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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<title>Boost.Regex: Algorithm regex_search</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<LINK href="../../../boost.css" type="text/css" rel="stylesheet"></head>
<body>
<P>
<TABLE id="Table1" cellSpacing="1" cellPadding="1" width="100%" border="0">
<TR>
<td vAlign="top" width="300">
<h3><A href="../../../index.htm"><IMG height="86" alt="C++ Boost" src="../../../boost.png" width="277" border="0"></A></h3>
</td>
<TD width="353">
<H1 align="center">Boost.Regex</H1>
<H2 align="center">Algorithm regex_search</H2>
</TD>
<td width="50">
<h3><A href="index.html"><IMG height="45" alt="Boost.Regex Index" src="uarrow.gif" width="43" border="0"></A></h3>
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</P>
<HR>
<H3>Contents</H3>
<dl class="index">
<dt><A href="#synopsis">Synopsis</A> <dt><a href="#description">Description</a> <dt><A href="#examples">
Examples</A></dt></dl>
<H3><A name="synopsis"></A>Synopsis</H3>
<PRE>#include <<A href="../../../boost/regex.hpp">boost/regex.hpp</A>> </PRE>
<P></P>
<P>The algorithm regex_search will search a range denoted by a pair of
bidirectional-iterators for a given regular expression. The algorithm uses
various heuristics to reduce the search time by only checking for a match if a
match could conceivably start at that position. The algorithm is defined as
follows:
<PRE>template <class BidirectionalIterator,
class Allocator, class charT,
class traits, class Allocator2>
bool <A href="#f1">regex_search</A>(BidirectionalIterator first, BidirectionalIterator last,
<a href="match_results.html">match_results</a><BidirectionalIterator, Allocator>& m,
const <a href="basic_regex.html">basic_regex</a><charT, traits, Allocator2>& e,
<a href="match_flag_type.html">match_flag_type</a> flags = match_default);
template <class ST, class SA,
class Allocator, class charT,
class traits, class Allocator2>
bool <A href="#f2">regex_search</A>(const basic_string<charT, ST, SA>& s,
<a href="match_results.html">match_results</a><
typename basic_string<charT, ST,SA>::const_iterator,
Allocator>& m,
const <a href="basic_regex.html">basic_regex</a><charT, traits, Allocator2>& e,
<a href="match_flag_type.html">match_flag_type</a> flags = match_default);
template<class charT, class Allocator, class traits,
class Allocator2>
bool <A href="#f3">regex_search</A>(const charT* str,
<a href="match_results.html">match_results</a><const charT*, Allocator>& m,
const <a href="basic_regex.html">basic_regex</a><charT, traits, Allocator2>& e,
<a href="match_flag_type.html">match_flag_type</a> flags = match_default);
template <class BidirectionalIterator, class Allocator,
class charT, class traits>
bool <A href="#f4">regex_search</A>(BidirectionalIterator first, BidirectionalIterator last,
const <a href="basic_regex.html">basic_regex</a><charT, traits, Allocator>& e,
<a href="match_flag_type.html">match_flag_type</a> flags = match_default);
template <class charT, class Allocator,
class traits>
bool <A href="#f5">regex_search</A>(const charT* str,
const <a href="basic_regex.html">basic_regex</a><charT, traits, Allocator>& e,
<a href="match_flag_type.html">match_flag_type</a> flags = match_default);
template<class ST, class SA,
class Allocator, class charT,
class traits>
bool <A href="#f6">regex_search</A>(const basic_string<charT, ST, SA>& s,
const <a href="basic_regex.html">basic_regex</a><charT, traits, Allocator>& e,
<a href="match_flag_type.html">match_flag_type</a> flags = match_default);
</PRE>
<H3><A name="description"></A>Description</H3>
<PRE><A name=f1></A>template <class BidirectionalIterator, class Allocator, class charT,
class traits, class Allocator2>
bool regex_search(BidirectionalIterator first, BidirectionalIterator last,
<a href="match_results.html">match_results</a><BidirectionalIterator, Allocator>& m,
const <a href="basic_regex.html">basic_regex</a><charT, traits, Allocator2>& e,
<a href="match_flag_type.html">match_flag_type</a> flags = match_default);</PRE>
<P><B> Requires:</B> Type BidirectionalIterator meets the requirements of a
Bidirectional Iterator (24.1.4).</P>
<P><B> Effects: </B>Determines whether there is some sub-sequence within
[first,last) that matches the regular expression <I>e</I>, parameter <I>flags</I>
