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regular expression to extract numbers
by Neil Sutton 29 Jan '13

29 Jan '13

Hi, I am new to using boost and am trying to learn basics so I can use regex features in my code. In my test program, I want a function to simply extract some numbers that follow after a certain string pattern and then to read those numbers into a vector. This is an outline of what i would like to do: // function definition #ifndef findnumbers.h #define findnumbers.h #include <string> #include <fstream> #include <vector> #include <boost/regex.hpp> #endif void findnumbers (ifstream& afile) { // assume file is opened in main - i have passed a reference boost::regex expression ( ....having trouble with this); // search for matches - there will be a fixed number of numbers e.g 10 std::string const_iterator start, end; start = afile.begin( ); end = afile.end( ); std::vector<int> results; boost::match_results<std::vector<int>::const_iterator> what; for(int count = 0; count !=10; count++) { boost::regex_search(start,end,what,expression) { //if a number is found place in the vector results.push_back(count); } So the first problem I have is defining a correct expression. The pattern has the format "sometext>NUMBERS<sometext" newline. The NUMBERS may be one or two digits combined and the pattern is repeated 10 times. I have searched the archives and tried to build something based on the examples I have read, but cannot seem to find a working solution. Can anyone help please in defining an expression? I do not need a solution to my function overall as I should be able to write it correctly once I know how to define the pattern. Kind regards

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[GIL] Why does 'get_color' take a tag object instead of its type only?
by TONGARI 29 Jan '13

29 Jan '13

Hi there, I'm curious of why gil::get_color(pixel, tag) is defined that way. Any need to take the tag value? If not, I'd prefer gil::get_color<Tag>(pixel) or just gil::get<Tag>(pixel) or even Tag::get(pixel). And if possible, I hope GIL would just make pixel a Fusion sequence. Thanks.

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stack_allocator
by Andrew Hundt 29 Jan '13

29 Jan '13

Is there some version of a stack allocator in the current 1.52 version of boost, perhaps in some detail namespace? I searched the source and the archives and the only one I could find disappeared after 1.39: http://www.boost.org/doc/libs/1_39_0/boost/signals2/detail/stack_allocator.… Cheers! Andrew Hundt

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Which Parallel Boost Graph Library should I use?
by Christopher Cowing-Zitron 29 Jan '13

29 Jan '13

Hello, There is more than one PBGL server, one hosted by Boost, and the other by the Open Systems Laboratory (OSL). It appears that each has code not included in the other, whether I look at the release or sandbox SVN versions of the library. I have three criteria as to which version(s) I should use, which are all equally important to my final choice. First, in general, which is more reliable, the Boost or the OSL version? Both Boost and the OSL know their stuff, so it's not that I question the authors' skill, but rather I don't know which version has received more testing and validation. Second, which is more up-to-date, both in terms of which is updated more frequently, and which is more algorithmically and mathematically current? While I know programmers do love their graph algorithms, I wonder if the actual computer scientists and mathematicians at the OSL are more on the cutting edge. Finally, whether I use the Boost or the OSL server, I am more interested in the sandbox version than the release, as the development version has a lot of good stuff which isn't present in the release. That being said, in my experience there is quite a bit of variability amongst sandbox libraries as to their readiness for use, and I am not sure whether either PBGL sandbox is functional. Note, if there is some feature in one of the sandboxes that I am quite interested in, but is not yet at production quality, I wouldn't mind fixing it up for the community. Answers to any or all of the above questions would be most appreciated. Have a good day, -- Chris

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narrowing conversion warning in boost's regex_traits_defaults.hpp when trying to initialize wregex object
by rsk82 28 Jan '13

