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[uBLAS] Expert Developer Advice Needed ... Maybe...
by dmatt001 27 May '03

27 May '03

Hi Guys, After a significantly long break from using uBLAS, I have now been lucky enough to find myself in a new role where I can again use it! Having noted that there was no vector cross product in uBLAS, I thought I would implement my own. To make it really efficient and work in with the other uBLAS features, I thought I would try to make a compatible routine that eliminates temporaries and uses the other cool uBLAS features. So far so good. To start, I decided to use a simple case that I could easily check: a 3d vector. I also decided to copy some other routines as required to get going. For this reason I copied "scalar_plus". Now that I have written the short piece code, it doesn't quite get there. So far not so good. ;-) I am hoping that a reader please review the short code and output below and give some quick pointers about what I can do better...? Perhaps I need to get some better knowledge about the relevant tricks -- I was hoping to emulate another developer in the first instance. Thanks, Matt --- Code Follows --- namespace boost { namespace numeric { namespace ublas { // Binary returning vector template<class T1, class T2> struct vector_vector_binary_functor { typedef std::size_t size_type; typedef std::ptrdiff_t difference_type; typedef typename promote_traits<T1, T2>::promote_type promote_type; typedef promote_type value_type; typedef vector<promote_type> result_type; }; template<class T1, class T2> struct vector_vector_prod: public vector_vector_binary_functor<T1, T2> { typedef typename vector_vector_binary_functor<T1, T2>::size_type size_type; typedef typename vector_vector_binary_functor<T1, T2>::difference_type difference_type; typedef typename vector_vector_binary_functor<T1, T2>::value_type value_type; typedef typename vector_vector_binary_functor<T1, T2>::result_type result_type; template<class E1, class E2> BOOST_UBLAS_INLINE result_type operator () (const vector_expression<E1> &e1, const vector_expression<E2> &e2) const { // why use t() and e1() ? result_type t(3); t () (0) = e1 () (1) * e2 () (2) - e2 () (1) * e1 () (2); t () (1) = - e1 () (0) * e2 () (2) + e2 () (0) * e1 () (2); t () (2) = e1 () (0) * e2 () (1) - e2 () (0) * e1 () (1); return t; } }; template<class E1, class E2> BOOST_UBLAS_INLINE typename vector_binary_traits<E1, E2, vector_vector_prod<typename E1::value_type, typename E2::value_type> >::result_type vect_prod(const vector_expression<E1> &e1, const vector_expression<E2> &e2) { typedef typename vector_binary_traits<E1, E2, vector_vector_prod<typename E1::value_type, typename E2::value_type> >::expression_type expression_type; return expression_type(e1 (), e2 ()); } } } } --- Error Follows --- /home/matt/code/c++/pkg/boost_1_30_0/boost/numeric/ublas/functional.hpp: In member function `void boost::numeric::ublas::scalar_assign<T1, T2>::operator()(boost::numeric::ublas::scalar_binary_assign_functor<T1, T2>::argument1_type, boost::numeric::ublas::scalar_binary_assign_functor<T1, T2>::argument2_type) const [with T1 = double, T2 = boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> >]': /home/matt/code/c++/pkg/boost_1_30_0/boost/numeric/ublas/vector_assign.hpp:252: instantiated from `void boost::numeric::ublas::indexing_vector_assign(const F&, V&, const boost::numeric::ublas::vector_expression<E>&) [with F = boost::numeric::ublas::scalar_assign<double, boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> > >, V = boost::numeric::ublas::vector<double, boost::numeric::ublas::bounded_array<double, 3> >, E = boost::numeric::ublas::vector<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> >, boost::numeric::ublas::unbounded_array<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> > > >]' /home/matt/code/c++/pkg/boost_1_30_0/boost/numeric/ublas/vector_assign.hpp:266: instantiated from `void boost::numeric::ublas::vector_assign(const F&, V&, const boost::numeric::ublas::vector_expression<E>&, boost::numeric::ublas::dense_proxy_tag) [with F = boost::numeric::ublas::scalar_assign<double, boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> > >, V = boost::numeric::ublas::vector<double, boost::numeric::ublas::bounded_array<double, 3> >, E = boost::numeric::ublas::vector<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> >, boost::numeric::ublas::unbounded_array<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> > > >]' /home/matt/code/c++/pkg/boost_1_30_0/boost/numeric/ublas/vector_assign.hpp:423: instantiated from `void boost::numeric::ublas::vector_assign(const F&, V&, const boost::numeric::ublas::vector_expression<E>&) [with F = boost::numeric::ublas::scalar_assign<double, boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> > >, V = boost::numeric::ublas::vector<double, boost::numeric::ublas::bounded_array<double, 3> >, E = boost::numeric::ublas::vector<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> >, boost::numeric::ublas::unbounded_array<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> > > >]' /home/matt/code/c++/pkg/boost_1_30_0/boost/numeric/ublas/vector.hpp:77: instantiated from `boost::numeric::ublas::vector<T, A>::vector(const boost::numeric::ublas::vector_expression<E>&) [with AE = boost::numeric::ublas::vector<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> >, boost::numeric::ublas::unbounded_array<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> > > >, T = double, A = boost::numeric::ublas::bounded_array<double, 3>]' src/GLWireVisitor/GLWireVisitor.cpp:121: instantiated from here /home/matt/code/c++/pkg/boost_1_30_0/boost/numeric/ublas/functional.hpp:182: cannot convert `const boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> >' to `double' in assignment /home/matt/code/c++/pkg/boost_1_30_0/boost/numeric/ublas/vector_expression.hpp: In member function `F::result_type boost::numeric::ublas::vector_binary<E1, E2, F>::operator()(boost::numeric::ublas::promote_traits<E1::size_type, E2::size_type>::promote_type) const [with E1 = boost::numeric::ublas::vector<double, boost::numeric::ublas::bounded_array<double, 3> >, E2 = boost::numeric::ublas::vector<double, boost::numeric::ublas::bounded_array<double, 3> >, F = boost::numeric::ublas::vector_vector_prod<double, double>]': /home/matt/code/c++/pkg/boost_1_30_0/boost/numeric/ublas/vector_assign.hpp:252: instantiated from `void boost::numeric::ublas::indexing_vector_assign(const F&, V&, const boost::numeric::ublas::vector_expression<E>&) [with F = boost::numeric::ublas::scalar_assign<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> >, boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> > >, V = boost::numeric::ublas::vector<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> >, boost::numeric::ublas::unbounded_array<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> > > >, E = boost::numeric::ublas::vector_binary<boost::numeric::ublas::vector<double, boost::numeric::ublas::bounded_array<double, 3> >, boost::numeric::ublas::vector<double, boost::numeric::ublas::bounded_array<double, 3> >, boost::numeric::ublas::vector_vector_prod<double, double> >]' /home/matt/code/c++/pkg/boost_1_30_0/boost/numeric/ublas/vector_assign.hpp:266: instantiated from `void boost::numeric::ublas::vector_assign(const F&, V&, const boost::numeric::ublas::vector_expression<E>&, boost::numeric::ublas::dense_proxy_tag) [with F = boost::numeric::ublas::scalar_assign<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> >, boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> > >, V = boost::numeric::ublas::vector<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> >, boost::numeric::ublas::unbounded_array<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> > > >, E = boost::numeric::ublas::vector_binary<boost::numeric::ublas::vector<double, boost::numeric::ublas::bounded_array<double, 3> >, boost::numeric::ublas::vector<double, boost::numeric::ublas::bounded_array<double, 3> >, boost::numeric::ublas::vector_vector_prod<double, double> >]' /home/matt/code/c++/pkg/boost_1_30_0/boost/numeric/ublas/vector_assign.hpp:423: instantiated from `void boost::numeric::ublas::vector_assign(const F&, V&, const boost::numeric::ublas::vector_expression<E>&) [with F = boost::numeric::ublas::scalar_assign<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> >, boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> > >, V = boost::numeric::ublas::vector<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> >, boost::numeric::ublas::unbounded_array<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> > > >, E = boost::numeric::ublas::vector_binary<boost::numeric::ublas::vector<double, boost::numeric::ublas::bounded_array<double, 3> >, boost::numeric::ublas::vector<double, boost::numeric::ublas::bounded_array<double, 3> >, boost::numeric::ublas::vector_vector_prod<double, double> >]' /home/matt/code/c++/pkg/boost_1_30_0/boost/numeric/ublas/vector.hpp:77: instantiated from `boost::numeric::ublas::vector<T, A>::vector(const boost::numeric::ublas::vector_expression<E>&) [with AE = boost::numeric::ublas::vector_binary<boost::numeric::ublas::vector<double, boost::numeric::ublas::bounded_array<double, 3> >, boost::numeric::ublas::vector<double, boost::numeric::ublas::bounded_array<double, 3> >, boost::numeric::ublas::vector_vector_prod<double, double> >, T = boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> >, A = boost::numeric::ublas::unbounded_array<boost::numeric::ublas::vector<double, boost::numeric::ublas::unbounded_array<double> > >]' src/GLWireVisitor/GLWireVisitor.cpp:70: instantiated from `boost::numeric::ublas::vector_binary_traits<E1, E2, boost::numeric::ublas::vector_vector_prod<E1::value_type, E2::value_type> >::result_type boost::numeric::ublas::vect_prod(const boost::numeric::ublas::vector_expression<E>&, const boost::numeric::ublas::vector_expression<E2>&) [with E1 = boost::numeric::ublas::vector<double, boost::numeric::ublas::bounded_array<double, 3> >, E2 = boost::numeric::ublas::vector<double, boost::numeric::ublas::bounded_array<double, 3> >]' src/GLWireVisitor/GLWireVisitor.cpp:121: instantiated from here /home/matt/code/c++/pkg/boost_1_30_0/boost/numeric/ublas/vector_expression.hpp:775: no match for call to `(boost::numeric::ublas::vector_vector_prod<double, double>) (double, double)' make: *** [obj/GLWireVisitor/GLWireVisitor.o] Error 1

