(setq ll (cdr ll)))
(insert (car ll)))))
+;;;###autoload
+(defun delete-duplicate-lines (beg end &optional reverse adjacent interactive)
+ "Delete duplicate lines in the region between BEG and END.
+
+If REVERSE is nil, search and delete duplicates forward keeping the first
+occurrence of duplicate lines. If REVERSE is non-nil (when called
+interactively with C-u prefix), search and delete duplicates backward
+keeping the last occurrence of duplicate lines.
+
+If ADJACENT is non-nil (when called interactively with two C-u prefixes),
+delete repeated lines only if they are adjacent. It works like the utility
+`uniq' and is useful when lines are already sorted in a large file since
+this is more efficient in performance and memory usage than when ADJACENT
+is nil that uses additional memory to remember previous lines.
+
+When called from Lisp and INTERACTIVE is omitted or nil, return the number
+of deleted duplicate lines, do not print it; if INTERACTIVE is t, the
+function behaves in all respects as if it had been called interactively."
+ (interactive
+ (progn
+ (barf-if-buffer-read-only)
+ (list (region-beginning) (region-end)
+ (equal current-prefix-arg '(4))
+ (equal current-prefix-arg '(16))
+ t)))
+ (let ((lines (unless adjacent (make-hash-table :weakness 'key :test 'equal)))
+ line prev-line
+ (count 0)
+ (beg (copy-marker beg))
+ (end (copy-marker end)))
+ (save-excursion
+ (goto-char (if reverse end beg))
+ (if (and reverse (bolp)) (forward-char -1))
+ (while (if reverse
+ (and (> (point) beg) (not (bobp)))
+ (and (< (point) end) (not (eobp))))
+ (setq line (buffer-substring-no-properties
+ (line-beginning-position) (line-end-position)))
+ (if (if adjacent (equal line prev-line) (gethash line lines))
+ (progn
+ (delete-region (progn (forward-line 0) (point))
+ (progn (forward-line 1) (point)))
+ (if reverse (forward-line -1))
+ (setq count (1+ count)))
+ (if adjacent (setq prev-line line) (puthash line t lines))
+ (forward-line (if reverse -1 1)))))
+ (set-marker beg nil)
+ (set-marker end nil)
+ (when interactive
+ (message "Deleted %d %sduplicate line%s%s"
+ count
+ (if adjacent "adjacent " "")
+ (if (= count 1) "" "s")
+ (if reverse " backward" "")))
+ count))
+
(provide 'sort)
;;; sort.el ends here