August 2012 - Boost-users - lists.boost.org

[interprocess] Determine size of managed_shared_memory
by Kai Benndorf 12 Oct '19

12 Oct '19

Hi all, I want to create a managed_shared_memory in exactly the size I needed. Therefore I do something like this: size = sizeof( common_managed_shared_memory ); size += sizeof( MyClassInSharedMem ); managed_shared_memory segment(create_only, "name", size ); MyClassInSharedMem allocates itself some memory by segment->allocate(). I added this also to the size, but get a boost::interprocess::bad_alloc exception on allocating this additional memory. Are there some magic bytes I forgot to add? Many thanks in advance Kai

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[statechart] Passing parameters from event to State Local Storage
by Christophe Bourez 16 Nov '16

16 Nov '16

I need to maintain a parameter into the state local storage. This parameter is initially contained in the event that causes the transition to the target state. I give hereafter a small illustrative example. typename sc = boost::statechart; class EvTest : public sc::event<EvTest> { public: EvTest(std::size_t val) : value(val) {} std::size_t getValue() const { return this->value; } private: std::size_t value; }; class MyStateMachine; class StSource; class StTarget; class StSource : public sc::simple_state<StSource, MyStateMachine> { public: typedef sc::custom_reaction<EvTest> reactions; sc::result react(const EvTest &event) { // How to pass event.getValue() to the target state ? transit<StTarget>(); } }; class StTarget : public sc::simple_state<StTarget, MyStateMachine> { public: StTarget(std::size_t val) : val(value) {} private: std::size_t value; }; Thanks, Christophe

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Statechart serialization
by mbrodeur65 04 Mar '15

04 Mar '15

Hi, I'm looking for a solution to serialize boost::statechart objects. I'm aware that this feature is on the statechart library todo list but was wondering if there are any workaround to achieve this with the latest boost release (1.34) ? thanks for your help ! mbrodeur65 -- View this message in context: http://www.nabble.com/Statechart-serialization-tf4131326.html#a11749139 Sent from the Boost - Users mailing list archive at Nabble.com.

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[Thread] Read-write locks
by lfrfly＠icqmail.com 18 Sep '14

18 Sep '14

I'm trying to create a standard read/write lock using Boost Threads, and I'm having a bit of difficulty mapping the Boost concepts onto the usual ones. A read/write lock should have several states: Locked for reading (multiple threads may lock at once), locked for writing (only one thread may lock, and no threads may be locked for reading at the same time), and unlocked. Ideally it would be nice if an RWL which is locked for reading may temporarily upgrade to locked for writing, then return to the locked for reading state. Boost supports several relevant notions of locking: shared locking, upgrade locking, and exclusive locking. This to me is a confusing distinction. In particular, a shared_mutex seems appropriate as the basis for a RWL, but is lock_upgrade() the equivalent of a write lock and lock_shared the equivalent of a read lock? This is unclear. If "upgrade locking" is not the same as "exclusive locking", then is an upgrade lock actually exclusive? Could someone please clarify this.

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[Statechart] How to decide between post_event and process_event atrun time ?
by Philippe DAVID 22 Jul '14

22 Jul '14

Hi, I have a method in which I want to post/process an event. The thing is, this method can be called from outside the state machine (so I need to call process_event), or indirectly by a reaction of the state machine (in this case I must call post_event since process_event is not reentrant). I don't want to write 2 distinct methods to do this (one that calls post, and the other process), I would much rather prefer adding a 'if' in my method that tells me if I have to call process_event or post_event (if I'm being called indirectly by the state machine or not). Is there a way to do this with statechart ? regards, Philippe

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[asio] resolver::cancel() problem
by Matthew Edwards 14 Mar '14

14 Mar '14

In my application (and a separate test program) it seems as though the cancel() function on the resolver does not work as intended. For async resolves, the cancel functionality should abort them immediately and pass an 'operation aborted' error code to the callback handler. In my tests, I will resolve an invalid domain (this causes the resolve to take a few seconds, to demonstrate the problem), sleep for 100ms, then call cancel on the resolver object. No cancelling actually occurs, and the callback is simply triggered after a few seconds with a "No host found" error code, not the expected operation aborted. Has anyone experienced this before, or know how I might be using the resolver incorrectly?

