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[phoenix] Staus of phoenix
by Edward Diener 18 Dec '09

18 Dec '09

Is phoenix an official Boost library ? I do not see it listed among the Boost libraries for 1.40 or 1.41 although I do see it in the pdf documentation for Boost libraries put together by John Maddock.

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Template type questions
by Glenn Macgregor 18 Dec '09

18 Dec '09

Hi All, I am using the boost::variant with the binary visitor algorithm, apply_visitor. struct UnknownValue {}; typedef boost::variant<UnknownValue, long, unsigned long, double, string, char> ValueType; I am using apply_visitor for binary visitation as below: class AddVisitor : public boost::static_visitor<> { public: template <typename T> void operator()(const T &lhs, const T &rhs) { T val = lhs + rhs; } template <typename T, typename R> void operator()(const T &lhs, const R &rhs) { // do nothing...different types } template <typename T> void operator()(const T &lhs, const UnknownValue &rhs) { // do nothing...we have an unknown value } template <typename T> void operator()(const UnknownValue &lhs, const T &rhs) { // do nothing...we have an unknown value } void operator()(const UnknownValue &lhs, const UnknownValue &rhs) { // do nothing...we have an unknown value } }; The above is not complete because I can do addition if the types are long and unsigned long or long and double or long and char...etc. What is the preferred method for doing this? Do I need to create an overridden operator() for every argument combination that is valid or can I get the argument types in the function? Thanks Glenn

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[spirit] help parsing data file into a struct
by Kenny Riddile 18 Dec '09

18 Dec '09

This is my first time using Spirit and I haven't messed with writing EBNF grammars since college, so I'm sorry if this is a simple question. Lets say I have a structure that looks like this: struct Foo { std::string someString; std::string someOtherString; std::vector<std::string> stringList; }; BOOST_FUSION_ADAPT_STRUCT( Foo, (std::string, someString) (std::string, someOtherString) (std::vector<std::string>, stringList) ) and I have a data file that looks like this: SOMESTRING hello SOMEOTHERSTRING goodbye STRINGLIST { string1 string2 string3 } I have written the following grammar to parse such a file into the struct above: template< typename Iterator > struct FooDefinition : spirit::qi::grammar< Iterator, Foo() > { FooDefinition() : FooDefinition::base_type( start ) { using namespace spirit::qi; start = someString >> +space >> someOtherString >> +space >> stringList; someString = lit("SOMESTRING") >> +space >> value; someOtherString = lit("SOMEOTHERSTRING") >> +space >> value; stringList = lit("STRINGLIST") >> *space >> lit('{') >> *space >> (value % +space) >> *space >> lit('}'); value = +char_("a-zA-Z_0-9"); space = lit(' ') | lit('\n') | lit('\t'); } spirit::qi::rule< Iterator, Foo() > start; spirit::qi::rule< Iterator, std::string() > someString; spirit::qi::rule< Iterator, std::string() > someOtherString; spirit::qi::rule< Iterator, std::vector<std::string>() > stringList; spirit::qi::rule< Iterator, std::string() > value; spirit::qi::rule< Iterator > space; }; However, I would like the order of the three statements in the data file (SOMESTRING, SOMEOTHERSTRING, and STRINGLIST) to be irrelevant. Right now, they must be in the order shown above for parsing to succeed. How would I go about accomplishing this with Spirit?

