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JSON and ptree questions
by Gustaf Johansson 05 Feb '10

05 Feb '10

Hi, I've been using the JSON writer with the property_tree. I find it difficult to write lists, since ptree::add does not allow empty paths, and that is required for the json writer to write lists. I have experimentally commented out two asserts, namely line 851, ptree_implementation.hpp: "assert(!p.empty() && "Empty path not allowed for put_child.");" line 200, string_path.hpp: "assert(!empty() && "Reducing empty path");" This is the only way that I've found to correctly write JSON lists in debug mode. Is there any way to do this without the trouble of commenting out the lines above? If not, would it not be a good thing to consider some other way to handle lists in the lib? / Gustaf

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Ref: large data sets and BOOST_FOREACH / boost:bind don't mix ?
by Avi Bahra 05 Feb '10

05 Feb '10

You guys were right, I forgot that it was debug release when run in release mode, I get: Time: BOOST_FOREACH(Fred& fred, vec) { fred.inc(); } 0.28 Time: std::for_each(vec.begin(),vec.end(),boost::bind(&Fred::inc,_1) ); 0.56 Time: for (std::vector<Fred>::iterator i = vec.begin(); i < theEnd ; i++) { (*i).inc(); } 0.27 Time: std::for_each(vec.begin();vec.end(),std::mem_fun_ref(&Fred::inc)) 0.6 Time: for (size_t i = 0; i < theSize ; i++) { vec[i].inc(); } 0.27 Best regards, Ta, Avi

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Re: [Boost-users] large data sets and BOOST_FOREACH / boost:bind don'tmix ?
by pete＠pcbartlett.com 05 Feb '10

05 Feb '10

>[Comparison of loops] >I get following times when run on suse linux with gcc 4.2.1/ boost 1.39 I'm sorry - I totally failed to read your post properly where you state you are using GCC. My apologies. In this case, I, like Roman, suspect the optimization settings are not right.

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declaration does not declare anything - exception
by Dirk Griffioen 05 Feb '10

05 Feb '10

Hi, When I compile with Xcode I get a 'declaration does not declare anything' error on boost/exception/diagnostic_information.hpp. However, the exception test run fine when I compile with bjam --toolset=darwin ... I am quite sure both use the same compiler (g++-4.0.1) and have the same options (I copied from the bjam set to Xcode). I now outcommented it (see below), but this is not a permanent solution. It should be valid, so what am I doing wrong regarding Xcode? Any help would be very much appreciated! Best, Dirk template <class T> struct enable_boost_exception_overload { struct yes { char q[100]; }; typedef char no; //static yes check(exception const *); //static no check(...); enum e { value=sizeof(/*check*/((T*)0))==sizeof(yes) }; }; template <class T> struct enable_std_exception_overload { struct yes { char q[100]; }; typedef char no; //static yes check(std::exception const *); //static no check(...); enum e { value = !enable_boost_exception_overload<T>::value && sizeof(/*check*/((T*)0))==sizeof(yes) }; };

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[future] Getting type of the future result
by Pavel Shevaev 05 Feb '10

05 Feb '10

Folks, please correct me if I'm wrong but currently it's not possible to get the type of the future result. There is a 'reference' typedef both in unique_future and shared_future classes but it's not public... -- Best regards, Pavel

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Re: [Boost-users] large data sets and BOOST_FOREACH / boost:bind don'tmix ?
by pete＠pcbartlett.com 05 Feb '10

