+;;;###autoload
+(defun gnus-sorted-range-intersection (range1 range2)
+ "Return intersection of RANGE1 and RANGE2.
+RANGE1 and RANGE2 have to be sorted over <."
+ (let* (out
+ (min1 (car range1))
+ (max1 (if (numberp min1)
+ (if (numberp (cdr range1))
+ (prog1 (cdr range1)
+ (setq range1 nil)) min1)
+ (prog1 (cdr min1)
+ (setq min1 (car min1)))))
+ (min2 (car range2))
+ (max2 (if (numberp min2)
+ (if (numberp (cdr range2))
+ (prog1 (cdr range2)
+ (setq range2 nil)) min2)
+ (prog1 (cdr min2)
+ (setq min2 (car min2))))))
+ (setq range1 (cdr range1)
+ range2 (cdr range2))
+ (while (and min1 min2)
+ (cond ((< max1 min2) ; range1 preceeds range2
+ (setq range1 (cdr range1)
+ min1 nil))
+ ((< max2 min1) ; range2 preceeds range1
+ (setq range2 (cdr range2)
+ min2 nil))
+ (t ; some sort of overlap is occurring
+ (let ((min (max min1 min2))
+ (max (min max1 max2)))
+ (setq out (if (= min max)
+ (cons min out)
+ (cons (cons min max) out))))
+ (if (< max1 max2) ; range1 ends before range2
+ (setq min1 nil) ; incr range1
+ (setq min2 nil)))) ; incr range2
+ (unless min1
+ (setq min1 (car range1)
+ max1 (if (numberp min1) min1 (prog1 (cdr min1) (setq min1 (car min1))))
+ range1 (cdr range1)))
+ (unless min2
+ (setq min2 (car range2)
+ max2 (if (numberp min2) min2 (prog1 (cdr min2) (setq min2 (car min2))))
+ range2 (cdr range2))))
+ (cond ((cdr out)
+ (nreverse out))
+ ((numberp (car out))
+ out)
+ (t
+ (car out)))))
+