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 Hu Chunming
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<head>
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<meta name="GENERATOR" content="Microsoft FrontPage 6.0">
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<title>Introduction</title>
</head>
<body bgcolor="#FFFFFF">
<p><img src="../../../boost.png" alt="C++ Boost" width="277" height=
"86"/><br></p>
<h1 align="center">Introduction</h1>
<p align="left">The Boost Tokenizer package provides a flexible and
easy-to-use way to break a string or other character sequence into a series
of tokens. Below is a simple example that will break up a phrase into
words.</p>
<div align="left">
<pre>
// simple_example_1.cpp
#include<iostream>
#include<boost/tokenizer.hpp>
#include<string>
int main(){
using namespace std;
using namespace boost;
string s = "This is, a test";
tokenizer<> tok(s);
for(tokenizer<>::iterator beg=tok.begin(); beg!=tok.end();++beg){
cout << *beg << "\n";
}
}
</pre>
</div>
<p align="left">You can choose how the string gets parsed by using the
TokenizerFunction. If you do not specify anything, the default
TokenizerFunction is <em>char_delimiters_separator<char></em> which
defaults to breaking up a string based on space and punctuation. Here is an
example using another TokenizerFunction called
<em>escaped_list_separator</em>. This TokenizerFunction parses a superset
of comma-separated value (CSV) lines. The format looks like this:</p>
<p align="left">Field 1,"putting quotes around fields, allows commas",Field
3</p>
<p align="left">Below is an example that will break the previous line into
its three fields.</p>
<div align="left">
<pre>
// simple_example_2.cpp
#include<iostream>
#include<boost/tokenizer.hpp>
#include<string>
int main(){
using namespace std;
using namespace boost;
string s = "Field 1,\"putting quotes around fields, allows commas\",Field 3";
tokenizer<escaped_list_separator<char> > tok(s);
for(tokenizer<escaped_list_separator<char> >::iterator beg=tok.begin(); beg!=tok.end();++beg){
cout << *beg << "\n";
}
}
</pre>
</div>
<p align="left">Finally, for some TokenizerFunctions you have to pass
something into the constructor in order to do anything interesting. An
example is the offset_separator. This class breaks a string into tokens based
on offsets. For example, when <em>12252001</em> is parsed using offsets of
2,2,4 it becomes <em>12 25 2001</em>. Below is the code used.</p>
<div align="left">
<pre>
// simple_example_3.cpp
#include<iostream>
#include<boost/tokenizer.hpp>
#include<string>
int main(){
using namespace std;
using namespace boost;
string s = "12252001";
int offsets[] = {2,2,4};
offset_separator f(offsets, offsets+3);
tokenizer<offset_separator> tok(s,f);
for(tokenizer<offset_separator>::iterator beg=tok.begin(); beg!=tok.end();++beg){
cout << *beg << "\n";
}
}
</pre>
</div>
<p align="left"> </p>
<hr>
<p><a href="http://validator.w3.org/check?uri=referer"><img border="0" src=
"../../doc/images/valid-html401.png" alt="Valid HTML 4.01 Transitional"
height="31" width="88"></a></p>
<p>Revised
<!--webbot bot="Timestamp" s-type="EDITED" s-format="%d %B %Y" startspan -->9 June 2010<!--webbot bot="Timestamp" endspan i-checksum="38518" --></p>
<p><i>Copyright © 2001 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>
</body>
</html>
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