November 2011 - Boost-users - lists.preview.boost.org

fusion quesion
by Robert Ramey 25 Nov '11

25 Nov '11

Fusion includes a number of binary functions such as join, equal, less, etc. Looking at the code suggests that they just work element by element in sequential order. But what about associative tuples? For example struct account {}; struce amount {}; typedef boost::fusion::set< account, amount > debit; typedef boost::fusion::set< amount, account > debit2. clearly the types are meant to be the "same" so I would expect boost::fusion::join(debit, debit2) to function and return one type. I'm thinking it doesn't do that. Any observations/suggestions that any Fusion guru would like to share would be appreciated. Robert Ramey

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Re: [Boost-users] Scope exit with no capture
by Bruno Martinez 24 Nov '11

24 Nov '11

>> It seems scope exit is abandoned. > > Not abandoned but carefully looked after. I'm happy to hear this. > Scroll down the post > you're refering to to this line: >> #define this(x) (this(x)) > > Check the code in > http://lists.boost.org/Archives/boost/2009/05/151353.php > Do we want to go that far? What do you mean? Note that the limitation that's bothering me is having an empty capture list, not capturing this. > Also, there are some limitations (a) "this" must be first in a > capture list and (b) there is no way you can use "this" inside > a body if you use C++03 compiler. > > So, rather than raising a learning curve for no clear benefit, > I prefer being explicit and write: > > YourClass *this_ = this; BOOST_SCOPE_EXIT((this_)... > or > YourClass& self = *this; BOOST_SCOPE_EXIT((self)... I've not bumped into the this limitation yet. I want a clean way to run code at exit that needs no access to local variable and captures nothing. Since my compiler supports lambda, I've adopted the old scopeguard from loki. It would be great if scope_exit supported & and = capture for all needed variables as hinted in the documentation as a possibility, or better yet, reimplement scope_guard, which has better syntax. Bruno

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Graph and external properties
by g4hx 24 Nov '11

24 Nov '11

Hello everyone, I am currently trying to implement a graph algorithm using boost::graph but I ran into a problem which I don't know how to fix. I already asked this question http://stackoverflow.com/questions/8234910/external-property-map-tied-to-st… but I got no answer yet, apart from someone telling me that "Boost.Graph" is borderline unusable. I thought that you people wouldn't let this stand, so I am just asking you: I need some variables stored in a vector to be accessible via an operator[](edge_descriptor&), I think that this could be done using external properties, but since I already use bundled internal properties, I am not sure how to go ahead. I basically need something as in http://www.boost.org/doc/libs/1_36_0/libs/property_map/iterator_property_ma…. I would very much appreciate it someone would just drop me a few lines of code to illustrate how to solve the problem. g4hx

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[Thread] program crashes from time to time when deleting unique_future<void>
by Soderback, Johan 24 Nov '11

