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using bind with find_if
by Dennis Jones 10 Mar '11

10 Mar '11

Hello, I am currently using find_if with bind2nd to perform a search on a vector. My current code looks like this: struct OverrideMatches : public std::binary_function<const TItemOverride, const TItemOverride, bool> { bool operator()( const TItemOverride& OverrideSource, TItemOverride OverrideTarget ) const { return OverrideSource.ChildAssyItemRecNo == OverrideTarget.ChildAssyItemRecNo && OverrideSource.LinkItemRecNo == OverrideTarget.LinkItemRecNo; } }; TItemOverrideGateway::Container_t::iterator where = std::find_if( FOverridesContainer.begin(), FOverridesContainer.end(), std::bind2nd( OverrideMatches(), TItemOverride( "", 0, "", 0, ChildItemRecNo, LinkItemRecNo ) ) ); I would like to eliminate the need for that temporary object to hold the values I am searching for (and just specify the values instead), and to do that, I want to try using boost::bind instead of std::bind2nd, but I have not been able to determing exactly what that syntax would look like. I know I will need placeholders for the values to search on (ChildItemRecNo, LinkItemRecNo), but then how does the element from the vector get passed to the I think I want the functor to look something like this: struct OverrideMatches { bool operator()( const TItemOverride &OverrideSource, const RecNo_t ChildItemRecNo, const RecNo_t LinkItemRecNo ) { return OverrideSource.ChildAssyItemRecNo == ChildItemRecNo && OverrideSource.LinkItemRecNo == LinkItemRecNo; } }; If the above functor is correct (and maybe it's not, in which case, please correct me), how do I then rewrite std::find_if to use it with boost::bind? Thank you very much, Dennis Jones

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function_base.hpp type-punned pointer warnings
by KSpam 10 Mar '11

10 Mar '11

I get a ton of warnings (well over 5000 in the code base I am compiling) from function_base.hpp when compiling with gcc. boost-1.46.0/include/boost/function/function_base.hpp:321: warning: dereferencing type-punned pointer will break strict-aliasing rules boost-1.46.0/include/boost/function/function_base.hpp:325: warning: dereferencing type-punned pointer will break strict-aliasing rules This has been a known problem for a very long time, and the work around is quite simple. Replace reinterpret_cast<functor_type*>(&in_buffer.data)->~Functor(); with functor_type* p = reinterpret_cast<functor_type*>(&in_buffer.data); p->~Functor(); and replace reinterpret_cast<functor_type*>(&out_buffer.data)->~Functor(); with functor_type* p = reinterpret_cast<functor_type*>(&out_buffer.data); p->~Functor(); Would it be a reasonable request to have this simple patch applied to the boost source code? Respectfully, Justin

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min and max preferring NaN
by Rhys Ulerich 10 Mar '11

10 Mar '11

'Afternoon, The usual std::min and std::max prefer numbers over NaNs per http://en.wikipedia.org/wiki/IEEE_754_revision#min_and_max. POSIX's fmin(3) does as well. Can anyone suggest a better implementation (chained ternary complaints aside) for a NaN-preferring min or max than brute force things akin to template<class T> inline const T& minnan(const T& a, const T& b) { return UNLIKELY((boost::math::isnan)(a)) ? a : (a < b) ? a : b; } where UNLIKELY is a small macro telling the compiler to generate code expecting that the boost::math::isnan test fails? The need arises in a numerical simulation where I want to gradually accumulate a global minimum where throwing away NaNs ("windowing" in IEEE 754 revision-speak) is the unacceptable. Thanks, Rhys

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async_read_some/async_write_some
by Marco Piacentini 10 Mar '11

10 Mar '11

Hi...this is my question: are there the concatenation of these functions be considered like a multithread approach on a socket? I try to explain myself better... I need to have a behaviour like the following: inside a process, one thread read over a scoket, and one thread write over the same socket... is it possible to make the same beahviour simply create a chain of async_read and Async_write? or I have to handle the socket with lock-unlock mechanism? thank you...

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Re: [Boost-users] [ASIO] async_accept : Error m_val 1.
by Cyprien DIOT 10 Mar '11