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inheritance, input streams, parsing and arithmetic range of values
by Hicham Mouline 18 Dec '09

18 Dec '09

Hello I would like your opinions about design/implementation choices for an application I am writing. I have a list of models. Each model is a kind of black box that takes inputs and produces outputs. All the inputs are either of boolean or arithmetic type. (bool, int, double) A subset of inputs is valid for all models. Then different models have different number of other inputs. For a fixed set of inputs, the model produces 1 fixed set of outputs. It is desired to vary the values of some/all (at least 1) of the inputs and get different outputs sets, and then plot that. The inputs are specified in files (considered as std::istream in the code), the syntax is trivial: input1 = value1 ... inputn = valuen When it is desired to vary the input values, the syntax changes a little: input1 = value1 input2 = value21..value22 ... inputn = valuen in this example only input2 changes, and the idea is to plot one of the outputs over the differnt values of input2. Each derived model has a concrete struct input_i_s { ... } that holds its inputs. class model { public: virtual fixed_inputs get_fixed_inputs( std::istream& ) const =0; /// throws if syntax error, or not all inputs are specified, or some values are not valid virtual variable_inputs get_variable_inputs( std::istream& ) const =0; /// the same, allows the '..' notation though for ranges, at least of the inputs need to be a range }; // fixed_inputs is a pointer to a base class of all inputs for all models 1 implementation pseud-code looks like: fixed_inputs model_i::get_fixed_inputs( std::istream& input) const { size_t inputs = 7; std::string buffer; while (inputs>0 && input.good()) { input >> buffer; if ( buffer.substr(0, sizeof("input1")) == "input1=") { std::istringstream is(buffer.substr(0, sizeof("input1"))); is >> .... ; /// pseudo-code : stores the value into a field in fixed_input1s // if wrong value, throws an exception } else if ... ... } return fixed_inputs( new input_i_s() ); // pseudo-code, say for model number i } I would like then to write the implementation for the syntax which accepts ranges as well. (the get_variable_inputs function) I hope to be able to factorize code between the 2 implementations. 1. boost::program_options can read options from input streams. Given that I am interested in ranges as well, is it adviced to go down that road? 2. Is there a library that helps to generate the expected format of the input stream from the struct of inputs for each model, and reads the stream automatically. Can it do range values as well? 3. is it possible then to factorize code between the get_fixed_inputs and get_variable_inputs? Regards,

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(no subject)
by Michael Fowler 18 Dec '09

18 Dec '09

Hello. I tried using the code provided here: http://www.boost.org/doc/libs/1_41_0/doc/html/boost_asio/example/echo/block… to echo text back to a client but i haven't been successful. It seems to hang at size_t length = sock->read_some(boost::asio::buffer(data), error); what is wrong? Thanks

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Function template specialization
by Surya Kiran Gullapalli 18 Dec '09

18 Dec '09

Hello all, The following question may not be related to boost, but if a solution can be found with boost or otherwise would be great. I've a base class with a function template. I derive from base class and try to have a specialization for the function template in derived class I did something like this. ////////////////////////// Header file begin ////////////////////////// class Base { .. template <typename T> fun (T arg) { ... } }; class Derived : public Base { ... } ; template <> Derived::fun(int arg); ///////////////////////// Header file end //////////////////////////// and in .cpp file I've provided implementation for the template specialization. This works fine with MSVC 8.0 and g++ complains about lack of function declaration fun in Derived class. I do not know which compiler is behaving correctly. Any help in this is greatly appreciated. Thanks in advance, Surya

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boost lambda and bind
by Conoscenza Silente 18 Dec '09

18 Dec '09

Hi All I am trying to use boost lambda for looping over a std::map to get each element and pass those to a class function using lambda functions. I don't know why but the binding inside my std::for_each is not compiling and I have 2 errors pointing to the line where boost::assign is used. 'invalid initialization of reference of type int&' 'invalid initialization of reference of type std::basic_string<>&' Do you know how to fix this and why it is happening Thank you very much Regards CS //Boost //#include<boost/assign/std/map.hpp> #include<boost/assign/list_of.hpp> #include<boost/lambda/lambda.hpp> #include<boost/lambda/core.hpp> #include<boost/lambda/bind.hpp> #include<boost/lambda/construct.hpp> class CInnerClassHandler{ public: void DoSomething( int aIntValue, const std::string& aStringValue ){ std::cout << "INT:" << aIntValue << "STRING:" << aStringValue << std::endl; // here we just trace } }; void map_lambda_test(){ typedef std::pair< int, std::string > this_pair; std::map< int, std::string > dictionary = boost::assign::map_list_of(3,"A")(4,"B")(5,"C"); // Errors points to // this line of code CInnerClassHandler obj; std::for_each( dictionary.begin(), dictionary.end(), boost::lambda::bind( &CInnerClassHandler::DoSomething, &obj, boost::lambda::bind(&this_pair::first, boost::lambda::_1), boost::lambda::bind(&this_pair::second,boost::lambda::_1)) ); }

