April 2007 - Boost-users - lists.preview.boost.org

[BLL] Right usage of he placeholder _1 ?
by pheres 26 Apr '07

26 Apr '07

Hello, I've two problems so far with a simple for_each: 1. vector<string*> v2(10); fill(v2.begin(), v2.end(), new string("hehe")); for_each(v2.begin(), v2.end(), cout << *_1 << " "); // works for_each(v2.begin(), v2.end(), delete _1 ); // error // error: type ‘const struct // boost::lambda::lambda_functor<boost::lambda::placeholder<1> // >’ argument given to ‘delete’, expected pointer Shouldn't the placeholder _1 actually become a (string-)pointer as it obviously does in the expression above ( cout << *_1 << " " )? 2. Is it possible to call member functions from an placeholder of a boost-like lambda expression? vector<string> v3(10); fill(v3.begin(), v3.end(), "hoho"); for_each(v3.begin(), v3.end(), cout << _1->c_str() << " "); // error // error: base operand of ‘->’ has non-pointer type ‘const // boost::lambda::lambda_functor<boost::lambda::placeholder<1> >’ Thank you for any input!

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[program_options] Problem with custom parser and boolean options
by Tarjei Knapstad 26 Apr '07

26 Apr '07

I'm trying to support non-conventional syntax on the form "option=value", where boolean options are given as "option=on" or "option=off". For this I've implemented a custom parser that splits a string on the '=' character and returns a std::pair<std::string, std::string> containing the option and it's value. This works fine for most things except I can't figure out how to handle boolean options. I've tried the following which just makes the option "disappear" if it's set to "off" and returns a pair with the option and an empty string as value if it's set to "on". It works for "off", but for "on" I get an exception stating "extra parameter in 'option'". Is there any way to get around this? Here's my custom parser: //---------------- START: code std::pair<std::string, std::string> custom_parser(std::string const & s) { std::pair<std::string, std::string> option; if (s.find("=") != std::string::npos) { std::vector<std::string> slist; boost::split(slist, s, boost::is_any_of("=")); if (slist[1] == "on") { option.first = slist[0]; } else if (slist[1] == "off") { // Return an empty option if the feature is turned off } else { option.first = slist[0]; option.second = slist[1]; } } return option; } //-------------- END: code Any help appreciated! Regards, -- Tarjei

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[multi_index] inherit from a multi_index
by Guillaume Lazzara 26 Apr '07

26 Apr '07

Hi, I would like to know if it is safe to create a struct and make it inherit from a multi_index. Actually I already tried but I got this error: /usr/include/boost/multi_index_container.hpp:204: warning: base class 'struct boost::multi_index::detail::header_holder<boost::multi_index::detail::ordered_index_node<boost::multi_index::detail::index_node_base<vcsn::InitialValue<vcsn::rat::exp<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, float> > > >, boost::multi_index::multi_index_container< [...] >, boost::multi_index::indexed_by<boost::multi_index::ordered_unique<boost::multi_index::member<vcsn::InitialValue<vcsn::rat::exp<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, float> >, [...] >' should be explicitly initialized in the copy constructor Is it an issue due to Boost or because I'm doing something really bad? Thanks, -- Guillaume Lazzara Epita CSI 2008

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regex_replace -- format_default
by ivan＠0x4849.net 26 Apr '07

26 Apr '07

Hi I am trying to use boost::regex_replace but I am having trouble understanding the format to use for the the format string. The Ecma-262.pdf rules for how to create a format string seem quite terse. Does anyone know of a reference that has some more examples? Here is the code I am trying to write: #include <boost/regex.hpp> #include <string> #include <iostream> int main(int argc, char** argv) { std::string str; boost::regex expression("abc"); std::string fmt(""); // WHAT GOES HERE? fn = "abcabcabc"; boost::regex_replace(str, expression, fmt); std::cout << str << std::endl; return 0; } Thank you, Ivan Novick http://www.0x4849.net

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boost::random::normal_distribution
by Jeffrey Brent McBeth 26 Apr '07

26 Apr '07

#include <boost/random.hpp> #include <iostream> int main(int argc, char *argv[]) { boost::mt19937 eng; boost::normal_distribution<> norm(0,1); std::cout << norm(eng) << std::endl; } Gives me a NaN everytime. Looking at the code, it doesn't really surprise me, as _r1 = eng(); _r2 = eng(); _cached_rho = sqrt(-result_type(2)*log(result_type(1)-_r2)); would only work if eng were in the range (0,1) with 0 being degenerate, and 1 being undefined. Looking through the mt19937, that is returning a full UInt32. Perhaps those two eng() should be replaced by uniform_01? Jeffrey McBeth -- ---------------------------------------------------------------------------- Hofstadter's Law states: It always takes longer than you expect, even when you take into account Hofstadter's Law. ----------------------------------------------------------------------------

