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

function_traits<> help, ASAP please!
by Hossein Haeri 26 Dec '04

26 Dec '04

Dear all, According to the Boost.Type_Traits I guess that function_traits<> is supposed to be of the most docile ones. After all it's got a few lines of comment... Don't know how, and why, but the following plain-jane programme #include <iostream> #include "boost\type_traits\function_traits.hpp" int main() { typedef void (*FType) (); typedef typename boost::function_traits<FType> ::result_type return_type; cin.get(); return 0; } Gives me the following error under GCC 3.3.1 (which I'm sure supports partial template specialisation): Compiler: Default compiler Building Makefile: "C:\Documents and Settings\Hossein\My Documents\My Programmes\Probability I\Distributions\7.2.1\Makefile.win" Executing make... make.exe -f "C:\Documents and Settings\Hossein\My Documents\My Programmes\Probability I\Distributions\7.2.1\Makefile.win" all g++.exe -D__DEBUG__ -c 7_2_1Main.cpp -o 7_2_1Main.o -I"C:/Dev-Cpp/include/c++/3.3.1" -I"C:/Dev-Cpp/include/c++/3.3.1/mingw32" -I"C:/Dev-Cpp/include/c++/3.3.1/backward" -I"C:/Dev-Cpp/lib/gcc-lib/mingw32/3.3.1/include" -I"C:/Dev-Cpp/include" -pg -g3 7_2_1Main.cpp: In instantiation of `boost::function_traits<void (*)()>': 7_2_1Main.cpp:57: instantiated from here 7_2_1Main.cpp:57: error: base class `boost::detail::function_traits_helper<void (**)()>' has incomplete type 7_2_1Main.cpp: In function `int main()': 7_2_1Main.cpp:57: error: no type named `result_type' in `struct boost::function_traits<void (*)()>' 7_2_1Main.cpp:57: error: using `typename' outside of template 7_2_1Main.cpp:57: error: ISO C++ forbids declaration of `return_type' with no type make.exe: *** [7_2_1Main.o] Error 1 Execution terminated Is he right? Is there anything particular I should had done, and I've not? TIA, --Hossein __________________________________ Do you Yahoo!? Read only the mail you want - Yahoo! Mail SpamGuard. http://promotions.yahoo.com/new_mail

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Random, Random Seed
by Hossein Haeri 25 Dec '04

25 Dec '04

Dear all, Using the following (slightly manipulated) sample code of Boost.Random, I'm always gettig the same sequence: boost::mt19937 rng; boost::uniform_int<> six(1,6); boost::variate_generator<boost::mt19937, boost::uniform_int<> > die(rng, six); for(size_t i = 0; i < 10; ++i) cout << die() << " "; I know that this is the consequence of the fact that the generators are deterministic ones, plus another fact that they start using the same seed. This behaviour, however, is not that much desirable, and I'm seaking some sort of good random seed. Any suggestions? TIA and Merry Christmas, --Hossein __________________________________ Do you Yahoo!? Yahoo! Mail - You care about security. So do we. http://promotions.yahoo.com/new_mail

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Looking for lazy if_
by Agoston Bejo 24 Dec '04

24 Dec '04

Hi! I'm looking for some "lazy" version of boost::mpl::if_. I'm not very much into MPL, so I don't really know either if such a function exists in boost or whether it can be easily constructed. Platform: VC++7.1 Thx in advance, Agoston This example shows you how it may cause problems that both "branches" of if_ get evaluated: //------------------------------------------------------------ #include <iostream> #include <vector> #include <boost/mpl/if.hpp> #include <boost/type_traits.hpp> using namespace std; using namespace boost; using namespace mpl; template<typename T> struct t_type { typedef typename if_< is_arithmetic<T>, T, typename T::value_type>::type // ERROR! type; }; int _tmain(int argc, _TCHAR* argv[]) { cout << typeid(t_type<int>::type).name() << endl; // 'int' cout << typeid(t_type<vector<double> >::type).name() << endl; // 'double' return 0; } //------------------------------------------------------------ Error message: error C2825: 'T::value_type': cannot form a qualified name see reference to class template instantiation 't_type<T>' being compiled with [ T=int ]

