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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<title>Boost.Regex: Algorithm regex_split (deprecated)</title>
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<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../boost.png" border="0"></a></h3>
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<H1 align="center">Boost.Regex</H1>
<H2 align="center">Algorithm regex_split (deprecated)</H2>
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<P>The algorithm regex_split has been deprecated in favor of the iterator <A href="regex_token_iterator.html">
regex_token_iterator</A> which has a more flexible and powerful interface,
as well as following the more usual standard library "pull" rather than "push"
semantics.</P>
<P>Code which uses regex_split will continue to compile, the following
documentation is taken from the previous boost.regex version:</P>
<H3><A name="regex_split"></A>Algorithm regex_split</H3>
<PRE>#include <<A href="../../../boost/regex.hpp">boost/regex.hpp</A>> </PRE>
<P>Algorithm regex_split performs a similar operation to the perl split operation,
and comes in three overloaded forms:
</P>
<PRE><B>template</B> <<B>class</B> OutputIterator, <B>class</B> charT, <B>class</B> Traits1, <B>class</B> Alloc1, <B>class</B> Traits2, <B>class</B> Alloc2>
std::size_t regex_split(OutputIterator out,
std::basic_string<charT, Traits1, Alloc1>& s,
<B> const</B> basic_regex<charT, Traits2, Alloc2>& e,
<STRONG> </STRONG>boost::match_flag_type flags,
std::size_t max_split);
<B>template</B> <<B>class</B> OutputIterator, <B>class</B> charT, <B>class</B> Traits1, <B>class</B> Alloc1, <B>class</B> Traits2, <B>class</B> Alloc2>
std::size_t regex_split(OutputIterator out,
std::basic_string<charT, Traits1, Alloc1>& s,
<B> const</B> basic_regex<charT, Traits2, Alloc2>& e,
boost::match_flag_type flags = match_default);
<B>template</B> <<B>class</B> OutputIterator, <B>class</B> charT, <B>class</B> Traits1, <B>class</B> Alloc1>
std::size_t regex_split(OutputIterator out,
std::basic_string<charT, Traits1, Alloc1>& s);</PRE>
<P><STRONG>Effects: </STRONG>Each version of the algorithm takes an
output-iterator for output, and a string for input. If the expression contains
no marked sub-expressions, then the algorithm writes one string onto the
output-iterator for each section of input that does not match the expression.
If the expression does contain marked sub-expressions, then each time a match
is found, one string for each marked sub-expression will be written to the
output-iterator. No more than <I>max_split </I>strings will be written to the
output-iterator. Before returning, all the input processed will be deleted from
the string <I>s</I> (if <I>max_split </I>is not reached then all of <I>s</I> will
be deleted). Returns the number of strings written to the output-iterator. If
the parameter <I>max_split</I> is not specified then it defaults to UINT_MAX.
If no expression is specified, then it defaults to "\s+", and splitting occurs
on whitespace.
</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><A href="../example/snippets/regex_split_example_1.cpp">Example</A>: the
following function will split the input string into a series of tokens, and
remove each token from the string <I>s</I>:
</P>
<PRE><B>unsigned</B> tokenise(std::list<std::string>& l, std::string& s)
{
<B> return</B> boost::regex_split(std::back_inserter(l), s);
}</PRE>
<P><A href="../example/snippets/regex_split_example_2.cpp">Example</A>: the
following short program will extract all of the URL's from a html file, and
print them out to <I>cout</I>:
</P>
<PRE><FONT color=#008000>#include <list>
#include <fstream>
#include <iostream>
#include <boost/regex.hpp>
</FONT>
boost::regex e(<FONT color=#000080>"<\\s*A\\s+[^>]*href\\s*=\\s*\"([^\"]*)\""</FONT>,
boost::regbase::normal | boost::regbase::icase);
<B>void</B> load_file(std::string& s, std::istream& is)
{
s.erase();
<FONT color=#000080>//
// attempt to grow string buffer to match file size,
// this doesn't always work...
</FONT> s.reserve(is.rdbuf()-&gtin_avail());
<B>char</B> c;
<B>while</B>(is.get(c))
{
<FONT color=#000080>// use logarithmic growth stategy, in case
// in_avail (above) returned zero:
</FONT> <B>if</B>(s.capacity() == s.size())
s.reserve(s.capacity() * 3);
s.append(1, c);
}
}
<B>int</B> main(<B>int</B> argc, <B>char</B>** argv)
{
std::string s;
std::list<std::string> l;
<B>for</B>(<B>int</B> i = 1; i < argc; ++i)
{
std::cout << <FONT color=#000080>"Findings URL's in "</FONT> << argv[i] << <FONT color=#000080>":"</FONT> << std::endl;
s.erase();
std::ifstream is(argv[i]);
load_file(s, is);
boost::regex_split(std::back_inserter(l), s, e);
<B>while</B>(l.size())
{
s = *(l.begin());
l.pop_front();
std::cout << s << std::endl;
}
}
<B>return</B> 0;
}</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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