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

Re: Boostifying GluCat
by Paul C. Leopardi 11 May '04

11 May '04

Hi all, Back in January last year, I asked if there was any documentation which could help me to Boostify GluCat: http://lists.boost.org/MailArchives/boost-users/msg02787.php Since then I have been very busy, but in the next few months I may be able to find the time to get this done right, so I'm asking again: GluCat is a new numeric template class library, hopefully destined for promotion to Boost. I would like to know where there is some documentation on how to: 1. Add concepts. Is there such a thing as a non-commutative multiplication concept? How do I check concepts? 2. Add numeric limits. Limits of U<T> would default to limits of T. 3. Add numeric promotion_traits. What are promotion_traits ? There is a discussion on ublas-dev mailing list about promotion_traits within uBLAS. 4. Add numeric type_traits. Also, is there a set of documented procedures which explain what is required for a library to be included in Boost? GluCat uses uBLAS. Should I take these questions to ublas-dev? Thanks

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Re: is_sequence
by Rozental, Gennadiy 11 May '04

11 May '04

> It already works. If you want to detect STL sequence-ness, you'll > have to try some nasty hacks. I'm have doubts about whether it's even > possible to approximate that metafunction in portable code. Wouldn't something about these lines work? template<typename T> char test( T const&, long ); template<typename T> int test( std::list<T> const&, int ); template<typename T> struct is_list { static T t; enum { value = sizeof( test( t, 0 ) ) == 4; } }; Gennadiy.

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[BGL] graph constness and vertex/edge iterators
by Cyrille Damez 11 May '04

11 May '04

Hi all, I'm currently trying to write a wrapper in order to use the BGL algorithms and visitors on a home-made graph class. If I'm not mistaken, this requires me to write (amongst other things) a couple functions that will return iterators over my graph edges and vertices, eg: std::pair<graph_traits<MyGraph>::out_edge_iterator, graph_traits<MyGraph>::out_edge_iterator > out_edges(graph_traits<MyGraph>::vertex_descriptor u, const MyGraph& g) and similarly in_edges(...) , vertices(...) and edges(...) functions. However, it seems that this function profile forces me to do a const_cast on g when implementing the function body since the out_edge_iterators are not const iterators, though they point to internal elements of g. I had a look at the example given in the documentation (dealing with converting LEDA graphs to the BGL), but I didn't see anything helping me on this particular issue (also, the example in the doc is a bit outdated since it uses the deprecated Boost iterator adaptors). Am I forced to rely on const_cast in these functions, or is there a way to declare my graph edges, vertices and the corresponding iterators as const in my graph_traits class ? I'm a newbie with the BGL, and more generally with this whole traits/template specialization style of programming, so please excuse me if I overlooked something obvious. Cheers.

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is_sequence
by Wolfgang Meyer 11 May '04

11 May '04

Is boost::mpl::is_sequence supposed to work with gcc 3.2.2 ? I'm trying to use it, but get "false" for boost::mpl::is_sequence<std::list<int> >::value using boost 1.31.0. The same happens with boost::mpl::has_begin. I'm working with FreeBSD 5.1. Any hints how to get it to work would be greatly appreciated. Wolfgang Meyer

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BOOST_NO_MEMBER_TEMPLATE_FRIENDS
by Witz 11 May '04

11 May '04

if the following code is commented out from visualc.hpp the standard streaming operators become available for mersenne_twister - and they seem to work fine. is this a bug or have i just been fortunate in my experimentation? #if _MSC_VER <= 1310 # define BOOST_NO_MEMBER_TEMPLATE_FRIENDS #endif ian whittley

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BGL: using an edge_descriptor as key in a map
by boost＠spyderworks.de 11 May '04

11 May '04

Hi, is it possible to use an edge_descriptor (boost::graph_traits<G>::edge_descriptor) as key in a map? I intend to write a visitor class which sets a boolean to each edge, and therefore I need the edge as key. The result of my first try is, that the compiler complains about the missing '<' operator of the key in the map. Best regards Stefan Rauch

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RE: [Boost-users] help: boost::thread and compile error
by Ben Hutchings 10 May '04

10 May '04

Guillermo Martony <gmartony(a)cue.com.uy> wrote: > Greetings, > The following code taken from an example compiles without errors: > > #include <boost/thread/thread.hpp> > #include <boost/thread/xtime.hpp> > #include <iostream> > class thread_alarm > { <snip> > }; > > int main() > { > int secs = 5; > std::cout << "setting alarm for 5 seconds..." << std::endl; > thread_alarm alarm(secs); > boost::thread thrd(alarm); > thrd.join(); > return 0; > } > > But adding a std::fstream varible to the thread_alarm class: <snip> > Results in the following compilation error: > > c:\opt\include\boost\function\function_template.hpp(289): > error C2664: 'void > boost::function0<R,Allocator>::assign_to(Functor)' : cannot convert > parameter 1 from 'const thread_alarm' to 'thread_alarm' > with > [ > R=void, > Allocator=int, > Functor=thread_alarm > ] The boost::thread constructor copies its argument, so the thread_alarm class needs to be copiable, but std::fstream is not copiable. You might be better off using Boost.Bind to produce a lightweight functor.

