August 2004 - Boost-users - lists.preview.boost.org

[Help on implementation of boost regex]
by hackervalley 02 Aug '04

02 Aug '04

Hello, I try to use boost regex . I don't have a lot of experience of using boost regex . Boost regex examples aren't so explicit for me. So I need some help to parse this example file. Point(1) = {0,0,0,0.1}; Point(2) = {1,0,0,0.1}; Point(3) = {0,1,0,0.1}; Point(4) = {1,1,0,0.1}; Line(1) = {1,2}; Line(2) = {2,4}; Line(3) = {4,3}; Line(4) = {3,1}; Line Loop(5) = {2,3,4,1}; Plane Surface(6) = {5}; I can't read each informations to use it after. I can't match for use IdentificationNumber of Point(IdentificationNumber). Actually my code look so : /* g++ -Wall -O2 -o ifstream ifstream.cc */ #include <iostream> #include <fstream> #include <string> /* boost regex header */ #include <boost/regex.hpp> using namespace std; using namespace boost; int main (int argc, char argv[]) { char buffer[256]; string filename; string inputstring; cout << "Input filename "; cin >> filename; ifstream readfile (filename.c_str (), ios::in); if (!readfile.is_open ()) { cout << "Error opening file" << endl; return 0; } regex exPoint ("Point"); regex exLine ("Line"); regex IdentificationNumber ("[:digit:]"); while (!readfile.eof ()) { readfile.getline (buffer, 200); inputstring = buffer; if (regex_search (inputstring, exPoint)) { cout << "Point" << endl; smatch result; if (regex_search (inputstring, result, IdentificationNumber)) { cout << "Identification Number " << result << endl; } else cout << "Error regex_match" << endl; } if (regex_search (inputstring, exLine)) { cout << "Line" << endl; } cout << buffer << endl; } readfile.close (); return (0); } Thank you for help. Best regards hackervalley http://hackervalley.free.fr

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Accessing Internal Properties
by Jeffrey Holle 02 Aug '04

02 Aug '04

I'm using BGL checked out of CVS on Tue Jun 29 05:25:17 EDT 2004. Also using gcc 3.4.1 on a linux machine. I've a question of how to access internal properties. It appears that there are basically two templated function families for this: get - returns a value get_property_iter_range - returns iterator range get_property - returns a reference Are there more? I'm interested in the later. I've seen in the examples get_property being used to access properties global to a graph, but not edge or vertex properties. What I'd like to see is a varient of get_property (or equivalent) that takes an edge descriptor, so it provides access to a particular edge's named property. Does what I'm looking for exist?

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using boost::shared_ptr with boost::signal
by oliver.kowalke＠t-online.de 01 Aug '04

01 Aug '04

Hi, I want to use boost::shared_ptr with boost::signal. class A { private: int _i; public: A() : _i( 0) {} void operator()( int, std::string & s) { i+= 1; } void operator()( std::string & s, int) { i+= 2; } }; boost::shared_ptr< A > a( new A() ); boost::signal< void( int, std::string &) > rsig; boost::singal< void( std::string &, int) > lsig; rsig.connect( a); lsig.connect( a); rsig(0,"called from right side"); lsig("called from left side",0); Because a is a smart_ptr this code would not compile because operator() is not a member function. If I dereference the smart pointer when I connect to signal, changes of a are never know by the other signal instance. Maybe I can use a proxy class which aggregates the smart pointer but maybe there is a better solution?! with best regards, Oliver -- "Der Spezialist ist ein Barbar, dessen Unwissenheit nicht allumfassend ist." Master's Voice, S.LEM

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boost.graph external properties question.
by Jeffrey Holle 01 Aug '04

01 Aug '04

HI, I'm starting a project that uses boost.graph and I'm trying to decide if I should use internal or external properties. My code that implements external properties is like, for example: typedef boost::graph_traits <GraphT>::vertex_descriptor Vertex; typedef std::map<Vertex,Vertex_Datum,ltDescriptor<Vertex> > VertexData; My question is: Given my use of Vertex as a key of a std::map, it needs to be unique. Is this uniqueness quality maintained across different graphs? That is, can I instanciate 2 GraphT objects and populate both, but maintain only one VertexData container? Assume that I am not defining any internal properties in GraphT.

