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

Re: [Boost-users] Collecting boost multi-index meta data
by Joaquin M Lopez Munoz 25 Mar '11

25 Mar '11

Gokulakannan Somasundaram <gokul007 <at> gmail.com> writes: > > > Hi, > Say i have a boost::tuple / MPL Sequence, on which i have > created a multi-index. Is it possible for me collect all the > attribute numbers on which i have declared the > IndexSpecifierList( the one passed as template parameter to > boost::multi_index::indexed_by ) ? Hi Gokul, I'm not sure I undersand your question. Have you taken a look at the index_type_list nested type? http://www.boost.org/libs/multi_index/doc/reference/multi_index_container.h… types >From this MPL sequence you can easily extract the list of key extractor types used for defining the multi_index_container, which hopefully is close to what you're after. Don't hesitate to elaborate a little more on your question and I'll see whether I can be more helpful. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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[BGL] Separating twin vertices
by Shaun Jackman 19 Mar '11

19 Mar '11

Hi, I have a directed graph where every vertex has a twin vertex. It is known ahead of time which pairs of vertices are twins. I want to remove as few vertices as possible from the graph such that no vertex and its twin is in the same connected component. Could someone suggest an appropriate algorithm? I've just started delving into the BGL. So far I'm suitably impressed! Cheers, Shaun

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[Filesystem] v3 using wide url with boost::iostreams::mapped_file
by Bibbo, Joe 10 Mar '11

10 Mar '11

We recently flipped the switch from v2 to v3 of the boost file system. Now that boost:filesystem::wpath is no longer a valid type, how do you work with the wide url and boost:iostreams::mapped_file? With v2 we would void doSomethingWithMapfile(std::wstring& url) { boost::iostreams::basic_mapped_file_params<boost::filesystem::wpath> attribs; // initialize attribs, including attribs.path = url; // create our mapped file boost::iostreams::mapped_file mapFile(attribs); // An then do something with the map file. } Regards, Joe

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[iostreams] restriction device/filter
by Borko Jandras 09 Mar '11

09 Mar '11

Hello, I'm looking at the implementation of the "restriction" device, from Boost.Iostreams library, which provides access to a subsequence of the original device. When it reaches the end of the input subsequence, the restriction device start performing read()'s of size zero on the original device. Shouldn't it be returning an end-of-sequence marker (EOF) instead? I am using a restriction device as source parameter for the iostreams::copy function and this always results in an infinite loop. Am I doing something wrong? Thanks! - Borko

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[graph] Is reverse_graph<> read-only?
by al.zatv 08 Mar '11

08 Mar '11

Hello! Is reverse_graph<> in Boost::Graph Library, read-only? I just can't beleive it:) Can it be fixed?

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[ptr_container] compiler error with BOOST_RESULT_OF_USE_DECLTYPE
by Nathan Ridge 07 Mar '11