05 Feb '10

I would hazard a guess that you are using MSVC with _SECURE_SCL left as the default ON. Here are my results with _SECURE_SCL on: Time: BOOST_FOREACH(Fred& fred, vec) { fred.inc(); } 1.406 Time: std::for_each(vec.begin(),vec.end(),boost::bind(&Fred::inc,_1) ); 0.515 Time: for (std::vector::iterator i = vec.begin(); i < theEnd ; i++) { (*i).inc(); } 1.313 Time: std::for_each(vec.begin();vec.end(),std::mem_fun_ref(&Fred::inc)) 0.516 Time: for (size_t i = 0; i < theSize ; i++) { vec[i].inc(); } 0.391 And with _SECURE_SCL off: Time: BOOST_FOREACH(Fred& fred, vec) { fred.inc(); } 0.36 Time: std::for_each(vec.begin(),vec.end(),boost::bind(&Fred::inc,_1) ); 0.515 Time: for (std::vector::iterator i = vec.begin(); i < theEnd ; i++) { (*i).inc(); } 0.344 Time: std::for_each(vec.begin();vec.end(),std::mem_fun_ref(&Fred::inc)) 0.516 Time: for (size_t i = 0; i < theSize ; i++) { vec[i].inc(); } 0.375 BODY { font-family:Arial, Helvetica, sans-serif;font-size:12px; }So you can see that going through a function pointer has an abstraction penalty - but this is basically the same whether it be through bind or std::mem_fun_ref (haven't checked but assume they compile to same optimized code) Iterators are faster than indexes if _SECURE_SCL is off and slower if it is on - no new news here. ForEach has a small penalty over iterators, but is rare that this matters. Pete On Fri 05/02/10 15:13 , Avi Bahra wrote: In my application I have very large data sets, I was using BOOST_FOREACH and boost bind. But I was surprised that performance wise they were the worst ? Take the following test: class Fred { public: Fred(int i = 0) : i_(i) {} void inc() { i_++;} private: int i_; }; BOOST_AUTO_TEST_CASE( test_loop ) { size_t vecSize = 200000000; std::vector vec; vec.reserve(vecSize); for (size_t i = 0; i < vecSize ; i++) { vec.push_back(Fred(i));} boost::timer timer; BOOST_FOREACH(Fred& fred, vec) { fred.inc(); } cout

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large data sets and BOOST_FOREACH / boost:bind don't mix ?
by Avi Bahra 05 Feb '10

05 Feb '10

In my application I have very large data sets, I was using BOOST_FOREACH and boost bind. But I was surprised that performance wise they were the worst ? Take the following test: class Fred { public: Fred(int i = 0) : i_(i) {} void inc() { i_++;} private: int i_; }; BOOST_AUTO_TEST_CASE( test_loop ) { size_t vecSize = 200000000; std::vector<Fred> vec; vec.reserve(vecSize); for (size_t i = 0; i < vecSize ; i++) { vec.push_back(Fred(i));} boost::timer timer; BOOST_FOREACH(Fred& fred, vec) { fred.inc(); } cout << "Time: BOOST_FOREACH(Fred& fred, vec) { fred.inc(); } " << timer.elapsed() << "\n"; timer.restart(); std::for_each(vec.begin(),vec.end(),boost::bind(&Fred::inc,_1) ); cout << "Time: std::for_each(vec.begin(),vec.end(),boost::bind(&Fred::inc,_1) ); " << timer.elapsed() << "\n"; timer.restart(); std::vector<Fred>::iterator theEnd = vec.end(); for (std::vector<Fred>::iterator i = vec.begin(); i < theEnd ; i++) { (*i).inc(); } cout << "Time: for (std::vector<Fred>::iterator i = vec.begin(); i < theEnd ; i++) { (*i).inc(); } " << timer.elapsed() << "\n"; timer.restart(); std::for_each(vec.begin(),vec.end(),std::mem_fun_ref(&Fred::inc) ); cout << "Time: std::for_each(vec.begin();vec.end(),std::mem_fun_ref(&Fred::inc)) " << timer.elapsed() << "\n"; timer.restart(); size_t theSize = vec.size(); for (size_t i = 0; i < theSize ; i++) { vec[i].inc(); } cout << "Time: for (size_t i = 0; i < theSize ; i++) { vec[i].inc(); } " << timer.elapsed() << "\n"; } I get following times when run on suse linux with gcc 4.2.1/ boost 1.39 Time: BOOST_FOREACH(Fred& fred, vec) { fred.inc(); } 10.65 Time: std::for_each(vec.begin(),vec.end(),boost::bind(&Fred::inc,_1) ); 9.76 Time: for (std::vector<Fred>::iterator i = vec.begin(); i < theEnd ; i++) { (*i).inc(); } 4.48 Time: std::for_each(vec.begin();vec.end(),std::mem_fun_ref(&Fred::inc)) 4.08 Time: for (size_t i = 0; i < theSize ; i++) { vec[i].inc(); } 1.6 It appears that BOOST_FOREACH and use of boost::bind in performance critical application should be avoided ? -- Best regards, Ta, Avi

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Problem with Interprocess Synchronization MUTEX
by Daniel Veneros 05 Feb '10

