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| 25 | <div class="chapter" lang="en"> |
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| 26 | <div class="titlepage"><div> |
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| 27 | <div><h2 class="title"> |
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| 28 | <a name="xpressive"></a>Chapter 21. Boost.Xpressive</h2></div> |
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| 29 | <div><div class="author"><h3 class="author"> |
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| 30 | <span class="firstname">Eric</span> <span class="surname">Niebler</span> |
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| 31 | </h3></div></div> |
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| 32 | <div><p class="copyright">Copyright © 2003, 2004 Eric Niebler</p></div> |
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| 33 | <div><div class="legalnotice"> |
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| 34 | <a name="id1953490"></a><p> |
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| 35 | Distributed under the Boost Software License, Version 1.0. (See accompanying |
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| 36 | file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) |
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| 37 | </p> |
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| 38 | </div></div> |
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| 39 | </div></div> |
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| 40 | <div class="toc"> |
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| 41 | <p><b>Table of Contents</b></p> |
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| 42 | <dl> |
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| 43 | <dt><span class="section"><a href="xpressive.html#boost_xpressive.preface">Preface</a></span></dt> |
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| 44 | <dt><span class="section"><a href="xpressive/user_s_guide.html">User's Guide</a></span></dt> |
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| 45 | <dd><dl> |
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| 46 | <dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.introduction">Introduction</a></span></dt> |
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| 47 | <dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.installing_xpressive">Installing xpressive</a></span></dt> |
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| 48 | <dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.quick_start">Quick Start</a></span></dt> |
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| 49 | <dt><span class="section"><a href="xpressive/user_s_guide.html#xpressive.user_s_guide.creating_a_regex_object">Creating a Regex Object</a></span></dt> |
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| 50 | <dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.matching_and_searching">Matching and Searching</a></span></dt> |
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| 51 | <dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.accessing_results">Accessing Results</a></span></dt> |
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| 52 | <dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.string_substitutions">String Substitutions</a></span></dt> |
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| 53 | <dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.string_splitting_and_tokenization">String Splitting and Tokenization</a></span></dt> |
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| 54 | <dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.grammars_and_nested_matches">Grammars and Nested Matches</a></span></dt> |
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| 55 | <dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.localization_and_regex_traits">Localization and Regex Traits</a></span></dt> |
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| 56 | <dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.tips_n_tricks"> Tips 'N Tricks</a></span></dt> |
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| 57 | <dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.concepts">Concepts</a></span></dt> |
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| 58 | <dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.examples">Examples</a></span></dt> |
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| 59 | </dl></dd> |
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| 60 | <dt><span class="section"><a href="xpressive/reference.html">Reference</a></span></dt> |
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| 61 | <dd><dl> |
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| 62 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.basic_regex.hpp">Header <boost/xpressive/basic_regex.hpp></a></span></dt> |
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| 63 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.traits.c_regex_traits.hpp">Header <boost/xpressive/traits/c_regex_traits.hpp></a></span></dt> |
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| 64 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.traits.cpp_regex_traits.hpp">Header <boost/xpressive/traits/cpp_regex_traits.hpp></a></span></dt> |
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| 65 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.match_results.hpp">Header <boost/xpressive/match_results.hpp></a></span></dt> |
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| 66 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.traits.null_regex_traits.hpp">Header <boost/xpressive/traits/null_regex_traits.hpp></a></span></dt> |
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| 67 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.regex_algorithms.hpp">Header <boost/xpressive/regex_algorithms.hpp></a></span></dt> |
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| 68 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.regex_compiler.hpp">Header <boost/xpressive/regex_compiler.hpp></a></span></dt> |
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| 69 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.regex_constants.hpp">Header <boost/xpressive/regex_constants.hpp></a></span></dt> |
