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multi_array math operation.
by chun ping wang 12 Apr '06

12 Apr '06

Question 1: How would i add or subtract multiarray given the fact that i don't know the dimension of it... Like its N dimension where N = 4. and u know both Multi_array A and Multi_Array B has [x][y][z][w] dimension and u want to add them together. Question 2: are there any built in operator for that...the built in + only does pointers address not adding actual object together.

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[xpressive&regex&spirit] Can previous regex be cached?
by Lynn Allan 12 Apr '06

12 Apr '06

<alert comment=<boost newbie"> Xpressive provides a "tips n tricks" to: Compiling a regex (dynamic or static) is more expensive than executing a match or search. If you have the option, prefer to compile a pattern into a basic_regex<> object once and reuse it rather than recreating it over and over. Would it be feasible/advantageous for the regex-related libraries to automagically to "cache" the immediately previous regex compilation? (or provide as an option) I've seen code that had the same regex being compiled inside a loop, which I suppose would really diminish performance. Perhaps this could be detected, and the user/developer "protected from themselves" ... and/or perhaps informed that this is happening? Could there be a "helper" class that somehow or other allowed the last "n" regexes to be cached? (btw .... what is the plural of regex .... regexen? regices?) </alert>

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undefined reference to boost::detail::graph::read_graphviz
by Irek Szczesniak 12 Apr '06

12 Apr '06

Hi, I have a problem with the Boost Graph Library: I'm unable to link with the read_graphviz function. I'm using Boost v. 1.33.1 on Fedora Core 3, Linux 2.6.10, gcc 3.4.4. I try to compile the example boost_1_33_1/libs/graph/example/graphviz.cpp. > g++ -I /usr/local/include/boost-1_33_1/ /home/ijs/boost_1_33_1/libs/graph/src/libbgl-viz.a graphviz.cpp /tmp/ccBWKH7i.o(.gnu.linkonce.t._ZN5boost13read_graphvizINS_14adjacency_listINS_4vecSES2_NS_11undirectedSENS_8propertyINS_13vertex_name_tESsNS_11no_propertyEEENS4_INS_13edge_weight_tEdS6_EES6_NS_5listSEEEEEbRSiRT_RNS_18dynamic_propertiesERKSs+0x6e): In function `bool boost::read_graphviz<boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, boost::property<boost::vertex_name_t, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::no_property>, boost::property<boost::edge_weight_t, double, boost::no_property>, boost::no_property, boost::listS> >(std::basic_istream<char, std::char_traits<char> >&, boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, boost::property<boost::vertex_name_t, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::no_property>, boost::property<boost::edge_weight_t, double, boost::no_property>, boost::no_property, boost::listS>&, boost::dynamic_properties&, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)': : undefined reference to `boost::detail::graph::read_graphviz(std::basic_istream<char, std::char_traits<char> >&, boost::detail::graph::mutate_graph&)' collect2: ld returned 1 exit status I would appreciate any advice. Thanks for reading. Best, Irek

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[xpressive] Glitch with example project re xpressive_typeof.hpp
by Lynn Allan 11 Apr '06

11 Apr '06

<alert comment="boost newbie"> Thanks for providing the example project for demonstrating usage of xpressive. As a windows developer with minimal stl / boost experience, it is a terrific aid for "getting up to speed" (and could be a model for other libraries to provide "baby steps with training wheels" sample code?). Just a glitch: The vc7.1 project file has a reference to xpressive_typeof.hpp, which refers to the non-existent file <boost/typeof/typeof.hpp> ... and it goes downhill from there. The project doesn't actually use xpressive_typeof.hpp, so the example project still compiles/links ok .... I suppose this is an obsolete reference reflecting an earlier configuration? HTH, </alert>

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Serialization: hugo file size, binary archives
by Sascha Ochsenknecht 11 Apr '06

11 Apr '06

Hello, I'm using the Serialization Library of Boost to store my data structure. I want to use the binary archive type by default: boost::archive::binary_oarchive(ostream &s) // saving boost::archive::binary_iarchive(istream &s) // loading But I noticed that these files can be very big compared to the stored data. I got a binary archive with around 1.5GByte. That could be but when I compress it I got only ~200MByte left (!). It seems that there is a lot of 'overhead' data or 'redundant' data (I see a lot of '0' when I look into it with an Hex editor). i tried the gzip (...) filter of the Iostreams library, but I want to avoid this for production due to increasing runtime. Some Information about my data structure (maybe helpful): - using a lot of pointer - using a lot of std::vector Does anybody investigate the same problem? Is there a possibility to decrease the archive size but storing the same amount of data? What could be a solution? Writing an own/optimized (regarding to my data structure) Archive class? thanks in advance Sascha

