January 2011 - Boost-users - lists.preview.boost.org

Improving extern template usage
by Jens Auer 04 Jan '11

04 Jan '11

Hi, I've been playing around with the extern template implementation of Visual C++ (2005 and 2010) to reduce our overly long build times. Microsoft's implementation does only omit implicit definitions for member functions not defined inline in the class body. This makes the feature rather useless to reduce build times, as most functions in the boost library (and Microsoft's STL) seem to be declared inline and get implicitly instantiated every time, thus forcing the linker to remove them which is quite costly. This behavior is also perfectly valid with the standard where an exception is made for member functions of template classes defined inline. Would it be reasonable to change the coding guidelines to only define trivial member functions in the class body and provide the definitions separatly after the class declaration? I think gcc does implicitly sinatntiate these member functions, but the MS compilers are widely used and a large number of users would benefit.

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enable_if: fusion seq, vs2010 vs gcc
by Hicham Mouline 04 Jan '11

04 Jan '11

#include <iostream> #include <boost/utility/enable_if.hpp> #include <boost/fusion/include/is_sequence.hpp> struct S { double skid; }; template<typename Archive> void serialize(Archive& ar, S& sp, unsigned int) { std::cout<<"1st one"<<std::endl; } template <typename Archive, typename Seq> typename boost::enable_if_c<boost::fusion::traits::is_sequence<Seq>::value, void>::type serialize( Archive& ar, Seq& seq, unsigned int) { std::cout<<"2nd one"<<std::endl; } template void serialize<double>(double&, S&, unsigned int); int main() { S s; double d1=5.; serialize(d1, s, 5); return 0; } The above code compiles ok on gcc4.5.1 and prints 1st one. It crashes vs2008. vs2010 was fixed not to crash but fails to compile according to those who have vs2010. Is this correct code (I guess I mean standard conforming)? regards,

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[units] subtract_typeof_helper<> help!
by Terry Golubiewski 04 Jan '11

04 Jan '11

I'm trying to use boost::geometry and boost::units together. For some reason boost::geometry doesn't represent the difference of two points as vectors. So, I'm making my own Vector class and defining Vector = Point - Point. The sample program below doesn't compile because I need to tell the units library about the special properties of point subtraction (I think). terry #include <boost/geometry/geometry.hpp> #include <boost/units/systems/si.hpp> #include <boost/units/quantity.hpp> #include <boost/units/io.hpp> #include <iostream> #include <iomanip> using namespace std; using namespace boost; using namespace boost::geometry; using namespace boost::units; typedef point<double, 3, cs::cartesian> Point; class Vector { Point _impl; friend Vector operator-(const Point& lhs, const Point& rhs); explicit Vector(Point p) : _impl(p) { } public: Vector() : _impl(0) { } Vector(double dx, double dy, double dz=0) : _impl(dx, dy, dz) { } friend ostream& operator<<(ostream& os, const Vector& v) { return os << dsv(v._impl); } }; // Vector inline Vector operator-(const Point& lhs, const Point& rhs) { Point tmp(lhs); subtract_point(tmp, rhs); return Vector(tmp); } inline ostream& operator<<(ostream& os, const Point& pt) { return os << dsv(pt); } int main() { Point p1(1, 2, 3); Point p2(4, 5, 6); typedef quantity<si::length, Point> Position; typedef quantity<si::length, Vector> Displacement; Position start( p1 * si::meters); Position finish(p2 * si::meters); Displacement disp(finish - start); cout << "disp=" << disp << endl; return EXIT_SUCCESS; } // main

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[Proto] EvalStream Revisited -- Segmentation Fault
by Hossein Haeri 04 Jan '11