05 Feb '10

Hi, I have a problem, I need to access a shared memory segment from several process and all at the same time. I was looking at boost::interprocess threads but I'm not sure how to implement the mutex. this is the code I have(working): #include <boost/interprocess/managed_shared_memory.hpp> #include <boost/interprocess/containers/vector.hpp> #include <boost/interprocess/containers/string.hpp> #include <boost/interprocess/containers/map.hpp> #include <boost/interprocess/allocators/allocator.hpp> #include <cstdlib> #include <string> #include <iostream> #include <map> #include <sstream> using namespace boost::interprocess; typedef managed_shared_memory::segment_manager SegmentManager; typedef allocator<void, SegmentManager> VoidAllocator; typedef allocator<char, SegmentManager> CharAllocator; typedef basic_string<char, std::char_traits<char>, CharAllocator> BasicString; class Action { int id; BasicString task; public: Action(int num, const char *name, const VoidAllocator &void_alloc) :id(num), task(name,void_alloc) {} void setId(int num); void setTask(BasicString newTask); int getId(); }; int Action::getId() { return id; } void Action::setId(int num) { id = num; } void Action::setTask(BasicString newTask) { task = newTask; } typedef allocator<Action, SegmentManager> ActionAllocator; typedef std::pair<const BasicString, Action> MapValueType; typedef std::pair<BasicString, Action> MovableToMapValueType; typedef allocator<MapValueType, SegmentManager> MapValueTypeAllocator; typedef map<BasicString, Action, std::less<BasicString>, MapValueTypeAllocator> MyMap; void CreateAndFill() { managed_shared_memory segment(create_only, "MySharedMemory", 65536); VoidAllocator alloc_inst(segment.get_segment_manager()); MyMap *myMap = segment.construct<MyMap>("Map" )(std::less<BasicString>(),alloc_inst); std::string keyword; std::string helper; int i=0; for(int adder = 0; adder<=1000; adder++) { keyword = "Hello"; std::stringstream out; out << adder; helper = out.str(); keyword = keyword + helper;//Creates a string "Hello" + adder BasicString key(keyword.c_str(), alloc_inst);//string to BasicString Action action(i,"ActionContent", alloc_inst);//puts values of Action object MapValueType value(key, action); myMap->insert(value); i++; } } int main(int argc, char** argv) { //Remove shared memory on construction and destruction struct shm_remove { shm_remove() {shared_memory_object::remove("MySharedMemory"); } ~shm_remove() {shared_memory_object::remove("MySharedMemory"); } }remover; CreateAndFill(); } How and where do I have to set the mutex?? Is this anonymous or named? Thanks! Dann

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[StateChart] Inheriting state
by Igor R 05 Feb '10

05 Feb '10

Hello, I'd like to share some functionality between states belonging to different (but similar) FSMs. I try to do this by taking out some part of a state to a base class template: template<class Derived, class Outer, class Inner> struct ActiveBase : state<Derived, Outer, Inner> { // this's probably not quite standard, but it should be fine with msvc ActiveBase(my_context ctx) : my_base(ctx) {} void f(const Event1 &) {} }; struct Active; struct FSM : asynchronous_state_machine<FSM, Active> { //... }; struct Active : ActiveBase<Active, FSM, Disconnected> { Active(my_context ctx) : ActiveBase(ctx) {} typedef mpl::list < sc::in_state_reaction<Event1, ActiveBase, &ActiveBase::f> > reactions; }; However, this doesn't compile: 1>..\boost/statechart/state_machine.hpp(493) : error C2440: 'return' : cannot convert from 'FSM' to 'ActiveBase<Derived,Outer,Inner> &' 1> with 1> [ 1> Derived=Active, 1> Outer=FSM, 1> Inner=boost::mpl::list<Disconnected> 1> ] 1> ../boost/statechart/simple_state.hpp(684) : see reference to function template instantiation 'Context &boost::statechart::state_machine<MostDerived,InitialState,Allocator,ExceptionTranslator>::context<OtherContext>(void)' being compiled 1> with 1> [ 1> Context=ActiveBase<Active,FSM,boost::mpl::list<Disconnected>>, 1> MostDerived=FSM, 1> InitialState=Active, 1> Allocator=std::allocator<void>, 1> ExceptionTranslator=boost::statechart::null_exception_translator, 1> OtherContext=ActiveBase<Active,FSM,boost::mpl::list<Disconnected>> 1> ] etc........ Of course, the above snippet is not the real code, and maybe I miss the problem in some other place, but I just would like to know if the above approach legitimate and *should* compile. Thanks.

