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boost::iterator_adaptor
by Grisha Spivak 14 May '06

14 May '06

Hi, here is small code snippet to demonstrate my problrm: #include <stddef.h> #include <iostream> #include <boost/iterator/iterator_adaptor.hpp> template<typename T, size_t stride> class stride_iterator : public boost::iterator_adaptor<stride_iterator<T, stride>, T*> { public: stride_iterator() : stride_iterator::iterator_adaptor_( 0 ) { } explicit stride_iterator( T * p ) : stride_iterator::iterator_adaptor_( p ) { } private: friend class boost::iterator_core_access; void increment() { this->base_reference() = this->base() + stride; } void deccrement() { this->base_reference() = this->base() - stride; } void advance( ptrdiff_t d ) { this->base_reference() = this->base() + d*stride; } ptrdiff_t distance_to( stride_iterator const & i ) const { return ( i.base() - this->base() )/stride; } }; int main() { int arr[12] = {}; arr[3*2] = 33; arr[5*2] = 55; stride_iterator<int, 2> it( arr ); it[2] = -22; it[3] = it[5]; std::cout << arr[2*2] << ' ' << arr[3*2] << ' ' << arr[5*2] << '\n'; return 0; } It prints "-22 33 55" instead of "-22 55 55" (which I expected) - so "it[3] = it[5];" assignment didn't modifies array. Is it intended behaviour? Or maybe I'm doing something wrong?

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newbie - boost::shared_ptr of type stringstream using << operator?
by Ed Johnson 14 May '06

14 May '06

Hi, Is it possible to use shared_ptr to manage stringstreams, and still use the << operator on the stringstream? example: #include <iostream> boost::shared_ptr< std::stringstream > sharedStream(new std::stringstream("hello world")); std::cerr << (*sharedStream).str() << std::endl; (*sharedStream) << "!"; std::cerr << (*sharedStream).str() << std::endl; std::stringstream tr; tr << "hello everyone"; tr << "!"; std::cerr << tr.str() << std::endl; output: hello world !elloworld hello everyone! Thanks, Ed Johnson

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[review] Fusion review begins
by Ronald Garcia 14 May '06

14 May '06

The review of Joel de Guzman's Fusion library begins today, May 1, 2006, and continues through May 10, 2006. :Download: http://spirit.sourceforge.net/dl_more/fusion_v2.zip :Description: Fusion is a library of heterogenous containers and views and algorithms. A set of heterogenous containers (vector, list, set and map) is provided out of the box along with view classes that present various composable views over the data. The containers and views follow a common sequence concept with an underlying iterator concept that binds it all together, suitably making the algorithms fully generic over all sequence types. The architecture is somewhat modeled after MPL which in turn is modeled after STL. It is code-named "fusion" because the library is the "fusion" of compile time metaprogramming with runtime programming. Review questions ================ Please always explicitly state in your review, whether you think the library should be accepted into Boost. You might want to comment on the following questions: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? Cheers, Ron

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Re: [Boost-users] [multi_index] thread safety
by Patel Priyank-PPATEL1 13 May '06