24 Nov '11

Hi, I have a small example program that crashes from time to time. I would appreciate some help to understand why. In function run() executed on the main thread I create a packaged_task (pt), put it in a queue (_q) and wait for it to get executed (fu.get()). In another thread the tasks are executed when the queue _q is populated. The task I'm running always throws/rethrows intentionally. It results (from time to time) in an access violation when the unique_future, fu, is deleted. See the stack trace at the bottom. Anybody see any flaws in this design? I have tried 1.47.0 and 1.48.0, MSVC 2005. Here's the code. ***************************************************** #include <boost/exception/all.hpp> #include <boost/thread.hpp> #include <sstream> #include <iostream> struct Exception : public virtual std::exception , public virtual boost::exception { }; struct TheException : public virtual Exception {}; void throwf() { try { BOOST_THROW_EXCEPTION(TheException()); } catch (...) { boost::current_exception_diagnostic_information(); throw; } } struct Test { Test() { _t.reset(new boost::thread(boost::bind(&Test::executor, this))); } ~Test() { _t->join(); } void executor() { for (;;) { boost::unique_lock<boost::mutex> lk(_mx); while(_q.empty()) { _cv.wait(lk); } boost::shared_ptr< boost::packaged_task<void> > pt = _q.front(); _q.pop_front(); lk.unlock(); (*pt)(); } } void run() { for (;;) { const int N = 20000; for (int j = 0; j < N; ++j) { boost::shared_ptr< boost::packaged_task<void> > pt(new boost::packaged_task<void>(throwf)); boost::unique_future<void> fu = pt->get_future(); { boost::unique_lock<boost::mutex> lk(_mx); _q.push_back(pt); pt.reset(); } _cv.notify_one(); try { fu.get(); assert(false); } catch (const TheException& ) { } catch (const boost::exception& ) { assert(false); } catch (...) { assert(false); } } std::cout << "."; } } private: boost::mutex _mx; std::list< boost::shared_ptr< boost::packaged_task<void> > > _q; boost::shared_ptr<boost::thread> _t; boost::condition_variable_any _cv; }; int main(int, char*) { Test test; test.run(); } ***************************************************** Here is the callstack, program terminated with access violation. Unhandled exception at 0x0043196b in crasher.exe: 0xC0000005: Access violation reading location 0xdddddded. > crasher.exe!boost::exception_detail::refcount_ptr<boost::exception_detail::error_info_container>::release() Line 78 + 0x18 bytes C++ crasher.exe!boost::exception_detail::refcount_ptr<boost::exception_detail::error_info_container>::~refcount_ptr<boost::exception_detail::error_info_container>() Line 35 C++ crasher.exe!boost::exception::~exception() Line 278 + 0xb bytes C++ crasher.exe!boost::exception_detail::clone_impl<TheException>::`vbase destructor'() + 0x41 bytes C++ crasher.exe!boost::exception_detail::clone_impl<TheException>::`scalar deleting destructor'() + 0x2b bytes C++ crasher.exe!boost::checked_delete<boost::exception_detail::clone_base const >(const boost::exception_detail::clone_base * x=0x006f7d10) Line 34 + 0x35 bytes C++ crasher.exe!boost::detail::sp_counted_impl_p<boost::exception_detail::clone_base const >::dispose() Line 78 + 0xc bytes C++ crasher.exe!boost::detail::sp_counted_base::release() Line 102 + 0xf bytes C++ crasher.exe!boost::detail::shared_count::~shared_count() Line 309 C++ crasher.exe!boost::shared_ptr<boost::exception_detail::clone_base const >::~shared_ptr<boost::exception_detail::clone_base const >() + 0x2e bytes C++ crasher.exe!boost::exception_ptr::~exception_ptr() + 0x2b bytes C++ crasher.exe!boost::detail::future_object_base::~future_object_base() Line 106 + 0x9c bytes C++ crasher.exe!boost::detail::future_object<void>::~future_object<void>() + 0x2b bytes C++ crasher.exe!boost::detail::task_base<void>::~task_base<void>() + 0x2b bytes C++ crasher.exe!boost::detail::task_object<void,void (__cdecl*)(void)>::~task_object<void,void (__cdecl*)(void)>() + 0x2b bytes C++ crasher.exe!boost::detail::task_object<void,void (__cdecl*)(void)>::`scalar deleting destructor'() + 0x2b bytes C++ crasher.exe!boost::checked_delete<boost::detail::task_object<void,void (__cdecl*)(void)> >(boost::detail::task_object<void,void (__cdecl*)(void)> * x=0x006f7b10) Line 34 + 0x34 bytes C++ crasher.exe!boost::detail::sp_counted_impl_p<boost::detail::task_object<void,void (__cdecl*)(void)> >::dispose() Line 78 + 0xc bytes C++ crasher.exe!boost::detail::sp_counted_base::release() Line 102 + 0xf bytes C++ crasher.exe!boost::detail::shared_count::~shared_count() Line 309 C++ crasher.exe!boost::shared_ptr<boost::detail::future_object<void> >::~shared_ptr<boost::detail::future_object<void> >() + 0x2e bytes C++ crasher.exe!boost::unique_future<void>::~unique_future<void>() Line 644 + 0x2b bytes C++ crasher.exe!Test::run() Line 95 + 0xc bytes C++ crasher.exe!main(int __formal=1, int __formal=1) Line 112 C++ crasher.exe!__tmainCRTStartup() Line 597 + 0x19 bytes C crasher.exe!mainCRTStartup() Line 414 C kernel32.dll!7c817067() [Frames below may be incorrect and/or missing, no symbols loaded for kernel32.dll] ________________________________ Please consider the environment before printing this e-mail. 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Iterate over template arguments
by Allan Nielsen 24 Nov '11

