1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<head> 4<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 5<title>Chapter 46. Boost.Xpressive</title> 6<link rel="stylesheet" href="../../doc/src/boostbook.css" type="text/css"> 7<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 8<link rel="home" href="index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> 9<link rel="up" href="libraries.html" title="Part I. The Boost C++ Libraries (BoostBook Subset)"> 10<link rel="prev" href="variant/refs.html" title="References"> 11<link rel="next" href="xpressive/user_s_guide.html" title="User's Guide"> 12</head> 13<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 14<table cellpadding="2" width="100%"><tr> 15<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../boost.png"></td> 16<td align="center"><a href="../../index.html">Home</a></td> 17<td align="center"><a href="../../libs/libraries.htm">Libraries</a></td> 18<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 19<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 20<td align="center"><a href="../../more/index.htm">More</a></td> 21</tr></table> 22<hr> 23<div class="spirit-nav"> 24<a accesskey="p" href="variant/refs.html"><img src="../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="libraries.html"><img src="../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="index.html"><img src="../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="xpressive/user_s_guide.html"><img src="../../doc/src/images/next.png" alt="Next"></a> 25</div> 26<div class="chapter"> 27<div class="titlepage"><div> 28<div><h2 class="title"> 29<a name="xpressive"></a>Chapter 46. Boost.Xpressive</h2></div> 30<div><div class="author"><h3 class="author"> 31<span class="firstname">Eric</span> <span class="surname">Niebler</span> 32</h3></div></div> 33<div><p class="copyright">Copyright © 2007 Eric Niebler</p></div> 34<div><div class="legalnotice"> 35<a name="xpressive.legal"></a><p> 36 Distributed under the Boost Software License, Version 1.0. (See accompanying 37 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>) 38 </p> 39</div></div> 40</div></div> 41<div class="toc"> 42<p><b>Table of Contents</b></p> 43<dl class="toc"> 44<dt><span class="section"><a href="xpressive.html#boost_xpressive.preface">Preface</a></span></dt> 45<dt><span class="section"><a href="xpressive/user_s_guide.html">User's Guide</a></span></dt> 46<dd><dl> 47<dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.introduction">Introduction</a></span></dt> 48<dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.installing_xpressive">Installing 49 xpressive</a></span></dt> 50<dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.quick_start">Quick Start</a></span></dt> 51<dt><span class="section"><a href="xpressive/user_s_guide.html#xpressive.user_s_guide.creating_a_regex_object">Creating 52 a Regex Object</a></span></dt> 53<dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.matching_and_searching">Matching 54 and Searching</a></span></dt> 55<dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.accessing_results">Accessing 56 Results</a></span></dt> 57<dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.string_substitutions">String 58 Substitutions</a></span></dt> 59<dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.string_splitting_and_tokenization">String 60 Splitting and Tokenization</a></span></dt> 61<dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.named_captures">Named Captures</a></span></dt> 62<dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.grammars_and_nested_matches">Grammars 63 and Nested Matches</a></span></dt> 64<dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.semantic_actions_and_user_defined_assertions">Semantic 65 Actions and User-Defined Assertions</a></span></dt> 66<dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.symbol_tables_and_attributes">Symbol 67 Tables and Attributes</a></span></dt> 68<dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.localization_and_regex_traits">Localization 69 and Regex Traits</a></span></dt> 70<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> 71<dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.concepts">Concepts</a></span></dt> 72<dt><span class="section"><a href="xpressive/user_s_guide.html#boost_xpressive.user_s_guide.examples">Examples</a></span></dt> 73</dl></dd> 74<dt><span class="section"><a href="xpressive/reference.html">Reference</a></span></dt> 75<dd><dl> 76<dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.basic_regex_hpp">Header <boost/xpressive/basic_regex.hpp></a></span></dt> 77<dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.match_results_hpp">Header <boost/xpressive/match_results.hpp></a></span></dt> 78<dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.regex_actions_hpp">Header <boost/xpressive/regex_actions.hpp></a></span></dt> 79<dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.regex_algorithms_hpp">Header <boost/xpressive/regex_algorithms.hpp></a></span></dt> 80<dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.regex_compiler_hpp">Header <boost/xpressive/regex_compiler.hpp></a></span></dt> 81<dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.regex_constants_hpp">Header <boost/xpressive/regex_constants.hpp></a></span></dt> 82<dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.regex_error_hpp">Header <boost/xpressive/regex_error.hpp></a></span></dt> 83<dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.regex_iterator_hpp">Header <boost/xpressive/regex_iterator.hpp></a></span></dt> 84<dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.regex_primitives_hpp">Header <boost/xpressive/regex_primitives.hpp></a></span></dt> 85<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> 86<dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.regex_traits_hpp">Header <boost/xpressive/regex_traits.hpp></a></span></dt> 87<dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.sub_match_hpp">Header <boost/xpressive/sub_match.hpp></a></span></dt> 88<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> 89<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> 90<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> 91<dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.xpressive_hpp">Header <boost/xpressive/xpressive.hpp></a></span></dt> 92<dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.xpressive_dynamic_hpp">Header <boost/xpressive/xpressive_dynamic.hpp></a></span></dt> 93<dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.xpressive_fwd_hpp">Header <boost/xpressive/xpressive_fwd.hpp></a></span></dt> 94<dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.xpressive_static_hpp">Header <boost/xpressive/xpressive_static.hpp></a></span></dt> 95<dt><span class="section"><a href="xpressive/reference.html#header.boost.xpressive.xpressive_typeof_hpp">Header <boost/xpressive/xpressive_typeof.hpp></a></span></dt> 96</dl></dd> 97<dt><span class="section"><a href="boost_xpressive/acknowledgments.html">Acknowledgments</a></span></dt> 98<dt><span class="section"><a href="xpressive/appendices.html">Appendices</a></span></dt> 99<dd><dl> 100<dt><span class="section"><a href="xpressive/appendices.html#boost_xpressive.appendices.appendix_1__history">Appendix 101 1: History</a></span></dt> 102<dt><span class="section"><a href="xpressive/appendices.html#boost_xpressive.appendices.appendix_2__not_yet_implemented">Appendix 103 2: Not Yet Implemented</a></span></dt> 104<dt><span class="section"><a href="xpressive/appendices.html#boost_xpressive.appendices.appendix_3__differences_from_boost_regex">Appendix 105 3: Differences from Boost.Regex</a></span></dt> 106<dt><span class="section"><a href="xpressive/appendices.html#boost_xpressive.appendices.perf">Appendix 4: Performance 107 Comparison</a></span></dt> 108<dt><span class="section"><a href="xpressive/appendices.html#xpressive.appendices.appendix_5__implementation_notes">Appendix 109 5: Implementation Notes</a></span></dt> 110</dl></dd> 111</dl> 112</div> 113<div class="section"> 114<div class="titlepage"><div><div><h2 class="title" style="clear: both"> 115<a name="boost_xpressive.preface"></a><a class="link" href="xpressive.html#boost_xpressive.preface" title="Preface">Preface</a> 116</h2></div></div></div> 117<div class="blockquote"><blockquote class="blockquote"><p> 118 <span class="emphasis"><em>Wife:</em></span> New Shimmer is a floor wax!<br> <span class="emphasis"><em>Husband:</em></span> 119 No, new Shimmer is a dessert topping!<br> <span class="emphasis"><em>Wife:</em></span> It's 120 a floor wax!<br> <span class="emphasis"><em>Husband:</em></span> It's a dessert topping!<br> 121 <span class="emphasis"><em>Wife:</em></span> It's a floor wax, I'm telling you!<br> <span class="emphasis"><em>Husband:</em></span> 122 It's a dessert topping, you cow!<br> <span class="emphasis"><em>Announcer:</em></span> Hey, 123 hey, hey, calm down, you two. New Shimmer is both a floor wax <span class="emphasis"><em>and</em></span> 124 a dessert topping! 