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[Range] Range adaptors and compatibility with non-adapted iterators
by John M. Dlugosz 12 Jan '12

12 Jan '12

Consider something like this: themap_type::iterator search_for (int val) { return boost::find_if (themap|map_values, my_predicate(val)); } The return from the function chokes because the adapted iterator type cannot be convered back to the original type of iterator in the parent collection. This is more general. If I wasn't just returning through but using the result within the function, how do I test against end to see if find_if was successful? auto it2= boost::find_if (themap|map_values, my_predicate(val)); if (it2 == themap::end()) // same problem! This seems to be a problem with any algorithm that returns an iterator or otherwise makes the iterators used within the algorithm visible outside of it, even if such usage is just as an "end" flag and not really used to locate the element within the original collection for subsequent iteration. Am I missing something? Is there a good reason why the filtered iterator can't give up the inner original iterator? How do you use range adaptors in these situations? —John

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Help needed in creating Regex...
by Subhash Nagre 12 Jan '12

12 Jan '12

Hi everyone, I need a help in creating a regular expression, I need to select only "Sentences" in String using Regex so I wrote the Code .. *boost::regex re( "(\\S.+?[.!?])(?=\\s+|$)" );* This code considers that sentences break at any of these three characters . ! ? but this code considers string "Mr. Obama" as 2 difference sentences (being a dot character in between), where as I want it to be only one sentence. I have a got a string vector of all the words which have to excluded. std::vector<std:string>exceptionVector; exceptionVector.pushback("Mr.") exceptionVector.pushback("Dr.") exceptionVector.pushback("Mrs.") Now in my regex, I want that if any of the words occur from my vector, it should NOT be a seperate sentence. Any idea how can I create this Regular expression Thanks in Advance -Subhash

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asio raw with PF_PACKET and promiscuous mode?
by Chris Cleeland 11 Jan '12

11 Jan '12

Before I reinvent the wheel, has anybody put together an asio encapsulation of Linux' AF_PACKET sockets with SOCK_RAW? Also, I'm trying to wrap my brain around how I might represent the concept of an "endpoint" for a socket like this. Rather than an IPv4/v6 address, one binds to an interface. So, while there is a concept of a resolver, it resolves an interface name to an interface index value. >From a C/system call perspective, I need to do the following to get the ball rolling: 1. s = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL)) 2. sockaddr_ll myinterface = { .sll_family = AF_PACKET, .sll_protocol = htons(ETH_P_ALL), .sll_ifindex = interfaceIndex("eth0") }, then bind(s, &myinterface) 3. packet_mreq promiscuous_cmd = { .mr_ifindex = interfaceIndex("eth0"), .mr_type = PACKET_MR_PROMISC }, then setsockopt(s, PACKET_ADD_MEMBERSHIP, &promiscuous_cmd) I'm pretty sure that for #1, I need a class packet that models the Protocol concept. But where to put the rest is a bit fuzzier. Do I need to create a whole new "resolver" for interface names? I guess I should also note that, at least for the moment, this is just a means to an end, rather than the end itself. So, I don't need to craft the entire thing--I need to get enough working to be able to easily write some code that can capture all network packets on a given interface, e.g., class snooper { public: snooper(std::string interfacename); void start(); void stop(); ... }; so I can just do something like snooper s("eth0"); s.start(); ...capture stuff... s.stop(); (I'm obviously omitting the part where snooper would hook into objects that would receive and process captured packets, but I'd like for that to work similar to how one plumbs up receipt of udp packets.) -- Chris Cleeland

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casting shared pointers to derived classes
by Don Wilde 11 Jan '12

11 Jan '12

Greetings, all - I am updating a neural network package from the DOS days to modern C++ standards. I have a shared_ptr to a vector of shared_ptrs of type Layer. This class has derived classes OutputLayer, MiddleLayer and InputLayer. Each of these has their own method for calculating output updates, so I need to be able to cast. from boost::shared_ptr<Layer> to static_cast<OutputLayer*>(). Unfortunately, VC++ 2010 will not allow me to do so. It won't even allow a reinterpret_cast. I've looked on the Web and I also have Schalling's guide to Boost. Thank you in advance for your guidance. I'm using boost_1_47_0, if that makes a difference. :D