04 Jan '11

Dear all, A few weeks ago, I asked for help about an EDSL which can handle expressions like x >> f >> g >> h so that they're equivalent to h(g(f(x))) once evaluated. Eric kindly provided me with the solution in the P.S. I was just playing around with his code and thought about extending it with a simple case when f's and g's are actually functions, as opposed to function objects. So, I added the following two lines: int plus1(int i) {return i + 1;} const terminal<pointer_to_unary_function<int, int> >::type plus_one = {ptr_fun(&plus1)}; And, I get a segmentation fault (GCC 4.5.1, MinGW32, WinXP, SP3) when I run the following line: 1 >> plus_one >> plus_one Any ideas? TIA, --Hossein P.S. #include <boost/proto/proto.hpp> #include <iostream> namespace proto = boost::proto; using proto::_; struct add_one_ { typedef int result_type; int operator()(int i) const { return i + 1; } }; proto::terminal<add_one_>::type const add_one = {}; struct GetFun : proto::call<proto::_value(proto::_right)> {}; struct EvalStream : proto::or_< proto::when< proto::terminal<_> , proto::_value > , proto::when< proto::shift_right<EvalStream, proto::terminal<_> > , proto::lazy< GetFun(EvalStream(proto::_left)) > > > {}; int main() { // This prints "3" std::cout << EvalStream()( 1 >> add_one >> add_one ) << std::endl; }

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[units] Automatic Physical Units in Mathematica and Boost.Units
by alfC 03 Jan '11

03 Jan '11

Since there are not many computer software that handles units seriously, except possibly for Boost.Units and Mathematica`Units in my opinion, I just wanted to point out to this post: Automatic Physical Units in Mathematica http://blog.wolfram.com/2010/12/09/automatic-physical-units-in-mathematica/ Interesting discussion in terms of features. One of the reasons I hated Mathematica units handling so far was due to the lack of a typing system which C++ and boost.Units have naturally, the other reason was that the physical quantites didn't seem to play well with other parts of the system. Now it seems that Mathematica Units is discovering "types". One of the features that it mentions is the ability to perform automatic conversions upon arithmetic operations of mixed units. In fact I was working in a way to perform automatic conversion in Boost.Units inside arithmetic formulas, since Mathematica has unbounded precision arithmetic by default the automatic conversions are not a real problem. An exact matching of this feature can not be achieved with a limited precision representation (like double). I'll take the opportunity ask two broad general questions: Does any body have experience with using boost.units quantity with a underlying type that are not double, e.g. multiple precision, or vector (geometric) objects? Does it work well? Are there future planned developments for Boost.Units, in terms of external features (e.g. automatic conversion, better interaction with boost.phoenix) or internal implementation? Thank you, Alfredo

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mpi/serialization: string serialization and const char*
by Hicham Mouline 02 Jan '11

02 Jan '11

hello, Including I mpi::broadcast an object. Its serialization method is split into a save() and a load(). In the save(), I send: ar << "fixed_params"; where ar is a boost::mpi::packed_iarchive. At reception, the load() function : std::string paramstype; ar >> paramstype; if (paramstype=="fixed_params") /// this fails because the count of characters if 12 for 1 side and 13 for the other. The null character is there. Should this work? regards,

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[Proto] Vector Example Compilation Failure
by Hossein Haeri 02 Jan '11

