- Boost-users - lists.boost.org

[iterator] unrelated type problem with iterator_facade arrow operator
by Michael Fawcett 23 Mar '09

23 Mar '09

Can someone confirm if the attached code doesn't compile intentionally or if this is a bug? I'm sorry for not posting a minimal example but I couldn't figure out how to reduce the problem. It requires Windows (uses ATL::CAdapt and ATL::CComBSTR) and I've tested using VS 2005 and VS2008. This bug manifests when the Reference type has overloaded the address-of operator to return a type not implicitly convertible to Value * (I believe). Changing lines 324-326 in iterator_facade.hpp from: static type make(Reference x) { return implicit_cast<type>(&x); } to: static type make(Reference x) { return implicit_cast<type>(boost::addressof(x)); } and adding the appropriate include makes the attached code compile. Full error log below: 1>c:\dev\vendor\boost\1.37.0\boost\iterator\iterator_facade.hpp(326) : error C2664: 'boost::implicit_cast' : cannot convert parameter 1 from 'BSTR *' to 'ATL::CComBSTR *' 1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast 1> c:\dev\vendor\boost\1.37.0\boost\iterator\iterator_facade.hpp(325) : while compiling class template member function 'ATL::CComBSTR *boost::detail::operator_arrow_result<ValueType,Reference,Pointer>::make(Reference)' 1> with 1> [ 1> ValueType=ATL::CComBSTR, 1> Reference=ATL::CComBSTR &, 1> Pointer=ATL::CComBSTR * 1> ] 1> c:\dev\vendor\boost\1.37.0\boost\iterator\iterator_facade.hpp(641) : see reference to class template instantiation 'boost::detail::operator_arrow_result<ValueType,Reference,Pointer>' being compiled 1> with 1> [ 1> ValueType=ATL::CComBSTR, 1> Reference=ATL::CComBSTR &, 1> Pointer=ATL::CComBSTR * 1> ] 1> c:\dev\vendor\boost\1.37.0\boost\iterator\iterator_adaptor.hpp(271) : see reference to class template instantiation 'boost::iterator_facade<Derived,Value,CategoryOrTraversal,Reference,Difference>' being compiled 1> with 1> [ 1> Derived=test::atl::CAdapt_iterator<std::_Vector_iterator<ATL::CAdapt<ATL::CComBSTR>,std::allocator<ATL::CAdapt<ATL::CComBSTR>>>>, 1> Value=ATL::CComBSTR, 1> CategoryOrTraversal=std::random_access_iterator_tag, 1> Reference=ATL::CComBSTR &, 1> Difference=__w64 int 1> ] 1> c:\dev\personal\boost\iterator_adaptor_bug\main.cpp(65) : see reference to class template instantiation 'boost::iterator_adaptor<Derived,Base,Value,Traversal,Reference>' being compiled 1> with 1> [ 1> Derived=test::atl::CAdapt_iterator<std::_Vector_iterator<ATL::CAdapt<ATL::CComBSTR>,std::allocator<ATL::CAdapt<ATL::CComBSTR>>>>, 1> Base=std::_Vector_iterator<ATL::CAdapt<ATL::CComBSTR>,std::allocator<ATL::CAdapt<ATL::CComBSTR>>>, 1> Value=ATL::CComBSTR, 1> Traversal=std::random_access_iterator_tag, 1> Reference=ATL::CComBSTR & 1> ] 1> c:\dev\personal\boost\iterator_adaptor_bug\main.cpp(103) : see reference to class template instantiation 'test::atl::CAdapt_iterator<Iterator>' being compiled 1> with 1> [ 1> Iterator=std::_Vector_iterator<ATL::CAdapt<ATL::CComBSTR>,std::allocator<ATL::CAdapt<ATL::CComBSTR>>> 1> ] Thanks for any insight, --Michael Fawcett

1 1

Re: [Boost-users] Dijkstra shortest path
by Florian.PONROY＠fr.thalesgroup.com 23 Mar '09

