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[Bind] Does not compile with local classes
by Rudi Dittrich 15 Jul '09

15 Jul '09

Hello, I tried to use a local class as a callback function registering with a boost signal. The example below shall illustrate this scenario. There are two classes: class Foo which triggers a signal when its member function set_k( k ) is called. Each object which wants to receive this signal has to subscribe with it, calling on_k_changed(...). The second class is Bar which has one member function change_k(...). There is a local class KChanged inside this member function. KChanged has one function k_changed(...) which shall be called whenever the signal in Foo is triggered. Thus, it shall act as a callback function. Therefore, I used boost bind with k_changed(...) and tried to register with Foo's signal. After compiling I get the following compilation error: g++ -Wall -o local_class local_class.cpp -lboost_signals In member function ‘void Bar::change_k(uint32_t)’: nested_function.cpp:56: error: no matching function for call to ‘bind(void (Bar::change_k(uint32_t)::KChanged::*)(uint32_t), Bar::change_k(uint32_t)::KChanged*, boost::arg<1>&)’ I do not really understand why this doesn't work. If I make k_changed(...) static then it works and I do not get any compilation errors. So my questions are: 1.) Is this a compiler problem? I use g++ (GCC) 4.1.2 20080704 (Red Hat 4.1.2-44) 2.) Or is such a construct not supported by the C++ language in general? 3.) Or is boost bind not able to handle local classes. 4.) And if it is possible to use bind with local functions how, do I have to implement it? I would really appreciate if somebody could help me. Best regards, Rudolf Dittrich. #include <iostream> #include <boost/bind.hpp> #include <boost/signals.hpp> typedef boost::signals::connection connection_t; class Foo { public: private: typedef boost::signal<void (uint32_t)> sig_k_t; sig_k_t _sigK; public: Foo() {} ~Foo() {} connection_t on_k_changed( const sig_k_t::slot_function_type& subscriber ) { return _sigK.connect( subscriber ); } void disconnect( connection_t subscriber ) { subscriber.disconnect(); } void set_k( uint32_t k ) { _sigK( k ); } }; class Bar { private: Foo& _foo; public: Bar( Foo& foo ) : _foo( foo ) {} void change_k( uint32_t k ) { static uint32_t k_new; struct KChanged { void k_changed( uint32_t k ) { k_new = k; } } k_changed; connection_t conn; conn = _foo.on_k_changed( boost::bind( &KChanged::k_changed, &k_changed, _1 ) ); _foo.set_k( k ); _foo.disconnect( conn ); } }; int main( int argc, char *argv[] ) { Foo foo; Bar bar( foo ); bar.change_k( 100 ); return 0; } -- Jetzt kostenlos herunterladen: Internet Explorer 8 und Mozilla Firefox 3 - sicherer, schneller und einfacher! http://portal.gmx.net/de/go/chbrowser

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[boost][graph] update adjacency_list from boost 1.33 to 1.39
by Andrey Torba 15 Jul '09

15 Jul '09

I update boost in a project from 1.33 to 1.39. In elier boost.graph adjacency_list had last template parameter 'Allocator'. Now this parameter is abcent. The question is how was it used? In my example there is a Graph type: typedef boost::adjacency_list<list_pooledS, list_pooledS, boost::directedS, NodeInfo, EdgeInfo, boost::no_property, list_pooledS, * boost::get_mat_fast_pool_alloc<char>::allocator*> Graph; as i can see allocator is defined in `list_pooledS`. Will it be enough to define such type (without last parameter)? typedef boost::adjacency_list<list_pooledS, list_pooledS, boost::directedS, NodeInfo, EdgeInfo, boost::no_property, list_pooledS> Graph; -- Regards, Andrey

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[boost][thread] Breaking Changes
by Andrey Torba 15 Jul '09