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[Fwd: How to print the structure of vector of boost::variant]
by Baba Prasad 11 Jan '12

11 Jan '12

Dear friends, please see the bellow my code and tell me how to get out this problem please.when I try to print values of variant it's giving the error as: std::ostream& operator<<(std::ostream&, const status_rsp&): worked.cpp:33: error: const struct status_rsp has no member named os worked.cpp:33: error: const class boost::variant<int, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_> has no member named channelid worked.cpp:33: error: expected ) before ; token worked.cpp:34: error: const class boost::variant<int, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost #include<vector> #include<iostream> #include<boost/variant.hpp> typedef int cid; typedef int n_queue; typedef boost::variant<chid> link_st_rs; typedef std::vector<link_st_rs> link_st_rs_list; typedef boost::variant<n_queue> link_de_rs; typedef std::vector<link_de_rs> link_de_rs_list; using namespace std; struct lparam { int value; }; typedef vector<lparam> link1; struct link_s_rsp { link1 ll; link_st_rs_list lsrl; link_de_rs_list ldrl; }; struct status_rsp { link_s_rsp rsp; friend std::ostream& operator<<(std::ostream& os , const status_rsp& sr) { os << "the value is " << sr.rsp.ll.front().value; os << "id" << sr.rsp.lsrl.front().chid; os << "val" << sr.rsp.ldrl.front().n_queue; return os; } }; typedef vector<status_rsp> srl; int main() { linkparam lp; lp.value =90; link_de_rs_list ldrl; lsrl.push_back(4); ldrl.push_back(3); status_rsp sr; sr.rsp.ll.push_back(lp); srl srl1; srl1.push_back(sr); link1::iterator iter2 = srl1.begin()->rsp.ll.begin(); cout << "A vlue is: " << iter2->value; link_st_rs_list::iterator iter3 = srl1.begin()->rsp.lsrl.begin(); cout << " B value " << iter3->chid; link_de_rs_list::iterator iter4 = srl1.begin()->rsp.ldrl.begin(); cout << "C value" < iter4->n_queue; cin.ignore(); return 0; } Best Regards BaBu -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.

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Needs advices on design ( mpl or processor )
by Allan Nielsen 11 Jan '12

