January 2010 - Boost-users - lists.preview.boost.org

wait/notify problem
by girish hilage 03 Feb '10

03 Feb '10

Hi, I am trying to implement MANAGER:WORKER model using boost thread_group. I am using wait() and notify() for that. In my application, when thread1 wants to listen for some event from thread2, it executes wait(). when thread2 wants to inform about the event to thread1, it executes notify(). The problem I am facing is : thread1 first executes wait(). then thread2 executes notify(). but notify() completes its execution even before thread1 actually starts waiting for the event and notify() is goes in vain and then thread1 keeps on waiting infinitely. To avoid this, right now I am using sleep(1) before thread2 calls notify() to make sure that thread1 really reaches the actual wait state. But this is not a permanent solution; as it is possible that even within 1sec thread1 might not actually start listening for the event. (Also 1sec makes my applcation very slow). So, I just want to know if there is any such mechanism which will enable thread2 to keep notify()ing until the event is accepted by thread1? i.e. blocked notify(). Regards, Girish

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boost any questions and praise
by Alan Tennant 02 Feb '10

02 Feb '10

Firstly. Thank you very much team Boost, it looks like it will be very useful and solve many of my coding problems. I can create an any boost::any a1; I can assign something to it a1 = string1; I can get it back out later std::cout<<any_cast<std::string>(a1); A boost any has a "type()" method. However this produced an error. std::cout<<any_cast<a1.type()>(a1);

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[multi_array] deduce logical shape of "parent" multi_array from view
by alfC 02 Feb '10

02 Feb '10

Hi, I am programming and adaptor of the HDF5 library to handle, to some extend, multi_arrays in an elegant way. It turns out that when I try to save a multi_array_view, with strides and offsets, etc. HD5F still needs to know the logical size (shape) of the parent array (the one that has contiguous elements in memory). The paradox is that in order to save an array view I need to know the original array. The question is, is there an (elegant) way to reconstruct the shape of the original array just from the multi_array_view. For moments it seems imposible because array_view doesn't know even the dimensionality of the "parent" array (or it does?). The task is further complicated because many members that may have this information are actually private or protected within multi_array_view. This is an example of what I want: multi_array<2> A(extents[10][10]); multi_array_view<1> Aview = A[3][indeces[range(0,10,2)]]; desired_function(Aview); --> returns 10, 10. Thanks, Alfredo

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boost::random: get same number sequences 32/64 bit?
by Sebastian Mach 01 Feb '10

01 Feb '10

Hello list, today I found out that boost::random, at least the combination boost::mt19937 rng(<seed>); typedef boost::uniform_int<int> dist_t; dist_t dist (<min>, <max>); boost::variate_generator< boost::mt19937&, dist_t > rand_ (rng, dist); will give me different results depending on whether I use "g++ (Debian 4.3.2-1.1) 4.3.2" (with sizeof(long)=8) or "g++.exe (TDM-2 mingw32) 4.4.1" (with sizeof(long)=4). This testcase: ++ #include <boost/random.hpp> boost::mt19937 rng(1); typedef boost::uniform_int<int> dist_t; dist_t dist (0, 16); boost::variate_generator< boost::mt19937&, dist_t > rand_ (rng, dist); int main () { for (int i=0; i<6; ++i) { std::cout << rand_() << std::endl; } } -- will print 16 8 1 6 0 12 with the 64bit variant variant, but 7 16 12 15 0 2 with the 32bit variant. Is there a (preferably portable) way to ensure that they will be the same on all 32bit+ machines? Otherwise this would be a real stopper to use boost::random for me, and I'd have to go back to libcoyotl's Mersenne Twister, which gives consistent results, upon which I really depend. Sincerely Sebastian Mach phresnel(a)gmail.com

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[range_ex]"Practical" Status of boost::range, boost::range_ex, and associated algorithms
by Jesse Perla 01 Feb '10

