August 2015 - Boost-users - lists.boost.org

[Interprocess] Problem with file_lock on Linux
by Jan Niklas Hasse 31 Aug '15

31 Aug '15

The following code #include <boost/interprocess/sync/file_lock.hpp> #include <iostream> #include <fstream> int main() { std::ofstream file("test.lock"); boost::interprocess::file_lock flock("test.lock"); std::cout << flock.try_lock(); std::cout << flock.try_lock() << std::endl; } outputs 10 on Windows and 11 on Linux. Shouldn't it also print 10 on Linux or am I missunderstanding file_lock? I've also tried locking from different threads, but no luck.

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[SPAM] from: giridhar
by giridhar 30 Aug '15

30 Aug '15

Sup boost http://arheatingcooling.com/unlikely.php?rule=g94y8vfvqvgeu2 giridharms(a)gmail.com giridhar

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[variant][mpl] silly mistake in make_variant_over usage?
by Nat Goodspeed 29 Aug '15

29 Aug '15

The following program fails to compile (148 lines of errors, will paste on request) with g++ (Ubuntu 4.9.2-0ubuntu1~14.04) 4.9.2 in -std=c++11 mode. This is using Boost 1.59.0. Command line: g++ -std=c++11 -I ~/boost_1_59_0 -o make_variant make_variant.cpp I assume I'm making a simple error. I would appreciate your pointing it out. Thank you! (Is there a simpler way to obtain a variant of the result types of passed functions? I was hoping I could just write: boost::variant< std::result_of<Fns>::type... >.) #include <boost/variant/variant.hpp> #include <boost/mpl/vector.hpp> #include <boost/mpl/transform.hpp> #include <type_traits> // std::result_of template < typename... Fns > typename boost::make_variant_over< boost::mpl::transform< boost::mpl::vector<Fns...>, std::result_of<boost::mpl::_1> > >::type multiplex(Fns && ... functions) { typedef typename boost::make_variant_over< boost::mpl::transform< boost::mpl::vector<Fns...>, std::result_of<boost::mpl::_1> > >::type return_t; // dummy for now return return_t(); } int main(int argc, char *argv[]) { boost::variant<int, char*> var = multiplex([argc](){ return argc; }, [argv](){ return argv[0]; }); return 0; }

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is it possible to group values with Boost's rtree?
by Andy Edwards 27 Aug '15

27 Aug '15

Hi everyone, I need a way to take a collection of 3D objects and put them into disjoint minimally overlapping groups no bigger than some N. Can this be done with Boost's rtree or any other Boost libraries? I've done this by putting the objects in an R* tree and using the nodes at a certain level of the tree (for example, 2 levels up from the leaf level) to determine the groups. However, that was in my own Java R* tree implementation that provided read-only access to its internal nodes. I'd like to port this program to C++ using Boost's rtree, but it doesn't provide read-only access to its nodes, does it? Does anyone know if it would be possible to extend the rtree to provide this? Or would it be possible to write a custom predicate to get the groupings? Thanks! Andy

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[filesystem] Relative Draft Proposal RFC
by Beman Dawes 27 Aug '15

27 Aug '15

There have been requests for a Filesystem library relative function for at least ten years. The requested functionality seems simple - given two paths with a common prefix, return the non-common suffix portion of one of the paths such that it is relative to the other path. In terms of the Filesystem library, path p("/a/b/c"); path base("/a/b"); path rel = relative(p, base); // the requested function cout << rel << endl; // outputs "c" assert(absolute(rel, base) == p); If that was all there was to it, the Filesystem library would have had a relative function years ago. Critical issues: Clashing requirements, symlinks, directory placeholders (dot, dot-dot), user-expectations, corner cases. A paper by Jamie Allsop, Additions to Filesystem supporting Relative Paths, is what broke my mental logjam. Much of [my proposal] is based directly on Jamie's analysis and proposal. The weakly_canonical function and aspects of the semantic specifications are my contributions. Mistakes, of course, are mine. The full proposal is at http://boostorg.github.io/filesystem/relative_proposal.html A preliminary implementation is available in the feature/relative2 branch of the Boost Filesystem Git repository. See github.com/boostorg/filesystem/tree/feature/relative2 The overall plan is to get feedback from boost developers, then merge to develop for boost 1.60, then propose to the C++ committee for addition to the Filesystem TS. Comments welcome. If you are one of the many people who have requested "relative" functionality, does this proposal meet your needs? If not, why? Thanks, --Beman

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Avoid including path to BOOST into exe
by Pavel Seleznev 27 Aug '15

27 Aug '15

Hello, I have the same question as described here http://stackoverflow.com/questions/32141335/avoid-including-path-to-boost-i… I have built BOOST with the following command line: b2 --toolset=msvc-10.0 --stagedir=./stage/2010/win32 address-model=32 variant=release threading=multi link=static runtime-link=static then compiled a project with statically linked runtime and release configuration with NDEBUG, BOOST_DISABLE_ASSERTS defined. Compiler options: c++\advanced\use full paths (/FC) is off c++\general\debug information format (/ZI /Zi /Z7) is empty ...and still having the entries in my binary file: c:\work\boost/xpressive/basic_regex.hpp void __cdecl boost::xpressive::detail::throw_on_stack_error(bool) Regex stack space exhausted c:\work\boost/xpressive/detail/dynamic/parse_charset.hpp void __thiscall boost::xpressive::detail::char_overflow_handler::operator () How can I avoid this? Regards, Pavel

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Using boost modified bessel functions with complex arguments
by Ross Kynch 27 Aug '15

27 Aug '15

Dear all, Does anyone know how to call boost's modified bessel function of the first kind using a complex argument? Specifically I want the positive half integer order with complex argument so I use: #include <boost/math/special_functions/bessel.hpp> std::complex<double> output = boost::math::cyl_bessel_i(double nhalf, std::complex<double> x); but this gives me a huge list of compiler errors which seems to suggest the std::complex<double> template isn't valid. I am able to call other boost math library functions so I don't believe my install is to blame here. Thanks for any help Ross

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Asio io_service and Thread scheduler/executor
by Mikael Olenfalk 26 Aug '15

26 Aug '15

Hi, I am currently thinking about how to move our project at work from a set of specific threads (1 thread per module e.g.) and our own network library abstraction to Boost.Asio and Boost.Thread's scheduler/executors. Before I read about schedulers/executors I considered just using asio::io_service (with a pool of threads calling .run()) for quick-shot background offloading, but after looking at scheduler/executor I would prefer using it for background work. Does anybody have any experience how to combine boost::asio with boost::thread's scheduler/executors? In my preferred design I would only have one thread pool backing both asio work and background computational tasks (e.g. using boost::async(Executor&, F&&, ...) ) My initial gut feeling was to have a thread-pool calling boost::asio::io_service.run() and then wrap that in an executor. I guess what I am asking for if somebody has any previous experience to share with this or similar approaches. Kind regards, /M

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Fw: Use of QMutex not as expected
by Don El Ron 26 Aug '15

26 Aug '15

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Boost Social Event at CppCon
by Jon Kalb 25 Aug '15

25 Aug '15

Boosters, Because a lot of Boosters are going to be attending CppCon, we¹d like to arrange a social event for Boosters/C++Now regulars. http://cppcon.org/ If you are planning to attend CppCon or even If you are just going to be in or around Bellevue, Washington between September 20th and 25 and you¹d like to join us for dinner, please let us know so we can get a count. Please send mail to: social(a)boost.org Once we settle on a date, etc, we¹ll let everyone who responded know when and where, so please let us know, even if you are a ³maybe.² I hope to see you at CppCon. Jon

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