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about convert adjacency_matrix into common boost matrix
by Peng Wang 24 Dec '08

24 Dec '08

Hi, I am a newbie of boost. Could I ask one question that how to convert BGL adjacency_matrix object into common matrix (http://www.boost.org/doc/libs/1_37_0/libs/numeric/ublas/doc/matrix.htm)? I am sorry that if the question is too simple. I have looked around but did not find a answer. Thank you very much in advance. Sincerely yours, Wang

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[iterator] transform_iterator
by Max 24 Dec '08

24 Dec '08

Hello I just came across transform_iterator and found it a useful generic tool. But is it possible for it to go further to make the following code get compiled and run as expected? struct A { int i_; A() : i_(0) {} explicit A(int i) : i_(i) {} }; const int N = 5; A a_list[N] = { A(-3), A(1), A(3), A(2), A(-4) }; typedef boost::function<int(A)> fn_t; // sorting a_list according to the elements' i_ member std::stable_sort(boost::make_transform_iterator(a_list, fn_t(boost::bind(&A::i_, _1))), boost::make_transform_iterator(a_list+N, fn_t(boost::bind(&A::i_, _1))), std::less<int>()); Thanks B/Rgds Max ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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Re: [Boost-users] [boost] [shared_ptr] A smarter smart pointer proposal for dyn
by Max 24 Dec '08

24 Dec '08

Hello Dotchevski, Could you please elaborate? Thanks. B/Rgds Max ----- Original Message ----- From: Emil Dotchevski To: boost(a)lists.boost.org Subject: Re: [boost] [shared_ptr] A smarter smart pointer proposal for dynamic libraries Date: 2008-12-24 12:37:33 As far as I can tell, the only reason your reset() appears to work is that it is inlined in the executable. The compiler doesn't guarantee inlining, so in general it will crash anyway. The solution to this problem is to inject the DLL's lifetime into any shared_ptrs obtained from that DLL; that is, make the shared_ptr keep the DLL afloat. This can be done easily (and non-intrusively) using shared_ptr's aliasing constructor. Emil Dotchevski Reverge Studios, Inc. http://www.revergestudios.com/reblog/index.php?n=ReCode ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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boost::interprocess on FreeBSD 7
by Andy Wiese 24 Dec '08

24 Dec '08

Using boost::interprocess from boost_1_37_0 on FreeBSD 7.0, I get a segmentation fault in pthread_mutex_lock() from /lib/libthr.so. 3, in what appears to anything related to a ShmemAllocator. For example, when I run the example from http://www.boost.org/doc/libs/1_37_0/doc/html/interprocess/allocators_conta… I get the segfault at this line: //Initialize the STL-like allocator const ShmemAllocator alloc_inst (segment.get_segment_manager()); I stepped back to this simple test after encountering this segfault (always in pthread_mutex_lock) when trying to use almost any function of segment_manager from managed_mapped_file. This is from an mapped file boost::interprocess::map structure that works very well on darwin. Is there any hope to getting this to work on FreeBSD? ----------------------------------------------------------------------------------------------- FWIW, here is the complete text of the example: void test_ipc2() { using namespace boost::interprocess; shared_memory_object::remove("MySharedMemory"); try{ //A managed shared memory where we can construct objects //associated with a c-string managed_shared_memory segment(create_only, "MySharedMemory", //segment name 65536); //Alias an STL-like allocator of ints that allocates ints from the segment typedef allocator<int, managed_shared_memory::segment_manager> ShmemAllocator; //Alias a vector that uses the previous STL-like allocator typedef vector<int, ShmemAllocator> MyVector; int initVal[] = {0, 1, 2, 3, 4, 5, 6 }; const int *begVal = initVal; const int *endVal = initVal + sizeof(initVal)/sizeof(initVal[0]); //Initialize the STL-like allocator const ShmemAllocator alloc_inst (segment.get_segment_manager()); //Construct the vector in the shared memory segment with the STL- like allocator //from a range of iterators MyVector *myvector = segment.construct<MyVector> ("MyVector")/*object name*/ (begVal /*first ctor parameter*/, endVal /*second ctor parameter*/, alloc_inst /*third ctor parameter*/); BOOST_CHECK(myvector); //Use vector as your want std::sort(myvector->rbegin(), myvector->rend()); // . . . //When done, destroy and delete vector from the segment segment.destroy<MyVector>("MyVector"); } catch(...){ shared_memory_object::remove("MySharedMemory"); throw; } shared_memory_object::remove("MySharedMemory"); }

