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thread safe dynamic array and matrix
by Lars Schouw 10 Apr '06

10 Apr '06

Does boost provide me with a thread-safe dynamic array and/or matrix? The container should be thread safe for write from many thread at the same time for chaning information in the elements stored in the array. Regards Lars Schouw --------------------------------- Talk is cheap. Use Yahoo! Messenger to make PC-to-Phone calls. Great rates starting at 1¢/min.

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Program Options: What to do with positional_options_description?
by Olaf van der Spek 09 Apr '06

09 Apr '06

Hi, The example says: positional_options_description pd; pd.add("output-file", 2).add_optional("input-file", -1); But what do I do with pd after this?

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boost::bind and std::copy for member functions
by Leon Mergen 09 Apr '06

09 Apr '06

Hello, Ok, this is what I'm trying to do: I want to define some base class A which has a container with elements it needs to sort. I want to be flexible with the comparison function, so the base class A will define an abstract comparison function which will be implemented by derived classes. Since std::sort () expects function objects, after a lot of asking around I found out I needed to use boost::bind. However, trying almost all different types of combinations and looking up all kind of manuals, I'm pretty much clueless... Here's the test-case code: --- #include <algorithm> #include <string> #include <vector> #include <boost/bind.hpp> class A { public: virtual bool sort (std::string const * const & a, std::string const * const & b) const = 0; void func () { // std::sort ( _elements.begin(), _elements.end(), boost::mem_fn ( A::sort) ); std::sort ( _elements.begin(), _elements.end(), boost::bind ( A::sort, this, _1, _2 ) ); } private: std::vector < std::string * > _elements; }; class B : public A { public: virtual bool sort (std::string const * const & a, std::string const * const & b) const { return true; } }; class C : public A { public: virtual bool sort (std::string const * const & a, std::string const * const & b) const { return false; } }; --- I hope the code makes it a bit more clear as to what I'm trying to do... I follow examples listed at threads like http://blog.gmane.org/gmane.comp.lib.boost.user/day=20050617 , and well, this is almost a literate copy of some recommendations but it doesn't work: -- sort.cpp: In member function ‘void A::func()’: sort.cpp:13: error: no matching function for call to ‘bind(<unknown type>, A* const, boost::arg<1>&, boost::arg<2>&)’ /usr/local/include/boost/bind.hpp:1416: note: candidates are: boost::_bi::bind_t<boost::_bi::unspecified, F, typename boost::_bi::list_av_3<A1, A2, A3>::type> boost::bind(F, A1, A2, A3) [with F = bool (A::*)(const std::string* const&, const std::string* const&)const, A1 = A*, A2 = boost::arg<1>, A3 = boost::arg<2>] /usr/local/include/boost/bind/bind_mf_cc.hpp:78: note: boost::_bi::bind_t<R, boost::_mfi::cmf2<R, T, A1, A2>, typename boost::_bi::list_av_3<A1, A2, A3>::type> boost::bind(R (T::*)(B1, B2)const, A1, A2, A3) [with R = bool, T = A, B1 = const std::string* const&, B2 = const std::string* const&, A1 = A*, A2 = boost::arg<1>, A3 = boost::arg<2>] -- and well, the error is cryptic enough for me to not quite understand what I'm doing wrong... any suggestions ? Thanks in advance! Regards, Leon Mergen

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[string] Are std::string's null terminated?
by Lynn Allan 08 Apr '06

08 Apr '06

Sorry if this is off-topic. Just wanted to check .... are std::string's defined to be null terminated? I came across a web page that indicated they are, but you can find lots of misinformation on the web. http://www.codeproject.com/string/cppstringguide2.asp std::string's seem to be null terminated with the Microsoft vc7.1 and vc8 compiler, but I wanted to check if this is generally true according to the C++ standard. I'm relatively new to stl and using std::string .... mostly have used C strings and MFC CStrings (which changed from vc6 to vc7.1?) std::string strA = "ABC"; std::string strB = "DEF"; std::string strC = "GHI"; std::string strD = "JKL"; std::string strE = "MNO"; // Check if std::string's are null terminated const char* pTest = strC.c_str(); for (int i = 0; i < 80; ++i) { printf("I: %2d ch:%3d %c\n", i, pTest[i], pTest[i]); } std::string testStrings[] = { "abc", "def", "ghi", "jkl" }; const char* p = testStrings[1].c_str(); printf("\n********************\n"); for (int i = 0; i < 80; ++i) { printf("I: %2d ch:%3d %c\n", i, p[i], p[i]); } printf("\n********************\n"); TIA,

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total noob help: LAMBDA with zip_iterator
by chun ping wang 08 Apr '06

08 Apr '06

I have several questions that I asked earlier but never got an answer. So I will start one by one.. a.) How do I use lambda with zip_iterator. (assuming you have a zip_iterator of vector, list, map)? Thats my first question...

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[FYI] RCF 0.2
by Jarl Lindrud 08 Apr '06

08 Apr '06

Hi all, I just thought I would announce that I've released v. 0.2 of RCF, a portable C++ IPC framework. It makes extensive use of boost, including Boost.Threads, Boost. Serialization, and the recently accepted asio library, so maybe people on this list will find it of interest :) http://www.codeproject.com/threads/Rcf_Ipc_For_Cpp.asp /Jarl.