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| 70 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.regex_error.hpp">Header <boost/xpressive/regex_error.hpp></a></span></dt> |
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| 71 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.regex_iterator.hpp">Header <boost/xpressive/regex_iterator.hpp></a></span></dt> |
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| 72 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.regex_primitives.hpp">Header <boost/xpressive/regex_primitives.hpp></a></span></dt> |
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| 73 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.regex_token_iterator.hpp">Header <boost/xpressive/regex_token_iterator.hpp></a></span></dt> |
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| 74 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.regex_traits.hpp">Header <boost/xpressive/regex_traits.hpp></a></span></dt> |
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| 75 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.sub_match.hpp">Header <boost/xpressive/sub_match.hpp></a></span></dt> |
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| 76 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.xpressive.hpp">Header <boost/xpressive/xpressive.hpp></a></span></dt> |
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| 77 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.xpressive_dynamic.hpp">Header <boost/xpressive/xpressive_dynamic.hpp></a></span></dt> |
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| 78 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.xpressive_fwd.hpp">Header <boost/xpressive/xpressive_fwd.hpp></a></span></dt> |
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| 79 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.xpressive_static.hpp">Header <boost/xpressive/xpressive_static.hpp></a></span></dt> |
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| 80 | <dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.xpressive_typeof.hpp">Header <boost/xpressive/xpressive_typeof.hpp></a></span></dt> |
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| 81 | </dl></dd> |
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| 82 | <dt><span class="section"><a href="boost_xpressive/acknowledgments.html">Acknowledgments</a></span></dt> |
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| 83 | <dt><span class="section"><a href="xpressive/appendices.html">Appendices</a></span></dt> |
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| 84 | <dd><dl> |
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| 85 | <dt><span class="section"><a href="xpressive/appendices.html#boost_xpressive.appendices.appendix_1__not_yet_implemented">Appendix 1: Not Yet Implemented</a></span></dt> |
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| 86 | <dt><span class="section"><a href="xpressive/appendices.html#boost_xpressive.appendices.appendix_2__differences_from_boost_regex">Appendix 2: Differences from Boost.Regex</a></span></dt> |
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| 87 | <dt><span class="section"><a href="xpressive/appendices.html#boost_xpressive.appendices.perf"> Appendix 3: Performance Comparison</a></span></dt> |
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| 88 | </dl></dd> |
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| 89 | </dl> |
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| 90 | </div> |
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| 91 | <div class="section" lang="en"> |
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| 92 | <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
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| 93 | <a name="boost_xpressive.preface"></a>Preface</h2></div></div></div> |
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| 94 | <div class="blockquote"><blockquote class="blockquote"><p> |
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| 95 | <span class="emphasis"><em>Wife:</em></span> It's a floor wax!<br> <span class="emphasis"><em>Husband:</em></span> |
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| 96 | No, it's a dessert topping!<br> <span class="emphasis"><em>Announcer:</em></span> Stop! You're |
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| 97 | both right. It's a floor wax <span class="emphasis"><em>and</em></span> a dessert topping! |
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| 98 | </p></blockquote></div> |
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| 99 | <div class="blockquote"><blockquote class="blockquote"><p> |
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| 100 | <span class="bold"><strong><span class="emphasis"><em>-- Saturday Night Live</em></span></strong></span> |
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| 101 | </p></blockquote></div> |
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| 102 | <a name="boost_xpressive.preface.description"></a><h2> |
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| 103 | <a name="id1953567"></a> |
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| 104 | Description |
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| 105 | </h2> |
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| 106 | <p> |
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| 107 | xpressive is an advanced, object-oriented regular expression template library |
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| 108 | for C++. Regular expressions can be written as strings that are parsed at run-time, |
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| 109 | or as expression templates that are parsed at compile-time. Regular expressions |
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| 110 | can refer to each other and to themselves recursively, allowing you to build |
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| 111 | arbitrarily complicated grammars out of them. |
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| 112 | </p> |
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| 113 | <a name="boost_xpressive.preface.motivation"></a><h2> |
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| 114 | <a name="id1953590"></a> |
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| 115 | Motivation |
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| 116 | </h2> |
