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[BGL] Confusion about iterator_property_map and initialization of OffsetMap
by Cedric Laczny 03 Apr '11

03 Apr '11

Hi, I have modified the astar-cities.cpp example to use an external rank_map based on iterator_property_map. The following should give you an idea: vector<cost> v_vec(num_vertices(g), 0.0); typedef property_map< mygraph_t, vertex_index_t>::type VertexIndexMap; VertexIndexMap v_index = get(vertex_index, g); // Initialization of interest // Create the external property map typedef iterator_property_map< std::vector< cost >::iterator, VertexIndexMap > CostMap; CostMap c_map(v_vec.begin(), v_index); and the function-call of astar_search is as follows: astar_search (g, start, distance_heuristic<mygraph_t, cost, location*, const char**> (locations, goal, name), predecessor_map(&p[0]).distance_map(&d[0]). visitor(a_star_vis). rank_map(c_map)); // Here we use the "global" cost map Basically, the code is the same as in the example, with only the addition of the explicit rank_map. Now I am fairly confused that the function call seems to behave the same if I have "get(vertex_index, g)" and if I don't have it. This comes unexpected to me as I would think that it needs OffsetMap (v_index) to correctly find the index in the random access container (v_vec). But when I simply declare an object it is not yet initialized and will not contain any meaningfull offsets (not using "get(vertex_index, g)"). So why does it work, when the map is not initialized? Or what am I missing here please? Best, Cedric

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[MPL] no invoke<T>?
by Noah Roberts 03 Apr '11

03 Apr '11

I had to write an invoke metafunction because I couldn't seem to find one that looked like it was what I needed: template < typename MF > struct invoke { typedef typename MF::type type; }; I've looked through the documentation TOC: http://www.boost.org/doc/libs/1_42_0/libs/mpl/doc/refmanual/refmanual_toc.h… Is there something I'm missing?

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questions regarding boost::mem_fn and boost::bind
by Littlefield, Tyler 02 Apr '11

02 Apr '11

Hello all: I have a quick question. I was trying to learn how to use boost::mem_fn to work as a sort of function object, because I need something like this for my library. So: If I understand this correctly, it creates a function object that has () overloaded, correct? I was curious if someone could then help me figure this out, the documentation is confusing for me. lets say I have this class: class Foo { public: int Add(int a, int b) { return (a+b); } }; and I could do Foo bar; how would I create a mem_fn named f, that would let me call it for add? so: f(3,1). I would have to tie the instance of foo (bar) to this somehow, correct? Next, I see that mem_fn creates a function object which basically does what I want. What then is the point in boost::bind? It looks to do about the same as mem_fn, just makes my head hurt a little bit more. I am trying to learn boost by finding uses for some of the libraries. Some of them sort of makes sense, but I see that mem_fn are the bases for a lot, so I wanted to learn how to use those. After bind and mem_fn, what other libraries would it be best to learn that is used all over? Last, this is the use I will be putting mem_fn to. If this is incorrect, I still want to learn, but it looked like a great example. I am writing a quick socket class that will have connect, close, and send capabilities. I am hooking this to my game engine, and wanted to use a mem_fn to receive the data. So the server polls all user input, then it will poll the sockets that were added to another list. It will pass off any data read by calling the function object with the data as an argument, as well as the socket. Sorry for all the questions, and thanks in advance for the help/clarification. -- Thanks, Ty

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VS2010+boost 1.44 - error in move.hpp
by archie14 02 Apr '11

02 Apr '11

While compiling the project in VS2010 previously built without errors in VS2008 I am getting following error: c:\libraries\boost\boost_1_44_0\boost\interprocess\detail\move.hpp(342): error C2440: 'return' : cannot convert from 'boost::interprocess::file_mapping' to 'boost::interprocess::file_mapping &&' You cannot bind an lvalue to an rvalue reference c:\libraries\boost\boost_1_44_0\boost\interprocess\file_mapping.hpp (62) : see reference to function template instantiation 'boost::interprocess::file_mapping &&boost::interprocess::move<boost::interprocess::file_mapping&>(T)' being compiled with [ T=boost::interprocess::file_mapping & ] I tried to search the forum for the reports on this error and did not find anything. I'll appreciate any help in this matter.