10 Mar '11

Thank you for your answer. You're right, with message member function, I get the "Already open" error. I don't really understand it, my source code is: void Server::receiving() { boost::system::error_code error; tcp::endpoint endp(tcp::v4(), 14242); acceptor = new tcp::acceptor(_io); acceptor->open(endp.protocol()); acceptor->set_option(tcp::acceptor::reuse_address(true)); acceptor->bind(endp); acceptor->listen(); _client = new tcp::socket(_io); _client->close(); acceptor->async_accept(*_client, boost::bind(&ipc::handle_accept, this, boost::asio::placeholders::error)); } What is "already open" ? _client ? It has just been allocated before calling async_accept. _io is properly initialized. If this error is about acceptor, how can I use it with async_accept ? I've seen http://www.boost.org/doc/libs/1_37_0/doc/html/boost_asio/reference/basic_so… but i don't see any line where the listen port is set to acceptor. I'm sorry for my english which is not very good. Thank you ! ----- Mail original ----- De: "Igor R" <boost.lists(a)gmail.com> À: boost-users(a)lists.boost.org Envoyé: Jeudi 10 Mars 2011 00:42:24 Objet: Re: [Boost-users] [ASIO] async_accept : Error m_val 1. > m_val = 1; > m_cat = 0x00ab8d00 instance; > | [boost::asio::error::detail::misc_category] = {...} > | boost::noncopyable_::noncopyable = {...} > | __vfptr = 0x00a8bf18 const boost::asio::error::detail::misc_category::`vftable' Use message() member function of error_code to see the error description. IIUC, in your case it should be "Already open", i.e. you're trying to accept new connection to a socket which was already open. _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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[uBLAS] Predefined subrange or project
by Ryan 10 Mar '11

10 Mar '11

Is it possible to predefine a subrange or project with a specific range so that when called I only had to pass in the matrix? I'm currently dealing with several 9x9 matrices that I need to access the 3x3 submatrix (topleft, topmiddle, topright, etc.). Is there a way to typedef or templatize a subrange or project so that I just need to pass the 9x9 matrix and get the topleft matrix? Example: typedef subrange(input_matrix, 0, 3, 0, 3) topleft; //This is what I want to somehow define. matrix<double> A(9,9); topleft(A) = zero_matrix<double>(3,3); Ryan

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Re: [Boost-users] [ASIO] async_accept : Error m_val 1.
by Cyprien DIOT 10 Mar '11

10 Mar '11

I've made unit test for this problem. Server.h: #pragma once #include <boost/thread/thread.hpp> #include <boost/asio.hpp> #include <boost/array.hpp> #include <iostream> class Server { public: AssistGui(boost::asio::io_service &); ~AssistGui(void); void accept(const boost::system::error_code& e); void sendMsg(const char *msg, unsigned int size); private: boost::asio::io_service &io; boost::asio::ip::tcp::socket _client; boost::asio::ip::tcp::acceptor _acceptor; }; Server.cpp: #include "Server.h" using boost::asio::ip::tcp; Server::Server(boost::asio::io_service &ios) : io(ios), _client(ios), _acceptor(ios, tcp::endpoint(tcp::v4(), 14242)) { _acceptor.async_accept(_client, boost::bind(&Server::accept, this, boost::asio::placeholders::error)); } void Server::sendMsg(const char *msg, unsigned int size) { } Server::~Server(void) { } void Server::accept(const boost::system::error_code& e) { // same error :-( : "Already open" } int main() { boost::asio::io_service ios; Server s(ios); ios.run(); } The error is still the same "Already open". _WIN32_WINNT=0x0501 is defined. I tried to change port. No warnings at program compilation. Can you help me? Thank you Cyprien DIOT ----- Mail original ----- De: "Igor R" <boost.lists(a)gmail.com> À: boost-users(a)lists.boost.org Envoyé: Jeudi 10 Mars 2011 00:42:24 Objet: Re: [Boost-users] [ASIO] async_accept : Error m_val 1. > m_val = 1; > m_cat = 0x00ab8d00 instance; > | [boost::asio::error::detail::misc_category] = {...} > | boost::noncopyable_::noncopyable = {...} > | __vfptr = 0x00a8bf18 const boost::asio::error::detail::misc_category::`vftable' Use message() member function of error_code to see the error description. IIUC, in your case it should be "Already open", i.e. you're trying to accept new connection to a socket which was already open. _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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[Boost] [Interprocess] Use of Boost.Move in interprocess affecting causing compilation errors with 1.46
by Lars Hagstrom 10 Mar '11