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| 117 | <p> |
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| 118 | If you need to manipulate text in C++, you have typically had two disjoint |
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| 119 | options: a regular expression engine or a parser generator. Regular expression |
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| 120 | engines (like <a href="../../libs/regex" target="_top">Boost.Regex</a>) are powerful |
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| 121 | and flexible; patterns are represented as strings which can be specified at |
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| 122 | runtime. However, that means that syntax errors are likewise not detected until |
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| 123 | runtime. Also, regular expressions are ill-suited to advanced text processing |
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| 124 | tasks such as matching balanced, nested tags. Those tasks have traditionally |
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| 125 | been handled by parser generators (like the <a href="http://spirit.sourceforge.net" target="_top">Spirit |
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| 126 | Parser Framework</a>). These beasts are more powerful but less flexible. |
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| 127 | They generally don't allow you to arbitrarily modify your grammar rules on |
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| 128 | the fly. In addition, they don't have the exhaustive backtracking semantics |
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| 129 | of regular expressions, which can make it more challenging to author some types |
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| 130 | of patterns. |
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| 131 | </p> |
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| 132 | <p> |
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| 133 | xpressive brings these two approaches seamlessly together and occupies a unique |
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| 134 | niche in the world of C++ text processing. With xpressive, you can choose to |
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| 135 | use it much as you would use <a href="../../libs/regex" target="_top">Boost.Regex</a>, |
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| 136 | representing regular expressions as strings. Or you can use it as you would |
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| 137 | use <a href="http://spirit.sourceforge.net" target="_top">Spirit</a>, writing your |
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| 138 | regexes as C++ expressions, enjoying all the benefits of an embedded language |
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| 139 | dedicated to text manipulation. What's more, you can mix the two to get the |
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| 140 | benefits of both, writing regular expression <span class="emphasis"><em>grammars</em></span> |
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| 141 | in which some of the regular expressions are statically bound -- hard-coded |
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| 142 | and syntax-checked by the compiler -- and others are dynamically bound and |
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| 143 | specified at runtime. These regular expressions can refer to each other recursively, |
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| 144 | matching patterns in strings that ordinary regular expressions cannot. |
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| 145 | </p> |
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| 146 | <a name="boost_xpressive.preface.influences_and_related_work"></a><h2> |
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| 147 | <a name="id1953666"></a> |
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| 148 | Influences and Related Work |
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| 149 | </h2> |
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| 150 | <p> |
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| 151 | The design of xpressive's interface has been strongly influenced by John Maddock's |
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| 152 | <a href="../../libs/regex" target="_top">Boost.Regex</a> library and his <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2003/n1429.htm" target="_top">proposal</a> |
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| 153 | to add regular expressions to the Standard Library. I also drew a great deal |
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| 154 | of inspiration from Joel de Guzman's <a href="http://spirit.sourceforge.net" target="_top">Spirit |
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| 155 | Parser Framework</a>, which served as the model for static xpressive. Other |
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| 156 | sources of inspiration are the <a href="http://www.perl.com/pub/a/2002/06/04/apo5.html" target="_top">Perl |
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| 157 | 6</a> redesign and <a href="http://research.microsoft.com/projects/greta" target="_top">GRETA</a>. |
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| 158 | (You can read a summary of the changes Perl 6 will bring to regex culture |
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| 159 | <a href="http://dev.perl.org/perl6/doc/design/syn/S05.html" target="_top">here</a>.) |
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| 160 | </p> |
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| 161 | </div> |
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| 162 | </div> |
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| 163 | <table width="100%"><tr> |
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| 164 | <td align="left"><small><p>Last revised: July 16, 2007 at 17:52:22 GMT</p></small></td> |
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| 165 | <td align="right"><small></small></td> |
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| 166 | </tr></table> |
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