
template <class Char, class Traits = std::char_traits<Char> >
class char_delimiters_separator{
The char_delimiters_separator class is an implementation of the TokenizerFunction concept that can be used to break text up into tokens. It is the default TokenizerFunction for tokenizer and token_iterator_generator. An example is below.
// simple_example_4.cpp
#include<iostream>
#include<boost/tokenizer.hpp>
#include<string>
int main(){
using namespace std;
using namespace boost;
string s = "This is, a test";
tokenizer<char_delimiters_separator<char> > tok(s);
for(tokenizer<char_delimiters_separator<char> >::iterator beg=tok.begin(); beg!=tok.end();++beg){
cout << *beg << "\n";
}
}
There is one constructor of interest. It is as follows
explicit char_delimiters_separator(bool return_delims = false, const Char* returnable = "",const Char* nonreturnable = "" )
|
Parameter |
Description |
| return_delims | Whether or not to return the delimiters that have been found. Note that not all delimiters can be returned. See the other two parameters for explanation. |
| returnable | This specifies the returnable delimiters. These are the delimiters that can be returned as tokens when return_delims is true. Since these are typically punctuation, if a 0 is provided as the argument, then the returnable delmiters will be all characters Cfor which std::ispunct(C) yields a true value. If an argument of "" is provided, then this is taken to mean that there are noreturnable delimiters. |
| nonreturnable | This specifies the nonreturnable delimiters. These are delimiters that cannot be returned as tokens. Since these are typically whitespace, if 0 is specified as an argument, then the nonreturnable delimiters will be all characters C for which std::isspace(C) yields a true value. If an argument of "" is provided, then this is taken to mean that there are no non-returnable delimiters. |
The reason there is a distinction between nonreturnable and returnable delimiters is that some delimiters are just used to split up tokens and are nothing more. Take for example the following string "b c +". Assume you are writing a simple calculator to parse expression in post fix notation. While both the space and the + separate tokens, you only only interested in the + and not in the space. Indeed having the space returned as a token would only complicate your code. In this case you would specify + as a returnable, and space as a nonreturnable delimiter.
To use this class, pass an object of it anywhere a TokenizerFunction object is required.
| Parameter | Description |
|---|---|
| Char | The type of the elements within a token, typically char. |
| Traits | The traits class for Char, typically std::char_traits<Char> |
Revised 25 December, 2006
Copyright © 2001 John R. Bandela
Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)