[/ 
  Copyright 2006-2007 John Maddock.
  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).
]


[section:regex_token_iterator regex_token_iterator]

The template class [regex_token_iterator] is an iterator adapter; that is to 
say it represents a new view of an existing iterator sequence, 
by enumerating all the occurrences of a regular expression within that 
sequence, and presenting one or more character sequence for each match found. 
Each position enumerated by the iterator is a [sub_match] object that represents 
what matched a particular sub-expression within the regular expression. 
When class [regex_token_iterator] is used to enumerate a single sub-expression 
with index -1, then the iterator performs field splitting: that is 
to say it enumerates one character sequence for each section of the character 
container sequence that does not match the regular expression specified.

   template <class BidirectionalIterator, 
            class charT = iterator_traits<BidirectionalIterator>::value_type,
            class traits = regex_traits<charT> >
   class regex_token_iterator 
   {
   public:
      typedef          basic_regex<charT, traits>                              regex_type;
      typedef          sub_match<BidirectionalIterator>                        value_type;
      typedef typename iterator_traits<BidirectionalIterator>::difference_type difference_type;
      typedef          const value_type*                                       pointer;
      typedef          const value_type&                                       reference;
      typedef          std::forward_iterator_tag                               iterator_category;
      
      ``[link boost_regex.regex_token_iterator.construct1 regex_token_iterator]``();
      ``[link boost_regex.regex_token_iterator.construct2 regex_token_iterator]``(BidirectionalIterator a, 
                           BidirectionalIterator b, 
                           const regex_type& re, 
                           int submatch = 0, 
                           match_flag_type m = match_default);
      ``[link boost_regex.regex_token_iterator.construct3 regex_token_iterator]``(BidirectionalIterator a, 
                           BidirectionalIterator b, 
                           const regex_type& re, 
                           const std::vector<int>& submatches, 
                           match_flag_type m = match_default);
      template <std::size_t N>
      ``[link boost_regex.regex_token_iterator.construct4 regex_token_iterator]``(BidirectionalIterator a, 
                           BidirectionalIterator b, 
                           const regex_type& re, 
                           const int (&submatches)[N], 
                           match_flag_type m = match_default);
      ``[link boost_regex.regex_token_iterator.construct5 regex_token_iterator]``(const regex_token_iterator&);
      regex_token_iterator& ``[link boost_regex.regex_token_iterator.assign operator=]``(const regex_token_iterator&);
      bool ``[link boost_regex.regex_token_iterator.op_eq operator==]``(const regex_token_iterator&)const;
      bool ``[link boost_regex.regex_token_iterator.op_ne operator!=]``(const regex_token_iterator&)const;
      const value_type& ``[link boost_regex.regex_token_iterator.op_deref operator*]``()const;
      const value_type* ``[link boost_regex.regex_token_iterator.op_arrow operator->]``()const;
      regex_token_iterator& ``[link boost_regex.regex_token_iterator.op_inc1 operator++]``();
      regex_token_iterator ``[link boost_regex.regex_token_iterator.op_inc2 operator++]``(int);
   };

   typedef regex_token_iterator<const char*>                   cregex_token_iterator;
   typedef regex_token_iterator<std::string::const_iterator>   sregex_token_iterator;
   #ifndef BOOST_NO_WREGEX
   typedef regex_token_iterator<const wchar_t*>                wcregex_token_iterator;
   typedef regex_token_iterator<<std::wstring::const_iterator> wsregex_token_iterator;
   #endif

   template <class charT, class traits>
   regex_token_iterator<const charT*, charT, traits> 
      ``[link boost_regex.regex_token_iterator.make make_regex_token_iterator]``(
            const charT* p, 
            const basic_regex<charT, traits>& e, 
            int submatch = 0, 
            regex_constants::match_flag_type m = regex_constants::match_default);
                                
   template <class charT, class traits, class ST, class SA>
   regex_token_iterator<typename std::basic_string<charT, ST, SA>::const_iterator, charT, traits> 
      ``[link boost_regex.regex_token_iterator.make make_regex_token_iterator]``(
            const std::basic_string<charT, ST, SA>& p, 
            const basic_regex<charT, traits>& e, 
            int submatch = 0, 
            regex_constants::match_flag_type m = regex_constants::match_default);
                                
