December 2010 - Boost-users - lists.preview.boost.org

Re: [Boost-users] boost::interprocess boost::interprocess xsi_shared_memory
by Daniel Neuberger 12 Jan '11

12 Jan '11

Is there a reason for not finishing the implementation of XSI (System V) shared memory? It seems like most of the work is already done. If there is no reason not to, I might be able to finish the implementation so that it can be included in the next release. I know that POSIX may be sufficient for some, but System V allows for much better control using SELinux since it lives in kernel space. FYI: This is in response to http://thread.gmane.org/gmane.comp.lib.boost.user/64537. Thoughts? Thanks. - Daniel

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[Iterator] advance and random_access_traversal iterators
by Anthony Foglia 11 Jan '11

11 Jan '11

What happened to the patch to add a boost::advance function designed to work with Boost.Iterator's concepts? Three years ago there was a thread pointing out the problem with std::advance not treating random access traversal iterators as random access (because of the reference type). Sebastian Redl posted a patch to add a boost::advance (and boost::distance) function. <http://lists.boost.org/Archives/boost/2007/09/127785.php> I don't see any proof of this patch ever being applied. Someone filed a bug report two years ago to bring attention to the patch, and it still hasn't been applied. <https://svn.boost.org/trac/boost/ticket/2539> Is there a reason it hasn't been applied (the collision with the boost::distance supplied by Boost.Range?) or has it just fallen through the cracks? -- Anthony Foglia Princeton Consultants (609) 987-8787 x233

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[DateTime] Daily Schedules
by John Rocha 07 Jan '11

07 Jan '11

I was looking at the DateTime library for a scheduling module in my application. I was very excited to see time periods (time_period) and its method contains(). I could set up a time_period for say 8:00-17:00, and then when something happened I could create a ptime and see if the time_period contains my ptime. (i.e. did my action happen between 8:00 and 17:00.) However, I realized that a time period is much more specific than I want. A time_period is tied to a specific date, i.e. 8:00-17:00 on Sep. 20 1999. I read the documentation, and I didn't see (or missed) anything that might be what I would call an hour period -- a range of time that is independent of the date. I don't think it's a duration, because I understood that to mean the amount of time between two time points (i.e. +/- 5 hours). I have some ideas on how I might extend this to achieve what I want, but before going that route, I wanted to double check if others have encountered this and if so how they resolved it. Was it done with a bit of the library that I'm overlooking? Or did you have to extend the class to achieve the desired results? Thanks in advance, -=John

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[Accumulators] Retract samples
by Alex Hagen-Zanker 06 Jan '11

06 Jan '11

Dear all, I am considering using Boost Accumulators for a moving window calculation. When a window would step from left to right, it should add the sample on the right side of the window and retract the sample on the left side on each step. For weighted accumulators, it might be possible to use negative weights. But, since the accumulators do not appear to be intended for this use, there may be implementation details that invalidate the use of negative weights. Is there a recommended way to retract samples in Boost Accumulators? Thanks, Alex p.s. the general idea: void movingwindowsum(const vector<double>& in, vector<double>& out, size_t radius ) { size_t n = in.size(); double sum = 0; // This should be an accumulator for(size_t i = 0; i < min(n, radius); ++i) { sum += in[i ]; // add sample } out.resize(n); for(size_t i = 0; i < n; ++i) { size_t left = i - radius - 1; size_t right = i + radius; if (left >= 0) sum -= in[left]; // retract sample if (right < n) sum += in[right]; // add sample out[i] = sum; }

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Problems in CodeGear
by jose perez 06 Jan '11

