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Re: [Boost-users] Boost thread questions
by Merrill Cornish 01 Mar '06

01 Mar '06

Hector, >>> how to lock a file (fstream) for reading/writing Are you trying to lock the _file_ on disk for all applications running on the system? Or, are you trying to lock a stream opened to that file for different threads in your application? In the first case, you need to use an OS-level lock, not Boost. In the second case, use a mutex as someone else suggested. Merrill

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[statechart] Template States, Compile Error
by David Greene 01 Mar '06

01 Mar '06

The attached testcase doesn't compile with g++ 4.0.2 or g++ 3.2.3. The compiler generates a series of error messages like this: boost/statechart/simple_state.hpp:189: error: no type named 'inner_context_type' in 'struct Test::NormalMode<int>' I hastily sketched this out based on a larger code. If there are typos or other mistakes, let me know but the main problem I'm trying to solve is the "no type named" problem. I typedef it right in the template definition for NormalMode! This is using the current CVS for statechart, 1.33.1 for mpl. Is it possibly a compiler bug? Thanks! -Dave ---------------- Testcase #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/statechart/state.hpp> #include <boost/statechart/transition.hpp> #include <boost/mpl/list.hpp> #include <iostream> // Switch finite state machine for multiplexor schedule policy namespace Test { namespace sc = boost::statechart; namespace mpl = boost::mpl; // Inner states template <typename Type> struct On; template <typename Type> struct Off; template <typename Type> struct Error; // Outer states template <typename Type> struct NormalMode; template <typename Type> struct ErrorMode; // Events struct End : public sc::event<End> {}; struct UnconsumedEvent : public sc::event<UnconsumedEvent> { std::string st; UnconsumedEvent(const std::string &s) : st(s) {}; const std::string &state(void) const { return(st); }; }; template<typename Derived, typename Type> struct SwitchEvent : public sc::event<Derived> { typedef Type value_type; value_type ev; SwitchEvent(value_type e) : ev(e) {}; value_type value(void) const { return(ev); } }; template<typename Type> struct TurnOn : public SwitchEvent<TurnOn<Type>, Type> { TurnOn(Type value) : SwitchEvent<TurnOn<Type>, Type>(value) {}; }; template<typename Type> struct TurnOff : public SwitchEvent<TurnOff<Type>, Type> { TurnOff(Type value) : SwitchEvent<TurnOff<Type>, Type>(value) {}; }; template<typename Type> struct Switch; namespace detail { template<typename Type> struct typedefs { typedef Type value_type; typedef Switch<value_type> switch_context; typedef TurnOn<value_type> turn_on; typedef TurnOff<value_type> turn_off; typedef On<value_type> on; typedef Off<value_type> off; }; }; // The state machine template<typename Type> struct Switch : public sc::state_machine<Switch<Type>, NormalMode<Type> >, public detail::typedefs<Type> { typedef sc::state_machine<Switch<Type>, NormalMode<Type> > Base; typedef Switch<Type> This; std::string state(void) const { if (this->template state_cast<const typename This::on *>()) { return("ON"); } else if (this->template state_cast<const typename This::off *>()) { return("OFF"); } else { std::cerr << "Unknown state" << std::endl; std::abort(); return("ERROR"); } }; // Abort on unexpected events void unconsumed_event(const sc::event_base &event) { std::cerr << "Unexpected event in state " << state() << std::endl; std::abort(); this->post_event(new UnconsumedEvent(state())); }; }; // Define states // Outer template<typename Type> struct NormalMode : public sc::simple_state<NormalMode<Type>, Switch<Type>, Off<Type> >, public detail::typedefs<Type> { typedef sc::simple_state<NormalMode<Type>, Switch<Type>, Off<Type> > state_base; typedef typename state_base::inner_context_type inner_context_type; }; template<typename Type> struct ErrorMode : public sc::simple_state<ErrorMode<Type>, Switch<Type>, Error<Type> >, public detail::typedefs<Type> { typedef sc::simple_state<ErrorMode<Type>, Switch<Type>, Error<Type> > state_base; typedef typename state_base::inner_context_type inner_context_type; }; // Inner template<typename Type> struct Off : public sc::simple_state<Off<Type>, NormalMode<Type> >, public detail::typedefs<Type> { typedef Off<Type> This; typedef mpl::list< sc::custom_reaction<typename This::on>, sc::custom_reaction<End> > reactions; sc::result react(const typename This::on &) { this->template context<typename This::switch_context>().transit("OFF", "ON"); return(this->template transit<typename This::on>()); }; sc::result react(const End &) { this->terminate(); }; }; template<typename Type> struct On : public sc::simple_state<On<Type>, NormalMode<Type> >, public detail::typedefs<Type> { typedef On<Type> This; typedef mpl::list< sc::custom_reaction<typename This::off>, sc::custom_reaction<End> > reactions; sc::result react(const typename This::off &) { this->template context<typename This::switch_context>().transit("ON", "OFF"); return(this->template transit<typename This::off>()); }; sc::result react(const End &) { this->terminate(); }; }; template<typename Type> struct Error : sc::simple_state<Error<Type>, ErrorMode<Type> >, public detail::typedefs<Type> { }; }; int main(void) { Test::Switch<int> machine; machine.initiate(); machine.process_event( Test::TurnOn<int>(0) ); std::cout << "Now in state " << machine.state() << std::endl; machine.process_event( Test::TurnOff<int>(0) ); std::cout << "Now in state " << machine.state() << std::endl; machine.process_event( Test::TurnOff<int>(0) ); // Should produce error std::cout << "Now in state " << machine.state() << std::endl; machine.process_event( Test::End() ); }