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Nesting Grammars with boost::spirit
by Dan Nuffer 27 May '03

27 May '03

I have two grammars defined (value and variable). I'll paste value here, variable is very similar: struct value : public grammar<value> { template <typename ScannerT> struct definition { definition(value const &self) { val = real_p[&do_real] | ('-' >> val)[&do_neg] | '+' >> val; } rule<ScannerT> val; rule<ScannerT> const &start() const { return val; } }; }; Now I want to define a grammar that uses both of these, for instance part of it might be (value | variable)... how can I do this? Thanks. _____________________________________________________________ <a href="http://www.gamedev.net">GameDev.net Email Service</a> - "Plenty of 1's and 0's" _____________________________________________________________ Select your own custom email address for FREE! Get you(a)yourchoice.com w/No Ads, 6MB, POP & more! http://www.everyone.net/selectmail?campaign=tag

1 0

boost::date_time::posix_time and Intel Compiler 7.0?
by Andre du Toit 26 May '03

26 May '03

Hi there. I get the following error when I try to compile code using boost::date_time::posix_time: c:\PROGRAM FILES\BOOST_1_30_0\boost/date_time/posix_time/time_formatters.hpp(43): error: more than one operator "<<" matches these operands: function "std::basic_ostream<_E, _Tr>::operator<<(std::_Bool={bool={bool}}) [with _E=char, _Tr=std::char_traits<char>]" function "std::basic_ostream<_E, _Tr>::operator<<(short) [with _E=char, _Tr=std::char_traits<char>]" function "std::basic_ostream<_E, _Tr>::operator<<(unsigned short) [with _E=char, _Tr=std::char_traits<char>]" function "std::basic_ostream<_E, _Tr>::operator<<(int) [with _E=char, _Tr=std::char_traits<char>]" function "std::basic_ostream<_E, _Tr>::operator<<(unsigned int) [with _E=char, _Tr=std::char_traits<char>]" function "std::basic_ostream<_E, _Tr>::operator<<(long) [with _E=char, _Tr=std::char_traits<char>]" function "std::basic_ostream<_E, _Tr>::operator<<(unsigned long) [with _E=char, _Tr=std::char_traits<char>]" function "std::basic_ostream<_E, _Tr>::operator<<(float) [with _E=char, _Tr=std::char_traits<char>]" function "std::basic_ostream<_E, _Tr>::operator<<(double) [with _E=char, _Tr=std::char_traits<char>]" function "std::basic_ostream<_E, _Tr>::operator<<(long double) [with _E=char, _Tr=std::char_traits<char>]" operand types are: std::basic_ostream<char, std::char_traits<char>> << boost::posix_time::time_duration::fractional_seconds_type << frac_sec; Looking at the offending file (time_formatters.hpp, line 43 and vicinity) gives: #if (defined(BOOST_MSVC) && (_MSC_VER <= 1200)) // 1200 == VC++ 6.0 boost::int64_t frac_sec = td.fractional_seconds(); // JDG [7/6/02 VC++ compatibility] char buff[32]; _i64toa(frac_sec, buff, 10); #else time_duration::fractional_seconds_type frac_sec = td.fractional_seconds(); #endif if (frac_sec != 0) { ss << "." << std::setw(time_duration::num_fractional_digits()) << std::setfill('0') // JDG [7/6/02 VC++ compatibility] #if (defined(BOOST_MSVC) && (_MSC_VER <= 1200)) // 1200 == VC++ 6.0 << buff; #else << frac_sec; //!!! Line 43 !!!// #endif It appears that there is not a streaming operator defined for the time_duration::fractional_seconds_type type. Looking deeper into this issue was a bit of nightmare; since the offending type consists of numerous nested typdefs etc. etc. If anyone has a short and sweet answer to my essay of a question, I would appreciate it. The obvious answer of "don't use the Intel compiler" will not suffice! Saying that, when I switched from the Intel compiler to bad old MSVC6 I had not problems. But our company's software requires the performance gain provided by the Intel compiler on Windows. Another issue, I saw that during installation of Boost, it is possible using STLPort and MSVC6 together, but (for the reasons mentioned above), why not STLPort with the Intel compiler? I did ask the same question some time before now, but no-one bothered to answer. I would really appreciate any help in this regard! Greetings, Andre.

