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[range] istream_range from a temporary istream
by Nathan Ridge 22 Jul '11

22 Jul '11

Hello, The boost::istream_range function currently takes its parameter by lvalue reference (i.e. istream&). Can this be changed to rvalue reference (istream&&)? This way one can write things like: vector<T> v; push_back(v, istream_range<T>(ifstream("some_file.txt"))); Regards, Nate.

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boost::units primer explained / conversion factors required
by Michael Powell 22 Jul '11

22 Jul '11

Okay, here's what we need to get at, for starters. And maybe an illustration or three and a little exchange will go a long way towards helping my better comprehend units. I'm starting with a set of SI calculations for oil and gas constants calculations. Eventually we will need to accommodate US units as well. But not quite yet. We need to get at a calculation involving Pressure Gradient, which ends up being metric::bar/si::meter (bars over meters) in specific units, or I suppose si::pressure/si::length might also work. Then we need to get after Fluid Density, which ends up being si::kilogram/si:meter^3 (kilograms over cubic meters) in specific units, or I suppose si::mass/si::meter^3 (I don't know what this looks like in terms of boost::units, maybe one of the volumes?), or perhaps make use of mass_density? We take all that and divide Pressure Gradient by Fluid Density to arrive at what we hope will be the the conversion factor: 0.0000981. Which we could specify that as a constant, but I like proving it through the software first (plausibly once) when we ask for it. Similar type calculations would follow for US units involving gallons, cubic inches, inches, and inches per foot, along these lines. So I need some examples will spell it out for me. The learning curve using boost::units is just too steep for me right now without it. Any tips or pointers along these lines would be much appreciated. Thank you, Michael

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[serialization] Memory leaks even with shared_ptrs
by cc caprani 22 Jul '11

22 Jul '11

Hi All, Sorry for posting twice in two days, but I'm having lots of trouble getting this right. Robert points out in the bus route example that the memory leaks can be solved using shared_ptrs (bottom of this page: http://www.boost.org/doc/libs/1_47_0/libs/serialization/doc/tutorial.html#e… ) I have a basic example (below), quite like the bus route, that has memory leaks when using raw pointers. I've converted it to shared_ptrs but the leaks are exactly the same. Where have I gone wrong? I'm using VS2010 (hence the memory leak headers & function call to _CrtDumpMemoryLeaks();). Any help much appreciated! -------------------------------------------------------- Example that replicates problem: #define _CRTDBG_MAP_ALLOC #include <stdlib.h> #include <crtdbg.h> #include <boost/archive/xml_iarchive.hpp> #include <boost/archive/xml_oarchive.hpp> #include <boost/serialization/string.hpp> #include <boost/serialization/vector.hpp> #include <boost/serialization/export.hpp> #include <boost/serialization/shared_ptr.hpp> #include <boost/shared_ptr.hpp> #include <boost/make_shared.hpp> #include <iostream> #include <fstream> #include <string> class Distribution { public: Distribution(void) {}; ~Distribution(void) {}; virtual std::string getType() = 0; protected: std::string m_Type; private: friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int version) {}; }; BOOST_SERIALIZATION_ASSUME_ABSTRACT(Distribution) class ContinuousDist : public Distribution { public: ContinuousDist() { m_Type = "Continuous"; m_Location = 80.0; m_Scale = 5.0; m_Shape = 0.0; }; ~ContinuousDist(void) {}; virtual std::string getType() {return m_Type;}; private: double m_Location; double m_Scale; double m_Shape; friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int version) { ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(Distribution) & BOOST_SERIALIZATION_NVP(m_Type) & BOOST_SERIALIZATION_NVP(m_Location) & BOOST_SERIALIZATION_NVP(m_Scale) & BOOST_SERIALIZATION_NVP(m_Shape); }; }; BOOST_CLASS_EXPORT(ContinuousDist); class DiscreteDist : public Distribution { public: DiscreteDist(void) { m_Type = "Discrete"; m_Data.push_back(1.2); m_Data.push_back(2.5); m_PMF.push_back(0.8); m_PMF.push_back(0.2); }; ~DiscreteDist(void){}; virtual std::string getType() {return m_Type;}; private: std::vector<double> m_Data; std::vector<double> m_PMF; friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int version) { ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(Distribution) & BOOST_SERIALIZATION_NVP(m_Type) & BOOST_SERIALIZATION_NVP(m_Data) & BOOST_SERIALIZATION_NVP(m_PMF); }; }; BOOST_CLASS_EXPORT(DiscreteDist); typedef boost::shared_ptr<Distribution> DistributionPtr; class Parameter { public: Parameter() { m_ID = 0; }; Parameter(int id, int type) { m_ID = id; if(type == 1) m_pDist = boost::make_shared<DiscreteDist>(); else m_pDist = boost::make_shared<ContinuousDist>(); }; ~Parameter(void){}; DistributionPtr getDist() {return m_pDist;}; int getID() {return m_ID;}; private: DistributionPtr m_pDist; int m_ID; friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int version) { ar & BOOST_SERIALIZATION_NVP(m_ID) & BOOST_SERIALIZATION_NVP(m_pDist); }; }; typedef boost::shared_ptr<Parameter> ParameterPtr; void load(std::vector<ParameterPtr>& vP, std::string file) { std::ifstream ifs(file.c_str()); boost::archive::xml_iarchive ia(ifs); ia >> BOOST_SERIALIZATION_NVP(vP); } void save(std::vector<ParameterPtr>& vP, std::string file) { std::ofstream ofs(file.c_str()); boost::archive::xml_oarchive oa(ofs); oa << BOOST_SERIALIZATION_NVP(vP); } int main() { // tbe file to read/save from/to std::string file = "archive.xml"; // make some Parmeters std::vector<ParameterPtr> vParam; vParam.push_back( boost::make_shared<Parameter>(1,1) ); vParam.push_back( boost::make_shared<Parameter>(2,2) ); // display for checking for(unsigned int i = 0; i != vParam.size(); ++i) std::cout << "P: " << vParam.at(i)->getDist()->getType() << std::endl; // save the file std::cout << "Writing..." << std::endl; save(vParam,file); // read the file std::cout << "Reading..." << std::endl; load(vParam,file); // display for checking for(unsigned int i = 0; i != vParam.size(); ++i) std::cout << "P: " << vParam.at(i)->getDist()->getType() << std::endl; std::cin.get(); // hold console window open _CrtDumpMemoryLeaks(); // report memory leaks }

