February 2010 - Boost-users

[boost-program-options] Minor documentation bug
by mmocny 26 Feb '10

26 Feb '10

To whom it may concern, The last code example in the section "Option Details" on page http://www.boost.org/doc/libs/1_42_0/doc/html/program_options/tutorial.html, the line: $bin/gcc/debug/options_description ...should be bold, to match the rest of the syntax. I found the example confusing until I properly parsed what was meant to be written. Might I also suggest a space after the $ or even* "shell> command" * -Michal Mocny

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[boost-users][array] Passing by reference
by Ryan McConnehey 26 Feb '10

26 Feb '10

I'm wanting to pass a boost::array by reference to a function. Normally, this isn't a problem. My first approach yielded a compiler error stating boost::array needs template parameters. When adding the template parameters (approach 2) the compiler then states boost::array needs T to be a compile time constant. I want the function to be able to take different boost::array sizes. Can boost::array be passed by reference without knowing the size of the array at compile time? Any help would be great. Ryan Approach 1 void extract (boost::array & var) {} Approach 2 template<typename T, typename S> void extract (boost::array<T, S> & var) {}

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Boost.Serialization warning C4540 on MSVC
by Antti Alho 26 Feb '10

26 Feb '10

Hi, I'm using Boost.Serialization for my project and have run into a cryptic warning message. Although it doesn't seem to actually do any harm on run-time I would like to know what it means, and possibly how I can fix it without #pragma disabling it. The relevant code and the entire warning can be found here: Codepad paste <http://codepad.org/MVx2O6dC> The error message was produced by Visual Studio 2008. Since I'm not perfectly sure what the correct syntax is supposed to be regarding lines 74 and 75 when dealing with classes using multiple inheritance and since I couldn't find documentation regarding the subject those could very well be the source of my problems (although it seems to do what it is expected to do). All help greatly appreciated, thanks in advance.

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[program_options][1.35] validating string value
by Soumen 26 Feb '10

26 Feb '10

Hi, My option (say, "opt1") can take any of only few possible string type values (say, "value1", "value2", "value3" and "value4"). Is there anyway to specify this such that if any other value, say - "valueXX", is passed to "opt1", it throws an error? If yes, can someone point me to documentation or sample code snippet to show how to do this? Or, explicitly, checking against these possible values is my only option? Regards, ~ Soumen -- View this message in context: http://old.nabble.com/-program_options--1.35--validating-string-value-tp276… Sent from the Boost - Users mailing list archive at Nabble.com.

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Combing 2 memory pools
by Michael Kennard 26 Feb '10

26 Feb '10

Short version: I'm using the boost pool library for allocation of a linked list of small objects. Now I want to append one linked list onto the end of another. Thus I also want to combine the memory pools. I don't see this functionality in the interface documentation. Is there a way to easily combine two memory pools? Longer version: The list is a member of a class which manages it and has methods for creating and deleting list elements. The memory pool is also a member of this class. Before using the memory pool, each list element was allocated individually and deleted individually. With the pool, deletion is easier because you just destroy the pool instead of deleting each list element individually. Merging two lists together before I used the pool was just a matter of appending one linked list onto the end of the other (easy, and code not shown). But now that I'm using the pool I've got to figure out how to merge the two pools into one. Here's a simplified version of the code (which I haven't tried to compile): struct element { int m_data; element* m_next; }; class MyList { public: MyList(); // constructor void NewElement (int data) { element* new_element = static_cast<element*>(m_pool.malloc()); new_element->m_data = data; // add to beginning of list new_element->next = m_list; m_list = new_element; } element* m_list; boost::pool m_pool; }; -- Michael Kennard Aquaveo (www.aquaveo.com)

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fusion Transformation function passed to transform
by Hicham Mouline 26 Feb '10