01 Feb '10

Hi there, I am excited to start using ranges in user code with standard algorithms (mostly copy, transform, binary_searches). Is it safe for me to start using code with range/range_ex? Since the http://www.boostpro.com/vault/index.php?directory=Algorithms version hasn't been updated for a while, I was worried that there could be interface changes. I am perfectly willing to use a subset of algorithms that are expected to remain stable -Jesse

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mix usage of boost.thread and pthread?
by Hua Su 01 Feb '10

01 Feb '10

Hi all, Is it OK to use both pthread and boost.thread in the same program under linux? E.g., there are two cases: 1. use pthread api to create/join/detach/cancel threads but use boost.thread's mutex/condition_variable etc. to do thread synchronization, and this_thread/sleep/get_id/thread_local_storage etc.. 2. use boost.thread api to create/join/detach/interrupt thread but use pthread api to do thread synchronization. I know boost.thread is a pthread api wrapper under linux, but I'm afraid of that the two cases above aren't safe if boost.thread uses some tricks I don't understand. Would you kindly give any hints? Thanks! Hua

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[property_tree]problem with equal_range
by Ken Murphy 01 Feb '10

01 Feb '10

Hello all, I am getting an error while trying to compile the following program: #include "boost/property_tree/ptree.hpp" int main(int argc, char* argv[]) { boost::property_tree::ptree t; t.equal_range("KEY"); return 0; } Compiler output: 1>c:\hibbettlinux\src\boost-1.41.0\boost\property_tree\detail\ptree_impl 1>emen tation.hpp(448) : error C2039: 'base' : is not a member of 'boost::multi_index::detail::bidir_node_iterator<Node>' 1> with 1> [ 1> Node=boost::multi_index::detail::ordered_index_node<boost::multi_index::deta il::index_node_base<std::pair<const std::string,boost::property_tree::basic_ptree<std::string,std::string>>,std: :allocator<std::pair<const std::string,boost::property_tree::basic_ptree<std::string,std::string>>>>> 1> ] 1> c:\hibbettlinux\src\boost-1.41.0\boost\property_tree\detail\ptree_implementa tion.hpp(444) : while compiling class template member function 'std::pair<_Ty1,_Ty2> boost::property_tree::basic_ptree<Key,Data>::equal_range(const std::basic_string<_Elem,_Traits,_Ax> &)' 1> with 1> [ 1> _Ty1=boost::property_tree::basic_ptree<std::string,std::string>::assoc_itera tor, 1> _Ty2=boost::property_tree::basic_ptree<std::string,std::string>::assoc_itera tor, 1> Key=std::string, 1> Data=std::string, 1> _Elem=char, 1> _Traits=std::char_traits<char>, 1> _Ax=std::allocator<char> 1> ] 1> c:\hibbettlinux\src\platform\vc80\test\test.cpp(9) : see 1> reference to class template instantiation 'boost::property_tree::basic_ptree<Key,Data>' being compiled 1> with 1> [ 1> Key=std::string, 1> Data=std::string 1> ] 1>c:\hibbettlinux\src\boost-1.41.0\boost\property_tree\detail\ptree_impl 1>emen tation.hpp(449) : error C2039: 'base' : is not a member of 'boost::multi_index::detail::bidir_node_iterator<Node>' 1> with 1> [ 1> Node=boost::multi_index::detail::ordered_index_node<boost::multi_index::deta il::index_node_base<std::pair<const std::string,boost::property_tree::basic_ptree<std::string,std::string>>,std: :allocator<std::pair<const std::string,boost::property_tree::basic_ptree<std::string,std::string>>>>> 1> ] I am using boost 1.41 with VC 7.1 Any help is appreciated!!!!!! Ken Murphy

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Mingw: build, install, .LIB files and boost-config?
by John Pye 01 Feb '10

