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< title > Boost.Regex: Algorithm regex_split (deprecated)< / title >
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< H1 align = "center" > Boost.Regex< / H1 >
< H2 align = "center" > Algorithm regex_split (deprecated)< / H2 >
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< P > The algorithm regex_split has been deprecated in favor of the iterator < A href = "regex_token_iterator.html" >
regex_token_iterator< / A > which has a more flexible and powerful interface,
as well as following the more usual standard library "pull" rather than "push"
semantics.< / P >
< P > Code which uses regex_split will continue to compile, the following
documentation is taken from the previous boost.regex version:< / P >
< H3 > < A name = "regex_split" > < / A > Algorithm regex_split< / H3 >
< PRE > #include < < A href = "../../../boost/regex.hpp" > boost/regex.hpp< / A > > < / PRE >
< P > Algorithm regex_split performs a similar operation to the perl split operation,
and comes in three overloaded forms:
< / P >
< PRE > < B > template< / B > < < B > class< / B > OutputIterator, < B > class< / B > charT, < B > class< / B > Traits1, < B > class< / B > Alloc1, < B > class< / B > Traits2, < B > class< / B > Alloc2>
std::size_t regex_split(OutputIterator out,
std::basic_string< charT, Traits1, Alloc1> & s,
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< B > const< / B > basic_regex< charT, Traits2, Alloc2> & e,
< STRONG > < / STRONG > boost::match_flag_type flags,
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std::size_t max_split);
< B > template< / B > < < B > class< / B > OutputIterator, < B > class< / B > charT, < B > class< / B > Traits1, < B > class< / B > Alloc1, < B > class< / B > Traits2, < B > class< / B > Alloc2>
std::size_t regex_split(OutputIterator out,
std::basic_string< charT, Traits1, Alloc1> & s,
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< B > const< / B > basic_regex< charT, Traits2, Alloc2> & e,
boost::match_flag_type flags = match_default);
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< B > template< / B > < < B > class< / B > OutputIterator, < B > class< / B > charT, < B > class< / B > Traits1, < B > class< / B > Alloc1>
std::size_t regex_split(OutputIterator out,
std::basic_string< charT, Traits1, Alloc1> & s);< / PRE >
< P > < STRONG > Effects: < / STRONG > Each version of the algorithm takes an
output-iterator for output, and a string for input. If the expression contains
no marked sub-expressions, then the algorithm writes one string onto the
output-iterator for each section of input that does not match the expression.
If the expression does contain marked sub-expressions, then each time a match
is found, one string for each marked sub-expression will be written to the
output-iterator. No more than < I > max_split < / I > strings will be written to the
output-iterator. Before returning, all the input processed will be deleted from
the string < I > s< / I > (if < I > max_split < / I > is not reached then all of < I > s< / I > will
be deleted). Returns the number of strings written to the output-iterator. If
the parameter < I > max_split< / I > is not specified then it defaults to UINT_MAX.
If no expression is specified, then it defaults to "\s+", and splitting occurs
on whitespace.
< / P >
< P > < STRONG > Throws:< / STRONG > < CODE > std::runtime_error< / CODE > if the complexity of
matching the expression against an N character string begins to exceed O(N< SUP > 2< / SUP > ),
or if the program runs out of stack space while matching the expression (if
Boost.regex is < A href = "configuration.html" > configured< / A > in recursive mode),
or if the matcher exhausts it's permitted memory allocation (if Boost.regex is < A href = "configuration.html" >
configured< / A > in non-recursive mode).< / P >
< P > < A href = "../example/snippets/regex_split_example_1.cpp" > Example< / A > : the
following function will split the input string into a series of tokens, and
remove each token from the string < I > s< / I > :
< / P >
< PRE > < B > unsigned< / B > tokenise(std::list< std::string> & l, std::string& s)
{
< B > return< / B > boost::regex_split(std::back_inserter(l), s);
}< / PRE >
< P > < A href = "../example/snippets/regex_split_example_2.cpp" > Example< / A > : the
following short program will extract all of the URL's from a html file, and
print them out to < I > cout< / I > :
< / P >
< PRE > < FONT color = #008000 > #include < list>
#include < fstream>
#include < iostream>
#include < boost/regex.hpp>
< / FONT >
boost::regex e(< FONT color = #000080 > "< \\s*A\\s+[^> ]*href\\s*=\\s*\"([^\"]*)\""< / FONT > ,
boost::regbase::normal | boost::regbase::icase);
< B > void< / B > load_file(std::string& s, std::istream& is)
{
s.erase();
< FONT color = #000080 > //
// attempt to grow string buffer to match file size,
// this doesn't always work...
< / FONT > s.reserve(is.rdbuf()-& gtin_avail());
< B > char< / B > c;
< B > while< / B > (is.get(c))
{
< FONT color = #000080 > // use logarithmic growth stategy, in case
// in_avail (above) returned zero:
< / FONT > < B > if< / B > (s.capacity() == s.size())
s.reserve(s.capacity() * 3);
s.append(1, c);
}
}
< B > int< / B > main(< B > int< / B > argc, < B > char< / B > ** argv)
{
std::string s;
std::list< std::string> l;
< B > for< / B > (< B > int< / B > i = 1; i < argc; ++i)
{
std::cout < < < FONT color = #000080 > "Findings URL's in "< / FONT > < < argv[i] < < < FONT color = #000080 > ":"< / FONT > < < std::endl;
s.erase();
std::ifstream is(argv[i]);
load_file(s, is);
boost::regex_split(std::back_inserter(l), s, e);
< B > while< / B > (l.size())
{
s = *(l.begin());
l.pop_front();
std::cout < < s < < std::endl;
}
}
< B > return< / B > 0;
}< / PRE >
< HR >
< p > Revised
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04 Feb 2004
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< p > < i > <EFBFBD> Copyright John Maddock 1998-
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< P > < I > Use, modification and distribution are subject to 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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