5 10

ublas test with cwpro8
by Benedikt Weber 24 May '03

24 May '03

Hi I tried to run the tests for ublas with cwpro8 on Window 2000: D:\boost\boost_1_30_0\libs\numeric\ublas\test2>bjam -sTOOLS=cwpro8 The compiler (Codewarrior) has problems with the boost include files. Includes like #include <boost/numeric/ublas/io.hpp> work only with the system path and not with the user path. When I change <include>$(BOOST_ROOT) in the jamfile to <sysinclude>$(BOOST_ROOT) the problem disappears (but would possibly not work for other compilers). Benedikt

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Boost::signal compil error under Visual studio 6
by georges_torres2003 24 May '03

24 May '03

Hello, I've got a problem using the signal library, receiving this compiler error: F:\LIBSPC\BOOST\boost/iterator_adaptors.hpp(872) : fatal error C1001: INTERNAL COMPILER ERROR (compiler file 'msc1.cpp', line 1794) Please choose the Technical Support command on the Visual C++ Help menu, or open the Technical Support help file for more information F:\LIBSPC\BOOST\boost/signals/signal_template.hpp(303) : see reference to class template instantiation 'boost::iterator_adaptor<struct _STL::_Rb_tree_iterator<struct _STL::pair<class boost::any const ,struct boost::signals::detail::conn ection_slot_pair>,struct _STL::_Nonconst_traits<struct _STL::pair<class boost::any const ,struct boost::signals::detail::connection_slot_pair> > >,class boost::signals::detail::slot_call_policies<struct boost::signals::detail::call_bound2<bool>::cal ler<int,int,class boost::function2<bool,int,int,int> >,struct _STL::_Rb_tree_iterator<struct _STL::pair<class boost::any const ,struct boost::signals::detail::connection_slot_pair>,struct _STL::_Nonconst_traits<struct _STL::pair<class boost::any con st ,struct boost::signals::detail::connection_slot_pair> > > >,bool,bool &,bool *,struct _STL::input_iterator_tag,struct boost::detail::default_argument>' being compiled I'm just sending a signal at this line, as follow: // i_x and i_y are ints MouseSignalLClick(i_x, i_y); MouseSignalLClick is member of a class, defined as follow: boost::signal2<bool,int,int> MouseSignalLClick; I'm using Boost library version 1.30, and visual sp5. Thanks.

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Policy based threading question
by Aschwin Gopalan 24 May '03