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Enums to/from Strings
by John M. Dlugosz 22 Jul '11

22 Jul '11

Any thoughts or pointers on the best way to support rendering and parsing of enumerated constants? Some only need to be printed, as for debug messages. Others need to be parsed as well, such as from a configuration file. I'm thinking the solution should provide for uniform access to the conversion including existing uses such as feeding an enumeration constant to Boost.Format and having it automatically render as the string.

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determine whether the compilation is occuring on mac os
by Sean Farrow 22 Jul '11

22 Jul '11

Hi: I'm writing a cross platform app and need to determine whether I am compiling on windows/mac os. I note there is a windows configuration define in boost.config, but is there an equivalent mac one? Cheers Sean.

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Boost.Iterator runtime assertion with MSVC
by Narinder Claire 22 Jul '11

22 Jul '11

Hello The following piece of code : ____________________ #include<string> #include<map> #include<iostream> #include<iterator> #include<boost/iterator/transform_iterator.hpp> typedef std::map<std::string, int> map; typedef map::const_iterator const_iterator; struct transformer { typedef std::string result_type; const result_type & operator()(const std::pair<const result_type, int> & thePair)const { return thePair.first; } }; typedef boost::transform_iterator<transformer, const_iterator > const_key_iterator; int main() { map m; m["one"]=1; m["two"]=2; const_key_iterator key_iterator(m.begin(),transformer()); // Following 3 lines work fine const std::string &temp = *key_iterator; std::string::const_iterator it_works = temp.begin(); std::cout << *it_works; // Following 2 lines cause crash when // compiled with VS2010 & VS2008 std::string::const_iterator it_fails = key_iterator->begin(); std::cout << *it_fails ; } ________________________________ executes fine when compiled with mingw(gcc 4.5.2) and gcc 4.5.2(Ubuntu 11.04) but crashes when compiled with VS2010 & VS2008. The issue seems to be something about not being allowed to dereference an iterator toa string. Can anyone shed any light on this ? I ensured that language extensions were NOT disabled. Rgds N

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Using thread library in MFC DLL causes assertion failure
by Kean Mariotti 22 Jul '11

22 Jul '11

Hi everybody, I am working on a MFC DLL project with Visual Studio 2010. Since I have started to use the boost thread library in my DLL I get error messages, when from another program I try to dynamically load the DLL. I recreated the problem, apparently the errors occur when from any MFC DLL project is included one header of the thread library (I tried with barrier.hpp, condition_variable.hpp and thread.hpp). Below is shown what the messages look like: 1. Debug assertion failed! Program: ... File: ...\dllinit.cpp Line: 607 2. then I press ignore... 3. Debug assertion failed! Program: ... File: ...\dllmodul.cpp Line: 135 4. then I press ignore and the program correctly goes on with its execution... I have found an older thread in which was explained a very similar issue: http://comments.gmane.org/gmane.comp.lib.boost.user/49747 but apparently nothing has been fixed since that time. I hope somebody has a suggestion.

