March 2012 - Boost-users - lists.preview.boost.org

[Property Map] given a function/functor, how to construct readable property map?
by Frank Birbacher 22 Mar '12

22 Mar '12

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi! I have graph structure using custom datatypes. An edge weight can be calculated by calling some function. I want to call the dag shortest path algorithm and pass it a property map that uses the function to compute edge weights on the fly. I consulted the Boost 1.47 documentation for property map. I find identity or std::map adaptors, but did not find any reference to using functions or functors. Do I miss anything? Frank -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.17 (Darwin) Comment: GPGTools - http://gpgtools.org Comment: keyserver x-hkp://pool.sks-keyservers.net iEYEARECAAYFAk9o2GwACgkQhAOUmAZhnmpdAwCfc38fjB2cZC/ZYzv7Y8+GXdTr IXgAnjoJh5ZKoxFkNTAK5Ye0DeOkuQY0 =8xTO -----END PGP SIGNATURE-----

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Boost ASIO cancelling jobs from another thread
by Mark Christiaens 21 Mar '12

21 Mar '12

We are developing a client-server application using Boost ASIO for asynchronous socket communication. We were wondering whether it is safe to cancel a read on a socket by closing the socket from another thread (without any additional synchronization)? What would be the preferred way to cancel operations from different threads? Thanks in advance, Mark Christiaens Amplidata

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boost::interprocess managed_unique_ptr cannot be used inside template (VS2008).
by bear330 21 Mar '12

21 Mar '12

Hi, I eagerly want to try boost 1.49, but the compiler error stuck me. managed_unique_ptr cannot be used inside template if I use Visual Studio 2008: There is a very simple example: #include <iostream> #include <boost/interprocess/managed_windows_shared_memory.hpp> #include <boost/interprocess/smart_ptr/unique_ptr.hpp> #include <boost/interprocess/allocators/allocator.hpp> #include <boost/interprocess/containers/list.hpp> #include <boost/interprocess/sync/named_mutex.hpp> #include <boost/interprocess/sync/named_condition.hpp> #include <boost/interprocess/sync/scoped_lock.hpp> struct Request { int a; }; template<typename Segment, typename T> class Channel { public: /// Value pointer in queue. typedef typename boost::interprocess::managed_unique_ptr<T, Segment>::type ValuePtr; }; int main(int argc, char* argv[]) { Channel<boost::interprocess::managed_windows_shared_memory, Request>::ValuePtr v; std::cout << "Test" << std::endl; return 0; } I got this error in Visual Studio 2008: T.cpp C:\Program Files\boost\boost_1_49_0\boost/interprocess/detail/pointer_type.hpp(64) : error C2039: 'remove_reference' : is not a member of 'boost::interprocess::ipcdetail::ipcdetail' C:\Program Files\boost\boost_1_49_0\boost/interprocess/smart_ptr/unique_ptr.hpp(94) : see reference to class template instantiation 'boost::interprocess::ipcdetail::pointer_type<T,D>' being compiled with [ T=Request, D=boost::interprocess::deleter<Request,boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>> ] T.cpp(34) : see reference to class template instantiation 'boost::interprocess::unique_ptr<T,D>' being compiled with [ T=Request, D=boost::interprocess::deleter<Request,boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>> ] C:\Program Files\boost\boost_1_49_0\boost/interprocess/detail/pointer_type.hpp(64) : error C2947: expecting '>' to terminate template-argument-list, found '<' C:\Program Files\boost\boost_1_49_0\boost/interprocess/detail/pointer_type.hpp(64) : error C3203: 'remove_reference' : unspecialized class template can't be used as a template argument for template parameter 'D', expected a real type C:\Program Files\boost\boost_1_49_0\boost/interprocess/detail/pointer_type.hpp(64) : error C2955: 'boost::interprocess::ipcdetail::remove_reference' : use of class template requires template argument list C:\Program Files\boost\boost_1_49_0\boost/interprocess/detail/type_traits.hpp(30) : see declaration of 'boost::interprocess::ipcdetail::remove_reference' C:\Program Files\boost\boost_1_49_0\boost/interprocess/detail/pointer_type.hpp(64) : error C2143: syntax error : missing ';' before '>' C:\Program Files\boost\boost_1_49_0\boost/interprocess/detail/pointer_type.hpp(64) : error C2039: 'type' : is not a member of '`global namespace'' C:\Program Files\boost\boost_1_49_0\boost/interprocess/detail/pointer_type.hpp(64) : error C2039: 'type' : is not a member of '`global namespace'' C:\Program Files\boost\boost_1_49_0\boost/interprocess/detail/pointer_type.hpp(64) : error C2238: unexpected token(s) preceding ';' C:\Program Files\boost\boost_1_49_0\boost/interprocess/smart_ptr/unique_ptr.hpp(94) : error C2039: 'type' : is not a member of 'boost::interprocess::ipcdetail::pointer_type<T,D>' ................ This example works fine in boost 1.48.0 I submit a ticket ( https://svn.boost.org/trac/boost/ticket/6648 #6648 ) to boost::interprocess, but no any reply since 3 weeks ago, So I just ask how to solve this problem or any direction? Thanks. -- View this message in context: http://boost.2283326.n4.nabble.com/boost-interprocess-managed-unique-ptr-ca… Sent from the Boost - Users mailing list archive at Nabble.com.