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regex_search? Which subexpression smatch'ed?
by Lynn Allan 08 Apr '06

08 Apr '06

<alert comment="boost and regex newbie"> I'm using regex_search to detect which subexpression matched. I adapted the "Captures" example at: http://www.boost.org/libs/regex/doc/captures.html In the snippet below, it works ok to loop thru m[num].matched, but I was wondering if there was a more direct way of getting the information about which match was "hit". (The real application is going to have about 70 possible subexpressions to match against, instead of just four.) std::string contents("String has two, three, one, and four in it. "); boost::regex reg("(one)|(two)|(three)|(four)"); >From the above, I want the output to be: <match=2>two <match=3>three <match=1>one <match=4>four void test_search() { boost::smatch m; std::string contents("String has two, three, one, and four in it. "); boost::regex reg("(one)|(two)|(three)|(four)"); std::string::const_iterator it = contents.begin(); std::string::const_iterator end = contents.end(); while (boost::regex_search(it, end, m, reg)) { for (int num = 1; num <= 4; ++num) { if (m[num].matched == true) { std::cout << "<match=" << num << ">" << m[0] << std::endl; break; } } it = m[0].second; } } </alert>

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Re: [Boost-users] Boost Graph Library: Shortest path problem
by Grégoire Dooms 07 Apr '06

07 Apr '06

> > Date: Fri, 07 Apr 2006 11:39:20 +0200 > From: Steven Van Ingelgem <steven.vaningelgem(a)dpd.be> > Subject: [Boost-users] Boost Graph Library: Shortest path problem > To: boost-users(a)lists.boost.org > Message-ID: > <D3D675A5A7892D4287068E36BAFABB91016EC6DD(a)dcexch2.dpdbe.com> > Content-Type: text/plain; charset=us-ascii > > Hi, > > > > I have a problem with using (actually with finding the correct function > for my problem) the BGL. > > What I have is 5000 cities (vertices), 14000 roads (edges) between them > (directional roads)... And what I want to know is which roads I have to > take to encounter the least cities on my way. > Simple answer: take no road at all ;-) > Every edge has a weight of 1... So the documentation points me to using > the breadth_first_search algorithm. > > But this function - as far as I can see - goes through the entire graph. > I don't see any way to stop it (for example when it has discovered my > targetcity)?? > Sorry about that, I did know you had a target city. If you want to stop at the target city, the short answer is : use a visitor and throw an exception. void breadth_first_search(const Graph& g, typename graph_traits<Graph>::vertex_descriptor s, Buffer& Q, BFSVisitor vis, ColorMap color); The BFSVisitor can be made with the make_bfs_visitor http://www.boost.org/libs/graph/doc/bfs_visitor.html pass it an eventlist made of a predecessor_recorder and a custom eventprocessor use breadth_first_search(g, s, Q, make_bfs_visitor(make_pair(record_predecessors(predecessor_map, on_tree_edge), my_eventvisitor(target_node)), colormap) with struct my_eventvisitor : public boost::base_visitor<my_eventvisitor>{ typedef boost::on_finish_vertex event_filter; Graph::vertex_descriptor target; my_eventvisitor(Graph::vertex_descriptor target): target(target) {} template <class Vertex, class Graph> void operator()(Vertex v, Graph& g) { if (v==target){ throw TargetDiscoveredException; } }; I did not try to compile this but it should be along the lines of what you are looking for. > Is it possible someone can point me where I can have a look at? > In short I need to calculate (a lot) of roads from different cities to > other cities (so it's not that I always have the same root vertex). > > If you have to compute the distance for nearly all pairs of cities, you might want to look for one of the all pairs shortest paths. Hope this helps, -- Gregoire Dooms

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Re: [Boost-users] Serialization: crash atlaunchofprogram(duetoboost::serialization::base_object)
by RIVASSEAU Jean Noel 07 Apr '06

07 Apr '06

Hi I've tried to set up a small example that can reproduce the problem, however I cannot seem to succeed... One thing is sure, the crash is due to the BSL and the base_object thing, because if I change this only thing, the program goes from running perfectly to crashing at launch. Note that it is not really a problem of a class having multiple parents (this could happen if for example you use multiple inheritance). It is a problem of a class "switching parents". Jean-Noël -----Message d'origine----- De : boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] De la part de Robert Ramey Envoyé : vendredi 7 avril 2006 06:25 À : boost-users(a)lists.boost.org Objet : Re: [Boost-users] Serialization: crash atlaunchofprogram(duetoboost::serialization::base_object) Note that there is a test test_..._mi which tests serialization with classes which have multiple parents. So I would hope that this wouldn't be a problem. But you never know Robert Ramey RIVASSEAU Jean Noel wrote: > Ok, I will try to send a small example to the list tomorrow. In fact > I think everything lies in the fact that using > boost::serialization::base_object also registers the fact that the > classes are parent and child. The serialization system needs to know > that in order to make casts later. > > Somehow it probably does not like it when it tries to register > several different classes as the parent of the same class. > > Jean-Noël

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Boost Graph Library: Shortest path problem
by Steven Van Ingelgem 07 Apr '06

07 Apr '06

Hi, I have a problem with using (actually with finding the correct function for my problem) the BGL. What I have is 5000 cities (vertices), 14000 roads (edges) between them (directional roads)... And what I want to know is which roads I have to take to encounter the least cities on my way. Every edge has a weight of 1... So the documentation points me to using the breadth_first_search algorithm. But this function - as far as I can see - goes through the entire graph. I don't see any way to stop it (for example when it has discovered my targetcity)?? Is it possible someone can point me where I can have a look at? In short I need to calculate (a lot) of roads from different cities to other cities (so it's not that I always have the same root vertex). Thanks for any suggestion! Steven Van Ingelgem

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