October 2002 - Boost-users - lists.preview.boost.org

[bgl] breadth_first_search for shortest paths (fwd)
by Joel Young 31 Oct '02

31 Oct '02

Dear Jeremy, et al, I am trying to implement a shortest paths algorithm on a directed graph. As I have unit edge weights, I would rather use breadth_first_search rather than dijkstra. // Is this a good candidate for addition? template <class Map, class Tag> struct vertex_marker : public boost::base_visitor<vertex_marker<Map,Tag> > { typedef Tag event_filter; vertex_marker(Map p_map,int p_val) : m_map(p_map),m_val(p_val) { } template <class Vertex, class Graph> void operator()(Vertex v,const Graph&) { boost::put(m_map,v,m_val); } Map m_map; int m_val; }; template <class Map, class Tag> vertex_marker<Map,Tag> mark_vertices(Map p_map, Tag, int p_v) { return vertex_marker<Map,Tag>(p_map,p_v); } boost::breadth_first_search( mygraph, rootnode, boost::visitor(boost::make_bfs_visitor( std::make_pair( boost::record_distances( boost::get(boost::vertex_distance,mygraph), boost::on_tree_edge()) , std::make_pair( mark_vertices( boost::get(boost::vertex_distance,mygraph), boost::on_initialize_vertex(), std::numeric_limits<int>::max()) , mark_vertices( boost::get(boost::vertex_distance,mygraph), boost::on_start_vertex(), 0) ) ) )) ); The problem is that on_start_vertex does not seem to be implemented for breadth_first_search, but it is for depth_first. For dijkstra, the start node seems to be automaticly zeroed. I guess I could mod Am I missing something really obvious here or is there an inconsistency across the algorithms? Shouldn't on_start_vertex be used for all of the graph algorithms? Also, I can't seem to find documentation on neighbor_bfs.hpp Thanks, Joel

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Debug regex++ in VC6
by r_gharavi 31 Oct '02

31 Oct '02

When I build a stand-alone debug xll with regex++ (static linking), Excel refuses to accept it as an addin. It works fine in release mode. Due to reasons beyond my control :-), I am using VC6 STL. Any pointers would be appreciated. Thanks.

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d_heap bug
by Tsvetomir Valtchev 31 Oct '02

31 Oct '02

[I tried to contact the library's author, dietmar.kuehl@claas- solutions.de, but the message bounced back.] Dear Dietmar, I was looking for a better heap class than the one in STL and I was delighted to come across your d_heap class included in the Boost library. Unfortunately, I had a number of problems with it, and I figured you might be interested in some feedback. First, the class didn't compile with VC.NET (and probably won't with VC 6 either). This might be due to non-conformance on the part of Microsoft's compiler and some known limitations with template support, but for some of the issues I think they were due to the non- conformance of the code itself. Second, to my dismay, the code turned out to be seriously flawed. The following simple fragment, for example, causes a crash: THeap::pointer ptrs[10]; ptrs[0] = heap.push(12); ptrs[1] = heap.push(16); heap.remove(ptrs[0]); heap.remove(ptrs[1]); After some debugging and deciphering of the code, I found that the remove() function didn't handle a special case where the node to be 'sifted up' coincided with the last "hole" left in the tree. I think pop() had a similar problem. (In my fixed version, I have expressed pop() in terms of remove(), which resolves the problem and also avoids some code duplication.) I hope some day you get around to publishing an improved version. Another suggestion I have is some way to make sure that the pointer's passed back by client code are valid. Extensive use of assertions throughout the code might also prevent various programming errors. Regards, // Chango V.

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Regex++ and UTF-8
by Gitit 31 Oct '02

31 Oct '02

Hi, We want to use regex++ (version 3.31) with UTF-8 strings. I tried to match a UTF-8 character of 2 bytes to the regex "." and the match failed. It seems regex++ handles these 2 bytes as two separate characters. 1) Is there a "native" way in the regex++ library for using UTF-8 strings? Can we use UTF-8 strings to compare against a compiled regex (the regex is in ASCII only)? Can the regex itself hold UTF-8 characters? 2) Is converting to wchar_t our only option? As far as I understand, wchar_t does not cover the entire range of characters covered by UTF-8, so it may not be enough. Any other ideas? thanks, Gitit.