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Metric_TSP_approx example
by Jeff Wang 20 Mar '12

20 Mar '12

Hello, I am looking at metric_tsp_approx.cpp example file to test the TSP issue. My vertex points: 0(0.68,2.72),1(1.69,1.13),2(2.78,2.29),3(1.02,2.47),4(0.83,0.71),5(2.59,0.52) The metric_tsp_approx_tour give the result: 0,3,1,2,4,5,0. I think 0,3,1,2,5,4,0 is better than the previous result, am I wrong? Also, I do not want to have the result like connecting vertex 2 and 4, so I added a larger edge_weight value, say 1000.0 between 2 and 4, but the result is the same as that of genneral vertext distance weight, how could I make the tsp tour does not go from 2 to 4? Thanks, Jeff

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[Boost::Python] ensuring destructors are called when executing scripts
by Andy Falanga (afalanga) 20 Mar '12

20 Mar '12

Hi everyone, I'm working on an API that will be used in Python. I'm running some of my teams unit tests to test some new functionality. (These use the Python unit test framework though I admit I don't understand it.) The exposed class has an "interface" among its many member fields. This abstract class is, I believe, correctly defined. That is, the abstract class defines a virtual destructor. The derived classes define non-virtual destructors. When I use a smaller test python script that doesn't use the unit test framework for Python, all of these destructors seem to be called correctly. However, when using the unit test framework, this doesn't seem to be the case. I believe this to be problem anyway because when I use the unit test scripts, I get a BSOD. (The BSOD is because these classes use a propriety driver that was written by our team for underlying hardware.) When I call this class directly, in my other script, the destructors are called properly because things work and there's no BSOD. I found a posting to some python support group where someone was having a similar problem. They mentioned that using Py_Finalize seemed to fix this but that it shouldn't be used with Boost. I'd like to know what's going on first of all. I'm not a python "anything". Before now, I've never used the language. Is there some way to ensure that C++ destructors are called? One of the respondents to the thread I mentioned said something about the interpreter still hold references and using a clear() method. However, the code he/she provided to illustrate wasn't python code at all but C++. It was as if they didn't understand the OP's request. Any help is greatly appreciated. Andy

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boost link error
by Pervez, Salman 20 Mar '12