11 Jan '12

Hi This is not a specific questions directly related to Boost::mpl, but a request for help if somebody has the time... For the last couple of month I have been trying to learn to use the boost::mpl library. To learn to use the library I decided to use it for creating a "compressed-enum" library. The library should make it possible to store several enums in a single variable (for instance an unsigned int) Here is a simple example to give en idea: // example enums to play with struct TagA { enum Size { size = 4 }; enum Max { max = 3 }; enum E { A0 = 0, A1 = 1, A2 = 2, A3 = 3, }; }; struct TagB { enum Size { size = 4 }; enum Max { max = 3 }; enum E { B0 = 0, B1 = 1, B2 = 2, B3 = 3, }; }; struct TagC { enum Size { size = 4 }; enum Max { max = 3 }; enum E { C0 = 0, C1 = 1, C2 = 2, C3 = 3, }; }; struct First{}; struct Second{}; int main() { // using the compressed enums library typedef unsigned short STORAGE; typedef CompressedEnums< STORAGE, CompressedEnum<STORAGE, 1, TagA>, CompressedEnum<STORAGE, 4, TagB, First>, CompressedEnum<STORAGE, 16, TagB, Second>, CompressedEnumArray<STORAGE, 64, TagC, 5> > ENUMS; assert(sizeof(ENUMS) == 2)); ENUMS enums; enums.set<TagA>(TagA::A2); enums.set<Second>(TagB::B2); enums.set<3, TagC>(TagC::C2); cout << enums.get<TagA>() << " " << enums.get<Second>(TagB::B2) << " " << enums.get<3, TagC>(TagC::C2) << endl; } CompressedEnums contains the storage variable, and inherit from all its template arguments, and make their methods available through tags. CompressedEnum and CompressedEnumArray only contains static methods which can find the enum in the storage variable. Here is a snippet of my implementation: template < typename STORAGE_TYPE, int OFFSET, typename ENUM_CONTAINER, typename TAG = typename ENUM_CONTAINER::E > struct CompressedEnum { typedef TAG ACCESS_TAG; typedef typename ENUM_CONTAINER::E INNER_TYPE; enum Offset { offset = OFFSET }; enum Size { size = ENUM_CONTAINER::size }; static INNER_TYPE get(const STORAGE_TYPE& data) { return (INNER_TYPE)((data / OFFSET) % size); } ----%<----%<----%<----%<----%<----%<----%<----%<-- } template < typename STORAGE_TYPE, typename B00 = Dummy< 0>, typename B01 = Dummy< 1>, typename B02 = Dummy< 2>, typename B03 = Dummy< 3> > struct CompressedEnums : public B00, B01, B02, B03 { typedef boost::mpl::map<boost::mpl::pair<typename B00::ACCESS_TAG, B00>, boost::mpl::pair<typename B01::ACCESS_TAG, B01>, boost::mpl::pair<typename B02::ACCESS_TAG, B02>, boost::mpl::pair<typename B03::ACCESS_TAG, B03> > TYPE_MAP; template<typename TAG> typename boost::mpl::at<TYPE_MAP, TAG>::type::INNER_TYPE get() const { return boost::mpl::at<TYPE_MAP, TAG>::type::get(data); } ----%<----%<----%<----%<----%<----%<----%<----%<-- STORAGE_TYPE data; }; The code works and does what it is suppose to (as far as I know) but I'm not very happy with the interface: typedef CompressedEnums< STORAGE, // 1 because it is the first CompressedEnum<STORAGE, 1, TagA>, // 4 because TagA::size == 4 CompressedEnum<STORAGE, 4, TagB, First>, // 16 because TagA::size * TagB::size == 16 CompressedEnum<STORAGE, 16, TagB, Second>, // 64 because TagA::size * TagB::size * TagB::size == 64 CompressedEnumArray<STORAGE, 64, TagC, 5> > ENUMS; These magic numbers makes it very easy to make bugs when the code is restructured or changed, and it should be possible to calculate them automatic. If the magic numbers are replaced with their expresions the code will still break of the arguemnts are reordered. To accomplice this I have considered two solutions: macro or more templating... Using macroes I imagin the interface could look something like this: typedef CompressedEnums< STORAGE, ENUM_PACK( STORAGE, 1, (CompressedEnum, TagA) (CompressedEnum, TagB, First) (CompressedEnum, TagB, Second) (CompressedEnumArray, TagC, 5) ) > ENUMS; Which then would expand to the code manual entered above. Alternative using template I imagin that CompressedEnums could change CompressedEnum<STORAGE, 0, TagB, Second> -> CompressedEnum<STORAGE, 16, TagB, Second> automatic and then derive from that one automatic. I tried both, but non of my idea worked out very well, which is why I hope that one of you c++ experts could give me some hints. Best regards Allan W. Nielsen

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depth_first_visit
by James Lindsay 10 Jan '12

10 Jan '12

Hello, I've found several questions regarding the depth_first_visit algorithm but I can't find a complete example anywhere. I was wondering if someone could post a complete example of the depth_first_visit algorithm in action, including how you created the color map. Thanks

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[BGL / General] member of struct is a reference - why?
by Max Limper 10 Jan '12

10 Jan '12

Hi everybody, I was just going through the "File Dependency" example for the graph library and found this piece of code which is a very simple cycle detector: struct cycle_detector : public dfs_visitor<> { cycle_detector( bool& has_cycle) : _has_cycle(has_cycle) { } template <class Edge, class Graph> void back_edge(Edge, Graph&) { _has_cycle = true; } protected: bool& _has_cycle; }; It takes a reference and manipulates the externally declared variable hasCyle via that reference. I tried to change hasCylce to a "regular" member variable, and I just want to read it afterwards, like cycle_detector detector(); boost::depth_first_search(graph, boost::visitor(detector)); if (detector.foundCycles) { //do something } I also thought about giving the cycle detector other member variables, like a list of back edges that gets filled. However, I found that none of those variables gets set the right way, starting with the very simple "bool hasCycle" member. I guess there must be a reason why the person that made the example chose to use a reference, and it only works that way... any ideas why? Thanks a lot in advance.

