- Boost-users - lists.boost.org

Re: [Boost-users] erase and iterators
by David Klein 11 Jul '06

11 Jul '06

boost-users-bounces(a)lists.boost.org wrote: > On Tue, Jul 11, 2006 at 10:19:05AM +0000, Roman Neuhauser wrote: >> # kneeride(a)gmail.com / 2006-07-11 17:31:23 +1000: >>> On 7/11/06, Michael Nicolella <boost(a)mike-n.com> wrote: >>>> vec.erase( std::remove_if( vec.begin(), vec.end(), >>>> some_condition_functor >>>> ) ); >>> >>> Mike, I do like your remove_if example. >>> >>> i am not familar with this approach, can you please give me an >>> example of defining a some_condition_functor? for example when the >>> value == 5. > > What about this? > > Let's assume the vector contains ints > > class condition_functor { > > public: > > bool operator()(int elem) > { > return elem==5 > } > }; > > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users you can use Boost.Lambda for this #include <boost/lambda/lambda.hpp> using namespace boost::lambda; std::vector<int> v; ... v.erase(std::remove_if(v.begin(), v.end(), 5 == _1)); -- HTH dave

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[serialization] skipping data
by Joel de Guzman 11 Jul '06

11 Jul '06

Hi, Here's a use case that I can't seem to find a way to do using boost.serialization. Say with version 1, I want to serialize X Y and Z. These are hierarchical and expensive data structures. Now, with version 2, I do not need to create Y objects anymore. Yet, I still have to open version 1 files for backward compatibility. So, when loading version 1 files, I want to skip reading Y objects. How do I do that without having to create a temporary Y object that will be discarded later? (I'm particularly interested with XML archives. If I had control over the xml parser, that would simply mean ignoring everything from the current tag until the next matching tag is found). Regards, -- Joel de Guzman http://www.boost-consulting.com http://spirit.sf.net

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[BGL] bipartite graphs
by Heiko Bauke 11 Jul '06

11 Jul '06

Hello, how can I deal with bipartite graphs and BGL? In particular I have the problem that my graph has two kinds of nodes with different kinds of vertex properties. Any suggestions? Heiko -- -- Es gibt vielerlei Lärm. Aber es gibt nur eine Stille. -- (Kurt Tucholsky, dt. Schriftsteller, 1890-1935) -- Cluster Computing @ http://www.clustercomputing.de -- Heiko Bauke @ http://www.uni-magdeburg.de/bauke

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Serialization of boost::any
by Sliwa, Przemyslaw (London) 11 Jul '06

11 Jul '06

Does it exist somewhere? Is it planned at all? Thanks for help Kind regards Pshemek Przemyslaw Sliwa Global Foreign Exchange FX Risk Engine Development Merrill Lynch ( +44 (0)20 7995 4182 ) +44 (0)79 6325 2319 * Email: przemyslaw_sliwa(a)ml.com -------------------------------------------------------- If you are not an intended recipient of this e-mail, please notify the sender, delete it and do not read, act upon, print, disclose, copy, retain or redistribute it. Click here for important additional terms relating to this e-mail. http://www.ml.com/email_terms/ --------------------------------------------------------

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[BGL] conflict with call of boost::source
by Lars Monecke 11 Jul '06