20 Mar '12

Hi everyone, I need some help debugging a link error I am getting. I am trying to compile an application that uses boost, here is the error. g++ -g -O2 -o .libs/sesame sesame-SysAgent.o sesame-Sysimage.o sesame-Package.o -L/home/spervez1/db-4.6.21/build_unix/lib -L/home/spervez1/boost_1_49_0/lib\ /home/spervez1/qpidc-0.14/src/.libs/libqmf.so /home/spervez1/qpidc-0.14/src/.libs/libqmfengine.so /home/spervez1/qpidc-0.14/src/.libs/libqpidclient.so /hom\ e/spervez1/qpidc-0.14/src/.libs/libqpidcommon.so -lboost_program_options -lboost_filesystem -ldl /home/spervez1/qpidc-0.14/src/.libs/libqpidtypes.so -luuid \ /home/spervez1/dbus-1.4.16/dbus/.libs/libdbus-1.so -lpthread -lrt -Wl,--rpath -Wl,/home/spervez1/qpid-tools/lib -Wl,--rpath -Wl,/home/spervez1/dbus-1.4.16/\ lib /usr/bin/ld: warning: libboost_system.so.1.49.0, needed by /home/spervez1/boost_1_49_0/lib/libboost_filesystem.so, not found (try using -rpath or -rpath-link) /home/spervez1/qpidc-0.14/src/.libs/libqpidcommon.so: undefined reference to `boost::system::system_category()' /home/spervez1/qpidc-0.14/src/.libs/libqpidcommon.so: undefined reference to `boost::system::generic_category()' collect2: ld returned 1 exit status I have boost installed in /home/spervez1/boost_1_49_0/ Here are the two commands that led to this error CPPFLAGS="-I/home/spervez1/db-4.6.21/build_unix/include -I/home/spervez1/boost_1_49_0/include" LDFLAGS="-L/home/spervez1/db-4.6.21/build_unix/lib -L/home/spervez1/boost_1_49_0/lib" ./configure --with-qpid-checkout=/home/spervez1/qpidc-0.14 --with-db4-devel=/home/spervez1/db-4.6.21/build_unix --with-boost=/home/spervez1/boost_1_49_0/ make I've researched some online and others have been able to solve this problem by adding the -lboost_filesystem flag which already exists in the makefile command so I'm a bit confused what the error could be. I'll appreciate any input on this. Thanks. Salman ________________________________ CONFIDENTIALITY AND SECURITY NOTICE The contents of this message and any attachments may be confidential and proprietary and also may be covered by the Electronic Communications Privacy Act. This message is not intended to be used by, and should not be relied upon in any way, by any third party. If you are not an intended recipient, please inform the sender of the transmission error and delete this message immediately without reading, disseminating, distributing or copying the contents. Citadel makes no assurances that this e-mail and any attachments are free of viruses and other harmful code.

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some simple questions on Date/Time parsing and formatting
by John M. Dlugosz 20 Mar '12

20 Mar '12

The Boost function ptime from_iso_string seems to only take part of a ISO 8601 date string. In particular, strings coming from XML will have a trailing Z. Even knowing that we will always get 'Z' and not some arbitrary timezone information, it seems a kludge to truncate the last character from the string before feeding it to a function that claims to parse an ISO date/time string. Am I missing something? Second, is there a simple function to format a ptime using the conventions of the current Locale? I see functions for "simple" and "iso", but user-facing output (as opposed to creating an XML file) needs to use local conventions. Thanks, —John

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[Graph] Example: astar_search_no_init over an infinite, implicit graph
by Luke Meyers 20 Mar '12

