September 2007 - Boost-users

[bind] MSVC 8.0 compiles _1 but not _2
by Mark Ruzon 29 Sep '07

29 Sep '07

Suppose you want to compute 3 - x for a vector of floats: using namespace std; vector<float> v; transform(v.begin(), v.end(), v.begin(), boost::bind(minus<float>(), _1, 3.0f)); This compiles fine on the MSVC 8.0 compiler. But I want to compute x - 3, and replacing _1 with _2 in the above expression yields a mess of errors, starting with: c:\program files\boost\boost_1_34_1\boost\bind.hpp(278) : error C2679: binary '[' : no operator found which takes a right-hand operand of type 'overloaded-function' (or there is no acceptable conversion) c:\program files\boost\boost_1_34_1\boost\bind.hpp(205): could be 'float boost::_bi::list1<A1>::operator [](boost::arg<I>) const' with [ A1=float &, I=1 ] Anybody have any thoughts on this one? Thanks, Mark

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Boost test manual can not be accessed
by Peng Yu 28 Sep '07

28 Sep '07

Hi, The following webpage can not be accessed. Can somebody fix it. http://www.boost.org/libs/test/doc/components/utf/getting_started/index.html Thanks Peng

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dynamic_pointer_cast doesn't work as expected
by Diego Bernini 28 Sep '07

28 Sep '07

Hi, see these lines: boost::shared_ptr<Executor> executor(&(createExecutor(subclass,name))); if(!executor) { throw LoadingClassException("createExecutor function of\""+subclass+"\" return null."); } //executor points to an object of class ExecDebugger that IS A Executor //(it's a plugin loaded at run time via Qt) boost::shared_ptr<Nameable> a=executor; boost::shared_ptr<Executor> sp; sp=boost::dynamic_pointer_cast<Executor>(a); --------------------------------------------------------------------------------------------------------------------- a is a Nameable, it points to a ExecDebugger object. ExecDebugger IS A Executor, Executor IS A Nameable...but sp is always ==0! Why?! Thanks, Diego Bernini

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Re: [Boost-users] fast_pool_allocator won't compile with VS 2005 SP1 using map
by Scott 28 Sep '07

28 Sep '07

I'm sorry, but I failed to mention I'm using boost 1.33.1 Scott

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fast_pool_allocator won't compile with VS 2005 SP1 using map
by Scott 28 Sep '07

28 Sep '07

I have a std::map that I'd like to use the fast_pool_allocator with. But when I declare it, I get errors with rebind. typedef std::pair<IndexVariant, Hints> IndexMapType; typedef boost::fast_pool_allocator<IndexMapType> IndexPoolAllocator; typedef std::map<IndexVariant, Hints, std::less< IndexVariant >, IndexPoolAllocator> ValueHints; 1>C:\Program Files\Microsoft Visual Studio 8\VC\include\map(28) : error C2903: 'rebind' : symbol is neither a class template nor a function template 1> C:\Program Files\Microsoft Visual Studio 8\VC\include\xtree(26) : see reference to class template instantiation 'std::_Tmap_traits<_Kty,_Ty,_Pr,_Alloc,_Mfl>' being compiled 1> with 1> [ 1> _Kty=nw::IndexVariant, 1> _Ty=nw::Hints, 1> _Pr=std::less<nw::IndexVariant>, 1> _Alloc=nw::IndexPoolAllocator, 1> _Mfl=false 1> ] However, if I substitute: typedef std::allocator<IndexMapType> IndexPoolAllocator; it all compiles fine. I'd appreciate any help with my problem! :) Thanks, Scott

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boost::result_of and gcc
by Martin Ecker 28 Sep '07

28 Sep '07

Hello, I'm running into a problem when using boost::result_of with gcc 3.4.2 and 4.2.1 (with MingW). The following program compiles fine with Visual C++ 8.0, but not with gcc: ------------------------------- #include <boost/utility/result_of.hpp> struct test_function1 { template <typename SignatureT> struct result; template <typename T> struct result<test_function1 (T)> { typedef T type; }; template <typename T> T operator () (T t) const { return t; } }; template <typename ArgT> struct test_function2 { template <typename SignatureT> struct result; template <typename T> struct result<test_function2 (T)> { typedef T type; }; template <typename T> T operator () (T t) const { return t; } }; int main(int argc, char *argv[]) { typedef boost::result_of< test_function1(int)>::type result_type; typedef boost::result_of< test_function2<float>(int)>::type result_type; return 0; } ------------------------------- The error message I get is for the second typedef using test_function2: E:/Projects/Third Party/boost/boost/utility/result_of.hpp: In instantiation of `boost::detail::result_of_nested_result<test_function2<float>, test_function2<float> ()(int)>': E:/Projects/Third Party/boost/boost/utility/result_of.hpp:75: instantiated from `boost::detail::result_of_impl<test_function2<float>, test_function2<float> ()(int), false>' E:/Projects/Third Party/boost/boost/utility/detail/result_of_iterate.hpp:24: instantiated from `boost::result_of<test_function2<float> ()(int)>' main.cpp:43: instantiated from here E:/Projects/Third Party/boost/boost/utility/result_of.hpp:68: error: invalid use of undefined type `struct test_function2<float>::result<test_function2<float> ()(int)>' I get the same error if I simply wrap test_function1 in another template class as nested struct and then use it instead of test_function2. Am I attempting to do something fundamentally wrong here, or is it a bug in gcc? Thanks, Martin

