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[Boost.Graph] Accessing edge properties via an edge_iterator
by Julius Ziegler 18 Dec '08

18 Dec '08

Hello list, I wonder what is the fastest method to access edge properties of an adjacency_list when iterating over edges. Actually, the only way I know of for accessing properties is via operator[]: typedef boost::adjacency_list<listS, vecS, boost::directedS, NodeProperty, EdgeProperty > Graph; Graph g; for( tie( ei, ei_end ) = edges( graph ); ei != ei_end; ++ei ) { g[*ei]=something; } From this I conclude, that the right EdgeProperty is stored in some associative container, with edge_descriptor being the key-type. Or does edge_iterator store any information besides a pair<vertex_descriptor, vertex_descriptor>? What is the time complexity of this look_up? To me it feels that there should be a faster way to access properties via an edge_iterator, and by browsing the source I found that edge_iterator has a member function get_property(), however, since it returns void*, and I did not find anything in the documentation, I'm not sure if it is there for this purpose. Thank you very kindly for any hints, Julius

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[bind] Need Help - Function Composition
by loadcom 18 Dec '08

18 Dec '08

Hello all, I'm using boost::bind to get elegant code. Thank the author for the great lib. I'm posting because I ran accross a small problem with the following code. My intention of the code is to find the element of a container with the least abs value of a member (i_). template <typename Arg, typename Result> class less_by_func : public std::binary_function<Arg, Arg, bool> { typedef boost::function<Result(Arg)> fn_t; typedef less_by_func<Arg, Result> self_t; fn_t func_; less_by_func() {} // not open public: less_by_func(const self_t& src) : func_(src.func_) {} explicit less_by_func(const fn_t& func) : func_(func) {} template <typename Arg, typename Result> explicit less_by_func(const less_by_func<Arg, Result>& src) : func_(src.func_) {} bool operator()(const Arg& lhs, const Arg& rhs) const { return func_(lhs) < func_(rhs); } }; // helper function template<typename F> less_by_func<typename F::argument_type, typename F::result_type> make_less_by_func(F func) { return less_by_func<typename F::argument_type, typename F::result_type>(func); } struct A { int i_; A() : i_(0) {} explicit A(int i) : i_(i) {} void set(int i) { i_ = i; } int get() const { return i_; } }; std::vector<A> a_list; a_list.push_back(A(10)); a_list.push_back(A(222)); a_list.push_back(A(-100)); int min_abs = std::min_element(a_list.begin(), a_list.end(), min2max::make_less_by_func( boost::function<int(A)>( boost::bind<int>( std::ptr_fun(&std::abs<int>), boost::bind(&A::i_, _1) ) ) ) )->i_; std::cout << min_abs << std::endl; This code works fine, what I don't understand is why I couldn't remove the explicit construction of a boost::function<int(A)> object and let compiler do the implicit conversion(construction) silently. That means the following code doesn't work: int min_abs = std::min_element(a_list.begin(), a_list.end(), min2max::make_less_by_func( boost::bind<int>( std::ptr_fun(&std::abs<int>), boost::bind(&A::i_, _1) ) ) )->i_; The following code doesn't get compile neither: std::stable_sort(a_list.begin(), a_list.end(), make_less_by_func(boost::bind(&A::i_, _1))); I know a more verbose version like this will also work: int min_abs = std::min_element(a_list.begin(), a_list.end(), boost::bind(std::less(), boost::bind(std::ptr_fun(&std::abs), boost::bind(&A::i_, _1)), boost::bind(std::ptr_fun(&std::abs), boost::bind(&A::i_, _2)) ) )->i_; But I just want the code to be as elegant as possible. :-) My environment is: boost_1_36_0 + VS2003sp1 Thanks for any hints. with best regards Max ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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[process] How to exec multiple shell commands
by Konstantin Litvinenko 18 Dec '08

18 Dec '08

Hi! I have successfully used boost.process but now stuck with a problem. I need to execute 2 commands in one shell invocation. Both windows and linux allow do that, but I can't figure out how to do it with help of boost.process. Is there interface to do that? PS. I am using old boost.process. I have download process-is-0.4.zip from the vault and didn't find solution for my problem.