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Multicast Dual NIC Receive Problem
by Andy Couldrake 05 Feb '10

05 Feb '10

As a newbie to Boost asio, can please I ask for some guidance on the following problem (which does seem to get a mention from time to time on the boost lists). On a dual NIC Linux server, I am unable to get the sample boost asio multicast receiver ( http://www.boost.org/doc/libs/1_41_0/doc/html/boost_asio/example/multicast/…) to receive packets. It does work fine on a single NIC workstation running the same version of Linux by specify 0.0.0.0 as the listen address, but when I specify the listen address of the correct card on the dual NIC server (A.B.C.D), I get nothing. I have also tried the following but no luck: boost::asio::ip::multicast::join_group joinRequest(multicast_address.to_v4(), listen_address.to_v4()); socket_.set_option(joinRequest); As a sanity check: mtools mdump (http://www.29west.com/news/mtools/) shows that multicast data is coming through ok on the dual NIC server on the NIC listenaddress (A.B.C.D) eg ./mdump <groupaddress> <port> <listenaddress>. It would be nice if we could get the sample code corrected and working! I volunteer to help achieve this ... Regards, Andy

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Re: [Boost-users] [Serialization] Speedding up client-server communication
by Brian Wood 05 Feb '10

05 Feb '10

Ruediger Berlich writes: > Hi there, > > I am in the process of speeding up communication between a server and its > clients. Communication involves serialized class data. Messages can be as > large as 100 kilobytes. > I have done some measurements which have shown that, in a cluster with > Gigabit networking, most overhead of the parallelisation seems to come from > the Broker infrastructure and the process of (de-)serialization. Network > latency and/or bandwidth seems to play only a minor role in this > environment. > Hence, apart from optimizing my broker, I'm looking for ways to optimize the > serialization process, as used in my application. As messages are discarded > as soon as they reach the recipient, versions of serialized data do not play > an important role. I don't find any mention of "message" in the 1.42 Boost Serialization documentation. Are you using MPI? The obvious thing you've not mentioned is compression. I use bzip2 to compress and decompress data - http://webEbenezer.net/misc/SendCompressedBuffer.hh http://webEbenezer.net/misc/ReceiveCompressedBuffer.hh Besides using bzip2, I use variable-length integers to encode the size of the compressed data. It works to use a fixed-size integer as well, but frequently you can shave a couple of bytes off the total by using a variable-length integer. Brian Wood http://webEbenezer.net (651) 251-9384 "The kingdom of heaven is like a treasure hidden in the field, which a man found and hid again; and from joy over it he goes and sells all that he has and buys that field."

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problem with browsing html documentation under w3m
by Michal 04 Feb '10

04 Feb '10

Hallo Group Members there is one page that causes problems under w3m: http://www.boost.org/doc/libs/1_39_0/libs/range/doc/range.html <link href="style.css" rel="stylesheet" type="text/css"><link href="/favicon.ico" rel="icon" type="image/ico"><link href="/style/section-basic.css" rel="stylesheet" type="text/css"><pre_int><img_alt src="../../../boost.png" hseq="1">[boost] </img_alt></pre_int> Boost.Range Range concepts <_SYMBOL TYPE=32>•</_SYMBOL> Overview <_SYMBOL TYPE=32>•</_SYMBOL> Single Pass Range <_SYMBOL TYPE=32>•</_SYMBOL> Forward Range <_SYMBOL TYPE=32>•</_SYMBOL> Bidirectional Range <_SYMBOL TYPE=32>•</_SYMBOL> Random Access Range <_SYMBOL TYPE=32>•</_SYMBOL> Concept Checking <nobr><_SYMBOL TYPE=26>━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━</_SYMBOL> </nobr> Overview A Range is a concept similar to the STL Container concept. A Range provides iterators for accessing a half-open range [first,one_past_last) of elements and provides information about the number of elements in the Range. However, a Range has much fewer requirements than a Container. The motivation for the Range concept is that there are many useful Container-like types that do not meet the full requirements of Container, and many algorithms that can be written with this reduced set of requirements. In particular, a Range does not necessarily <_SYMBOL TYPE=32>•</_SYMBOL> own the elements that can be accessed through it, <_SYMBOL TYPE=32>•</_SYMBOL> have copy semantics, best regards, Michal

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PP: 2 to the power x macro
by Hicham Mouline 04 Feb '10

