May 2007 - Boost-users - lists.preview.boost.org

[MPL] Runtime traversal of a type sequence until a condition is true
by Scott Meyers 24 May '07

24 May '07

I'm interested in taking Andrei Alexandrescu's Ad Hoc Visitor technique (http://tinyurl.com/2k8h2h) and implementing it using the MPL. I need to implement a runtime function that iterates over an MPL type sequence until a dynamic_cast succeeds. Here's some pseudocode, where I use "typelist" to mean an MPL type sequence: class UnknownType { ... }; // for exceptions template <typename TL> // TL = "typelist" void visit(ASTNode *pn) { for (each type T in TL) { // try dynamic_ if (T *pT = dynamic_cast<T*>(pn)) { // casting to all v.process(pT); // the types in TL return; } throw UnknownType(typeid(*pn)); // throw an ex. if } // no type matches I can make this work if I replace the for loop with a use of mpl::for_each, but for_each iterates over all elements of the type sequence, and I want to stop when a dynamic_cast succeeds. I can hack the function object I pass to for_each to have it be a no-op once a successful dynamic_cast has been encountered, but the operative word there is "hack." What I really want is something more like do_until<Sequence>(unaryFunctionObject) that will loop over all the entries in Sequence until the unaryFunctionObject returns true. Is there something like this in the MPL, must I roll my own, or am I approaching this the wrong way entirely? Thanks, Scott

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removing a subset of bits from a boost::dynamic_bitset...
by Graham Reitz 24 May '07

24 May '07

What is an efficient method using dynamic_bitset to do the following? bitset1<16> = 0xabcd mask<16> = 0x000f result<4> = (bitset1 & mask) What is the syntax to remove a subset of bits from a dynamic bitset? Thanks, Graham

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BOOST_FOREACH and iterating by reference
by Daniel Gehriger 24 May '07

24 May '07

I tried BOOST_FOREACH on a slightly modified version of the sample in the documentation. Instead of iterating by value, I iterate by reference: extern std::vector<float> get_vector_float(); BOOST_FOREACH( float& f, get_vector_float() ) { } When compiling with VisualC++ 8.0, I receive the following error message: error C2440: 'initializing' : cannot convert from 'const float' to 'float &' Conversion loses qualifiers Is there a work-around ? - Daniel -- View this message in context: http://www.nabble.com/BOOST_FOREACH-and-iterating-by-reference-tf3806531.ht… Sent from the Boost - Users mailing list archive at Nabble.com.

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[program_options] unknown options in config files
by Ram V 24 May '07

24 May '07

Hi, This is a feature request for the program_options library. A clean and extensible design for my code stipulates that it will be best to pass the user input (command line / config file) around to different modules which then extract the relevant options using the program_options library. This will mean neglecting all options that are irrelevant to the current module. However, it appears that this is possible only from the command line and not from the config file. Ideally, it will be great if the api for parsing config files mirrors what exists for the command line. That would mean a basic_config_file_parser class with chainable allow_unregistered() and collect_unrecognized() methods for the config file parsing. Some searching shows that there have been a couple of similar requests on this list: http://thread.gmane.org/gmane.comp.lib.boost.user/25035 http://thread.gmane.org/gmane.comp.lib.boost.user/24398 <http://thread.gmane.org/gmane.comp.lib.boost.user/24398> and on the developers' list: http://thread.gmane.org/gmane.comp.lib.boost.devel/150415 http://thread.gmane.org/gmane.comp.lib.boost.devel/86380 <http://thread.gmane.org/gmane.comp.lib.boost.devel/150415> It also appears that a issue ticket was opened on sourceforge: http://thread.gmane.org/gmane.comp.lib.boost.devel/145941 I am wondering if there are any plans to add support for this soon. If not, any thoughts from the library developers or other users on how they think its best to do-it-myself will be appreciated. Thanks RamV

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Distributing Boost.Program_options
by Chris Thachuk 24 May '07

24 May '07

Hello all, I'm a first time user of boost libraries and I'm finding them extremely useful. I will be incorporating their use into a number of open source research projects. I've searched the archives on how to distribute the boost source with my code. It seems the bcp tool is the way to go for this, however, I'm confused on how to use it for my purpose. I would like to keep the code as portable as possible without users needing to install additional libraries on their own. Since most of the boost libraries are all contained in header files, it seems easy to distribute. However, I always getting linking errors unless I link against a pre-built library for Boost.Program_options. Is it necessary for this library to be built first, then linked against? How could I use the 'bcp' tool to grab the needed Boost dependencies for my project? Can I use a standard make file as the users wouldn't have bjam installed? My apologies if this is covered in an obvious location. I've found the documentation to be helpful, but I haven't found what I've needed yet to accomplish this. Any help would be greatly appreciated. Best, Chris Thachuk Graduate Student Simon Fraser University Vancouver, BC, Canada

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Bug :: bzip2_decompressor
by scan man 24 May '07