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Boost::thread and Dr. Watson
by Francesco Nesci 18 Dec '08

18 Dec '08

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Thread scope
by Birju Prajapati 18 Dec '08

18 Dec '08

Hi, I've seen that when a newly created thread goes out of scope, it keeps running - this suggests to me that they are heap allocated, but can't find anywhere in the documentation that confirms this. Can someone confirm or deny this, and show me where in the docs it is if confirmed? Many thanks, Birju Schneider Trading 4th Floor, 25 Copthall Avenue London EC2R 7BP -------------------------------------------------------- Message from: Birju.Prajapati(a)schneidertrading.com Message to: boost-users(a)lists.boost.org Attached files: 0 This e-mail and any files transmitted with it are confidential, may be legally privileged, and are for the sole use of the intended recipient. Copyright in this e-mail and any accompanying document created by us is owned by us. If you are not the intended recipient of this e-mail or any part of it please telephone our IT Department at the number shown above or by e-mail at info(a)schneidertrading.com. You should not use or disclose to any other person the contents of this e-mail or its attachments (if any), nor take copies. This e-mail is not a representation or warranty and is not intended nor should it be taken to create any legal relations, contractual or otherwise. Schneider Trading Associates Ltd (Registration No. 3692131) is incorporated in England and Wales and the registered office is at 25 Copthall Avenue, London EC2R 7BP. The company is authorised and regulated by the Financial Services Authority

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[boost.tuple] Nested tuples and tie
by Julius Ziegler 18 Dec '08

18 Dec '08

Dear list, is there a way to make constructs like this one work? double a, b, c; tie( tie( a, b ), c ) = make_tuple( make_tuple( 1., 2. ), 3. ); This leads to the first parameter of the "outer" tie getting initialised by the return value of the "inner" tie. That means a temporary gets passed by reference, and the compiler (sort of reasonably) doesnt want to do this. Best regards, Julius

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[bind] Pointer as third parameter
by Jean-Pierre Bergamin 18 Dec '08

18 Dec '08

Dear boost-Users I'm having problems with calling a function that takes a pointer as the third argument through bind. I cannot explain, why the code below does not compile with the function 'op3' enabled. When changing f3 to void f3(int a, int b, int c) { } it also works. I don't see any reasony why this should fail, since f2 also works. Any ideas how to solve this? // --------------------------------------- void f3(int a, int b, int *c) { } void f2(int a, int *b) { } template <typename F> void op3(F f) { int a = 1, b = 2, c = 3; f(a, b, &c); } template <typename F> void op2(F f) { int a = 1, b = 2; f(a, &b); } void call() { op2(boost::bind(&f2, _1, _2)); //op3(boost::bind(&f3, _1, _2, _3)); } // --------------------------------------- This compiles fine. When uncommenting the line op3(...) in the function "call", gcc fails with: test.cpp: In function `void op3(F) [with F = boost::_bi::bind_t<void, void (*)(int, int, int*), boost::_bi::list3<boost::arg<1> (*)(), boost::arg<2> (*)(), boost::arg<3> (*)()> >]': test.cpp:23: instantiated from here test.cpp:11: error: no match for call to `(boost::_bi::bind_t<void, void (*)(int, int, int*), boost::_bi::list3<boost::arg<1> (*)(), boost::arg<2> (*)(), boost::arg<3> (*)()> >) (int&, int&, int*)' /usr/local/include/boost/bind/bind_template.hpp:18: note: candidates are: typename boost::_bi::result_traits<R, F>::type boost::_bi::bind_t<R, F, L>::operator()() [with R = void, F = void (*)(int, int, int*), L = boost::_bi::list3<boost::arg<1> (*)(), boost::arg<2> (*)(), boost::arg<3> (*)()>] /usr/local/include/boost/bind/bind_template.hpp:24: note: typename boost::_bi::result_traits<R, F>::type boost::_bi::bind_t<R, F, L>::operator()() const [with R = void, F = void (*)(int, int, int*), L = boost::_bi::list3<boost::arg<1> (*)(), boost::arg<2> (*)(), boost::arg<3> (*)()>] /usr/local/include/boost/bind/bind_template.hpp:114: note: typename boost::_bi::result_traits<R, F>::type boost::_bi::bind_t<R, F, L>::operator()(A1&, A2&, A3&) [with A1 = int, A2 = int, A3 = int*, R = void, F = void (*)(int, int, int*), L = boost::_bi::list3<boost::arg<1> (*)(), boost::arg<2> (*)(), boost::arg<3> (*)()>] /usr/local/include/boost/bind/bind_template.hpp:120: note: typename boost::_bi::result_traits<R, F>::type boost::_bi::bind_t<R, F, L>::operator()(A1&, A2&, A3&) const [with A1 = int, A2 = int, A3 = int*, R = void, F = void (*)(int, int, int*), L = boost::_bi::list3<boost::arg<1> (*)(), boost::arg<2> (*)(), boost::arg<3> (*)()>] MSVC 8 fails with: .\test.cpp(19) : error C2664: 'void boost::_bi::bind_t<R,F,L>::operator ()<int,int,int*__w64 >(A1 &,A2 &,A3 &) const' : cannot convert parameter 3 from 'int *__w64 ' to 'int *__w64 &' with [ R=void, F=void (__cdecl *)(int,int,int *), L=boost::_bi::list3<boost::arg<1>,boost::arg<2>,boost::arg<3>>, A1=int, A2=int, A3=int *__w64 ] .\Sleep.cpp(29) : see reference to function template instantiation 'void op3<boost::_bi::bind_t<R,F,L>>(boost::_bi::bind_t<R,F,L>)' being compiled with [ R=void, F=void (__cdecl *)(int,int,int *), L=boost::_bi::list3<boost::arg<1>,boost::arg<2>,boost::arg<3>> ] Thanks for your help. James