13 May '06

Hi Joaquin, I have to use actually two or more threads on procedure pool. I start seeing same Problem when I have three/four threads working on same procedure pool. I tried to introduce mutex (ACE_Guard) but still having problems in execution in one/two minute of execution. Seems I am guarding every method that is used by container. Anything wrong with the Following code? Thanks Priyank #ifndef PROCEDURE_POOL_H #define PROCEDURE_POOL_H /** * Identifier pool of procedure. This procedure will be un-sorted * hashed index provided by procedures unique id retuned by procedure. * It internally uses boost hashed index for indexing the procedures * in procedure pool. * * @author Priyank Patel * @since Mar 30, 2006 */ #include <ace/Mutex.h> #include <boost/multi_index_container.hpp> #include <boost/multi_index/member.hpp> #include <boost/multi_index/ordered_index.hpp> #include <boost/multi_index/hashed_index.hpp> #include <boost/config.hpp> #include <boost/utility.hpp> #include <boost/shared_ptr.hpp> #include <boost/multi_index/key_extractors.hpp> #include "Procedure.h" using boost::multi_index_container; using namespace boost::multi_index; /** * Defines tag used for procedure id. */ struct procedure_id_tag { }; class Procedure_Pool: boost::noncopyable { private: /** * Type definition for multi index container. */ typedef multi_index_container< Procedure*, indexed_by< hashed_unique< tag<procedure_id_tag>, const_mem_fun<Procedure, int, &Procedure::id> > > > Procedure_Hashed_Pool; /** * Type definition for indexing based on procedure id tag. */ typedef Procedure_Hashed_Pool::index<procedure_id_tag>::type Procedure_By_Id; public: /** * Constructor. */ Procedure_Pool(): pool_(), procedure_by_id_(pool_.get<procedure_id_tag>()) { } /** * Adds specified procedure in this pool. * It will intenally used procedures id() method to index procedure. * @param _procedure Procedure to be added in this pool * @return Success (0) or Failure (-1) based on addition happened or not */ int add_by_id(Procedure * _procedure); /** * Removes procedure from this pool. * @param _procedure procedure that needs to be removed * @return Success (0) or Failure (1) based on removal happend or not */ int remove_by_id(Procedure * _procedure); /** * Retrieves procedure based on specified id. * @param _id Identifier * @return Procedure Pointer to procedure. Returns 0 if procedure not found */ Procedure * find_by_id(int _id); private: /** * Returns true if procedure is present otherwise returns false. * @param _procedure procedure that needs to found * @return true if found or false if not found */ //bool find_by_id(Procedure * _procedure); /** * boost multiindex object that is associated with this pool. */ Procedure_Hashed_Pool pool_; /** * Refernece of pool that is indexed by procedure id tag. */ Procedure_By_Id &procedure_by_id_; ACE_Mutex mutex_; }; #endif //===============================================================================/// #include "../include/Procedure_Pool.h" int Procedure_Pool::add_by_id(Procedure * _procedure) { LD_TRACE("Procedure_Pool::add_by_id"); ACE_ASSERT(_procedure != 0); ACE_DEBUG((LM_DEBUG, "ADDING %d\n", _procedure->id())); if (find_by_id(_procedure->id()) == 0) { ACE_Guard<ACE_Mutex> guard(mutex_); { // procedure not found procedure_by_id_.insert(_procedure); } // debug info ACE_DEBUG((LM_DEBUG, "Added procedure : %d \n", _procedure->id())); // return success return 0; } else { // error ACE_ERROR((LD_ERROR "%N:%l Error in adding procedure : %d \n", _procedure->id())); // return failure return -1; } } int Procedure_Pool::remove_by_id(Procedure * _procedure) { LD_TRACE("Procedure_Pool::remove_by_id"); ACE_ASSERT(_procedure != 0); ACE_DEBUG((LM_DEBUG, "REMOVING: %d \n", _procedure->id())); if (find_by_id(_procedure->id()) != 0) { ACE_Guard<ACE_Mutex> guard(mutex_); { // procedure found procedure_by_id_.erase(_procedure->id()); } ACE_DEBUG((LM_DEBUG, "Removed procedure : %d \n", _procedure->id())); return 0; } else { ACE_ERROR((LD_ERROR "%N:%l Error in removing procedure : %d \n", _procedure->id())); return -1; } } Procedure * Procedure_Pool::find_by_id(int _id) { LD_TRACE("Procedure_Pool::find_by_id"); ACE_Guard<ACE_Mutex> guard(mutex_); { Procedure_By_Id::iterator it = procedure_by_id_.find(_id); if (it != procedure_by_id_.end()) { ACE_DEBUG((LM_DEBUG, "%N:%l Found procedure for id: %d \n", _id)); return *it; } } ACE_DEBUG((LM_DEBUG, "%N:%l Not able to found procedure for id: %d \n", _id)); // return null return 0; } -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of JOAQUIN LOPEZ MU?Z Sent: Thursday, May 11, 2006 2:12 PM To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [multi_index] thread safety ----- Mensaje original ----- De: george <george13p(a)yahoo.com> Fecha: Jueves, Mayo 11, 2006 7:27 pm Asunto: Re: [Boost-users] [multi_index] thread safety > hello Joaquin Hello George, > > > You have to lockguard every access to the container; note this also > > includes, for instance, container traversal with iterators, i.e. > > iterator displacement. Strictly speaking, iterator dereference > > should also be lockguarded, although I can say unofficially that > > unguarded dereference is OK. > > can you explain a litle more? > as I konw from STL, multiple readers is ok. Correct. > reading and inserting a new object does't invalidate iterators(for > pointer-based conteiners offcourse,list, map etc...) Correct. This also holds for multi_index_containers. > > a concurrent read and insert in multi_index are not (safely)possible? > I mean there might be an iterator invalidation? Concurrent reading and writing is not safe, but the issue has nothing to do with iterator invalidation. ...I think I've got a hunch about what you've got in mind. When I say that you've got to lockguard iterator displacement, what I mean is: consider a concurrent write operation and an iterator increment; this concurrency is not thread safe and undefined behavior results: a possible outcome is iterator invalidation, but you could also get an app crash, a corrupted data structure, an infinite loop or whatever. Tecnhically speaking, an invalid iterator is a perfectly legal state for an iterator to be in, which has nothing to do with undefined behavior resulting from violating thread safety guarantees. I'm not sure I made myself clear :) Insist on me if I didn't. > offcourse there is a chance for a 'dirty-read' but this for the domain > of the aplication if it is a problem and not for multi_index. I don't get what you mean here, would you care to elaborate? Joaquín M López Muñoz Telefónica, Investigación y Desarrollo _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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boost::bind, boost::function & placeholders flexibility
by jbd 13 May '06

