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1 ;;!emacs
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2 ;;
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3 ;; FILE: hvar.el
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4 ;; SUMMARY: Variable manipulation routines for Hyperbole.
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5 ;; USAGE: GNU Emacs Lisp Library
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6 ;; KEYWORDS: extensions, hypermedia
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7 ;;
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8 ;; AUTHOR: Bob Weiner
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9 ;; ORG: Brown U.
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10 ;;
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11 ;; ORIG-DATE: 1-Oct-91 at 14:00:24
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12 ;; LAST-MOD: 14-Apr-95 at 16:13:46 by Bob Weiner
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13 ;;
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14 ;; This file is part of Hyperbole.
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15 ;; Available for use and distribution under the same terms as GNU Emacs.
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16 ;;
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17 ;; Copyright (C) 1991-1995, Free Software Foundation, Inc.
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18 ;; Developed with support from Motorola Inc.
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19 ;;
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20 ;; DESCRIPTION:
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21 ;; DESCRIP-END.
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22
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23 ;;; ************************************************************************
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24 ;;; Other required Elisp libraries
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25 ;;; ************************************************************************
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26
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27 (require 'set)
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28
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29 ;;; ************************************************************************
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30 ;;; Public functions
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31 ;;; ************************************************************************
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32
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33 ;;;###autoload
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34 (defun var:append (var-symbol-name list-to-add)
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35 "Appends to value held by VAR-SYMBOL-NAME, LIST-TO-ADD. Returns new value.
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36 If VAR-SYMBOL-NAME is unbound, it is set to LIST-TO-ADD.
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37 Often used to append to 'hook' variables."
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38 (let ((val))
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39 (if (and (boundp var-symbol-name)
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40 (setq val (symbol-value var-symbol-name))
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41 (or (if (symbolp val) (setq val (cons val nil)))
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42 (listp val)))
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43 ;; Don't add if list elts are already there.
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44 (if (memq nil (mapcar (function
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45 (lambda (elt) (set:member elt val)))
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46 list-to-add))
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47 (set-variable var-symbol-name
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48 (if (eq (car val) 'lambda)
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49 (apply 'list val list-to-add)
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50 (append val list-to-add)))
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51 val)
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52 (set-variable var-symbol-name list-to-add))))
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53
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54 (provide 'hvar)
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55
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