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Build boost for i686 (instead of i386)
by Christoph Duelli 18 Dec '09

18 Dec '09

What do I have to pass to bjam to build Boost with i686 instead of the default i386 as cpu? (I am using Linux, with gcc 4.3.2) So far I am calling ./bjam architecture=x86 address-model=32 Best regards Christoph

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Re: [Boost-users] [Boost.Test] valgrind complains about invalid reads
by Scott Banachowski 18 Dec '09

18 Dec '09

Thanks for the reply Gennadiy, see inline for comments: --- On Wed, 12/16/09, Gennadiy Rozental <rogeeff(a)gmail.com> wrote: > From: Gennadiy Rozental <rogeeff(a)gmail.com> > Subject: Re: [Boost-users] [Boost.Test] valgrind complains about invalid reads > To: boost-users(a)lists.boost.org > Date: Wednesday, December 16, 2009, 9:32 PM > Scott Banachowski <sbanacho > <at> yahoo.com> writes: > > > > > > > I agree with Peter here, the destructor for test_unit > should be virtual. > > 'Should' is a strong statement. Do you have anything to > based it on? > Ok, should is too strong. Change that to "it would be nice to", because the possibility that the base class destructor may be called (even if not by your code, possibly by others). > > I find that it is being deleted when > > test_unit* is a stored in reference counted pointer, > > Where? My mistake, it's held in a map. See the next comment: > > > and at program exit it is being deleted by calling > ~test_unit(). > > Where do I call destructor explicitly? You don't. It's being called implicitly at program exit, by valgrind. I think what is happening is that valgrind replaces the delete operator with its own, which is "operator delete(void*)" The typeinfo is likely lost by this replacement of delete. Just because you don't call the destructor, it doesn't mean others won't. If a base class is derived from, best practice is to declare its destructor virtual. It is relatively common to replace allocators (e.g. tcmalloc). > > > If you use a derived class (test_suite), this is > leading to an error. > > Where? As already mentioned, reported by valgrind. > > > Also, in the code I'm looking at (1.40.0), the > test_suite class has a > > virtual destructor, but its base class test_unit > does not. > > Not making the base class virtual seems to be > defeating the purpose. > > What purpose? The only reason that test_suite destructor is > virtual is because > this class in fact is being polymorphically. It has > subclass master_test_suite. > By defeating the purpose, I mean it forces code like the following: if( ut_detail::test_id_2_unit_type( tu.second->p_id ) == tut_suite ) delete static_cast<test_suite const*>(tu.second); else delete static_cast<test_case const*>(tu.second); A virtual base case simplifies this code (especially if in the future other classes are added, or in the case of replacement allocator it does the right thing). thanks, Scott > Gennadiy > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users > __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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[serialization] object tracking for shared strings
by Nils Krumnack 17 Dec '09

17 Dec '09

Hi all, I hope one of you will be able to help me with this: I am working with a data structure that contains a large number of (mostly identical) strings. To save memory I put together a shared memory string implementation, which ensures that each string is kept in memory only once (implemented through a global map with all strings). However, once I write them to disk, I again have n copies of each string. I would really prefer, if I could avoid the space overhead. At first glance, object tracking seems to be the way to go. If my strings were tracked, there would automatically be only one copy of each string. However I can't quite figure out how. I don't really want to change the global tracking behavior for std::string, since that might end up affecting code all over the place. Serializing pointers would be an option, but then I would have to deal with the issue of when to deallocate that object. I suppose I could serialize shared pointers, but then I would have to change my implementation to use shared pointers internally. Alternatively I could also wrap a struct around the strings internally and turn on tracking for that struct, but again I would have to complicate my implementation for the sake of serialization. What I was hoping to find was some way of telling the archive at the point where I am serializing the object, that it should track this one object. I am thinking of something like ar & BOOST_SERIALIZATION_TRACK_THIS (mystring); I was looking for something like that in the documentation, but wasn't very successful. Any ideas? Thanks in advance for any help, Nils