04 Feb '10

Hello, I have written this code to return 2 to the power x. #include <boost/preprocessor/repetition/for.hpp> #include <boost/preprocessor/seq/size.hpp> #include <boost/preprocessor/arithmetic/add.hpp> #include <boost/preprocessor/arithmetic/sub.hpp> #include <boost/preprocessor/arithmetic/mul.hpp> #include <boost/preprocessor/tuple/elem.hpp> #include <boost/preprocessor/seq/elem.hpp> #define PRED(r,state) BOOST_PP_TUPLE_ELEM(2, 1, state) #define OP(r,state) (BOOST_PP_MUL(BOOST_PP_TUPLE_ELEM(2, 0, state), 2), BOOST_PP_SUB(BOOST_PP_TUPLE_ELEM(2, 1, state), 1)) #define MACRO(r,state) (state) #define POWERSEQ(x) BOOST_PP_FOR((2,x), PRED, OP, MACRO) #define LAST_TUPLE(x) BOOST_PP_SEQ_ELEM(BOOST_PP_SUB(BOOST_PP_SEQ_SIZE(POWERSEQ(x)),1), POWERSEQ(x)) #define POWER2(x) BOOST_PP_TUPLE_ELEM(2, 0, LAST_TUPLE(x)) POWER2(6) I have to generate some sequence and take the last element of it and then extract the result. I didn't find such a macro already in PP. My code seems a bit too complicated. Is there a more trivial way to do this? rds,

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Using Boost 1.41 / output directories
by Rocks User 04 Feb '10

04 Feb '10

Hello, We are migrating to Boost 1.41.0 from boost 1.37.0. When using 1.41.0, the output path for the object files is different than when using 1.37.0. For ex: source code: home/proj/moduleA/1 home/proj/moduleA/2 home/proj/moduleA/3 All object files from moduleA/1, /2, /3 are as follows, when using 1.37.0 home/proj/build/gcc/threading/debug/moduleA/ When using 1.41.0, the object files are created as follows: home/build/gcc/threading/debug/moduleA/1 home/build/gcc/threading/debug/moduleA/2 home/build/gcc/threading/debug/moduleA/3 This is messing up our build esp the header file include paths becasue some of out .h & .cpp files are dynamically generated to the build location and compiled How can I make the object files layout similar to when using 1.37.0? Any help is highly appreciated. Thanks,

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Re: [Boost-users] Help with custom classes PLEASE!!
by Steven Watanabe 04 Feb '10

04 Feb '10

AMDG Daniel Veneros wrote: > Thanks, > > I fixed some things and its running now. > What I don't know how to do is to declarate/allocate a custom class.. > I got this: > > typedef managed_shared_memory::segment_manager SegmentManager; > > typedef allocator<char, SegmentManager> CharAllocator; > > typedef basic_string<char, std::char_traits<char>, CharAllocator> > BasicString; > > typedef allocator<int, SegmentManager> IntAllocator; > > > class Action > { > int id; > BasicString task; > public: > Action(int num, const char *name, const VoidAllocator &void_alloc) > :id(num), task(name,void_alloc) > {} > void setId(int num); > void setTask(BasicString newTask); > }; > > void Action::setId(int num) { > id = num; > } > > void Action::setTask(BasicString newTask) { > task = newTask; > } > > > Now... how should I allocate the "Class" object?? > Any Idea? Thanks!! > I assume that by Class you mean the Action class? If this class is used at the top level, you can use managed_shared_memory::construct. If you want to use an allocator with it, the commands are allocator<Action, SegmentManager> alloc(...); // allocate memory Action* action = alloc.allocate(1); // construct an object using placement new new (action) Action(12, "action", ...); In Christ, Steven Watanabe P.S. Please send messages like this to boost-users rather than directly to me.

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[BGL] predecessor map from a view on a multi_array
by Geoff Hilton 04 Feb '10