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boost::bind vs boost::mem_fun (was RE: [Boost-users] Re: shared_ptrs with std::mem_fn)
by Mark Storer 10 May '04

10 May '04

> > template<class _R, class _Ty> > > class mem_fun_t : public unary_function<_Ty *, _R> { > > public: > > explicit mem_fun_t(_R (_Ty::*_Pm)()) > > : _Ptr(_Pm) {} > > _R operator()(_Ty *_P) const > ^^^^^^^ > > {return ((_P->*_Ptr)()); } > > private: > > _R (_Ty::*_Ptr)(); > > }; > > --- > > <...> > No, the relevant part is the signature I highlighted above. <...> > > All I have to say is "use boost::mem_fn, which works, and never > touch the one in std::". Thanks for clearing that up, it was really bugging me. So to speak. ;) I've recently started using boost::bind, and I think I'm in love. But boost::mem_fun raises another question in my mind: Are there any cases where "boost::bind( &foo::bar, _1 )" is superior to "boost::mem_fun( &foo::bar )" (other than a few less keys to press)? I'd say that boost::bind is clearly supperior when "bar" takes a parameter, but when it does not, the water gets a little muddy. I'd imagine that you wouldn't get the long stream of error messages (expected N params not Y, expected N + 1 params, not Y, expected N + 2 ...) from bind when all the different variants miss, but is there anything else? --Mark Storer Senior Software Engineer Verity, Inc.

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RE: [Boost-users] boost 1.30 / date_time / link problem with VC7
by Ben Hutchings 10 May '04

10 May '04

Dan Dimerman <dan_dimerman(a)hotmail.com> wrote: > I'm having the following problem when linking a MSWindows MFC > application with the static library libboost_date_time.lib using > DevStudio .Net 7.0. > > The output looks like this: > > ------ Build started: Project: Main, Configuration: Debug Win32 ------ > Linking... > MSVCRTD.lib(ti_inst.obj) : error LNK2005: "private: __thiscall > type_info::type_info(class type_info const &)" > (??0type_info@@AAE@ABV0@@Z) already defined in libcmtd.lib(typinfo.obj) > MSVCRTD.lib(ti_inst.obj) : error LNK2005: "private: class type_info & > __thiscall type_info::operator=(class type_info const &)" > (??4type_info@@AAEAAV0@ABV0@@Z) already defined in > libcmtd.lib(typinfo.obj) > LINK : warning LNK4098: defaultlib 'MSVCRTD' conflicts with > use of other libs; use /NODEFAULTLIB:library > Debug/Main.exe : fatal error LNK1169: one or more multiply > defined symbols found > > I am working with the "Multi-threaded Debug (/MTd)" version of > libraries. > Tried using alternatives, but I got errors elsewhere and the > errors above persisted. > From boost, I am using the library built at "My Documents\Visual > Studio Projects\boost\libs\date_time\build\bin\libboost_date_time.lib > \vc7\debug\runtime-link-dynamic" > > Any help will be greatly appreciated... You are using the debug DLL version of the date_time library. In order to share a heap with the main program this uses the debug DLL version of the C++ run-time library (MSVCRTD) and requires that the main program uses it too. You must either: (1) Build and use the debug multi-threaded static version of the date_time library. (2) Use the debug DLL versions of the C++ run-time library and MFC in your main program.

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help: boost::thread and compile error
by Guillermo Martony 10 May '04

10 May '04

Greetings, The following code taken from an example compiles without errors: #include <boost/thread/thread.hpp> #include <boost/thread/xtime.hpp> #include <iostream> class thread_alarm { public: thread_alarm(int secs) : m_secs(secs) { } void operator()() { boost::xtime xt; boost::xtime_get(&xt, boost::TIME_UTC); xt.sec += m_secs; boost::thread::sleep(xt); std::cout << "alarm sounded..." << std::endl; } private: int m_secs; }; int main() { int secs = 5; std::cout << "setting alarm for 5 seconds..." << std::endl; thread_alarm alarm(secs); boost::thread thrd(alarm); thrd.join(); return 0; } But adding a std::fstream varible to the thread_alarm class: #include <fstream> #include <boost/thread/thread.hpp> #include <boost/thread/xtime.hpp> #include <iostream> class thread_alarm { public: thread_alarm(int secs) : m_secs(secs) { } void operator()() { boost::xtime xt; boost::xtime_get(&xt, boost::TIME_UTC); xt.sec += m_secs; boost::thread::sleep(xt); std::cout << "alarm sounded..." << std::endl; } private: int m_secs; std::fstream fs; // only this line was added }; int main() { int secs = 5; std::cout << "setting alarm for 5 seconds..." << std::endl; thread_alarm alarm(secs); boost::thread thrd(alarm); thrd.join(); return 0; } Results in the following compilation error: c:\opt\include\boost\function\function_template.hpp(289): error C2664: 'void boost::function0<R,Allocator>::assign_to(Functor)' : cannot convert parameter 1 from 'const thread_alarm' to 'thread_alarm' with [ R=void, Allocator=int, Functor=thread_alarm ] I'm using Microsoft Studio .NET 2002 Thanks in advance for any help. Guillermo Martony

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