September 2014 - Boost-users

[Range] Strange!
by Robert Jones 10 Sep '14

10 Sep '14

Can anyone explain why my last output line is garbage? #include <iostream> #include <boost/range/algorithm/copy.hpp> #include <boost/range/counting_range.hpp> #include <boost/range/adaptor/reversed.hpp> #include <boost/range/adaptor/transformed.hpp> #include <boost/phoenix/bind/bind_function.hpp> #include <boost/phoenix/core/argument.hpp> int doubled( int i ) { return i * 2; } template <typename Range> void print_it( const Range & range ) { boost::copy( range, std::ostream_iterator<int>( std::cout, " " ) ); std::cout << std::endl; } int main( ) { using boost::adaptors::reversed; using boost::adaptors::transformed; using boost::counting_range; using boost::phoenix::arg_names::_1; print_it( counting_range( 1, 5 ) ); print_it( counting_range( 1, 5 ) | reversed ); print_it( counting_range( 1, 5 ) | transformed( doubled ) ); print_it( counting_range( 1, 5 ) | reversed | transformed( doubled ) ); print_it( counting_range( 1, 5 ) | transformed( bind( doubled, _1 ) ) ); print_it( counting_range( 1, 5 ) | reversed | transformed( bind( doubled, _1 ) ) ); } Output is 1 2 3 4 4 3 2 1 2 4 6 8 8 6 4 2 2 4 6 8 -711713824 -711713824 -711713824 -711713824 Compiling with gcc-4.9.1, Boost 1.56 on Fedora 20 64-bit. Thx, Rob.

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[filesystem] directory_iterator and filter in 1.56.0
by Braden McDaniel 10 Sep '14

10 Sep '14

This sort of thing worked in Boost 1.55.0: #include <boost/filesystem.hpp> #include <boost/range.hpp> #include <boost/range/adaptor/filtered.hpp> struct pred { bool operator()(const boost::filesystem::directory_entry & dirent) const { return true; } }; int main() { const auto dirent_range = boost::make_iterator_range(boost::filesystem::directory_iterator("/"), boost::filesystem::directory_iterator()); const auto filtered_dirent_range = boost::adaptors::filter(dirent_range, pred()); } Not so in 1.56.0 [output from Apple's clang 3.4]: boost/concept_check.hpp:210:9: error: no viable conversion from 'boost::single_pass_traversal_tag' to 'boost::forward_traversal_tag' Y y = x; ^ ~ The full error output is much more verbose and I can provide it if desired; but the above is the gist of the situation, as I understand it: directory_iterators are SinglePass iterators; filter operates on ForwardTraversal iterators; and the SinglePass iterator cannot be converted to the ForwardTraversal one. Is this situation deliberate or an unintended side effect? Is there some similarly succinct means of filtering a file/directory listing? -- Braden McDaniel <braden(a)endoframe.com>

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Re: [Boost-users] [context] Compiling error with context and bind
by José 10 Sep '14

10 Sep '14

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[context] Compiling error with context and bind
by José 09 Sep '14

09 Sep '14

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[msm] extending msm::back::state_machine
by Manuel Schiller 09 Sep '14

09 Sep '14

Hi, I tried to enhance the backend of boost::msm by inheriting from boost::msm::back::state_machine. When doing so, I cannot access members of my subclass in the states. When compiling the attached example, I get this error message: *error: ‘class boost::msm::back::state_machine<fsm_, boost::parameter::void_, boost::parameter::void_, boost::parameter::void_, boost::parameter::void_>’ has no member named ‘test’* How can I "inject" extended_back_machine as the type being passed as "FSM" to the state? Bye Manuel #################################### template<typename FrontMachine> struct extended_back_machine : public boost::msm::back::state_machine<FrontMachine> { void test() { std::cout << "test" << std::endl; } }; struct fsm_ : public boost::msm::front::state_machine_def<fsm_> { struct State : public boost::msm::front::state<> { template <class Event,class FSM> void on_entry(Event const&, FSM& fsm) { fsm.test(); } }; typedef State initial_state; }; int main() { typedef extended_back_machine<fsm_> fsm; fsm m; m.start(); return 0; } ####################################

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[boost][container][static_vector] Stack or heap?
by Aaron Levy 08 Sep '14

08 Sep '14

Does the boost::container::static_vector allocate its memory on the stack or heap. From what I could make of the code, it seems to allocate on the stack. What happens if the requested size exceeds the stack size limits? Aaron