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newbie problem with Boost.Serialization
by John Pye 26 Apr '07

26 Apr '07

Hi all, I have some trouble with the Boost.Serialization library. I have compiled the 'demo.cpp' example, and now I am trying to distill it a little, so that I can understand how to apply it to my own polymorphic class hierarchy. However I keep seeing the same error message, and can't work out what it means. In /usr/include/boost/archive/detail/oserializer.hpp:567 there are some comments about the error message I'm seeing but I don't understand what those comments mean. I'm using Boost 1.33.1-7ubuntu1 on Ubuntu 6.10. Any help would be much appreciated! Cheers JP Here is the error message: --------------8<--------------- jpye@john:~/boosttest$ scons scons: Reading SConscript files ... scons: done reading SConscript files. scons: Building targets ... g++ -o ser1.o -c ser1.cpp /usr/include/boost/archive/detail/oserializer.hpp: In function 'void boost::archive::save(Archive&, T&) [with Archive = boost::archive::text_oarchive, T = dd]': /usr/include/boost/archive/basic_text_oarchive.hpp:78: instantiated from 'void boost::archive::basic_text_oarchive<Archive>::save_override(T&, int) [with T = dd, Archive = boost::archive::text_oarchive]' /usr/include/boost/archive/detail/interface_oarchive.hpp:78: instantiated from 'Archive& boost::archive::detail::interface_oarchive<Archive>::operator<<(T&) [with T = dd, Archive = boost::archive::text_oarchive]' ser1.cpp:43: instantiated from here /usr/include/boost/archive/detail/oserializer.hpp:567: error: invalid application of 'sizeof' to incomplete type 'boost::STATIC_ASSERTION_FAILURE<false>' scons: *** [ser1.o] Error 1 scons: building terminated because of errors. jpye@john:~/boosttest$ -------------------------------------- Here is the code that was being compiled: -----------------8<--------------- jpye@john:~/boosttest$ cat ser1.cpp #include <iomanip> #include <iostream> #include <fstream> #include <string> #include <boost/archive/tmpdir.hpp> #include <boost/archive/text_iarchive.hpp> #include <boost/archive/text_oarchive.hpp> #include <boost/serialization/base_object.hpp> #include <boost/serialization/utility.hpp> #include <boost/serialization/list.hpp> class dd{ friend std::ostream&operator<<(std::ostream&,const dd&); friend class boost::serialization::access; double x,y; template<class Archive> void serialize(Archive & ar, const unsigned int /* file_version */){ ar & y & x; } public: // every serializable class needs a constructor dd(){}; dd(double x, double y) : x(x), y(y) {} }; std::ostream & operator<<(std::ostream &os, const dd &d) { return os << d.x << ' ' << d.y; } int main(int argc, char *argv[]){ dd D(10,20); int x = 5; std::cerr << D << std::endl; std::ofstream ofs("test.txt"); boost::archive::text_oarchive oa(ofs); oa << x; oa << D; return 0; } -------------------------------------- And, just for completeness, my build file: --------------8<---------------- jpye@ascendserver:~/boosttest$ cat SConstruct Program("test",["ser1.cpp"], LIBS=['boost_serialization']) ------------------------------------

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Re: [Boost-users] [Serialization, XML] - how to get info "where am i?" in serialization helper (encoding is not recursive)?
by Frank Bergemann 26 Apr '07

26 Apr '07

Hi Gary, you made my day - many thanks! Seems we have done similar things :-) Just a final question: Could you tell me, what these defines are about? I didn't adopt them and the modules seems to be ok without. > > #define BOOST_ARCHIVE_CUSTOM_IARCHIVE_TYPES datastore::ConfigIArchive > #define BOOST_ARCHIVE_CUSTOM_OARCHIVE_TYPES datastore::ConfigOArchive > Cheers! \Frank _______________________________________________________________ SMS schreiben mit WEB.DE FreeMail - einfach, schnell und kostenguenstig. Jetzt gleich testen! http://f.web.de/?mc=021192

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BOOST_CLASS_EXPORT conflicts with xml_iarchive.hpp
by Oleg V. Zhylin 26 Apr '07

