March 2009 - Boost-users - lists.preview.boost.org

How to post a work into a io_service and wait for it run complete?
by �]邓 18 Mar '09

18 Mar '09

I created a io_service in main thread, for dispatch user request. And i created another io_service in a thread_pool, run some sync work(like database query). After main thread got some user request, it post a query into the io_service running in the thread_pool. After the query has been completed, query thread post a work to the main thread. But the next query cannot be handled until the last result was closed. So query thread need to wait main thread until it'll not using the result any more. How to do it? Now I write some code with mutex and condition_variables. but is there any better choice with out such things?

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correct usage of bind
by Sandeep Gupta 18 Mar '09

18 Mar '09

Hi, Both the statements below bind function buildPair. While the first works the other fails. What could be a possible fix. Thanks in advance. //---- Function to be used by bind ------------------------- template<typename X, typename Y> std::pair<X, Y> buildPair(X x, Y y) { std::pair<X,Y> apair(x,y); return apair; } (std::cout<<buildPair(_1,_2).first<<' ')(1,2); ///--compiles fine--------- (bind(buildPair,_1,_2))(3,5); ///-fails------------ Thanks sandeep

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correct usage of bind (pls ignore last email)
by Sandeep Gupta 18 Mar '09

18 Mar '09

Hi, The code below tries to chain function ft1 (argument is a pair) with function buildPair (returns a pair). template<typename X, typename Y> std::pair<X, Y> buildPair(X x, Y y) { std::pair<X,Y> apair(x,y); return apair; } int main() { typedef boost::function<void (std::pair<int,int>)> FuncType1_t; std::vector<std::pair<int,int> > myvec; FuncType1_t ft1 = bind(&std::vector<std::pair<int,int> > ::push_back, &myvec, _1); typedef boost::function<void(std::pair<int,int>)> FuncType2_t; FuncType2_t ft2 = bind(ft1, bind(buildPair<int,int>,_1,_2)); //compile fails return 0; } This fails. The problem however vanished if I replace the declaration "FuncType3 ft2..." with bind(ft1, bind(buildPair<int,int>,_1,_2))(3,5); So my question is what is correct type of bind(ft1, bind(buildPair<int,int>,_1,_2)); Thanks sandeep

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[parameter] type of function arguments
by Rutger ter Borg 17 Mar '09

17 Mar '09

I'm looking into the possibilities of using Boost.Parameter to introduce extra user-friendliness to a part of the numeric-bindings libraries (in this particular case, bindings for BLAS and LAPACK). Boost.Parameter looks like it is exactly what I need, making it easy to write functions with a couple of required, and many optional parameters. What I couldn't immediately catch from the documentation, is what the types of the passed arguments are of a BOOST_PARAMETER_FUNCTION. E.g., the example in section 2.1.4 says BOOST_PARAMETER_FUNCTION( [snip] ) { // ... body of function goes here... // use graph, visitor, index_map, and color_map } but it is not clear to me is how to easily get to the type of graph, visitor, etc., in the body of the function. Thanks in advance, Kind regards, Rutger ter Borg

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Link errors with MSVC 9 application using Boost date_time on DEBUG build
by Tom Aylesworth 17 Mar '09