is used to control how the expression is matched against the character
sequence. Returns true if such a sequence exists, false otherwise.</P>
<P><STRONG>Throws:</STRONG> <CODE>std::runtime_error</CODE> if the complexity of
matching the expression against an N character string begins to exceed O(N<SUP>2</SUP>),
or if the program runs out of stack space while matching the expression (if
Boost.regex is <A href="configuration.html">configured</A> in recursive mode),
or if the matcher exhausts it's permitted memory allocation (if Boost.regex is <A href="configuration.html">
configured</A> in non-recursive mode).</P>
<P><B> Postconditions: </B>If the function returns false, then the effect on
parameter <I>m</I> is undefined, otherwise the effects on parameter <I>m</I> are
given in the table:</P>
<DIV align="center">
<CENTER>
<TABLE id="Table2" cellSpacing="1" cellPadding="7" width="624" border="1">
<TR>
<TD vAlign="top" width="50%">
<P><B> Element</B></P>
</TD>
<TD vAlign="top" width="50%">
<P><B> Value</B>
</P>
</TD>
</TR>
<TR>
<TD vAlign="top" width="50%">
<P>m.size()</P>
</TD>
<TD vAlign="top" width="50%">
<P>e.mark_count()</P>
</TD>
</TR>
<TR>
<TD vAlign="top" width="50%">
<P>m.empty()</P>
</TD>
<TD vAlign="top" width="50%">
<P>false</P>
</TD>
</TR>
<TR>
<TD vAlign="top" width="50%">
<P>m.prefix().first</P>
</TD>
<TD vAlign="top" width="50%">
<P>first</P>
</TD>
</TR>
<TR>
<TD vAlign="top" width="50%">
<P>m.prefix().last</P>
</TD>
<TD vAlign="top" width="50%">
<P>m[0].first</P>
</TD>
</TR>
<TR>
<TD vAlign="top" width="50%">
<P>m.prefix().matched</P>
</TD>
<TD vAlign="top" width="50%">
<P>m.prefix().first != m.prefix().second</P>
</TD>
</TR>
<TR>
<TD vAlign="top" width="50%">
<P>m.suffix().first</P>
</TD>
<TD vAlign="top" width="50%">
<P>m[0].second</P>
</TD>
</TR>
<TR>
<TD vAlign="top" width="50%">
<P>m.suffix().last</P>
</TD>
<TD vAlign="top" width="50%">
<P>last</P>
</TD>
</TR>
<TR>
<TD vAlign="top" width="50%">
<P>m.suffix().matched</P>
</TD>
<TD vAlign="top" width="50%">
<P>m.suffix().first != m.suffix().second</P>
</TD>
</TR>
<TR>
<TD vAlign="top" width="50%">
<P>m[0].first</P>
</TD>
<TD vAlign="top" width="50%">
<P>The start of the sequence of characters that matched the regular expression</P>
</TD>
</TR>
<TR>
<TD vAlign="top" width="50%">
<P>m[0].second</P>
</TD>
<TD vAlign="top" width="50%">
<P>The end of the sequence of characters that matched the regular expression</P>
</TD>
</TR>
<TR>
<TD vAlign="top" width="50%">
<P>m[0].matched</P>
</TD>
<TD vAlign="top" width="50%">
<P><CODE> true</CODE> if a full match was found, and <CODE>false</CODE> if it was
a partial match (found as a result of the <CODE>match_partial</CODE> flag being
set).</P>
</TD>
</TR>
<TR>
<TD vAlign="top" width="50%">
<P>m[n].first</P>
</TD>
<TD vAlign="top" width="50%">
<P>For all integers n < m.size(), the start of the sequence that matched
sub-expression <I>n</I>. Alternatively, if sub-expression n did not participate
in the match, then <I>last</I>.</P>
</TD>
</TR>
<TR>
<TD vAlign="top" width="50%">
<P>m[n].second</P>
</TD>
<TD vAlign="top" width="50%">
<P>For all integers n < m.size(), the end of the sequence that matched
sub-expression <I>n</I>. Alternatively, if sub-expression n did not participate
in the match, then <I>last</I>.</P>
</TD>
</TR>
<TR>
<TD vAlign="top" width="50%">
<P>m[n].matched</P>
</TD>
<TD vAlign="top" width="50%">
<P>For all integers n < m.size(), true if sub-expression <I>n</I> participated
in the match, false otherwise.</P>
</TD>
</TR>
</TD></TR></TABLE>
</CENTER>
</DIV>
<PRE><A name=f2></A>template <class charT, class Allocator, class traits, class Allocator2>
bool regex_search(const charT* str, <a href="match_results.html">match_results</a><const charT*, Allocator>& m,
const <a href="basic_regex.html">basic_regex</a><charT, traits, Allocator2>& e,
<a href="match_flag_type.html">match_flag_type</a> flags = match_default);</PRE>
<P><B> Effects:</B> Returns the result of <CODE>regex_search(str, str +
char_traits<charT>::length(str), m, e, flags)</CODE>.</P>
<PRE><A name=f3></A>template <class ST, class SA, class Allocator, class charT,
class traits, class Allocator2>
bool regex_search(const basic_string<charT, ST, SA>& s,
<a href="match_results.html">match_results</a><typename basic_string<charT, ST, SA>::const_iterator, Allocator>& m,
