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[units][phoenix] static physical constants don't play well with phoenix?
by alfC 30 Apr '11

30 Apr '11

Hi, This post is just to point out a deficiency of either boost.phoenix or boost.units and see if there are workarounds. Phoenix 3 now plays well with Boos.units quantities out of the box but for some reason it does not play well with boost.units static physical constants. Like in the following example. This is because the constant 'hbar' is not a normal quantity type but a boost::units::constant< ... hbar_t > type. do you think physical constants could be defined as normal quantities in the future so it can play well with phoenix? #include<iostream> #include<boost/units/systems/si/io.hpp> #include<boost/units/systems/si/codata_constants.hpp> #include<boost/phoenix/phoenix.hpp> int main(){ using namespace boost::units; using namespace boost::phoenix; using namespace boost::phoenix::arg_names; quantity<si::action> const hbarvar = boost::units::si::constants::codata::hbar; std::clog << (arg1 * hbarvar)(5.) << std::endl; // works std::clog << (arg1 * boost::units::si::constants::codata::hbar)(5.) << std::endl; //doesn't work return 0; }

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Re: [Boost-users] [Multi-Index] Categorised Container
by Hossein Haeri 29 Apr '11

29 Apr '11

Hi Marsh, multi_index_container < T hashed_non_unique<...>, ordered_non_unique<...> > my_container; > So are you expecting hash collisions and doing something useful with > them? This is interesting, can you explain more about the problem and > why this is useful? Sure. Take T = pair<TimeStamp, shared_ptr<B> > where B is some base class for a hierarchy in my application. B has a pure virtual member function called id() which returns the same string for any instance of a class D, where D is derived from B. I will need to have all the instances the dynamic type of the second element of which is of D, but sorted according to TimeStamp's operator <. My idea was to get the first index in my_container to be this id() member function and the second index to be operator < (const TimeStamp&, const TimeStamp&). Is that doable in Multi-Index? > I think you're on the right track by calling them 'categories' and > suggest you not try to overload it with the hash value used to index the > collection (even if they happen to be the same). Sorry but I'm not sure I can follow your English here. Would you mind paraphrasing it if the issue is still important? > If you didn't want to store redundant data in T, you could define a key > extractor which runs your preferred hash function to calculate the > category on the fly. This much redundancy is not a matter for me. But, I'd rather not calculate the category on-the-fly for this container is going to be heavily accessed (and also populated/garbage-collected) for every D which derives from B. Does that make it easier to answer my questions? TIA, --Hossein

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ning Boost Regression Tests
by Ted Byers 29 Apr '11

29 Apr '11

I have been using boost for quite a while (for years I used boost without running any tests other than those I wrote myself), and am now looking at running the regression tests. I found the statement: "To run every library's regression tests, run bjam from Boost's /status directory." What I haven't found is how to view the results of that testing on my own machine. I don't know if that is a catastrophic failure of the test script, or if I just didn't invoke bjam correctly. I ran bjam (in cygwin's bash, on Windows 7), without any arguments, in boost's status directory, and it executed a lot of tests. Obviously, that produced a lot more output than can be copied here, but the last few lines of output (after many many hundreds of lines of output) were: 1 [main] bjam 9280 fhandler_dev_zero::fixup_mmap_after_fork: requested 0x772B0000 != 0x0 mem alloc base 0x772B0000, state 0x1000, size 8192, Win32 error 487 263 [main] bjam 9280 C:\cygwin\home\Ted\boost_1_46_1\bjam.exe: *** fatal error - recreate_mmaps_after_fork_failed Stack trace: Frame Function Args 0028E5D0 6102796B (0028E5D0, 00000000, 00000000, 74C98458) 0028E8C0 6102796B (6117EC60, 00008000, 00000000, 61180977) 0028F8F0 61004F1B (61180DAC, 00000000, 61180DA6, 0041A000) 0028F930 610061B1 (00000060, 02000000, 6116A724, 6116A720) 0028F960 610064C0 (00000000, 00000002, 00000000, 75053480) 0028FA20 6106FC15 (61000000, 00000001, 0028FD24, 00000001) 0028FA40 77169960 (6106F960, 61000000, 00000001, 0028FD24) 0028FB34 7716D8C9 (0028FD24, 7EFDD000, 7EFDE000, 7723206C) 0028FCB0 771837EE (0028FD24, 77130000, 77AB63F9, 00000000) 0028FD00 77182187 (0028FD24, 77130000, 00000000, 00000000) 0028FD10 77169E89 (0028FD24, 77130000, 00000000, 0001002F) End of stack trace 0 [main] bjam 8628 fork: child -1 - died waiting for longjmp before initialization, retry 0, exit code 0x100, errno 11 vfork: Resource temporarily unavailable Obviously the last test executed failed, but I found no summary of the results, nothing to indicate whether or not most of the built library was built correctly. Did the regression test script abort without producing the summary, or do I need to pass some argument to tell it to display a summary (I had in mind the kind of output you get when building gcc, and you execute 'make check' before executing 'make install', as one doesn't want to install a library or anything else that didn't get built correctly)? Thanks Ted