17 Mar '09

I have a very simple app that I'm trying to link with the Boost date_time library. It links and runs fine with I build against the RELEASE configuration. But I get the following link errors when when I use the DEBUG configuration: 2>TimeUtil.obj : error LNK2019: unresolved external symbol "public: char const * __cdecl boost::gregorian::greg_month::as_long_string(void)const " (?as_long_string@greg_month@gregorian@boost@@QBAPBDXZ) referenced in function "public: static class stlpd_std::basic_ostream<wchar_t,class stlpd_std::char_traits<wchar_t> > & __cdecl boost::date_time::month_formatter<class boost::gregorian::greg_month,class boost::date_time::iso_extended_format<wchar_t>,wchar_t>::format_month(class boost::gregorian::greg_month const &,class stlpd_std::basic_ostream<wchar_t,class stlpd_std::char_traits<wchar_t> > &)" (?format_month@?$month_formatter@Vgreg_month@gregorian@boost@@V?$iso_extended_format@_W@date_time@3@_W@date_time@boost@@SAAAV?$basic_ostream@_WV?$char_traits@_W@stlpd_std@@@stlpd_std@@ABVgreg_month@gregorian@3@AAV45@@Z) 2>TimeUtil.obj : error LNK2019: unresolved external symbol "public: char const * __cdecl boost::gregorian::greg_month::as_short_string(void)const " (?as_short_string@greg_month@gregorian@boost@@QBAPBDXZ) referenced in function "public: static class stlpd_std::basic_ostream<wchar_t,class stlpd_std::char_traits<wchar_t> > & __cdecl boost::date_time::month_formatter<class boost::gregorian::greg_month,class boost::date_time::iso_extended_format<wchar_t>,wchar_t>::format_month(class boost::gregorian::greg_month const &,class stlpd_std::basic_ostream<wchar_t,class stlpd_std::char_traits<wchar_t> > &)" (?format_month@?$month_formatter@Vgreg_month@gregorian@boost@@V?$iso_extended_format@_W@date_time@3@_W@date_time@boost@@SAAAV?$basic_ostream@_WV?$char_traits@_W@stlpd_std@@@stlpd_std@@ABVgreg_month@gregorian@3@AAV45@@Z) It is linking against "libboost_date_time-vc90-mt-sgdp-1_38.lib". Using undname, I can see that the library is using the __thiscall convention instead of __cdecl. Is this a problem in my configuration for building the Boost date_time library, or a problem in my app's build configuration? Thanks in advance for any help! Tom Aylesworth Reality Mobile LLC

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Problems upgrading from 1_34_1 to 1_38_0 in VS 2005 Express
by Roman Stepanenko 17 Mar '09

17 Mar '09

Hi, The only thing i changed in my project was new location for headers and libraries (from 1_34_1 to 1_38_0). Now I am getting these messages for a lot of classes: 1>pipeline.cpp 1>c:\program files\microsoft visual studio 8\vc\include\complex(356) : error C2589: '(' : illegal token on right side of '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(356) : error C2059: syntax error : '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(376) : error C2589: '(' : illegal token on right side of '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(376) : error C2059: syntax error : '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(381) : error C2589: '(' : illegal token on right side of '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(381) : error C2059: syntax error : '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(386) : error C2589: '(' : illegal token on right side of '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(386) : error C2059: syntax error : '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(391) : error C2589: '(' : illegal token on right side of '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(391) : error C2059: syntax error : '::' 1>noise.cpp 1>llxmlrpctransaction.cpp 1>c:\program files\microsoft visual studio 8\vc\include\complex(356) : error C2589: '(' : illegal token on right side of '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(356) : error C2059: syntax error : '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(376) : error C2589: '(' : illegal token on right side of '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(376) : error C2059: syntax error : '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(381) : error C2589: '(' : illegal token on right side of '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(381) : error C2059: syntax error : '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(386) : error C2589: '(' : illegal token on right side of '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(386) : error C2059: syntax error : '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(391) : error C2589: '(' : illegal token on right side of '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(391) : error C2059: syntax error : '::' 1>llworldmapview.cpp 1>c:\program files\microsoft visual studio 8\vc\include\complex(356) : error C2589: '(' : illegal token on right side of '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(356) : error C2059: syntax error : '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(376) : error C2589: '(' : illegal token on right side of '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(376) : error C2059: syntax error : '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(381) : error C2589: '(' : illegal token on right side of '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(381) : error C2059: syntax error : '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(386) : error C2589: '(' : illegal token on right side of '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(386) : error C2059: syntax error : '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(391) : error C2589: '(' : illegal token on right side of '::' 1>c:\program files\microsoft visual studio 8\vc\include\complex(391) : error C2059: syntax error : '::' any help is appreciated

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[Review] Polynomial library review begins today
by John Maddock 17 Mar '09