20 Mar '12

Having finally gotten this working, I wanted to share it. As the topic states, this is an implementation of an infinite, implicit graph, and an example that searches the graph with astar_search_no_init. I didn't find any examples out there of anyone doing this particular thing, so I hope it may be helpful to my fellow travelers. This code is a bastardization of some stuff from a game I'm working on (blatant plug: http://snarglequest.blogspot.com/) and the "city search" example code from the BGL docs. I'm sure it could be more concise, but I hope you'll find it accessible. Oh, and critiques would of course be welcome. I said it's working, not perfect; I'm sure there are many things I could be doing in better ways, and I'd love to know about them. Luke /** * Example use of boost::astar_search_no_init on an infinite, implicitly-defined graph. * * The graph type used here is XYGraph, representing an infinite grid of squares. Each * square is connected to its eight neighbors; however, the example shows how to use * boost::filtered_graph to make the search take place only along orthogonal edges. */ #include <iostream> #include <list> #include <map> #include <set> #include <utility> #include <boost/graph/graph_traits.hpp> #include <boost/graph/astar_search.hpp> #include <boost/graph/filtered_graph.hpp> #include <boost/operators.hpp> #include <boost/ref.hpp> namespace Direction { enum id { MIN = 0, N = MIN, S, E, W, NW, NE, SE, SW, NONE }; } struct XY : public boost::additive<XY, boost::totally_ordered<XY, boost::equivalent<XY> > > { typedef int X; typedef int Y; XY(X x = 0, Y y = 0); // Same square counts. bool adjacentTo(XY const& that) const; XY & operator=(XY const& that); XY & operator+=(XY const& that); bool operator<(XY const& that) const; X x; Y y; XY neighbor(Direction::id direction) const; std::set<XY> allNeighbors() const; }; std::ostream & operator<<(std::ostream & os, XY const& xy); struct neighbor_iterator; /* * Model of: * * Graph * * IncidenceGraph */ struct XYGraph { XYGraph(); // Graph concept requirements typedef XY vertex_descriptor; typedef std::pair<XY, XY> edge_descriptor; typedef boost::undirected_tag directed_category; typedef boost::disallow_parallel_edge_tag edge_parallel_category; typedef boost::incidence_graph_tag traversal_category; // IncidenceGraph concept requirements typedef neighbor_iterator out_edge_iterator; typedef int degree_size_type; }; namespace boost { template <> struct graph_traits<XYGraph> { typedef XYGraph G; typedef G::vertex_descriptor vertex_descriptor; typedef G::edge_descriptor edge_descriptor; typedef G::out_edge_iterator out_edge_iterator; typedef G::directed_category directed_category; typedef G::edge_parallel_category edge_parallel_category; typedef G::traversal_category traversal_category; typedef G::degree_size_type degree_size_type; typedef void in_edge_iterator; typedef void vertex_iterator; typedef void vertices_size_type; typedef void edge_iterator; typedef void edges_size_type; }; } // IncidenceGraph concept requirements std::pair<XYGraph::out_edge_iterator, XYGraph::out_edge_iterator> out_edges(XYGraph::vertex_descriptor v, XYGraph const& g); XYGraph::degree_size_type out_degree(XYGraph::vertex_descriptor v, XYGraph const& g); XYGraph::vertex_descriptor source(XYGraph::edge_descriptor e, XYGraph const& g); XYGraph::vertex_descriptor target(XYGraph::edge_descriptor e, XYGraph const& g); // Iterator struct neighbor_iterator : public boost::iterator_facade<neighbor_iterator, std::pair<XY,XY>, boost::forward_traversal_tag, std::pair<XY,XY> > { public: neighbor_iterator(); neighbor_iterator(XY xy, Direction::id direction); neighbor_iterator & operator=(neighbor_iterator const& that); std::pair<XY,XY> operator*() const; void