   template <class charT, class traits, std::size_t N>
   regex_token_iterator<const charT*, charT, traits> 
   ``[link boost_regex.regex_token_iterator.make make_regex_token_iterator]``(
            const charT* p, 
            const basic_regex<charT, traits>& e, 
            const int (&submatch)[N], 
            regex_constants::match_flag_type m = regex_constants::match_default);
                               
   template <class charT, class traits, class ST, class SA, std::size_t N>
   regex_token_iterator<typename std::basic_string<charT, ST, SA>::const_iterator, charT, traits> 
      ``[link boost_regex.regex_token_iterator.make make_regex_token_iterator]``(
            const std::basic_string<charT, ST, SA>& p, 
            const basic_regex<charT, traits>& e, 
            const int (&submatch)[N], 
            regex_constants::match_flag_type m = regex_constants::match_default);
                                
   template <class charT, class traits>
   regex_token_iterator<const charT*, charT, traits> 
      ``[link boost_regex.regex_token_iterator.make make_regex_token_iterator]``(
            const charT* p, 
            const basic_regex<charT, traits>& e, 
            const std::vector<int>& submatch, 
            regex_constants::match_flag_type m = regex_constants::match_default);
                                
   template <class charT, class traits, class ST, class SA>
   regex_token_iterator<
         typename std::basic_string<charT, ST, SA>::const_iterator, charT, traits> 
      ``[link boost_regex.regex_token_iterator.make make_regex_token_iterator]``(
            const std::basic_string<charT, ST, SA>& p, 
            const basic_regex<charT, traits>& e, 
            const std::vector<int>& submatch, 
            regex_constants::match_flag_type m = regex_constants::match_default);

[h4 Description]

[#boost_regex.regex_token_iterator.construct1]

   regex_token_iterator();

[*Effects]: constructs an end of sequence iterator.

[#boost_regex.regex_token_iterator.construct2]

   regex_token_iterator(BidirectionalIterator a, 
                        BidirectionalIterator b, 
                        const regex_type& re, 
                        int submatch = 0, 
                        match_flag_type m = match_default);

[*Preconditions]: `!re.empty()`.  Object /re/ shall exist for the lifetime of 
the iterator constructed from it.

[*Effects]: constructs a [regex_token_iterator] that will enumerate one string for 
each regular expression match of the expression /re/ found within the sequence \[a,b), 
using match flags /m/ (see [match_flag_type]).  The string enumerated is the sub-expression /submatch/ 
for each match found; if /submatch/ is -1, then enumerates all the text 
sequences that did not match the expression /re/ (that is to performs field 
splitting).

[*Throws]: `std::runtime_error` if the complexity of matching the expression against 
an N character string begins to exceed O(N[super 2]), or if the program runs 
out of stack space while matching the expression (if Boost.Regex is configured 
in recursive mode), or if the matcher exhausts its permitted memory 
allocation (if Boost.Regex is configured in non-recursive mode).

[#boost_regex.regex_token_iterator.construct3]

   regex_token_iterator(BidirectionalIterator a, 
                        BidirectionalIterator b, 
                        const regex_type& re, 
                        const std::vector<int>& submatches, 
                        match_flag_type m = match_default);

[*Preconditions]: `submatches.size() && !re.empty()`.  Object /re/ shall 
exist for the lifetime of the iterator constructed from it.

[*Effects]: constructs a [regex_token_iterator] that will enumerate 
`submatches.size()` strings for each regular expression match of 
the expression /re/ found within the sequence \[a,b), using match flags /m/ 
(see [match_flag_type]).  For each match found one string will be enumerated 
for each sub-expression index contained within submatches vector; if 
`submatches[0]` is -1, then the first string enumerated for each match will be 
all of the text from end of the last match to the start of the current match, 
in addition there will be one extra string enumerated when no more matches can 
be found: from the end of the last match found, to the end of the underlying sequence.

[*Throws]: `std::runtime_error` if the complexity of matching the expression 
against an N character string begins to exceed O(N[super 2]), or if the 
program runs out of stack space while matching the expression (if Boost.Regex is 
configured in recursive mode), or if the matcher exhausts its permitted memory 
allocation (if Boost.Regex is configured in non-recursive mode).