11 Jul '06

Hi, i have reduced my problem to the following lines. I want to install a own edge property to a graph. The property as a template argument with then name "source". Here is my try: ---> code starts here <--- #include <boost/graph/adjacency_list.hpp> namespace Foo { class source { }; } namespace Bar { template <class Source> class Edge { }; } typedef Bar::Edge<Foo::source> tMyEdge; struct edge_impl_t { typedef boost::edge_property_tag kind; }; typedef boost::property <edge_impl_t, tMyEdge> edge_property_t; typedef boost::adjacency_list < boost::listS, boost::vecS, boost::undirectedS, boost::no_property, edge_property_t> tGraph; int main(int /* argc */, char* /* argv[] */) { tGraph stGraph1; tGraph stGraph2; stGraph1 = stGraph2; } ----> code ends here <--- When compiling the above code with gcc 4.1.1, i get these errors: main.cpp: In member function 'void boost::vec_adj_list_impl<Graph, Config, Base>::copy_impl(const boost::vec_adj_list_impl<Graph, Config, Base>&) [with Graph = boost::adjacency_list<boost::listS, boost::vecS, boost::undirectedS, boost::no_property, boost::property<edge_impl_t, Bar::Edge<Foo::source>, boost::no_property>, boost::no_property, boost::listS>, Config = boost::detail::adj_list_gen<boost::adjacency_list<boost::listS, boost::vecS, boost::undirectedS, boost::no_property, boost::property<edge_impl_t, Bar::Edge<Foo::source>, boost::no_property>, boost::no_property, boost::listS>, boost::vecS, boost::listS, boost::undirectedS, boost::no_property, boost::property<edge_impl_t, Bar::Edge<Foo::source>, boost::no_property>, boost::no_property, boost::listS>::config, Base = boost::undirected_graph_helper<boost::detail::adj_list_gen<boost::adjacency_list<boost::listS, boost::vecS, boost::undirectedS, boost::no_property, boost::property<edge_impl_t, Bar::Edge<Foo::source>, boost::no_property>, boost::no_property, boost::listS>, boost::vecS, boost::listS, boost::undirectedS, boost::no_property, boost::property<edge_impl_t, Bar::Edge<Foo::source>, boost::no_property>, boost::no_property, boost::listS>::config>]': /usr/local/gcc-4.1.1/boost-1.33.1/boost/graph/detail/adjacency_list.hpp:1990: instantiated from 'boost::vec_adj_list_impl<Graph, Config, Base>& boost::vec_adj_list_impl<Graph, Config, Base>::operator=(const boost::vec_adj_list_impl<Graph, Config, Base>&) [with Graph = boost::adjacency_list<boost::listS, boost::vecS, boost::undirectedS, boost::no_property, boost::property<edge_impl_t, Bar::Edge<Foo::source>, boost::no_property>, boost::no_property, boost::listS>, Config = boost::detail::adj_list_gen<boost::adjacency_list<boost::listS, boost::vecS, boost::undirectedS, boost::no_property, boost::property<edge_impl_t, Bar::Edge<Foo::source>, boost::no_property>, boost::no_property, boost::listS>, boost::vecS, boost::listS, boost::undirectedS, boost::no_property, boost::property<edge_impl_t, Bar::Edge<Foo::source>, boost::no_property>, boost::no_property, boost::listS>::config, Base = boost::undirected_graph_helper<boost::detail::adj_list_gen<boost::adjacency_list<boost::listS, boost::vecS, boost::undirectedS, boost::no_property, boost::property<edge_impl_t, Bar::Edge<Foo::source>, boost::no_property>, boost::no_property, boost::listS>, boost::vecS, boost::listS, boost::undirectedS, boost::no_property, boost::property<edge_impl_t, Bar::Edge<Foo::source>, boost::no_property>, boost::no_property, boost::listS>::config>]' /usr/local/gcc-4.1.1/boost-1.33.1/boost/graph/adjacency_list.hpp:373: instantiated from 'boost::adjacency_list<OutEdgeListS, VertexListS, DirectedS, VertexProperty, EdgeProperty, GraphProperty, EdgeListS>& boost::adjacency_list<OutEdgeListS, VertexListS, DirectedS, VertexProperty, EdgeProperty, GraphProperty, EdgeListS>::operator=(const boost::adjacency_list<OutEdgeListS, VertexListS, DirectedS, VertexProperty, EdgeProperty, GraphProperty, EdgeListS>&) [with OutEdgeListS = boost::listS, VertexListS = boost::vecS, DirectedS = boost::undirectedS, VertexProperty = boost::no_property, EdgeProperty = boost::property<edge_impl_t, Bar::Edge<Foo::source>, boost::no_property>, GraphProperty = boost::no_property, EdgeListS = boost::listS]' main.cpp:42: instantiated from here main.cpp:7: error: 'class Foo::source' is not a function, /usr/local/gcc-4.1.1/boost-1.33.1/boost/graph/adjacency_list.hpp:464: error: conflict with 'template<class Directed, class Vertex, class OutEdgeListS, class VertexListS, class DirectedS, class VertexProperty, class EdgeProperty, class GraphProperty, class EdgeListS> Vertex boost::source(const boost::detail::edge_base<Directed, Vertex>&, const boost::adjacency_list<OutEdgeListS, VertexListS, DirectedS, VertexProperty, EdgeProperty, GraphProperty, EdgeListS>&)' /usr/local/gcc-4.1.1/boost-1.33.1/boost/graph/detail/adjacency_list.hpp:2051: error: in call to 'source' I know the easiest way is to rename Foo::source but this class came from another library. Is there a chance to use this class anyway? Thanks in advance, Lars