operator++(); bool operator==(neighbor_iterator const& that) const; bool equal(neighbor_iterator const& that) const { return operator==(that); } void increment() { operator++(); } private: XY xy; Direction::id direction; }; struct orthogonal_only; template <typename Graph> class distance_heuristic; struct found_goal {}; // exception for termination // visitor that terminates when we find the goal class astar_goal_visitor : public boost::default_astar_visitor { public: astar_goal_visitor(XY goal) : m_goal(goal) {} virtual void examine_vertex(XY xy, XYGraph const& g) { std::cout << "Exploring " << xy << "..." << std::endl; if(xy == m_goal) throw found_goal(); } virtual void examine_vertex(XY xy, boost::filtered_graph<XYGraph, orthogonal_only> const& g) { std::cout << "Exploring " << xy << "..." << std::endl; if(xy == m_goal) throw found_goal(); } private: XY m_goal; }; template <typename K, typename V> class default_map { public: typedef K key_type; typedef V data_type; typedef std::pair<K,V> value_type; default_map(V const& defaultValue) : defaultValue(defaultValue) {} V & operator[](K const& k) { if (m.find(k) == m.end()) { m[k] = defaultValue; } return m[k]; } private: std::map<K,V> m; V const defaultValue; }; struct PredecessorMap { PredecessorMap() {} PredecessorMap(PredecessorMap const& that) : m(that.m) {} typedef XY key_type; typedef XY value_type; typedef XY & reference_type; typedef boost::read_write_property_map_tag category; XY & operator[](XY xy) { return m[xy]; } std::map<XY,XY> m; }; XY get(PredecessorMap const& pm, XY xy) { std::map<XY,XY>::const_iterator found = pm.m.find(xy); return (found != pm.m.end()) ? found->second : xy; } void put(PredecessorMap & pm, XY key, XY value) { pm.m[key] = value; } // Filter used to traverse grid only along orthogonal (non-diagonal) edges. struct orthogonal_only { typedef std::pair<XY,XY> Edge; bool operator()(Edge const& edge) const { return edge.first.x == edge.second.x || edge.first.y == edge.second.y; } }; // Euclidean distance heuristic (square root omitted) template <typename Graph> class distance_heuristic : public boost::astar_heuristic<Graph, int> { public: distance_heuristic(XY goal) : m_goal(goal) {} unsigned operator()(XY xy) { int dx = m_goal.x - xy.x; int dy = m_goal.y - xy.y; unsigned retval = static_cast<unsigned>(dx * dx + dy * dy); return retval; } private: XY m_goal; }; int main(int argc, char **argv) { XYGraph baseGraph; boost::filtered_graph<XYGraph, orthogonal_only> g(baseGraph, orthogonal_only()); //BOOST_CONCEPT_ASSERT((IncidenceGraphConcept< boost::filtered_graph<XYGraph, orthogonal_only> >)); XY start(0,0); XY goal(5,7); std::cout << "Start vertex: " << start << std::endl; std::cout << "Goal vertex: " << goal << std::endl; PredecessorMap p; typedef boost::associative_property_map< default_map<XY,unsigned> > DistanceMap; typedef default_map<XY,unsigned> WrappedDistanceMap; WrappedDistanceMap wrappedMap = WrappedDistanceMap(std::numeric_limits<unsigned>::max()); wrappedMap[start] = 0; DistanceMap d = DistanceMap(wrappedMap); try { astar_search_no_init(g, start, distance_heuristic<XYGraph>(goal) , visitor(astar_goal_visitor(goal)) . distance_map(d) . predecessor_map(boost::ref(p)) . weight_map(boost::associative_property_map< default_map<std::pair<XY,XY>,unsigned> >( default_map<std::pair<XY,XY>,unsigned>(1))) . vertex_index_map(boost::associative_property_map< std::map<XY,unsigned> >(std::map<XY,unsigned>())) . rank_map(boost::associative_property_map< std::map<XY,unsigned> >(std::map<XY,unsigned>())) . color_map(boost::associative_property_map< std::map<XY,boost::default_color_type> >( std::map<XY,boost::default_color_type>())) . distance_compare(std::less<unsigned>()) . distance_combine(std::plus<unsigned>()) ); } catch(found_goal