26 Apr '07

Hello All, Could someone please help me to understand why code below fails to compile with STATIC_ASSERTION_FAILURE in basic_xml_iarchive.hpp // If your program fails to compile here, its most likely due to // not specifying an nvp wrapper around the variable to // be serialized. BOOST_STATIC_ASSERT(0 == sizeof(T)); Code does compile if BOOST_CLASS_EXPORT line is commeted out. #include <boost/archive/xml_iarchive.hpp> class A { friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & i; } int i; }; #include <boost/serialization/export.hpp> BOOST_CLASS_EXPORT(A) int main() { } WBR Oleg V. Zhylin ovz(a)yahoo.com __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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Filesystem - Recurse directories function?
by Jeff 25 Apr '07

25 Apr '07

I am wondering if someone would possibly post a recursive function that prints out all files and sub-directories. I've never created a recursive function before and I'm having problems getting all files and directories to print. Thank You

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Boost topological_sort attempts to advance a dereferencable iterator 20 steps outside the valid range
by Stephen Torri 25 Apr '07

25 Apr '07

I am still trying to understand why boost graph's topological_sort fails for a test program I have made to sort five vertexes. Originally I compiled this program against boost 1.33.1 on a Fedora Core 6 system using gcc-4.1.1. After receiving no response from the boost-users list that could solve this problem I read the Reporting Bug document on the boost website. I followed the CVS instructions and checked out a copy from the HEAD (reported as boost-1.35) and built it. I used the following flags: bjam -sHAVE_ICU=1 -d2 -sTOOLS=gcc -sBUILD=release -sEXPAT_INCLUDE=/usr/include -sEXPAT_LIBPATH=/usr/lib stage Afterwards I installed it and rebuilt the test program. It is still failing inside the topological_sort. The output of the program is below along with the test program source code. Stephen --------- OUTPUT ------------ [storri@localhost infrastructure]$ ./test_dag Added edge: 1 -> 20 Number of edges is 1 Added edge: 1 -> 30 Number of edges is 2 Added edge: 1 -> 40 Number of edges is 3 Added edge: 1 -> 5 Number of edges is 4 Added edge: 20 -> 5 Number of edges is 5 Added edge: 30 -> 5 Number of edges is 6 Added edge: 40 -> 5 Number of edges is 7 /usr/lib/gcc/i386-redhat-linux/4.1.1/../../../../include/c ++/4.1.1/debug/safe_iterator.h:277: error: attempt to advance a dereferenceable (start-of-sequence) iterator 20 steps, which falls outside its valid range. Objects involved in the operation: iterator @ 0x0xbfead0fc { type = N11__gnu_debug14_Safe_iteratorIN9__gnu_cxx17__normal_iteratorIPN5boost18default_color_typeEN10__gnu_norm6vectorIS4_SaIS4_EEEEEN15__gnu_debug_def6vectorIS4_S8_EEEE (mutable iterator); state = dereferenceable (start-of-sequence); references sequence with type `N15__gnu_debug_def6vectorIN5boost18default_color_typeESaIS2_EEE' @ 0x0xbfead0fc } Aborted ----------- CODE --------------- #include <boost/graph/adjacency_list.hpp> #include <boost/shared_ptr.hpp> #include <boost/cstdint.hpp> #include <boost/format.hpp> #include <boost/graph/topological_sort.hpp> #include <iostream> #include <map> class Component; class Graph_Base { public: typedef boost::property< boost::vertex_index_t, boost::uint32_t, boost::property< boost::vertex_name_t, boost::shared_ptr<Component> > > VertexProperty_t; typedef boost::adjacency_list< boost::setS, // OutEdgeList boost::setS, // VertexList boost::directedS, // Directed VertexProperty_t > // VertexProperties Graph_t; typedef boost::adj_list_vertex_property_map<Graph_Base::Graph_t, boost::shared_ptr<Component>, const boost::shared_ptr<Component>&, boost::vertex_name_t> Property_Map_const_t; }; class Component { public: typedef boost::shared_ptr<Component> ptr_t; Component ( boost::uint32_t id ) : m_id ( id ) {} ~Component () { m_source_list.clear(); } // Now part of Component_Data void set_Data_Source ( uint32_t id ) { if ( ! m_source_list.insert ( std::make_pair ( id, false ) ).second ) { std::cerr << "WARNING: Attempted to add a duplicate component id."; std::cerr << std::endl; std::cerr << "Ignoring component id." << std::endl; } } std::map<boost::uint32_t, bool>::const_iterator