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1 ;;!emacs
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2 ;;
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3 ;; FILE: hhist.el
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4 ;; SUMMARY: Maintains history of Hyperbole buttons selected.
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5 ;; USAGE: GNU Emacs Lisp Library
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6 ;; KEYWORDS: 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: 24-Apr-91 at 03:36:23
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12 ;; LAST-MOD: 14-Apr-95 at 16:02:05 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 ;;
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22 ;; This is minimal right now and will be extended.
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23 ;; Currently, it implements a push-pop stack of traversed locations.
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24 ;;
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25 ;; It will be extended to allow random access to previous locations
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26 ;; and to store traversal histories for later recall.
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27 ;;
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28 ;; DESCRIP-END.
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29
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30 ;;; ************************************************************************
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31 ;;; Public functions
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32 ;;; ************************************************************************
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33
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34 (defun hhist:add (elt)
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35 "Adds ELT to hyper-history list if not the same as current or previous loc.
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36 ELT must have been created via a call to 'hhist:element'."
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37 ;; Even though this next line looks useless, it cures a problem with
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38 ;; window buffer correspondences on startup, so don't remove it.
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39 (set-buffer (window-buffer (selected-window)))
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40 (let ((prev-buf (car elt)))
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41 (if (or (equal prev-buf (buffer-name))
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42 (equal prev-buf (car (car *hhist*))))
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43 nil
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44 (setq *hhist* (cons elt *hhist*)))))
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45
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46 (defun hhist:element ()
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47 "Returns a history element for current point location."
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48 (list (current-buffer) (point)))
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49
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50 (defun hhist:remove (&optional arg)
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51 "Removes optional prefix ARG entries from history, returns to ARGth location.
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52 The command is ignored with ARG < 1."
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53 (interactive "p")
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54 (setq arg (or arg 1))
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55 (let ((prev-buf-line))
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56 (if (null *hhist*)
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57 (and (> arg 0)
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58 (message "(hhist:remove): No previous source to which to return.")
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59 (beep))
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60 (while (and (> arg 0) *hhist*)
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61 (setq prev-buf-line (car *hhist*)
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62 *hhist* (cdr *hhist*)
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63 arg (1- arg)))
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64 (switch-to-buffer (car prev-buf-line))
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65 (goto-char (car (cdr prev-buf-line)))
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66 )))
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67
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68 (defun hhist:init ()
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69 "Resets history list."
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70 (interactive)
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71 (setq *hhist* nil))
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72
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73 ;;; ************************************************************************
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74 ;;; Private functions
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75 ;;; ************************************************************************
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76
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77 (defun hhist:wind-line ()
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78 "Returns window relative line number that point is on."
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79 (max 0 (1- (- (count-lines 1 (1+ (point)))
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80 (count-lines 1 (window-start))))))
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81
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82 ;;; ************************************************************************
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83 ;;; Private variables
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84 ;;; ************************************************************************
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85
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86 (defconst *hhist* nil
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87 "List of previously visited Hyperbole button source locations.
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88 Car of list is most recent.")
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89
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90 (provide 'hhist)
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