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2548
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1 ;;; regexp-opt.el --- generate efficient regexps to match strings
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2
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3 ;; Copyright (C) 1994,95,96,97,98,99,2000 Free Software Foundation, Inc.
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4
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5 ;; Author: Simon Marshall <simon@gnu.org>
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6 ;; Maintainer: FSF
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7 ;; Keywords: strings, regexps, extensions
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8
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9 ;; Modified by Karl M. Hegbloom Sep. 1997 to support the new regexp syntax
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10 ;; with shy groups. (benchmarks pending)
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11
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12 ;; This file is part of XEmacs.
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13
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14 ;; XEmacs is free software; you can redistribute it and/or modify
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15 ;; it under the terms of the GNU General Public License as published by
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16 ;; the Free Software Foundation; either version 2, or (at your option)
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17 ;; any later version.
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18
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19 ;; XEmacs is distributed in the hope that it will be useful,
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20 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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21 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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22 ;; GNU General Public License for more details.
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23
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24 ;; You should have received a copy of the GNU General Public License
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25 ;; along with XEmacs; see the file COPYING. If not, write to the
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26 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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27 ;; Boston, MA 02111-1307, USA.
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28
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29 ;;; Commentary:
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30
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31 ;; The "opt" in "regexp-opt" stands for "optim\\(al\\|i\\(se\\|ze\\)\\)".
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32 ;;
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33 ;; This package generates a regexp from a given list of strings (which matches
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34 ;; one of those strings) so that the regexp generated by:
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35 ;;
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36 ;; (regexp-opt strings)
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37 ;;
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38 ;; is equivalent to, but more efficient than, the regexp generated by:
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39 ;;
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40 ;; (mapconcat 'regexp-quote strings "\\|")
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41 ;;
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42 ;; For example:
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43 ;;
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44 ;; (let ((strings '("cond" "if" "when" "unless" "while"
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45 ;; "let" "let*" "progn" "prog1" "prog2"
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46 ;; "save-restriction" "save-excursion" "save-window-excursion"
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47 ;; "save-current-buffer" "save-match-data"
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48 ;; "catch" "throw" "unwind-protect" "condition-case")))
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49 ;; (concat "(" (regexp-opt strings t) "\\>"))
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50 ;;
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51 ;; => "(\\(?:c\\(?:atch\\|ond\\(?:ition-case\\)?\\)\\|if\\|let\\*?\\|prog[12n]\\|save-\\(?:current-buffer\\|excursion\\|match-data\\|restriction\\|window-excursion\\)\\|throw\\|un\\(?:less\\|wind-protect\\)\\|wh\\(?:en\\|ile\\)\\)\\>"
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52 ;;
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53 ;;
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54 ;; (let ((strings '("cond" "if" "when" "unless" "while"
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55 ;; "let" "let*" "progn" "prog1" "prog2"
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56 ;; "save-restriction" "save-excursion" "save-window-excursion"
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57 ;; "save-current-buffer" "save-match-data"
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58 ;; "catch" "throw" "unwind-protect" "condition-case")))
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59 ;; (concat "(" (regexp-opt strings t t) "\\>"))
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60 ;; ^
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61 ;; => "(\\(c\\(atch\\|ond\\(ition-case\\)?\\)\\|if\\|let\\*?\\|prog[12n]\\|save-\\(current-buffer\\|excursion\\|match-data\\|restriction\\|window-excursion\\)\\|throw\\|un\\(less\\|wind-protect\\)\\|wh\\(en\\|ile\\)\\)\\>"
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62 ;;
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63 ;;
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64 ;; Searching using the above example `regexp-opt' regexp takes approximately
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65 ;; two-thirds of the time taken using the equivalent `mapconcat' regexp.
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66
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67 ;; Since this package was written to produce efficient regexps, not regexps
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68 ;; efficiently, it is probably not a good idea to in-line too many calls in
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69 ;; your code, unless you use the following trick with `eval-when-compile':
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70 ;;
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71 ;; (defvar definition-regexp
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72 ;; (eval-when-compile
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73 ;; (concat "^("
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74 ;; (regexp-opt '("defun" "defsubst" "defmacro" "defalias"
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75 ;; "defvar" "defconst") t)
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76 ;; "\\>")))
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77 ;;
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78 ;; The `byte-compile' code will be as if you had defined the variable thus:
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79 ;;
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80 ;; (defvar definition-regexp
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81 ;; "^(\\(def\\(alias\\|const\\|macro\\|subst\\|un\\|var\\)\\)\\>")
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82 ;;
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83 ;; Note that if you use this trick for all instances of `regexp-opt' and
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84 ;; `regexp-opt-depth' in your code, regexp-opt.el would only have to be loaded
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85 ;; at compile time. But note also that using this trick means that should
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86 ;; regexp-opt.el be changed, perhaps to fix a bug or to add a feature to
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87 ;; improve the efficiency of `regexp-opt' regexps, you would have to recompile
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88 ;; your code for such changes to have effect in your code.
