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[iostreams] How to overload the flush on a outpou stream
by vicente.botet 16 Nov '08

16 Nov '08

Hi, I want to to take a specific action when I flush an output stream. Can Boost.Iostreams be of any use? Thanks is advanve, Vicente

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[unordered] patch to remove warning on Visual C++
by Christopher Lux 16 Nov '08

16 Nov '08

Hi, appended is a small patch to fix some annoying warnings using Visual C++ 8.0 and 9.0. It would be nice if this could be looked at and applied to the trunk. The warnings were: 1>brick_pool.cpp 1>E:\devel\working_copies\schism_x64_vc90_sp1\externals\inc\boost\boost/unordered/unordered_map.hpp(388) : warning C4396: 'boost::operator ==' : the inline specifier cannot be used when a friend declaration refers to a specialization of a function template 1>E:\devel\working_copies\schism_x64_vc90_sp1\externals\inc\boost\boost/unordered/unordered_map.hpp(389) : warning C4396: 'boost::operator !=' : the inline specifier cannot be used when a friend declaration refers to a specialization of a function template Regards -chris -- Christopher Lux | | Bauhaus-Universität Weimar | faculty of media - virtual reality systems group

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[Multiarray] & [Range] MSVC/gcc warning: returning address of local variable or temporary
by John Reid 15 Nov '08

15 Nov '08

The following code generates a worrying warning under MSVC: #include <boost/range/iterator_range.hpp> #include <boost/multi_array.hpp> typedef boost::multi_array< double, 1 > my_array; typedef my_array::const_iterator it; void test(const my_array & a) { boost::iterator_range< it > it_range(a.begin(), a.begin() + 1); it_range[0]; } C:\Dev\ThirdParty\boost\boost_1_37_0\boost/range/iterator_range.hpp(356) : warning C4172: returning address of local variable or temporary C:\Dev\ThirdParty\boost\boost_1_37_0\boost/range/iterator_range.hpp(354) : while compiling class template member function 'const double &boost::iterator_range<IteratorT>::operator [](__w64 int) const' with [ IteratorT=it ] iterator_range.cpp(8) : see reference to class template instantiation 'boost::iterator_range<IteratorT>' being compiled with [ IteratorT=it ] I'm using msvc 8.0 express and boost 1.37.0 release. I've seen similar warnings from gcc 4.3 on similar code. Is this a problem with boost.Multiarray, boost.range or the compiler? My guess is that Multiarray has defined its iterators incorrectly. Can anyone confirm this/provide a fix? Thanks, John.

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Boost conformance to standard c++0x libraries statement
by vicente.botet 15 Nov '08

15 Nov '08

Hi, There are a lot of Boost libraries already included in the C++ Standards Committee's Library Technical Report (TR1). More Boost libraries are proposed for the upcoming TR2. As all these libraries do not conform completly to the standard for different raisons: the compliler do not support some feautres of the C++0x, the emulation seems to complex or any other justification. I think that it will help the users to have a clear statement, library by library, of which features the library conform to or not. This statement should contain the library feature(class, typedef, constants, functions, ...), dependencies on other C++0x features, whether it conforms on C++0x compilers supporting the needed compiler features, if it use some workaround on other compilers and finaly for the non conformant features why the library do not conforms. It will be also useful to state which features on the library are not on the standard. I have prepared as an example a table for the Boost.Thread library (limited tothread and this thread API). Anthony the informations on these tables could be wrong. Attached boost_thread_conformance.qbk and boost_thread_conformance.html Any comments and ideas are welcome. HTH, Vicente

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[thread] sleep() with time_duration?
by Boris 15 Nov '08

15 Nov '08

If I want a thread to sleep for five seconds the shortest code I could come up with is: boost::system_time time = boost::get_system_time(); time += boost::posix_time::seconds(5); boost::thread::sleep(time); It would be nice if it was possible to pass a time_duration object to sleep() directly: boost::thread::sleep(boost::posix_time::seconds(5)); This would also be consistent with the deadline_timer in Boost.Asio whose constructor accepts both a time and a time_duration. Boris

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[Random] design of the random library
by Ares Lagae 15 Nov '08