[#boost_regex.regex_token_iterator.construct4]

   template <std::size_t N>
   regex_token_iterator(BidirectionalIterator a, 
                        BidirectionalIterator b, 
                        const regex_type& re, 
                        const int (&submatches)[R], 
                        match_flag_type m = match_default);

[*Preconditions]: `!re.empty()`.  Object /re/ shall exist for the lifetime of the iterator constructed from it.

[*Effects]: constructs a [regex_token_iterator] that will enumerate /R/ strings 
for each regular expression match of the expression /re/ found within the sequence 
\[a,b), using match flags /m/ (see [match_flag_type]).  For each match found one 
string will be enumerated for each sub-expression index contained within the 
/submatches/ array; if `submatches[0]` is -1, then the first string enumerated for 
each match will be all of the text from end of the last match to the start 
of the current match, in addition there will be one extra string enumerated when 
no more matches can be found: from the end of the last match found, to 
the end of the underlying sequence.

[*Throws]: `std::runtime_error` if the complexity of matching the expression 
against an N character string begins to exceed O(N[super 2]), or if the 
program runs out of stack space while matching the expression (if Boost.Regex 
is configured in recursive mode), or if the matcher exhausts its 
permitted memory allocation (if Boost.Regex is configured in non-recursive mode).

[#boost_regex.regex_token_iterator.construct5]

   regex_token_iterator(const regex_token_iterator& that);

[*Effects]: constructs a copy of `that`.

[*Postconditions]: `*this == that`.

[#boost_regex.regex_token_iterator.assign]

   regex_token_iterator& operator=(const regex_token_iterator& that);

[*Effects]: sets `*this` to be equal to `that`.

[*Postconditions]: `*this == that`.

[#boost_regex.regex_token_iterator.op_eq]

   bool operator==(const regex_token_iterator&)const;

[*Effects]: returns true if `*this` is the same position as `that`.

[#boost_regex.regex_token_iterator.op_ne]

   bool operator!=(const regex_token_iterator&)const;

[*Effects]: returns `!(*this == that)`.

[#boost_regex.regex_token_iterator.op_deref]

   const value_type& operator*()const;

[*Effects]: returns the current character sequence being enumerated.

[#boost_regex.regex_token_iterator.op_arrow]

   const value_type* operator->()const;

[*Effects]: returns `&(*this)`.

[#boost_regex.regex_token_iterator.op_inc1]

   regex_token_iterator& operator++();

[*Effects]: Moves on to the next character sequence to be enumerated.

[*Throws]: `std::runtime_error` if the complexity of matching the expression 
against an N character string begins to exceed O(N[super 2]), or if the program 
runs out of stack space while matching the expression (if Boost.Regex is 
configured in recursive mode), or if the matcher exhausts its permitted 
memory allocation (if Boost.Regex is configured in non-recursive mode).

[*Returns]: `*this`.

[#boost_regex.regex_token_iterator.op_inc2]

   regex_token_iterator& operator++(int);

[*Effects]: constructs a copy result of `*this`, then calls `++(*this)`.

[*Returns]: result.

[#boost_regex.regex_token_iterator.make]

   template <class charT, class traits>
   regex_token_iterator<const charT*, charT, traits> 
      make_regex_token_iterator(
            const charT* p, 
            const basic_regex<charT, traits>& e, 
            int submatch = 0, 
            regex_constants::match_flag_type m = regex_constants::match_default);
                             
   template <class charT, class traits, class ST, class SA>
   regex_token_iterator<typename std::basic_string<charT, ST, SA>::const_iterator, charT, traits> 
      make_regex_token_iterator(
            const std::basic_string<charT, ST, SA>& p, 
            const basic_regex<charT, traits>& e, 
            int submatch = 0, 
            regex_constants::match_flag_type m = regex_constants::match_default);
                                
   template <class charT, class traits, std::size_t N>
   regex_token_iterator<const charT*, charT, traits> 
   make_regex_token_iterator(
            const charT* p, 
            const basic_regex<charT, traits>& e, 
            const int (&submatch)[N], 
            regex_constants::match_flag_type m = regex_constants::match_default);
                               