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[boost] [program options] Potential bug in parsing arguments where one is suffix of the other ?
by Sanjit Jhala 02 Apr '11

02 Apr '11

Hi, I have the following code (modified from example/first.cpp): *#include <boost/program_options.hpp>* *#include <string>* *#include <vector>* *#include <iostream>* * * *namespace po = boost::program_options;* * * *using namespace std;* * * *typedef vector<string> Strings;* * * *// A helper function to simplify the main part.* *template<class T>* *ostream& operator<<(ostream& os, const vector<T>& v)* *{* * copy(v.begin(), v.end(), ostream_iterator<T>(cout, " "));* * return os; * *}* * * * * *int main(int argc, char *argv[]) {* * * * po::options_description cmdline_desc("Usage: %s [Options] [args]\nOptions");* * cmdline_desc.add_options()* * ("str", po::value< string >(), "a string arg")* * ("strs", po::value< Strings >(), "a list of strings")* * ("foo", po::value< string >(), "a string arg")* * ("bar", po::value< Strings >(), "a list of strings")* * ; * * * * po::variables_map vm; * * po::store(po::parse_command_line(argc, argv, cmdline_desc), vm);* * po::notify(vm);* * * * if (vm.count("str"))* * cout << "Got str arg=" << vm["str"].as< string >() << "\n";* * if (vm.count("strs"))* * cout << "Got strs arg=" << vm["strs"].as< Strings >() << "\n";* * if (vm.count("foo"))* * cout << "Got foo arg=" << vm["foo"].as< string >() << "\n";* * if (vm.count("bar"))* * cout << "Got bar arg=" << vm["bar"].as< Strings >() << "\n";* *}* * * When I run the program I see: *./po_test --str "a string" --strs "a, vector, of, strings" --foo "a foo" --bar "a, bar"* *Got strs arg=a string a, vector, of, strings * *Got foo arg=a foo* *Got bar arg=a, bar * It appears the parser is getting confused between the "str" and the "strs". It doesn't seem to be related to ambiguity in handling vectors since the "foo" and "bar" arguments are fine. I see this problem on 32-bit CentOS and Ubuntu machines, but not on 64-bit. I am running Boost 1.43 and from the /usr/local/include/boost/program_options/version.hpp: #define BOOST_PROGRAM_OPTIONS_VERSION_HPP_VP_2004_04_05 #define BOOST_PROGRAM_OPTIONS_VERSION 2 Is this a bug or a expected behaviour? -Sanjit

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Boost Graph/Subgraph: Making a "layered graph"
by Frank Neuhaus 02 Apr '11

02 Apr '11

Hi, I want to represent a graph that consists of several layers. I have an algorithm that is supposed to be run on each layer seperately. I thought about having all layers in one graph, but each layer in a subgraph of this graph. That way - I thought - I could leave the algorithm that works on one layer unchanged. First off: Is that a reasonable design? Is there a different way to achieve what I want? Maybe there is another way to pass a subset of the graph to my algorithm? Now as for the actual problem with boost subgraphs: My current code (for one layer only) looks similar to this: ---- struct my_vertex { int x; }; struct my_edge { int y; }; typedef boost::adjacency_list<vecS, listS, undirectedS, my_vertex, my_edge> NormalGraph; NormalGraph ng; NormalGraph::vertex_descriptor vd=add_vertex(ng); ng[vd].x=5; ---- So as you can see I am using bundled properties. Now I want to create the same thing with subgraphs. Just doing ---- typedef boost::subgraph<boost::adjacency_list<vecS, listS, undirectedS, my_vertex, my_edge> > SubGraph; ---- Did not work and I suspected it was due to the problem mentioned in the "Notes" section at the very bottom of [1] - which I dont quite understand to be honest. I still tried to use the workaround that is mentioned there: ---- struct my_vertex { int x; }; struct my_edge { int y; }; typedef boost::property<boost::vertex_index_t, std::size_t, my_vertex> vertex_prop; typedef boost::property<boost::edge_index_t, std::size_t, my_edge> edge_prop; typedef boost::adjacency_list<vecS, listS, undirectedS, vertex_prop, edge_prop> Graph; typedef boost::subgraph<Graph> Subgraph; Subgraph sg; Subgraph::vertex_descriptor vd=add_vertex(sg); sg[vd].x=5; // doesnt work - why? auto pm=get(boost::vertex_bundle,sg); my_vertex vert; vert.x=7; put(pm,vd,vert); // doesnt work - why? ---- Now I do not understand how to access my vertex and edge properties as you can see... Neither using [] nor accessing via property maps appears to work. What am I doing wrong here? I couldnt find any documentation or examples on this :( Thanks a lot Frank [1] http://www.boost.org/doc/libs/1_46_0/libs/graph/doc/subgraph.html