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Re: [Boost-users] interested to know your opinion on possible feature
by Ovanes Markarian 11 Jul '06

11 Jul '06

On Tue, July 11, 2006 01:26, Sebastian Redl wrote: > Ovanes Markarian wrote: > >>In my current project is a need to implement an optional type, this type is considered to be >> lazy. >>I am wondering why C++ or Boost do not offer this possibility. >> >> > In what way does Boost.Optional fail to meet your needs? > > Sebastian Redl > > Thanks for your reply. I will take a look at this class in a more detailed manner. I saw it already, but thought it is not what I need. After some inspection I start to realize, that it is indeed what I might need. Thanks again. With Kind Regards, Ovanes Markarian

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erase and iterators
by bringiton bringiton 11 Jul '06

11 Jul '06

is this common practise for using an interator with erase? what i wish to do is interate through each item and delete the item if some condition is true. when i delete, i need to move back a step so that i dont miss an item. for (std::vector<int>::iterator it = vect.begin(); it != vect.end(); it++) { if ((*it) == 5) { // some condition vect.erase(it); it--; // step back } } or would it be best to use a reverse iterater? (or possible?) for (std::vector<int>::reverse_iterator it2 = vect.rbegin(); it2 != vect.rend(); it2++) { if ((*it) == 5) { // i'm not actually sure how to erase with a reverse iterator??? vect.erase(it2); } }

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weak_ptr, shared_ptr and dynamic libraries
by Kyle Girard 10 Jul '06

10 Jul '06

Hello, I was fooling around with the boost::shared_ptr and boost::weak_ptr library and dynamic libraries and I received a segmentation fault which I do not fully understand and I am hoping someone can shed some light on the situation. I am playing around with having objects in a dynamic library which are managed by shared_ptr's return weak_ptrs to the application My problem arises when the weak_ptrs aren't destroyed before the plugin is unloaded. I was hoping that the weak_ptr would become invalid when the shared_ptr it points to is unloaded but instead it causes a segmentation fault. I'm just starting to play around with dynamic libraries and shared_ptrs and stuff so I don't fully understand all the caveats that go with the territory so any information would be appreciated. Here's a small linux example which generates the error: main.cc == Application foo.cc/foo.hh == Dynamic Library make sure to set LD_LIBRARY_PATH to the appropriate directory main.cc ======= #include <iostream> #include <dlfcn.h> #include <boost/weak_ptr.hpp> #include "Foo.hh" using namespace std; int main() { typedef boost::weak_ptr<Foo> (*DoStuff) (void); void *hndl = dlopen("libFoo.so", RTLD_NOW); void *doStuff = dlsym(hndl, "doStuff"); // { //if I comment this in then the error goes away boost::weak_ptr<Foo> wpFoo = ((DoStuff)(doStuff))(); // } //if I comment this in then the error goes away dlclose(hndl); cerr << "Yay Finished" << endl; return 0; } Foo.hh ====== #ifndef FOO_HH #define FOO_HH #include <boost/weak_ptr.hpp> class Foo { }; extern "C" { boost::weak_ptr<Foo> doStuff(); } #endif //FOO_HH Foo.cc ====== #include "Foo.hh" #include <vector> #include <boost/shared_ptr.hpp> std::vector<boost::shared_ptr<Foo> > Foos; extern "C" { boost::weak_ptr<Foo> doStuff() { Foos.push_back(boost::shared_ptr<Foo>(new Foo)); return Foos[0]; } } Makefile ======== CC = g++ LIBS = -ldl .cc.o: $(CC) -ggdb -c $< default: make all OBJS = main.o test: main.o $(CC) -rdynamic -o test main.o $(LIBS) libfoo.so: Foo.o g++ -shared -Wl,-soname,libFoo.so -o libFoo.so Foo.o all: test libfoo.so clean: rm -f *.so *.o test === end of example thanks Kyle