const&) { // found a path to the goal std::list<XY> shortest_path; for(XY xy = goal;; xy = p[xy]) { shortest_path.push_front(xy); if(p[xy] == xy) break; } std::cout << "Shortest path from " << start << " to " << goal << ": "; std::list<XY>::iterator spi = shortest_path.begin(); std::cout << start; for(++spi; spi != shortest_path.end(); ++spi) std::cout << " -> " << (*spi); std::cout << std::endl; return 0; } std::cout << "Didn't find a path from " << start << "to" << goal << "!" << std::endl; return 0; } XYGraph::XYGraph() {} std::pair<XYGraph::out_edge_iterator, XYGraph::out_edge_iterator> out_edges(XYGraph::vertex_descriptor v, XYGraph const& g) { return std::make_pair( XYGraph::out_edge_iterator(v, Direction::MIN), XYGraph::out_edge_iterator(v, Direction::NONE) ); } XYGraph::degree_size_type out_degree(XYGraph::vertex_descriptor v, XYGraph const& g) { return v.allNeighbors().size(); } XYGraph::vertex_descriptor source(XYGraph::edge_descriptor e, XYGraph const& g) { return e.first; } XYGraph::vertex_descriptor target( XYGraph::edge_descriptor e, XYGraph const& g) { return e.second; } neighbor_iterator::neighbor_iterator() {} neighbor_iterator::neighbor_iterator(XY xy, Direction::id direction) : xy(xy) , direction(direction) { } neighbor_iterator & neighbor_iterator::operator=(neighbor_iterator const& that) { xy = that.xy; direction = that.direction; return *this; } std::pair<XY,XY> neighbor_iterator::operator*() const { std::pair<XY,XY> const retval = std::make_pair(xy, xy.neighbor(direction)); return retval; } void neighbor_iterator::operator++() { direction = static_cast<Direction::id>(int(direction) + 1); } bool neighbor_iterator::operator==(neighbor_iterator const& that) const { return xy == that.xy && direction == that.direction; } XY::XY(X x, Y y) : x(x) , y(y) { } bool XY::adjacentTo(XY const& that) const { return abs(x - that.x) <= 1 && abs(y - that.y) <= 1; } XY & XY::operator=(XY const& that) { x = that.x; y = that.y; return *this; } XY & XY::operator+=(XY const& that) { x += that.x; y += that.y; return *this; } bool XY::operator<(XY const& that) const { return x < that.x || (x == that.x && y < that.y); } std::ostream & operator<<(std::ostream & os, XY const& xy) { os << "(" << xy.x << "," << xy.y << ")"; return os; } XY XY::neighbor(Direction::id direction) const { using namespace Direction; int dx = 0, dy = 0; switch (direction) { case NW: case W: case SW: dx = -1; break; case NE: case E: case SE: dx = 1; } switch (direction) { case NW: case N: case NE: dy = -1; break; case SW: case S: case SE: dy = 1; } XY const neighbor(x + dx, y + dy); return neighbor; } std::set<XY> XY::allNeighbors() const { std::set<XY> neighbors; for (int dx = -1; dx <= 1; ++dx) for (int dy = -1; dy <= 1; ++dy) neighbors.insert(XY(x+dx,y+dy)); return neighbors; }

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Tokenizer - multiple separators
by asif saeed 20 Mar '12

20 Mar '12

Hi, Can I pass multiple separators (for example ";|") in a char_sep to Boost::Tokenizer? Can I then use boost is_any_of to tokenize of any of these separator characters? Can you give me an example? Does Boost::Tokenizer already do this? Thanks in advance. Best regards, Asif

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[XML] validate closing tags with boost property tree read_xml?
by Simon Coakley 20 Mar '12

20 Mar '12

boost::property_tree::xml_parser::read_xml uses the default rapidxml behaviour of not validating closing tags. With rapidxml you can use the flag parse_validate_closing_tags to turn this on. Boost does not support any such flag. Is there anyway to turn it on using Boost or will I have to use rapidxml directly? Thanks

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