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are boost::interprocess containers thread-safe?
by blp330 17 Dec '09

17 Dec '09

Hi, I must implement a multiple producer-consumer IPC application in win32 (but will port to linux in near future). I am wondering whether the boost::interprocess container like list, vector or map is thread-safe (actually, interprocess-safe?) or I need to use lock in my producer-consumer application? I mean, can Producer just simply put shared memory string to container and take it from Consumer without any lock? Or is there any multiple producer-consumer example that uses boost::interprocess? Thanks a lot. -- View this message in context: http://old.nabble.com/are-boost%3A%3Ainterprocess-containers-thread-safe--t… Sent from the Boost - Users mailing list archive at Nabble.com.

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[proto] extends example not compiling
by alfC 17 Dec '09

17 Dec '09

Is this example, contained in the boost.Proto manual supposed to compile? #include<complex> #include <boost/proto/core.hpp> #include <boost/proto/context.hpp> #include <boost/proto/debug.hpp> #include<boost/proto/extends.hpp> template<class T, class Dummy = boost::proto::is_proto_expr> struct my_complex { BOOST_PROTO_EXTENDS( typename boost::proto::terminal<std::complex<T> >::type , my_complex<T> , boost::proto::default_domain ) }; int main() { my_complex<int> c0, c1; c0 + c1; // OK, operator+ found now! } I get this error (with gcc 4.3 and gcc 4.4): proto_complex.cpp:10: error: expected nested-name-specifier before ‘typename’ proto_complex.cpp:10: error: two or more data types in declaration of ‘proto_base_expr’ proto_complex.cpp:10: error: ‘proto_base_expr’ has not been declared proto_complex.cpp:10: error: ‘proto_base_expr’ has not been declared The strangest thing is that when I replace the macro by its explicit code the code seems to compile. Thank you, Alfredo

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[Re: ] boost.plot: integrating plotting in a C++ native application: general questions about which tools to use
by Richard Ulrich 17 Dec '09

17 Dec '09

Hi Hicham, another possibility is to use a webapp like Wt from http://webtoolkit.eu It's great to work with and has good support for 2D plots. As for the 3D: I've been thinking about that as well for a whild especially embedded in an interactive webpage. I came across openVRML which looks promising, but is a hell of a beast to build (the supporting libraries). So no experiences yet. Rgds Richard

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newbie - graph library - vertex properties
by List User 17 Dec '09

17 Dec '09

Hi 1. In the creation of adjacency list, vertex properties and edge properties could be vecS, listS etc.But how will one access this vertex_properties vector, for example? 2. In the kevin-bacon2.cpp example file available with boost distribution, a struct is used to store vertex properties. But that example does not seem to have used boost_install_property or property_map etc. I thought one would need to use them for having new properties for the vertex. 3. In the kevin-bacon2.cpp approach for adding new properties to the graph, the vertex_properties are read as adjacency_list[vertex_descriptior]. How will have a read only access in such a case? When I use this in a function which is defined as const in c++, the compiler cribs :)Thanks suresh

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[asio] Socket closed notification?
by Nicola Michael Gutberlet 17 Dec '09

17 Dec '09

Hello everybody, I'm using TCP sockets and wonder, if there's a possibility to get an automatic notification when one side of a socket is closed (even if the other side is crashed / not closed properly). Thanks in advance for any help. Regards, Nicola