125 </p></blockquote></div> 126<div class="blockquote"><blockquote class="blockquote"><p> 127 <span class="bold"><strong><span class="emphasis"><em>-- Saturday Night Live</em></span></strong></span> 128 </p></blockquote></div> 129<h3> 130<a name="boost_xpressive.preface.h0"></a> 131 <span class="phrase"><a name="boost_xpressive.preface.description"></a></span><a class="link" href="xpressive.html#boost_xpressive.preface.description">Description</a> 132 </h3> 133<p> 134 xpressive is an advanced, object-oriented regular expression template library 135 for C++. Regular expressions can be written as strings that are parsed at run-time, 136 or as expression templates that are parsed at compile-time. Regular expressions 137 can refer to each other and to themselves recursively, allowing you to build 138 arbitrarily complicated grammars out of them. 139 </p> 140<h3> 141<a name="boost_xpressive.preface.h1"></a> 142 <span class="phrase"><a name="boost_xpressive.preface.motivation"></a></span><a class="link" href="xpressive.html#boost_xpressive.preface.motivation">Motivation</a> 143 </h3> 144<p> 145 If you need to manipulate text in C++, you have typically had two disjoint 146 options: a regular expression engine or a parser generator. Regular expression 147 engines (like <a href="../../libs/regex" target="_top">Boost.Regex</a>) are powerful 148 and flexible; patterns are represented as strings which can be specified at 149 runtime. However, that means that syntax errors are likewise not detected until 150 runtime. Also, regular expressions are ill-suited to advanced text processing 151 tasks such as matching balanced, nested tags. Those tasks have traditionally 152 been handled by parser generators (like the <a href="http://spirit.sourceforge.net" target="_top">Spirit 153 Parser Framework</a>). These beasts are more powerful but less flexible. 154 They generally don't allow you to arbitrarily modify your grammar rules on 155 the fly. In addition, they don't have the exhaustive backtracking semantics 156 of regular expressions, which can make it more challenging to author some types 157 of patterns. 158 </p> 159<p> 160 xpressive brings these two approaches seamlessly together and occupies a unique 161 niche in the world of C++ text processing. With xpressive, you can choose to 162 use it much as you would use <a href="../../libs/regex" target="_top">Boost.Regex</a>, 163 representing regular expressions as strings. Or you can use it as you would 164 use <a href="http://spirit.sourceforge.net" target="_top">Spirit</a>, writing your 165 regexes as C++ expressions, enjoying all the benefits of an embedded language 166 dedicated to text manipulation. What's more, you can mix the two to get the 167 benefits of both, writing regular expression <span class="emphasis"><em>grammars</em></span> 168 in which some of the regular expressions are statically bound -- hard-coded 169 and syntax-checked by the compiler -- and others are dynamically bound and 170 specified at runtime. These regular expressions can refer to each other recursively, 171 matching patterns in strings that ordinary regular expressions cannot. 172 </p> 173<h3> 174<a name="boost_xpressive.preface.h2"></a> 175 <span class="phrase"><a name="boost_xpressive.preface.influences_and_related_work"></a></span><a class="link" href="xpressive.html#boost_xpressive.preface.influences_and_related_work">Influences 176 and Related Work</a> 177 </h3> 178<p> 179 The design of xpressive's interface has been strongly influenced by John Maddock's 180 <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> 181 to add regular expressions to the Standard Library. I also drew a great deal 182 of inspiration from Joel de Guzman's <a href="http://spirit.sourceforge.net" target="_top">Spirit 183 Parser Framework</a>, which served as the model for static xpressive. Other 184 sources of inspiration are the <a href="http://www.perl.com/pub/a/2002/06/04/apo5.html" target="_top">Perl 185 6</a> redesign and <a href="http://research.microsoft.com/projects/greta" target="_top">GRETA</a>. 186 (You can read a summary of the changes Perl 6 will bring to regex culture 187 <a href="http://dev.perl.org/perl6/doc/design/syn/S05.html" target="_top">here</a>.) 188 </p> 189</div> 190</div> 191<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 192<td align="left"><p><small>Last revised: August 11, 2020 at 15:03:11 GMT</small></p></td> 193<td align="right"><div class="copyright-footer"></div></td> 194</tr></table> 195<hr> 196<div class="spirit-nav"> 197<a accesskey="p" href="variant/refs.html"><img src="../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="libraries.html"><img src="../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="index.html"><img src="../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="xpressive/user_s_guide.html"><img src="../../doc/src/images/next.png" alt="Next"></a> 198</div> 199</body> 200</html> 201