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shared_ptr downcast
by Jason Cipriani 24 Dec '08

24 Dec '08

If I have: class Base { }; class Derived : public Base { }; And a container, e.g.: std::vector<boost::shared_ptr<Base> > objs; How do I downcast to a shared_ptr<Derived>? E.g.: boost::shared_ptr<Derived> d = (boost::shared_ptr<Derived>)objs[0]; I have a function that takes a shared_ptr<Derived> and all I have is a shared_ptr<Base>. I don't mind static_cast behavior, although dynamic_cast behavior would be ideal. Thanks, Jason

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[Spirit] Building an expression parser with boost.spirit
by Max 24 Dec '08

24 Dec '08

Thank you! It's really a vault full of spirit examples from beginning tutorials to full-fledged applications! Best regards Max ----- Original Message ----- From: Joel de Guzman To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [Spirit] Building an expression parser with boost.spirit Date: 2008-12-24 11:07:20 Max wrote: > Thank you Hartmut. > > I've found some simple examples using Google and an > expression parser, exactly as what I described, which is > built on boost.spirit: > > http://idlebox.net/2007/stx-exparser/#subsec_grammar Also, see http://spirit.sourceforge.net/repository/applications/show_contents.php Spirit2 has extensive calculator examples from the simplest expression evaluator progressing incrementally to a full C-like compiler. Regards, -- Joel de Guzman http://www.boostpro.com http://spirit.sf.net ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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Re: [Boost-users] [Spirit] Building an expression parser with boost.spirit
by Max 24 Dec '08

24 Dec '08

Thank you Hartmut. I've found some simple examples using Google and an expression parser, exactly as what I described, which is built on boost.spirit: http://idlebox.net/2007/stx-exparser/#subsec_grammar Best regards Max ----- Original Message ----- From: Hartmut Kaiser To: Subject: Re: [Boost-users] [Spirit] Building an expression parser with boost.spirit or any other Date: 2008-12-23 22:41:43 > There are several parsing tool libs in boost, say spirit and wave, > pheonix, etc. > But I am just not quite clear of the relation between each of them. > I've skimmed through some of the documentation some time ago, but it > seems to be too tough to me till now. > > My question is, giving the huge power of these libs, is it simple to > construct an traditional expression parser which accepts formulea like: > > 1+2/3 > sin(0.34)/power(tan(.4),3) > and so on > > Or, preferably, is there already a sample program like this anywhere? I'd say, go with Spirit. Examples are for instance in the Spirit distribution ($BOOST_ROOT/libs/spirit/examples) and here: http://spirit.sourceforge.net/repository/applications/show_contents.php. HTH Regards Hartmut ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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Accumulators: Using data vector from Interprocess
by dhruva 24 Dec '08

24 Dec '08

Hi, I have large data to be processed hence planning to use memory mapped file backed vector from boost::interprocess. Could I use this vector directly in accumulators and perform computations on data in the boost::interprocess container without having to copy it all into the contain in accumulator_set? Also, is there a way to remove an entry once I add it to an accumulator_set? I want to emulate a sliding window calculation. Ex: If my window size is 100, when I add the 101st entry, I want to remove the 1st entry so that the size is always 100. -dhruva -- Contents reflect my personal views only!

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Re: [Boost-users] [STL] Is there a std::abs<>() function?
by Max 24 Dec '08

24 Dec '08

Hello Anteru, Yes, there exist several overloads of abs() functions or similar but some of them with different name, say fabs, fabsf, etc. This make it impossible to use it in generic code. More specifically, I've ever written this code cout << std::abs<int>(-1) << endl; but, to my very surprise, I get 0! I have #include <cmath> #include <cstdlib> I'm using VS2003SP1 under WinXP_SP1 Thanks B/Rgds Max ----- Original Message ----- From: Anteru To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [STL] Is there a std::abs<>() function? Date: 2008-12-23 19:00:56 Max schrieb: > Hello, > > It's strange to me that there seems not to be a std::abs<>() function > in STL, with it I can write code like this: > > double d = std::abs(-1.0); > int i = std::abs(-1); > > Does anybody else have the same feeling? #include double d = std::abs (-1.0); cmath pulls the standard math functions into the std namespace, and adds a few overloads. See for example: http://www.dinkumware.com/manuals/?manual=compleat&page=math.html#abs Cheers, Anteru ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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[Statechart] Order of Trigger/Event/Guard at state transition
by Franz Alt 23 Dec '08