06 Jan '11

Hello. I'm unable to compile boost in Embarcadero 2010 (CodeGear) version 0x621. My code is really simple: #include "boost/random/mersenne_twister.hpp" This produces this error: [BCC32 Error] mersenne_twister.hpp(63): E2299 Cannot generate template specialization from 'detail::disable_constructor<Engine,T>' in the line: BOOST_RANDOM_DETAIL_GENERATOR_CONSTRUCTOR(mersenne_twister, Generator, gen) { seed(gen); } I have preprocessed my .cpp in order to see if boost gets correctly self configured for CodeGear compiler. It does very well, because it enters into codegear.hpp. But the last checked version of the CodeGear compiler is 0x620, and my version is 0x621. I have tried to change this line: // versions check: // last known and checked version is 0x620 #if (__CODEGEARC__ > 0x621) and this one: // CodeGear C++ Builder 2010 #if (__CODEGEARC__ <= 0x621) / # define BOOST_NO_TYPENAME_WITH_CTOR // Cannot use typename keyword when making temporaries of a dependant type etc... so that the compiler ignores or enters those sections, but nothing changes. It seems slightly strange to me that version 0x620 and 0x621 are SO different that boost is unable to get compiled. This problem has raised when trying to compile my application with libLAS library, which uses guid.hpp (which uses mersenne_twister.hpp), and there are much more compiler errors than the one I am explaining here. I guess (and hope) they are part of the same problem. No problems arise with other boost modules like, for example, "boost/smart_ptr.hpp". Help will be appreciated. Thanks!

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[property_tree] Parsing JSON
by Olivier Tournaire 05 Jan '11

05 Jan '11

Hi all, I am currently trying to parse a JSON file, but cannot figure how to achieve this task (see for instance http://ax.itunes.apple.com/WebObjects/MZStoreServices.woa/wa/wsSearch?term=… ). Here is a piece of code: #ifndef ITUNES_JSON_STRUCTURE_HPP #define ITUNES_JSON_STRUCTURE_HPP #include <boost/property_tree/ptree.hpp> #include <string> class itunes_json_structure { public: void load(const std::string &filename); boost::property_tree::ptree m_ptree; }; #endif // ITUNES_JASON_STRUCTURE_HPP #include "itunes_jason_structure.hpp" #include <boost/property_tree/json_parser.hpp> #include <iostream> using namespace std; void itunes_json_structure::load(const string &filename) { using boost::property_tree::ptree; try { // Load the JSON file into the property tree. If reading fails // (cannot open file, parse error), an exception is thrown. read_json(filename, m_ptree); cout << "resultCount = " << m_ptree.get<string>("resultCount") << endl; ptree all_results = m_ptree.get_child("results"); // HERE!!! How can I read the content of the "results" node???? } catch(exception &e) { throw e; } } I am unable to read the content of the "results" node. Could you please give me some help? Regards, Olivier

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Visualizer for boost::tuple
by Mohamed Bana 05 Jan '11

05 Jan '11

Hello, I can't seem to find a visualizer for boost::tuple, does anyone have one lying around somewhere? I'm using Visual Studio 2005, if that's of any help. I appreciate the help. —Mohamed

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[Proto] callable_context
by Hossein Haeri 04 Jan '11

