- Boost-users - lists.boost.org

Re: [Boost-users] Bind/Function: use reference arguments in template variadic functions
by Yannick POTIN 13 Apr '13

13 Apr '13

> > Actually, I try to use template variadic functions which can contains references, pointers and/or values which must be converted to boost::function0<void>. > > I tried to use forward() but I lose references with it. I tried ref() to but it make values interpreted as references (so ints are broken). So I'm looking for a magic way to use ref() only when needed by the arguments. > What do you mean by "when needed by the arguments?" How do you specify what should have ref added and what shouldn't? Well, I tried to make a template pseudo-code to determine which function it needs to use. Like this code that does not work: ///// Big code to make it working template<typename W,typename T> struct SignalArgumentValueConverter { }; template<typename T> struct SignalArgumentValueConverter<const boost::reference_wrapper<T>,T> { static const boost::reference_wrapper<T> convert(T&& t) { return boost::ref<T>(t); } }; template<typename T> struct SignalArgumentValueConverter<T&&,T> { static T&& convert(T&& t) { return std::forward<T&&>(t); } }; template<typename T> struct SignalArgumentTypeConverter { typedef typename std::conditional<std::is_reference<T>::value,const boost::reference_wrapper<T>,T&&>::type type; static type convert(T&& t) { return SignalArgumentValueConverter<type,T>::convert(std::forward<T&&>(t)); } }; ////// Little code to use it // Note: current is an iterator on a std::vector< boost::function<void(Args…)> > (*current)( SignalArgumentTypeConverter<Args>::convert(boost::forward<Args>(args))... ); This code does not compile and I think that I may break its code while I made some tests. Any idea to create something lile that (or even better) ? Regards, Yannick POTIN

1 0

[program_options] Possible to compose notifier to void void function?
by Michael Powell 13 Apr '13

13 Apr '13

Hello, Is it possible? Something like the example identified here: http://stackoverflow.com/questions/7125666/what-is-boostprogram-optionsnoti… Except I'd like to hook up a void(void) notifier handler instead of the parameter. Thank ye... Regards, Michael Powell

2 1

Re: [Boost-users] Bind/Function: use reference arguments in template variadic functions
by Yannick POTIN 12 Apr '13

12 Apr '13

> > >> template<class ...classes> >> boost::function0<void> call_something(classes&... c) > > Thank you, It actually allows me to use references in these functions. > I just tried and g++ is waiting for only references but I need to use pointers and/or values too. > There is a way to use mixed types in template variadic functions ? > For perfect forwarding use: template<class... T> void call(T&&... t) { foo(std::forward<T>(t)...); } I tried this one too and it works fine thank you. However, I use these functions with boost::bind library and actually references are lost when I use it (and I need to). After some google searches, it seems that boost::bind officially does not support this use (due to internal references). So I tried with std::bind because I read somewhere the problem was fixed with its C++11 version. The problem is the same : with std::bind too, references are lost using std::forward. Does anyone made this duo bind/template variadic functions working together ? And if someone did, how did you do ? Sorry, I lost context with what you're trying to do, but maybe you want to use boost::ref / std::ref in conjunction with boost::bind / std::bind, respectively? I think that should indicate to the binding framework to hold the bound values by reference rather than by value (if that's what you want). - Jeff Actually, I try to use template variadic functions which can contains references, pointers and/or values which must be converted to boost::function0<void>. I tried to use forward() but I lose references with it. I tried ref() to but it make values interpreted as references (so ints are broken). So I'm looking for a magic way to use ref() only when needed by the arguments. Regards, Yannick POTIN

2 1

Difficulty using promises and futures
by Michael Powell 12 Apr '13

12 Apr '13

Hello, I would like to use promises and futures in our embedded app. We're targeting ArchLinux ARM. I believe we can build against a GCC 4.7.2 toolchain which has either C++0x or possibly even C++11 (somewhat) support. I am trying to setup a couple of simple issues to make it even compile, but am having trouble. boost::packaged_task<vector<int> > int_vect_pt_(simple_vector_getter); boost::unique_future<vector<int> > int_vect_f_ = int_vect_pt_.get_future(); boost::thread task(boost::move(int_vect_pt_)); boost::packaged_task<int> int_pt_(simple_getter); boost::unique_future<int> int_f_ = int_pt_.get_future(); boost::thread task(boost::move(int_pt_)); Error(s): Description Resource Path Location Type 'boost::move' is ambiguous ' Candidates are: boost::type move(boost::packaged_task<int> &) ' optics.cpp /detector/devices line 156 Semantic Error Description Resource Path Location Type 'boost::move' is ambiguous ' Candidates are: boost::type move(boost::packaged_task<std::vector<int,std::allocator<int>>> &) ' optics.cpp /detector/devices line 152 Semantic Error Can anyone help or otherwise advise? I've even got a "crude" future implementation in C# .NETCF for pity's sake... Anyway, if necessary, what did we do before promises/futures? ;-) Thank you... Regards, Michael Powell