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Re: [Boost-Users] Re: regex: flag for "global" search?
by dick.bridges＠tais.com 30 Oct '02

30 Oct '02

The boost::regex_search example bumps the start to march through the sub-expressions and the boost::regex_grep examples demonstrate using the 'callback' for each term. I was kinda hoping the library provided a "convenience version" that would take something like "(\\w+)(?:\\.(\\w+))*" and populate the match_results as if the terms had been expanded <e.g.> "(\\w+)(?:\\.(\\w+))?(?:\\. (\\w+))?(?:\\.(\\w+))?"</e.g.> Perhaps to some arbitrary limit? Oh well, given the riches provided, a little while loop now and then is surely a small price to pay. ;) Thanks for the response. I'm continually amazed at the ethos fostered by Boost group members. "Edward Diener" <eddielee@tropic To: boost-users(a)yahoogroups.com soft.com> cc: Sent by: news Subject: [Boost-Users] Re: regex: flag for "global" search? <news(a)main.gmane .org> 10/29/2002 04:54 PM Please respond to Boost-Users Use boost::regex_grep. The boost::regex_search only finds the first match. <dick.bridges(a)tais.com> wrote in message news:OF6181960C.1A0F5C63-ON88256C61.006996C6@tais.net... > I'm trying to capture the sub-expressions in a fqdn (e.g., > one.two.three.com.). One piece of Perl-speak for the expression is: "/ > (\w+)\./g". I've been using boost_search and trying variations on "(?: > (\\w+)\\.)+" but I can't seem to get all the sub-expressions into the > match_results. > > There's got to be a flag I've been overlooking. Any suggestion will be > appreciated. Info: <http://www.boost.org> Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

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regex: flag for "global" search?
by dick.bridges＠tais.com 30 Oct '02

30 Oct '02

I'm trying to capture the sub-expressions in a fqdn (e.g., one.two.three.com.). One piece of Perl-speak for the expression is: "/ (\w+)\./g". I've been using boost_search and trying variations on "(?: (\\w+)\\.)+" but I can't seem to get all the sub-expressions into the match_results. There's got to be a flag I've been overlooking. Any suggestion will be appreciated. TIA

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Gcc-3.2, statistic_tests.cpp and <limits>
by pcarlini.rm 29 Oct '02

29 Oct '02

Hi, the PR libstdc++/6718 in the Gcc bug database is about a run time problem with this Boost testcase: paolo:~/Programming/c++/boost_1_29_0/libs/random> a.out Confidence level: 0.99; 1-alpha = 0.01; chi_square(19, 36.191) = 0.99 Running tests on minstd_rand KS: 4750* [0] 9500* [0] equidistribution: a.out: statistic_tests.hpp:571: void generic_counter<RandomA ccessContainer>::operator()(int) [with RandomAccessContainer = std::vector<int, std::allocator<int> >] : Assertion `static_cast<unsigned int>(i) < container.size()' failed. Abort According to Nathan Sidwell and Gaby Dos Reis analysis the problem is due to well known issues with numeric_limits<double>::infinity of 3.2's run time library for which unexpectedly Boost provides no work arounds. On the contrary, 2.95.x worked just fine. Please let me know if you need any additional information, ciao, Paolo.

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AW: [Boost-Users] boost::bind problem
by Jasper, Alexander 29 Oct '02

29 Oct '02

-----Ursprüngliche Nachricht----- Von: Mark Snelling [mailto:mark@bakedbeans.com] Gesendet: Dienstag, 29. Oktober 2002 17:44 An: Boost-Users(a)yahoogroups.com Betreff: [Boost-Users] boost::bind problem [...] typedef priority_queue<shared_ptr<Functor>, vector<shared_ptr<Functor> >, bind(less<int(), bind(&Functor::priority, _1), bind(&Functor::priority, _2))> MyQueue; As far as I know you can't call a function in a typedef. bind(..) is a function call returning a predicate. But does s.o. know how to use bind in this manner. I failed to, since the type of what bind returns is far to complex. And it is required if you want to to use bind in conjunction with maps or the priority_queue's. You have to wrap the call in your own predicate. alex

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boost::bind problem
by Mark Snelling 29 Oct '02

29 Oct '02

Hello, I was wondering if anyone out there in Boost land could give me a hand here? Here's the problem: I have a class A: class A { public: A(int i) : _priority(i) {} int priority() {return _priority;} private: int _priority; }; What I want to do is create a std::priority_queue based on boost::shared_ptr<A> and use boost::bind/compose to create the sorting function required by std::priority_queue. However, when I try and typedef the queue (to save a lot of typing) I get compiler errors on VS.NET. using namespace std; using namespace boost; typedef priority_queue<shared_ptr<Functor>, vector<shared_ptr<Functor> >, bind(less<int(), bind(&Functor::priority, _1), bind(&Functor::priority, _2))> MyQueue; Am I going about this the right way? Any help appreciated. TIA Mark.

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Graph library: parallel edges
by Juerg Tschirren 29 Oct '02

29 Oct '02

With the Boost Graph Library, I try do create an undirected graph that does not allow parallel edges, so far without success. Does anybody have a small example that shows how to do this? Juerg

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