March 2009 - Boost - lists.preview.boost.org

[random] Speed up binomial and poisson distributions
by Stephan 10 Mar '09

10 Mar '09

Hi, I was wondering why the binomial distribution still isn't optimized for speed. If I look into the GSL as a comparison, they use much smarter and faster algorithms. As is, the bosst::random distributions are not usable for computational purposes to me, which is a pity since I very much like the approach using variate_generators and stuff... I would be happy to contribute some faster code, but I don't know how exactly I should proceed for that... should I contact the maintainer directly? Stephan

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[threadpool] version 22 with default pool
by k-oli＠gmx.de 09 Mar '09

09 Mar '09

I've uploaded a new version of boost-threadpool. changes: * free-function get_default_pool() returning reference to static pool< unbounded_channel< fifo > > * task has new function result() returning the internal shared_future * future-like functions removed from task * boost-threadpool not a header-only library Oliver

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[Asio] Starting/stopping chat_server externally
by Tres Spicher 09 Mar '09

09 Mar '09

Hi all, I am hoping someone who is an expert on Boost.Asio can help me by analyzing my modifications to the chat_server example. I have adjusted the example to closely resemble an application I am developing that uses the example as its inspiration. Important differences between my version and the official version include: 1) chat_room supports clearing the set of participants, and the destructor for participants closes the corresponding socket 2) chat_server supports a start and a stop operation from another thread 3) The io_service is managed by the chat_server object instead of the main function I would like to know if my usage is correct, particularly for the start/stop operations. I would like the stop operation to put the chat_server into the same state it was in on construction, so that the start operation semantics are identical whether the chat_server is newly constructed or has already been stopped. I am concerned about memory leaks or uncaught exceptions, and anything else that a seasoned user of the library would notice that I may have missed. The code can be found here: http://pastie.org/412088 Thanks in advance! Tres -- Tres Spicher Boulder Labs tres(a)boulderlabs.com

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Re: [boost] [Python] GSoC and Python 3.0 Support
by OvermindDL1 09 Mar '09

09 Mar '09

> I'm a student who has finished SWIG's Python 3.0 support in GSoC 2008. > If Boost will participate in this year's Summer of Code, I'd like to > contribute my knowledge of Python 3 migration to Boost.Python, by > implement Python 3.0 support for it. Finally the users of Boost.Python > would get 3.0 support smoothly. Is that worth for a GSoC project? Any > interesting? I would be very pleased if you did this. I had done some minor edits myself, but have no chance for a good half year at least until I could dedicate some time to it, and if you did it then you would both get paid and save me a lot of time. Do note, adding Py3k support also involves changing the python version testing in the build scripts, I already have that part done if I can find it somewhere...

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Can i do serialization on "wchar_t *"
by Selvaraj Kannan 09 Mar '09

09 Mar '09

Hi, I am getting the following error, while compile. I am using Boost 1.32 Version on Mac OS 10.5. --------- > g++ -I/usr/local/include/boost-1_32/ -L/usr/local/lib/ -lboost_wserialization Test.cpp /usr/local/include/boost-1_32/boost/serialization/access.hpp:106: error: request for member 'serialize' in 't', which is of non-class type 'wchar_t' /usr/local/include/boost-1_32/boost/serialization/access.hpp: In static member function 'static void boost::serialization::access::serialize(Archive&, T&, unsigned int) [with Archive = boost::archive::binary_wiarchive, T = wchar_t]': /usr/local/include/boost-1_32/boost/serialization/serialization.hpp:78: instantiated from 'void boost::serialization::serialize(Archive&, T&, unsigned int) [with Archive = boost::archive::binary_wiarchive, T = wchar_t]' /usr/local/include/boost-1_32/boost/serialization/serialization.hpp:121: instantiated from 'void boost::serialization::serialize_adl(Archive&, T&, unsigned int) [with Archive = boost::archive::binary_wiarchive, T = wchar_t]' /usr/local/include/boost-1_32/boost/archive/detail/iserializer.hpp:155: instantiated from 'void boost::archive::detail::iserializer<Archive, T>::load_object_data(boost::archive::detail::basic_iarchive&, void*, unsigned int) const [with Archive = boost::archive::binary_wiarchive, T = wchar_t]' Test.cpp:27: instantiated from here /usr/local/include/boost-1_32/boost/serialization/access.hpp:106: error: request for member 'serialize' in 't', which is of non-class type 'wchar_t' -------- Can someone help me solving this issue. regards S.Kannan

