ring+.el - extensions to GNU `ring.el'

[Drew Adams]

;;; ring+.el --- Extensions to `ring.el'.
;; 
;; Filename: ring+.el
;; Description: Extensions to `ring.el'.
;; Author: Drew Adams
;; Maintainer: Drew Adams
;; Copyright (C) 1996-2001, Drew Adams, all rights reserved.
;; Created: Thu Apr 11 16:46:04 1996
;; Version: $Id: ring+.el,v 1.4 2001/01/09 22:13:30 dadams Exp $
;; Last-Updated: Tue Jan  9 14:13:12 2001
;;           By: dadams
;;     Update #: 62
;; Keywords: extensions, lisp, local
;; Compatibility: GNU Emacs 20.x
;; 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; 
;;; Commentary: 
;; 
;;    Extensions to `ring.el'.
;; 
;;  Main new functions here:
;;    `ring-insert-new', `ring-member'.
;;
;;
;;  This file should be loaded after loading the standard GNU file
;;  `ring.el'.  So, in your `~/.emacs' file, do this:
;;  (eval-after-load "ring" '(progn (require 'ring+))
;; 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; 
;;; Change log:
;; 
;; RCS $Log: ring+.el,v $
;; RCS Revision 1.4  2001/01/09 22:13:30  dadams
;; RCS Adapted file header for Emacs Lisp Archive.
;; RCS
;; RCS Revision 1.3  2001/01/03 17:44:45  dadams
;; RCS *** empty log message ***
;; RCS
;; RCS Revision 1.2  2001/01/03 01:07:28  dadams
;; RCS *** empty log message ***
;; RCS
;; RCS Revision 1.1  2000/09/14 17:23:45  dadams
;; RCS Initial revision
;; RCS
; Revision 1.1  1997/03/20  17:54:48  dadams
; Initial revision
;
; Revision 1.3  1996/07/01  13:22:02  dadams
; (trivial)
;
; Revision 1.2  1996/04/12  12:30:14  dadams
; (trivial)
;
; Revision 1.1  1996/04/12  12:22:54  dadams
; Initial revision
;; 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; 
;; This program is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

;; This program 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
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with this program; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; 
;;; Code:

(require 'ring) ;; ring-length, ring-ref, ring-remove, ring-insert
(require 'cl) ;; incf

(provide 'ring+)

;;;;;;;;;;;;;;;;;


;;;###autoload
(defun ring-member (item ring)
  "Returns index of ITEM if on RING, else nil.  Comparison via `equal'.
The index is 0-based."
  (let ((ind 0)
        (len (1- (ring-length ring)))
        (memberp nil))
    (while (and (<= ind len)
                (not (setq memberp (equal item (ring-ref ring ind)))))
      (incf ind))
    (and memberp ind)))


;;;###autoload
(defun ring-insert-new (ring item)
  "`ring-remove' ITEM from RING, then `ring-insert' it back onto RING.
This ensures that there is only one ITEM on RING.
Returns the new RING."
  (let (ind)
    (while (setq ind (ring-member item ring))
      (ring-remove ring ind)))
  (ring-insert ring item)
  ring)

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;;; `ring+.el' ends here