Function: range-intersection

range-intersection is a byte-compiled function defined in range.el.gz.

Signature

(range-intersection RANGE1 RANGE2)

Documentation

Return intersection of RANGE1 and RANGE2.

Aliases

gnus-sorted-range-intersection (obsolete since 29.1)

Source Code

;; Defined in /usr/src/emacs/lisp/emacs-lisp/range.el.gz
(defun range-intersection (range1 range2)
  "Return intersection of RANGE1 and RANGE2."
  (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 precedes range2
             (setq range1 (cdr range1)
                   min1 nil))
            ((< max2 min1)              ; range2 precedes 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)))))