July 2009 - Boost-users - lists.preview.boost.org

Binding operator <<
by Archie14 11 Jul '09

11 Jul '09

Can't figure out the proper sintax for binding <<. class A { public: friend std::ostream& operator << (std::ostream& stream, A& a); }; class B : boost::ptr_vector<A> { public: friend std::ostream& operator << (std::ostream& stream, B& b); } std::ostream& operator << (std::ostream& stream, B& b) { std::for_each(begin(), end(), boost::bind(&operator<<, ref(stream), ref(_1)); ??? return stream; }

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Re: [Boost-users] boost programmer_option.hpp
by Narendra R 11 Jul '09

11 Jul '09

hi Markus , Steeps i have done is 1. downloaded boost library boost_1_39_0 2. build the program.option using bootstrap.sh --without-libraries=program_options --libdir=/home/narendra/boost_instal/boost_1_39_0/b_lib_ins where /home/narendra/boost_instal is the directory where i have stored boost library I tried to link like this g++ -I /home/narendra/boost_instal/boost_1_39_0 test.cpp -o test -L /home/narendra/boost_instal/boost_1_39_0/stage/lib -l/home/narendra/boost_instal/boost_1_39_0/stage/lib/libboost_program_options-gcc41-mt-1_39.a

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[Program Options] Difficulty compiling for static runtime library
by Lindley M French 11 Jul '09

11 Jul '09

I have a large project that I'd like to use Boost.Program Options with. Most of the other Visual Studio 2005 projects are set to link against "Multithreaded" or "Multithreaded Debug" rather than the DLL variants of same; so of course, I need to build Program Options accordingly. I tried this: bjam.exe" release --runtime-link=static program_options But that did not produce the library that VS wants, which is: libboost_program_options-vc80-mt-s-1_39.lib Actually, that build setting caused program_options to throw a massive number of warnings, mostly stuff like: .\boost/program_options/detail/cmdline.hpp(128) : warning C4251: 'boost::program_options::detail::cmdline::m_style_parser' : class 'boost::function1 ,T0>' needs to have dll-interface to be used by clients of class 'boost::program_options::detail::cmdline' with [ R=std::vector<boost::program_options::option>, T0=std::vector<std::string> & ] and also .\boost/program_options/errors.hpp(21) : warning C4275: non dll-interface class 'std::logic_error' used as base for dll-interface class 'boost::prog m_options::error' C:\Program Files (x86)\Microsoft Visual Studio 8\VC\INCLUDE\stdexcept(22) : see declaration of 'std::logic_error' .\boost/program_options/errors.hpp(21) : see declaration of 'boost::program_options::error' Any ideas?

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re gularized gamma incomplete function (v 1.39)
by darthshak 10 Jul '09

10 Jul '09

I am using boost v1.39 libraries on Ubuntu 9.04. This is the first time I am using the boost libraries for some mathematical work. I needed to use the regularized incomplete gamma function for one of my programs. The documentation told me that gamma_q was the upper incomplete gamma function for the job. So I tried the syntax gamma_q(a,b) and I got an error saying "gamma_q was not declared in this scope". Realizing that the boost libraries were in /opt/boost, I compiled with the following : g++ ggpdf.cpp -I /opt/boost/include/boost-1_39/ I included the boost header with a #include<boost/math/special_functions/gamma.hpp>. I stil got the same error (gamma_q was not declared in scope). I then thought that I should link the libraries manually and then tried g++ ggcdf.cpp -I /opt/boost/include/boost-1_39/ -L /opt/boost/lib/ ...and still no luck. Also, the size of my /opt/boost folder is only 65M, which seems kind of small. Am I missing some incantation here for compiling or is it just an incomplete install? -- View this message in context: http://www.nabble.com/regularized-gamma-incomplete-function-%28v-1.39%29-tp… Sent from the Boost - Users mailing list archive at Nabble.com.

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newbie weighted edges question
by Fahad Saeed 10 Jul '09

10 Jul '09

Hello everyone, I am new at using Boost libraries and was hoping that someone could give me some pointers how to start.The problem that I want to solve is as follows: I want to build a directed graph model with edges that are weighted.But instead of having one weight each edge is suppose to have 2 weights, each representing a different parameter in my graph model.The weights are to be used separately for different functions. Also, this is trivial but a pointer would certainly help. I would like to take each vertice in the graph and ¨know¨ its immediate neighbours. Thanks in advance. Fahad

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[mpl] Any mpl tricks to use default tags and get around function template argument deduction with function defaults?
by jesseperla 10 Jul '09

