July 2004 - Boost-users - lists.boost.org

boost::shared_ptr and stl algorithms
by Bill Eidson 15 Apr '05

15 Apr '05

std::vector< boost::shared_ptr<T> > TVec; I want to write a function object to run std::for_each. to do somework against members of T and accumulate results in functor. My attempts have failed in VC7 with memory errors in my operator() method. struct fo { bool operator()( boost::shared_ptr<T>& t ) { return true; } }; Thanks in advance bille

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Will libraries built on WinNT run on Win98? (MinGW)
by Reed Hedges 31 Mar '05

31 Mar '05

I know that Win98 is not really supported, but is there any chance that libraries (specifically thread and regex) that were build on WinNT using MinGW work on Win98 (in MinGW)? My guess is no, but has anyone tried it? thanks reed

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Bug in lexical_cast<> with doubles
by Leon Raj 29 Jan '05

29 Jan '05

I think I've found a bug in the boost::lexical_cast<> library (v1.31.0) on WinXP SP1, MSVC 6.0 (sp5) and MSVC.NET 2003. --- Start code snippet --- #include <boost/lexical_cast.hpp> #include <iostream> int main( int argc, char* argv[] ) { double dMax = = std::numeric_limits< double >::max(); // On a Win32 x86 system, dMax is now 1.7976931348623157e+308 // This is successful and strMax is "1.797693134862316e+308" std::string strMax = boost::lexical_cast< std::string >( dMax ); try { double newDMax = boost::lexical_cast< double >( strMax ); std::cout << "Successfuly" << std::endl; } catch ( boost::bad_lexical_cast& ) { std::cout << "Failed to cast" << std::endl; } // On a Win32 x86 system, this always fails, // because (I think) strMax overflows a double, // because 1.7976931348623157e+308 is *rounded UP* // to 1.797693134862316e+308, which cannot be // represented by a double } --- End code snippet --- ----------------------------------------------------- Leon Raj Senior Engineer Invetech Pty. Ltd. Phone: +61 3 9211 7000 (Switchboard) +61 3 9211 7938 (DDI) leon.raj(a)invetech.com.au IMPORTANT - This e-mail and any attachments may be confidential. Any retransmissions, dissemination or other use of these materials by persons or entities other than the intended recipient is prohibited. If received in error, please contact us and delete all copies. Before opening or using attachments, check them for viruses and defects. Our liability is limited to resupplying any affected attachments. [Any representations or opinions expressed in this e-mail are those of the individual sender, and not necessarily those of Vision Systems Limited].

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problem compiling with threads and stlport
by Nicholas Cain 31 Aug '04

31 Aug '04

hi, I'm new to boost, stlport and programming on linux in general, so I apologise now for any obvious beginner errors! I'm using mandrake 10 and gcc 3.3.2, and using root I created STLport 4.6.2 libraries, and then created all the boost 1.31.0 libraries using bjam -sTOOLS=gcc-stlport -sBUILD="debug release <stlport-iostream>on" install I had to have this little lot in my bashrc file to do it; export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib export STLPORT_VERSION=4.6.2 export STLPORT_ROOT=/home/ncain export STLPORT_LIB_DIRECTORY=/usr/local/lib export STLPORT_INCLUDE_DIRECTORY=/usr/local/include/ export PYTHON_VERSION=2.3 export PYTHON_ROOT=/usr Everything seemed to build ok, apart from an "../lib/libstlport_gcc_debug.so does not exist" error in the final part of the stlport build and a continual "warning: "_POSIX_C_SOURCE" redefined" warning during the boost build. Both the stlport and boost libraries are in /usr/local/lib ok, and building thread/test passed fine too. I altered one of the tutorial files to use _STL and also created a makefile (since bjam is a bit beyond me at the moment), and these appear as; testboost.cpp: #include <boost/thread/thread.hpp> #include <boost/thread/xtime.hpp> #include <iostream> using namespace _STL; struct thread_alarm { thread_alarm(int secs) : m_secs(secs) { } void operator()() { cout << "alarm sounded..." << endl; } int m_secs; }; int main(int argc, char* argv[]) { int secs = 5; thread_alarm alarm(secs); boost::thread thrd(alarm); thrd.join(); } makefile: .PHONY: all clean ALL = testboost INCS = -I"/usr/local/include/stlport" \ -I"/usr/local/include/boost-1_31" LIBS=-L"/usr/local/lib" -lstlport_gcc -lboost_thread-gcc-mt-p -lpthread .cpp: ${CXX} ${INCS} -pthread -o $@ $^ ${LIBS} all: ${ALL} clean: ${RM} core* *.o ${RM} ${ALL} make returns this error; g++ -I"/usr/local/include/stlport" -I"/usr/local/include/boost-1_31" -pthread -o testboost testboost.cpp -L"/usr/local/lib" -lstlport_gcc -lboost_thread-gcc-mt-p -lpthread /home/ncain/tmp/ccZWBPnj.o(.text+0x4b): In function `main': : undefined reference to `boost::thread::thread[in-charge](boost::function0<void, _STL::allocator<boost::function_base> > const&)' collect2: ld returned 1 exit status make: *** [testboost] Error 1 using -lboost_thread-gcc-mt-gdp makes no difference, however changing the cpp to use the std libraries works fine (builds and runs correctly). Have I made a mistake in building the boost libraries or possibly in my makefile? thanks, nik

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mpl related question
by Istvan Buki 06 Aug '04

06 Aug '04

Hello mpl experts, I'm trying to initialize the elements of an array using rules defined in a list of structures. The code below illustrate what I'm trying to achieve. The problem I have with this code is that the First_Descriptor structure contain this index member that will be used to access the right item of the array. This is not nice because it force the writer of this structure to deal with implementation details. Is there a way to get rid of this index typedef in the *_Descriptor structures by using another construct from the mpl that would generate it ? // The array I need to initialize. Array_Item array[2]; struct Initializer { template < typename U > void operator()( mpl::identity< U > ) { // This is where array elements are initialized. // Note how the index member is used. array[U::index::type::value].some_method( U::a_param ) ; } } ; // This is one structure containing rules used to initialize array items. struct First_Descriptor { enum { a_param = 123456 } ; typedef mpl::int_< 0 > index ; } ; struct Second_Descriptor { enum { a_param = 2567 } ; typedef mpl::int_< 1 > index ; } ; // The list of structures containg rules to be applied during array // initialization. typedef mpl::list< First_Descriptor, Second_Descriptor > Descriptors ; // traverse the list and apply the rules. mpl::for_each< Descriptors, mpl::make_identity<_> >( Initializer( ) ) ; Thanks for any help you could provide. Istvan

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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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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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