04 Jan '11

Dear all, I am trying to use callable_contexts to evaluate expressions like: x >> f >> g >> h; where this would be equivalent to h(g(f(x))). I have derived my context from callable_context, and thought I have overloaded for relevant tags (terminal and shift_right). GCC 4.5.1 (MinGW32, WinXP, SP3) stops with an error message which is cryptic to my current level of knowledge about Proto. I guess that's because I haven't done the job correctely. For your reference, I have included a copy of my program as well as the error GCC gives me in the P.S. section of this posting. Any ideas please? TIA, --Hossein P.S. <code> #include <iostream> #include <boost/proto/proto.hpp> namespace mpl = boost::mpl; namespace proto = boost::proto; using proto::_; using namespace std; struct EWGrandDad { int evaluate() const; }; typedef proto::terminal<double (*) (double)> FunctionType; template<typename> struct EmtExpr; struct EmtGrammar: proto::or_ < proto::terminal<EWGrandDad>, proto::shift_right<EmtGrammar, FunctionType> > {}; struct EmtDomain: proto::domain<proto::generator<EmtExpr>, EmtGrammar> {}; template<typename Expr> struct EmtExpr : proto::extends<Expr, EmtExpr<Expr>, EmtDomain> { typedef proto::extends<Expr, EmtExpr<Expr>, EmtDomain> base_type; EmtExpr(const Expr& e = Expr()): base_type(e) {} }; struct EWBase : EmtExpr<typename proto::terminal<EWGrandDad>::type> { typedef typename proto::terminal<EWGrandDad>::type expr_type; EWBase(): EmtExpr<expr_type>(expr_type::make(EWGrandDad())) {} }; struct EW1: EWBase { EW1(int n1, int n2): n1_(n1), n2_(n2) {} int evaluate() const {return n1_ * n2_;} int n1_, n2_; }; double times2(double d) {return d * 2;} double minus1(double d) {return d - 1;} struct EmtContext: proto::callable_context<const EmtContext> { typedef double result_type; result_type operator() (proto::tag::terminal, const EWGrandDad& ew) const { return ew.evaluate(); } template<typename Expr> result_type operator() (proto::tag::shift_right, const Expr& e, FunctionType f) const { return f(proto::eval(e, *this)); } }; int main() { EmtContext emtCtx; cout << "result = " << emtCtx(EW1(4, 5) >> &times2 >> &minus1); return 0; } </code> <error message> main.cpp: In function 'int main()': main.cpp:82:63: error: no match for call to '(EmtContext) (const boost::lazy_enable_if_c<true, boost::proto::generatorns_::generator<EmtExpr>::result<EmtDomain(boost::proto::exprns_::expr<boost::proto::tag::shift_right, boost::proto::argsns_::list2<const EmtExpr<boost::proto::exprns_::expr<boost::proto::tag::shift_right, boost::proto::argsns_::list2<const EW1&, EmtExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<double (* const&)(double)>, 0l> > >, 2l> >&, EmtExpr<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<double (* const&)(double)>, 0l> > >, 2l>)> >::type)' main.cpp:67:14: note: candidate is: EmtContext::result_type EmtContext::operator()(boost::proto::tag::terminal, const EWGrandDad&) const </error message>

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Mingw64 Boost Threads Build
by Dustin T. Clifford 04 Jan '11

04 Jan '11

Good Afternoon, We have been using boost-threads for our native APIs and, thus far, Boost has been a godsend! We had a recent request to build a 64-bit version of this API. To accomplish this we have attempted to build using MinGW64. Unfortunately, I have had zero luck getting boost-threads to build. I can build the 32-bit address model without a problem but 64-bit continues to elude me. I first tried Boost 1.35.0 and have now moved on to 1.45.0. I believe that the environment is set up correctly (see below). This build is being performed on a Windows 7 64-bit using MinGW64 from Cygwin. export CC=x86_64-w64-mingw32-gcc.exe export CXX=x86_64-w64-mingw32-g++.exe export LD=x86_64-w64-mingw32-ld.exe I have, also, modified my PATH to use the appropriate 64-bit bintools and aliased gcc, g++ and ld to the 64-bit MinGW64 compilers and linkers. To build Boost I have used the following with no success. boostrap.sh address-model=64 -prefix=<install> --with-libraries=thread; bjam -a install; boostrap.sh -prefix=<install> --with-libraries=thread; bjam -a address-model=64 install; boostrap.sh -prefix=<install> --with-libraries=thread; bjam -a install; The last build attempt succeeds but appears to have built 32-bit binaries. The previous two fail in building boost-threads complaining that 'address-model-64' is not found for certain build artifacts. I have, also, tried the above with a prebuilt bjam with the same results. I have tried much more than what I have cited here (including MSVC builds) with no success (some built but resulted in 32-bit binaries). I have scoured Google and found many talking about this but most either had no resolution or contained instructions that conflicted or made no sense. Does anybody have any insight into how I can produce a 64-bit boost-threads archive? Any help would be greatly appreciated. Thanks in advance, Dustin P.S. If I have missed any information or you need more (build logs are too big to attach), please, let me know.

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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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