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Re: [Boost-users] Changing name of function being called in a tem plate
by James Hughes 11 Apr '06

11 Apr '06

Sorry that should read "boost.function does NOT (....." amongst other bad spelling mistakes... James > -----Original Message----- > From: James Hughes [mailto:JHughes@Linx.co.uk] > Sent: 11 April 2006 17:01 > To: 'boost-users(a)lists.boost.org' > Subject: Re: [Boost-users] Changing name of function being called in a > tem plate > > > >Have you checked out Boost.Function? You can use a > >boost::function<void (T &)> > >instance in your class to point to the correct member > function you want > >to call. > > > >Alternatively, you may try to use member function pointer: > > > >template <typename T, void (Observer::*Notify)(T & )> > >class .... > >{ } > > > >Just my 5 cents... > > > >Cheers, > > > >Freddie > > Thanks Freddie, > > boost.function does allows me (I dont think) to specify the > function when > the template is instantiated (it has to be done programmatically). The > alterantive might, but I am unsure of the syntax and how to > use it - could > you add any detail? > > At the moment, it seems like a robust option is to use > macros, and simply > redefine the function name to whatever I want - quick and > simple, but not > very templatey!! > > James > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users >

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Re: [Boost-users] Changing name of function being called in a tem plate
by James Hughes 11 Apr '06

11 Apr '06

>Have you checked out Boost.Function? You can use a >boost::function<void (T &)> >instance in your class to point to the correct member function you want >to call. > >Alternatively, you may try to use member function pointer: > >template <typename T, void (Observer::*Notify)(T & )> >class .... >{ } > >Just my 5 cents... > >Cheers, > >Freddie Thanks Freddie, boost.function does allows me (I dont think) to specify the function when the template is instantiated (it has to be done programmatically). The alterantive might, but I am unsure of the syntax and how to use it - could you add any detail? At the moment, it seems like a robust option is to use macros, and simply redefine the function name to whatever I want - quick and simple, but not very templatey!! James

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[shared_ptr] commit/rolback
by Denis G. Priyomov 11 Apr '06

11 Apr '06

Wouldn't it be nice to extend shared_ptr to support transaction-like semantics? Or is it possible already? Sometimes it's needed to execute code on exit only until we haven't reached some point (of "no return"): { shared_ptr<void> cr_guard(static_cast<void*>(0), bind(rollback_fun, x, y)); [...some critical part which should call rollback_fun on failure only...] //don't call rollback_fun if we get here cr_guard.commit(); [...any code that follows...] } Thanks! Wish you well! -=-=-=-=-=-=-=-=-=- Denis G. Priyomov

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Re: [Boost-users] Changing name of function being called in a template
by Wu Yinghui, Freddie 11 Apr '06

11 Apr '06

> From: > James Hughes <JHughes(a)Linx.co.uk> > Date: > Tue, 11 Apr 2006 10:14:12 +0100 > > Hello all, > > I have a feeling this may be off the topic of Boost, so if anyone can point > me in the direction of a better place to ask please do (a templates mailing > list?). However, I post it here because I think Boost::Bind does something > similar internally to what I want to do, so someone may be able to advise. > > I have a couple of templated class which implement a simple observer pattern > (yes I know Boost has signals, but it's not thread safe). > > It uses a virtual function to make a call in to the observer from the > subject. My own observer then derive from this class and implement the > notify function. However, I would like to 'template' the name of the > function, so that different instances of the template can make calls to > different named function. > > Now in Boost:bind you specify the name of the function in the class to be > called, but I don't know how to implement that in my own template class. > > class observer<typename T> > { > virtual void Notify(T&); // This is the function I want to rename > according to the template > } > > so I might want, in a different instance, the Notify function to be called, > Shutdown(). Following code is NOT valid C++, but gives an idea of what I am > trying to implement, but don't know enough yet to do so!! > > class observer<typename T, typename functionname> > { > virtual void <functionname>(T&) > } > > Is there a way I can use templates to do this? Boost:bind can call a > particular member function passed in as part of the template defn, how do I > that? > > I hope that is vaguely clear... > > James Have you checked out Boost.Function? You can use a boost::function<void (T &)> instance in your class to point to the correct member function you want to call. Alternatively, you may try to use member function pointer: template <typename T, void (Observer::*Notify)(T & )> class .... { } Just my 5 cents... Cheers, Freddie

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program_options, /Ob<n>
by Strelnikov Michael 11 Apr '06

11 Apr '06

Hello All, I'd like to parse cl.exe's command line with program_options. po::command_line_style::style_t op_style = po::command_line_style::style_t( po::command_line_style::allow_long | po::command_line_style::allow_long_disguise | po::command_line_style::long_allow_adjacent ); Parses only -Ob=<n> thanks

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