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Boost in an MFC app on WinNT4
by tangleman＠secules.net 29 Apr '11

29 Apr '11

I am trying to modify a current MFC application running on Windows NT4 to use boost libraries for ethernet communcications (originally, it used CommX for serial) and general increased performance, effieciency, and clarity of code. I started out modifying it in VS2010, but I found that I was unable to produce a valid NT4 app with VS2010. I googled the issue and found that VS2005 was the last version able to create an NT4 app. I got everything to compile in VS2005, but found that I had to change certain #define statements in stdafx.h in order to get the app to run on NT4. However, even after doing that, when I execute the program on NT4, it immediately quits with no error. It doesn't show anything. I even checked the Task Manager processes while executing it. It is like it never executed at all. I got desperate and tried compiling the app in VS2003, but I got so many errors that I gave that up. My last attempt was VC6, but again, I got 262 errors and started wondering whether it was even possible for boost to run in VB6 or on an NT4 machine. This is a very tight-schedule project, so any (prompt) help would be very appreciated! Thank you!

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[boost::fusion] map or set uniqueness guarantees
by Ovanes Markarian 29 Apr '11

29 Apr '11

Hello *, I am wondering if I should expect some uniqueness guarantees on contained element from fusion set or map containers? In this example: struct print_value { template<class T> void operator()(T& v)const { cout << typeid(T).name() << " has value: " << v << endl; } }; boost::fusion::set<int, int, int> s; boost::fusion::for_each(s, print_value()); I get 3 lines - one for each int I put in. I would expect only one line. What are my expectations for at_key? Which int would it return? Which type is going to be returned after I inserted the same type again? May be the better question would be, is the new type inserted as the head element or at the end of the underlying list? Many thanks for the anserws? With Kind Regards, Ovanes

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Asio handle_read this=0x0 in http server3 example
by Matthijs Möhlmann 29 Apr '11

29 Apr '11

Hello, When compiling example http/server3 then I get a segmentation fault. GDB gives the following trace: #0 0x000000000040e2a2 in http::server3::request_parser::parse<char*> ( this=0x2078, req=..., begin=0x48 <Address 0x48 out of bounds>, end=0x273 <Address 0x273 out of bounds>) at request_parser.hpp:42 #1 0x000000000040743e in http::server3::connection::handle_read (this=0x0, e=..., bytes_transferred=555) at connection.cpp:48 As you see the 'this=0x0' in #1 is not correct I think. I think this has to do with the internals in Asio but I'm not sure. I'm using g++ 4.6 in combination with boost trunk. I'm not able to reproduce this with boost 1.46.1. Regards, Matthijs Möhlmann

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is there a function can get two file path relative path?
by k 29 Apr '11

29 Apr '11

the boost filesystem library provide relative_ path() but it only give relate root directory. or is it other function can do it?