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[C++ Now! 2012] Deadline extension: Call for Submissions, new deadline is January 20th, 2012
by Hartmut Kaiser 10 Jan '12

10 Jan '12

INAUGURAL C++ NOW! CONFERENCE 2012 Aspen CO, USA, May 14-18, 2012, www.cppnow.org CALL FOR SUBMISSIONS We invite you to submit session proposals to the Inaugural C++ Now! Conference: C++Now! 2012 (Aspen CO, USA, May 14 - 18, 2012). Based on the successful traditions of 5 years of BoostCon, which was the main face-to-face event for all things C++ and Boost (www.boost.org) C++Now! 2012 will present leading speakers from the whole C++ community. The conference name is changing to C++ Now! to reflect the current value of the language, the focus on its new state (from the new Standard), and the need to continually look to the future so the language remains useful to the C++ community. The focus of this conference will be the new C++11 language Standard and as usual Boost: what's new in C++, its Standard library, and in the Boost libraries, how to write and maintain them, how to evangelize or to deploy Boost within your organization. The new C++ Standard, but also the infrastructure and process of Boost, its vision and mission - no matter what you are interested in, it all comes together in the C++Now! sessions. Meet the colleagues, and feel the inspiration to support your work with C++ and Boost for the next year. The C++ Now! Conference is dedicated to discussion and education about C++, an open and free language and standard. Our Conference will focus on discussion and education about open source software usage and developments in the C++ developer and user community. To reflect the breadth of the C++ and Boost communities, the conference includes sessions aimed at three constituencies: C++ and Boost end-users, hard-core Boost library and tool developers, and researchers pushing the boundaries of computation. The program fosters interaction and engagement within and across those groups, with an emphasis on hands-on, participatory sessions. As a multi-paradigm language, C++ is a melting pot where the most compelling ideas from other programming communities are blended in powerful ways. Historically, some of the most popular sessions at C++Now! have highlighted these concepts, from DSLs to functional programming to transactional memory and more. Bring your C#, Python, Ruby or Haskell influences to bear in an environment that will broaden their exposure. IMPORTANT DATES New proposal submissions due: January 20th, 2012. UPDATED! Proposals decisions sent (tentative program): February 17th, 2012. Fully scheduled program available: February 25th, 2012. Session materials due: April 15th, 2012. BEST PRESENTATION AWARDS We know how much effort it takes to prepare talks for our conference. For this reason we will award the best presentations in the following categories: Best Presentation, Best Short Presentation, Best Tutorial, and Best Workshop. The awards will be given based on the audience's voting. Each award will include the author's name listed on the cover of the C++Now! website for that year and a plaque containing all the C++Now! conference information. SESSION TOPICS Topics of interest include, but are not restricted to, the following: * C++11 and how it changes life for users and library writers * General tutorial sessions on C++11, the C++11 Standardslibrary, and one or more Boost libraries * In-depth sessions on using specific Boost libraries * Case studies on using Boost * Experts panels * Advanced sessions on implementation techniques used within Boost libraries * Development workshops to extend or enhance existing Boost libraries * Workshops on design process * Infrastructure workshops such as Build tools, Website, Testing * Concepts and Generic Programming * Hardware and infrastructure presentations focused on how libraries can make better use of the technology * Software development tools and their application to C++ and or Boost * Other topics likely to be of great interest to Boost users and developers Interactive and collaborative sessions are encouraged, as this is the style of learning and participation that has proven most successful at such events. Sessions can be tutorial based, with an emphasis on interaction and participant involvement, or workshop based, whether hands-on programming or paper-based, discussion-driven collaborative work. SESSION FORMATS Presentations Presentations focus on a practitioner's ideas and experience with anything