01 Feb '10

Hi all While I'm aware that MinGW is not one of the 'primary' platforms for MinGW, I wanted to ask a few questions to help me in the task of building a binary copy of Boost for this platform that's as good as it can be. Firstly, what would be the correct build commands to build Boost for MinGW such that I end up with both shared libraries and static libraries? What I've worked out so far is shown here: http://ascendwiki.cheme.cmu.edu/Binary_installer_for_Boost_on_MinGW Secondly, to install Boost at an arbitrary path under MinGW, what is the correct BJAM command? On MinGW, I'm not running ./configure, so the suggestions from the Unix build documentation don't make sense. By default under MinGW, if I run "bjam install", my files end up in c:\Boost but I'd like too have another target directory, so that it's possible to build even without write privileges to that folder. Is there such a thing as "bjam --install-prefix=c:/MinGW install"? Is there a way to strip out all the redundant folder levels like "release" and "gcc-mingw-3.4.5" etc? Third, using BJAM on MinGW results in .LIB files being generated. These .LIB files are NOT correctly names for use with MinGW. As far as I can tell, I have to rename them as .A files, or else do something else with them so that they'll correctly be detected by the the GCC "-l" linker flag. Finally, there was a bit of discussion on the mailing list about a year ago about providing a "boost-config" script. With the ever-changing naming conventions for Boost libs, and the possible presence of static libraries, shared libraries, -mt, -d, and other file suffixes, such a script would be INVALUABLE for people looking to access pre-built Boost binaries for their projects. It would be an almost trivial task to implement such a script -- has there been any progress on this anywhere? Can I suggest that for MinGW, a native shell script, with file paths constructed relative to the boost-config path, would probably be the best way, rather than pkg-config, which is not available in MinGW/MSYS by default. Feel free to direct me to the online documentation of this stuff if it exists -- I couldn't find it though. Cheers JP -- John Pye Dept of Engineering Australian National University http://pye.dyndns.org/

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boost serialization stream error question
by Gabe Sibley 01 Feb '10

01 Feb '10

Dear All, I'm using boost serialization and have come across issues with "steam error" when I try to deseriailze from an xml or text archive. Binary archives are fine, but I can't use binary because my users need xml archives. The problem is caused by double values less than DBL_MIN. Apparently, streaming such values in causes the input stream fail_bit to be set, which causes the serialization lib to throw an exception. One work around is to make sure all double values are clamped and finite when the archive is created. I can live with this, esp. since I have algorithms that will from time to time produce non-finite results. So far what I've done is just replace BOOST_SERIALIZATION_NVP macro with the following MAKE_NVP macro that calls "FixReal": #define BOOST_SERIALIZATION_NVP(name) \ boost::serialization::make_nvp(BOOST_PP_STRINGIZE(name), name ) // Use this macro instead of BOOST_SERIALIZATION_NVP because it fixes doubles that are not streamable. // That is, it fixes double values that cause streaming errors. #define MAKE_NVP(name) \ boost::serialization::make_nvp(BOOST_PP_STRINGIZE(name), FixReal(name) ) // note the call to FixReal // does nothing -- just pass all non-double types through template<class T> inline T& FixReal( T& t ) { return t; } /// Routine to make sure doubles are streamable -- Nan, Inf, etc. cause stream errors, so we prevent them. inline double& FixReal( double& d ) { if( d < DBL_MIN ) { d = DBL_MIN; } if( d > DBL_MAX ) { d = DBL_MAX; } if( std::isnan(d) ) { d = 0; } if( std::isinf(d) ){ d = DBL_MAX; } return d; } /// We also need to fix double arrays. The ugly syntax is because // we have to pass and return a reference to an array. inline double (&FixReal( double (&d)[2] ))[2] { for( size_t ii = 0; ii < 2; ii++ ){ FixReal(d[ii]); } return d; } Ok, here's my question: How can I get the "FixReal" functionality above without having to write a specialized function for every possible double signature? For instance, I don't want to have to write inline double (&FixReal( double (&d)[3] ))[3] inline double (&FixReal( double (&d)[4] ))[4] ... etc. or any of the other POD double signatures possible. I just want the serialization library to fix the errant double values when I create the archive. I guess I could modify the "void save(const double t)" function in basic_text_oprimitive.hpp to check all doubles, but that seems like a bad plan. Any suggestions? thanks for your help, Gabe