26 Feb '10

Hello, The transformation function to pass to fusion::transform() function and metafunction are hard to get right, in particular the embedded inner result struct because of the fact that the template argument of result is a "function signature" There is only the 1 simple example in libs/fusion/doc/html/fusion/algorithm/transformation/metafunctions/transform.html I for one would love to see another example where the fusion vector has different types, and where the result of transformation function depends on each type of the sequence transform is applied on. In the meantime, I am writing something like this: struct extract_rule { template <typename Signature> struct result; //// primary template template <typename Holder> struct result< extract_rule(const Holder) > { //// is this always a specialization of the primary? typedef .... type; }; template <typename Holder> typename result<extract_rule(const Holder)>::type operator()( const Holder& h ) const { .... } }; Does this look right? regards,

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function pointers and anys
by Alan Tennant 25 Feb '10

25 Feb '10

I created a pointer to a function, I am able to call the function though the pointer as well as move the pointer, as I would expect. I put it into a boost::any. How do I get the pointer out of the any so that I can call it? I'm having difficulty using the any_cast to do it.

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[Asio] streambuf exceptions
by Dylan Klomparens 25 Feb '10

25 Feb '10

I'm using an asio::streambuf to read and write data to a socket. Despite my best efforts, I can't get the streambuf to throw an exception if I consume too much. I'm trying to get it to throw an exception so I can test an error case. The documentation says streambuf::consume will throw an std::length error if the requested amount to read is greater than the input stream size ( http://www.boost.org/doc/libs/1_42_0/doc/html/boost_asio/reference/basic_st…) But in my test program, this did not happen. Do I need to enable exception throwing somehow? Or is streambuf working as intended and not supposed to throw an exception? Here is my test program: #include <iostream> #include <boost/asio.hpp> using namespace std; int main() { char in[] = "hello"; char out[6] = {0, 0, 0, 0, 0, 0}; boost::asio::streambuf s; s.sputn(in, sizeof(in)); s.sgetn(out, sizeof(in)); cout << out << endl << s.size() << endl; s.consume(1000); return 0; }

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[graph] [parallel graph] property and distributedS
by Andreas Zilian 25 Feb '10

25 Feb '10

Hello, using the parallel graph library, I try to combine the property definition for a vertex typedef property<vertex_rank_t, int, VVV> vertex_property_t; with the vertex storage type distributedS in a distributed adjacency_list. Unfortunately this does not compile in the form listed below. Now, I would like to learn why the code actually compiles fine if a) distributedS is changed to vecS (see typdef vertex_storage_t), b) property<vertex_rank_t, int, VVV> is changed to VVV (see typedef vertex_property_t). I need the property vertex_rank_t for redistribution of the graph. Thank you very much, Andreas #include <boost/graph/use_mpi.hpp> #include <boost/graph/distributed/adjacency_list.hpp> #include <boost/graph/distributed/mpi_process_group.hpp> using namespace boost; using boost::graph::distributed::mpi_process_group; struct VVV { friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { } }; //typedef vecS vertex_storage_t ; typedef distributedS<mpi_process_group, vecS> vertex_storage_t ; //typedef VVV vertex_property_t; typedef property<vertex_rank_t, int, VVV> vertex_property_t; typedef adjacency_list<vecS, vertex_storage_t, directedS, vertex_property_t> G; int main (int argc, char* argv[]) { boost::mpi::environment env(argc,argv); G g(10); }

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Problem creating a circular buffer in shared memory using Boost
by Cuneyt Taskiran 25 Feb '10

25 Feb '10

Hi, I am trying to create a circular buffer in shared memory using Boost circular_buffer and Interprocess libraries. I compiled and ran the the example given in the Interprocess documentation<http://www.boost.org/doc/libs/1_42_0/doc/html/interprocess/quick_guide.html…>for creating a vector in shared memory with no problem. However, when I modify it to use the Boost circular_buffer as: int main(int argc, char *argv[]) { managed_shared_memory segment(create_only, "MySharedMemory", 65536); const ShmemAllocator alloc_inst (segment.get_segment_manager()); MyCircBuffer *myCircBuf = segment.construct<MyCircBuffer>("MyCircBuffer")(alloc_inst); return 0; } I get a compilation error (caused by segment.construct()). Any idea what I am doing wrong? Is it because circular_buffer is not one of the containers listed in /boost/interprocess/containers, i.e. it's not compatible with Interprocess? Thanks, C

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