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<h1>char_separator<Char, Traits></h1>
<p>The <tt>char_separator</tt> class breaks a sequence of characters into
tokens based on character delimiters much in the same way that
<tt>strtok()</tt> does (but without all the evils of non-reentrancy and
destruction of the input sequence).</p>
<p>The <tt>char_separator</tt> class is used in conjunction with the
<a href="token_iterator.htm"><tt>token_iterator</tt></a> or <a href=
"tokenizer.htm"><tt>tokenizer</tt></a> to perform tokenizing.</p>
<h2>Definitions</h2>
<p>The <tt>strtok()</tt> function does not include matches with the
character delimiters in the output sequence of tokens. However, sometimes
it is useful to have the delimiters show up in the output sequence,
therefore <tt>char_separator</tt> provides this as an option. We refer to
delimiters that show up as output tokens as <b><i>kept delimiters</i></b>
and delimiters that do now show up as output tokens as <b><i>dropped
delimiters</i></b>.</p>
<p>When two delimiters appear next to each other in the input sequence,
there is the question of whether to output an <b><i>empty token</i></b> or
to skip ahead. The behaviour of <tt>strtok()</tt> is to skip ahead. The
<tt>char_separator</tt> class provides both options.</p>
<h2>Examples</h2>
<p>This first examples shows how to use <tt>char_separator</tt> as a
replacement for the <tt>strtok()</tt> function. We've specified three
character delimiters, and they will not show up as output tokens. We have
not specified any kept delimiters, and by default any empty tokens will be
ignored.</p>
<blockquote>
<pre>
// char_sep_example_1.cpp
#include <iostream>
#include <boost/tokenizer.hpp>
#include <string>
int main()
{
std::string str = ";;Hello|world||-foo--bar;yow;baz|";
typedef boost::tokenizer<boost::char_separator<char> >
tokenizer;
boost::char_separator<char> sep("-;|");
tokenizer tokens(str, sep);
for (tokenizer::iterator tok_iter = tokens.begin();
tok_iter != tokens.end(); ++tok_iter)
std::cout << "<" << *tok_iter << "> ";
std::cout << "\n";
return EXIT_SUCCESS;
}
</pre>
</blockquote>The output is:
<blockquote>
<pre>
<Hello> <world> <foo> <bar> <yow> <baz>
</pre>
</blockquote>
<p>The next example shows tokenizing with two dropped delimiters '-' and
';' and a single kept delimiter '|'. We also specify that empty tokens
should show up in the output when two delimiters are next to each
other.</p>
<blockquote>
<pre>
// char_sep_example_2.cpp
#include <iostream>
#include <boost/tokenizer.hpp>
#include <string>
int main()
{
std::string str = ";;Hello|world||-foo--bar;yow;baz|";
typedef boost::tokenizer<boost::char_separator<char> >
tokenizer;
boost::char_separator<char> sep("-;", "|", boost::keep_empty_tokens);
tokenizer tokens(str, sep);
for (tokenizer::iterator tok_iter = tokens.begin();
tok_iter != tokens.end(); ++tok_iter)
std::cout << "<" << *tok_iter << "> ";
std::cout << "\n";
return EXIT_SUCCESS;
}
</pre>
</blockquote>The output is:
<blockquote>
<pre>
<> <> <Hello> <|> <world> <|> <> <|> <> <foo> <> <bar> <yow> <baz> <|> <>
</pre>
</blockquote>
<p>The final example shows tokenizing on punctuation and whitespace
characters using the default constructor of the
<tt>char_separator</tt>.</p>
<blockquote>
<pre>
// char_sep_example_3.cpp
#include <iostream>
#include <boost/tokenizer.hpp>
#include <string>
int main()
{
std::string str = "This is, a test";
typedef boost::tokenizer<boost::char_separator<char> > Tok;
boost::char_separator<char> sep; // default constructed
Tok tok(str, sep);
for(Tok::iterator tok_iter = tok.begin(); tok_iter != tok.end(); ++tok_iter)
std::cout << "<" << *tok_iter << "> ";
std::cout << "\n";
return EXIT_SUCCESS;
}
</pre>
</blockquote>The output is:
<blockquote>
<pre>
<This> <is> <,> <a> <test>
</pre>
</blockquote>
<h2>Template parameters</h2>
<table border summary="">
<tr>
<th>Parameter</th>
<th>Description</th>
<th>Default</th>
</tr>
<tr>
<td><tt>Char</tt></td>
<td>The type of elements within a token, typically <tt>char</tt>.</td>
<td> </td>
</tr>
<tr>
<td><tt>Traits</tt></td>
<td>The <tt>char_traits</tt> for the character type.</td>
<td><tt>char_traits<char></tt></td>
</tr>
</table>
<h2>Model of</h2><a href="tokenizerfunction.htm">Tokenizer Function</a>
<h2>Members</h2>
<hr>
<pre>
explicit char_separator(const Char* dropped_delims,
const Char* kept_delims = "",
empty_token_policy empty_tokens = drop_empty_tokens)
</pre>
<p>This creates a <tt>char_separator</tt> object, which can then be used to
create a <a href="token_iterator.htm"><tt>token_iterator</tt></a> or
<a href="tokenizer.htm"><tt>tokenizer</tt></a> to perform tokenizing. The
<tt>dropped_delims</tt> and <tt>kept_delims</tt> are strings of characters
where each character is used as delimiter during tokenizing. Whenever a
delimiter is seen in the input sequence, the current token is finished, and
a new token begins. The delimiters in <tt>dropped_delims</tt> do not show
up as tokens in the output whereas the delimiters in <tt>kept_delims</tt>
do show up as tokens. If <tt>empty_tokens</tt> is
<tt>drop_empty_tokens</tt>, then empty tokens will not show up in the
output. If <tt>empty_tokens</tt> is <tt>keep_empty_tokens</tt> then empty
tokens will show up in the output.</p>
<hr>
<pre>
explicit char_separator()
</pre>
<p>The function <tt>std::isspace()</tt> is used to identify dropped
delimiters and <tt>std::ispunct()</tt> is used to identify kept delimiters.
In addition, empty tokens are dropped.</p>
<hr>
<pre>
template <typename InputIterator, typename Token>
bool operator()(InputIterator& next, InputIterator end, Token& tok)
</pre>
<p>This function is called by the <a href=
"token_iterator.htm"><tt>token_iterator</tt></a> to perform tokenizing. The
user typically does not call this function directly.</p>
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<p>Revised
<!--webbot bot="Timestamp" s-type="EDITED" s-format="%d %B, %Y" startspan -->25
December, 2006<!--webbot bot="Timestamp" endspan i-checksum="38518" --></p>
<p><i>Copyright © 2001-2002 Jeremy Siek and John R. Bandela</i></p>
<p><i>Distributed under 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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