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Strange output from boost::exception diagnostic_information
by pholding 01 Feb '10

01 Feb '10

-------------------------------------------------------------------------------- I've been having a look at the diagnostic_information function in the boost exception library, but seem to be getting a strangely formatted output. The code I'm using is as follows Code: #include <boost/exception/diagnostic_information.hpp> #include <stdexcept> #include <iostream> void myerror(){ throw boost::enable_error_info(std::range_error("blah")); } int main(){ try{ myerror(); } catch(boost::exception & e){ std::cerr << diagnostic_information(e) << std::endl; } return 0; }The output is as follows: Quote: Throw in function (unknown) Dynamic exception type: N5boost16exception_detail19error_info_injectorISt1 1range_errorEE std::exception::what: blah What I don't understand is why I'm getting N5, 16, 19, ISt11 and EE between the details of the exception type. To rule out my code, I compiled the example_io.cpp file provided in the boost example documentation and I'm getting a similar output. Does anyone what is causing the strange characters displayed? I'm running Ubuntu 9.10 and the version of g++ is 4.4.1 -- View this message in context: http://old.nabble.com/Strange-output-from-boost%3A%3Aexception-diagnostic_i… Sent from the Boost - Users mailing list archive at Nabble.com.

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Re: [Boost-users] [BGL] Color Maps
by pablo barrio lópez-cortijo 31 Jan '10

31 Jan '10

Hi Andrew, thanks for your help. > I would recommend using the named parameter version of the call since it lets you omit optional parameters. It seems like the right approach. So now my code is as follows: typedef graph_traits<graph_t>::vertex_descriptor Vertex; Vertex source; ... some code that finds the appropriate vertex // DFSActions is the DFS visitor, with actions on vertex discover and finish DFSActions actions(this); // Calling DFS with named parameters depth_first_search(*g, visitor(actions), root_vertex(source)); Problem: the code doesn't compile, and I'm sure the fault is in "root_vertex(source)". This is the (very synthesized) error thrown by the compiler: property_map.hpp: In instantiation of ‘boost::property_traits<boost::bgl_named_params<long unsigned int, boost::root_vertex_t, boost::no_property> >’: depth_first_search.hpp:192: instantiated from ‘void boost::depth_first_search( long line ) [ with REALLY long line ]’ depth_first_search.hpp:222: instantiated from ‘void boost::depth_first_search( long line ) [ with REALLY long line ]’ graphdef.cpp:134: instantiated from here graphdef.cpp:134: instantiated from here property_map.hpp:31: error: no type named ‘key_type’ in ‘struct boost::bgl_named_params<long unsigned int, boost::root_vertex_t, boost::no_property>’ property_map.hpp:33: error: no type named ‘reference’ in ‘struct boost::bgl_named_params<long unsigned int, boost::root_vertex_t, boost::no_property>’ property_map.hpp:34: error: no type named ‘category’ in ‘struct boost::bgl_named_params<long unsigned int, boost::root_vertex_t, boost::no_property>’ And many other errors, but this is the first one. To check if the problem was in my "source" vertex, I changed the call to DFS with the default value for the root_vertex (looked up in the header file): depth_first_search(*g, visitor(actions), root_vertex(*vertices(*g).first)); The error keeps showing. Having a look at the DFS source code, it seems that the named param function expects a root_vertex of type root_vertex_t, which appears several times in the error msg. The Boost docs specify a type of graph_traits<graph_t>::vertex_descriptor, which is what I'm using now. I suppose it's the same type, but I've not found the type definition. I'm sure it must be a very stupid mistake, but I can't see it. Any clues?