07 Mar '11

Hello, The following code: #include <boost/ptr_container/ptr_set.hpp> struct A { bool operator<(const A&) const; }; int main() { boost::ptr_set<A> s; return 0; } gives the following compiler errors when compiling with BOOST_RESULT_OF_USE_DECLTYPE defined: In file included from ../../lib/boost- 1.45/boost/preprocessor/iteration/detail/iter/forward1.hpp:52:0, from ../../lib/boost-1.45/boost/utility/result_of.hpp:92, from ../../lib/boost-1.45/boost/ptr_container/indirect_fun.hpp:23, from ../../lib/boost-1.45/boost/ptr_container/ptr_set.hpp:19, from test.cpp:1: ../../lib/boost-1.45/boost/utility/detail/result_of_iterate.hpp: In instantiation of 'boost::detail::cpp0x_result_of_impl<less<A>(A &)>': ../../lib/boost-1.45/boost/utility/detail/result_of_iterate.hpp:44:8: instantiated from 'boost::result_of<less<A>(A &)>' ../../lib/boost-1.45/boost/ptr_container/indirect_fun.hpp:107:9: instantiated from 'boost::void_ptr_indirect_fun<less<A>, A, A>' stl_tree.h:462:31: instantiated from '_Rb_tree< void *, void *, _Identity<void *> , boost::void_ptr_indirect_fun<less<A>, A, A> >' stl_set.h:112:17: instantiated from 'set< void *, boost::void_ptr_indirect_fun<less<A>, A, A> >' ../../lib/boost-1.45/boost/ptr_container/ptr_set_adapter.hpp:40:21: instantiated from 'boost::ptr_container_detail::set_config< A, set<void *, boost::void_ptr_indirect_fun<less<A>, A, A> >, true >' ../../lib/boost-1.45/boost/ptr_container/detail/reversible_ptr_container.hpp:87:59: instantiated from 'boost::ptr_container_detail::reversible_ptr_container< boost::ptr_container_detail::set_config< A, set<void *, boost::void_ptr_indirect_fun<less<A>, A, A> >, true >, boost::heap_clone_allocator >' ../../lib/boost-1.45/boost/ptr_container/detail/associative_ptr_container.hpp:32:11: instantiated from 'boost::ptr_container_detail::associative_ptr_container< boost::ptr_container_detail::set_config< A, set<void *, boost::void_ptr_indirect_fun<less<A>, A, A> >, true >, boost::heap_clone_allocator >' ../../lib/boost-1.45/boost/ptr_container/ptr_set_adapter.hpp:122:11: instantiated from 'boost::ptr_container_detail::ptr_set_adapter_base< A, set<void *, boost::void_ptr_indirect_fun<less<A>, A, A> > , boost::heap_clone_allocator, true >' ../../lib/boost-1.45/boost/ptr_container/ptr_set_adapter.hpp:299:11: instantiated from 'boost::ptr_set_adapter< A, set<void *, boost::void_ptr_indirect_fun<less<A>, A, A> > , boost::heap_clone_allocator, true >' ../../lib/boost-1.45/boost/ptr_container/ptr_set.hpp:33:11: instantiated from 'boost::ptr_set<A>' ../shared/test/test.cpp:10:23: instantiated from here ../../lib/boost-1.45/boost/utility/detail/result_of_iterate.hpp:70:69: error: no match for call to '(less<A>) (A &)' stl_function.h:230:12: candidate is: stl_function.h:233:7: bool less<A>::operator()(const A &, const A &) const stl_function.h:233:7: candidate expects 2 arguments, 1 provided I am compiling with g++ 4.5 with the --std=c++0x flag. The error goes away if I do not define BOOST_RESULT_OF_USE_DECLTYPE (but I need this define for other things). Am I doing something wrong or is this a bug? Thanks, Nate.

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Boost Concepts with iterators and ranges
by Robert Ramey 04 Mar '11

04 Mar '11

I've been experimenting with Boost Concepts in conjunction with Boost Range and by implication boost iterators. I have a few questions from the documentation: a) I see BOOST_CONCEPT_USAGE described in some detail in the section Creating Concept Checking Classes. But in the section titled "Reference" I only find in the subsection "macros" BOOST_CONCEPT_ASSERT and BOOST_CONCEPT_REQUIRES. Is BOOST_CONCEPT_USAGE meant to be used? b) "Deprecated Concept Checking Classes" "For each of the concepts documented here, the library includes an identical concept checking class whose name ends in "Concept" For example, in addition to RandomAccessIterator, the library defines a RandomAccessIteratorConcept class template." It sounds like this means that I shouldn't expect to find "WritableIteratorConcept" but in fact in "interator_concepts.hpp" find just that. I'm assuming that's an oversight. c) except for the above, the Range library uses things like ForwardTraversal and ForwardTraversalConcept the iterators library uses ForwardTraversal only. d) the iterators concepts are in the root namespace boost_concepts while the range concepts are in the root namespace boost. e) boost/range/concepts.hpp includes the file boost/iterator/iterator_concepts.hpp All this makes it very hard to keep all this straight in one's head. Is there any possibility that all this could be made simpler to follow by some combination of documentation improvements and/or namespace coordination? Robert Ramey

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Re: [Boost-users] [GIL] gray pixel iterator in generic algorithm
by Robert Lupton the Good 02 Mar '11