04 Feb '10

Hi, I'm currently using MSVC9 and the code listed below doesn't compile, instead producing the following errors and warnings: Warning 1 warning C4100: 'x' : unreferenced formal parameter c:\program files\boost\boost_1_41_0\boost\concept\detail\msvc.hpp 20 test Warning 2 warning C4100: 'id' : unreferenced formal parameter c:\program files\boost\boost_1_41_0\boost\graph\dag_shortest_paths.hpp 86 test Error 3 error C2440: '<function-style-cast>' : cannot convert from 'int' to 'D' c:\program files\microsoft visual studio 9.0\vc\include\limits 109 test I know MSVC has issues with named parameters among other things, but I haven't been able to get it to compile with the non-named-parameters overload either, in this instance. What am I misusing and how am I misusing it? Also, I get the impression that the default combiner/comparer may be unsafe for floating-point comparisons and addition (with respect to over/underflow and comparing floating point values, I seem to recall it being a good idea never to compare with direct equalities, eg. x == infinity because of rounding issues). Might it be a good idea to further specialize appropriate areas of the algorithm code to account for this, or am I over-generalizing(specializing?)? How about a specialized closed_plus<> in relax.hpp which makes the comparisons more safely for floats and doubles (since both parameters "a" and "b" of closed_plus must be of type T anyway)? #include <boost/graph/adjacency_list.hpp> #include <boost/graph/dag_shortest_paths.hpp> #include <boost/multi_array.hpp> namespace geoff { typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::directedS ,boost::no_property, float> Graph; typedef boost::multi_array<boost::graph_traits<Graph>::vertex_descriptor, 2U> PredecessorsMatrix; typedef PredecessorsMatrix::array_view<1>::type PredecessorMap; } //namespace geoff int main(int /*argc*/, char* /*argv*/[]) { const std::size_t num_agents = 3; geoff::Graph graph; geoff::PredecessorsMatrix per_agent_matrix(boost::extents[num_agents][boost::num_vertices(graph)]); geoff::PredecessorsMatrix::index_gen indices; std::size_t agent_index = 0U; geoff::PredecessorMap agent_x_predecessors = per_agent_matrix[indices[agent_index][boost::multi_array_types::index_range()]]; boost::dag_shortest_paths(graph, 0, boost::predecessor_map(agent_x_predecessors)); } Thanks very much, Geoff

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[1.42] PDF documentation build available.
by John Maddock 04 Feb '10

04 Feb '10

Documentation for those Boost libraries that can have their documentation built as PDF is now available from the usual SF download page: https://sourceforge.net/projects/boost/files/ Individual links are: https://sourceforge.net/projects/boost/files/boost-docs/1.42.0/boost_pdf_1_… (26Mb) https://sourceforge.net/projects/boost/files/boost-docs/1.42.0/boost_pdf_1_… (25Mb) https://sourceforge.net/projects/boost/files/boost-docs/1.42.0/boost_pdf_1_… (24Mb) https://sourceforge.net/projects/boost/files/boost-docs/1.42.0/boost_pdf_1_… (23Mb) Enjoy! John.

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Re: [Boost-users] boost any questions and praise
by pete＠pcbartlett.com 04 Feb '10

04 Feb '10

[I fear this conversation is drifting off-topic, but I hope the moderators will forgive a further reply] > > and because it is an any he has no means of > > knowing for sure if the contents are streamable at instantiation time. > > Don't put an object into the any that can't be cout and then try and > cout the any. > > He has to "trust to luck". > > His code put the object into the any in the first place. No luck > involved. Or it's someone elses code but he knows what someone elses > code is giving. Ah you are lucky. You live in a world where you and your co-developers never make any mistakes and the documentation is always up-to-date. I am more fallible and make mistakes and if possible I'd prefer to be told about them via a compile-time error rather than blowing the stack at runtime. > There is more to an object than it's type. You can't just guess what > to give a function based on only the information that it wants one > unsigned integer. Sure - I don't think anyone has said type-safety is a panacea for all coding ills or a replacement for documentation. But the consensus is that it very helpful in C++. Incidentally, you may be interested in the Constrained Value library (http://student.agh.edu.pl/~kawulak/constrained_value/index.html) [1] So if your function needs something in [a,b] rather than [0,UINT_MAX] the type system can give some assistance. [snip irrelevant stuff about "lockup safe" - it's a non-sequitur ] > I do appreciate there are different views here, however if one has > chosen boost::any already then they already know what they want, > especially given the stuff in std. Suggesting that because you can > cause an error an error could unexpectedly occur when you pass > unknown objects into an unknown method in a non sensible example > that wouldn't happen isn't helpful. You have to appreciate where we are coming from. Your original post had code where you tried to pass the result of a runtime method as a template parameter. This suggests you are not hugely familiar with C++ and perhaps Boost.Any, so people naturally ponder whether Boost.Any really is the right choice (often it isn't) and try to help by making sure the OP has heard about the alternatives. > The documentation says that for boost::any a program doesn't crash > if you try and cast an any into a type it was not set as, it gives a > null instead. Actually, If try to retrieve a pointer to the type, it would return a null, if you tried to retrieve a value, it would throw bad_any_cast. > For crashing on stream insertion when it's contents can't be > inserted vs giving an error that will stop the program more safely > and tell the coder what went wrong, I think the latter is more > desirable, unless there is a significant performance difference in > which case either one is valid. Right, if you went down a has_operator_stream route, you could throw an exception instead of blowing the stack. Feel free to offer a patch along those lines if you want , but it opens up a can worms. If operator Links: ------ [1] http://student.agh.edu.pl/~kawulak/constrained_value/index.html)

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Problems with bind
by dilas dilas 04 Feb '10

04 Feb '10

If I have class with to versions of member function: const and non-const, and I use bind to access this member function, then I get a lot of errors. For example: struct A { void foo(void){}; void foo(void)const{}; }; const A a; lambda::bind(&A::foo,lambda::_1 )(a); Can I do something to solve this problem?