2 1

[circular_buffer] Serialization support for circular_buffer
by Brian Wood 31 Jan '10

31 Jan '10

B"H Shalom, Boost, The C++ Middleware Writer now supports marshalling circular_buffers. This is done by transmitting a circular buffer's capacity, then size, followed by it's elements. An example of the code used when marshalling a circular_buffer is here -- http://webEbenezer.net/posts/cirbuf.hh. -- Brian Wood http://www.webEbenezer.net (651) 251-9384

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Can someone provide an Asio Serial Port example?
by Jeff 30 Jan '10

30 Jan '10

I would like to use Asio to connect to a microcontroller to send and read from, but there are no serial_port samples available. For instance, I would like to type an ‘a’ into the keyboard and have the microcontroller return 1. The microcontroller is already programmed for this but I need to create an interface for it. A sample that does this or any working sample at all would be sincerely appreciated. Thank you, Jeff

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std::list customization
by Etienne Philip Pretorius 30 Jan '10

30 Jan '10

Hello List, I know this is not boost specific, but I would appreciate any comments about the following. I have a specific set of values stored in a std::list<unsigned char>. As expected I can delete and add items anywhere, since I am using the std::list object rearrange its own contents. But here is the problem - when I have already decided that item at position 13 should always remain at position 13 if the list has 13 or more objects in it... If I remove an item from the beginning then the item at position 13 becomes the item at position 12, while this is undesired - the effect of shifting everything else on by one value is desired. Some examples of what I require: Fixed position marked with []. a,b,c,[d],e,f pop_front() is called b,c,e,[d],f This list object should also work when inserting items and keep those with fixed positions at their position if the object size allows it. Any suggestions, Ideas on how to implement this would be greatly appreciated. Kind Regards, Etienne

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[mpl - function_types] Generate typedef from operator() of a functor
by Olivier Tournaire 30 Jan '10

30 Jan '10

Hi all, Given an mpl sequence of types such as: typedef mpl::vector<T0, T1, T2, T3> arg_types; 1) the users of my library provide functors such as F (where T0 and T1 may have been any of the types of arg_types: class F { typedef mpl::pair<T0,T1> signature_type; double operator()(const T0& t0, T1& t1); }; is there a way to generate signature_type automatically ? 2) if the operator() is overloaded, the user class currently has to typedef an mpl::vector of mpl::pairs such as class G { typedef mpl::vector<mpl::pair<T2,T3>, mpl::pair<T1,T1>, mpl::pair<T3,T1> > signature_type; double operator()(const T2& t2, T3& t3); double operator()(const T1& t1, T1& t1); double operator()(const T3& t3, T1& t1); }; in this case, is it also possible to generate signature_type automatically ? Regrads, Olivier

2 3

[function_types] About parameter_types
by Olivier Tournaire 30 Jan '10

30 Jan '10

Hi all, I am trying to extract the parameters types of a given function/functor in a mpl sequence. Digging boost libraries, I came across function_types, and in particular parameter_types, which might be the right tool. However, I cannot figure how to use it. Could you please help ? Suppose I have: void foo(int, double); And would like to generate the following sequence: mpl::vector<int, double> How can I do that ? Regards, Olivier

2 2

[doc] Add "Last Update" information
by Marco Guazzone 30 Jan '10

30 Jan '10

Dear Boosters, In my opinion it would be very helpful if the documentation include for each library the version of the last update. For instance, one could add this information in the summary page (http://www.boost.org/doc/libs/1_41_0) --- [snip] --- uBLAS uBLAS provides matrix and vector classes ... Author(s)...........Joerg Walter and Mathias Koch First Release...1.29.0 -> Last Update......1.40.0 <- Standard Build & Link......Header only Categories........Math and numerics --- [/snip] --- The reason for this is that it should simplify the discovery of what version of Boost one needs for his own software project. As a matter of fact, the use of "First Release" might not be sufficient because after the initial release of a library many other features could have been added. So the need for this additional piece of information. What do you think? Regards, -- Marco