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89
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90 ;; Originally written for font-lock.el, from an idea from Stig's hl319.el, with
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91 ;; thanks for ideas also to Michael Ernst, Bob Glickstein and Dan Nicolaescu.
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92 ;; Please don't tell me that it doesn't produce optimal regexps; I know that
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93 ;; already. For example, the above explanation for the meaning of "opt" would
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94 ;; be more efficient as "optim\\(al\\|i[sz]e\\)", but this requires complex
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95 ;; forward looking. But (ideas or) code to improve things (are) is welcome.
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96
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97 ;;; Code:
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98
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99 ;;;###autoload
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100 (defun regexp-opt (strings &optional paren non-shy)
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101 "Return a regexp to match a string in STRINGS.
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102 Each string should be unique in STRINGS and should not contain any regexps,
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103 quoted or not. If optional PAREN is non-nil, ensure that the returned regexp
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104 is enclosed by at least one regexp match grouping construct. If optional
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105 NON-SHY is non nil, the inner groupings will use \"\\\\( \\\\)\" grouping,
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106 rather than the default \"\\\\(?: \\\\)\" 'shy', or non-match-capturing groups.
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107 The returned regexp is typically more efficient than the equivalent regexp:
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108
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109 (let ((open-paren (if PAREN \"\\\\(\" \"\")) (close-paren (if PAREN \"\\\\)\" \"\")))
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110 (concat open-paren (mapconcat 'regexp-quote STRINGS \"\\\\|\") close-paren))
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111
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112 but typically contains more regexp grouping constructs.
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113 Use `regexp-opt-depth' to count them.
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114
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115 If PAREN is `words', then the resulting regexp is additionally surrounded
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116 by \\=\\< and \\>."
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117 (save-match-data
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118 ;; Recurse on the sorted list.
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119 (let* ((max-lisp-eval-depth (* 1024 1024))
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120 (completion-ignore-case nil)
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121 (words (eq paren 'words))
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122 (sorted-strings (sort (copy-sequence strings) 'string-lessp))
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123 (re (regexp-opt-group sorted-strings paren nil non-shy)))
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124 (if words (concat "\\<" re "\\>") re))))
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125
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126 ;;;###autoload
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127 (defun regexp-opt-depth (regexp &optional count-shy-groups-too)
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128 "Return the depth of REGEXP.
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129 This means the number of regexp grouping constructs (parenthesised
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130 expressions) in REGEXP, not counting the \"\\\\(?: \\\\)\"
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131 non-match-capturing groups unless COUNT-SHY-GROUPS-TOO is non-nil.
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132 See `regexp-opt'."
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133 (save-match-data
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134 ;; Hack to signal an error if REGEXP does not have balanced parentheses.
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135 (string-match regexp "")
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136 ;; Count the number of open parentheses in REGEXP.
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137 (let ((max (1- (length regexp)))
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138 (count 0) start)
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139 (while (string-match "\\\\(" regexp start)
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140 (setq start (match-end 0))
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141 (when (or count-shy-groups-too
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142 (not (string= (substring regexp start (min (+ start 2) max)) "?:")))
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143 (setq count (1+ count))))
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144 count)))
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145
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146 ;;; Workhorse functions.
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147
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148 (eval-when-compile
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149 (require 'cl))
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150
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151 (unless (fboundp 'make-bool-vector)
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152 (defalias 'make-bool-vector 'make-vector))
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153
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154 (defun regexp-opt-group (strings &optional paren lax non-shy)
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155 "Return a regexp to match a string in STRINGS.
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156 If PAREN non-nil, output regexp parentheses around returned regexp.
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157 If LAX non-nil, don't output parentheses if it doesn't require them.
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158 If NON-SHY non-nil, don't use \\(?: \\) shy groups, use match capturing ones.
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159 Merges keywords to avoid backtracking in Emacs' regexp matcher.
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160
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161 The basic idea is to find the shortest common prefix, remove it
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162 and recurse. If there is no prefix, we divide the list into two so that
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163 \(at least) one half will have at least a one-character common prefix.
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164
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165 Also we delay the addition of grouping parenthesis as long as possible
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166 until we're sure we need them, and try to remove one-character sequences
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167 so we can use character sets rather than grouping parenthesis."