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1.33.1 read_graphviz possible parser issue
by Brian Stadler 28 Sep '07

28 Sep '07

Hi all, I'm reading in thousands of files in the graphviz language into a program using read_graphviz(), library version 1.33.1. I noticed a problem with some of my results and discovered that read_graphviz doesn't appear to be interpreting the files correctly. The structure of the graphs is preserved (no edges gone astray). However, the labeling of the nodes is changed. I confirmed this by reading in a file and immediately writing it back out using write_graphviz(). Below is the code used to read in the files. It's very simple as I have nothing special being reprsented. Could someone else check this and confirm this is a problem. I've checked the bugs list and 1.34.x release notes and found nothing addressing the particular issue. thanks all. My read_graphviz code: bool file; ifstream in(openfile.c_str(), ios::in); dynamic_properties dp; dp.property("node_id", get(&ed_node::vertex_name, ug)); <--simple adjacency list with bundled properties being used file = read_graphviz(in, ug, dp, "node_id"); Source graphviz file: strict graph { 0 -- 3; 0 -- 4; 1 -- 3; 1 -- 4; 2 -- 3; 2 -- 4; 3 -- 4; } Output graphviz file: graph G { 0; 1; 2; 3; 4; 0--1 ; 0--2 ; 3--1 ; 3--2 ; 4--1 ; 4--2 ; 1--2 ; }

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[gil] questions about usage
by Chris Weed 28 Sep '07

28 Sep '07

Hi, I have had great success using gil, and I have some questions and feedback. I didn't see a way to create an image of floating point values. I use my own typedef as follows, but I would think this should be in gil: typedef boost::gil::pixel<float,gray_layout_t> value32f_pixel_t; It is quite common to use square filters in image processing, and I think it would be useful to overload subimage_view with a fixed offset from all 4 sides. template <typename View> inline View subimage_view(const View& src, int border) { return View(src.width()-border*2,src.height()-border*2,src.xy_at(border,border)); } I also had a need for an "image" constructor that would take a size and allocator, but not initialize the values: image(const point_t& dimensions, std::size_t alignment, const Alloc alloc_in = Alloc()) : _memory(0), _align(alignment), _alloc(alloc_in) { allocate_and_default_construct(dimensions); } The biggest change I would suggest is adding the ability to take a view of a view, a const_view of a const_view, and a const_view of a view. This would make writing functions much easier. Thanks, Chris

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custom allocators for shared_ptr
by Cory Nelson 28 Sep '07

28 Sep '07

It would be useful if shared_ptr and family provided a way to give a custom allocator. For instance, to replace the quick allocator with a lock-free one. -- Cory Nelson

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[boost::thread] Function doesn't work out of the main thread
by Gabriel Weilenmann 28 Sep '07

28 Sep '07

Hi Everyone I have a problem with threads which I don't understand. Well, it might be also connected to OpenCV, because it only occured while calling certain OpenCV functions so far: void callCvShowImage() { // OpenCV function to display an image in a window. cvShowImage("WindowName", image); } void callCvQueryFrame() { // OpenCV function to grab an image from a camera. frame = cvQueryFrame( capture ); } In a single thread program they work as expected: ... callCvShowImage(); //Works well callCvQueryFrame(); //Works well ... In the multithreaded version they don't work. In my oppinion, exactly the same thing should happen as above. But surprisingly the functions suddenly don't execute anymore. thrdXX.join() block the program forever... ... boost::thread thrdSI(&callCvShowImage()); thrdSI.join(); // the program never gets to this point ... ... boost::thread thrdQF(&callCvQueryFrame()); thrdQF.join(); // the program never gets till here ... Is there a way to fix this? I could also use the thread library from Microsoft if you think this would help... Obviously, I'm not much into threads. So please try to give me some examples together with your answer Thanks to you people once more Gabriel -- GMX FreeMail: 1 GB Postfach, 5 E-Mail-Adressen, 10 Free SMS. Alle Infos und kostenlose Anmeldung: http://www.gmx.net/de/go/freemail

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