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[Graph] Topological sort compilation error
by Bruno Morais 01 Apr '11

01 Apr '11

Hi, I got some problems trying to compile a topological sort code. I created my graph with the color properties but I got the error: error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'boost::detail::error_property_not_found' (or there is no acceptable conversion) So, I tried the example at boost_1_46_1\libs\graph\example\topo_sort.cpp. It works fine, but with a little change I could reproduce the error. I change the following code at line 43: typedef adjacency_list<vecS, vecS, directedS, property<vertex_color_t, default_color_type> > Graph; to typedef adjacency_list<vecS, listS, directedS, property<vertex_color_t, default_color_type> > Graph; Should the vertex list selector influence on that? I tried Boost 1.46.1 and got the error with both compilers: Microsot Visual Studio 2008 version 9.0.21022.8 RTM and Intel® C++ Compiler Version 11.1.850.2008 I attached the modified version of the file. With Kind Regards, Bruno

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Re: [Boost-users] Boost-users Digest, Vol 2679, Issue 1
by Shah, Gaurav N 01 Apr '11

01 Apr '11

Thanks Andreas Wehrmann. if worked after including boost/function.hpp. I am still wondering what changes boost has made while moving from 1.41 to 1.44 that has made users to explicitly include "function.hpp" This code was compiling with 1.41 without including boost/function.hpp Thank You, Gaurav -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of boost-users-request(a)lists.boost.org Sent: Friday, April 01, 2011 11:34 AM To: boost-users(a)lists.boost.org Subject: Boost-users Digest, Vol 2679, Issue 1 Send Boost-users mailing list submissions to boost-users(a)lists.boost.org To subscribe or unsubscribe via the World Wide Web, visit http://lists.boost.org/mailman/listinfo.cgi/boost-users or, via email, send a message with subject or body 'help' to boost-users-request(a)lists.boost.org You can reach the person managing the list at boost-users-owner(a)lists.boost.org When replying, please edit your Subject line so it is more specific than "Re: Contents of Boost-users digest..." Today's Topics: 1. Re: [boost::mutex] Do they block or wait? (Ovanes Markarian) 2. Re: [Lambda] nitty gritty detail...? (Robert Jones) 3. Re: [Lambda] nitty gritty detail...? (Steven Watanabe) 4. VS2010+boost 1.44 - error in move.hpp (archie14) 5. [boost] [program options] Potential bug in parsing arguments where one is suffix of the other ? (Sanjit Jhala) 6. [MPL] no invoke<T>? (Noah Roberts) 7. Re: Problem with gcc/4.5.0-g++and boost::function (Andreas Wehrmann) ---------------------------------------------------------------------- Message: 1 Date: Thu, 31 Mar 2011 20:21:29 +0200 From: Ovanes Markarian <om_boost(a)keywallet.com> To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [boost::mutex] Do they block or wait? Message-ID: <AANLkTim_=MZAk0WwoerK7-TCRAGpN0Gdgcr+DDV5uhOA(a)mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" On Thu, Mar 31, 2011 at 7:49 PM, Steven Watanabe <watanabesj(a)gmail.com>wrote: > AMDG > > > On 03/31/2011 09:55 AM, Panagiotis Foteinos wrote: > >> I looked into the documentation, but it is still unclear to me. >> >> [...] > > boost's locking mechanism >> blocking or spinning? >> >> > It's an implementation detail. You realize that the > two aren't necessarily mutually exclusive? Anyway, > Boost.Thread does block on an Event. A spin-lock > only makes sense on a multi-core system. > > In Christ, > Steven Watanabe > As Steven pointed out it is an implementation detail and these two concepts might be used together (primarily for optimization). Switching to kernel mode (e.g. dealing with kernel objects like event, mutex, semaphore through system calls) is a very time costly operation, therefore some libs provide spinning optimizations, which do spinning (for some few cpu cycles) and if they are still unable to acquire a lock, they make a system call which changes into the kernel mode and finally puts the thread into the blocked state if the object is still not available (signaled, unlocked etc). But even so it is not black and white in the concurrency world. :( Some would like to achieve speed through such an optimization others would like to get rid of such an optimization. A good example might be an embedded app running on a battery driven HW, where energy plays a major role. Here wasting CPU cycles for speed optimization might not be a good idea... But anyway that should be separately evaluated. With Kind Regards, Ovanes -------------- next part -------------- HTML attachment scrubbed and removed ------------------------------ Message: 2 Date: Thu, 31 Mar 2011 19:27:30 +0100 From: Robert Jones <robertgbjones(a)gmail.com> To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [Lambda] nitty gritty detail...? Message-ID: <AANLkTinfsOJmqrWBP16+7s2c+YufKcW3GwcHapxttLqq(a)mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" On Thu, Mar 31, 2011 at 4:47 PM, Steven Watanabe <watanabesj(a)gmail.com>wrote: > AMDG > > > On 03/31/2011 08:29 AM, Robert Jones wrote: > >> From Bjorn Karlsson's book, P297... >>> >> >> int i; >> int value = 12; >> var(i) = ( if_then_else_return( _1>=10, constant(10),_1) )(value); >> >> Why does the assignment LHS need to be wrapped in var()? >> >> > Because operator= must be a member function. > > Nope, still not getting it! Stop me when I err... if_then_else_return(...) defines a unary functor it_then_else_return(...)