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Re: [Boost-users] [iostreams] array_sink
by EMalenfant＠interstarinc.com 01 Mar '06

01 Mar '06

From: Jeff Flinn [mailto:TriumphSprint2000@hotmail.com] > > My reading of the docs states that array_sink models the > concept sink, meaning that the following should compile: > [snip] > > io::array_sink lSink(x,4); > > const char* y = "abc"; > > io::write( lSink, y, 4 ); [snip] > > I must be doing something obviously wrong, on VC7.1 I get: > > c:\boost\boost_1_33_1\boost\iostreams\write.hpp(118) : error > C2039: 'write' > : is not a member of 'boost::iostreams::basic_array_sink<Ch>' [snip] Hi Jeff, I think this is related to the fact that array_sink is a "direct" sink. At the bottom of this page: http://www.boost.org/libs/iostreams/doc/?path=4.1.1.7 there is mention that "io::write()" is subject the the precondition that the sink is *not* convertible to "direct_tag". BTW, in the "details" of the iostreams library, there is a "direct_adapter" which seems to allow one to expose a "direct" Device as an "indirect" one. HTH, Éric Malenfant

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Re: [Boost-users] [mpl] newbie question
by james.jones＠firstinvestors.com 01 Mar '06

01 Mar '06

Andy Little wrote: > Of course If anyone can implement the dimensional-analysis part of pqs > (in the Boost vault in The Physical Quantities Units directory) , such > that it compiles faster than it does currently, by using mpl, then I > will be happy to re-implement it using mpl. If I recall previous posts correctly, the compile-time using MPL was 30 seconds, and using your own code 4 seconds. Is this really a good reason not to use MPL? I would understand if it were 30 *minutes* versus 4 seconds. But in this case you're gaining 26 seconds per compile at the price of writing some custom code that may or may not be as maintainable as MPL (not saying it isn't - I haven't looked at pqs). I think in general it's understood that C++ in general, and BOOST in particular, can tend to increase compile times, because they heavily invest in compile-time template logic. But as I see it, an extra 26 seconds per compile times, say, 1000 compilations (to be generous) on a given project, is about one man-day (really less: it's 7-1/4 hours; how many of us put in only that much in a given workday?). Do you think it takes less than a man-day to come up with an MPL replacement, even one that only handles a subset of the functionality? Maybe, but I think there's reason to be skeptical. Also, if MPL resulted in a 7-times slower *runtime* than custom code, then choosing not to use might make more sense. Is that the case? If so, I missed it. Anyway, not saying you made the wrong decision, just offering a possible alternative way to think about this. - James