1 0

asio UDP local port binding issue on Windows
by akos＠maroy.hu 30 Jan '10

30 Jan '10

Hi, I seem to encounter an issue when using boost asio. I'm trying to create a UDP client-server environment, where for the client I'm creating an asio socket like this: io_service _io_service; ip::udp::socket _socket(_io_service, ip::udp::v4()); my expectation at this point is that the _socket is created, and it can send and receive UDP packets. this includes receiving packets, which also means that the socket is bound to some random port on the local network interface. now this is all true on Linux and MacOS, but on Windows, the socket does not seem to bind to a port. interestingly, for _socket.is_open() I get true in return. but for _socket.local_endpoint(), I get an error excaption with the error code 10022, which is defined as WSAEINVAL. I also tried the following, and got the same results: io_service _io_service; ip::udp::socket _socket(_io_service); _socket.open(ip::udp::v4()); is my assumption that the above should result in a socket bound to a local random port incorrect? Akos

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Property Tree - adding child nodes to a parent
by Jon Shuler 30 Jan '10

30 Jan '10

I am trying to build a property tree from hierarchy data in a database. I want to be able to add a child at a given node using something similar to: parentNode.add_child("child name", data_type). There is a add_child method but it expects the path to add the child at. I looked at the examples and did not see anything. Is this possible? Jon This e-mail message and any attachment(s) transmitted with it are intended only for the use of the recipient(s) named above.This message may be privileged and/or confidential. If you are not an intended recipient, you may not review, copy or distribute this message. If you have received this communication in error, please notify us immediately by e-mail and delete the original message.

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Re: [Boost-users] Detect specialized template function?
by Andrew Chinkoff 30 Jan '10

30 Jan '10

Hi, Daniel. This is your example: template <class T> void S::f() { if(g is specialized) // (1) callbacks_ready=true; // else wait for a callback object to be registered } At (1) the runtime detection is used, but "S:g()" was specialized at compile time. Templates are specialized and compiled at compile time, but not runtime. We can't write "if(g is specialized)" - it is impossible to realize it at runtime (and it is senseless). So let me to recommend you some books of H. Sutter and A. Alexandrescu. There are a lot of recommendations about templates, their specializations, overloads, static/dynamic polymorphisms and more. 1st book: [http://www.gotw.ca/publications/xc++s.htm] Pay attention to this chapter of the book: "Item 7: Why Not Specialize Function Templates?" 2nd book; "C++ Coding Standards: 101 Rules, Guidelines, and Best Practices" (authors H. Sutter and A. Alexandrescu) Pay attention to 64, 65, 66 and 67 chapters. I hope you will find some useful ideas about templates in these books. There are also Boost libraries targeted to realize static polymorphism: 1) http://www.boost.org/doc/libs/1_40_0?view=category_Generic 2) http://www.boost.org/doc/libs/1_40_0?view=category_Metaprogramming Best, Andrew. > Slightly OT, but I was hoping someone here might know the magic incantation > (which may involve a Boost library). > Given a template class such as > template <class T> > struct S > { > void f(); > void g() { T t(h()); cb(t) } > T & h(); > boost::function1<void, T &> cb; > }; > Is there a way to have S.f() behave differently depending on whether S.g() uses > the default definition or whether it is specialized for this particular type? > This detection needs to occur before S.g() is ever called. > For example, the mere existance of the specialization > template <> void S<int>::g() { ... } > should trigger special logic in S<int>::f(). > Thanks, > Daniel > P.S. The motivation for this is an attempt to retrofit a callback API that > allows specialization of S.g() or the registration of a boost::function that > gets called by the default S.g(). We need to disable callbacks until an actual > function is registered via either method. It is easy to dispatch on > registration of the boost::function; I don't know how to detect the > specialization.