02 Jan '11

Dear all, Trying the Vector example at the Proto documentation: http://boost.org/doc/libs/1_45_0/doc/html/proto/users_guide.html#boost_prot… under Boost 1.42 and GCC 4.5.1 (MinGW32, WinXP, SP3), I get the error message in the PS. Any ideas why this is happening? How would I solve the problem? (BTW, I have already tried the Boost 1.42 version of this example as well.) TIA,--Hossein -------------- Build: Debug in Vector --------------- Compiling: main.cpp In file included from d:\program files\codeblocks\mingw\bin\../lib/gcc/mingw32/4.5.1/include/c++/vector:65:0, from D:\My Documents\My Programmes\Tutorial\Proto\Examples\Vector\main.cpp:10: d:\program files\codeblocks\mingw\bin\../lib/gcc/mingw32/4.5.1/include/c++/bits/stl_vector.h: In instantiation of 'std::_Vector_base<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_>': d:\program files\codeblocks\mingw\bin\../lib/gcc/mingw32/4.5.1/include/c++/bits/stl_vector.h:171:5: instantiated from 'std::vector<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_>' D:\Sources\Boost\boost_1_42_0/boost/mpl/aux_/preprocessed/gcc/template_arity.hpp:85:5: instantiated from 'const int boost::mpl::aux::template_arity_impl<std::vector<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_>, 1>::value' D:\Sources\Boost\boost_1_42_0/boost/mpl/aux_/preprocessed/gcc/template_arity.hpp:93:5: instantiated from 'const int boost::mpl::aux::template_arity<std::vector<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_> >::value' D:\Sources\Boost\boost_1_42_0/boost/mpl/aux_/preprocessed/gcc/template_arity.hpp:98:30: instantiated from 'boost::mpl::aux::template_arity<std::vector<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_> >' D:\Sources\Boost\boost_1_42_0/boost/proto/matches.hpp:247:13: instantiated from 'boost::proto::detail::terminal_matches<const std::vector<int>&, std::vector<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_> >' D:\Sources\Boost\boost_1_42_0/boost/proto/matches.hpp:322:13: [ skipping 7 instantiation contexts ] D:\Sources\Boost\boost_1_42_0/boost/proto/matches.hpp:505:13: instantiated from 'boost::proto::result_of::matches<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::multiplies, boost::proto::argsns_::list2<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> >, VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> > >, 2l> >, VectorGrammar>' D:\Sources\Boost\boost_1_42_0/boost/mpl/aux_/nested_type_wknd.hpp:28:1: instantiated from 'boost::mpl::aux::nested_type_wknd<boost::proto::result_of::matches<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::multiplies, boost::proto::argsns_::list2<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> >, VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> > >, 2l> >, VectorGrammar> >' D:\Sources\Boost\boost_1_42_0/boost/mpl/aux_/preprocessed/gcc/and.hpp:29:1: instantiated from 'boost::mpl::aux::and_impl<true, boost::proto::result_of::matches<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::multiplies, boost::proto::argsns_::list2<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> >, VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> > >, 2l> >, VectorGrammar>, mpl_::bool_<true>, mpl_::bool_<true>, mpl_::bool_<true> >' D:\Sources\Boost\boost_1_42_0/boost/mpl/aux_/preprocessed/gcc/and.hpp:55:1: instantiated from 'boost::mpl::and_<mpl_::bool_<true>, boost::proto::result_of::matches<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::multiplies, boost::proto::argsns_::list2<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> >, VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> > >, 2l> >, VectorGrammar>, mpl_::bool_<true>, mpl_::bool_<true>, mpl_::bool_<true> >' D:\Sources\Boost\boost_1_42_0/boost/proto/operators.hpp:219:9: instantiated from 'boost::proto::detail::enable_binary<VectorDomain, IsVector<std::vector<int> >, std::vector<int>, IsVector<std::vector<int> >, std::vector<int>, VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::multiplies, boost::proto::argsns_::list2<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> >, VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> > >, 2l> > >' D:\My Documents\My Programmes\Tutorial\Proto\Examples\Vector\main.cpp:223:34: instantiated from here d:\program files\codeblocks\mingw\bin\../lib/gcc/mingw32/4.5.1/include/c++/bits/stl_vector.h:71:60: error: no class template named 'rebind' in 'struct boost::proto::wildcardns_::_' d:\program files\codeblocks\mingw\bin\../lib/gcc/mingw32/4.5.1/include/c++/bits/stl_vector.h: In instantiation of 'std::vector<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_>': D:\Sources\Boost\boost_1_42_0/boost/mpl/aux_/preprocessed/gcc/template_arity.hpp:85:5: instantiated from 'const int boost::mpl::aux::template_arity_impl<std::vector<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_>, 1>::value' D:\Sources\Boost\boost_1_42_0/boost/mpl/aux_/preprocessed/gcc/template_arity.hpp:93:5: instantiated from 'const int boost::mpl::aux::template_arity<std::vector<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_> >::value' D:\Sources\Boost\boost_1_42_0/boost/mpl/aux_/preprocessed/gcc/template_arity.hpp:98:30: instantiated from 'boost::mpl::aux::template_arity<std::vector<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_> >' D:\Sources\Boost\boost_1_42_0/boost/proto/matches.hpp:247:13: instantiated from 'boost::proto::detail::terminal_matches<const std::vector<int>&, std::vector<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_> >' D:\Sources\Boost\boost_1_42_0/boost/proto/matches.hpp:322:13: instantiated from 'boost::proto::detail::matches_<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l>, boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<std::vector<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_> >, 0l> >' D:\Sources\Boost\boost_1_42_0/boost/proto/matches.hpp:505:13: [ skipping 6 instantiation contexts ] D:\Sources\Boost\boost_1_42_0/boost/proto/matches.hpp:505:13: instantiated from 'boost::proto::result_of::matches<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::multiplies, boost::proto::argsns_::list2<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> >, VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> > >, 2l> >, VectorGrammar>' D:\Sources\Boost\boost_1_42_0/boost/mpl/aux_/nested_type_wknd.hpp:28:1: instantiated from 'boost::mpl::aux::nested_type_wknd<boost::proto::result_of::matches<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::multiplies, boost::proto::argsns_::list2<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> >, VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> > >, 2l> >, VectorGrammar> >' D:\Sources\Boost\boost_1_42_0/boost/mpl/aux_/preprocessed/gcc/and.hpp:29:1: instantiated from 'boost::mpl::aux::and_impl<true, boost::proto::result_of::matches<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::multiplies, boost::proto::argsns_::list2<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> >, VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> > >, 2l> >, VectorGrammar>, mpl_::bool_<true>, mpl_::bool_<true>, mpl_::bool_<true> >' D:\Sources\Boost\boost_1_42_0/boost/mpl/aux_/preprocessed/gcc/and.hpp:55:1: instantiated from 'boost::mpl::and_<mpl_::bool_<true>, boost::proto::result_of::matches<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::multiplies, boost::proto::argsns_::list2<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> >, VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> > >, 2l> >, VectorGrammar>, mpl_::bool_<true>, mpl_::bool_<true>, mpl_::bool_<true> >' D:\Sources\Boost\boost_1_42_0/boost/proto/operators.hpp:219:9: instantiated from 'boost::proto::detail::enable_binary<VectorDomain, IsVector<std::vector<int> >, std::vector<int>, IsVector<std::vector<int> >, std::vector<int>, VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::multiplies, boost::proto::argsns_::list2<VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> >, VectorExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<const std::vector<int>&>, 0l> > >, 2l> > >' D:\My Documents\My Programmes\Tutorial\Proto\Examples\Vector\main.cpp:223:34: instantiated from here d:\program files\codeblocks\mingw\bin\../lib/gcc/mingw32/4.5.1/include/c++/bits/stl_vector.h:173:58: error: no type named 'value_type' in 'struct boost::proto::wildcardns_::_' d:\program files\codeblocks\mingw\bin\../lib/gcc/mingw32/4.5.1/include/c++/bits/stl_vector.h:196:20: error: no members matching 'std::vector<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_>::_Base::_M_allocate' in 'struct std::vector<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_>::_Base' d:\program files\codeblocks\mingw\bin\../lib/gcc/mingw32/4.5.1/include/c++/bits/stl_vector.h:197:20: error: no members matching 'std::vector<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_>::_Base::_M_deallocate' in 'struct std::vector<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_>::_Base' d:\program files\codeblocks\mingw\bin\../lib/gcc/mingw32/4.5.1/include/c++/bits/stl_vector.h:199:20: error: no members matching 'std::vector<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_>::_Base::_M_get_Tp_allocator' in 'struct std::vector<boost::proto::wildcardns_::_, boost::proto::wildcardns_::_>::_Base' Process terminated with status 1 (0 minutes, 2 seconds) 7 errors, 0 warnings