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[uuid] looking for source
by Michael Caisse 09 Mar '09

09 Mar '09

I was looking for the current source for the uuid library. I have found the package used in the last mini-review. Is that the latest? Thank you. michael -- ---------------------------------- Michael Caisse Object Modeling Designs www.objectmodelingdesigns.com

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Re: [boost] [math] Please give me some advice.
by Dongfei Yin 09 Mar '09

09 Mar '09

Hi, I just write some simple example in the main.cpp. now, I have an idea, what about to initialize the variable or assign before the expression. like this, variable<0> x(3.0); double x1 = (x + x * x)(); // x1 == 12 x = 4.0; double x2 = d(x + x * x, x)(); // x2 == 9 from the example, you can see that some of the expression is simplified from the output. that means the result of d(x + x, x) is 2 before running. I don't want to use variable<0>::type to define a variable, so some overload operator is needed. now, I use const_<N>() to define compile time variable, it seems not so convenient. what do you think about it. I will improve it according to your advice. BTW, I think it is easier than existing tools for automatic differentiation, right? Dongfei.

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[filesystem] Normalize
by Konstantin Litvinenko 09 Mar '09

09 Mar '09

Hi All! I have noticed that fs::path("/foo/boo/.").normalize == fs::path("/foo/boo/.") and but I expect fs::path("/foo/boo/.").normalize == fs::path("/foo/boo") without trailing dot. I there is a reason why trailing dot is not removed? Is that paths is not equivalents on some systems?

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wiki.boost.org Ancient
by Joel 09 Mar '09

09 Mar '09

Can wiki.boost.org be redirected to someplace useful? Right now it is an advertisement for crystal clear software. It is a bad advertisement since it is from 2005. Even worse, it has a link to a "boost wiki" that isn't being updated and has spam hidden away in it. It claims not to be official, but if the url is wiki.boost.org, it IS official! Thanks! Joel

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[dynamic_bitset] intersects
by vicente.botet 08 Mar '09

08 Mar '09

Hi, I want to know if two dynamic_bitsets have an element in common. Is there an efficient way to get this? dynamic_bitset<> bs1, bs2; intersetcs(bs1, bs2)? Vicente

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[Curry] generic and currying multimethod class
by Nowake 08 Mar '09