02 Mar '11

> With this, the unit test for my gray opening function with an unscaled float image now compiles and works fine. Does this mean that you have some clean way to handle gil images that don't automatically scale into [0,1]? If so, can we have it pushed into the next boost release? I have a clunky version of this that I'm not proud of, but I certainly need. I'm an astronomer, and the values in my images (unsigned short, int, float) are directly related to the number of photons detected so scaling is a real problem. R

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[python] intercepting uncaught exceptions
by Gennadiy Rozental 01 Mar '11

01 Mar '11

Hi, I am using Boost.Python quite extensively (even stretching it to the limit in some cases). Now I cave this problem: Is there any way to intercept uncaught exception in embedded Python code? I need to add some information to an exception/traceback in this case. I have full control over environment before embedded code is executed. I thought I'll be able to use sys.excepthook, but it does not seem to be invoked. Alternatively I'd can live if I can somehow retrieve the context of failed call (global/local dict?) in boost::python::error_already_set handler. Please advise, Gennadiy

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boost::asio from C++ Forms App in VS 2010
by Alan Vella 01 Mar '11

01 Mar '11

Hi all, I'm trying to port a C++ project from gcc (on MinGW) to Visual Studio 2010 inside a Visual C++ Windows Forms application. The code was originally written on a Windows XP 32-bit machine. Now it is being ported into a Windows 7 32-bit machine. This project uses quite a few boost libraries, including the boost::asio library. When I try to compile the code in VS2010 I get the following errors: 1> Please define _WIN32_WINNT or _WIN32_WINDOWS appropriately. For example: 1> - add -D_WIN32_WINNT=0x0501 to the compiler command line; or 1> - add _WIN32_WINNT=0x0501 to your project's Preprocessor Definitions. 1> Assuming _WIN32_WINNT=0x0501 (i.e. Windows XP target). 1>C:\Program Files\boost\boost_1_44\boost/asio/detail/impl/win_thread.ipp(52): error C2664: 'QueueUserAPC' : cannot convert parameter 1 from 'void (__stdcall *)(ULONG_PTR)' to 'PAPCFUNC' 1> Address of a function yields __clrcall calling convention in /clr:pure and /clr:safe; consider using __clrcall in target type 1>C:\Program Files\boost\boost_1_44\boost/asio/detail/impl/win_thread.ipp(82): error C2664: '_beginthreadex' : cannot convert parameter 3 from 'unsigned int (__stdcall *)(void *)' to 'unsigned int (__stdcall *)(void *)' 1> Address of a function yields __clrcall calling convention in /clr:pure and /clr:safe; consider using __clrcall in target type 1>C:\Program Files\boost\boost_1_44\boost/asio/detail/win_thread.hpp(31): error C3641: 'boost::asio::detail::win_thread_function' : invalid calling convention '__stdcall ' for function compiled with /clr:pure or /clr:safe 1>C:\Program Files\boost\boost_1_44\boost/asio/detail/win_thread.hpp(36): error C3641: 'boost::asio::detail::apc_function' : invalid calling convention '__stdcall ' for function compiled with /clr:pure or /clr:safe 1>C:\Program Files\boost\boost_1_44\boost/asio/detail/win_fenced_block.hpp(35): error C3862: 'boost::asio::detail::win_fenced_block::win_fenced_block': cannot compile an unmanaged function with /clr:pure or /clr:safe 1> Inline native assembly not supported in managed code 1>C:\Program Files\boost\boost_1_44\boost/asio/detail/win_fenced_block.hpp(35): error C3645: 'boost::asio::detail::win_fenced_block::win_fenced_block' : __clrcall cannot be used on functions compiled to native code 1>C:\Program Files\boost\boost_1_44\boost/asio/detail/win_fenced_block.hpp(54): error C3862: 'boost::asio::detail::win_fenced_block::~win_fenced_block': cannot compile an unmanaged function with /clr:pure or /clr:safe 1> Inline native assembly not supported in managed code 1>C:\Program Files\boost\boost_1_44\boost/asio/detail/win_fenced_block.hpp(54): error C3645: 'boost::asio::detail::win_fenced_block::~win_fenced_block' : __clrcall cannot be used on functions compiled to native code 1> 1>Build FAILED. Any help would be much appreciated. Cheers, Alan Vella. _______________________________________________________ Unlimited Disk, Data Transfer, PHP/MySQL Domain Hosting http://www.doteasy.com

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