April 2004 - Boost - lists.boost.org

boost::filesystem with network paths on windows
by Arne.Adams＠t-online.de 25 Aug '04

25 Aug '04

Hi, I am trying to use boost filesystem to copy files from a local directory to a directory on a network server (the latter having a path like \\databaseserver\c$\importfiles\myTabledump.txt <file:///\\databaseserver\c$\importfiles\myTabledump.txt> ) Unfortunately the leading double backslashs (\\) get converted in the constructor of filesystem::path to double slashs - yielding a different meaning. Is there a way to copy files on windows to network servers like this? Regards, Arne Adams Nerotal 23 65193 Wiesbaden Tel.: (+49) 611 3413745 Mobil: 0172 6147473 Mail: inbox(a)arneadams.com

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[filesystem + iterator] directory iterator problem
by Vladimir Prus 08 Jul '04

08 Jul '04

There's a bug report on sourceforge: https://sourceforge.net/tracker/index.php?func=detail&aid=937606&group_id=7… which boils down to the fact that directory_iterator it(...); path p = *it++; does not work correctly. The exact problem is that the above line return a copy of the iterator, and increments 'it', but both iterators have shared_ptr to the same internal structure, so by time user deferences the copy, it gets the next file in the directory. The filesystem lib sources contain the following comment: The *r++ requirement doesn't appear to apply to the new single_pass_traversal category Thus I'm leaving the proxy out pending confirmation from the N1477 authors I'm not sure I understand that. It seems that *r++ should work, since signle pass iterator requires that r++ should work and return object of type X (call it r2), and the reabable iterator requires that *r2 should work. Am I wrong? And BTW, don't the above requirements mean r++ cannot return a proxy object, but only a real copy of the iterator? - Volodya

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[BGL] remove_edge bug
by Vladimir Prus 30 Jun '04

30 Jun '04

Jeremy, I think your reversion 1.120 of detail/adjacency_list.hpp: 2004-04-01 05:30 jsiek * detail/adjacency_list.hpp: fixed remove_edge for bidirectional graphs actually breaks remove_edge in a different way. Please take a look at http://zigzag.cs.msu.su:7813/program_graph.cpp The code there add two vertices, an edge between them, and then removes the edge. After that 'num_edges' returns 1, not 0 as expected. I seems like now remove_edge removes elements from out_edges and in_edges storage, but not from global edges vector. Is it possible to fix this problem? TIA, Volodya

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[BGL] Unused parameter "inf" in dijkstra_shortest_paths?
by Douglas Gregor 30 Jun '04