23 Mar '09

Hi, The following algorithm should do the trick: // predecessors is the predecessor map // destinationNode is the node you want to reach // sourceNode is the source of the graph int currentNode = destinationNode; int predecessorNode = 0; std::cerr << boost::format("--- PATH: %d <- ") % destinationNode; do { predecessorNode = predecessors[currentNode]; if (predecessorNode == currentNode) { // Unreachable nextHop = 0; std::cerr << "XXX" << std::endl; break; } else if (predecessorNode == sourceNode) { // Next hop found nextHop = currentNode; std::cerr << sourceNode << std::endl; break; } else { // One hop on the path currentNode = predecessorNode; std::cerr << boost::format("%d <- ") % currentNode; } } while (true); Hope it helps, Florian -----Message d'origine----- De : boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org]De la part de dwaem Envoyé : lundi 23 mars 2009 16:23 À : boost-users(a)lists.boost.org Objet : Re: [Boost-users] Dijkstra shortest path Steven Watanabe-4 wrote: > > AMDG > > dwaem wrote: >> int weight[] = {1, 1, 2, 2, 3, 4, 3, 4, 5, 6, 7}; >> >> <snip> >> >> it shows >> distances and parents: >> distance(A) = 0, parent(A) = C >> distance(B) = 0, parent(B) = A >> distance(C) = 0, parent(C) = C >> distance(D) = 0, parent(D) = C >> distance(E) = 0, parent(E) = C >> >> >> which makes no sense. >> > > You're not using the weight array anywhere, > so you get the default weight of 0 for every edge. > > In Christ, > Steven Watanabe > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users > > Yes this is my obviouse oversight. But now when I have founded shortest path from node A to node B. How to display full path from A to B, not only parent of the last node. -- View this message in context: http://www.nabble.com/Dijkstra-shortest-path-tp22626827p22662345.html Sent from the Boost - Users mailing list archive at Nabble.com. _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

1 0

Dijkstra shortest path
by dwaem 23 Mar '09

23 Mar '09

Hi I made a little change to example from manual which search shortest path http://www.boost.org/doc/libs/1_37_0/libs/graph/example/dijkstra-example.cpp http://www.boost.org/doc/libs/1_37_0/libs/graph/example/dijkstra-example.cpp by adding add_edge function but is seams to give incorect results #include <boost/config.hpp> #include <algorithm> #include <vector> #include <utility> #include <iostream> #include <boost/graph/adjacency_list.hpp> #include <boost/graph/reverse_graph.hpp> #include <boost/graph/graph_utility.hpp> #include <boost/graph/dijkstra_shortest_paths.hpp> #include <boost/graph/graph_traits.hpp> #include <boost/graph/adjacency_list.hpp> using namespace boost; int main() { typedef adjacency_list < vecS, vecS, bidirectionalS, no_property, property < edge_weight_t, int > > graph; typedef graph_traits < graph >::vertex_descriptor vertex_descriptor; typedef graph_traits < graph >::edge_descriptor edge_descriptor; graph G(5); enum nodes { A, B, C, D, E }; add_edge(A, E, G); add_edge(B, E, G); add_edge(C, E, G); add_edge(A, B, G); add_edge(B, D, G); add_edge(B, A, G); add_edge(B, C, G); add_edge(C, A, G); add_edge(C, D, G); add_edge(D, A, G); add_edge(D, B, G); int weight[] = {1, 1, 2, 2, 3, 4, 3, 4, 5, 6, 7}; char name[] = "ABCDE"; std::cout << "\n"; vertex_descriptor s = vertex(C, G); property_map<graph, edge_weight_t>::type weightmap = get(edge_weight, G); std::vector<vertex_descriptor> p(num_vertices(G)); std::vector<int> d(num_vertices(G)); dijkstra_shortest_paths(G, s, predecessor_map(&p[0]).distance_map(&d[0])); std::cout << "distances and parents:" << std::endl; graph_traits < graph >::vertex_iterator vi, vend; for (tie(vi, vend) = vertices(G); vi != vend; ++vi){ std::cout << "distance(" << name[*vi] << ") = " << d[*vi] << ", "; std::cout << "parent(" << name[*vi] << ") = " << name[p[*vi]] << std::endl; } std::cout << std::endl; } it shows distances and parents: distance(A) = 0, parent(A) = C distance(B) = 0, parent(B) = A distance(C) = 0, parent(C) = C distance(D) = 0, parent(D) = C distance(E) = 0, parent(E) = C which makes no sense. Marcin Matuszak -- View this message in context: http://www.nabble.com/Dijkstra-shortest-path-tp22626827p22626827.html Sent from the Boost - Users mailing list archive at Nabble.com.