   template <class charT, class traits, class ST, class SA, std::size_t N>
   regex_token_iterator<
         typename std::basic_string<charT, ST, SA>::const_iterator, charT, traits> 
      make_regex_token_iterator(
            const std::basic_string<charT, ST, SA>& p, 
            const basic_regex<charT, traits>& e, 
            const int (&submatch)[N], 
            regex_constants::match_flag_type m = regex_constants::match_default);
                                
   template <class charT, class traits>
   regex_token_iterator<const charT*, charT, traits> 
      make_regex_token_iterator(
            const charT* p, 
            const basic_regex<charT, traits>& e, 
            const std::vector<int>& submatch, 
            regex_constants::match_flag_type m = regex_constants::match_default);
                                
   template <class charT, class traits, class ST, class SA>
   regex_token_iterator<
         typename std::basic_string<charT, ST, SA>::const_iterator, charT, traits> 
      make_regex_token_iterator(
            const std::basic_string<charT, ST, SA>& p, 
            const basic_regex<charT, traits>& e, 
            const std::vector<int>& submatch, 
            regex_constants::match_flag_type m = regex_constants::match_default);

[*Effects]: returns a [regex_token_iterator] that enumerates one [sub_match] 
for each value in /submatch/ for each occurrence of regular expression /e/ 
in string /p/, matched using [match_flag_type] /m/.

[h4 Examples]

The following example takes a string and splits it into a series of tokens:

   #include <iostream>
   #include <boost/regex.hpp>

   using namespace std;

   int main(int argc)
   {
      string s;
      do{
         if(argc == 1)
         {
            cout << "Enter text to split (or \"quit\" to exit): ";
            getline(cin, s);
            if(s == "quit") break;
         }
         else
            s = "This is a string of tokens";

         boost::regex re("\\s+");
         boost::sregex_token_iterator i(s.begin(), s.end(), re, -1);
         boost::sregex_token_iterator j;

         unsigned count = 0;
         while(i != j)
         {
            cout << *i++ << endl;
            count++;
         }
         cout << "There were " << count << " tokens found." << endl;

      }while(argc == 1);
      return 0;
   }


The following example takes a html file and outputs a list of all the linked files:

   #include <fstream>
   #include <iostream>
   #include <iterator>
   #include <boost/regex.hpp>

   boost::regex e("<\\s*A\\s+[^>]*href\\s*=\\s*\"([^\"]*)\"",
                  boost::regex::normal | boost::regbase::icase);

   void load_file(std::string& s, std::istream& is)
   {
      s.erase();
      //
      // attempt to grow string buffer to match file size,
      // this doesn't always work...
      s.reserve(is.rdbuf()->in_avail());
      char c;
      while(is.get(c))
      {
         // use logarithmic growth strategy, in case
         // in_avail (above) returned zero:
         if(s.capacity() == s.size())
            s.reserve(s.capacity() * 3);
         s.append(1, c);
      }
   }

   int main(int argc, char** argv)
   {
      std::string s;
      int i;
      for(i = 1; i < argc; ++i)
      {
         std::cout << "Findings URL's in " << argv[i] << ":" << std::endl;
         s.erase();
         std::ifstream is(argv[i]);
         load_file(s, is);
         boost::sregex_token_iterator i(s.begin(), s.end(), e, 1);
         boost::sregex_token_iterator j;
         while(i != j)
         {
            std::cout << *i++ << std::endl;
         }
      }
      //
      // alternative method:
      // test the array-literal constructor, and split out the whole
      // match as well as $1....
      //
      for(i = 1; i < argc; ++i)
      {
         std::cout << "Findings URL's in " << argv[i] << ":" << std::endl;
         s.erase();
         std::ifstream is(argv[i]);
         load_file(s, is);
         const int subs[] = {1, 0,};
         boost::sregex_token_iterator i(s.begin(), s.end(), e, subs);
         boost::sregex_token_iterator j;
         while(i != j)
         {
            std::cout << *i++ << std::endl;
         }
      }

      return 0;
   }

     
[endsect]