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Re: [Boost-users] [Boost.Test] valgrind complains about invalid reads
by Scott Banachowski 17 Dec '09

17 Dec '09

I agree with Peter here, the destructor for test_unit should be virtual. I find that it is being deleted when test_unit* is a stored in reference counted pointer, and at program exit it is being deleted by calling ~test_unit(). If you use a derived class (test_suite), this is leading to an error. Also, in the code I'm looking at (1.40.0), the test_suite class has a virtual destructor, but its base class test_unit does not. Not making the base class virtual seems to be defeating the purpose. Scott

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Interfaces in C++
by Jerry Jeremiah 16 Dec '09

16 Dec '09

Hello, I am really interested in interfaces ever since Google's new Go language brought them to my attention. Who would have guessed they are a really old thing? Joel posted some code based on fusion that does interfaces at http://lists.boost.org/Archives/boost/2005/06/89418.php but it is based on a version of fusion before it became a separate library. I have fiddled with it trying to get it to compile against the trunk but I guess I just don't understand enough about fusion to get it going. :-( If Joel or some other fusion guru could tell me how to change it to get it to compile with the current version of fusion I would really appreciate it. Besides getting the ability to play with interfaces hopefully I will gain more in depth knowledge of how to use fusion... Jerry

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boost graph library, default_dfs_visitor, dfs
by List User 16 Dec '09

16 Dec '09

Hi Please see the code below. class my_visitor: public default_dfs_visitor { public: my_visitor(){} void finish_vertex(Vertex u, const Graph & g); vector<Vertex> getFinishingOrder(void){return finishingOrder;} //private: vector<Vertex> finishingOrder;//stores the vertices in the finishing order }; template<typename Vertex, typename Graph> void my_visitor::finish_vertex(Vertex u, const Graph & g){ finishingOrder.push_back(u); } main.cpp has the following: my_visitor vis; depth_first_search(g, visitor(vis));//to get the finishing order on vertices cout << "size of fin vector = " << vis.finishingOrder.size() << endl; My problem: size of the finishingOrder vector is zero outside the my_visitor::finish_vertex method. I checked its size inside the my_visitor::finish_vertex method and its value is increasing... Does I miss something in the understanding of the visitor concept? Thanks suresh

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[GIL] Change layout type of a pixel...
by Eloi Du Bois 16 Dec '09

16 Dec '09

Hi all, I would like to know how to change the layout of a given pixel type. For example, I would like to do something like: // Pixel = rgb16_pixel_t for example. template<class Pixel> void foo(Pixel & A) { typedef typename pixel<hsl_t, Pixel::bits>::type hsl_pixel_t; hsl_pixel_t a; color_convert(A, a); } Thank you by advance, Eloi.

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[GIL]
by Eloi Du Bois 16 Dec '09

