November 2011 - Boost-users

boost::mpl
by Peter Foelsche 12 Nov '11

12 Nov '11

Again -- my thanks to the developers of boost::mpl -- something I'm really use and appreciate a lot! Some requests: 1) I talked already in the past about the value_init stuff used in for_each. I'm not certain which kind of object needs it's memory initialized to zero to work. Anyway -- even in case of pod types the contents of the value does not matter, AS ONLY THE TYPE IS NEEDED to select one or the other template routine. 2) The routine mpl::for_each must be inlined. I got an object file of a size which I've never seen before!!!! And memory usage by the compiler of up to 12GB! And after some examination it turned out, that some routines called by for_each are not inlined. And I did add again (like I did already some time ago and reported here) some __forceinline (the equivalent for g++ is some attribute) to some of the routines in boost/mpl/for_each.hpp Now everything is fine -- the compiler finishes after an appropriate time and things compile again on 32bit. Peter Foelsche

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[ASIO] Flush output on socket
by Claude 12 Nov '11

12 Nov '11

Hi! I use this code for send a std::string with a socket: I have a doubt: this function automatically flush its output? -- View this message in context: http://boost.2283326.n4.nabble.com/ASIO-Flush-output-on-socket-tp3951921p39… Sent from the Boost - Users mailing list archive at Nabble.com.

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boost::ptr_vector::sort with c++11 lambdas
by qplace 12 Nov '11

12 Nov '11

I am trying to figure out if c++11 lambda can be used instead of the straight preducates. say, I have class A : public boost::noncopyable { ... } and boost::ptr_vector<A> lst; I'd like to use something like: lst.sort([&] (const A& v1, const A& v2) ->bool {return v1 < v2;}); Tutorial for ptr_vector says that predicates are wrapped in indirect_fun. May be this is the reason the sort fails to compile?

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Re: [Boost-users] [Spirit-general] Pattern matching with boost
by Anthony Foiani 12 Nov '11

12 Nov '11

Anthony Foiani <tkil(a)scrye.com> wrote: > Have you even tried my code? > > http://article.gmane.org/gmane.comp.lib.boost.user/71262 Seth Heeren <bugs(a)sehe.nl> writes: > FYI: that mail never seems to have arrived at my MUA... Perhaps it > got lost for Alec too? FWIW, the webinterface I sometimes use > doesn't seem to list your post either. I don't know the why's there, > just thought I'd mention. Drat. Thanks for the heads-up. And it seems that your message didn't go out over the boost-users list, either, although it did make it to spirit-general. Weird. Alec, I apologize for the snark in my latest message. When you replied to my later messages, but not to my original reply, I just assumed you had seen it and were ignoring it for some reason. Sorry about that. > Some corner cases to think about: > > 1. ... > B. ... > > +1 many good points! Only a side effect of fixing my own stupid mistakes for many years! Best regards, Tony

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Re: [Boost-users] dynamic_bitset: request for new functions
by David Hochstuhl 12 Nov '11

12 Nov '11

> My apologies if my tone was not friendly, this was not my intention. Hey, there is absolutely no reason why you should apologize... your tone is very friendly...and thank you again for your answer. >Given the current interface I find your requests quite reasonable. >I'm sure that if you provide a patch for the functions you are >suggesting, with documentation and test, the author/maintainer will >accept them. My hope was that the maintainer himself will do it. Writing the code for the find functions and other "easy" ones (like setting a range of bits to true, setting trailing zeros to true, etc) will probably take a few minutes. For me, it will at least take several days, as I first would have to study the source code of the class (although it is not all too long). btw, who is the maintainer of dynamic_bitset? best, David ___________________________________________________________ SMS schreiben mit WEB.DE FreeMail - einfach, schnell und kostenguenstig. Jetzt gleich testen! http://f.web.de/?mc=021192

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[smart_ptr] weak_ptr pointer semantics
by Szymon Gatner 12 Nov '11

12 Nov '11

Hi, Why weak_ptr does not have (smart) pointer semantics? No * or -> or even get(). I often need a pointer type that is a listener to shared_ptr<> (does not affect refcount) but is still usable as a regular pointer type. If providing * and -> operators is for some reason undesirable then just a get() member would be nice as it would allow to implement own wrapper with pointer semantics. get() would return raw pointer from shared counter (so is fast) and not shared_ptr<> as lock() does. -- Szymon Gatner The Lordz Games Studio www.thelordzgamesstudio.com

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[fusion] trouble with transform
by Gennadiy Rozental 11 Nov '11