24 May '03

Dear Boosters! I am designing a class template with policy controled threading behaviour, like template<ThreadingModel=SingleThreaded> class Something; where there are different ThreadingModels available (see Modern C++ Design by Alexandrescu for a discussion of policies). I would like to have Something to inherit ThreadingModel. The idea is that SingleThreaded does not impose any additional penalties. So my Idea was to have something like class SingleThreaded { public: void lock() {} void release() {} } class MultiThreaded { public: void lock() { lock_mutex(m_mutex) } void release() { release_mutex(m_mutex) } private: mutex m_mutex; } and have all functions call lock() and release() accordingly. But this is not good, since it does not use Resource Initialization is Aquisition and leads to exeption safety problems and so on. Furthermore, it is not (because of these reasons) possible to model using boost::mutex ´es since they do not expose a lock() release() interface but can only be locked using scoped_locks. So another idea is to have something like class SingleThreaded { class scoped_lock { // Empty class } } class MultiThreaded { public: class scoped_lock { scoped_lock() // constructor that locks m_mutex of // of MultiThreaded ~scoped_lock() // unlocks } private: boost::mutex m_mutex; } and have the member functions lock the mutex by instantiating an embeded scoped_lock object. Now there are some questions I have: 1.) Does this approach sound sensible, or am I overlooking a commonly used Idiom to achieve this functionality 2.) How can I access the m_mutex member of the right object in scoped_lock()? The only way I can imagin is to give the this pointer to the constructor (like scoped_lock lock(this);). It is somehow not nice, but possible 3.) The actual code I am using looks like //! Policy class. /*! Multithreading, object operations are synchronized via * a non-recursive lock, obeying strict Resource Acuisition is Initialization * semantics */ class LockDefault { public: LockDefault() : m_pmutex(new boost::mutex) { } class scoped_lock : public boost::mutex::scoped_lock { public: scoped_lock(LockDefault &obj) : boost::mutex::scoped_lock(obj->m_pmutex) { } ~scoped_lock() { } }; public: boost::mutex m_mutex; }; This works with gcc and I think it does what it should. It fails to compile with VC++6 giving error C2512: 'scoped_lock<class boost::recursive_mutex>' : no appropriate default constructor which I do not understand, since the default constructor is never called. Also, I do not like to have the mutex member public, but if I make it private and write friend class scoped_lock; this does not have the desired effect (MSVC still complains about private data member access) Somehow, I must be getting something completely wrong, so if somebody could point me in the right direction, I would be thankful. BTW: I am using boost_1_30_0 Thanks, Aki

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newbie: trouble composing with boost::bind
by Jacques A. Vidrine 23 May '03

23 May '03

Hello, I'm new to the Boost library and quite excited to see some of the tools available to assist writing functional-style code. Recently I wanted to perform an action on every object in a container of smart pointers (boost::shared_ptr). I couldn't seem to find a concise way to do so. Here is a small example (no container involved) demonstrating the problem I'm encountering. #include <iostream> #include <string> #include <boost/shared_ptr.hpp> #include <boost/bind.hpp> using namespace std; using namespace boost; void xprint(ostream *os, shared_ptr<string> p) { *os << p.get()->c_str() << endl; } void xprint2(ostream *os, string *p) { *os << p->c_str() << endl; } int main(int ac, char *av[]) { shared_ptr<string> p(new string("Test")); bind(xprint, &cerr, _1)(p); #ifdef THIS_DOES_NOT_WORK bind(xprint2, &cerr, _1)( bind(&shared_ptr<string>::get, _1)(p) ); #else string *q = bind(&shared_ptr<string>::get, _1)(p); bind(xprint2, &cerr, _1)(q); #endif return 0; } Using GCC 3.2, I encounter a `no match for call' error in the `THIS_DOES_NOT_WORK' section of code. (Full diagnostics below.) I have tried many variations using mem_fn, apply, and by specifying the return type of the functor explicitly, but with no success. I'm afraid I don't understand the problem. I hoped someone here might be able to hit me with a clue-stick :-) Cheers, -- Jacques Vidrine . NTT/Verio SME . FreeBSD UNIX . Heimdal nectar(a)celabo.org . jvidrine(a)verio.net . nectar(a)freebsd.org . nectar(a)kth.se g++ -DTHIS_DOES_NOT_WORK -I/usr/local/include example.cc example.cc: In function `int main(int, char**)': example.cc:31: no match for call to `(boost::_bi::bind_t<void, void (*)(std::ostream*, std::string*), boost::_bi::list2<boost::_bi::value<std::ostream*>, boost::arg<1> > >) ( std::string*)' /usr/local/include/boost/bind/bind_template.hpp:19: candidates are: boost::_bi::result_traits<R, F>::type boost::_bi::bind_t<R, F, L>::operator()() [with R = void, F = void (*)(std::ostream*, std::string*), L = boost::_bi::list2<boost::_bi::value<std::ostream*>, boost::arg<1> >] /usr/local/include/boost/bind/bind_template.hpp:25: boost::_bi::result_traits<R, F>::type boost::_bi::bind_t<R, F, L>::operator()() const [with R = void, F = void (*)(std::ostream*, std::string*), L = boost::_bi::list2<boost::_bi::value<std::ostream*>, boost::arg<1> >] /usr/local/include/boost/bind/bind_template.hpp:31: boost::_bi::result_traits<R, F>::type boost::_bi::bind_t<R, F, L>::operator()(A1&) [with A1 = std::string*, R = void, F = void (*)(std::ostream*, std::string*), L = boost::_bi::list2<boost::_bi::value<std::ostream*>, boost::arg<1> >] /usr/local/include/boost/bind/bind_template.hpp:37: boost::_bi::result_traits<R, F>::type boost::_bi::bind_t<R, F, L>::operator()(A1&) const [with A1 = std::string*, R = void, F = void (*)(std::ostream*, std::string*), L = boost::_bi::list2<boost::_bi::value<std::ostream*>, boost::arg<1> >]