( value) evaluates that functor, and returns what? Some type of integer I think? So doesn't the assignment simply perform assignment of an integer, by copy? And that doesn't need operator= to a member of anything? Thanks - R. -------------- next part -------------- HTML attachment scrubbed and removed ------------------------------ Message: 3 Date: Thu, 31 Mar 2011 11:38:33 -0700 From: Steven Watanabe <watanabesj(a)gmail.com> To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [Lambda] nitty gritty detail...? Message-ID: <4D94CA29.9060307(a)providere-consulting.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed AMDG On 03/31/2011 11:27 AM, Robert Jones wrote: > On Thu, Mar 31, 2011 at 4:47 PM, Steven Watanabe<watanabesj(a)gmail.com>wrote: >> >> On 03/31/2011 08:29 AM, Robert Jones wrote: >> >>> From Bjorn Karlsson's book, P297... >>>> >>> >>> int i; >>> int value = 12; >>> var(i) = ( if_then_else_return( _1>=10, constant(10),_1) )(value); >>> >>> Why does the assignment LHS need to be wrapped in var()? >>> >>> >> Because operator= must be a member function. >> >> > Nope, still not getting it! Stop me when I err... > > if_then_else_return(...) defines a unary functor > it_then_else_return(...)( value) evaluates that functor, and returns what? > > Some type of integer I think? Yes. > So doesn't the assignment simply perform > assignment of an integer, by copy? And that doesn't need operator= to > a member of anything? > Oh, I see. As written, the code doesn't make much sense, so my mind automatically translated it into (var(i) = if_then_else_return( _1>=10, constant(10),_1) )(value); In Christ, Steven Watanabe ------------------------------ Message: 4 Date: Thu, 31 Mar 2011 22:56:11 +0000 (UTC) From: archie14 <admin(a)tradeplatform.us> To: boost-users(a)lists.boost.org Subject: [Boost-users] VS2010+boost 1.44 - error in move.hpp Message-ID: <loom.20110401T005027-111(a)post.gmane.org> Content-Type: text/plain; charset=us-ascii While compiling the project in VS2010 previously built without errors in VS2008 I am getting following error: c:\libraries\boost\boost_1_44_0\boost\interprocess\detail\move.hpp(342): error C2440: 'return' : cannot convert from 'boost::interprocess::file_mapping' to 'boost::interprocess::file_mapping &&' You cannot bind an lvalue to an rvalue reference c:\libraries\boost\boost_1_44_0\boost\interprocess\file_mapping.hpp (62) : see reference to function template instantiation 'boost::interprocess::file_mapping &&boost::interprocess::move<boost::interprocess::file_mapping&>(T)' being compiled with [ T=boost::interprocess::file_mapping & ] I tried to search the forum for the reports on this error and did not find anything. I'll appreciate any help in this matter. ------------------------------ Message: 5 Date: Thu, 31 Mar 2011 16:16:25 -0700 From: Sanjit Jhala <sjhalaz(a)gmail.com> To: boost-users(a)lists.boost.org Subject: [Boost-users] [boost] [program options] Potential bug in parsing arguments where one is suffix of the other ? Message-ID: <AANLkTi=bEJWMhNj-wO-9O6SjHORiGkr0xn75pKeJOU4=(a)mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" Hi, I have the following code (modified from example/first.cpp): *#include <boost/program_options.hpp>* *#include <string>* *#include <vector>* *#include <iostream>* * * *namespace po = boost::program_options;* * * *using namespace std;* * * *typedef vector<string> Strings;* * * *// A helper function to simplify the main part.* *template<class T>* *ostream& operator<<(ostream& os, const vector<T>& v)* *{* * copy(v.begin(), v.end(), ostream_iterator<T>(cout, " "));* * return os; * *}* * * * * *int main(int argc, char *argv[]) {* * * * po::options_description cmdline_desc("Usage: %s [Options] [args]\nOptions");* * cmdline_desc.add_options()* * ("str", po::value< string >(), "a string arg")* * ("strs", po::value< Strings >(), "a list of strings")* * ("foo", po::value< string >(), "a string arg")* * ("bar", po::value< Strings >(), "a list of strings")* * ; * * * * po::variables_map vm; * * po::store(po::parse_command_line(argc, argv, cmdline_desc), vm);* * po::notify(vm);* * * * if (vm.count("str"))* * cout << "Got str arg=" << vm["str"].as< string >() << "\n";* * if (vm.count("strs"))* * cout << "Got strs arg=" << vm["strs"].as< Strings >() << "\n";* * if (vm.count("foo"))* * cout << "Got foo arg=" << vm["foo"].as< string >() << "\n";* * if (vm.count("bar"))* * cout << "Got bar arg=" << vm["bar"].as< Strings >() << "\n";* *}* * * When I run the program I see: *./po_test --str "a string" --strs "a, vector, of, strings" --foo "a foo" --bar "a, bar"* *Got strs arg=a string a, vector, of, strings * *Got foo arg=a foo* *Got bar arg=a, bar * It appears the parser is getting confused between the "str" and the "strs". It doesn't seem to be related to ambiguity in handling vectors since the "foo" and "bar" arguments are fine. I see this problem on 32-bit CentOS and Ubuntu machines, but not on 64-bit. I am running Boost 1.43 and from the /usr/local/include/boost/program_options/version.hpp: #define BOOST_PROGRAM_OPTIONS_VERSION_HPP_VP_2004_04_05 #define BOOST_PROGRAM_OPTIONS_VERSION 2 Is this a bug or a expected behaviour? -Sanjit -------------- next part -------------- HTML attachment scrubbed and removed ------------------------------ Message: 6 Date: Thu, 31 Mar 2011 16:32:13 -0700 From: Noah Roberts <roberts.noah(a)gmail.com> To: boost-users(a)lists.boost.org Subject: [Boost-users] [MPL] no invoke<T>? Message-ID: <in32tm$6u3$1(a)dough.gmane.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed I had to write an invoke metafunction because I couldn't seem to find one that looked like it was what I needed: template < typename MF > struct invoke { typedef typename MF::type type; }; I've looked through the documentation TOC: http://www.boost.org/doc/libs/1_42_0/libs/mpl/doc/refmanual/refmanual_toc.h… Is there something I'm missing? ------------------------------ Message: 7 Date: Fri, 01 Apr 2011 08:04:18 +0200 From: Andreas Wehrmann <a.wehrmann(a)centersystems.com> To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] Problem with gcc/4.5.0-g++and boost::function Message-ID: <4D956AE2.4040808(a)centersystems.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed On 03/31/2011 06:42 PM, Steven Watanabe wrote: > AMDG > > On 03/31/2011 09:27 AM, Shah, Gaurav N wrote: >> I have legacy code in my library using boost::function. This works >> fine if I am using gcc/4.2.2-g++ and BOOST/1.41. But if I switch >> myself to using gcc/4.5.0-g++ and BOOST/1.44 I get below ERROR: >> I do not see anything wrong with code. >> >> /export/home/a_besnad/Perforce/eq-thebeast-build-linux-Beast_8.08/TheBeast/marketdata/IMDMXP/server/wombat/management.hpp:69:51: >> error: 'function' in namespace 'boost' does not name a type >> /export/home/a_besnad/Perforce/eq-thebeast-build-linux-Beast_8.08/TheBeast/marketdata/IMDMXP/server/wombat/management.hpp:69:58: >> error: ISO C++ forbids declaration of 'parameter' with no type >> /export/home/a_besnad/Perforce/eq-thebeast-build-linux-Beast_8.08/TheBeast/marketdata/IMDMXP/server/wombat/management.hpp:69:66: >> error: expected ',' or '...' before '<' token >> ../../../../../../marketdata/IMDMXP/server/wombat/management.cpp:126:10: >> error: prototype for 'void datasource::management::stop(const >> std::string&, const boost::function<void()>&)' does not match any in >> class 'datasource::management' >> /export/home/a_besnad/Perforce/eq-thebeast-build-linux-Beast_8.08/TheBeast/marketdata/IMDMXP/server/wombat/management.hpp:69:14: >> error: candidate is: void datasource::management::stop(const >> std::string&, int) >> make[6]: *** [management.lo] Error 1 >> make[6]: *** Waiting for unfinished jobs.... >> >> >> >> Code lines throw ERROR: >> >> 68 */ >> 69 void stop(const std::string& topic, const >> boost::function< void (void)>& action); >> 70 >> >> Thanks for help in advance. >> > > Have you verified that boost/function.hpp > is #included? > > In Christ, > Steven Watanabe > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users This is the first thing I would check, since the compiler has become stricter, meaning indirect inclusions won't work anymore. I ran across the same problem when upgrading from 4.2.x to 4.4.x and 4.5.x respectively. Regards, Andreas -- Dipl.-Ing. (FH) Andreas Wehrmann Software Development -------------------------------------------------------------- Center Communication Systems GmbH A-1210 Wien, Ignaz-K?ck-Stra?e 19 Sitz in Wien FN 796 88p, Firmenbuchgericht Wien www.centersystems.com Tel.: +43 (0) 190 199 - 3616 Mobile: +43 (0) 664 884 75916 Fax: +43 (0) 190 199 - 2110 E-Mail: a.wehrmann(a)centersystems.com ------------------------------ _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users End of Boost-users Digest, Vol 2679, Issue 1 ******************************************** This communication is for informational purposes only. It is not intended as an offer or solicitation for the purchase or sale of any financial instrument or as an official confirmation of any transaction. 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how to link to a specific version of windows CRT
by Mai Zi 01 Apr '11