08 Mar '09

Hi, I implement curried function library and upload to Vault. http://www.boostpro.com/vault/index.php?action=downloadfile&filename=curry.… - This function object create the object that imitates curried function. you can call target function in incremental steps. # but you must regist each argument sets by hand. - This function is generic function. you can set different function object to each argument sets. - This function can also use multimethod. # but you must use holder (similar as boost::any) to hold argument. # this class act dynamic visitor for holder. - This function object is poor performance. it takes much time to execute function. Samples: ____________________________________________________________________ // target function object struct test_function { string operator()() { return "operator()()"; }; string operator()(int& a) { return "operator()(int:" + lexical_cast<string>(a) + ")"; }; string operator()(int& a, double& b) { return "operator()(int:" + lexical_cast<string>(a) + ", double:" + lexical_cast<string>(b) + ")"; }; string operator()(const int& a) { return "operator()(const int:" + lexical_cast<string>(a) + ")"; }; string operator()(const int& a, const double& b) { return "operator()(const int:" + lexical_cast<string>(a) + ", const double:" + lexical_cast<string>(b) + ")"; }; }; BOOST_AUTO_TEST_CASE(test_pod) { // setup curry // create string return curry boost::curry<string> m00; // "entry" function to each argument sets. // nullary function m00.entry(test_function()); // unary function m00.entry<int>(test_function()); // binary function m00.entry<int, double>(test_function()); // you must "entry" each const type if you use const arguments. m00.entry<const int>(test_function()); m00.entry<const int, const double>(test_function()); // execute // incremental execution BOOST_AUTO(c00, m00()); BOOST_AUTO(c01, c00(100)); BOOST_AUTO(c02, c01(100.0)); BOOST_AUTO(r00, c02()); BOOST_CHECK_EQUAL(r00, "operator()(const int:100, const double:100)"); int i(100); double d(100.0); BOOST_CHECK_EQUAL(m00()(), "operator()()"); BOOST_CHECK_EQUAL(m00()(i)(), "operator()(int:100)"); BOOST_CHECK_EQUAL(m00()(i)(d)(), "operator()(int:100, double:100)"); // const value BOOST_CHECK_EQUAL(m00()(100)(), "operator()(const int:100)"); BOOST_CHECK_EQUAL(m00()(100)(100.0)(), "operator()(const int:100, const double:100)"); // with holder object (holder is similar to boost::any) boost::holder h0(100); boost::holder h1(100.0); BOOST_CHECK_EQUAL(m00()(h0)(), "operator()(int:100)"); BOOST_CHECK_EQUAL(m00()(h0)(h1)(), "operator()(int:100, double:100)"); }; Regrads. Nowake

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[math] Please give me some advice.
by Dongfei Yin 08 Mar '09

08 Mar '09

Hi, I have upload the file to Vault, file name is "[math]AD.zip". I have VC++ 2008 and the source can work under it. Please give me some advice to improve it. Dongfei.

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Re: [boost] [Boost-users] C++03 unique_ptr emulation
by Howard Hinnant 08 Mar '09

08 Mar '09

On Mar 6, 2009, at 9:30 AM, Sergey Skorokhodov wrote: > Hi, > > Howard Hinnant wrote: >> I've put up a new version of an C++03 emulated unique_ptr here: > > <skip> > > I tried to use this implementation with MSVC 7.1 sp1 and 9.0 sp1 and > encounter ICE in the following code: Sorry I don't have MSVC 7.1 to test against. Fwiw I dropped your code (copy/paste) into g++ 4.0 and it compiled, linked and ran without any memory leak or other memory related problems. -Howard > > > <code> > > #include <cstdlib> > #include <string> > #include "unique_ptr.hpp" > > > class Base > { > protected: > explicit Base( std::string const & src ) > { > target.reset( new char[src.length() + 1] ); > memcpy( target.get(), src.c_str(), src.length() ); > target[src.length()] = '0'; > } > > explicit Base( boost::unique_ptr<char[]> src ) > : target( move(src) ) > {} > virtual ~Base() {} > > private: > boost::unique_ptr<char[]> target; > }; > > class Derived : public Base > { > public: > explicit Derived( std::string const & src ) : Base( src ) {} > explicit Derived( boost::unique_ptr<char[]> src ) > : Base( move( src ) ) {} > virtual ~Derived() {} > }; > > int main(int argc, char * argv[]) > { > char const TEXT[] = "This is a text"; > boost::unique_ptr<char[]> ptxt( new char[sizeof(TEXT)] ); > Derived drv( move( ptxt ) ); > return 0; > } > > </code> > > Here is the exact compiler output: > > 1>c:\prj\vs2005\projects\unique_tsts\unique_tst\unique_tst.cpp(21) : > fatal error C1001: An internal error has occurred in the compiler. > 1>(compiler file 'f:\dd\vctools\compiler\utc\src\p2\ehexcept.c', > line 1454) > 1> To work around this problem, try simplifying or changing the > program near the locations listed above. > 1>Please choose the Technical Support command on the Visual C++ > 1> Help menu, or open the Technical Support help file for more > information > 1>Build log was saved at "file://c:\prj\VS2005\Projects\unique_tsts > \unique_tst\Debug\BuildLog.htm" > 1>unique_tst - 1 error(s), 0 warning(s) > > Is something wrong with my code or is it a "pure" MSVC bug? > > TIA > > -- > Sergey Skorokhodov > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users