15 Jul '09

Hi all! One of breaking changes of boost.thread since 1.34 are changes in the scoped_lock interface: was: boost::mutex::scoped_lock some_lock(some_mutex,false); now: boost::mutex::scoped_lock some_lock(some_mutex,boost::defer_lock); I update boost. So i have many methods in a project which accepts a boolean variable initial_lock. void c::fff(bool initial_lock) { scoped_lock lk(m_mutex, initial_lock); // do fff .... } Now it's impossible because of different types: const defer_lock_t defer_lock={}; const try_to_lock_t try_to_lock={}; const adopt_lock_t adopt_lock={}; For example if with boost 1.33 method looked like: void c::fff(bool initial_lock) { scoped_lock lk(m_mutex, initial_lock); // do fff .... } what kind of refactoring should i do? to pass locking strategy as a template parameter? template<class Lock> void c::fff(Lock initial_lock) { scoped_lock lk(m_mutex, initial_lock); invoke_fff(); } What was the reason to have a different locking types and not enum{defer_lock, try_to_lock, adopt_lock}. Does aproach lead to any errors? -- Regards, Andrey

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Boost Unordered Map
by Wong Peter 15 Jul '09

15 Jul '09

Hello to all, does boost unordered map have a member function called find and after the key, i would manipulate the value in the hash table. Thanks. -- Linux

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[Pool] questions
by Pearl Rothman 15 Jul '09

15 Jul '09

I am using Fedora 9, gcc 4.3.0, and boost 1.38.0. I am inheriting from object_pool so I have access to some of object_pool's hidden members. Is there a way for me to find out how many memory blocks or allocated chunks there are in the free list vs how many chunks are currently being used? Is the object_pool thread safe? Does set_next_size have a permanent effect or will the double algorithm start being used after the next allocation? If it's a permanent effect, is there something I can call to start using the double algorithm again? Thanks

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Portable Approach to get System Time
by Wong Peter 15 Jul '09

15 Jul '09

Hello to all, What is the portable approach to get the current system time ? Thanks. -- Linux

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Boost Function
by Wong Peter 15 Jul '09

15 Jul '09

What is Boost::function ? I read the documentation but cann;t find any clear explanation. -- Linux

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boost bind example does not compile with member template function on gcc 4.0
by James Pritts 15 Jul '09

15 Jul '09

Unfortunately I cannot grok boost::bind error, but this code seems really simple. If I change the code so that an int is passed to async_discovery, the program compiles. The problem seems to be centered around passing a boost::bind as a template argument. Any help would be appreciated. Here is the code... #include <boost/bind.hpp> class antix_discovery_service { public: template <typename Handler> void start_async_discovery(Handler handler) { } /// Asynchronously resolve a query to a list of entries. template <typename Handler> void async_discovery(Handler handler) { boost::bind(&antix_discovery_service::template start_async_discovery<Handler>, this, handler)(); } private: int ttt; }; class test { public: void do_it() { } }; int main() { antix_discovery_service ads; test t; ads.async_discovery(boost::bind<void>(&test::do_it, t)); return 0; } and here is the error... main.cpp: In function 'int main()': main.cpp:33: warning: unused variable 'jjj' ../vendor/boost/boost/bind/bind.hpp: In member function 'void boost::_bi::list2<A1, A2>::operator()(boost::_bi::type<void>, F&, A&, int) [with F = boost::_mfi::mf1<void, antix_discovery_service, boost::_bi::bind_t<void, boost::_mfi::mf0<void, test>, boost::_bi::list1<boost::_bi::value<test> > > >, A = boost::_bi::list0, A1 = boost::_bi::value<antix_discovery_service*>, A2 = boost::_bi::bind_t<void, boost::_mfi::mf0<void, test>, boost::_bi::list1<boost::_bi::value<test> > >]': ../vendor/boost/boost/bind/bind_template.hpp:20: instantiated from 'typename boost::_bi::result_traits<R, F>::type boost::_bi::bind_t<R, F, L>::operator()() [with R = void, F = boost::_mfi::mf1<void, antix_discovery_service, boost::_bi::bind_t<void, boost::_mfi::mf0<void, test>, boost::_bi::list1<boost::_bi::value<test> > > >, L = boost::_bi::list2<boost::_bi::value<antix_discovery_service*>, boost::_bi::bind_t<void, boost::_mfi::mf0<void, test>, boost::_bi::list1<boost::_bi::value<test> > > >]' main.cpp:14: instantiated from 'void antix_discovery_service::async_discovery(Handler) [with Handler = boost::_bi::bind_t<void, boost::_mfi::mf0<void, test>, boost::_bi::list1<boost::_bi::value<test> > >]' main.cpp:35: instantiated from here ../vendor/boost/boost/bind/bind.hpp:306: error: invalid use of void expression ...failed gcc.compile.c++ ..\.bin\test_bind\gcc-4.0\debug\main.o... ...skipped <p..\.bin\test_bind\gcc-4.0\debug>test_bind.avc for lack of <p..\.bin\test_bind\gcc-4.0\debug>main.o... ...skipped <p..\.bin\test_bind\gcc-4.0\debug>test_bind.ix86-win32.elf for lack of <p..\.bin\test_bind\gcc-4.0\debug>test_bind.avc... ...skipped <pinstall>test_bind.ix86-win32.elf for lack of <p..\.bin\test_bind\gcc-4.0\debug>test_bind.ix86-win32.elf... ...failed updating 1 target... ...skipped 3 targets... Compilation exited abnormally with code 1 at Tue Jul 14 14:27:58 -Jimmy.