24 Nov '11

Hi, I have a set of old classes which I use for inter process communication: Example: template<typename T0, typename T1> class Interface2: public InterfaceBase { public: Interface2( const std::string & name, IPCManager * ipcmanager) : InterfaceBase(name, ipcmanager){ } Interface2( const std::string & name, boost::function<void ( const T0 & t0, const T1 & t1 ) > _f, IPCManager * ipcmanager) : InterfaceBase(name, ipcmanager), f(_f) { } virtual ~Interface2() { } boost::function<void ( const T0 & t0, const T1 & t1 ) > f; protected: void handler(IpcMsg & m) { if(! f.empty()){ if( m.value_size() != 2 ) { m.set_type(IpcMsg_Type_RESPONSE_FAILED_WRONG_VALUE_NUMBERS); return; } GMB_ARGUMENT_DESERILIZE(T0, 0); GMB_ARGUMENT_DESERILIZE(T1, 1); try { f(t0, t1); m.set_type(IpcMsg_Type_RESPONSE_OK); } catch (std::exception e) { m.set_type(IpcMsg_Type_RESPONSE_FAILED_EXCEPTION); } }else{ m.set_type(IpcMsg_Type_RESPONSE_FAILED_NO_FUNCTION_ATTACHED); } } IPCManager * ipc; }; It works fine, but it might not be the most elegant solution, and I would very much like to improve it. Today I have Interface0-10 which accept from 0 to 10 arguments, and InterfaceCaller0-10 which call an interface with 0-10 arguments. And another set of classes with an return value as well. What I would like is an interface where the following would be valid (much like boost function): Interface< int (int, std::string ) > if1(...) ; I known this might not be easy or the intension of c++99, but I would like to give it a try anyway... So, I would appreciate it if somebody could give me some pointers on how I can process each of the templates arguments. I do not have access to a c++0x compiler on the target where this is used. Best regards Allan W. Nielsen

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[locale] 1.48+stlport5.2.1: invalid conversion from `int' to `stlp_std::ctype_base::mask'
by Bogdan Slusarczyk 24 Nov '11

24 Nov '11

Hi, I tried to build boost1.48 with stlport5.2.1 (linux). I noticed such problem: libs/locale/src/posix/numeric.cpp:215: error: invalid conversion from `int' to `stlp_std::ctype_base::mask' This is simple problem like this one: enum Test { value } Test test; test|=value; //error is here I could use -fpermissive, however I think it's very intrusive. If you know other solutions let me know please. Best regards, Bogdan

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multi_index_container + composite key
by Uthpal Urubail 24 Nov '11

24 Nov '11

All, Is it possible create a multi_index_container with keys in non sequenced order? i.e, in the below example while extracting the element book entry can I send the node1 and node2 in different order than how it is created? elementbook pb; Elem_entry fc1 = Elem_entry(1,90,99); Extracting: elementbook::iterator it; it = pb.find(boost::make_tuple(99,90)); ????? Is it possible to simulate this requirement? typedef multi_index_container< Elem_entry, indexed_by< //non-unique as some might have more than ids ordered_unique< composite_key< Elem_entry, member<Elem_entry,unsigned int,&Elem_entry::node1>, member<Elem_entry,unsigned int,&Elem_entry::node2> > >, ordered_unique< member<Elem_entry,unsigned int,&Elem_entry::faceid> > > > elementbook;

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Vertex Weights!!!
by Nouf M. 24 Nov '11

24 Nov '11

Hello, I have a graph that contains: - Vertices with 1.name 2.weight - Edges with 1.name 2.weight I couldnt figure out how to store the weights of the vertices. Is it possible to do that? if yes, then please tell me how... Thank you...

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How to use mpl::count and function_types
by Allan Nielsen 24 Nov '11

24 Nov '11

Hi I'm trying to count the number of parameters in a function-type: cout << boost::mpl::count< boost::function_types::parameter_types< void() > >::value << endl; cout << boost::mpl::count< boost::function_types::parameter_types< void(int) > >::value << endl; cout << boost::mpl::count< boost::function_types::parameter_types< void(int, int) > >::value << endl; This prints: 0 0 0 I would have expected: 0 1 2 What have I done wrong? -- Allan W. Nielsen

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[iostreams] 7-zip filters
by Igor R 24 Nov '11

24 Nov '11

Hello, I tried to google around the subj, but couldn't find anything useful. Is it realy unavailble or have I just overlooked it? :) Thanks.

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