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

subgraphs in BGL
by Luqman Hodgkinson 17 Oct '09

17 Oct '09

In the Boost Graph Library, I run connected components. I would like to create a new graph for each connected component where each vertex in the new graphs maintains all properties from the original graph. How do I do this? Best wishes, Luqman

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[filesystem] how to set a file size?
by Eric Niebler 17 Oct '09

17 Oct '09

Forgive me for the n00b-ish (and slightly offtopic) question, but is there any way in standard C++ or in Boost.Filesystem to truncate a file to a particular size? With std::ofstream, I can either truncate a file on open to 0 size, or else open it in overwrite mode and scribble over it, but when I'm done, I don't seem to have a way of saying, "The end of the file is now *here*." Is that right? And if so, does Boost.Filesystem have an API for this? Thanks, -- Eric Niebler BoostPro Computing http://www.boostpro.com

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[SOAP / WSDL Support] Web Portal Design
by Boost lzw 17 Oct '09

17 Oct '09

Hi there, I came across this C++ web services client library: http://wsdlpull.sourceforge.net/#overview Does Boost C++ support SOAP / WSDL for designing dynamic web portals ? As I know, Boost.Asio does support HTTP server development with example codes (very good ones). However, is there a way that we can extend Boost.Asio towards using SOAP / WSDL with Apache servers or ASP.NET technologies ? A big picture view of it, even non-Boost solutions, can be very helpful for me. thanks a lot in advance, Robert

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[Serialization] Changes for implementing archives between 1.39 and 1.40
by Ioannis Papadopoulos 17 Oct '09

17 Oct '09

Hi, I'm implementing my own archive (let's say my_archive) for use in Boost.Serialization. I'm following http://www.boost.org/doc/libs/1_40_0/libs/serialization/example/demo_fast_a… My archive is implemented in a header file. However, I get undefined symbols unless I add the following to my source template class boost::archive::detail::archive_serializer_map<my_archive>; Am I missing something? Is this the correct way of doing it? I didn't have to add this prior to Boost 1.40 Thanks

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[Boost.Test] [1.38] Automated test suie registration with muti-file-test-modules
by Greg Christopher 17 Oct '09

17 Oct '09

Hi, We are starting to expand the number of test modules and are having some growing pains. Originally we were using the "single header" variant included/unit_test.hpp file. Now we have switched to linking to the dynamic version of the boost test library and are including auto_unit_test.hpp. We have been counting on the Test Tools to automatically register suites and test cases. This still worked when we just included unit_test.hpp (instead of included/unit_test.hpp). However with multiple test modules, init_unit_test_suite is being defined in each module. I am looking for clear documentation on what to do. This seems like the closest thing: http://www.boost.org/doc/libs/1_31_0/libs/test/doc/components/unit_test_fra… However following those directions exactly when trying to use multiple test modules (in a single executable) and only one BOOST_AUTO_TEST_MAIN still results in init_unit_test_suite being multiply defined. I would like multiple test suites, although the documentation for this declares that there is a single global test suite. I apologize if this is well documented somewhere, but after an hour of googling I have to ask. Greg

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[mpl] Where is at with default
by Agustín K-ballo Bergé 16 Oct '09

16 Oct '09

I can't seem to find the `at` metafunction with a default value for associative sequences. What should I include to use such metafunction with a mpl::map ? Including <boost/mpl/at.hpp> is not enough, I get a 'too many templates arguments' when trying to do: typename boost::mpl::at< State, R, L >::type which I ended up doing like this: typename boost::mpl::eval_if< typename boost::mpl::has_key< State, R >::type , boost::mpl::at< State, R > , boost::mpl::identity< L > >::type Thank you.- Agustín K-ballo Bergé.-

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[preprocessor] different macro expansion depending on whether its argument is defined or not?
by Ingolf Steinbach 16 Oct '09

16 Oct '09

Hi, is it possible to write a preprocessor macro which takes one argument and which expands differently depending on whether the argument is defined or not? Boost solution preferred. Example: #define FOO #undef BAR MY_MACRO(FOO) expands to 1 MY_MACRO(BAR) expands to 0 Kind regards Ingolf

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[type_traits] Obtain type of pointer to member.
by Germán Diago 16 Oct '09

16 Oct '09

Hello. I would like to know if it's possible to obtain the base type from this expression: struct MyStruct { string field1; }; decltype(&MyStruct::field1) is a pointer to member. I would like to obtain type string instead, removing the pointer to member. Is it possible? Thanks.