30 Jun '04

Hmmm, this could be a bug, but I don't have time to look into it now: /home/gregod/Projects/Boost/boost/boost/graph/dijkstra_shortest_paths.hpp: In function `void boost::dijkstra_shortest_paths_no_init(const VertexListGraph&, typename boost::graph_traits<G>::vertex_descriptor, PredecessorMap, DistanceMap, WeightMap, IndexMap, Compare, Combine, DistInf, DistZero, DijkstraVisitor) [with VertexListGraph = boost::adjacency_list<boost::listS, boost::vecS, boost::bidirectionalS, boost::property<boost::vertex_name_t, std::string, boost::no_property>, boost::property<boost::edge_name_t, std::string, boost::property<boost::edge_length_t, double, boost::property<boost::edge_speed_limit_t, int, boost::property<boost::edge_direction_t, char, boost::property<boost::edge_snow_route_t, bool, boost::no_property> > > > >, boost::no_property, boost::listS>, DijkstraVisitor = boost::dijkstra_visitor<boost::null_visitor>, PredecessorMap = boost::iterator_property_map<__gnu_cxx::__normal_iterator<Intersection*, std::vector<Intersection, std::allocator<Intersection> > >, boost::vec_adj_list_vertex_id_map<boost::property<boost::vertex_name_t, std::string, boost::no_property>, size_t>, Intersection, Intersection&>, DistanceMap = boost::iterator_property_map<__gnu_cxx::__normal_iterator<double*, std::vector<double, std::allocator<double> > >, boost::vec_adj_list_vertex_id_map<boost::property<boost::vertex_name_t, std::string, boost::no_property>, size_t>, double, double&>, WeightMap = boost::adj_list_edge_property_map<boost::bidirectional_tag, double, double&, size_t, boost::property<boost::edge_name_t, std::string, boost::property<boost::edge_length_t, double, boost::property<boost::edge_speed_limit_t, int, boost::property<boost::edge_direction_t, char, boost::property<boost::edge_snow_route_t, bool, boost::no_property> > > > >, boost::edge_length_t>, IndexMap = boost::vec_adj_list_vertex_id_map<boost::property<boost::vertex_name_t, std::string, boost::no_property>, size_t>, Compare = std::less<double>, Combine = boost::closed_plus<double>, DistInf = double, DistZero = double]': /home/gregod/Projects/Boost/boost/boost/graph/dijkstra_shortest_paths.hpp:171: warning: unused parameter `double inf' /home/gregod/Projects/Boost/boost/boost/graph/dijkstra_shortest_paths.hpp: In function `void boost::dijkstra_shortest_paths_no_init(const VertexListGraph&, typename boost::graph_traits<G>::vertex_descriptor, PredecessorMap, DistanceMap, WeightMap, IndexMap, Compare, Combine, DistInf, DistZero, DijkstraVisitor) [with VertexListGraph = boost::adjacency_list<boost::listS, boost::vecS, boost::bidirectionalS, boost::property<boost::vertex_name_t, std::string, boost::no_property>, boost::property<boost::edge_name_t, std::string, boost::property<boost::edge_length_t, double, boost::property<boost::edge_speed_limit_t, int, boost::property<boost::edge_direction_t, char, boost::property<boost::edge_snow_route_t, bool, boost::no_property> > > > >, boost::no_property, boost::listS>, DijkstraVisitor = boost::dijkstra_visitor<boost::null_visitor>, PredecessorMap = boost::iterator_property_map<__gnu_cxx::__normal_iterator<Intersection*, std::vector<Intersection, std::allocator<Intersection> > >, boost::vec_adj_list_vertex_id_map<boost::property<boost::vertex_name_t, std::string, boost::no_property>, size_t>, Intersection, Intersection&>, DistanceMap = boost::iterator_property_map<__gnu_cxx::__normal_iterator<double*, std::vector<double, std::allocator<double> > >, boost::vec_adj_list_vertex_id_map<boost::property<boost::vertex_name_t, std::string, boost::no_property>, size_t>, double, double&>, WeightMap = TravelTimePropertyMap, IndexMap = boost::vec_adj_list_vertex_id_map<boost::property<boost::vertex_name_t, std::string, boost::no_property>, size_t>, Compare = std::less<double>, Combine = boost::closed_plus<double>, DistInf = double, DistZero = double]': /home/gregod/Projects/Boost/boost/boost/graph/dijkstra_shortest_paths.hpp:171: warning: unused parameter `double inf' Doug

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[iterator + lambda] transform_iterator and lambda expression
by Vladimir Prus 04 Jun '04

04 Jun '04

I'm again trying to use FP in C++, and having problems. What I wanted to do was: for_each(predecesor(v, g), /* BLL expression */ ); where predecessor(..) returns a pair of 'transform_iterator' instances. The simplest example which illustrates the problem is: struct functor { typedef int result_type; int operator()(int i) const { return i+1; }; }; transform_iterator<functor, vector<int>::iterator> it(v.begin()); (cout << _1)(*it); This does not compile, because operator* of transform_iterator return rvalue which can't be bound to non-const reference that operator() of the lambda expression accepts. Of all workarounds suggsted on BLL docs, only break_const is applicable to my case (I want to pass non-const references to the lambda, so const_parameters won't do), and break_const is scary. It looks like a serious problem with using FP, so I wonder what can be done. Maybe, transform_iterator should have yet another template parameter telling if it should store a value internally, and return reference (i.e. lvalue) in that case? It need not be enabled by default, but functions like my 'predecessor' above would make use of that extra template parameter. - Volodya

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Filesystem iterator suggestion
by Martin 18 May '04

18 May '04

I have used the filesystem library for some time now and noticed that there is no portable way of iterating over files in a directory that matches a pattern. In my applications I often need to find all files in a directory that matches "*.txt" or "input.*". I think it would be a good idea to add another constructor to the directory_iterator that support some primitive wilcards. The support could be limited to "*" at the end or followed by a "." (e.g. "*", "a*.*", "*.txt", "a.*") for (path::directory_iterator itr = directory_iterator(path, "*.txt"); itr != directory_iterator(); ++itr) ... I assume this limited wildcard support could easily be ported to most operating systems. ------------------- Another small improvement that would make the directory_iterator easier to use is to somehow allow it to only list directories or files. In the current implementation you need to create a temporary to use an algorithm on all files in a directory (or use some lambda if construct). std::vector<path> tmp; std::remove_copy_if(directory_iterator(dir), directory_iterator(), back_inserter(tmp), std::ptr_fun(is_directory)) std::for_each(tmp.begin(), tmp.end(), func); instead of just std::for_each(directory_iterator(dir, files_only), directory_iterator(), func);

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patch: boost/math/special_functions => compile error in asinh.hpp, acosh.hpp and atanh.hpp
by Huber, Carsten 10 May '04