28 Jan '13

The first line compiles ok. The second also produces working EXE, but in addition I get this large error: In file included from d:\boost/boost/regex/v4/regex_traits.hpp:35:0, from d:\boost/boost/regex/regex_traits.hpp:27, from d:\boost/boost/regex/v4/regex.hpp:39, from d:\boost/boost/regex.hpp:31, from test.cpp:4: d:\boost/boost/regex/v4/regex_traits_defaults.hpp: In instantiation of 'const charT* boost::re_detail::get_escape_R_string() [with charT = wchar_t]': d:\boost/boost/regex/v4/basic_regex_parser.hpp:804:54: required from 'bool boost::re_detail::basic_regex_parser<charT, traits>::parse_extended_escape() [with charT = wchar_t; traits = boost::regex_traits<wchar_t>]' d:\boost/boost/regex/v4/basic_regex_parser.hpp:308:36: required from 'bool boost::re_detail::basic_regex_parser<charT, traits>::parse_extended() [with charT = wchar_t; traits = boost::regex_traits<wchar_t>]' d:\boost/boost/regex/v4/basic_regex_parser.hpp:134:10: required from 'void boost::re_detail::basic_regex_parser<charT, traits>::parse(const charT*, const charT*, unsigned int) [with charT = wchar_t; traits = boost::regex_traits<wchar_t>]' d:\boost/boost/regex/v4/basic_regex.hpp:215:7: required from 'void boost::re_detail::basic_regex_implementation<charT, traits>::assign(const charT*, const charT*, boost::re_detail::basic_regex_implementation<charT, traits>::flag_type) [with charT = wchar_t; traits = boost::regex_traits<wchar_t>; boost::re_detail::basic_regex_implementation<charT, traits>::flag_type = unsigned int]' d:\boost/boost/regex/v4/basic_regex.hpp:661:4: required from 'boost::basic_regex<charT, traits>& boost::basic_regex<charT, traits>::do_assign(const charT*, const charT*, boost::basic_regex<charT, traits>::flag_type) [with charT = wchar_t; traits = boost::regex_traits<wchar_t>; boost::basic_regex<charT, traits>::flag_type = unsigned int]' d:\boost/boost/regex/v4/basic_regex.hpp:382:33: required from 'boost::basic_regex<charT, traits>& boost::basic_regex<charT, traits>::assign(const charT*, const charT*, boost::basic_regex<charT, traits>::flag_type) [with charT = wchar_t; traits = boost::regex_traits<wchar_t>; boost::basic_regex<charT, traits> = boost::basic_regex<wchar_t, boost::regex_traits<wchar_t> >; boost::basic_regex<charT, traits>::flag_type = unsigned int]' d:\boost/boost/regex/v4/basic_regex.hpp:367:48: required from 'boost::basic_regex<charT, traits>& boost::basic_regex<charT, traits>::assign(const charT*, boost::basic_regex<charT, traits>::flag_type) [with charT = wchar_t; traits = boost::regex_traits<wchar_t>; boost::basic_regex<charT, traits> = boost::basic_regex<wchar_t, boost::regex_traits<wchar_t> >; boost::basic_regex<charT, traits>::flag_type = unsigned int]' d:\boost/boost/regex/v4/basic_regex.hpp:336:7: required from 'boost::basic_regex<charT, traits>::basic_regex(const charT*, boost::basic_regex<charT, traits>::flag_type) [with charT = wchar_t; traits = boost::regex_traits<wchar_t>; boost::basic_regex<charT, traits>::flag_type = unsigned int]' test.cpp:15:37: required from here d:\boost/boost/regex/v4/regex_traits_defaults.hpp:329:73: warning: narrowing conversion of ''\37777777605'' from 'char' to 'const wchar_t' inside { } [-Wnarrowing] d:\boost/boost/regex/v4/regex_traits_defaults.hpp:331:64: warning: narrowing conversion of ''\37777777605'' from 'char' to 'const wchar_t' inside { } [-Wnarrowing] code : #include <iostream> #include <boost/regex.hpp> int main() { boost::regex narrow_str_regex("a+"); boost::wregex wide_str_regex(L"a+"); } boost: http://sourceforge.net/projects/boost/files/boost/1.52.0/boost_1_52_0.7z compiler: http://sourceforge.net/projects/mingwbuilds/files/host-windows/releases/4.7… ( and I know that this is the bug: https://svn.boost.org/trac/boost/ticket/7263 ) so, any tricks to get around this (some compiler switches?, I dunno) ? Or can I just ignore this error ? (Yes I need regex matching on wide strings.) -- View this message in context: http://boost.2283326.n4.nabble.com/narrowing-conversion-warning-in-boost-s-… Sent from the Boost - Users mailing list archive at Nabble.com.

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[1.53.0] Beta release candidates 2 now available for testing
by Marshall Clow 28 Jan '13

28 Jan '13

Updated release candidate files for 1.53.0 beta 1 are available at http://boost.cowic.de/rc/ As always, the release managers would appreciate it if you download the candidate of your choice and give building it a try. Please report both success and failure, and anything else that is noteworthy. This helps ensure the candidates build OK before we push them out to SourceForge. The files (and associated md5s) are: 579b680bf55f53cd6d50adc391cb6c23 *boost_1_53_0_beta1_rc2.tar.gz 02098bb6da0e9c10712ae63c16e6aeea *boost_1_53_0_beta1_rc2.tar.bz2 998e2616a66c50e5693f563afb899002 *boost_1_53_0_beta1_rc2.zip e4fde6a869a3e21f8751ba8b7fd471a8 *boost_1_53_0_beta1_rc2.7z There were three changes between rc1 and rc2: * Fixes for compilation errors in Boost.Serialization * Documentation updates for Boost.SmartPtr * Updates to Boost.Threads Thanks, --The release managers