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[BGL] Having a cost function as weight map
by Maxime van Noppen 06 Sep '13

06 Sep '13

Hi, I can't find how to do this pretty basic thing : having a function instead of a field to compute the cost of edges for various path finding algorithms. I couldn't find the answer in the documentation and Google was of no help. Did I miss something obvious ? Example : ------------------- #include <boost/graph/dijkstra_shortest_paths.hpp> #include <boost/graph/graph_traits.hpp> #include <boost/graph/adjacency_list.hpp> struct my_edge { double cost() const { return cost_ * 2; } double cost_; }; struct my_node { }; int main() { typedef boost::adjacency_list< boost::vecS, boost::vecS, boost::directedS, my_node, my_edge > graph_t; typedef boost::graph_traits<graph_t>::vertex_descriptor vertex_t; graph_t graph; vertex_t v /*= ... */; using boost::weight_map; // Works : boost::dijkstra_shortest_paths(graph, v, weight_map(boost::get(&my_edge::cost_, graph))); // Doesn't compile : //boost::dijkstra_shortest_paths(graph, v, // weight_map(boost::get(&my_edge::cost, graph))); } ------------------- Thanks ! -- Maxime

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Identify cycles in a undirected graph
by NsPx 20 Aug '13

20 Aug '13

Hi all, I use undirected_dfs to detect all cycles in a undirected graph. I detect a cycle with DFSVisitor.back_edge(e,g) but how can I get the list of vertices defining this cycle ? Thanks by advance

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Is boost::this_thread::sleep_for interruption point?
by Serg Gulko 23 May '13

23 May '13

Hello! According to documentation(v 1.50.0) call boost::this_thread::sleep_for can be interrupted. For some reason this functionality not works for me. Here is code sample: //Simple thread function void Test::worker(int delay) { try { boost::this_thread::sleep_for(boost::chrono::milliseconds(delay)); cout << "Doing some work" << endl; } catch (boost::thread_interrupted const& e) { cout << "INTERRUPTED" << endl; } } //Far in the code boost::thread workerThread(boost::bind(&Test::worker, this, 1200)); boost::this_thread::sleep(boost::posix_time::milliseconds(30)); workerThread.interrupt(); boost::this_thread::sleep(boost::posix_time::milliseconds(1500)); I always getting 'Doing some work'... -- View this message in context: http://boost.2283326.n4.nabble.com/Is-boost-this-thread-sleep-for-interrupt… Sent from the Boost - Users mailing list archive at Nabble.com.

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can't get first example in boost tutorial to work
by 7stud 11 Mar '13

11 Mar '13

I'm trying to install boost on mac osx 10.4.7. I followed the tutorial "Getting Started on Unix Variants" found here: http://www.boost.org/doc/libs/1_35_0/ more/getting_started/unix-variants.html Following the instructions in the tutorial, I installed boost in /usr/local as instructed, so my directory structure is: /usr/local/boost_1_34_1/boost But when I run the first example in the tutorial: #include <boost/lambda/lambda.hpp> #include <iostream> #include <iterator> #include <algorithm> int main() { using namespace boost::lambda; typedef std::istream_iterator<int> in; std::for_each(in(std::cin), in(), std::cout << (_1 * 3) << " " ); } I get the error(among others): error: boost/lambda/lambda.hpp: No such file or directory If I change the include path to: #include </user/local/boost_1_34_1/boost/lambda/lambda.hpp> I get the error(among others): error: boost/lambda/core.hpp: No such file or directory But core.hpp is in the lambda directory: /usr/local/boost_1_34_1/boost/lambda$ ls algorithm.hpp control_structures.hpp lambda.hpp bind.hpp core.hpp loops.hpp casts.hpp detail numeric.hpp closures.hpp exceptions.hpp switch.hpp construct.hpp if.hpp I'm using the Xcode 2.4 IDE to run my C++ programs. I also tried to execute the program from the command line with the original include path: #include <boost/lambda/lambda.hpp> but I get the same error: ~/2testing/dir1$ g++ prog1.cpp prog1.cpp:1:35: error: boost/lambda/lambda.hpp: No such file or directory prog1.cpp: In function 'int main()': prog1.cpp:8: error: 'boost' has not been declared prog1.cpp:8: error: expected namespace-name before ';' token prog1.cpp:8: error: '<type error>' is not a namespace prog1.cpp:11: error: '_1' was not declared in this scope I get the same errors again with the full include path: #include </user/local/boost_1_34_1/boost/lambda/lambda.hpp> $ g++ prog1.cpp In file included from prog1.cpp:1: /usr/local/boost_1_34_1/boost/lambda/lambda.hpp:14:33: error: boost/lambda/core.hpp: No such file or directory /usr/local/boost_1_34_1/boost/lambda/lambda.hpp:21:52: error: boost/lambda/detail/operator_actions.hpp: No such file or directory /usr/local/boost_1_34_1/boost/lambda/lambda.hpp:22:61: error: boost/lambda/detail/operator_lambda_func_base.hpp: No such file or directory /usr/local/boost_1_34_1/boost/lambda/lambda.hpp:23:63: error: boost/lambda/detail/operator_return_type_traits.hpp: No such file or directory /usr/local/boost_1_34_1/boost/lambda/lambda.hpp:26:45: error: boost/lambda/detail/operators.hpp: No such file or directory /usr/local/boost_1_34_1/boost/lambda/lambda.hpp:30:46: error: boost/lambda/detail/member_ptr.hpp: No such file or directory prog1.cpp: In function 'int main()': prog1.cpp:8: error: 'boost' has not been declared prog1.cpp:8: error: expected namespace-name before ';' token prog1.cpp:8: error: '<type error>' is not a namespace prog1.cpp:11: error: '_1' was not declared in this scope What path should I be using? Or, should I set an environment variable somewhere?