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Boost 1.36.0 with Linux 64bits
by JongKwan Kim 29 Jan '10

29 Jan '10

Hi all, I would like to know if the boost 1.36.0 is working well with Linux 64 bits. If I want to compile with boost 1.36.0 and Linux 64 bits, how should I install the boost 1.36.0? Is it the same to 32 bits machine? Please, if someone knows that, let me know. Thanks,

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fusion sequences, type erasure across translation units
by Hicham Mouline 29 Jan '10

29 Jan '10

Hello, I have a .cpp file which a sort of top level driver. I have say 100 different struct param_i {...}; where 1<=i<=100 Each param_i is defined in a param_i.hpp and param_i.cpp invokes metafunctions to obtain typedef fusion< variant< vector<double>, triplet<double>, pair<double>, double>, variant<...>, ..., variant<...> > seq_i_t; this sequence type is visible only in the param_i.cpp, not the header file. Generation of this sequence is The size of these sequences = number of members of param_i. The toplevel driver and other .cpp need to move instances of these types around to other .cpp. To avoid having the compiler call the metafunctions for these middle translation units, but only at the generating .cpp and at the consuming .cpp, I created a tag struct fusion_seq_tag {}; typedef <typename Arg> struct make_fusion_seq_i { typedef <undefined> type; }; typedef <typename Arg> struct make_fusion_seq_tag { typedef typename make_fusion_seq_i<Arg>::type base_type; struct type : fusion_seq_tag, base_type { type(...) : base_type(...) {} }; }; return smart_ptr<fusion_seq_tag>( new make_fusion_seq_tag<...>::type ); // this was the generating .cpp The function returns smart_ptr<fusion_seq_tag> which can move around in other .cpp without any metaprogramming until reaching the consuming .cpp Is this type erasure? I don't know how I can get the actual type back in the consuming .cpp if I don't know the originator but if I know only the shape of the fusion sequence. How to dynamic cast the type back to its unerased type? If I know the originator .cpp then I would know the exact fusion sequence and therefore I would just dynamic_cast the fusion_seq_tag. Regards,

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[boost][task] task and fiber do not compile
by Kishalay Kundu 29 Jan '10

29 Jan '10

Hi Oliver, I have boost 1.41.0 installed. I have been trying to build boost-task and boost-fiber (I guess this is the pre-req for building boost-task). However when I do: "./bjam threading=multi --with-task", the compiler errors out with a long list of compiler errors. I have gcc 4.4.1 installed on my Fedore 11 system. Could you please let me know what I am doing wrong? Thank you. regards, Kishalay

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[BGL] Color Maps
by pablo barrio lópez-cortijo 29 Jan '10

29 Jan '10

Hi there! I'm new to Boost (and also to this mailing list). I'm using depth_first_search and it's vital for me to be able to specify the root vertex (4th argument), and that means also specifying the Color Map, which I don't care too much about. It'd be great to have a default color map but I'm a newbie and I didn't found anything in the docs. My initial options were: a) Using sth like a "default_color_map" class. I ignore if there is such thing. b) Creating a property map out of a vector, something like "vector_property_map<default_color_type>". I tried and it didn't work. c) Including a property in my graph called "color" of type "default_color_type", and creating a property map out of it. Didn't work either. Actually, I get an error when trying to include the property with that type (compiles if the property is an int). d) Just copying the color map that the algorithm uses when called without the color map argument. Hoping to find out how the BGL code works was simply unrealistic so I abandoned the idea. Is there any way to easily instantiate a Color Map? I'd post my code, but I have 6 or 7 versions none of which work. Any help will be much appreciated. Thanks ahead!

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Detect specialized template function?
by dherring＠ll.mit.edu 29 Jan '10

29 Jan '10

Slightly OT, but I was hoping someone here might know the magic incantation (which may involve a Boost library). Given a template class such as template <class T> struct S { void f(); void g() { T t(h()); cb(t) } T & h(); boost::function1<void, T &> cb; }; Is there a way to have S.f() behave differently depending on whether S.g() uses the default definition or whether it is specialized for this particular type? This detection needs to occur before S.g() is ever called. For example, the mere existance of the specialization template <> void S<int>::g() { ... } should trigger special logic in S<int>::f(). Thanks, Daniel P.S. The motivation for this is an attempt to retrofit a callback API that allows specialization of S.g() or the registration of a boost::function that gets called by the default S.g(). We need to disable callbacks until an actual function is registered via either method. It is easy to dispatch on registration of the boost::function; I don't know how to detect the specialization.

2 1