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boost::units primer needed
by Michael Powell 21 Jul '11

21 Jul '11

Boost Units users, I need to find a *really* good boost::units primer to get me started. we've got some units-based calculations that need to be developed and I hope to make use of boost in order to facilitate those calculations taking place. so far what I am thinking of as a basic type calculation isn't panning out quite right, more likely I am failing to grasp just what I need to do to string together the quantities in accordance with the units framework which allows the calculations to happen properly... I don't know if any of this is making sense. Kind regards, Michael

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[Review] Lockfree review starts today, July 18th
by Hartmut Kaiser 21 Jul '11

21 Jul '11

Hi all, The review of Tim Blechmann's Boost.Lockfree library starts today, July 18th 2011, and will end on July 28th. I really hope to see your vote and your participation in the discussions on the Boost mailing lists! ----------------------------------------------------- About the library: Boost.Lockfree provides implementations of lock-free data structures. Lock-free data structures can be accessed by multiple threads without the necessity of blocking synchronization primitives such as guards. Lock-free data structures can be used in real-time systems, where blocking algorithms may lead to high worst-case execution times, to avoid priority inversion, or to increase the scalability for multi-processor machines. The following data structures are provided: - boost::lockfree::fifo, a lock-free fifo queue - boost::lockfree::stack, a lock-free stack - boost::lockfree::atomic_int, an atomic integer class The library is accessible from here: http://tim.klingt.org/boost_lockfree.tag.gz. Boost.Lockfree depends on C++0x atomics. They are not well supported with current compilers yet. For this reason Boost.Lockfree depends on the *unreviewed* Boost.Atomic library, that emulates C++0x atomics for C++98. This review is about Boost.Lockfree and not about Boost.Atomic, although it is included in the tarball and the git repository. If Boost.Lockfree will be accepted, it won't be merged into trunk before Boost.Atomic is accepted. --------------------------------------------------- Please always state in your review, whether you think the library should be accepted as a Boost library! Additionally please consider giving feedback on the following general topics: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? Regards Hartmut Review Manager

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[Serialization] getting version of items stored in STL collection
by cc caprani 21 Jul '11

21 Jul '11

I'm converting parts of a program to use boost::shared_ptr. I have a vector of pointers to objects std::vector<Object*> which now becomes std::vector<ObjectPtr> where ObjectPtr = make_shared<Object>(). I must support archives (XML files) created previously. Boost::serialization looks after saving STL collections very nicely. However, now, in reading a file, I need to determine the item_version in the collection so I can read in a vector of Object* or ObjectPtr. I also need to change the item_version when saving new files to indicate ObjectPtrs are being saved. I've dug through the documentation and source for hours but can't find anything that I can use (my own limitations perhaps?). This vector is NOT a class member and so class versioning does not apply unfortunately. Also, I am using bespoke load/save functions and NOT the serialize(Archive& ar, const unsigned int version) which would avoid this problem (I posted about this before - due to move from MFC to boost and mix of Doc/View architecture). I realize now I should have put a class version member of the MyAppDoc file structure which would be read in first. This would save all the pain. I've written some functions to interface with the file for the meantime, but I'm sure there must be a better solution: template<class Archive, class T> inline void load_vsp_from_vp(Archive& ar, std::vector<boost::shared_ptr<T>>& vPtr, const char* name) { std::vector<T*> vT; ar & boost::serialization::make_nvp(name, vT); boost::shared_ptr<T> ptr; vPtr.assign(vT.size(), ptr); for(int i = 0; i != vT.size(); ++i) vPtr.at(i).reset( vT.at(i) ); } template<class Archive, class T> inline void save_vp_from_vsp(Archive& ar, std::vector<boost::shared_ptr<T>>& vPtr, const char* name) { std::vector<T*> vT; for(int i = 0; i != vPtr.size(); ++i) vT.push_back( vPtr.at(i).get() ); ar & boost::serialization::make_nvp(name, vT); } Use as: save_vp_from_vsp<boost::archive::xml_oarchive, Object>(oa, m_vObject, "m_vObject"); Any help appreciated.

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