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[Program Options] terminate parsing after first positional argument
by Stuart Pook 22 Jan '13

22 Jan '13

Hello, How can I tell Boost Program Options to stop parsing the arguments as soon as it finds a positional argument? I'd like to be able to parse the argument list "-v chmod -R -v 600 foo" as having one argument for my program (-v) and the rest as a std::vector of std::string (including the -v). In the attached program I have tried 2 different approaches. The first uses multitoken with the arguments "--command date -u -v", it fails because "-u" isn't known. The second uses collect_unrecognized with "chmod -R -v 600", it doesn't work because -v is interpreted by boost and doesn't end up in the vector. As someone said back in 2005, perhaps I'm trying to write xargs: http://thread.gmane.org/gmane.comp.lib.boost.user/9529/focus=9641 I know that I can ask my users to write a.out -v -- chmod -R -v 600 foo but I don't want to do that. I want them to write "a.out -v chmod -R -v 600 foo". The first positional argument should should tell boost to stop processing. Another slightly different question. If I have a multitoken option that takes doubles how can I get it to accept negative values? If I give my program "--floats 1 8 -4 6" where --floats starts a multitoken option that accepts double, I get an exception saying that "-4" is an unknown option. thanks Stuart This is what my test program gives me with boost 1.50: argv: dd --command date -u -v unrecognised option '-u' Allowed options: -v [ --verbose ] verbose --command arg command to run 2nd try argv: dd chmod -R -v 600 I'm verbose v: chmod -R 600 3rd try argv: dd --floats 1 8 -4 6 unrecognised option '-4' Allowed options: -v [ --verbose ] verbose -f [ --floats ] arg numbers and my program (formatted to fit in 80 characters) #include <boost/program_options.hpp> #include <boost/range/algorithm.hpp> #include <boost/program_options/parsers.hpp> #include <boost/program_options/options_description.hpp> #include <iostream> namespace po = boost::program_options; #define nelements(a) (sizeof (a) / sizeof (a)[0]) void print(char const * * b, char const * * e) { std::cout << "argv: "; std::copy(b, e, std::ostream_iterator<char const *>(std::cout, " ")); std::cout << std::endl; } int main(int argc, char ** argv) { { bool verbose; std::vector<std::string> command; po::options_description desc("Allowed options"); desc.add_options() ("verbose,v", po::bool_switch(&verbose)->default_value(false), "verbose") ("command", po::value<std::vector<std::string> >(&command) ->multitoken(), "command to run") ; char const * args[] = { "dd", "--command", "date", "-u", "-v", 0 }; print(args, args + nelements(args) - 1); po::variables_map vm; try { po::store(po::command_line_parser(nelements(args) - 1, args) .options(desc).run(), vm); po::notify(vm); if (verbose) std::cout << "I'm verbose\n"; std::cout << "command: "; boost::copy(command, std::ostream_iterator<std::string>(std::cout, " ")); std::cout << std::endl; } catch (boost::program_options::unknown_option & x) { std::cerr << x.what() << "\n" << desc << "\n"; } } std::cout << "2nd try\n"; { bool verbose; po::options_description desc("Allowed options"); desc.add_options() ("verbose,v", po::bool_switch(&verbose)->default_value(false), "verbose") ; char const * args[] = { "dd", "chmod", "-R", "-v", "600", 0 }; print(args, args + nelements(args) - 1); po::variables_map vm; po::parsed_options parsed = po::command_line_parser(nelements(args) - 1, args). options(desc).allow_unregistered().run(); try { po::store(parsed, vm); } catch (boost::program_options::unknown_option & x) { std::cerr << x.what() << "\n" << desc << "\n"; exit(2); } po::notify(vm); if (verbose) std::cout << "I'm verbose\n"; std::cout << "v: "; std::vector<std::string> v = po::collect_unrecognized( parsed.options, po::include_positional); boost::copy(v, std::ostream_iterator<std::string>(std::cout, " ")); std::cout << std::endl; } std::cout << "3rd try\n"; { bool verbose; std::vector<double> f; po::options_description all("Allowed options"); all.add_options() ("verbose,v", po::bool_switch(&verbose)->default_value(false), "verbose") ("floats,f", po::value<std::vector<double> >(&f)->multitoken(), "numbers") ; char const * args[] = { "dd", "--floats", "1", "8", "-4", "6", 0 }; print(args, args + nelements(args) - 1); po::variables_map vm; try { po::store(po::command_line_parser(nelements(args) - 1, args) .options(all).run(), vm); po::notify(vm); if (verbose) std::cout << "I'm verbose\n"; std::cout << "floats: "; boost::copy(f, std::ostream_iterator<double>(std::cout, " ")); std::cout << std::endl; } catch (boost::program_options::unknown_option & x) { std::cerr << x.what() << "\n" << all << "\n"; } } }