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[boost][assign][bimap] Assign support for bimap
by Aaron Levy 08 Sep '14

08 Sep '14

Are there any Boost.Assign overloads available for Boost.Bimap? Aaron

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linking with Intel compiler to Boost libs compiled with Visual Studio
by Damien 05 Sep '14

05 Sep '14

Hi, I'm trying to link to Boost 1.56 libs that I built with VS2013. We compile with both Intel and VS. We build Boost with layout=tagged (e.g. boost_serialization-mt-gd.lib), and these link fine with VS2013. When linking with Intel 2015 the linker complains about a missing library, looking for the layout=versioned lib name (e.g. libboost_serialization-iw-mt-gd-1_56.lib). Even if you specify the library name directly on the link line, it still complains. I'm sure this is just an include or #define issue but I don't know where to look. If anyone can point me in the right direction I'd be grateful. Cheers, Damien

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Testers required
by Antony Polukhin 05 Sep '14

05 Sep '14

Hi, There is a big need in testers that have access to exotic platforms(zArch, MIPS) and compilers (Cray, IBM xlc ...). Could you please run `b2` in `boost/libs/type_index/test` and report results. This will help to test Boost.TypeIndex library and other libraries that depend on `demangle.hpp` I'll appreciate any help. Thanks in advance! -- Best regards, Antony Polukhin

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[graph] Vertex order and VertexList type changes boykov_kolmogorov_max_flow result
by Michael J Iatauro 04 Sep '14

04 Sep '14

In the code below, using listS to store vertices results in vertex instantiation order changing the amount of flow computed by boykov_kolmogorov_max_flow. As given, it computes a flow of 0. If I move the instantiation of "T-" to be before "t-" or switch the VertexList parameter of adjacency_list to vecS, it computes the correct flow of 1000. Stepping through the code, it looks like when the max_flow function iterates over vertices that are targets of out-edges from the source, the call to get(m_in_active_list_map, v) at boykov_kolmogorov_max_flow.hpp:528 returns true for the second vertex, preventing it from getting added to m_active_nodes. I tested this using g++ 4.4.7 and with Boost 1.55 and 1.56. Has anybody else seen anything like this? Code follows: #include <boost/graph/adjacency_list.hpp> #include <boost/graph/boykov_kolmogorov_max_flow.hpp> #include <boost/graph/properties.hpp> #include <boost/graph/graph_traits.hpp> #include <iostream> #include <limits> using namespace boost; typedef adjacency_list_traits<vecS, listS, directedS> Traits; typedef Traits::vertex_descriptor Vertex; typedef Traits::edge_descriptor Edge; typedef adjacency_list<vecS, listS, directedS, property<vertex_name_t, std::string, property<vertex_index_t, long, property<vertex_color_t, default_color_type, property<vertex_distance_t, long, property<vertex_predecessor_t, Edge > > > > >, property<edge_flow_t, double, property<edge_capacity_t, double, property<edge_residual_capacity_t, double, property<edge_reverse_t, Edge > > > > > Graph; void addEdge(Graph& g, const Vertex& source, const Vertex& target, const double capacity, const double reverseCapacity) { property_map<Graph, edge_reverse_t>::type rev = get(edge_reverse, g); Edge e1 = add_edge(source, target, g).first; Edge e2 = add_edge(target, source, g).first; put(edge_capacity, g, e1, capacity); put(edge_capacity, g, e2, reverseCapacity); rev[e1] = e2; rev[e2] = e1; } int main(void) { Graph g; property_map<Graph, vertex_name_t>::type nameMap = get(vertex_name, g); Vertex source = add_vertex(g); nameMap[source] = "source"; Vertex sink = add_vertex(g); nameMap[sink] = "sink"; Vertex tminus = add_vertex(g); nameMap[tminus] = "t-"; addEdge(g, source, tminus, 1, 0); Vertex Tminus = add_vertex(g); nameMap[Tminus] = "T-"; addEdge(g, source, Tminus, 1000, 0); Vertex Tplus = add_vertex(g); nameMap[Tplus] = "T+"; addEdge(g, Tplus, sink, 1000, 0); addEdge(g, Tplus, Tminus, 0, std::numeric_limits<int>::max()); double flow = boykov_kolmogorov_max_flow(g, source, sink); std::cout << flow << std::endl; return 0; } -- ------------------ Michael J. Iatauro Software Engineer QTS, Inc. NASA Ames Research Center Office: 650-604-0662 Mail stop: 269-2 P.O. Box 1 Moffett Field, CA 94035-0001

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