;;; alpha-point.el --- Figure out where to put a record in an alphabetically sorted file of records.
;; Copyright (C) 1997 Yale University
;; Author: Bradley C. Kuszmaul <bradley@ee.yale.edu>

;; This file is distributed under the terms of the GNU General Public
;; License (GPL) as published by the Free Software Foundation;  either
;; version 2, or (at your option) any later version.
;;
;; This file is distributed in the hope that it will be useful, but
;; without any warranty; without even the implied warranty of
;; merchantability or fitness for a particular purpose.  See the GPL
;; for details.
;;
;; You should have received a copy of the GPL along with GNU emacs.
;; Presumably, you need GNU emacs to use this program.

;; Find a key in an emacs file that is sorted alphabetically

;; LCD Archive Entry:
;; alpha-point|Bradley C. Kuszmaul|bradley@ee.yale.edu|
;; Figure out where to put a record in an alphabetically sorted file of records (useful for editing bibtex files and rolodex or address books.)|
;; $Date: 1997/07/30 16:22:13 $|$Id: alpha-point.el,v 1.3 1997/07/30 16:22:13 bradley Exp $|


(defvar alpha-find-beginning-of-record "^\n\\s-*\\(%.*\n\\)*" "A regexp to determine where the beginning of the alphabetical part of the record is.   The regexp must preceed the key.

The default is to find a paragraph (delimited by a blank line) and skip over any lines that begin with optional whitespace followed by a percent.  This works well for latex and also for some other files, such as Bradley's name-and-address file.")

;; This is suitable for bibtex mode.
;; It is an @ at the beginning of the line, followed by some letters
;; followed by an open bracket or parent, followed by optional whitespace or endcomments (newlines and control-L are endcomment)
(defvar bibtex-find-beginning-of-record "^@[A-Za-z]+[[{(]\\(\\s-\\|\\s>\\)*" "A good value for alpha-find-beginning-of-record in bibtex mode")
(add-hook 'bibtex-mode-hook
	  (function (lambda ()
		      (set (make-local-variable 'alpha-find-beginning-of-record)
			   bibtex-find-beginning-of-record))))

(defun alpha-point (name)
  "Find where to put name in an alphabetically sorted file.
  Finds the first entry in the file which is alphabetically >= the argument.
  Uses alpha-find-beginning-of-record to find the beginning of the key.

  For example, in a bibtex file where the labels are kept in ascending alphabetical order,
  try doing
    m-x alpha-point <return> foo <return>
  The point will be placed at the first record whose label is lexically after foo.

  Bradley binds alpha-point to C-. (which works just fine under X, but won't work under most older systems where the control key is not allowed to modify period.)"
  (interactive "sName to find:")
  (goto-char (point-min))
  (block nil
    (let ((nb (get-buffer-create " *Alpha Find*"))
	  (nb-position nil)
	  (nb-end nil)
	  (cb (current-buffer))
	  (cb-position (point)))
      (set-buffer nb)
      (goto-char (point-min))
      (delete-char (- (point-max) (point-min)) nil)
      (insert name)
      (setq nb-position (point-min))
      (setq nb-end      (point-max))
      (set-buffer cb)
      (while (search-forward-regexp
	      alpha-find-beginning-of-record (point-max) t)
	(setq cb-position (point))
	(if (null (search-forward-regexp "\\s-" (point-max) t))
	    (goto-char (point-max)))
	(setq cb-end (- (point) 1))
	(goto-char cb-position)
	(let ((comp (compare-buffer-substrings nb nb-position nb-end
					       cb cb-position cb-end)))
	  (cond ((<= comp 0)
		 (return nil))))))))


;;; $Log: alpha-point.el,v $
;;; Revision 1.3  1997/07/30 16:22:13  bradley
;;; Fix a typo
;;;
;;; Revision 1.2  1997/07/30 02:09:33  bradley
;;; alpha-point modifications
;;;
;;; Revision 1.1  1997/07/30 02:01:59  bradley
;;; Initial version.
;;;