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[units] Missing quantity operator++, operator%
by Nathan Crookston 25 Oct '12

25 Oct '12

All, I'm in the process of switching my homegrown units system over to boost units. Some operators which I'm missing are the modulus and the pre and post increment operators. Looking through the archives I note an original review[1] which mentioned the absence of those operators. One response claimed that quantity<si::length, int> t = 5. ...; t++; was nonsensical as writing 5 m + 1, and the reviewer eventually agreed, citing possible confusion if the quantity type converted the initializer. Matthias Schabel seemed to respond favorably: 'I debated this for a while - the only problem is that there will be some value types with heterogeneous operator+ / operator- for which q + 1 is not the same type as q, but I guess that it is just OK for it to just give a compile error in those cases.' And Steven Watanabe said 'Will do.' I haven't found anything regarding the modulus operator. My question is, would a patch adding those operators be accepted? Thanks, Nate [1] http://lists.boost.org/Archives/boost/2007/03/119001.php

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Asio and ZeroMQ
by Matthias Vallentin 11 Oct '12

11 Oct '12

A while ago, Maciej Gajewski started an effort to use Asio to observe a ZeroMQ socket [1]. Based on his code, I put together a thin library that wraps the implementation details. Since other have requested a working example, here it is now at github: https://github.com/mavam/bmq Any feedback is highly appreciated. A basic usage example looks like this: #include <boost/asio/io_service.hpp> #include <bmq.h> int main() { boost::asio::io_service io; bmq::context ctx(1); bmq::component c(ctx, io); auto sink = c.add_sink(ZMQ_PAIR, "inproc://x"); c.subscribe(sink, [](bmq::message&& msg) { std::string str(static_cast<char*>(msg.data()), msg.size()); std::cout << str << std::endl; }); auto source = c.add_source(ZMQ_PAIR, "inproc://x"); bmq::message msg(const_cast<char*>("foo"), 3, nullptr); source->send(msg); // Execute message handler. io.poll(); return 0; } At this point, the library is really thin and only provides very rudimentary wrapping of ZeroMQ. In the future, I plan to extend it in order to facilitate applications that build on message-passing. The dataflow abstraction I envision is essentially a directed graph, where nodes represent components and edges communication links. 0mq provides the edges and the Asio handles asynchronous event processing at the component level. The motiviation is that this model lends itself well for scaling out distributed systems over large clusters. Matthias [1] http://permalink.gmane.org/gmane.network.zeromq.devel/9538

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[Sandbox - endian] Why is endian still in sandbox?
by Nathaniel J Fries 07 Oct '12

07 Oct '12

A fairly novel (at least when put up against more intricate labours like asio, filesystem, and their like) project which appears to be finished and would be a very useful companion to existing libraries sits in the sandbox. Is there a reason for this?