2 2

[lambda]How can I call function of objects in std::list while using std::for_each?
by 钱晓明 23 Mar '09

23 Mar '09

Please help me! I want to call a virtual function of objects in std::list while using std::for_each: struct DiscardableItem { void Discard() { std::cout<<"Discard item!"<<std::endl; } }; std::list<DiscardableItem*> items; items.push_back(new DiscardableItem); items.push_back(new DiscardableItem); std::for_each( items.rbegin(), items.rend(), _1->*&DiscardableItem::Discard ); But DiscardableItem::Discard does not be called. How can I make it work? thanks! I think lambda can solve this problem easily.

4 5

[utility] addressof issue with classes having templated conversion operators
by Gevorg Voskanyan 23 Mar '09

23 Mar '09

Hi folks, I've came across a problem with addressof() when the argument is of a class type with a template conversion operator. A minimal test case reproducing the issue is attached. Using boost 1.38, the example fails to compile under gcc 4.2.2, with the following error: ../../../../vendor/boost/boost_1_38_0/boost/utility/addressof.hpp: In function 'T* boost::addressof(T&) [with T = convertible]': addressof_conversion.cpp:17: instantiated from here boost/boost_1_38_0/boost/utility/addressof.hpp:42: error: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second: ../../../../vendor/boost/boost_1_38_0/boost/utility/addressof.hpp:26: note: candidate 1: static T* boost::detail::addressof_impl<T>::f(T&, long int) [with T = convertible] ../../../../vendor/boost/boost_1_38_0/boost/utility/addressof.hpp:32: note: candidate 2: static T* boost::detail::addressof_impl<T>::f(T*, int) [with T = convertible] AFAICT gcc is right complaining here, according to 13.3.3 The same example compiles OK with boost 1.33.1, and the changeset that causes the difference seems to be this one: https://svn.boost.org/trac/boost/changeset/44705 Can this be considered a regression? How should this issue be addressed? Thanks, Gevorg

2 4

Suggestion about using Signals2
by Daniele Barzotti 23 Mar '09

23 Mar '09

Hi, I need some help on using signals2 in my app, I hope to explain my problem well. I have a thread that reads from the RS232: void SerialPort::reading() { ... read... if (data_available) signal_OnData; } the signal_OnData is: typedef boost::signals2::signal<void ()> _signal_void; _signal_void signal_OnData; And I connect it to a method MyUserClass::OnDataReceived() Into this method (MyUserClass::OnDataReceived) I need to re-send some data to RS232, but the SerialPort::reading thread is locked because it's waiting the OnDataReceived ends.. In fact, when the methods OnDataReceived ends, I receive data again. How can I solve this problem? Thanks in advance! Daniele.

2 11

Re: [Boost-users] [Graph] Computing reachable vertices on a graph
by Florian.PONROY＠fr.thalesgroup.com 23 Mar '09

23 Mar '09

Hi Andrew, Thank you very much for your reply. I eventually implemented Steven Watanabe's solution, which seems easier to me. Since I only need to know which nodes are actually reachable, I may get rid of distances for now. Thanks again, Florian -----Message d'origine----- De : boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org]De la part de Andrew Sutton Envoyé : vendredi 20 mars 2009 18:35 À : boost-users(a)lists.boost.org Objet : Re: [Boost-users] [Graph] Computing reachable vertices on a graph However, I encounter the following issue : in this example, vertices are numbered from 0 to 5. However, in my project, this is not the case, vertices could be numbered 5, 38, 42, 384... Using a vector in that case might not work as expected, a map<vertex, distance> would probably be better. I'm not quite familiar with BGL so far, maybe should I deal with a specific property map? Or using a visitor to record a vertex distance upon graph discovery? I'm a little bit lost, any help will be greatly appreciated! You probably shouldn't rely on vertex indices as the canonical id of the vertex. The method of identifying vertices (and edges) in an adjacency list varies with the vertex set and edge set type selectors (indices or identifeirs for vecS aren't the same as listS). There are a couple of different approaches. The easiest would be to simply maintain a mapping of id to vertex descriptor. For example: map<int, graph_traits<Graph>::vertex_descriptor> verts; verts[5] = add_vertex(g); verts[58] = add_vertex(g); // and so on. You can couple that bundled vertex properties to get a kind of bimap. struct vertex_props { int id; } typedef adj_list<vecS, vecS, directedS, vertex_props> Graph; template <typename Graph, typename Map> void add_vertex(Graph& g, Map& verts, int id) { vertex_descriptor v = add_vertex(g); verts[id] = v; g[v].id = id; } add_vertex(g, verts, 5); add_vertex(g, verts, 58); ... cout << g[*vertices(g).begin]->id << "\n"; Hope that helps, Andrew Sutton andrew.n.sutton(a)gmail.com <mailto:andrew.n.sutton@gmail.com>

