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

[BGL, Graph] listS and property maps
by Stephane Grabli 17 Nov '05

17 Nov '05

Hi, I'm new to the BGL and I'm trying to use the strong_components algorithm, defined this way: template <class Graph, class ComponentMap, class P, class T, class R> typename property_traits<ComponentMap>::value_type strong_components(Graph& g, ComponentMap comp, const bgl_named_params<P, T, R>& params = all defaults) with a graph defined like this: typedef adjacency_list<listS,listS,directedS> Graph; (in particular using listS for vertices storage). Does anyone know how I should declare the ComponentMap property map? I couldn't figure this out from the documentation and the examples I've seen all assume that a vecS type storage is used for vertices in the graph. Thanks! Stephane

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CVS silence:)
by Serge Skorokhodov 17 Nov '05

17 Nov '05

Hi, boost CVS has not changed for a few days. Should cvs update arguments be modified? TIA -- Serge

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[serialization] template point
by codeur＠altern.org 17 Nov '05

17 Nov '05

Hello I'm a new user of the serialization library and I didn't understand how I could serialize the following Map class : #include <vector> template<typename T> class Point { private: T x; T y; }; template<typename T> class Map { private: std::vector < Point<T> * > map; }; int main() { Map<double> m; /* double or float or int or user defined float/integer with infinite precision */ return 0; } Could somebody help me ? Thanks!

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[iostreams] WinRar cannot read zlib archive
by Christian Henning 16 Nov '05

16 Nov '05

Hi there I just have a simple question regarding the format of a zlib archive. Somehow WinRar cannot read the archive. If I use the simple example application provided in the zlib distribution WinRar is able to read it. This makes me wondering what difference is in the archive generated by boost::iostreams? Here is my example code which works fine. I using VC7.1 and Boost 1.33 #include <iostream> #define BOOST_IOSTREAMS_NO_LIB #include <boost/iostreams/device/file.hpp> #include <boost/iostreams/filtering_stream.hpp> #include <boost/iostreams/filter/zlib.hpp> namespace io = boost::iostreams; int _tmain(int argc, _TCHAR* argv[]) { { io::filtering_ostream out; out.push( io::zlib_compressor() ); out.push( io::file_sink( "hello.zip" )); out << "Hello boost::iostreams"; //close the file } io::filtering_istream in; in.push( io::zlib_decompressor() ); in.push( io::file_source( "hello.zip" )); std::string strMessage; std::getline( in, strMessage ); std::cout << strMessage << std::endl; return 0; } Besides the problem, seems that boost::iostream is an amazing lib and a huge contribution for the C++ community. Thanks, Christian

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[MPL] how do i validate a predicate template?
by Cory Nelson 16 Nov '05

16 Nov '05

Is there any way to validate a predicate (function, functor etc) template with MPL? ie, something like: BOOST_MPL_ASSERT((and_< is_function<Predicate>, equal_to<function_traits<Predicate>::arity, int_<1> >, is_same<function_traits<Predicate>::result_type, int >, is_same<function_traits<Predicate>::arg1_type, int > >)); -- Cory Nelson http://www.int64.org

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Re: [Boost-users] Inheritance
by james.jones＠firstinvestors.com 16 Nov '05

16 Nov '05

Hi Azam, Are you sure you want to inherit? Might it make sense to make a Boost graph object a private variable which you construct and then modify in your constructor? - James Jones Administrative Data Mgmt. (v)732-510-1806 375 Raritan Center Pkwy, Suite A (f)732-510-1855 Edison, NJ 08837 Visit us on the web at http://www.firstinvestors.com/ --- Original Message --- Date: Tue, 15 Nov 2005 18:53:15 -0800 From: "azam ." <boost80(a)gmail.com> Subject: [Boost-users] Inheritance To: boost-users(a)lists.boost.org Message-ID: <825e260c0511151853q4b0d599ek5a0d6d3daa28dec3(a)mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" Hi, I want to use Boost Graph Library via inheritance. Actually I want to define a graph which is an adjacency_list graph and is created in a special way. I thought of making it a derived class of adjacency_list and then define constructors to construct objects of this class. But my problem is how to (for example) set vertex properties in the constructor? Regularly if I want to add properties to vertices on a graph g, I use vertices(g) to get iterator of vertices and then I use this iterator, but what can I do in the constructor? I have no such graph object there and I can't use "this" reference too. Any help would be really appreciated. Thanks Azam

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Collections of shared_ptr<Base> and shared_ptr<Derived>
by Keith Weintraub 16 Nov '05

16 Nov '05

Folks, What is the best way to pass a std::vector<boost::shared_ptr<Derived> > to a function that expects a std::vector<boost::shared_ptr<Base> >? Can I use a cast or should I create a new std::vector<boost::shared_ptr<Base> > by iterating over the std::vector<boost::shared_ptr<Derived> >? Here is some sample code. What f is doing is not important it is just an example: class A { // This class is from a library I have no control over. public: virtual string getName() { return string("A");} }; class B : public A { // I need to create B from A to have extra functionality public: virtual string getName() { return string("B");} virtual string getLongName() { return string("This is B");} }; void f(std::vector<boost::shared_ptr<A> > &v) { // This function is from a library that I have no control over. for(int i = 0; i < v.size(); i++) cout << v[i]->getName(); } int main(char *argv, int arc) { std::vector<boost::shared_ptr<B> > bvec(10); boost::shared_ptr<B> bPtr(new B); bvec[0] = bPtr; f(bvec); // This should not compile. <------------------------- } The last line (with the arrow) won't compile because std::vector<boost::shared_ptr<B> > cannot be converted to std::vector<boost::shared_ptr<A> >.