const <a href="basic_regex.html">basic_regex</a><charT, traits, Allocator2>& e,
<a href="match_flag_type.html">match_flag_type</a> flags = match_default);</PRE>
<P><B> Effects:</B> Returns the result of <CODE>regex_search(s.begin(), s.end(), m,
e, flags)</CODE>.</P>
<PRE><A name=f4></A>template <class iterator, class Allocator, class charT,
class traits>
bool regex_search(iterator first, iterator last,
const <a href="basic_regex.html">basic_regex</a><charT, traits, Allocator>& e,
<a href="match_flag_type.html">match_flag_type</a> flags = match_default);</PRE>
<P><B> Effects:</B> Behaves "as if" by constructing an instance of <CODE><a href="match_results.html">
match_results</a><</CODE>BidirectionalIterator<CODE>> what</CODE>,
and then returning the result of <CODE>regex_search(first, last, what, e, flags)</CODE>.</P>
<PRE><A name=f5></A>template <class charT, class Allocator, class traits>
bool regex_search(const charT* str
const <a href="basic_regex.html">basic_regex</a><charT, traits, Allocator>& e,
<a href="match_flag_type.html">match_flag_type</a> flags = match_default);</PRE>
<P><B> Effects:</B> Returns the result of <CODE>regex_search(str, str +
char_traits<charT>::length(str), e, flags)</CODE>.</P>
<PRE><A name=f6></A>template <class ST, class SA, class Allocator, class charT,
class traits>
bool regex_search(const basic_string<charT, ST, SA>& s,
const <a href="basic_regex.html">basic_regex</a><charT, traits, Allocator>& e,
<a href="match_flag_type.html">match_flag_type</a> flags = match_default);</PRE>
<P><B> Effects:</B> Returns the result of <CODE>regex_search(s.begin(), s.end(), e,
flags)</CODE>.
<H3><A name="examples"></A>Examples</H3>
<P>The following <A href="../example/snippets/regex_search_example.cpp">example</A>,
takes the contents of a file in the form of a string, and searches for all the
C++ class declarations in the file. The code will work regardless of the way
that std::string is implemented, for example it could easily be modified to
work with the SGI rope class, which uses a non-contiguous storage strategy.</P>
<P></P>
<PRE><FONT color=#008000>#include <string>
#include <map>
#include <boost/regex.hpp>
</FONT><FONT color=#000080><I>
// purpose:
// takes the contents of a file in the form of a string
// and searches for all the C++ class definitions, storing
// their locations in a map of strings/int's
</I></FONT><B>typedef</B> std::map<std::string, <B>int</B>, std::less<std::string> > map_type;
boost::regex expression("^(template[[:space:]]*<[^;:{]+>[[:space:]]*)?(class|struct)[[:space:]]*(\\<\\w+\\>([[:blank:]]*\\([^)]*\\))?[[:space:]]*)*(\\<\\w*\\>)[[:space:]]*(<[^;:{]+>[[:space:]]*)?(\\{|:[^;\\{()]*\\{)");
<B>
void</B> IndexClasses(map_type& m, <B>const</B> std::string& file)
{
std::string::const_iterator start, end;
start = file.begin();
end = file.end();
boost::<a href="match_results.html">match_results</a><std::string::const_iterator> what;
boost::match_flag_type flags = boost::match_default;
<B>while</B>(regex_search(start, end, what, expression, flags))
{
<FONT color=#000080> <I>// what[0] contains the whole string
</I> <I>// what[5] contains the class name.
</I> <I>// what[6] contains the template specialisation if any.
</I> <I>// add class name and position to map:
</I></FONT> m[std::string(what[5].first, what[5].second) + std::string(what[6].first, what[6].second)] =
what[5].first - file.begin();
<FONT color=#000080><I>// update search position:
</I></FONT> start = what[0].second;
<FONT color=#000080><I>// update flags:
</I></FONT> flags |= boost::match_prev_avail;
flags |= boost::match_not_bob;
}
}
</PRE>
<HR>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
04 Feb 2004
<!--webbot bot="Timestamp" endspan i-checksum="39359" --></p>
<p><i> Copyright John Maddock 1998-
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%Y" startspan --> 2004<!--webbot bot="Timestamp" endspan i-checksum="39359" --></i></p>
<P><I>Use, modification and distribution are subject to the Boost Software License,
Version 1.0. (See accompanying file <A href="../../../LICENSE_1_0.txt">LICENSE_1_0.txt</A>
or copy at <A href="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</A>)</I></P>
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