10 Jul '09

I am building a make_ function for a complicated type with many generic parameters that all have defaults. I believe the following doesn't work in C++03 (but might in C++0X?) template<class T> void myfunc(T t = default_type()) {} if called with no arguments. Here is pseudocode for what I would like to do (unworking, so please bear with any mpl mistakes) struct default_tag{}; struct default_type // metafunction to return the default type to keep it centralized. { typedef int type; type construct() //A construction function? { return type(); } }; template<class T> class myclass { myclass(const T& t){....} //Requires a type }; template<class T> myclass< mpl::if_<mpl::is_same<T, default_tag>, //returns a my_class<> default_type, //call this metafunction if default T > //otherwise pass it in. > make_myclass(const T& t = default_tag()) //Note use of the default_tag { typename myclass< mpl::if_<mpl::is_same<T, default_tag>, default_type, //call this metafunction T >::type resolved_type; //this is what we want to use //Here I am confused of how to conditionally construct a type of default_type::type to pass in? // I thought it might help to have a default_type.construct function but wasn't sure what to do? //Note that T is often too large to do a full 'copy'. It won't be an int. //Pass in t directly or a constructed version of resolved_type if T if 'default'? return my_class<resolved_type>( ...); } The usage I would like to enable: auto m1 = make_myclass(); //Uses the default auto m2 = make_myclass( default_tag() ); //Uses the default as well. Why do I need this? Will actually have a number of these tags where you may want to conditionally choose some as defaults. int n = 5; auto m3 = make_myclass(n); Any ideas on the best idioms to support this and get around the template argument detection problems? Is this possible? If not, can I drop the need for the make_myclass(); usage and still keep the ability to call with a default and conditionally constructs the default object based ont eh type of a metafunction? Thanks, Jesse

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Re: [Boost-users] [optional] How to make boost::optional throw if trying to access uninitialized value
by Anders Dalvander 10 Jul '09

10 Jul '09

dariomt(a)gmail.com wrote: > Thanks for the info! > > I think it is not possible to have a specific boost::assertion_failed handler > for boost::optional and other handlers for other assertion failures in other > places, right? > > That would mean that the exception I throw from the handler cannot mention the > fact that I am accessing an uninitialized value in a boost::optional. > > Maybe I should create my own my::safe_optional based on boost::optional but > checking for uninitialized access. > > Any ideas? > You could create your own functions for this: template <typename T> T const& safe_get(boost::optional<T> const& opt) { if (!opt) throw some_exception(); return *opt; } template <typename T> T& safe_get(boost::optional<T>& opt) { if (!opt) throw some_exception(); return *opt; } Regards, Anders Dalvander

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boost::asio::async_read_until composite completion condition
by Etienne Philip Pretorius 10 Jul '09

10 Jul '09

Hello List, I need to implement a completion condition for boost::asio::async_read_until where either a boost::regex is matched or boost::asio::transfer_at_least is matched. Any suggestions will be much appreciated. Kindly, Etienne

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A question on data change with lambda expression. Can any one with kindness help me?
by fmingu 10 Jul '09

10 Jul '09

I am using Dev-C++ and lambda expression.I wrote the following lines: .................. typedef std::map<int, int> IIPrimemap; IIPrimemap primemapvec; ..................... void a(){ primemapvec[1]=3; bind(&IIPrimemap::value_type::second,(*bind(static_cast<IIPrimemap::iterator (IIPrimemap::*)()> (&IIPrimemap::end),var(primemapvec))))++; return; } .................... but after the program ran, the primemapvec[1] is still 3, not 4. I am puzzled about that. How can I change primemapvec to 4 ? Can anyone with kindness help me?

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[Thread] (Newb) shared memory in multithread process
by gabe_rosser 10 Jul '09

10 Jul '09

Dear All, Apologies for my ignorance but I would be extremely grateful if someone would kindly point me in the right direction. I am trying to parallelize my Monte Carlo simulation. The bottleneck in the process is the generation of Normally distributed random numbers (using boost.random libraries), so I was hoping to substantially improve the efficiency of the process by setting 2 or 3 cores of my quad core processor to the the task of generating these numbers while one core gets on with the rest of the algorithm. The simplest way I can envisage doing this is by allocating shared memory that is simultaneously written (by rand number generating threads) and read (by main thread), with some method of ensuring that the main thread doesn't read too far ahead (perhaps locking or just a simple while loop?). Boost.thread alone doesn't seem to be enough - an attempt to do exactly this resulted in a substantial slow down (with or without locking - without may result in undefined behaviour but I tried it anyway to see if it was causing the slowdown). Do I need to investigate shared pointers? I really need some large container in shared memory which I can fill in any order, much as would be the case if I were appending to and reading from a file, but hopefully faster! Any suggestions please? Sorry for the lack of understanding! Thanks, Gabe -- View this message in context: http://www.nabble.com/-Thread--%28Newb%29-shared-memory-in-multithread-proc… Sent from the Boost - Users mailing list archive at Nabble.com.

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