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Re: [Boost-users] AVL tree insert_equal generating assertion `node_algorithms::unique(to_insert)'
by bsing 16 Oct '09

16 Oct '09

My previous mail got truncated, the completed listing is below: Hi, I have the following piece of code that is generating the above assertion. Could someone tell me what is going wrong: template <typename T> struct my_node_t : public avl_set_base_hook<> { my_node_t(T data): m_data(data) {} template <typename U> friend bool operator< (const my_node_t<U>& lhs, const my_node_t<U>& rhs) { return lhs.m_data < rhs.m_data; }; T m_data; }; typedef my_node_t<int> avlnode_t; typedef avltree<avlnode_t> avltree_t; struct args_t { unsigned int seed[MAX_THREADS]; vector<avlnode_t>* items; avltree_t* tree_ptr; thread_args_t(size_t num_threads, avltree_t* map, vector<avlnode_t>* init_vec, size_t num_entries, unsigned int s) { num_items = num_entries; tree_ptr = map; initial_items = init_vec; for (size_t i = 0; i < num_threads; ++i) { seed[i] = i + s; } for (int i = 0; i < 10; ++i) { initial_items->push_back(i * 100); } for (vector<avlnode_t>::iterator it = initial_items->begin(); it != initial_items->end(); ++it) { tree_ptr->insert_equal(*it); } } ~thread_args_t() { tree_ptr->clear(); delete tree_ptr; delete initial_items; } }; void worker(void* args_ptr) { args_t* args = static_cast<args_t*>(args_ptr); avltree_t* tree = args->tree_ptr; vector<avlnode_t>* values = args->initial_items; int index = 5; //generate_random<int>(my_seed, 0, num_items + 1))) avlnode_t& find_element = *(values->begin() + index); tree->insert_equal(find_element); ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ <-raises exception } int main() { int num_threads = 1, num_entries = 10; vector<avlnode_t>* init_vec = new vector<avlnode_t>; avltree_t* tree = new avltree_t; args_t* args = new args_t(num_threads, tree, init_vec, num_entries); worker(args); delete args; }

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AVL tree insert_equal generating assertion `node_algorithms::unique(to_insert)'
by bsing 16 Oct '09

16 Oct '09

Hi, I have the following piece of code that is generating the above assertion. Could someone tell me what is going wrong: template <typename T> struct my_node_t : public avl_set_base_hook<> { my_node_t(T data): m_data(data) {} template <typename U> friend bool operator< (const my_node_t<U>& lhs, const my_node_t<U>& rhs) { return lhs.m_data < rhs.m_data; }; T m_data; }; typedef my_node_t<int> avlnode_t; typedef avltree<avlnode_t> avltree_t; struct args_t { unsigned int seed[MAX_THREADS]; vector<avlnode_t>* items; avltree_t* tree_ptr; thread_args_t(size_t num_threads, avltree_t* map, vector<avlnode_t>* init_vec, size_t num_entries, unsigned int s) { num_items = num_entries; tree_ptr = map; initial_items = init_vec; for (size_t i = 0; i < num_threads; ++i) { seed[i] = i + s; } for (int i = 0; i < 10; ++i) { initial_items->push_back(i * 100); } for (vector<avlnode_t>::iterator it = initial_items->begin(); it != initial_items->end(); ++it) { tree_ptr->insert_equal(*it); } } ~thread_args_t() { tree_ptr->clear(); delete tree_ptr; delete initial_items; } }; void worker(void* args_ptr) { args_t* args = static_cast<args_t*>(args_ptr); avltree_t* tree = args->tree_ptr; vector<avlnode_t>* values = args->initial_items; int index = 5; //generate_random<int>(my_seed, 0, num_items + 1))) avlnode_t& find_element = *(values->begin() + index); tree->insert_equal(find_element); ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ <-raises exception } int main() { int num_threads = 1, num_entries = 10; vector<avlnode_t>* init_vec = new vector<avlnode_t>; avltree_t* tree = new avltree_t; args_t* args = new args_t(num_threads, tree, init_vec, num_entries);

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