March 2003 - Boost-users - lists.preview.boost.org

Generic output manipulator for lists
by Reece H Dunn 14 Mar '03

14 Mar '03

I have a manipulator that will display lists in the basic form: [ i1, i2, ... , in ] It has a usage for a container where it prints the entire container in the list notation; it also has the ability to select the range to be displayed: template< typename ForwardIterator > inline formatlist_t< ForwardIterator > formatlist( ForwardIterator first, ForwardIterator last ); template< typename Container > inline formatlist_t< typename Container::iterator > formatlist( Container & c ); Example usage of the manipulator is thus: std::vector< int > v( 10 ); std::generate( v.begin(), v.end(), std::rand ); // basic list formatting std::cout << "list = " << stl::formatlist( v ) << '\n'; // use the form :- ( i1, ..., in ) std::cout << "list = " << stl::formatlist( v ).format( '(', ')' ) << '\n'; // use the form :- [ i1 | ... | in ] std::cout << "list = " << stl::formatlist( v ).format( '|' ).space( true, true ) << '\n'; You can currently configure the opening and closing elements of the list (default to '[' and ']'); the seperator used (defaults to ','); the spacing around the list (default true) and before/after the seperator (defaults to after the seperator only). I would like to submit it into the boost library. Are there any comments/suggestions/questions? I have currently only tested it with MS VC++.NET 7, but have written the code to not use any MS specific features so it should be usable on most of the current compilers. -rhd- mailto:msclrhd@hotmail.com

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boost::random examples of pseudo-random number generation
by agiatojon 14 Mar '03

14 Mar '03

Hello all, I would like to use boost for a project I am doing but have not been able to find an example of how one would use each class. I am sure it must be me but I am finding the doumentation a bit hard to read, and I am sure it is much easier than I am finding it. In case it is relevant, I am using MSVC++ 7.0. Thanks for any and all help/suggestions! Jon Agiato JonAgiato(a)nyc.rr.com

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Regex++ bug?
by sugi＠dream.big.or.jp 14 Mar '03

14 Mar '03

Hi. I found some strange behaviors in Regex++. For details, please see the following source. These are bugs? or do I have mistaken? boost's version is 1.29.0. --- #include <iostream> #include <boost/regex.hpp> using namespace std; void p(const char *r, const char *s){ cout << endl << "*********" << endl; cout << "regex: " << r << endl; cout << "string: " << s << endl; cout << "result: " << (boost::RegEx(r).Search(s) ? "found" : "not found") << endl; } int main(){ // I think this must not match, but this do. p("a\\Z", "a\nb"); // These match. Correct behaviors. p("()", "abc"); p("^()", "abc"); p("^()+", "abc"); p("^(){1}", "abc"); // But these don't match. // Are these wrong? p("^(){2}", "abc"); p("^((){2})", "abc"); // I feel these somewhat strange. // But I have little confidence to say that this is a bug. p("()", ""); // found (OK) p("()\\1", ""); // not found (this must match?) p("()\\1", "a"); // found (OK) p("a()\\1b", "ab"); // found (OK) p("a()b\\1", "ab"); // not found (this must match?) return 0; } --- Kouhei Yanagita

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filling in vertex_name_t property for adjacency_list
by Dieter Vrancken 14 Mar '03

14 Mar '03

Hi, I'm trying to create a graph that has a name for each vertex. Below is what I've come up with so far. I really don't know what's wrong with it. Can any of you help me out? I'm using boost 1.29.0 with Visual Studio6.0sp5 on win2k. I'm getting some errors on the line that's supposed to get the property map. Then a whole bunch of others because in the end 'name' has an incomplete type. kind regards, Dieter Vrancken // create some vertex names typedef std::set<std::string> StringSet; StringSet v_names; std::string names[] = { "v1", "v2", "v3" }; v_names.insert(names, names + sizeof(names)/sizeof(names[0])); // declare the graph typedef boost::adjacency_list<boost::setS, boost::vecS, boost::directedS, boost::vertex_name_t, boost::no_property, boost::graph_name_t, boost::setS> Graph; Graph g(v_names.size()); // get the property map for the vertex names boost::property_map<Graph, boost::vertex_name_t>::type name = boost::get(boost::vertex_name, g); // fill in the names StringSet::const_iterator ss_it = v_names.begin(), ss_end = v_names.end(); int i = 0; for(; ss_it!=ss_end; ++ss_it, ++i) boost::put(name, i, *ss_it);