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[Boost][enable_if] SFINAE and decltype
by Germán Diago 28 Apr '11

28 Apr '11

Hi all, I'm having a hard time trying to figure out how to make a code like this to improve error messages through static_assert. I want that when the function instantiation fails, the other function's static assert fails. I don't know how to do it. I began with something like this: template <class Range, class T> Range find(Range && haystack, const T & elem) { static_assert(std::is_convertible<decltype (elem == haystack.front())>::value, "elem and haystack must be equality comparable"); while (!haystack.empty() && !(haystack.front() == elem)) haystack.popFront(); return haystack; } But that didn't work since when decltype is applied to an invalid expression, SFINAE doesn't trigger in the function body. So now I'm trying an alternative like this, but I don't know how to express it: template <class Range, class T> Range find(Range && haystack, const T & elem, decltype (elem == haystack.front()) * = 0) { while (!haystack.empty() && !(haystack.front() == elem)) haystack.popFront(); return haystack; } template <class Range, class T> Range find(Range && haystack, const T & elem, !decltype (elem == haystack.front()) * = 0) { static_assert(..., "haystack.front() and elem must be equality comparable"); return haystack; } I can't figure out how to make it work. I also tried with boost::enable_if but the problem is that a bool expression doesn't have a ::value member. Could anyone suggest me THE SIMPLEST and most readable way to make this work? Thanks in advance. P.S.: By the way, I also tried structs and partial specialization, but no luck.

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Read/write with gzip
by Anders Knudby 28 Apr '11

28 Apr '11

Hello, I previously managed to write data to a gzipped file using the following code structure (it's an example of course, the "memblock" is actually filled with real data and the real filename is specified elsewhere). #include <boost/iostreams/filtering_streambuf.hpp> #include <boost/iostreams/filtering_stream.hpp> #include <boost/iostreams/copy.hpp> #include <boost/iostreams/filter/gzip.hpp> #include <boost/iostreams/device/file_descriptor.hpp> #include <boost/filesystem.hpp> namespace io = boost::iostreams; int size = 1000; char* memblock = new char [size]; io::filtering_ostream out; out.push(io::gzip_compressor()); out.push(io::file_descriptor_sink("c:/outfile.gz")); out.write (memblock, size); That works fine. I would now like to read these data again. I imagined I could do something like the following (using the same #include statements etc. as above): int size = 1000; char* memblock = new char [size]; io::filtering_istream in; in.push(io::gzip_decompressor()); in.push(io::file_descriptor_source("c:/outfile.gz")); in.read (memblock, size); That complies and runs, but it doesn't give me the real data back. What am I doing wrong? Anders

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boost build problem?...
by Krzysztof 28 Apr '11

28 Apr '11

I wrote a few lines of code just for start with a library of boost (program_options). Before I did it I had built boost library as prescribed and *.a and *.so files were created in my /home/krzysztof/Documents/Projects/boost/lib directory. However, compilation fails because of undefined references of some external symbols which belongs to program_options library. Could anyone help me with it? Below, there is the code and g++ output. (Linux 64b, Qt Creator and Code::Blocks used as IDE) #include "boost/program_options.hpp" using namespace boost::program_options; using namespace std; int main(int argc, char *argv[]) { options_description opd; opd.add_options() ("help","Display help") ("input_file,if",value<string>(),"Specifies input file") ("fet_file",value<string>(),"definitions file") ("output_file,of",value<string>(),"file after edition"); } g++ -o fetxedit main.o -L/usr/lib -L/home/krzysztof/Documents/Projects/boost/lib -lQtCore -lpthread main.o: In function `main': /home/krzysztof/Documents/Projects/fetxedit-build-desktop/../fetxedit/main.cpp:8: undefined reference to `boost::program_options::options_description::m_default_line_length' /home/krzysztof/Documents/Projects/fetxedit-build-desktop/../fetxedit/main.cpp:8: undefined reference to `boost::program_options::options_description::m_default_line_length' /home/krzysztof/Documents/Projects/fetxedit-build-desktop/../fetxedit/main.cpp:8: undefined reference to `boost::program_options::options_description::options_description(unsigned int, unsigned int)' /home/krzysztof/Documents/Projects/fetxedit-build-desktop/../fetxedit/main.cpp:14: undefined reference to `boost::program_options::options_description::add_options()' /home/krzysztof/Documents/Projects/fetxedit-build-desktop/../fetxedit/main.cpp:14: undefined reference to `boost::program_options::options_description_easy_init::operator()(char const*, char const*)' ... and so on -- Regards Krzysztof Jasieński

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