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any_cast<double>(any_assigned_with_int) fails. workaround?
by Markus Werle 23 May '03

23 May '03

Hi! At present I learn what it means not to have strong typing: I play around with boost::any. A new and healing experience. Thank You, Bjarne, for insisting on strong typing for C++ ;-) Never made so much use of the debugger ... So now I found out that any_cast does not promote types that may be promoted like for int->double conversions. Any workaround in the lib I overlooked or is this the time for my_any_cast<T>(boost::any const &)? Markus -- Compile time analytic differentiation? Yes, at http://daixtrose.sourceforge.net/

1 0

question about boost::bind
by Darin Buck 23 May '03

23 May '03

First, the working code: #include <boost/bind.hpp> #include <boost/function.hpp> #include <iostream> #include <string> #include <map> using namespace std; struct message { string mtablename; unsigned long long mpk; message(const string& tablename, const unsigned long long pk) : mtablename(tablename), mpk(pk) { } }; typedef boost::function < void, unsigned long long > MessageFunctor; typedef multimap < string, MessageFunctor > MessageFunctorMap; typedef pair < MessageFunctorMap::iterator, MessageFunctorMap::iterator > MessageFunctorTableMapIteratorPair; void callfunctor(pair < string, MessageFunctor > item, unsigned long long pk) { item.second(pk); } class MessageCenter { MessageFunctorMap mHandlerMap; public: MessageCenter() { } void sendMessage(message& amessage) { MessageFunctorTableMapIteratorPair iterPair = mHandlerMap.equal_range(amessage.mtablename); std::for_each(iterPair.first, iterPair.second, boost::bind (&callfunctor, _1, amessage.mpk)); // QUESTION LINE } void addHandler(string tableName, MessageFunctor handler) { mHandlerMap.insert(make_pair(tableName, handler)); } }; int gFooCounter = 0; void fooHandler(unsigned long long x) { cout << "fooHandler called on pk=" << x << endl; gFooCounter++; } void gooHandler(unsigned long long x){} int main(int argc, const char** argv) { MessageCenter messageCenter; messageCenter.addHandler("foo", fooHandler); messageCenter.addHandler("foo", fooHandler); messageCenter.addHandler("goo", gooHandler); // send some messages message fooMessage("foo", 123); messageCenter.sendMessage(fooMessage); if(gFooCounter != 2) cerr << "something didn't work"; else cout << "everything worked..." << endl; return 0; } now for the question: on the line labeled "QUESTION LINE", you can see that I'm binding to a functor called "callfunctor". All callfunctor does is call the functor embedded in the map's pair. Is there a way to simplify the line in question so that I don't need to create the functor just to get access to the pair.second member? -Darin

2 1

smart pointer into classes this
by Erik Thiele 23 May '03

23 May '03

hi i use my own smartpointer class but hope to consolidate it into some other standard class some day (like the boost smart_ptr). an open point is the "this" pointer in classes. i have a problem with this situation: class myclass { void foo (); }; void myclass::foo() { // i do not know, if there is a smartpointer on me. // in some situations i'd like to have it! // that's why "this" exists, but "this" is not a // smartpointer! so either i have to get it in my // parameter list, or i have to be derived from // some "smartpointable" base class and call the // thissmartptr() member function. // but how should i implement the "thissmartptr" function? // in the class construction, nobody gets the smartpointer. } void main() { // sp is the smartpointer sp<myclass> m (new myclass()); // does this kind of initialisation still work // when the thissmartptr stuff shall be implemented? } i have no clue on how to implement the thissmartptr problem. my problems are class construction. do you have any plans, or is it even already implemented in the smart_ptr? cu & thx erik -- Erik Thiele

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