relevant to C++11, Boost and users. Panels Panels feature three or four people presenting their ideas and experiences relating to C++11 and Boost's relevant, controversial, emerging, or unresolved issues. Panels may be conducted in several ways, such as comparative, analytic, or historic. Tutorials Tutorials are sessions at which instructors teach conference participants specific skills relevant to C++11 and Boost. Workshops Workshops provide an active arena for advancements In Boost-relevant topics. Workshops provide the opportunity for experienced practitioners to develop new ideas about a topic of common interest and experience. Author's Corner These were introduced at BoostCon 2008, and were a great Presentations success They are short (30 minute) sessions, focusing on tips on usage and design. In addition, we're looking to uncover the hidden design gems in Boost libraries. Tool Vendors We actively encourage tool vendors and ISP's to submit presentations proposals for a special Tool Vendors Session Track aimed at products related to Boost and C++ (compilers, libraries, tools, etc.). Other formats may also be of interest. Don't hold back a proposal just because it doesn't fit into a pigeonhole. SUBMITTING A PROPOSAL Standard Sessions are 60 minutes. You may submit a proposal for fractions or multiples of 90-minutes. Fractional proposals will be grouped into 60 minute sessions covering related topics. Longer sessions, such as tutorials and classes, will be assigned 90 minute, three hour (i.e. half day), or six hour (i.e. full day) time slots. Please include: * The working title. * Type of session: presentation, panel, tutorial, workshop, authors corner, vendor track, other. * A paragraph or two describing the topic covered, suitable for the conference web site. * Proposed length: 10-20 minute short talks, 45 minutes, 90 minutes, half day, full day. * Alternate lengths, if you are willing to make adjustments: 10- 20 minute short-talks, 45 minutes, 90 minutes, half-day, full day. * Audience: users, developers, both. * Level: basic, intermediate, advanced. * A biography, suitable for the conference web site. * Your contact information (will not be made public). SUBMISSION DETAILS All submissions should be made through the EasyChair conference management system: http://www.easychair.org/conferences/?conf=cppnow2012. If you have not already registered at EasyChair, you will need to do so in order to submit your proposal. All submissions will go through a peer review process. Authors are invited (but are not required) to submit PDF versions of full papers of up to 10 pages in ACM conference proceedings format (see http://www.acm.org/sigs/publications/proceedings-templates) The full papers are not required unless you want them published in the proceedings. All accepted proposals will be made available in the Association for Computing Machinery (ACM) Digital Library (approval pending). Best papers, after further reviews, will be considered to be book chapters or journal articles in a renowned journal. The session materials go on the C++Now! website and will be available to attendees. For general information on the C++Now! 2012 paper submission or the scope of technical papers solicited, please refer to the conference website at www.cppnow.org. For any other questions about the submission process or paper format, please contact the Program Committee at cppnow2012(a)easychair.com. If you have any technical problems with EasyChair, please contact EasyChair for help. Note: Presenters must agree to grant a non-exclusive perpetual license to publish submitted materials, either electronically or in print, in any media related to C++ Now!. Hartmut Kaiser, email: hartmut.kaiser(a)gmail.com (Program Committee Chair) Dave Abrahams, email: dave(a)boostpro.com (Conference Chair) On behalf of the conference organizers

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Quick Unit Test Question
by Brad Tilley 10 Jan '12

10 Jan '12

Hey everyone, I can make BOOST_CHECK produce a failure message like this: BOOST_AUTO_TEST_CASE( test_case2 ) { BOOST_CHECK( 1+1 == 3 ); } But when I try BOOST_WARN, all tests pass: BOOST_AUTO_TEST_CASE( test_case3 ) { BOOST_WARN( 1+1 == 3 ); } Running 3 test cases... *** No errors detected Perhaps I'm doing something wrong. Can someone point me in the right direction? Both BOOST_REQUIRE and BOOST_CHECK work OK. It's only BOOST_WARN that does not work for my testing. Thanks, Brad

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