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[BGL] setS as an edge container
by Datalurkur 01 Jan '11

01 Jan '11

I'm attempting to set up pathfinding using Dijkstra's algorithm, and decided to use setS since I need to add/remove edges frequently and don't want to worry about adding parallel edges. My typedefs are such: typedef property<edge_weight_t, int> Weight; typedef adjacency_list<vecS, setS, undirectedS, no_property, Weight> Graph; typedef graph_traits<Graph>::vertex_descriptor VertexDescriptor; typedef graph_traits<Graph>::edge_descriptor EdgeDescriptor; However, when trying to actually call dijkstra_shortest_paths, like so: std::vector<VertexDescriptor> predecessorMap(num_vertices(*_graph)); std::vector<int> distanceMap(num_vertices(*_graph)); dijkstra_shortest_paths(*_graph, startVertex, predecessor_map(&predecessorMap[0]).distance_map(&distanceMap[0])); I wind up with a bunch of compile errors within boost. Some examples: .../Boost.framework/Headers/graph/dijkstra_shortest_paths.hpp:377: error: no matching function for call to 'put(int*&, void* const&, int&)' .../Boost.framework/Headers/graph/two_bit_color_map.hpp:77: error: invalid cast from type 'boost::detail::error_property_not_found' to type 'size_t' .../Boost.framework/Headers/graph/dijkstra_shortest_paths.hpp:139: error: no matching function for call to 'get(int*&, void*)' I suspect it has something to do with the index map, but I assumed that vertex mappings that used vecS didn't need to be supplied with an index map. I followed the dijkstra example as closely as possible, but since they have a static set of edges and use vecS to store the edge map, I'm pretty certain that's where the discrepancy lies. Any other examples, advice?