2 3

Re: [Boost-users] Bind/Function: use reference arguments in template variadic functions
by Yannick POTIN 12 Apr '13

12 Apr '13

> >> template<class ...classes> >> boost::function0<void> call_something(classes&... c) > > Thank you, It actually allows me to use references in these functions. > I just tried and g++ is waiting for only references but I need to use pointers and/or values too. > There is a way to use mixed types in template variadic functions ? > For perfect forwarding use: template<class... T> void call(T&&... t) { foo(std::forward<T>(t)...); } I tried this one too and it works fine thank you. However, I use these functions with boost::bind library and actually references are lost when I use it (and I need to). After some google searches, it seems that boost::bind officially does not support this use (due to internal references). So I tried with std::bind because I read somewhere the problem was fixed with its C++11 version. The problem is the same : with std::bind too, references are lost using std::forward. Does anyone made this duo bind/template variadic functions working together ? And if someone did, how did you do ? Regards, Yannick POTIN

2 1

Document for static / dynamic library?
by young 12 Apr '13

12 Apr '13

How do I know which library have both dynamically linked library and static linked library? I heard of there may be some libraries that can only be statically linked (Boost.Test for example) and others which may only be dynamically linked (Boost.Threads for example), Does any document has the list for available library? Or I have to look at each library individually? -- View this message in context: http://boost.2283326.n4.nabble.com/Document-for-static-dynamic-library-tp46… Sent from the Boost - Users mailing list archive at Nabble.com.

1 0

boost_thread-vc100-mt-1_53.lib vs libboost_thread-vc100-mt-1_53.lib
by young 12 Apr '13

12 Apr '13

I try to use boost library in VC++ application, I am wondering which library to use. For example, for boost thread, should I use boost_thread-vc100-mt-1_53.lib or libboost_thread-vc100-mt-1_53.lib? What is difference between them? or in more general, what is difference between boost_xxx_vc100-mt-1_53.lib and libboost_xxx_vc100-mt-1_53.lib? -- View this message in context: http://boost.2283326.n4.nabble.com/boost-thread-vc100-mt-1-53-lib-vs-libboo… Sent from the Boost - Users mailing list archive at Nabble.com.

5 12

Re: [Boost-users] Bind/Function: use reference arguments in template variadic functions
by Yannick POTIN 12 Apr '13

12 Apr '13

AMDG On 04/11/2013 01:57 PM, Yannick POTIN wrote: > > <snip> > > // A template variadic function... > template<class ...classes> > boost::function0<void> call_something(classes... c) { > // ... here we are: > return boost::bind(call_a,boost::ref(c...)); > } > > <snip> > ---------------------------------------------- > After compilation, I get this output (watch the memory addresses): > 0xbfc8f994::operator()(): 1 > 0xbfc8f990::operator()(): 2 > 0xbfc8f984::operator()(): 1 > 0xbfc8f984::operator()(): 2 > I really don't know what happened (even if I can imagine). > But references are just lost and this is not good. > > So, here is my question: How can I make this working ? > The arguments of call_something are passed by value. Try: template<class ...classes> boost::function0<void> call_something(classes&... c) In Christ, Steven Watanabe Thank you, It actually allows me to use references in these functions. I just tried and g++ is waiting for only references but I need to use pointers and/or values too. There is a way to use mixed types in template variadic functions ? Regards, Yannick POTIN

2 1

[preprocessor] How to transform sequence into sequence of tuples.
by Mostafa 12 Apr '13

12 Apr '13

How would I go about doing the following transformation: (a)(b)(c)(d) -> (a, b)(c, d) Thanks, Mostafa

3 5

Asio Serial ports: enumerating all the devices
by Vincent Boucher 12 Apr '13

12 Apr '13

Hello, Are there cross-platform methods to discover all the devices currently connected through serial ports with Boost? The idea is to have a function returning a list of device objects, each containing a handle, the related vendor id, product id and the baud rate at which the device was able to communicate. My knowledge of serial communication is very limited, may be it is technically infeasible. Do you have any thoughts for Boost or other libs? Analog enumerate method for HID devices: http://www.signal11.us/oss/hidapi/ Thanks, Vincent

5 13