16 Dec '09

Hi all, Sorry to bother you with my problems but I am experiencing a new probable bug: I am trying to manage with data that are set as follow: P;P;P;P;...... Where P is a rgb pixel (10 bits per components) packed on an uint32 as follow: 00RGB;00RGB;00RGB;00RGB........ I mean there is two bits unused on each 32 bits pixel. So I tried to set up a view using packed_pixel and a bug occurs when using copy_and_convert_pixels... The very strange thing is that it is working when using color_convert on two pixels... I think there may exist something I didn't understood... Anyway, I give you the buggy code: /// 10 bits rgb packed to uint32_t starting at the 2nd bit typedef const packed_channel_reference<uint32_t, 22, 10, true> rgb10_packed_channel0_t; typedef const packed_channel_reference<uint32_t, 12, 10, true> rgb10_packed_channel1_t; typedef const packed_channel_reference<uint32_t, 02, 10, true> rgb10_packed_channel2_t; typedef mpl::vector3<rgb10_packed_channel0_t, rgb10_packed_channel1_t, rgb10_packed_channel2_t> rgb10_packed_channels_t; typedef packed_pixel<uint32_t, rgb10_packed_channels_t, rgb_layout_t> rgb10_packed_pixel_t; typedef view_type_from_pixel<rgb10_packed_pixel_t>::type rgb10_packed_view_t; // image data of dimension: {w,h} = {1,0} uint32_t *data=new uint32_t[1]; data[0] = 0xFFFFF00C; rgb10_packed_view_t vw10 = interleaved_view( 1, 0, (rgb10_packed_pixel_t*)( data ), sizeof( uint32_t ) ); rgb10_packed_pixel_t pix10 = *vw10.row_begin(0); rgb16_pixel_t pix16; // This is working color_convert(pix10, pix16); std::cout << "Right {R,G,B}={" << get_color(pix16, red_t()) << "," << get_color(pix16, green_t()) << "," << get_color(pix16, blue_t()) << "}" << std::endl; // Assert that are ok assert( get_color( pix16, red_t() ) == 0xFFFF ); assert( get_color( pix16, green_t() ) == 0xFFFF ); assert( get_color( pix16, blue_t() ) == 0x00C0 ); rgb16_image_t img16(vw10.width(), vw10.height()); rgb16_view_t vw16(view(img16)); // This isn't working with packed_view copy_and_convert_pixels(vw10, vw16); pix16 = *vw16.row_begin(0); std::cout << "Wrong {R,G,B}={" << get_color(pix16, red_t()) << "," << get_color(pix16, green_t()) << "," << get_color(pix16, blue_t()) << "}" << std::endl; // Assert that doesn't pass assert( get_color( pix16, red_t() ) == 0xFFFF ); assert( get_color( pix16, green_t() ) == 0xFFFF ); assert( get_color( pix16, blue_t() ) == 0x00C0 ); Hope this will help, Eloi.

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boost.plot: integrating plotting in a C++ native application: general questions about which tools to use
by Hicham Mouline 16 Dec '09

16 Dec '09

Hello, I am writing an application with a native C++ computation engine (library) that generates plotable data 2d and 3d, and a plotting engine. I am trying to determine what tools/libraries to use for the plotting engine. My graphs are all time series in the x axis (typically dates but maybe day numbers). I have a y axis and sometimes a z axis as well. Data is available in std::vector/list< pair<> > or std::vector/list< boost::tuple<> >, sometimes std::map<k,v>, perhaps later boost::multi_array<2> or <3> as well, or in fact just native arrays of pairs or boost::tuples. Decisions are made by the users, tweaking parameters and seeing how the plots change. The application user interface will be as: 1. win command line and just the plotting being graphical 2. Linux command line and just the plotting being graphical 3. win .net interface - input of parameters to the computing engine, and the plotting being graphical 4. Linux with X (maybe gtk/qt) - input of parameters to the computing engine, and the plotting being graphical And the results of the computation will then need to be plotted. So far, I have seen these solutions: ***1 - With 1,2,3 and 4, I can see a write the numbers to a file, call the external process on windows that runs gnuplot that runs a script file to plot the file. Both 2D (y(x)) and 3D(z(x,y)) visualizations are pretty flexible, in particular 3D visualizations allow to rotate the graph and view from different angles. But this process seems tortuous, gnuplot accepts piped data on linux but not on windows without mingw/cigwin. It would be preferable to not generate intermediary files, especially if that is very large. There is also a gnuplot c++ interface, but that doesn't avoid running the gnuplot external process. ***2 - I've come across boost.plot and it generates svg files which have only 2D if I understood correctly, SVG doesn't express 3D, and then use a browser (chrome) or that tool that uses SVG as its native format, or use ImageDisplay for e.g.( this comes with c++ dev library, perhaps that helps to plot directly the svg without running the process externally ) Cons: no 3d (rotating and different angles) and still require external programs. ***3 - I don't know .net but it seems c# is more convenient for the GUI part (inputting parameters, selecting options), running the c++ computation engine, and .net probably has some plotting part (don't know about 3D plots and rotating though) Cons: non portable solution - how would c# plotting interact with native c++ stl? ***4 - gtk/qt : does it have plotting features? It is ported to linux and win, does the windows port requires cygwin/mingw? How does it interact with STL containers? The solution is ideally the quickest-to-deploy and most portable, with windows not requiring cygwin/mingw, and not needing to run an external process. The need for portability comes from hardware requirements machines with a large number of processor cores run linux, while smaller boxes run win. I appreciate there are a lot of questions here, that deal with many topics and I thank everyone for answers or suggestions, Regards,