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[BGL] vecS for vertex container and vertex index adjustments
by Sergey Mitsyn 03 Oct '12

03 Oct '12

Hi all, I know that while using vecS for vertices one has no vertex iterator stability upon removing vertices. But I have a question if there exists something like vertex _index_ stability. The documentation says that indices for vertices are automatically adjusted so that they are still in contiguous range, but it is not specified how it is done. Is it okay to assume that if a vertex with an index I is removed, then vertices with indices < I have their indices unchanged, while vertices with indices > I have their indices decreased by one? The actual problem is removing all vertices meeting some condition. Is the following code ok? // traverse all vertices and remove those for which predicate // condition_to_remove_vertex returns true. // graph is adjacency_list<.., vecS, ...> vertex_iterator vi = vertices(graph).first, vi_end = vertices(graph).second; while (vi != vi_end) { if (condition_to_remove_vertex(vi, graph)) { vertices_size_type end_index = vertex_index[*vi_end] , vi_index = vertex_index[*vi]; remove_vertex_f(*vi, graph); // vi and vi_end are invalid --end_index; vi = vertices(graph).first + vi_index; vi_end = vertices(graph).first + end_index; // now vi and vi_end are valid again } else ++vi; } This way seems to be more effective than to start iteration again every time a vertex is removed. ------------ Sergey Mitsyn.

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[boost.build] Problems getting PDB files withs DLLs
by Jonathan Jones 19 Sep '12

19 Sep '12

Hi all, I'm having problems getting PDB files built with the DLLs using Boost 1.49 and Visual Studio 2010. I have both debug-symbols=on and debug-store=database specified, but the PDB files are never built. Am I missing something? Thanks, Jon

1 1

[boost] [contract] static_assert in contracts or not?
by Lorenzo Caminiti 17 Sep '12

17 Sep '12

Hello all, If static assertions make sense within contracts (preconditions, postconditions, and class invariants) is a questions that has been raised by both Vicente and Andrzej. I don't have a definitive answer so I'd like to discuss with the ML. On Wed, Aug 29, 2012 at 2:48 PM, Andrzej Krzemienski <akrzemi1(a)gmail.com> wrote: > (6) > Static assertions: is there any value in providing them, given that we > already have this ability in Boost? I see that N1962 decided to abandon > them; I am pretty sure the reason was that static_assert was already there. > They somehow do not fit conceptually into the model of preconditions, > postconditions and invariants. Precondition, for instance tries to detect a > run-time condition occurring immediately before a function is called this > time. Static assertion is not even executed then. What point is there in > putting such assertion into the precondition? Documentation says " static > assertions can be selectively disabled depending on where they are > specified [...] so it is still important to logically associate them with > preconditions, postconditions, etc." -- technically this sentence makes > logical sense, but can you think of a single example where this selective > disabling of assertions would be useful? What is the point in disabling > such assertions at all, if they cost you nothing in run-time? I propose to > remove them and give a sort of recommendation that software quality is > assured by using a number of fairly independent tools: DbC, concepts, > static assertions. I think we can break down the question in two parts. Let's assume N1962 is accepted into C++1x so we have both contracts and static_assert. 1) Would you expect to be able to use static_assert within contract assertions (preconditions, postconditions, and class invariants)? Note that only boolean conditions are allowed by N1962 within contracts, general code is not allowed, therefore this is not a trivial question. For example, would you expect to be able to do the following option A: template< typename To, typename From > To* memcopy ( To* to, From* from ) precondition{ static_assert(sizeof(To) >= sizeof(From), "destination too small"); static_assert(boost::is_convertible<From, To>::value, "incompatible types"); to; // pointer not null from; // pointer not null } { // ... } In this case, would it ever make sense to use static_assert in postcondition and/or class invariants even if that were allowed? Or would you just use static_assert in the body, option B: template< typename To, typename From > To* memcopy ( To* to, From* from ) precondition{ to; // pointer not null from; // pointer not null } { static_assert(sizeof(To) >= sizeof(From), "destination too small"); static_assert(boost::is_convertible<From, To>::value, "incompatible types"); // ... } I don't like this because the assertions are about the specifications (they assert a requirement of the interface) so they should go in the declaration and not in the implementation. Or maybe the assertions should be represented as concept requirements on To and From, option C: template< typename To, typename From > requires SizeofGreaterEqual<To, From>, Convertible<From, To> To* memcopy ( To* to, From* from ) precondition{ to; // pointer not null from; // pointer not null } { // ... } (Only we don't have concepts...) 2) Let's assume, we answered option A to question 1): template< typename To, typename From > To* memcopy ( To* to, From* from ) precondition{ static_assert(sizeof(To) >= sizeof(From), "destination too small"); static_assert(boost::is_convertible<From, To>::value, "incompatible types"); to; // pointer not null from; // pointer not null } { // ... } Would you expect these static_asserts to be disabled when precondition compilation and checking is turned off at compilation time? I'd think so. Thanks. --Lorenzo