01 Apr '11

Hi,there, I am using boost 1.42. The default CRT linked by it is like this: name='Microsoft.VC90.CRT' version='9.0.21022.8' Now I want to link to the another version, say, version="9.0.30729.4148", can anybody tell where and how to specify this option when I build the binary from source? Thanks in advance OrNot

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gcc3.4 and boost type trait (is_virtual_base_of) , compile warning
by emeplease 01 Apr '11

01 Apr '11

Hello , I am using boost 1.41 with gcc 3.4 (I know it's pretty old) , I am having problem with "is_virtual_base_of" The following lines of code will reproduce the problem. Thank you very much Joseph ======== test_typetrait.cpp ============== #include <iostream> #include <boost/type_traits/is_virtual_base_of.hpp> class Fruit { }; class Apple : virtual public Fruit { }; int main(int argc,char** argv) { std::cout << std::endl << boost::is_virtual_base_of< Fruit, Apple>::value << std::endl; return 0; } ======== full Compile warning ============== include/boost/type_traits/is_virtual_base_of.hpp: In instantiation of `boost::detail::is_virtual_base_of_impl<Fruit, Apple, mpl_::bool_< true> >::X': include/boost/type_traits/is_virtual_base_of.hpp:70: instantiated from `boost::detail::is_virtual_base_of_impl<Fruit, Apple, mpl_::bool_< true> >' include/boost/type_traits/is_virtual_base_of.hpp:78: instantiated from `boost::detail::is_virtual_base_of_impl2<Fruit, Apple>' include/boost/type_traits/is_virtual_base_of.hpp:87: instantiated from `boost::is_virtual_base_of<Fruit, Apple>' test_typetrait.cpp:119: instantiated from here include/boost/type_traits/is_virtual_base_of.hpp:56: warning: direct base `Fruit' inaccessible in `boost::detail::is_virtual_base_of_impl<Fruit, Apple, mpl_::bool_< true> >::X' due to ambiguity

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