1 0

Re: [Boost-users] [Graph] Computing reachable vertices on a graph
by Florian.PONROY＠fr.thalesgroup.com 23 Mar '09

23 Mar '09

Hi Steven, I just tried your solution, which works perfectly well. The vector is actually sized to the number of reachable nodes. I just added a reachable.reserve(max_number_of_nodes) to avoid multiple reallocations. Thank you very much for your help, Florian -----Message d'origine----- De : boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org]De la part de Steven Watanabe Envoyé : vendredi 20 mars 2009 18:36 À : boost-users(a)lists.boost.org Objet : Re: [Boost-users] [Graph] Computing reachable vertices on a graph AMDG Florian.PONROY(a)fr.thalesgroup.com wrote: > I need to get the list of all reachable vertices from a given vertex in a graph. I'm currently using the BFS algorithm to achieve that, which seems to fit well to my need. > How does this work: #include <boost/graph/adjacency_list.hpp> #include <boost/graph/breadth_first_search.hpp> #include <boost/graph/visitors.hpp> #include <vector> #include <iterator> typedef boost::adjacency_list< boost::vecS, boost::vecS, boost::directedS > Graph; int main() { Graph G(1); boost::add_edge(0, 1, G); boost::add_edge(1, 2, G); boost::add_edge(2, 5, G); boost::add_edge(3, 2, G); boost::add_edge(4, 3, G); boost::add_edge(5, 3, G); typedef Graph::vertex_descriptor Vertex; std::vector<Vertex> reachable; // The source vertex Vertex s = *(boost::vertices(G).first); boost::breadth_first_search(G, s, boost::visitor( boost::make_bfs_visitor( boost::write_property( boost::identity_property_map(), std::back_inserter(reachable), boost::on_discover_vertex())))); } In Christ, Steven Watanabe _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

1 0

trouble with correct type definition of multi_index::nth_index
by Sandeep Gupta 23 Mar '09

23 Mar '09

Hi, In the following code I am trying to get an handle to the index of a multi_index container. The compiler says "invalid initialization of reference of type ‘boost::multi_index::detail:..". Not sure why this is so. Since I wasn't sure about the source of error I have pasted the full code ( sans declarations) is give below. Thanks sandeep ///-------------------------Full code --------------------- template<typename Col1_t, typename Col2_t, typename Col3_t, typename Col4_t> class TupleStore { typedef tuple<Col1_t, Col2_t, Col3_t, Col4_t> tuple_t; typedef multi_index_container < tuple_t, indexed_by < ordered_unique<tuple_member_extractor<tuple_t,0> > > > tuplestore_t; tuplestore_t m_tuplestore; public: template<int n> void lookup_key(Col1_t key) const { typedef typename tuplestore_t:: template nth_index<n>::type tuplestore_index_t; ///compiler error here tuplestore_index_t& indexx = m_tuplestore.get<n>(); } }; int main() { TupleStore<int,int,int,int> tstr; tstr.lookup_key<0>(5); }

2 1

phoenix for_each and std::cout
by Sandeep Gupta 23 Mar '09

23 Mar '09

Hi, I am trying to use phoenix::for_each to print each element of iterator range. Would appreciate if any clarification as to why statements 1 and 2 are giving compile errors. Thanks sandeep //-------------code snippet int x; counting_iterator<int> first(0), last(10); iterator_range<counting_iterator<int> > ir(first, last); phoenix::for_each(ir, std::cout<<x<<' ')(); //stmt 1 ; compile error phoenix::for_each(ir, std::cout<<arg1<<' ')(); //stmt 2; compile error

2 1