15 Nov '08

I have some questions regarding the design of the C++/TR1 and Boost.Random library. What are the requirements on the UniformRandomNumberGenerator argument of operator() of random distribution class templates? It seems that the only requirement is uniform distribution, and both range and type (integer / floating point) are not specified. Does this mean that the random distribution class templates work with any kind of UniformRandomNumberGenerator? Does the normal_distribution work as expected with a linear congruential uniform random number generator? Or does the normal distribution assume a continuous distribution in [0,1[? Are these requirements documented? I could not immediately find them in the documentation. It seems operator() of most random distributions will first have to construct a uniform_01 random distribution from the UniformRandomNumberGenerator argument and then transform that distribution to the required distribution (e.g. the normal_distribution would construct a uniform_01 distribution from the UniformRandomNumberGenerator argument of operator() and then use the Box-Muller transformation). I would appreciate it if someone could clarify these issues. -- Ares Lagae, Ph.D. Computer Graphics Research Group, Katholieke Universiteit Leuven http://www.cs.kuleuven.be/~ares/

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default value for a variable using template argument
by Chris 15 Nov '08

15 Nov '08

Hi, did anyone ever suggest a template class which initializes a variable to a certain value? (see example) Is this too trivial? This is useful to prevent uninitialized values in objects. class A { defaulted<int, 1280> _width; defaulted<int, 1024 > _height; defaulted<int, 0> _depth; }; template <typename TYPE, TYPE value> class defaulted { public: defaulted() : _t(value) { } defaulted(const TYPE & value2) : _t(value2) { } operator TYPE & () { return _t; } TYPE * operator & () { return &_t; } const TYPE * operator & () const { return &_t; } operator const TYPE & () const { return _t; } TYPE & operator =(const TYPE & other) { _t = other; return _t; } private: TYPE _t; };

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[thread] other thread_group functions
by vicente.botet 14 Nov '08

14 Nov '08

Hi, I would like to know which of the following thread functions have a sens for thread_group? bool joinable() const; bool timed_join(const system_time& wait_until); template<typename TimeDuration> bool timed_join(TimeDuration const& rel_time); void detach(); I have another sugestion related to the _all suffix of the thread_group functions join_all and interrupt_all. Could you add the synonyms join and interrupt? In this way a thread_group can be seen as a compound object sharing the same interface as the element thread. ______________________ Vicente Juan Botet Escribá

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[thread] getting boost::thread* form boost::thread::id
by vicente.botet 14 Nov '08

14 Nov '08

Hi Anthony, I'm working with a keep_alive mechanism. I need to interrupt threads that are considered 'dead'. I have access to the thread specific context using a map : boost::thread::id -> context. This mapping is modified by self registration from the thread. On the other side I need a boost::thread pointer to interrupt the thread. With the current Boost.Thread interface, I don't see how I can get it either from the current thread or from the thread::id. Can I? Currently only the thread creator wrapper can add this information. I think that I could add a thread creator wrapper that add this as a thread specific pointer, but I will be able to get only the thread* for the threads created with this wrapper, which is not completly satisfactory. Do you think that at least one of these functions could be of general use: one for getting a boost::thread* form a boost::thread::id and one for getting the boost::thread* of the current thread? namespace boost { class thread { // ... static thread* get_thread_ptr(id); }; namespace this thread { thread* get_thread_ptr(); } } To implement this in Boost.Thread it will be need to store the thread* on the detail::thread_data_ptr. Do you think that this could be a possible addition on the Boost.Thread library? Thanks, Vicente

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[numeric_cast] request for boost::numeric_downcast
by Thorsten Ottosen 14 Nov '08

14 Nov '08

Hi Fernando, Amoung our utilities we have boost::polymorphic_cast boost::polymorphic_downcast The latter only performs a check in debug builds, and can then be used whenever the cast must succeed. boost::numeric_cast has no such alternative. Therefore I wuold like to see one. To keep in the naming convention from above, I think it could be reasonable to call this boost::numeric_downcast Furthermore, this should if possible be implemented in a seperate header (which is included in the main header) that can be compiled without exception-support. I think there are still platforms where they need this functionality, but don't want to sue exceptions. Any comments -Thorsten

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