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Presentation and problem with uBlas.
by Le Farfadet Spatial 24 Dec '04

24 Dec '04

Hello every body out there ! Let me introduce myself : I am Yoann LE BARS and I am a fresh Boost user. I am french too, so please excuse my bad english. I have got a problem with Boost uBlas, I hope it is the good list to post about it. I have made a little exemple which show what is my problem (it compiles but I found the behaviour very strange) : http://cpp.sourceforge.net/pastebin.php?show=2439 Here is a version which works but do not satisfy me : http://cpp.sourceforge.net/pastebin.php?show=2440 Why does it not satisfy me ? Well, because I am fulling a sparse matrix with an identity matrix, the A matrix and the transposed A matrix : it is very redondant and A can be a very big matrix. That is the reason why I have make the LeastSquareMatrix class. I believe I have done something wrong in it, but what ? Best regards. Yoann LE BARS, alias Le Farfadet Spatial

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[MPL] replace_if question
by David Greene 23 Dec '04

23 Dec '04

Well, my mpl adventure continues. I'm trying to place pair members of a sequence with their keys: #include <boost/type_traits.hpp> #include <boost/mpl/pair.hpp> #include <boost/mpl/key_type.hpp> #include <boost/mpl/map.hpp> #include <boost/mpl/vector.hpp> #include <boost/mpl/replace_if.hpp> #include <boost/mpl/int.hpp> #include <iostream> #include <typeinfo> using namespace boost; using namespace boost::mpl; struct pair_base {}; template<typename Key, typename Value> struct pair_type : public pair<Key, Value>, private pair_base {}; template<typename Sequence> struct replaceit { typedef typename replace_if< Sequence, is_base_and_derived<pair_base, _>, key_type<map<>, _> >::type type; }; int main(void) { replaceit< vector< charm pair_type<int, int_<32> >, pair_type<long, int_<64> > double > >::type toprint; std::cout << typeid(toprint).name() << std::endl; return(0); }; I know this is incorrect because the pairs will be replaced by the key_type metafunction itself. If I add ::type to the end of key_type<map<>, _> the compiler complains that no ::first member exists: boost-1_32/boost/mpl/pair.hpp: In instantiation of `boost::mpl::first<mpl_::_>': replace.cc:25: instantiated from `boost::mpl::key_type_impl<boost::mpl::aux::map_tag>::apply<boost::mpl::map<mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, mpl_::_>' replace.cc:25: instantiated from `boost::mpl::key_type<boost::mpl::map<mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, mpl_::_>' replace.cc:25: instantiated from here boost-1_32/boost/mpl/pair.hpp:43: no type named `first' in `struct mpl_::_' What's the right way to do this? Furthermore, is there a better way to identify pairs in replace_if than deriving from a special class? All I can think of is writing a predicate class and specializing it for mpl::pair<U, V>. Seems like there should be an easier way. Thanks! -Dave

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Questions about boost.thread
by Kosta 23 Dec '04

23 Dec '04

Hi! I have the following questions about boost.thread: 1) Did I miss an abstraction about atomic operations, e.g. for ++, --, +=, -=, <, ==, =, ... for uint8_t, uint16_t, uint32_t, ... (something like InterlockedIncrement() on WIN32)? I know that I can Mutexes and Locks to implement the desired behavior, but I think a more lightweight solution for this basic operations should be available, too. 2) How can I change the priority of a boost::thread? 3) boost::shared_ptr<> and boost::weak_ptr<> are not thread safe, are they? What is the suggested way to write thread safe implementations of them? Kosta

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RE: [Boost-users] /clr causes __fastcall to become __stdcall-->unresolved externals for regex
by Fuqua, Andrew (ISSAtlanta) 23 Dec '04

23 Dec '04

> You'll have to modify the definition of BOOST_REGEX_CALL in > boost/regex/config.hpp so that it's __cdecl whatever the build options are > (this is what the next version will do anyway BTW). Excellent. That's easy enough. THANKS!