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IOStreams: Memory-Mapped files: persistency-question
by Florian Schwarz 04 Feb '10

04 Feb '10

Hello, I'm using the class mapped_file from boost/iostreams to read and write to a file. I stumbled across a persistency-question which I couldn't answer from the documentation. When I'm using a normal c++ ofstream, I can be sure that after I called flush(), that the data is written to disk, even if my program crashes afterwards. But what if I'm using a mapped_file, is there any way to ensure that the written data will reach the disc, even if my program crashes at some later point? Thanks a lot for your help in advance. Best regards Florian

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Re: [Boost-users] [StateChart] Inheriting state
by Tarcisio Fedrizzi 04 Feb '10

04 Feb '10

Hi, I had almost the same problem you have. I solved it in this way: #include <boost/statechart/state_machine.hpp> #include <boost/statechart/simple_state.hpp> #include <boost/statechart/event.hpp> #include <boost/statechart/custom_reaction.hpp> #include <boost/mpl/list.hpp> namespace sc = boost::statechart; namespace mpl = boost::mpl; struct Event1 : sc::event<Event1> {}; template<class Derived, class Outer> struct ActiveBase : sc::simple_state<Derived, Outer> { typedef sc::simple_state<Derived, Outer> base; sc::result react(const Event1& event) { return discard_event(); } using base::discard_event; }; struct Active; struct FSM : sc::state_machine<FSM, Active> { }; struct Active : ActiveBase<Active, FSM> { typedef sc::custom_reaction<Event1> reactions; }; int main() { FSM fsm; fsm.initiate(); } notice the custom_reaction instead on in_state reaction. If you see in the documentation the function to specify for the in state reaction must be: "...|| Either the state defining the in-state reaction itself or one of it direct or indirect contexts..." since the base state (ActiveBase) is not known to the library the library is not able to use the function specified in the in_state_reaction template. Indeed if you specify Active instead of BaseActive in the in_state_reaction template (like in_state_reaction<Event1, Active, &Active::f>) things work a bit better. However this failes to compile anyway because the third parameters is seen to be of type "void (ActiveBase<Active, FSM>::*)(const Event1&)" and this doesn't match the required type. Anyway this is only an hypothesis I would wait for the author response in order to have a correct response. Hope this is helpful. Bye, Tarcisio.

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Compile Boost with visual studio 2008 compiler for Windows CE 6.0
by Tim.Olmer＠priva.nl 04 Feb '10