get_Source_List_Begin() const { return m_source_list.begin(); } std::map<boost::uint32_t, bool>::const_iterator get_Source_List_End() const { return m_source_list.end(); } boost::uint32_t get_ID (void) const { return m_id; } private: boost::uint32_t m_id; std::map<boost::uint32_t, bool> m_source_list; }; class Component_Graph { public: typedef boost::graph_traits<Graph_Base::Graph_t>::vertex_descriptor Vertex_t; typedef boost::graph_traits<Graph_Base::Graph_t>::edge_descriptor Edge_t; typedef std::map<uint32_t, Vertex_t> IdVertexMap_t; Component_Graph () {} void add_Component ( Component::ptr_t obj_ptr ) { bool no_duplicate; IdVertexMap_t::iterator pos; Vertex_t node; if ( obj_ptr.get() == 0 ) { std::cerr << boost::format("Exception throw in %s at line %d") % __FILE__ % __LINE__ << std::endl; return; } boost::tie (pos, no_duplicate) = m_index.insert (std::make_pair(obj_ptr->get_ID(), node)); if ( no_duplicate ) { // Insertion was successful // Make a new vertex and return handle to 'node' node = add_vertex(m_graph); // Get list of Components boost::property_map<Graph_Base::Graph_t, boost::vertex_name_t>::type clist = boost::get(boost::vertex_name, m_graph); // Assign component to vertex position clist[node] = obj_ptr; // Add vertex handle to map position pos->second = node; // Get list of indexes boost::property_map<Graph_Base::Graph_t, boost::vertex_index_t>::type ilist = get(boost::vertex_index, m_graph); ilist[node] = obj_ptr->get_ID(); for ( std::map<boost::uint32_t,bool>::const_iterator cpos = obj_ptr->get_Source_List_Begin(); cpos != obj_ptr->get_Source_List_End(); ++cpos ) { this->add_Child ( (*cpos).first, obj_ptr ); } } else { std::cerr << "ERROR: Duplicate source found. Skipping Component" << std::endl; return; } } void add_Child ( uint32_t parent_id, Component::ptr_t obj_ptr ) { IdVertexMap_t::iterator pos; IdVertexMap_t::iterator cpos; if ( obj_ptr.get() == 0 ) { std::cerr << boost::format("Exception throw in %s at line %d") % __FILE__ % __LINE__ << std::endl; return; } pos = m_index.find (parent_id); cpos = m_index.find ( obj_ptr->get_ID() ); if (pos == m_index.end()) { std::cerr << "ERROR: Cannot find parent. Skipping adding component #" << obj_ptr->get_ID() << std::endl; return; } // Add edge from parent to child Edge_t link; if (! (add_edge ( pos->second, cpos->second, m_graph).second)) { std::cerr << "ERROR: Duplicate edge exists from " << parent_id << " to " << obj_ptr->get_ID() << std::endl; } else { std::cout << boost::format("Added edge: %d -> %d") % parent_id % obj_ptr->get_ID() << std::endl; std::cout << "Number of edges is " << num_edges ( m_graph ) << std::endl; } } Graph_Base::Graph_t const& get_Graph () const { return m_graph; } Component::ptr_t get_Component (const Vertex_t& node) const { Graph_Base::Property_Map_const_t clist = get(boost::vertex_name, m_graph); return clist[node]; } private: Graph_Base::Graph_t m_graph; IdVertexMap_t m_index; }; int main (int, char**) { // CREATE Component_Graph Component_Graph m_graph; // Create Components Component::ptr_t node_one ( new Component ( 1 ) ); Component::ptr_t node_twenty ( new Component ( 20 ) ); node_twenty->set_Data_Source ( 1 ); Component::ptr_t node_thirty ( new Component ( 30 ) ); node_thirty->set_Data_Source ( 1 ); Component::ptr_t node_forty ( new Component ( 40 ) ); node_forty->set_Data_Source ( 1 ); Component::ptr_t node_five ( new Component ( 5 ) ); node_five->set_Data_Source ( 1 ); node_five->set_Data_Source ( 20 ); node_five->set_Data_Source ( 30 ); node_five->set_Data_Source ( 40 ); // Add Components to Graph m_graph.add_Component ( node_one ); m_graph.add_Component ( node_twenty ); m_graph.add_Component ( node_thirty ); m_graph.add_Component ( node_forty ); m_graph.add_Component ( node_five ); // Call topological_sort on graph typedef std::vector<Component_Graph::Vertex_t> m_container; m_container comp_list; boost::topological_sort ( m_graph.get_Graph(), std::back_inserter ( comp_list ) ); std::cout << "A topological ordering: "; for ( m_container::reverse_iterator ii = comp_list.rbegin(); ii != comp_list.rend(); ++ii ) { Component::ptr_t comp_ptr = m_graph.get_Component ( *ii ); std::cout << comp_ptr->get_ID() << " "; } std::cout << std::endl; return 0; }

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