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Re: [Boost-users] boost random in 2 dimensions
by Robert Patterson 28 Jan '13

28 Jan '13

@Gabriel >From your answer I understand that, the uniform distributed values are >generated seperately for x and y axis. Then both should be combined to >form a point over a plane. @Norbert i think this could do uniform distribution only over one co-ordinates. I am assuming you want to sample a point uniformly at random from a rectangular subset of the plane with the sides of the rectangle parallel to the axes. If not, the problem is a little more complex, but still soluble. However, for a square of size 1 Norbert is correct. The extension to a general rectangle is simple - just use two uniform_real_distributions (this will also give you floating point numbers as per your first post). Calls to two different uniform_real_distributions (or successive calls to one object) using the same engine object will give a point uniformly distributed in the rectangle. You are correct to point out that the individual coordinates are also uniformly distributed, but since they are independent they also yield a uniformly distributed point on the rectangle. Robert

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Assertion `invariant_()' failed. in boost multi index
by Sunil S Nandihalli 28 Jan '13

28 Jan '13

Hi Everybody, Boost multi index is a very nice library. But I have a situation where the invariant_() assertion fails. One of the indices is ordered based on a score which is computed with a function. The score of the same element can change when computed at different times. but however, the scores change, score decay over time, such that the previously computed order will always be right. While I don't know if this is the issue, I wanted to make sure that this kind of scoring functions does not cause a problem because of some caching that boost may be doing internally .. and also, the return value of the scoring function is a double which I can imagine can introduce some comparison issues. I am digging into the code to make sure that that is not the problem .. any pointers from the community is greatly appreciated. Thanks, Sunil.

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[spirit/qi] Error handler not called
by Szymon Gatner 28 Jan '13

28 Jan '13

Hi, I am trying to develop a JSON parser using spirit/qi so far it is not going bad but I am having serious problem with on_error and error handler. This is my code: namespace qi = boost::spirit::qi; namespace ascii = boost::spirit::ascii; namespace phoenix = boost::phoenix; template <typename Iterator> struct error_handler { template <typename, typename, typename, typename> struct result { typedef void type; }; void operator()(Iterator first, Iterator last, Iterator err_pos, const boost::spirit::info& info) const { std::cout << "never called"; } }; template <class Iterator> struct JsonGrammar : public qi::grammar<Iterator, Value(), ascii::space_type> { JsonGrammar() : JsonGrammar::base_type(json, "json"), error(error_handler<Iterator>()) { using qi::double_; using qi::lexeme; using qi::char_; using qi::int_; using qi::on_error; using qi::fail; using phoenix::construct; using phoenix::val; using namespace qi::labels; qi::on_error<qi::fail>(json, error(_1, _2, _3, _4)); string %= lexeme['"' >> +(char_ - '"') >> '"']; number = int_; member = string >> ':' >> value; array = '[' >> value % ',' >> ']'; object = '{' >> member >> *(',' >> member) >> '}'; value = array | object | number | string | qi::bool_ | "null"; json = array | object; json.name("json"); } phoenix::function<error_handler<Iterator> > const error; qi::rule<Iterator, std::string(), ascii::space_type> string; qi::rule<Iterator, int(), ascii::space_type> number; qi::rule<Iterator, Value(), ascii::space_type> json; qi::rule<Iterator, Array(), ascii::space_type> array; qi::rule<Iterator, Value(), ascii::space_type> value; qi::rule<Iterator, Object(), ascii::space_type> object; qi::rule<Iterator, std::pair<std::string, Value>(), ascii::space_type> member; }; now when i try to parse std::string json = "[1, 2, 3, 4, t]"; parising result is false. but error handelr is never called. What am I doing wrong? Regards, Simon -- Szymon Gatner The Lordz Games Studio www.thelordzgamesstudio.com

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boost random in 2 dimensions
by Danny 28 Jan '13

28 Jan '13

I am trying to use a boost random generator to make random points uniformly distributed over a plane surface. In the the following link, the code for doing it in a single dimension is available: http://stackoverflow.com/questions/2254909/boost-random-number-generator Here they use boost::uniform_int<> to generate numbers as int in a single dimension. But in my case I wish to generate numbers as float in two dimensions over a plane. Is there any distribution type available to use it in two dimensions? (I have seen boost::uniform_on_sphere, but it is for spherical surfaces.) Is it possible to to this using boost library? -- View this message in context: http://boost.2283326.n4.nabble.com/boost-random-in-2-dimensions-tp4641761.h… Sent from the Boost - Users mailing list archive at Nabble.com.

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