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Fusion error: wrong number of template arguments (30, should be 20)
by Joost Kraaijeveld 11 Sep '12

11 Sep '12

Hi, I have the following error after an upgrade to Boost 1.49 (Debian Wheezy): /usr/include/boost/fusion/container/deque/detail/preprocessed/deque_initial_size30.hpp:14:196: error: wrong number of template arguments (30, should be 20) In file included from /usr/include/boost/mpl/aux_/include_preprocessed.hpp:37:0, from /usr/include/boost/mpl/vector.hpp:46, from /usr/include/boost/fusion/container/deque/detail/deque_initial_size.hpp:16, from /usr/include/boost/fusion/container/deque/deque.hpp:15, from /usr/include/boost/fusion/container/deque.hpp:11, from /usr/include/boost/fusion/container.hpp:14, from ../../../library/../include/Danu/DanuModelObjects/Login.hpp:12, from ../../../library/DanuModelObjects/Login.cpp:7: /usr/include/boost/mpl/aux_/preprocessed/gcc/vector.hpp:22:8: error: provided for 'template<class T0, class T1, class T2, class T3, class T4, class T5, class T6, class T7, class T8, class T9, class T10, class T11, class T12, class T13, class T14, class T15, class T16, class T17, class T18, class T19> struct boost::mpl::vector' I have defined the following: #define FUSION_MAX_VECTOR_SIZE 30 #define FUSION_MAX_MAP_SIZE 30 How can I solve this problem? TIA -- Groeten, Joost Kraaijeveld Askesis B.V. Molukkenstraat 14 6524NB Nijmegen tel: 024-3888063 / 06-51855277 fax: 024-3608416 web: www.askesis.nl

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[Range] insert algorithm fails if target is a map
by Robert Jones 11 Sep '12

11 Sep '12

The title says it all really. The failure occurs because the insert algorithm expects the container to provide a 3-arg insert of the form container.insert( position, begin, end ); whereas map's, multimap's and set's insert method only takes two arguments... map.insert( begin, end ); Is this limitation by design? It would be easy to provide specialisations for maps, mmaps and sets, but that would not be a completely general solution. - Rob.

3 3

Boost.Hash and enums
by Filip Konvička 07 Sep '12

07 Sep '12

Hi, In Boost 1.51, it looks to me like boost::hash_value no longer knows how to handle enums anymore. Is the following the right way to tell it to treat enums like ints? #if (BOOST_VERSION >= 105100) // Boost 1.51.0+ namespace boost { /// Enable hashing of enums. template<typename E> size_t hash_value( E const e, typename std::enable_if<std::is_enum<E>::value, E>::type def = static_cast<E>(0)) { return hash_value((int)e); } } #endif Is enum hashing support going to be added to the library in the future? Thanks, Filip

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[fusion] Wrapping a Fusion sequence
by Agustín K-ballo Bergé 04 Sep '12