04 Feb '10

Hi all, I am trying for a couple of days to compile Boost with the Visual Studio 2008 compiler for Windows CE 6.0 I want to use the Boost.Thread Library in Windows CE 6.0. I have understand that I first need to compile STLport. Can I use STLport out of the box or do I need a separate C library for windows CE ?? I have run the configure tool like this: C:\build\STLport-5.2.1>call configure evc9 -x --with-static-rtl --use-boost C:\boost\boost_1_41_0 cl.exe /nologo /TP /WX /GF /GR /EHsc /GL /MT /Zi /O2 /FC /D_STLP_USE_DYNAMIC_LIB /D_STLP_USE_DYNAMIC_LIB /D _WIN32_WCE=0x600 /D UNDER_CE=1 /D "UNICODE" /D "ARM" /D "_ARM_" /D "ARMV4I" /DNDEBUG /I "../../stlport" /I"C:\boost\boost_1_41_0" /c /Foobj\evc9-arm\shared\dll_main.o /Fd"obj\evc9-arm\shared\stlport_x.5.2.pdb" ../../src\dll_main.cpp dll_main.cpp c:\build\stlport-5.2.1\stlport\stl\_ctime.h(38) : error C2039: 'clock' : is not a member of '`global namespace'' c:\build\stlport-5.2.1\stlport\stl\_ctime.h(38) : error C2873: 'clock' : symbol cannot be used in a using-declaration c:\build\stlport-5.2.1\stlport\stl\_ctime.h(39) : error C2039: 'asctime' : is not a member of '`global namespace'' c:\build\stlport-5.2.1\stlport\stl\_ctime.h(39) : error C2873: 'asctime' : symbol cannot be used in a using-declaration c:\build\stlport-5.2.1\stlport\stl\_ctime.h(40) : error C2039: 'ctime' : is not a member of '`global namespace'' c:\build\stlport-5.2.1\stlport\stl\_ctime.h(40) : error C2873: 'ctime' : symbol cannot be used in a using-declaration c:\build\stlport-5.2.1\stlport\stl\_ctime.h(41) : error C2039: 'gmtime' : is not a member of '`global namespace'' c:\build\stlport-5.2.1\stlport\stl\_ctime.h(41) : error C2873: 'gmtime' : symbol cannot be used in a using-declaration c:\build\stlport-5.2.1\stlport\stl\_ctime.h(46) : error C2039: 'mktime' : is not a member of '`global namespace'' c:\build\stlport-5.2.1\stlport\stl\_ctime.h(46) : error C2873: 'mktime' : symbol cannot be used in a using-declaration c:\build\stlport-5.2.1\stlport\stl\_ctime.h(47) : error C2039: 'localtime' : is not a member of '`global namespace'' c:\build\stlport-5.2.1\stlport\stl\_ctime.h(47) : error C2873: 'localtime' : symbol cannot be used in a using-declaration c:\build\stlport-5.2.1\stlport\stl\_ctime.h(48) : error C2039: 'strftime' : is not a member of '`global namespace'' c:\build\stlport-5.2.1\stlport\stl\_ctime.h(48) : error C2873: 'strftime' : symbol cannot be used in a using-declaration c:\build\stlport-5.2.1\stlport\stl\_ctime.h(49) : error C2039: 'time' : is not a member of '`global namespace'' c:\build\stlport-5.2.1\stlport\stl\_ctime.h(49) : error C2873: 'time' : symbol cannot be used in a using-declaration Does anyone know why I get this error and how to solve this? Thanks in advance! ______________________________________________________________________ Priva B.V. A disclaimer is applicable to this email, please refer to www.priva.nl/disclaimer. Op deze email is een disclaimer van toepassing, ga naar www.priva.nl/disclaimer.

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How to convert wide character strings to multi-byte strings ?
by Timothy Madden 04 Feb '10

04 Feb '10

Hello What is the right way to convert from wide character strings to multi-byte strings ? In boost or in C++ if any ? For narrow to wide conversion I can do wostringstream streamMsg; streamMsg << "Narrow string"; wstring wstrMessage = streamMsg.str(); But I think that too is not a good way as it might not take the current locale / code page /encoding /whatever into account, but just widen the char (as a number) to an wchar_t. So what is the right way ? How do I write a codecvt facet for the default locale if I need one ? Thank you, Timothy Madden

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array of small world graphs
by Vasilis Hatzopoulos 04 Feb '10

04 Feb '10

Hi all, new to boost and experiencing a bit of an issue with generating a collection of small worlds. Basically i want for each pass of the loop to generate a small world with a certain pRewire. Here's some code typedef small_world_iterator<mt19937, Graph> SWGen; base_generator_type generator(1u); for(int i = 0; i < num_graphs; i++){ Graph g( SWGen( generator, N, k, pRewire, SWGen(), N ); . . some operations on g, i.e. path lengths e.t.c. } As it happens all graphs g are the same graph while what i want is a collection of different small worlds with the same pRewire. Why does the state of the generator not advance after the first Graph is generated? Can anyone please help me with this. Thanks for your time, Vasilis.

2 1

building boost under mingw-w64
by Alexander Kalinin 04 Feb '10

04 Feb '10

Hi, Here some details about building boost under mingw-w64. I am using only "threads" and "date_time" libraries from boost and I started to building boost by command: bjam --prefix=c:\boost toolset=gcc address-model=64 variant=debug,release link=static,shared threading=multi --with-thread --with-date_time install and I got an error: ./boost/thread/win32/basic_ timed_mutex.hpp:152: error: cast from 'void*' to 'long int' loses precision This caused by the macros BOOST_INTERLOCKED_COMPARE_EXCHANGE_POINTER defined in interlocked.hpp. This macros has several definitions that depends on building defines. So I add BOOST_USE_WINDOWS_H define into the building command: bjam --prefix=c:\boost toolset=gcc address-model=64 variant=debug,release link=static,shared threading=multi --with-thread --with-date_time define=BOOST_USE_WINDOWS_H install add boost was compiled successful. The question is. Is it possible to build boost under mingw-w64 without BOOST_USE_WINDOWS_H define?

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