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1 ;;; symbols.el --- functions for working with symbols and symbol values
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2
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3 ;; Copyright (C) 1996 Ben Wing.
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4
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5 ;; This file is part of XEmacs.
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6
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7 ;; XEmacs is free software; you can redistribute it and/or modify it
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8 ;; under the terms of the GNU General Public License as published by
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9 ;; the Free Software Foundation; either version 2, or (at your option)
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10 ;; any later version.
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11
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12 ;; XEmacs is distributed in the hope that it will be useful, but
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13 ;; WITHOUT ANY WARRANTY; without even the implied warranty of
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14 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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15 ;; General Public License for more details.
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16
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17 ;; You should have received a copy of the GNU General Public License
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18 ;; along with XEmacs; see the file COPYING. If not, write to the Free
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19 ;; Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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20
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21 ;;; Synched up with: Not in FSF.
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22
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23 ;;; Not yet dumped into XEmacs.
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24
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25 ;;; Commentary:
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26
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27 ;; The idea behind magic variables is that you can specify arbitrary
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28 ;; behavior to happen when setting or retrieving a variable's value. The
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29 ;; purpose of this is to make it possible to cleanly provide support for
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30 ;; obsolete variables (e.g. unread-command-event, which is obsolete for
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31 ;; unread-command-events) and variable compatibility
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32 ;; (e.g. suggest-key-bindings, the FSF equivalent of
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33 ;; teach-extended-commands-p and teach-extended-commands-timeout).
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34 ;;
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35 ;; There are a large number of functions pertaining to a variable's
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36 ;; value:
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37 ;;
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38 ;; boundp
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39 ;; globally-boundp
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40 ;; makunbound
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41 ;; symbol-value
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42 ;; set / setq
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43 ;; default-boundp
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44 ;; default-value
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45 ;; set-default / setq-default
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46 ;; make-variable-buffer-local
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47 ;; make-local-variable
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48 ;; kill-local-variable
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49 ;; kill-console-local-variable
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50 ;; symbol-value-in-buffer
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51 ;; symbol-value-in-console
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52 ;; local-variable-p / local-variable-if-set-p
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53 ;;
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54 ;; Plus some "meta-functions":
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55 ;;
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56 ;; defvaralias
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57 ;; variable-alias
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58 ;; indirect-variable
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59 ;;
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60 ;; I wanted an implementation that:
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61 ;;
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62 ;; -- would work with all the above functions, but (a) didn't require
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63 ;; a separate handler for every function, and (b) would work OK
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64 ;; even if more functions are added (e.g. `set-symbol-value-in-buffer'
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65 ;; or `makunbound-default') or if more arguments are added to a
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66 ;; function.
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67 ;; -- avoided consing if at all possible.
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68 ;; -- didn't slow down operations on non-magic variables (therefore,
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69 ;; storing the magic information using `put' is ruled out).
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70 ;;
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71
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72 ;;; Code:
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73
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74 ;; perhaps this should check whether the functions are bound, so that
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75 ;; some handlers can be unspecified. That requires that all functions
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76 ;; are defined before `define-magic-variable-handlers' is called,
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77 ;; though.
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78
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79 ;; perhaps there should be something that combines
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80 ;; `define-magic-variable-handlers' with `defvaralias'.
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81
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82 (defun define-magic-variable-handlers (variable handler-class harg)
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83 "Set the magic variable handles for VARIABLE to those in HANDLER-CLASS.
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84 HANDLER-CLASS should be a symbol. The handlers are constructed by adding
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85 the handler type to HANDLER-CLASS. HARG is passed as the HARG value for
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86 each of the handlers."
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87 (mapcar
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88 #'(lambda (htype)
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89 (set-magic-variable-handler variable htype
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90 (intern (concat (symbol-value handler-class)
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91 "-"
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92 (symbol-value htype)))
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93 harg))
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94 '(get-value set-value other-predicate other-action)))
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95
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96 ;; unread-command-event
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97
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98 (defun mvh-first-of-list-get-value (sym fun args harg)
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99 (car (apply fun harg args)))
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100
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101 (defun mvh-first-of-list-set-value (sym value setfun getfun args harg)
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102 (apply setfun harg (cons value (apply getfun harg args)) args))
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103
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104 (defun mvh-first-of-list-other-predicate (sym fun args harg)
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105 (apply fun harg args))
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106
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107 (defun mvh-first-of-list-other-action (sym fun args harg)
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108 (apply fun harg args))
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109
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110 (define-magic-variable-handlers 'unread-command-event
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111 'mvh-first-of-list
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112 'unread-command-events)
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113
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114 ;; last-command-char, last-input-char, unread-command-char
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115
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116 (defun mvh-char-to-event-get-value (sym fun args harg)
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117 (event-to-character (apply fun harg args)))
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118
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119 (defun mvh-char-to-event-set-value (sym value setfun getfun args harg)
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120 (let ((event (apply getfun harg args)))
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121 (if (event-live-p event)
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122 nil
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123 (setq event (allocate-event))
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124 (apply setfun harg event args))
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125 (character-to-event value event)))
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126
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127 (defun mvh-char-to-event-other-predicate (sym fun args harg)
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128 (apply fun harg args))
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129
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130 (defun mvh-char-to-event-other-action (sym fun args harg)
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131 (apply fun harg args))
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132
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133 (define-magic-variable-handlers 'last-command-char
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134 'mvh-char-to-event
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135 'last-command-event)
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136
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137 (define-magic-variable-handlers 'last-input-char
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138 'mvh-char-to-event
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139 'last-input-event)
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140
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141 (define-magic-variable-handlers 'unread-command-char
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142 'mvh-char-to-event
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143 'unread-command-event)
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144
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145 ;; suggest-key-bindings
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146
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147 (set-magic-variable-handler
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148 'suggest-key-bindings 'get-value
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149 #'(lambda (sym fun args harg)
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150 (and (apply fun 'teach-extended-commands-p args)
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151 (apply fun 'teach-extended-commands-timeout args))))
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152
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153 (set-magic-variable-handler
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154 'suggest-key-bindings 'set-value
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155 #'(lambda (sym value setfun getfun args harg)
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156 (apply setfun 'teach-extended-commands-p (not (null value)) args)
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157 (if value
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158 (apply 'teach-extended-commands-timeout
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159 (if (numberp value) value 2) args))))
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160
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161 (set-magic-variable-handler
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162 'suggest-key-bindings 'other-action
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163 #'(lambda (sym fun args harg)
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164 (apply fun 'teach-extended-commands-p args)
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165 (apply fun 'teach-extended-commands-timeout args)))
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166
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167 (set-magic-variable-handler
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168 'suggest-key-bindings 'other-predicate
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169 #'(lambda (sym fun args harg)
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170 (and (apply fun 'teach-extended-commands-p args)
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171 (apply fun 'teach-extended-commands-timeout args))))
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