (/= (setq nlast (or (and (numberp (car read)) (car read))
+ (caar read)))
+ 1)
+ (setq first (car active)))
+ (while read
+ (when first
+ (push (cons first nlast) unread))
+ (setq first (1+ (if (atom (car read)) (car read) (cdar read))))
+ (setq nlast (if (atom (cadr read)) (cadr read) (caadr read)))
+ (setq read (cdr read)))))
+ ;; And add the last unread articles.
+ (cond ((< first last)
+ (push (cons first last) unread))
+ ((= first last)
+ (push first unread)))
+ ;; Return the sequence of unread articles.
+ (delq 0 (nreverse unread))))
+