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Boost.Iostreams - Filtering Stream questions (flushing, interactive input)
by Michael Rickert 16 Nov '05

16 Nov '05

I've been trying to use Boost.Iostreams, with mixed success. I've got a few more stumbling blocks that hopefully I can get some help with :-). First, I have a socket class, which I've used Boost.Iostreams to create a nice interface for. Quick details: class winsock_device { typedef boost::iostreams::bidirectional_device_tag category; //..implementation.. }; class winsock_socket { typedef winsock_device stream_device_type; typedef boost::iostreams::stream_buffer< stream_device_type > stream_buffer_type; typedef std::iostream stream_type; stream_device_type m_stream_device; stream_buffer_type m_stream_buffer; stream_type m_stream; public: winsock_socket( SOCKET raw_socket ) : m_stream_device( raw_socket ) , m_stream_buffer( m_stream_device ) , m_stream( & m_stream_buffer ) {} stream_type & stream() { return m_stream; } //..more implementation.. }; The implementation seems to work, tests show it to be working fine for input and output (with output needing to be flushed). Only problem is that the newlines are mismatched - a simple telnet chat client gets supurflous \r characters using std::getline, so I decided to wrap around the stream using a boost::iostreams::filtering_stream< boost::iostreams::bidirectional >, which is where things fall apart. I took my simple example, and replaced: std::iostream & ios = socket->stream(); with: namespace bios = boost::iostreams; bios::filtering_stream< bios::bidirectional > ios; ios.push( socket->stream() ); both with the same testing code: std::string nickname; ios << "Welcome, user - please enter a nickname:\n" << std::flush; socket->stream().flush(); std::getline( ios , nickname ); ios << "Welcome, " << nickname << "\n"; ios << "*** actual chatting not yet implemented ***\n"; ios << "Disconnecting you now, bye " << nickname << " !!!\n" << std::flush; socket->stream().flush(); This failed to work at all at first, eventually I figured out I needed to flush first the ios stream, and then the underlying socket->stream. This brings me to: question 1: Is there a workaround to allow an ending stream of (std::iostream &) to be flushed automatically by flushing filtering_stream? Even with no filters installed, however, the program freezes (until I shut down the telnet client) when I attempt to read a line from the stream, even after entering multiple newlines - I'm not exactly sure what's happening here. This brings me to: question 2: How can I get the input moving through my stream? Do I need to start a seperate thread to constantly flush() the stream that the main thread is blocked on i/o for? Thanks, -Mike

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Inheritance
by azam . 16 Nov '05

16 Nov '05

Hi, I want to use Boost Graph Library via inheritance. Actually I want to define a graph which is an adjacency_list graph and is created in a special way. I thought of making it a derived class of adjacency_list and then define constructors to construct objects of this class. But my problem is how to (for example) set vertex properties in the constructor? Regularly if I want to add properties to vertices on a graph g, I use vertices(g) to get iterator of vertices and then I use this iterator, but what can I do in the constructor? I have no such graph object there and I can't use "this" reference too. Any help would be really appreciated. Thanks Azam

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[IOStreams] Memory leaks when using zlib_compressor
by Christian Henning 16 Nov '05

16 Nov '05

Hi there, I couldn't find anything in the archives for my problem. Purify is showing several memory leaks when I execute the following program: int _tmain(int argc, _TCHAR* argv[]) { // prepare some data to write unsigned int nSize = 1000000; char* pBits = new char[nSize]; ::memset( pBits , 0 , nSize ); for( unsigned int i = 0; i < nSize; i++ ) { pBits[i] = i; } // write to file io::filtering_ostream out; out.push( io::zlib_compressor() ); out.push( io::file_sink( "test.zip", std::ios::binary )); out << nSize; out.write( pBits , nSize ); // clean up delete[] pBits; return 0; } I think the program is right. I'm using Boost 1.33 with VC 7.1. Here is what purify spits out: [I] Summary of all memory leaks... {268108 bytes, 6 blocks} [I] MPK: Potential memory leak of 196608 bytes from 3 blocks allocated in boost::iostreams::detail::zlib_base::do_init(zlib_params::iostreams::boost const&,bool,(*)(void *,UINT,UINT),(*)(void *,void *),void *) [IOStreams.exe] [W] MLK: Memory leak of 71360 bytes from 2 blocks allocated in boost::iostreams::detail::zlib_base::do_init(zlib_params::iostreams::boost const&,bool,(*)(void *,UINT,UINT),(*)(void *,void *),void *) [IOStreams.exe] Is that a know issue? I guess so, but has it been resolved? Thanks, Christian

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