04 Sep '12

I'm looking for a way to create a Fusion sequence wrapper that is itself a Fusion sequence and forwards all 'calls' to its wrapped sequence. Something in the lines of template< typename Sequence > struct sequence_wrapper { explicit sequence_wrapper( Sequence const& s ) : seq( s ){} Sequence seq; }; where sequence_wrapper< Sequence > is a Fusion sequence as well, and works just as Sequence would. The reason I need this is that I have several functions that operate on Fusion sequences (where all elements satisfy some special requirements), and I would like to add some syntax sugar for which I need a custom type to add overloaded operators to. I do not need the result of operations on a sequence_wrapper to return a sequence_wrapper as well, only the syntax sugar related calls would return a (manually) wrapped sequence. For instance, appending elements to a sequence using the comma operator (somewhat of a Boost.Assign for Fusion sequences): template< typename Sequence, typename T > sequence_wrapper< typename boost::fusion::result_of::push_back< Sequence const& , T >::type > operator,( Sequence const& seq, T const& v ) { return sequence_wrapper< typename boost::fusion::result_of::push_back< Sequence const& , T >::type >( boost::fusion::push_back( seq, v ) ) ; } What would be the best way to achieve this (if it is indeed supported by the library)? I'm particularly trying to avoid creating a Fusion sequence from scratch, as I would like to use whatever sequence is returned by Fusion operations. Would inheritance + specialization of `tag_of` to return the tag of the wrapped sequence just work? Or will I need to define a tag of my own and implement all required functions to just forward the call? Thank you in advance. Agustín K-ballo Bergé.- http://fusionfenix.com

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Trying to compile and use boost on proprietary complier similar to MPICH2 CXX
by Chris 04 Sep '12

04 Sep '12

Hi all, hope this is the right list for my question. So here it goes: When it try to use boost using a proprietary MPIC++ compiler I have no control over, I get the following errors: In file included from ../boost_1_43_0/boost/thread/detail/platform.hpp:17, from ../boost_1_43_0/boost/thread/thread.hpp:12, from ../boost_1_43_0/boost/thread.hpp:13, from test.cpp:37: ../boost_1_43_0/boost/config/requires_threads.hpp:47:5: error: #error "Compiler threading support is not turned on. Please set the correct command line options for threading: -pthread (Linux), -pthreads (Solaris) or -mthreads (Mingw32)" In file included from ../boost_1_43_0/boost/thread/thread.hpp:12, from ../boost_1_43_0/boost/thread.hpp:13, from test.cpp:37: ../boost_1_43_0/boost/thread/detail/platform.hpp:67:9: error: #error "Sorry, no boost threads are available for this platform." In file included from ../boost_1_43_0/boost/thread.hpp:13, from test.cpp:37: ../boost_1_43_0/boost/thread/thread.hpp:19:2: error: #error "Boost threads unavailable on this platform" The thing is, when I use the standard mpicxx from MPICH2, things work out fine. I'm now trying to find out if the problem lies in the complier, or if I simply did not compile and bootstrap boost properly. What I did when building boost is the following: ./bootstrap.sh --with-libraries=date_time,filesystem,serialization,iostreams,system,thread,mpi ./bjam cxxflags="-O2" release threading=multi link=static After bootstrap, I tried to manually edit the user-config.jam to add "using mpi ;" and explicitly added the path to the compiler, but this all did not change the above mentioned error when I try to compile my code that uses boost. Is this enough information for you to judge if I might have overlooked something when building boost? Many thanks, Chris

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filesystem directory_iterator run-time error during construction after upgrading to OSX Lion
by Martin Searancke 04 Sep '12

04 Sep '12

I have just upgraded my Mac to Lion and code that worked fine under snow leopard is giving me a run-time exception when constructing a directory_iterator. The error I am getting is "malloc: pointer being freed was not allocated" The line in question that raises this error is: for ( directory_iterator itr( my_path ); itr != end_itr; ++itr ) taken directly from the example and working fine under windows. This is version 1.49 installed with MacPorts. Is this a known problem? I found some vague references to a similar problem in an earlier version of boost but no solution. I have confirmed that I only have 1 copy of the headers and libs on the system and in the correct path. The date stamp on the files matches the last time I did a macports update so this should be the matching library for the header. Please note that I am a real novice to Mac development and have only just started porting code from windows for less than a month. Thanks in advance, Martin

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[traits, fusion, mpl] Basic question about is_base_of and template ancestors
by Rindeberg Magnus 04 Sep '12