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What is the relationship between BGL's edge_descriptor and edge_iterator?
by Jeff Holle 14 Mar '03

14 Mar '03

What is the relationship between an "edge_descriptor" and what an edge_iterator dereferences? I'm having problems coding the following: myFunct(GraphT& g) { typedef graph_traits<GraphT>::edge_descriptor Edge; typedef map< Edge, Edge_Datum> Edge_Data; Edge_Data edge_data; graph_traits<GraphT>::edge_iterator ei, ei_end; for(tie(ei,ei_end)=edges(graph);ei!=ei_end;++ei) edge_data.insert( make_pair(*ei, Edge_Data())); << blows up here. }

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Minor bug in docu of lambda library
by Peter Klotz 13 Mar '03

13 Mar '03

URL: http://www.boost.org/libs/lambda/doc/ar01s03.html#id2741989 The code fragment template <class T> : public binary_function<T, T, T> struct plus { should read template <class T> struct plus : public binary_function<T, T, T> { Best regards, Peter.

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slightly off-topic: recommendation for algorithm timing?
by Alejandro Escalante Medina 13 Mar '03

13 Mar '03

This is may a little out of the topic, but maybe you could recommend me some good class for measuring code execution times... Thanks, Alex _________________________________________________________ Do You Yahoo!? La mejor conexión a internet y 25MB extra a tu correo por $100 al mes. http://net.yahoo.com.mx

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Blind dynamic cast
by lorydido 13 Mar '03

13 Mar '03

Good morning, First of all, thank you very much for your help in advance. I have a problem in dynamic casting. sc_object *o = (sc_object*)(x[i]); if (typeid(*o)==typeid(sc_out<bool>)) sc_out<bool> *thisPort=dynamic_cast<sc_out<bool> *>(o); sc_out<T> type is a polymorphic template class that inherits sc_object class. I would like to cast the polymorphic object (*o) without to know the template type T of sc_out<T>. I would avoid all the possible casts that can result in an enormous computational burden. I would like to access to the methods of sc_out<T> type.I cannot modify the code of sc_out<T> and sc_object.Does exist any way to perform this "blind" operation? Does exist a boost library that allows the use of the string typeid.name() as type in dynamic cast operation? thank you very much in advance Lorenzo PIERALISI

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compose_f_gx problem
by pirx 13 Mar '03

13 Mar '03

hi, I've got a question regarding the compose_f_gx function object. I tried to use it in combination with this small example. class Element { public: explicit Element(int nVal) : m_nValue(nVal) {} const int getValue() const { return m_nValue; } private: int m_nValue; }; Element el(3); // a == true; bool a = bind<bool>(equal_to<int>(), _1, 3)(3); // b == 3; int b = mem_fn(&Element::getValue)(el); // c == true bool c = bind<bool>(equal_to<int>(), _1, 3) (mem_fn(&Element::getValue)(el)); // d should also be true, but does not compile bool d = compose_f_gx(bind<bool>(equal_to<int>(), _1, 3), mem_fn(&Element::getValue))(el); The last line does not compile. I don't know why. So what's wrong? thanks, andreas

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Re: [Boost-Users] slightly off-topic: recommendation for algorithm timing?
by Paul Grenyer 13 Mar '03

13 Mar '03

Hi > This is may a little out of the topic, but maybe you > could recommend me some good class for measuring code > execution times... Would boost's timer do what you want? Regards Paul Paul Grenyer Email: pjgrenyer(a)iee.org Web: www.paulgrenyer.co.uk "So long and thanks for all the fish."

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