13 May '06

Hello everybody, First of all, i'm a beginner trying to understand the use of the boost::bind library. Here is my problem : I'd like to know if there is a way to omit placeholders when calling boost::bind and let the compiler deduce their number. I understand that this is contrary to the flexibility offers by the placeholder, but i need to do something like that. void bar() {} void bar2(int) {} // Compile and works well boost::function < void ()> f1( boost::bind(&bar) ) ; boost::function < void (int) > f2( boost::bind(&bar2,_1) ) ; // i'd like to write this, but it doesn't compile // without the placeholders boost::function < void (int) > f2( boost::bind(&bar2) ) ; // i can write a small helper function mybind to achieve my goal // this compile and works well mybind(bar2) ; with template <typename Ret, typename Arg1, typename Arg2> void mybind(Ret (*Func)(Arg1, Arg2)) { boost::function<Ret (Arg1, Arg2)> f(Func) ; } I hope you understand what i've try to show. Maybe i missed something in the documentation. Thank you for reading ! Here is the working .cpp file i use to test things. =============================== #include <iostream> #include <stdexcept> #include <boost/bind.hpp> #include <boost/function.hpp> template <typename Ret, typename Arg1, typename Arg2> void mybind(Ret (*Func)(Arg1)) { boost::function<Ret (Arg1)> f(Func) ; } void bar() { std::cout << "bar()\n" ; } void bar2(int a) { std::cout << "bar2(int)\n" ; } int main (int argc, char* argv[]) { try { // Compile and works well { boost::function < void ()> f1( boost::bind(&bar) ) ; boost::function < void (int) > f2( boost::bind(&bar2,_1) ) ; } /* // i'd like to write this, but it doesn't compile { // without the placeholders boost::function < void (int) > f2( boost::bind(&bar2) ) ; f2(5) ; } */ // i can write a small helper function mybind to achieve my goal // this compile and works well /* template <typename Ret, typename Arg1, typename Arg2> void mybind(Ret (*Func)(Arg1, Arg2)) { boost::function<Ret (Arg1, Arg2)> f(Func) ; } */ { mybind(bar2) ; } } catch(std::exception& e) { std::cout << e.what() << '\n' ; return -1 ; } catch(...) { std::cout << "Non standard exception\n" ; return -1 ; } } ========================================

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Linking problems with boost::test in multiple modules.
by steve ahlgren 12 May '06

12 May '06

Hello : I am using boost::test to provide testing in multiple modules (dlls on win32). A single exe is used to call each of the test facilities in each module. In theory the above sounds ideal, especially as each individual unit test within a module is registered via an abstract factory. In practice, however, I am unable to link the individual modules properly as each one seems to require the function init_unit_test_suite() to be defined. This is mentioned in the FAQ but I have not yet found documentation or examples documenting boost::test spanning multiple modules. I would think that one instance of init_unit_test_suite() would be necessary within the controlling exe, and that each module (dll) would link statically against the boost::test library. Linking against this library, however, causes the problems described above. If anyone has suggestions or an example I would be grateful. Many thanks; sga

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Re: [Boost-users] [BULK] Re: MPL/Fusion
by Sohail Somani 12 May '06

12 May '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of > Arkadiy Vertleyb > There could be different opinions on this subject, but I > think the basic > rule of thumb should be: no template metaprogramming in the > non-library > code. Of course, most C++ programmers are wearing two hats: a library > (reusable code) writer and the user of this reusable code. > The key is to > distinguish which hat you are wearing at any particular moment :-) I find that increasingly it's the library, so maybe I'm on the right path. Thank you for your input! Sohail

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Re: [Boost-users] MPL/Fusion
by Sohail Somani 12 May '06

12 May '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of > Sohail Somani > Sent: Thursday, May 11, 2006 9:18 AM > To: boost-users(a)lists.boost.org > Subject: [Boost-users] MPL/Fusion > > Hi, > > I am quite interested in MPL/Fusion. I have made my own toy projects > using template metaprogramming to make decisions at compile time. I am > interested in learning what types of software boost users create with > it. > > Would anyone care to share? I think I should clarify: I meant non-library uses (like the maze app, I'll take a look thanks!). Like a programmer who also uses shared_ptr. Although I can think of a few instances where I would use it for work, I just want to tell myself that I am making things complicated and want your help to make sure I'm making better code. Sorry if that's even MORE confusing :) Sohail

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[date_time] Error in time_period documentation
by Ward, Arthur (Mission Systems) 12 May '06

12 May '06

To the documentation maintainers for date_time: I just noticed an error in the documentation for boost::posix_time::time_period in 1.33.1. According to the Posix Time documentation, time_period has the method "time_period shift(days)". As far as I can see, it should be "void shift(days)" and listed as a mutator.

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[Boost.program_options] Boolean option
by Kobi Cohen-Arazi 12 May '06

12 May '06

Hi, boost-1.32.0-6 I've tried to find in the program_options docs how to specify a regular boolean switch. If I use <bool>, it still demand putting something That's what I would like to have ./prog -t and not ./prog -t1 Right now, when using <bool> it will throw an exception if I'm not using the -t1 notation. Am I missing here something? Thanks, Kobi.

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