17 Mar '09

The review of Pawel Kieliszczyk's Polynomial library begins today and ends on Thurs 19th March. Download of the zip file from the vault is here: http://www.boostpro.com/vault/index.php?action=downloadfile&filename=polyno… Otherwise the library is present in the sandbox here: https://svn.boost.org/svn/boost/sandbox/SOC/2008/polynomial/ And the docs can be read online here: https://svn.boost.org/svn/boost/sandbox/SOC/2008/polynomial/libs/docs/index… The polynomial library contains a single class - polynomial<FieldType> - used for the manipulation of polynomials, along with a selection of algorithms which operate upon them. The library is an extension/rewrite of the existing "implementation detail" polynomial class in Boost.Math, and was written as part of last years Google Summer of Code under the mentorship of Fernando Cacciola. What to include in Review Comments ~~~~~~~~~~~~~~~~~~~~~~~~~ Your comments may be brief or lengthy, but basically the Review Manager needs your evaluation of the library. If you identify problems along the way, please note if they are minor, serious, or showstoppers. The goal of a Boost library review is to improve the library through constructive criticism, and at the end a decision must be made: is the library good enough at this point to accept into Boost? If not, we hope to have provided enough constructive criticism for it to be improved and accepted at a later time. The Serialization library is a good example of how constructive criticism resulted in revisions resulting in an excellent library that was accepted in its second review. Here are some questions you might want to answer in your review: * 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? And finally, every review should answer this question: * Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. Many reviews include questions for library authors. Authors are interested in defending their library against your criticisms; otherwise they would not have brought their library up for review. If you don't get a response to your question quickly, be patient; if it takes too long or you don't get an answer you feel is sufficient, ask again or try to rephrase the question. Do remember that English is not the native language for many Boosters, and that can cause misunderstandings. E-mail is a poor communication medium, and even if messages rarely get lost in transmission, they often get drowned in the deluge of other messages. Don't assume that an unanswered message means you're being ignored. Given constructively, criticism will be taken better and have more positive effects, and you'll get the answers you want. John Maddock. Review Manager for Polynomial Library.

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How to use lock_guard
by Daniele Barzotti 17 Mar '09

17 Mar '09

Hi, I'm tring to use lock_guard, but I have some doubts... I have a method called OnDataReceived() which is called by another class through a signal. void ATDispatcher::OnDataReceived() { boost::lock_guard<boost::mutex> lock(_mut); // Data received from RS232 _device.GetData(_buffer); // .... CODE .... // unlock the mutex before notifications lock.~lock_guard(); signal_OnData(); } The first time it's called, it works fine. The second time the flow locks on the creation of the lock object. In the caller class I have solved this declaring the lock in this manner: boost::mutex::scoped_lock lock(_mutex); lock.unlock(); while (true) { //main loop lock.lock(); // saving data to vector _read_buffer.append(buf, rd); //Unlock the mutex lock.unlock(); signal_OnData(); } but here because there is the worker thread loop, while in the called class there is no loop. Thanks for suggestions. Daniele.

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[mpl] is_constructible_from
by Roman Perepelitsa 17 Mar '09

17 Mar '09

I need a metafunction that returns true iif a type has a constructor with 2 arguments of a given type. Does mpl have it? If not, is it possible to implement? template <class C, class T1, class T2> struct is_constructible_from; struct foo { foo(int, int); }; struct bar { bar(int*, int); }; struct baz {}; int main() { assert(is_constructible_from<foo, int, int>::value); assert(is_constructible_from<foo, int, double>::value); assert(!is_constructible_from<bar, int, int>::value); assert(!is_constructible_from<baz, int, int>::value); }; Roman Perepelitsa.

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[graph] Looks like there is a bug in some graph-writing function
by Juan Antonio Farré Basurte 17 Mar '09

17 Mar '09

> > > Hi, > > I was correctly reading graphs in graphml and graphviz. > Now I've added support for graph writing. > And now I get tons of > errors at the last line of my code (I mean symbol '}'). > > After looking carefully at them looks like there are two families of errors, > all of them related to property maps: > > - Looks like property maps are being accessed for reading using operator[]. > But if the > property map is backed by std::map, it's documented that operator[] > in fact does an insert in the map. This is not a problem when reading a > graph, > as the graph is mutable. But of course it is a problem when writing a const graph. > I get tons of errors about modifying read-only > locations and discarding qualifiers (const, of course). > > - The other errors are about not finding a matching operator>>, also > related with properties. > In this case, it looks to be related with reading (and I think concretely graphviz), but I don't understand > why, > as it used to work before. May be this is a cryptic bug of my code. > > I don't find clear information in the errors about what graph writing > function is causing the first family > of errors. I can attach compiler output, but I'm afraid messages are in Spanish :S > Moreover, I'm not > sure if it's correct to send attached files to the list. > If anybody wants me to send it, just ask. > I've been able to locate the exact origin point of the error. It hasn't been easy. It isn't a problem of graph writing functions. The problem is in sentences like this: dp.property("min",get(&V::min,g)); where dp is a reference to a dynamic_properties object, g is a const reference to a graph and V is the type of vertex bundled properties of graph g (min is one of those properties). Commenting out all lines like this, everything compiles perfectly. Looks like, somehow, that sentence tries to modify properties in graph g and, as g is const, it fails to compile. Is there any workaround? Thanks, Juan

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