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Re: [Boost-users] [BGL] Dijkstra Shortest Paths
by Michael Kettner 01 Mar '06

01 Mar '06

Hi Marcio! On Wednesday 29 March 2006 14:43, Marcio Paim de Aquino wrote: > Hello all, > > does anyone know how to make a custom dijkstra visitor that ends the > algorithm when > it finds the path between two especified vertexes? You might read the manual. This is from http://www.boost.org/libs/graph/doc/faq.html How do I perform an early exit from an algorithm such as BFS? Create a visitor that throws an exception when you want to cut off the search, then put your call to breadth_first_search inside of an appropriate try/catch block. This strikes many programmers as a misuse of exceptions, however, much thought was put into the decision to have exceptions has the preferred way to exit early. See boost email discussions for more details. Regards, Michael > Thanks, > > Marcio

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[BGL] Dijkstra Shortest Paths
by Marcio Paim de Aquino 01 Mar '06

01 Mar '06

Hello all, does anyone know how to make a custom dijkstra visitor that ends the algorithm when it finds the path between two especified vertexes? Thanks, Marcio

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Re: [Boost-users] problem with serialization of pure virtual
by Nat Goodspeed 01 Mar '06

01 Mar '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org [mailto:boost-users- > bounces(a)lists.boost.org] On Behalf Of Tobias Combe > Sent: Tuesday, February 28, 2006 7:18 AM > To: boost-users(a)lists.boost.org > Subject: [Boost-users] problem with serialization of pure virtual > > When i use "ar.register<derived>();" in the template of the base-class > to register the derived classes, i get a syntax error. [Nat] What compiler are you using?

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serialization: found a (satisfactory) way to avoid the abstract class problem linking problem
by RIVASSEAU Jean Noel 01 Mar '06

01 Mar '06

Hello Robert, I found a way to avoid the link problem when dealing with a base abstract class, that maintains the base class abstract : I just manually instantiated the save/load functions for the abstract base class. They should have been instantiated by BOOST_CLASS_EXPORT, but this apparently does not work with abstract base classes; however manual instantiation works just fine. So I now have only one more problem (unfortunately, very serious), that happens with the serialization of std::vector containing pointers. Jean-Noël

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What can I do after I finished all the steps of "getting started" ?
by 郭华长 01 Mar '06

01 Mar '06

thanks _________________________________________________________________ 与联机的朋友进行交流，请使用 MSN Messenger: http://messenger.msn.com/cn

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Re: [Boost-users] serialization: errata: even manual instantiationisimpossible
by RIVASSEAU Jean Noel 01 Mar '06

01 Mar '06

// my_class_serialization.cpp or my_class.cpp or .. *.cpp #include <boost/archive/xml_iarchive.hpp> .... // all archives you might whant to use here. template<class Archive> serialize(Archive &ar, my_class &t....){ ... serialization for class my_class } #include "my_class.hpp" // explict instantiation here for all the archives which interest me template void serialize<boost::archive::xml_iarchive, my_class>; ... // explicit instantiation for all other archives you might use here. I notice you still include the archive headers in my_class_serialization.cpp. In that case, you do not have in fact to manually instantiate templates, since my_class_serialization.cpp includes "my_class.hpp" which includes export.hpp and maybe BOOST_CLASS_EXPORT after the archive headers included in class_serialization.cpp, so template instantiation will occure anyway. Anyway let's close this topic. I understood what the point was. Jean-Noël

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