11 Nov '11

Hi, I have code similar to the following snippet: #include <boost/fusion/container/list/list.hpp> #include <boost/fusion/container/list/convert.hpp> #include <boost/fusion/container/generation/make_list.hpp> #include <boost/fusion/algorithm/transformation/transform.hpp> namespace fusion=boost::fusion; template<typename T> class A { public: struct B {}; B make_b() const { return B(); } }; template<typename T> A<T> make_a( T const& ) { return A<T>(); } struct make_b { template<typename Sig> struct result; template <typename DS> struct result<make_b(DS const&)> { typedef typename DS::B type; }; template <typename T> typename T::B operator()(T const& t) const { return t.make_b(); } }; int main() { namespace fusion=boost::fusion; fusion::as_list( fusion::transform( fusion::make_list( make_a( 1. ), make_a( 1 ) ), make_b() ) ); return 0; } it fails to compile with an error like this: ... rather long context here ..\..\../boost/utility/result_of.hpp:83:1: error: invalid use of incomplete type ‘struct make_b::result<make_b(A<double>)>’ test.cpp:27:35: error: declaration of ‘struct make_b::result<make_b(A<double>)>’ What am I doing wrong? Any help appreciated, Gennadiy

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Re: [Boost-users] dynamic_bitset: request for new functions
by David Hochstuhl 11 Nov '11

11 Nov '11

Hey, thank you for your answer. >For the find features, I would consider to provide a view of a bitset >that behaves as standard set, with iterators. Even if the complexity of >these operations could not conform to the standard one, the advantages >are evident. In the same way you can associate a view of the >complementary set. I don't understand exactly what mean by this. Do you mean one should set up a std::set or something similar from a range of the bitset? >For the bit-twiddling hacks algorithm, the interface is almost ready. >Currently there is the data() function given access to the storage, and >a constructor from it. The problem is that the access is read-only and >the constructor will make a copy. Adding some move functions to extract >the storage and to take an external storage would permit to build every >algorithm you want on top of them in an efficient way. Can you tell me where to find this function. I searched the documentation and the source code, but couldn't find it. >As you said this is a lot and even if this is not complex, this will >need a considerable time to make something with the expected quality. Do >you think that you could contribute in some way? Sure I could, but I don't know whether I could provide the "expected quality". I anyway planned to code at least the LSB/MSB search functions for myself. best, David ___________________________________________________________ SMS schreiben mit WEB.DE FreeMail - einfach, schnell und kostenguenstig. Jetzt gleich testen! http://f.web.de/?mc=021192

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[mpi/serialization] Potential bug or just library misunderstanding?
by Tim Jacobs 10 Nov '11

10 Nov '11

I'm not sure why the following test-class produces this error: "MPI_Recv: MPI_ERR_TRUNCATE: message truncated" If the std::map has only a single element (ie I remove one of the test[].push_back() lines) the error does not occur. Can someone verify that this is indeed a bug and not just novice misuse of the library? Thanks, Tim #include <boost/mpi.hpp> #include <boost/serialization/string.hpp> #include <boost/serialization/vector.hpp> #include <boost/serialization/map.hpp> int main( int argc, char * argv [] ) { boost::mpi::environment env(argc, argv); boost::mpi::communicator world; if(world.rank()==0){ std::map<int, std::vector<std::string> > test; test[1].push_back("FOO"); test[50].push_back("BAR"); world.send(1, 1, boost::mpi::skeleton(test)); world.send(1, 1, boost::mpi::get_content(test)); std::cout << "sent" << std::endl; } else{ std::map<int, std::vector<std::string> > test; world.recv(0,1,boost::mpi::skeleton(test)); world.recv(0,1,boost::mpi::get_content(test)); } }

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dynamic_bitset: request for new functions
by David Hochstuhl 10 Nov '11

10 Nov '11

Hi everybody, is it planned to extend the dynamic_bitset in the near future? I would consider the implementations of the following functions to be particularly useful: find_last(); // position of most significant bit find_previous(size_t pos); // like find next, but in the other direction find_first_not(); // position of first unset bit find_next_not(); //... find_last_not(); //... find_previous_not(); //... further, views would be nice, so that one could act with bitwise operation only on a certain subset of the bitset. and last but not least -- I know that might be beyond the scope of this class -- arithmetics would be nice, so that one could directly copy e.g. the algorithms form bit-twiddling hacks. ( *of course* they should also work on views ^^ ) I know thats a lot, but it would certainly be helpful. Thanks in advance and best regards, David ___________________________________________________________ SMS schreiben mit WEB.DE FreeMail - einfach, schnell und kostenguenstig. Jetzt gleich testen! http://f.web.de/?mc=021192

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