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semaphore
by Amerio 23 Dec '04

23 Dec '04

Hello, I'm lacking a boost semaphore, so I tried to roll my own. Being carefull with threads, I present here my version, hoping you gurus will spot any flaw. class sem { sem(unsigned count): m_count(count) {} void post() { boost::mutex::scoped_lock lock(m_mutex); ++m_count; m_cond_.notify_one(); } void wait() { boost::mutex::scoped_lock lock(m_mutex); while ( m_count==0 ) m_cond.wait( lock ); --m_count; } private: unsigned m_count; boost::mutex m_mutex; boost::condition m_cond; }; Objective : I need a semaphore to sync many readers to a single input queue. If you know another implementation or solution to this specific problem, your help is welcome. Thank you.

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Boost contents
by Foster, Gareth 23 Dec '04

23 Dec '04

Hello, Just a general interest question which came to me reading the email below. Are there any critera for what can/can't be added to boost? Somebody was telling me about ACE recently, which apprently attempts to wrap POSIX with C++. It looks like there is overlap there with Boost. Does Boost have some similar aim, to be a set of libraries covering a certain anlge, or is it litterally a collection of useful code? Would something like a GUI abstraction system be considered? Or is the limit perhaps things that could resonably make it into the STL? Hope that isn't off topic, Thanks! Gaz -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Jonathan Turkanis Sent: 23 December 2004 09:58 To: boost-users(a)lists.boost.org Subject: [Boost-users] Re: units library Dan Dimerman wrote: > Jeff Garland wrote: >> On Wed, 22 Dec 2004 15:33:18 -0700, Chris Goller wrote >> >>> I've been looking around for a unit conversion library. I've seen >>> some on http://groups.yahoo.com/group/boost/files/ but am wondering >>> if any have been put into boost release yet. >> >> >> Nope, none are in a boost release. And I think that the most active >> author has recently abandoned his effort :-( So I'm afraid you >> shouldn't expect anything soon. >> >> Jeff > Are you referring to something like this: > > boost_1_32_0/libs/mpl/doc/tutorial/dimensional-analysis.html I believe he's refering to Andy Little's pqs library. Andy announced recently that he wasn't going to propose it for review, but he didn't say why. I never looked at it. Matthias Schabel also was working on a physical quantities library in the last year or so, but I haven't heard anything recently. David and Aleksey appear to discuss dimencional anaylsis in some detail here: http://www.artima.com/cppsource/metafunctions.html, but I don't know how close this comes to a full-fledged dimensional anaylsis library. Jonathan _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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/clr causes __fastcall to become __stdcall --> unresolved externals for regex
by Fuqua, Andrew (ISSAtlanta) 23 Dec '04

23 Dec '04

I'm getting a handful of the following errors and warnings while trying to build with boost regex in MS Visual C++ .NET with the /clr option (managed extensions). boost_1_32_0\boost\regex\v4\match_results.hpp(189): warning C4561: '__fastcall' incompatible with the '/clr' option: converting to '__stdcall' error LNK2001: unresolved external symbol "public: class boost::reg_expression<char,class boost::regex_traits<char>,class std::allocator<char> > & __stdcall boost::reg_expression<char,class boost::regex_traits<char>,class std::allocator<char> >::operator=(class boost::reg_expression<char,class boost::regex_traits<char>,class std::allocator<char> > const &)" (??4?$reg_expression@DV?$regex_traits@D@boost@@V?$allocator@D@std@@@boos t@@$$FQAGAAV01@ABV01@@Z) The debug build works fine because config.hpp defines BOOST_REGEX_CALL to _cdecl. It's the release configuration that has the trouble with __fastcall being changed to __stdcall. How do I get around this (without getting rid of /clr or using a debug build)? thanks

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