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Vertex properties in BGL
by Ralph Wessel 01 Aug '04

01 Aug '04

I would like to use the BGL for a project I'm working on, but I haven't been able to find a particular piece of information. The system I'm modeling can be easily represented by a directed graph, but it seems that an essential vertex property can only be calculated on the fly based on the current in-edge and out-edge as the graph is traversed. Can this be supported in the BGL in a way which can feed this vertex property to the supplied algorithms?

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[HELP]How can I print a name of a node in a graph?
by Daniele Carlucci 01 Aug '04

01 Aug '04

Hi everybody, I wanna to print a graph but instead the id I want to print the name of the same. How can I make? I have token the list of the nodes from a list i. In i.name I have the name of the node. The code that I used to initialize the graph is: template <class Graph> void print(Graph& g) { typename Graph::vertex_iterator i, end; typename Graph::out_edge_iterator ei, edge_end; for(boost::tie(i,end) = vertices(g); i != end; ++i) { if (*i!=0){ cout<< *i << " --> "; for (boost::tie(ei,edge_end) = out_edges(*i, g); ei != edge_end; ++ei) cout << target(*ei, g) << " "; cout << endl;} } } void Main() { int nodo, cont, a; nodo=1; typedef graph_traits < file_dep_graph >::vertices_size_type size_type; size_type n_vertices; //Setta n_vertices con il numero di nodi n_vertices=id; // legge il numero di nodi file_dep_graph g(n_vertices); for (i=list.begin(); i != list.end(); ++i) { size_type k; for (cont=0; cont<(*i).v.size(); cont++) { a=(*i).v[cont]; //Connection between node "cont" and all the other nodes add_edge((*i).PID, a, g); } } print(g); Thanks Daniele

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Re: Way to print a route between two nodes
by Gustavo Sÿffffe1nchez 01 Aug '04

01 Aug '04

I don't know exactly how you are traversing those nodes in the path, - ie how do find the path -, but as far as I know you have to use a visitor with an algorithm such as dijisktra shortest paths, so you define the event point, on_finish_vertex for example where you want the visitor to be called. This algorithm also stores in a vector the minimum weight pahts encountered from an specific origin vertex so you can go over those paths from the last vertex to this origin. Hope to be of help ------------------------------ Message: 10 Date: Thu, 29 Jul 2004 15:33:34 +0200 From: Daniele Carlucci Subject: [Boost-users] Way to print a route between two nodes To: boost-users(a)lists.boost.org Message-ID: <4108FCAE.8040301(a)email.it> Content-Type: text/plain; charset=us-ascii; format=flowed Hi all, there is a way to print a route between two nodes? If I have for ie: 8 nodes. A possible route is 1->3->2->6->8 How can I print it? I have only seen that it's used the way to print for every node, all the nodes near that one. Thanks Daniele ------------------------------ ---------------------------------

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serialization for indexed_set?
by Jedediah Smith 01 Aug '04

01 Aug '04

I'm trying to write generic boost::serialization functions for boost:indexed_set and I'm in a bit over my head. The serialization docs say to use something like the following for generic types: template<class Archive, class T> inline void save( Archive & ar, const std::auto_ptr<T> &t, const unsigned int file_version ){ ar << t.get(); } This is a non-intrusive save function for std::auto_ptr. The tricky thing is that the template parameters for indexed_set are much more complicated and the default index may either be regular (set-like) or sequenced (list-like). How would this be handled?

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boost for visual c++
by Jean-Michel besnard 01 Aug '04

01 Aug '04

Hi, How can I install the lib boost::random to use it within Visual C++ (6) ? Is there a built library to be downloaded somewhere or do I have to build it myself ? JM

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