Regions - multiple selections

6.el

(provide 'regions)

(defvar regions nil
  "Regions in buffer.")

(defun regions-maybe-push-selection ()
  "Push mark and point if point is not in regions."
  (let ((point (point))
        exists)
    (dolist (sel regions)
      (when (= point (cdr sel))
        (setq exists t)))
    (unless exists
      (push (cons (mark) (point)) regions))))

(defun regions-maybe-merge ()
  "Sort and merge overlap selections."
  (unless (>= 1 (length regions))
    (setq regions
          (sort regions #'(lambda (a b) (< (car a) (car b)))))
    ;; I'm pretty sure there should be a more lipsy way
    (let ((i 0)
          (j 1)
          (sel (nth 0 regions))
          new-regions
          a b
          (len (length regions))
          (cont t))
      (while cont
        (setq a (cdr sel)
              b (car (nth j regions)))
        (if (<= a b)
            (progn
              (push sel new-regions)
              (setq i j
                    j (1+ i)
                    sel (nth i regions)))
          (setcdr sel (cdr (nth j regions)))
          (incf j))
        (when (>= j len)
          (incf i)
          (setq j (1+ i)))
        (when (>= i (1- len))
          (push sel new-regions)
          (setq cont nil)))
      (setq regions new-regions))))