10 Mar '11

Hi all, I'm having a problem compiling some code with boost 1.46 that was compiling fine with 1.36 to 1.43 (or thereabouts). It appears that this is somewhat related to the use of Boost.Move in the Boost.Interprocess library. I have tried to read up a bit on Boost.Move, but have failed to quite understand what of it applies to me. Here is a small piece of code that will cause the compilation error (explanations below): ---------------------- #include <boost/interprocess/ containers/vector.hpp> #include <boost/interprocess/containers/string.hpp> #include <boost/interprocess/managed_shared_memory.hpp> typedef boost::interprocess::basic_string < char, std::char_traits<char>, boost::interprocess::allocator < char, boost::interprocess::managed_shared_memory::segment_manager > > ShmString; class A { #if 0 public: A(const A&); A& operator=(const A&); #endif private: #if 1 ShmString m_name; #endif }; typedef boost::interprocess::vector < A, boost::interprocess::allocator < A, boost::interprocess::managed_shared_memory::segment_manager > > AVector; class B { public: void AddA(const A & a) {m_as.push_back(a);} private: AVector m_as; }; ---------------- g++ 4.4 compilation errors: ---------------- In file included from /usr/include/c++/4.4/memory:49, from /home/lars/boost_1_46_0/boost/interprocess/containers/container/vector.hpp:23, from /home/lars/boost_1_46_0/boost/interprocess/containers/vector.hpp:19, from mfp.cpp:1: /usr/include/c++/4.4/bits/stl_algobase.h: In static member function ‘static _OI std::__copy_move<false, false, std::random_access_iterator_tag>::__copy_m(_II, _II, _OI) [with _II = boost::container::constant_iterator<A, long int>, _OI = A*]’: /usr/include/c++/4.4/bits/stl_algobase.h:397: instantiated from ‘_OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove = false, _II = boost::container::constant_iterator<A, long int>, _OI = A*]’ /usr/include/c++/4.4/bits/stl_algobase.h:436: instantiated from ‘_OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove = false, _II = boost::container::constant_iterator<A, long int>, _OI = A*]’ /usr/include/c++/4.4/bits/stl_algobase.h:468: instantiated from ‘_OI std::copy(_II, _II, _OI) [with _II = boost::container::constant_iterator<A, long int>, _OI = A*]’ /home/lars/boost_1_46_0/boost/interprocess/detail/move.hpp:1105: instantiated from ‘F boost::interprocess::copy_or_move(I, I, F, typename boost::disable_if<boost::interprocess::move_detail::is_move_iterator<I>, void>::type*) [with I = boost::container::constant_iterator<A, long int>, F = A*]’ /home/lars/boost_1_46_0/boost/interprocess/containers/container/detail/advanced_insert_int.hpp:53: instantiated from ‘void boost::container::containers_detail::advanced_insert_aux_proxy<T, FwdIt, Iterator>::copy_all_to(Iterator) [with T = A, FwdIt = boost::container::constant_iterator<A, long int>, Iterator = A*]’ mfp.cpp:46: instantiated from here /usr/include/c++/4.4/bits/stl_algobase.h:343: error: no match for ‘operator=’ in ‘* __result = __first.boost::container::constant_iterator<T, Difference>::operator* [with T = A, Difference = long int]()’ mfp.cpp:17: note: candidates are: A& A::operator=(A&) Which may not say too much, but if I change either the #if 0 to #if 1 or the #if 1 to #if 0 it suddenly compiles. So I'm thinking that the use of BOOST_MOVE_MACRO_COPYABLE_AND_MOVABLE(basic_string) in the interprocess string is somehow causing me to have to implement copy constructors and copy assignment operators in all classes that use them. Is this the way it is meant to be? I was fine with the compiler-generated ones before... Cheers Lars

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[lambda] How to write a lambda functor that returns a new functor
by Sebastian Theophil 10 Mar '11

10 Mar '11

Hi, How can I write a lambda expression with two placeholders, one for the callable object, and one for the function argument, such that supplying the callable object first returns a unary function? In the example below, generate should be a lambda expression with the first placeholder for the callable object itself, and the second placeholder for the argument. Calling generate(c) should return a unary function that is only missing the function call argument. In fact, it somehow returns type bool already, as proved by the static assert. #include <boost/lambda/bind.hpp> struct Arg { }; struct Callable : std::unary_function<Arg, bool> { bool operator()( Arg const& a ) const { return true; } }; int main( int argc, const char* argv[] ) { BOOST_AUTO(generate, boost::lambda::bind(boost::lambda::_1, boost::lambda::protect(boost::lambda::_1))); Callable c; BOOST_AUTO(fn, generate(c)); BOOST_STATIC_ASSERT((boost::is_same<BOOST_TYPEOF(fn), bool>::value)); Arg a; bool b = fn(a); _ASSERT(b==true); } Thanks, Sebastian -- Sebastian Theophil | stheophil(a)think-cell.com Senior Software Engineer think-cell Software GmbH | Chausseestr. 8/E | 10115 Berlin | Germany http://www.think-cell.com | phone +49 30 666473-10 | US phone +1 800 891 8091 Amtsgericht Berlin-Charlottenburg, HRB 85229 | European Union VAT Id DE813474306 Directors: Dr. Markus Hannebauer, Dr. Arno Schoedl

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boost::asio multiprocess
by Marco Piacentini 10 Mar '11

10 Mar '11

Hi guys...I would to make a simple multi process (not thread) server. I've seen the iterative example in which it handles one request at a time. Instead I need to handle more requests(more on less 10) at the same time. In the classic c and c++ examples, I've seen that the server is designed like the following: int listensd, connsd; // listening socket and conection socket pid_t pid; //process id listensd=socket(....); bind(listensd,...); listen(listensd,...); for(;;) { connsd=accept(listensd,...); if((pid=fork())==0) //child process { close(listensd); //close the listen socket do_it(connsd); //serve the request close(connsd); //close the connection socket exit(0); } close(connsd); //the parent closes the connection socket } Is it possible to do something like that with boost? I really don't know how obtain the two different socket, because in boost all the function (listen, bind, accept, etc.) return void. Thank you...

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