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168 (let* ((open-group (cond
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169 ((and paren non-shy) "\\(")
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170 (paren "\\(?:")
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171 (t "")))
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172 (close-group (if paren "\\)" ""))
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173 (open-charset (if lax "" open-group))
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174 (close-charset (if lax "" close-group)))
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175 (cond
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176 ;;
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177 ;; If there are no strings, just return the empty string.
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178 ((= (length strings) 0)
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179 "")
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180 ;;
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181 ;; If there is only one string, just return it.
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182 ((= (length strings) 1)
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183 (if (= (length (car strings)) 1)
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184 (concat open-charset (regexp-quote (car strings)) close-charset)
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185 (concat open-group (regexp-quote (car strings)) close-group)))
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186 ;;
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187 ;; If there is an empty string, remove it and recurse on the rest.
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188 ((= (length (car strings)) 0)
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189 (concat open-charset
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190 (regexp-opt-group (cdr strings) t t non-shy) "?"
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191 close-charset))
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192 ;;
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193 ;; If all are one-character strings, just return a character set.
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194 ((= (length strings) (apply '+ (mapcar 'length strings)))
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195 (concat open-charset
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196 (regexp-opt-charset strings)
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197 close-charset))
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198 ;;
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199 ;; We have a list of different length strings.
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200 (t
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201 (let ((prefix (try-completion "" (mapcar 'list strings)))
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202 (letters (let ((completion-regexp-list '("^.$")))
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203 (all-completions "" (mapcar 'list strings)))))
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204 (cond
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205 ;;
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206 ;; If there is a common prefix, remove it and recurse on the suffixes.
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207 ((> (length prefix) 0)
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208 (let* ((length (length prefix))
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209 (suffixes (mapcar (lambda (s) (substring s length)) strings)))
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210 (concat open-group
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211 (regexp-quote prefix) (regexp-opt-group suffixes t t non-shy)
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212 close-group)))
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213 ;;
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214 ;; If there are several one-character strings, remove them and recurse
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215 ;; on the rest (first so the final regexp finds the longest match).
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216 ((> (length letters) 1)
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217 (let ((rest (let ((completion-regexp-list '("^..+$")))
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218 (all-completions "" (mapcar 'list strings)))))
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219 (concat open-group
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220 (regexp-opt-group rest nil nil non-shy) "\\|" (regexp-opt-charset letters)
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221 close-group)))
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222 ;;
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223 ;; Otherwise, divide the list into those that start with a particular
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224 ;; letter and those that do not, and recurse on them.
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225 (t
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226 (let* ((char (substring (car strings) 0 1))
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227 (half1 (all-completions char (mapcar 'list strings)))
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228 (half2 (nthcdr (length half1) strings)))
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229 (concat open-group
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230 (regexp-opt-group half1 nil nil non-shy) "\\|" (regexp-opt-group half2 nil nil non-shy)
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231 close-group)))))))))
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232
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233 (defun regexp-opt-charset (chars)
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234 ;;
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235 ;; Return a regexp to match a character in CHARS.
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236 ;;
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237 ;; The basic idea is to find character ranges. Also we take care in the
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238 ;; position of character set meta characters in the character set regexp.
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239 ;;
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240 (let* ((charwidth 256) ; Yeah, right.
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241 ;; XEmacs: use bit-vectors instead of bool-vectors
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242 (charmap (make-bit-vector charwidth 0))
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243 (charset "")
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244 (bracket "") (dash "") (caret ""))
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245 ;;
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246 ;; Make a character map but extract character set meta characters.
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247 (dolist (char (mapcar 'string-to-char chars))
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248 (case char
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249 (?\]
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250 (setq bracket "]"))
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251 (?^
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252 (setq caret "^"))
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253 (?-
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254 (setq dash "-"))
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255 (otherwise
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256 ;; XEmacs: 1
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257 (aset charmap char 1))))
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258 ;;
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259 ;; Make a character set from the map using ranges where applicable.
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260 (dotimes (char charwidth)
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261 (let ((start char))
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262 (while (and (< char charwidth)
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263 ;; XEmacs: (not (zerop ...))
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264 (not (zerop (aref charmap char))))
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265 (incf char))
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266 (cond ((> char (+ start 3))
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267 (setq charset (format "%s%c-%c" charset start (1- char))))
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268 ((> char start)
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269 (setq charset (format "%s%c" charset (setq char start)))))))
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270 ;;
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271 ;; Make sure a caret is not first and a dash is first or last.
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272 (if (and (string-equal charset "") (string-equal bracket ""))
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273 (concat "[" dash caret "]")
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274 (concat "[" bracket charset caret dash "]"))))
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275
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276 (provide 'regexp-opt)
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277
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278 ;;; regexp-opt.el ends here
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