23 Dec '08

Hi all, I've tried to use the Statechart library for modelling a simple state machine. I've created three states and three transitions between them and added some debug outputs. When I've looked to the debug outputs I've wondered a little bit. I've thought that the processing of events are in the order 1) exit actions of source state 2) transition actions and 3) entry actions of target state. When I look at my result I see the order 1) transition action 2) exit action of source state and 3) entry action of target state. Does anybody know what I'm doing wrong here? Best regards, Franz #include <iostream> #include "FSMSimple.h" using namespace std; int main(int argc, char * argv[]) { // Instanciate the FSM ... FSMSimple sm; // ... and start it sm.initiate(); // Process some events ... cout << "trigger event 'Event1'" << endl; sm.process_event(Event1()); cout << "trigger event 'Event2'" << endl; sm.process_event(Event2()); return 0; } #include "FSMSimple.h" #include <iostream> using namespace std; // The FSM void FSMSimple::action1(const Event1 & /*e*/) { cout << "process action 'action1'" << endl; } void FSMSimple::action2(const Event2 & /*e*/) { cout << "process action 'action2'" << endl; } void FSMSimple::action3(const Event2 & /*e*/) { cout << "process action 'action3'" << endl; } bool FSMSimple::guard1() { cout << "process guard 'guard1'" << endl; return true; } // FSM state 'StateA' StateA::StateA() { cout << "enter state 'StateA'" << endl; } StateA::~StateA() { cout << "leave state 'StateA'" << endl; } // FSM state 'StateB' StateB::StateB() { cout << "enter state 'StateB'" << endl; } StateB::~StateB() { cout << "leave state 'StateB'" << endl; } sc::result StateB::react(const Event2 & e) { if (context<FSMSimple>().guard1()) { context<FSMSimple>().action3(e); return transit<StateC>(); } else { context<FSMSimple>().action2(e); return transit<StateA>(); } } // FSM state 'StateC' StateC::StateC() { cout << "enter state 'StateC'" << endl; } StateC::~StateC() { cout << "leave state 'StateC'" << endl; } #ifndef FSMSIMPLE_H #define FSMSIMPLE_H #include <iostream> #include <boost/mpl/list.hpp> #include <boost/statechart/event.hpp> #include <boost/statechart/state_machine.hpp> #include <boost/statechart/simple_state.hpp> #include <boost/statechart/custom_reaction.hpp> #include <boost/statechart/transition.hpp> namespace mpl = boost::mpl; namespace sc = boost::statechart; // FSM events struct Event1 : sc::event<Event1> { Event1() { std::cout << "process event 'Event1'" << std::endl; } }; struct Event2 : sc::event<Event2> { Event2() { std::cout << "process event 'Event2'" << std::endl; } }; // FSM initial state struct StateA; // The FSM struct FSMSimple : sc::state_machine<FSMSimple, StateA> { void action1(const Event1 & e); void action2(const Event2 & e); void action3(const Event2 & e); bool guard1(); }; // FSM states (forward declarations) struct StateA; struct StateB; struct StateC; // FSM states struct StateA : sc::simple_state<StateA, FSMSimple> { typedef mpl::list< sc::transition<Event1, StateB, FSMSimple, &FSMSimple::action1> > reactions; StateA(); ~StateA(); }; struct StateB : sc::simple_state<StateB, FSMSimple> { typedef mpl::list< sc::custom_reaction<Event2> > reactions; StateB(); ~StateB(); sc::result react(const Event2 & e); }; struct StateC : sc::simple_state<StateC, FSMSimple> { typedef mpl::list< > reactions; StateC(); ~StateC(); }; #endif // FSMSIMPLE_H enter state 'StateA' trigger event 'Event1' process event 'Event1' leave state 'StateA' process action 'action1' enter state 'StateB' trigger event 'Event2' process event 'Event2' process guard 'guard1' process action 'action3' leave state 'StateB' enter state 'StateC' leave state 'StateC'

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