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[netlib] Preparing for 0.9 and 0.8.1 Release, Help Wanted; Readying for Boost Submission
by Dean Michael Berris 01 Jan '11

01 Jan '11

Hi Guys! (Apologies in advance for the cross-post) I've just pushed the master, 0.8-devel, and 0.9-devel branch onto the cpp-netlib repository -- please take the time to test all these branches as I work on getting the documentation up to speed on the 0.9-devel branch preparing for the release and submission for review on the Boost developers mailing list. I'm also welcoming contributions in the form of: * Website help, the current documentation look is OK, but if you have time to fix up some of the issues like the fonts, adding anchors and maybe reformatting the API pages so that it's easier indexed, that would be *sweet*. Also, we need a landing page on cpp-netlib.github.com which introduces the library, hosts stats, and maybe has other goodies that are specifically for a website and not necessarily for documentation. * Documentation -- please, if you have example use cases that you want to contribute, now is the time to contribute them. If you have real world use cases where you're actually using cpp-netlib, now would be a good time to have your use case highlighted in the documentation. * More string implementations -- currently I need help with supporting Qt strings, MS CString, and wide strings in the implementation of the HTTP Clients. Those who are using wide strings and unicode strings natively and who have more experience with them (I only ever deal with the "C" locale) would be most welcome to contribute to getting the HTTP client to either do conversions or natively support different string implementations. I can help with the integration part by introducing the extension points that may not be obvious from the design (as it is still largely undocumented). * Examples -- the current set of examples are a little trivial, and if you have some interesting examples you want to build on (or would like to implement some of the examples highlighted here: https://github.com/cpp-netlib/cpp-netlib/issues/labels/Examples) your contribution would be most welcome. There are some things that I've pushed out for later releases, as I would like to concentrate at the moment to making the HTTP implementations more robust and support a wider range of use-cases. I'm looking for people with experience with ESMTP 1.0 who would like to contribute to implementing a simple client implementation that we can build along the same design as the HTTP client implementation. There's already a MIME parser/generator library in cpp-netlib thanks to Marshall Clow (which he presented in BoostCon 2010) also being developed for inclusion into Boost -- hopefully we can get that baked into the ESMTP client implementation early on to make it more immediately useful. At any rate, please expect a slightly delayed release of 0.9 which would be the first release which defaults to non-header-only, while 0.8.1 will be the first patch update version for 0.8. Appropriate changelogs to follow as soon as the releases are ready. In the meantime, please feel free to test out the code already in GitHub: http://github.com/cpp-netlib/cpp-netlib/ -- the stabilization effort for 0.9 and 0.8.1 will happen on this repository. Feedback would be most appreciated. Thanks everyone! -- Dean Michael Berris about.me/deanberris

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boost asio tcp::socket assign
by Lloyd 01 Jan '11

01 Jan '11

Hi, I have a boost::asio::ip::tcp::socket variable (reference) in a class, and it is initialized at the object construction time. At a later time I need to assign a new socket to this "socket reference variable". I think boost::assign is meant for that. But when I use assign, get the following error... (or is there any other method available?) .....cannot convert parameter 2 from 'boost::asio::ip::tcp::socket' to 'const boost::asio::detail::win_iocp_socket_service<Protocol>::native_type &' The code snippet is as follows... class MyClass { .... ..... private: tcp::socket& Socket; } void MyClass::SetSocket(tcp::socket& s) { Socket.assign(boost::asio::ip::tcp::v4(),s); } What could be the reason? Thanks in advance, Lloyd

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