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[boost-users][asio] async operations order.
by Germán Diago 16 Dec '09

16 Dec '09

Hello. I'm implementing a fully asynchronous server and I would like to know the order of async operations. The server receives, first of all, a size, and later the data. The onSizeRead handler allocates the memory required to store the data that is coming after the async_read. So I would like to know if this buffer will be available when onDataRead is called. so I get the size and data with two async_read operations. I would like to know if the relative order of the async calls is respected, since I'm reading from the same socket for both operations and I need the resources dictated by the first read before using the second one.

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Compiler crash with Phoenix and PropertyTree.
by Surya Kiran Gullapalli 16 Dec '09

16 Dec '09

Hello all, I'm seeing a compiler crash (MSVC 8.0) with the following piece of code. I'm using Boost.Phoenix along with Boost.PropertyTree namespace pt = boost::property_tree ; pt::ptree tree ; boost::phoenix::bind (&pt::ptree::put<string, bool>, tree, string("Temp.Flag"), true) ; Attached is the build log. Actually, this is a test program, I wrote to reproduce a C4180 warning, but I see a crash here (actually I see C4180 also) Let me know if I'm doing something wrong. Thanks, Surya

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is visitor object destroyed immediately after the execution of depth_first_search?
by Suresh Kumar 16 Dec '09

16 Dec '09

Hi, my idea is to get the finishing order of vertices in dfs by pushing the vertices in a vector and return it later through a function return value from my visitor class object. //code snippet int main() { my_visitor vis; depth_first_search(g, visitor(vis)); cout << "size of fin vector = " << vis.finishingOrder.size() << endl; //i get zero here!!! } class my_visitor: public default_dfs_visitor { public: my_visitor(){} void finish_vertex(Vertex u, const Graph & g){finishingOrder.push_back(u);}; vector<Vertex> getFinishingOrder(void){return finishingOrder;} private: vector<Vertex> finishingOrder; }; My problem: size of the finishingOrder vector is zero outside the my_visitor::finish_vertex method. I checked its size inside the my_visitor::finish_vertex method and its value is increasing every time a vertex is finished. Does I miss something in the understanding of the visitor concept? Thanks suresh -- R. Suresh Kumar PhD Student, Vislab #216, Engineering II Bldg University of California, Riverside, CA 92521

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[phoenix] A simple lambda func as boost::function
by Richard Vock 16 Dec '09

16 Dec '09

Hi boost gurus, after some time and a lot of pain I somehow managed to work with boost.lambda in a way that actually outweighs the costs (code elegance versus time spent compiling it), but I miss some features (like local variables) I see in that cute phoenix documentation and a lot of mailing list threads which all seem to propose using phoenix rather than lambda (and it indeed looks a lot better). But whenever I try to use it, I somehow fail at the most simple tasks. Take for example this minimalistic code example here (note the use of #define USE_LAMBDA): http://pastebin.com/m3f590a01 Both versions (with and without USE_LAMBDA defined) compile well on the most recent stable g++ compiler, but the phoenix version does not output anything. Not at all. Also note, that this exact lambda expression is mentioned here: http://tinyurl.com/ybmp2lw (well, without the << "\n" but that doesn't change the problem) Could someone please enlighten me by telling me what I have to do here? I should mention I am bound to boost::function, not some funky phoenix::actor derivations... Greets, Richard Vock

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