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[?] Looking for something like 'data_grid'
by loadcom 18 Dec '08

18 Dec '08

hello all, Sorry for this probable OT post, but I believe the boost guys must be able to help me. :-) I'm looking for a class similar to this: template class data_grid { //... }; It's a data block of arbitrary dimensions. With it user can do thing's like data look up, and interpolate on any series of specified dimentions, and the like. I guess boost doesn't have an out-of-the-box class like this, while multi_array is close to this requirements. Yes, I could write one by myself. But if there's an existing one, I won't bother to reinvent a wheel. Thanks for any information. with best regards Max ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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something about UTF8
by wind world 18 Dec '08

18 Dec '08

hi guys, I want to use boost::regex in Windows XP to match Japanese kanji. The encoding of kanji is UTF-8 I want to make sure after I use the funcation: MultibyteToWideChar to change the UTF-8 Kanji string->wstring, I can directly use boost::wregex(from wstring) to match Japanese? Appreciate any help. Worldwind

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[program options] Constraints, missing options
by Georg Sauthoff 18 Dec '08

18 Dec '08

Hi, I am using boost.Program_options and it is quite useful. I miss two features, though. I could not find a way to specify that some option should be mandatory at the command line. Or that some option has to be present at least x times and at most y times at the command line. I mean I can check it myself if the Program_options parser is finished - but I like it better, if the library would do the work for me. In pseudocode I want to write something like this for example: opts.add_options()("file,f", value< vector<string> >() ->min_times(1)->max_times(2), "blah blah"); ./a.out -f foo -f bar # ok ./a.out -f foo -f bar -f bas # exception from the Program_options parser Is this feature missing, or have I overlooked it in the documentation? Another thing I couldn't find: a way to switch program options into a 'checking mode'; i.e. a mode, where the program options code throws an exception if the count of an non existing option is queried (in case of an programming error). For example desc.add_options() ("help,h", "produce help message"); ... vm.set_pedantic(); // <- pseudo code vm.count("foobar"); // <- would throw exception Or even better, if it is possible do register some enum value, which can be used to index into the variables_map - I mean, to get a compile error the option identifier is misspelled (instead of an runtime error ...): enum my_opts { HELP }; desc.addoptions()("help,h", HELP, "produce help message"); vm.count(EHLP); // <- compile error ... Best regards Georg

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