04 Sep '12

Hello List! I have an issue understanding how to combine CRTP with the "is_base_of" trait when iterating over a fusion vector. I have tried to illustrate my problem in the test program below. The idea is to first "do stuff" to all instances of types derived from A and then "do stuff" to the ones derived from B. I just don't know what to write instead of "WHAT_GOES_HERE?" below. I have tried to use "::boost::mpl::_" in different ways to get the "type" type of B but failed miserably every time. I'm also curious about how to negate the "is_base_of" predicate. I tried using "not_<>" but that didn't work at all... Very thankful for any and all help! // Magnus P.S. Sorry if this question has been answered already! I have looked at the documentation, searched archives and the web but couldn't find the solution. Maybe I searched using the wrong keywords... #include <boost/type_traits.hpp> #include <boost/mpl/vector.hpp> #include <boost/fusion/include/mpl.hpp> #include <boost/fusion/container.hpp> #include <boost/fusion/include/at_key.hpp> #include <boost/fusion/include/for_each.hpp> #include <boost/fusion/include/filter_if.hpp> struct dostuff { template<typename T> void operator()(T const & x) const { // Do stuff here! } }; template<class D> struct A { }; template<class D, typename T> struct B { typedef T type; }; struct derived_from_A : public A<derived_from_A> { }; struct derived_from_B : public B<derived_from_B, int> { }; typedef ::boost::mpl::vector<derived_from_A, derived_from_B>::type typelist_type; ::boost::fusion::result_of::as_set<typelist_type>::type typeset_; int main(int argc, char ** argv) { dostuff ds; // This seems to be working! ::boost::fusion::for_each( ::boost::fusion::filter_if < ::boost::is_base_of<A< ::boost::mpl::_>, ::boost::mpl::_> > (typeset_), ds); #if(0) // Don't know how to do this! Preferably I'd like to check for inheritance from B. // If that isn't possible I'll settle for "not inheriting from A". ::boost::fusion::for_each( ::boost::fusion::filter_if < ::boost::is_base_of<B< ::boost::mpl::_, WHAT_GOES_HERE? >, ::boost::mpl::_> > (typeset_), ds); #endif }

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problems in compiling application using IBM XL C/C++ V12.1 and boost1.50.0
by Pravar 04 Sep '12

04 Sep '12

Hi All, I am getting compilation errors when I try to build my application code which includes some boost headers using IBM XL C/C++ compiler V12.1. ------------------------------------------------------------------------------------------------ "/opt/boost/include/boost/date_time/time_resolution_traits.hpp", line 71.21: 1540-0063 (S) The text "->" is unexpected. "/opt/boost/include/boost/date_time/time_resolution_traits.hpp", line 135.33: 1540-0040 (S) The text "<" is unexpected. "time_resolution_traits" may be undeclared or ambiguous. "/opt/boost/include/boost/date_time/time_resolution_traits.hpp", line 136.33: 1540-0040 (S) The text "<" is unexpected. "time_resolution_traits" may be undeclared or ambiguous. "/opt/boost/include/boost/date_time/time_resolution_traits.hpp", line 137.33: 1540-0040 (S) The text "<" is unexpected. "time_resolution_traits" may be undeclared or ambiguous. "/opt/boost/include/boost/date_time/posix_time/posix_time_config.hpp", line 40.44: 1540-0040 (S) The text "<" is unexpected. "date_time::time_resolution_traits" may be undeclared or ambiguous. ------------------------------------------------------------------------------------------------- These errors seems come due to the fact that this version of compiler is claimed to have more standard conformance than its predecessors. I confirmed from boost release notes of boost 1.50.0 that V12. of XL C/C++ supports this boost version. But still I encountered above errors. Should I use an older version of XL C/C++ compiler so that such errors can be avoided ? Does anybody encountered similar issues ? I am completely stuck at this point and would greatly appreciate any ideas to understand and resolve this. Thanks, Pravar DISCLAIMER: ----------------------------------------------------------------------------------------------------------------------- The contents of this e-mail and any attachment(s) are confidential and intended for the named recipient(s) only. It shall not attach any liability on the originator or NECHCL or its affiliates. Any views or opinions presented in this email are solely those of the author and may not necessarily reflect the opinions of NECHCL or its affiliates. Any form of reproduction, dissemination, copying, disclosure, modification, distribution and / or publication of this message without the prior written consent of the author of this e-mail is strictly prohibited. If you have received this email in error please delete it and notify the sender immediately. . -----------------------------------------------------------------------------------------------------------------------

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