Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

Introduction

The boost Tokenizer package provides a flexible and easy to use way to break of a string or other character sequence into a series of tokens. Below is a simple example that will break up a phrase into words.

// 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";
   }
}

You can choose how the string gets broken up. You do this by specifying the TokenizerFunction. If you do not specify anything, the default TokenizerFunction is char_delimiters_separator<char> which defaults to breaking up a string based on space and punctuation. Here is an example of using another TokenizerFunction called escaped_list_separator. This TokenizerFunction parses a superset of comma separated value (csv) lines. The format looks like this

// 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";
   }
}

Finally, for some TokenizerFunctions you have to pass in something into the constructor in order to do anything interesting. An example is offset_separator. This class breaks a string into tokens based on offsets for example

12252001 when parsed using offsets of 2,2,4 becomes 12 25 2001. Below is an example to parse this.

// 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";
   }
}