10 May '04

Hello boost developers, this is my first mail to boost(a)lists.boost.org and it is already a bug that I found in the latest release 1.31.0 :-( I tried to compile boost::math::asinh, boost::math::acosh and boost::math::atanh recently and got a compile error "C2039 'abs' : is not a member of '_STL'" on my MSVC6 compiler. I have STLPort 4.5.3 installed and thought, this might be the problem, but then I found out that boost::math::sinc_pi and boost::math::sinhc_pi compile with no errors. To make it short: asinh, acosh and atanh are using ::std::abs, ::std::sqrt and ::std::log - which are not part of the STL. To fix this problem, I have created a patch - see attached files. Best regards, Carsten Huber ------------------------------------------------- Dipl.-Ing. Carsten Huber (Member of the VDE) Software Development Engineer Product Line Diagnostics (PDG) Vector Informatik GmbH Ingersheimer Str. 24 D-70499 Stuttgart Phone : +49 711 80670-0 Fax : +49 711 80670-299 Mailto : carsten.huber(a)vector-informatik.de Internet: http://www.vector-informatik.de -------------------------------------------------

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[Formal review] Collection Traits library
by hartmutkaiser＠t-online.de 08 May '04

08 May '04

Hi all, The review of the Collection Traits library, written by Thorsten Ottosen starts today (April 28th, 2004) and runs for 10 days (until May 7th, 2004). The Latest version of the library is available at (yahoo files sections): http://tinyurl.com/ysbaj (72 kB) or in the Boost sandbox. What is it? The Collection Traits library is mainly a tool for writing generic algorithms that work on External Collections. A Collection is a subset of the container requirements; it is so small and essential that it can be made to work with standard containers, iterator-views, built-in arrays and strings by defining a new requirement, the External Collection Concept, where typedefs and functions have been made free-standing instead of members. The library consists of two components: (1) type generators and (2) free-standing functions. The type-generators provide types such as iterators and size_type of external collections whereas the Free-standing functions are for extracting iterators and size of the external collections. Here is a small example: // Example: extracting bounds in generic algorithms template< typename ExternalCollection, typename T > inline typename boost::iterator_of<ExternalCollection>::type find( ExternalCollection& c, const T& value ) { return std::find( boost::begin( c ), boost::end( c ), value´); } template< typename ExternalCollection, typename T > inline typename boost::const_iterator_of<ExternalCollection>::type find( const ExternalCollection& c, const T& value ) { return std::find( boost::begin( c ), boost::end( c ), value´); } // replace first value and return its index template< typename EC, typename T > inline typename boost::size_type_of< EC >::type my_generic_replace( EC& c, const T& value, const T& replacement ) { boost::iterator_of<EC>::type found = find( c, v ); *found = replacement; return std::distance( boost::begin( c ), found ); } // usage std::vector<int> my_vector; typedef vector<int>::iterator iterator; std::pair<iterator,iterator> my_view( my_vector.begin(), my_vector.begin() + N ); char str[] = "a string"; // ... std::cout << my_generic_replace( my_vector, 4, 2 ) << my_generic_replace( my_view, 4, 2 ) << my_generic_replace( str, 'a', 'b' ); As the External Concepts idea is a rather new one, I would like to ask you to comment on this. Please always state in your review, whether you think the library should be accepted as a Boost library! Additionally please consider giving feedback on the following general topics: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? Regards Hartmut Review Manager

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signals and threads
by David Abrahams 06 May '04

06 May '04

So, we're thinking of using the signals library in one of our projects, but the lack of thread-safety is a concern for us. What issues are preventing Boost.Signals from being made threadsafe? -- Dave Abrahams Boost Consulting http://www.boost-consulting.com

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[multi_index] ANN: Post-review version available
by Joaquín Mª López Muñoz 05 May '04

05 May '04

I'm glad to announce that the post-review version of The Boost Multi-index Containers Library or Boos.MultiIndex (formerly known as Boost.IndexedSet) is available at: http://groups.yahoo.com/group/boost/files/multi_index.zip The most noticeable change is the new name for the library, which I hope will please most and bug none. Also, a new powerful feature called composite_key has been added. The complete list of changes after requests from the reviewers can be consulted at: http://groups.yahoo.com/group/boost/files/multi_index_postreview_notes.html I'd be grateful if the people interested could do the following: 1. make sure that all requests have been met. Those that haven't are justified at the post-review notes. 2. try to compile the library with different compilers. I don't think I've broken anything, but one never knows. This version has been tested with MSVC 6.5, GCC 3.3.1 and ICC 7.1 for Windows. Of special interest are MSVC 7.1, ICC 8.0, GCC 4.0 and CW 9.2. If no one raises any objection, in a week's time I'll commit the library to the main CVS, hopefully in time for Boost 1.32. Thanks everybody, Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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