24 May '07

I modified the test program shipped in the boost::iostreams to decompress a 1.5 GB file which expand to 6GB. The program exits after writing 900KB of data without throwing exceptions. It is reproduced below, I was told in the irc channel that this was a bug in alloc and will be probably fixed in 1.34.1. -r #include <fstream> #include <iostream> #include <boost/iostreams/filtering_stream.hpp> #include <boost/iostreams/copy.hpp> #include <boost/iostreams/filter/bzip2.hpp> using namespace std; namespace bio = boost::iostreams; int main ( int argc, char ** argv ) { if (argc < 2) { fprintf(stderr, "Usage: %s data_filename\n", argv[0]); exit(0); } ifstream file(argv[1], ios_base::in|ios_base::binary ); if ( !file.good() ) { fprintf(stderr, "Unable to open file%s\n", argv[1]); exit(0); } else { try { bio::filtering_stream < bio::input > in; in.push( bio::bzip2_decompressor () ); in.push( file ); bio::copy ( in, cout ); } catch ( const std::exception& e ) { std::cerr<<"\nCaught std::exception " << ": "<< e.what() << std::endl; } } }

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boost condition deadlock
by jc 24 May '07

24 May '07

hello all i'm new to boost thread. i'm converting my win32 based thread application to boost so that in future i can be portable. this is my code void CVectorCAN::xlVectorThreadByCh(void){ //do something here while(m_bVectorThreadAlive){ WaitForSingleObject(m_hxlEventHandle, 50); xlStatus = XL_SUCCESS; while(!xlStatus){ if(m_bReceiveStatus){ { boost::mutex::scoped_lock lock1(m_AckMutex1); m_bVectorThreadDead = true; m_cond1.notify_one(); } return; } //process data here }//while xl_success }//while the thread is alive m_bVectorThreadDead = true; } int CVectorCAN::KillVectorBoostThread(void){ boost::mutex::scoped_lock lock2(m_AckMutex1); m_bVectorThreadAlive = false; m_bReceiveStatus = true; while(!m_bVectorThreadDead){ m_cond1.wait(lock2); } m_pVectorThread->join(); delete m_pVectorThread; m_pVectorThread = NULL; return 0; } my function deadlocks in the m_cond1.wait(lock2) i have no idea what i'm doing wrong. any pointer in the right direction will be great thanks -- jc (jayachandran kamaraj)

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Re: [Boost-users] [filesystem] is_directory on root throws
by james.jones＠firstinvestors.com 24 May '07

24 May '07

From: "David Neubelt" <david(a)readyatdawn.com> > I checked and verified the folder does exist, I'm guessing the problem > is that the directory is in the format c:folder instead of c:\folder. That most likely is the problem, since those are (probably) different directories. c:folder refers to a directory or file named "folder" in the **current working directory** of C:, whereas c:\folder refers to a directory or file named "folder" in the root of C:. - James Jones Administrative Data Mgmt. Webmaster 375 Raritan Center Pkwy, Suite A Data Architect Edison, NJ 08837

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[Serialisation] Explicit instantiation of serialize when used in library
by Hughes, James 24 May '07

24 May '07

Hello all (but probably mostly Robert) I have a class in a library which has a serialise function. It's defined in the header but implemented in the cpp file. However, I am getting an unresolved error, because when the library is build there is no need to instantiate the serialise function, as its only called by something using the library. So, I have tried to explicitly instantiate the missing function in the cpp file in the library, after the serialise implementation template class LCPanel::serialize<boost::archive::xml_iarchive>(boost::archive::xml_iar chive&, unsigned int) However, this line gives an error Expected ')' before '&' token I'm not sure where I am going wrong here as syntax appears correct (but I am not sure of), any ideas? James This message (including any attachments) contains confidential and/or proprietary information intended only for the addressee. Any unauthorized disclosure, copying, distribution or reliance on the contents of this information is strictly prohibited and may constitute a violation of law. If you are not the intended recipient, please notify the sender immediately by responding to this e-mail, and delete the message from your system. If you have any questions about this e-mail please notify the sender immediately.

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Cannot build boost with Intel Compiler 9.1 on Windows
by Iliyan Georgiev 24 May '07

24 May '07

Hi, Today was a painful and frustrating day. I've been trying to build Boost 1.34 with Intel C++ Compiler 9.1 for hours L I have tried on 4 machines - all of them running either XP or Vista, with installed Visual Studio 2005 and Intel Compiler 9.1. I get the same errors. Here's what I do: 0. Run iclvars.bat to set the environment variables 1. Download the latest boost distribution sources 2. Extract them 3. Download the latest version of bjam (ot build it myself with VC8) 4. Put bjam.exe to the root of boost 5. Run bjam from the boost root (tried with several command lines, i.e. bjam -build-dir=build -toolset=intel-win32 stage) The process starts (warns me about not having Python, which is ok), but the first time compile-c-c++ is run, the windows message "I don't know how to open this file" appears for the file extension .rsp. I dismiss the window for every file (quite annoying) but then the build script cannot find some files and it all messes up. What happens here? What's wrong? In the list archives I found a guy reporting similar troubles with an older version, and the reply suggested to set some variables and to follow a link with more info, which was dead. Anyway, this was for the old version 1. How to deal with this now? I really feel helpless L

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