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interested to know your opinion on possible feature
by Ovanes Markarian 10 Jul '06

10 Jul '06

Hello all, I have one issue, which I would like to discuss here. In my current project is a need to implement an optional type, this type is considered to be lazy. I am wondering why C++ or Boost do not offer this possibility. These are just some thoughts which are really not perfect, but an opinion and interest would be highly appreciated: template<class Type, class Allocator /*some other policies like threading etc.*/> class lazy_type { public: //constructors must be considered which //should it be possible to copy this type etc. //destuctor, must be considered how the object should be deallocated in regards of owning and non-owning policies operator bool()const { return ptr_!=NULL; } Type* operator->() { if(!ptr_) { //allocate ptr_ and instantiate it using an allocator or another policy type ... } return ptr_; } private: Type* ptr_; }; This type can be a mix of reference counted ptr (shared_ptr) and allocator on request. All comments and thoughts are HIGHLY appreciated. With Kind Regards, Ovanes Markarian

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Linking errors while using the test library (for a very basic program)
by Josh 10 Jul '06

10 Jul '06

I have a very simple program ******************************************************************** #include <iostream> #include <boost/test/unit_test.hpp> using boost::unit_test::test_suite; void MyTest() { BOOST_CHECK(2==2); } test_suite * init_unit_test_suite( int, char* [] ) { test_suite* test= BOOST_TEST_SUITE( "Simple test" ); test->add(BOOST_TEST_CASE( &MyTest ), 0); return test; } **************************************************************************************** I am trying to compile it using the following commands g++ -c BoostTest.cpp -I~/boost/include/boost-1_33_1/ g++ -o BT BoostTest.o -I/home/josh/boost/include/boost-1_33_1/ /home/josh/boost/lib/libboost_unit_test_framework-gcc-s.a The first step completes without a problem, the linking stage gives the following errors BoostTest.o(.text+0x15b): In function `MyTest()': : undefined reference to `boost::test_tools::tt_detail::test_and_continue_impl(bool, boost::basic_wrap_stringstream<char>&, boost::unit_test::basic_cstring<char const>, unsigned int, bool, boost::unit_test::log_level)' BoostTest.o(.text+0x258): In function `init_unit_test_suite(int, char**)': : undefined reference to `boost::unit_test::test_suite::add(boost::unit_test::test_case*, unsigned long, int)' BoostTest.o(.gnu.linkonce.t._ZN5boost9unit_test16create_test_caseEPFvvESs+0x12): In function `boost::unit_test::create_test_case(void (*)(), std::basic_string<char, std::char_traits<char>, std::allocator<char> >)': : undefined reference to `boost::unit_test::ut_detail::normalize_test_case_name(std::basic_string<char, std::char_traits<char>, std::allocator<char> >&)' BoostTest.o(.gnu.linkonce.t._ZN5boost9unit_test18function_test_caseC1EPFvvENS0_13basic_cstringIKcEE+0x1b): In function `boost::unit_test::function_test_case::function_test_case(void (*)(), boost::unit_test::basic_cstring<char const>)': : undefined reference to `boost::unit_test::test_case::test_case(boost::unit_test::basic_cstring<char const>, bool, unsigned long, bool)' BoostTest.o(.gnu.linkonce.r._ZTVN5boost9unit_test18function_test_caseE+0x10): undefined reference to `boost::unit_test::test_case::size() const' BoostTest.o(.gnu.linkonce.t._ZN5boost9unit_test9test_caseD2Ev+0xc): In function `boost::unit_test::test_case::~test_case()': : undefined reference to `vtable for boost::unit_test::test_case' BoostTest.o(.gnu.linkonce.r._ZTIN5boost9unit_test18function_test_caseE+0x8): undefined reference to `typeinfo for boost::unit_test::test_case' ************************************************************* PLEASE HELP! Josh --------------------------------- Want to be your own boss? Learn how on Yahoo! Small Business.

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