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Re: [Boost-users] [statechart] friend state can't call overloaded member functions in machine class
by David Matz 15 Jul '09

15 Jul '09

Hello Andreas, [snip] Replace with the following lines and everything should work: > > sc::in_state_reaction< EvBack, CoreApp, (void (CoreApp::*)(const EvBack &)) > &CoreApp::doInStateReaction >, > sc::in_state_reaction< EvNext, CoreApp, (void (CoreApp::*)(const EvNext &)) > &CoreApp::doInStateReaction > Yes, thats what I'm looking for. Now it compiles. Thanks a lot :-) David

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[program options] vectro from config file
by Diederick C. Niehorster 15 Jul '09

15 Jul '09

Hi All, I can't find an answer to this before, so I'll ask here. I would like to read a vector from a config file using program_options. example definition of option: ("Expt.ControlOrd", po::value<vector<int>>(&_pcData->SetExptOrders()), "Expt.ControlOrd") In the config file, the following works: ControlOrd = 1 ControlOrd = 2 But i would much prefer to use: ControlOrd = 1 2 or ControlOrd = (1 2) or something like that. I have made this work by editing the sourcecode, diff: ---- Index: config_file.cpp =================================================================== --- config_file.cpp (revision 54915) +++ config_file.cpp (working copy) @@ -12,6 +12,8 @@ #include <boost/program_options/detail/convert.hpp> #include <boost/throw_exception.hpp> +#include <boost/algorithm/string.hpp> + #include <iostream> #include <fstream> #include <cassert> @@ -112,8 +114,17 @@ found = true; this->value().string_key = name; this->value().value.clear(); - this->value().value.push_back(value); this->value().unregistered = !registered; + + if (*value.begin() == '(' && *value.rbegin() == ')') + { + value = value.substr(1, value.size()-2); + vector<string> SplitVec; + split( SplitVec, value, is_any_of(" ") ); + this->value().value.swap(SplitVec); + } + else + this->value().value.push_back(value); break; } else { ---- Of course, this is not a great solution as it doesn't allow you to read strings starting with ( and ending with ). Well, it is missing one thing. If we could somehow check that the datatype requested for this options is a vector, we could add that check to the if. I think that leaves only one problem, that of reading a vector of strings. Please tell me if it is possible to check for the requested type at this point in the code and how to do it. Any other comments also very welcome! I'll suggest it to the author once it works well. Thank you, Diederick

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