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Thoughts on make_shared and shared_from_this in a constructor
by Peter Dimov 07 Mar '09

07 Mar '09

Let's take an example make_shared overload: template< class T, class A1, class A2 > boost::shared_ptr< T > make_shared( A1 const & a1, A2 const & a2 ) { boost::shared_ptr< T > pt( static_cast< T* >( 0 ), detail::sp_ms_deleter< T >() ); detail::sp_ms_deleter< T > * pd = boost::get_deleter< detail::sp_ms_deleter< T > >( pt ); void * pv = pd->address(); // #1 ::new( pv ) T( a1, a2 ); pd->set_initialized(); T * pt2 = static_cast< T* >( pv ); boost::detail::sp_enable_shared_from_this( &pt, pt2, pt2 ); return boost::shared_ptr< T >( pt, pt2 ); } The primary problem with calling shared_from_this in a constructor is that a shared_ptr to the object does not exist yet and may never will. But, when using make_shared, at the line marked //#1 we do have a shared_ptr that owns the storage of the future object T. So we should, in principle, be able to return a copy of it from shared_from_this. Unfortunately, we can't just move the sp_enable_shared_from_this call to #1 because (a) we can't convert an yet-unconstructed T to its enable_shared_from_this base if there's virtual inheritance along the way, and (b) even if we could, we can't initialize the weak_this_ member since it's not constructed yet. I can't think of a good way to pass this shared_ptr to the enable_shared_from_this base since we have no control over T.

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Future or Property Tree?
by Ryan Gallagher 07 Mar '09

07 Mar '09

Forwarding a question that someone asked in a trac bug, "Will PropertyTree? make it into Boost 1.39.0???": https://svn.boost.org/trac/boost/ticket/1989 I guess this has to be asked at least once a year. ;-) http://thread.gmane.org/gmane.comp.lib.boost.devel/171719/ >From this thread it appears that the original author, Marcin, may no longer be available to maintain this library. Was this ever confirmed? However, a year ago Sebastian mentioned that he would be willing to support the library. I don't know if this offer is still good, but it seems that we should figure out what we're doing with this library. There was a list of items in the following thread about what Marcin felt should be done before the release: http://thread.gmane.org/gmane.comp.lib.boost.devel/171825/ In that thread Marcin wrote: """ IMO the issues that should be addressed before release are: - Simplification by removing some of the template arguments (arguable - maybe someone is using that?) - Figure out which parsers are unneccessary and get rid of them (cmdline parser?) - Get some docs toolchain to work properly and provide up-to-date docs. Lots of the text can be ported over (and my monkey english corrected from the original docs. - Speedup through use of a custom container (to replace std::list, needs some profiling work if it's even worth it) """ I believe that some of the parsers were already removed from svn. In the first link I posted (the trac ticket) were some patches I gave a long time back for the docs in quickbook form + doxygen. However, these were just meant to be a start based upon the original documentation (with a few English grammar corrections) and aren't really release-ready quite yet. (I'd have to see about getting the doc toolchain setup again myself, which I don't remember working so well on Windows, though Linux didn't give me any major problems.) On top of this list, at this point I think there would may be a few patches to review and apply from Trac. Do we have a committed maintainer? Can we make any plan of action for making this library release-ready or are we giving up on it? -Ryan

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[optional] little addition
by Arno Schödl 07 Mar '09

07 Mar '09

I just started using boost::optional, and this proved to be generically useful, but I believe is currently not in boost::optional: template< class T, class Tcompatible > bool optional_assign( T& t, boost::optional<Tcompatible> const& optt ) { if( optt ) { t=*optt; return true; } else { return false; } } so you can write boost::optional< TMyValue > TryToGetT(); T t; if( !optional_assign( t, TryToGetT () ) { ... other way to get t ... } instead of the more verbose: boost::optional< TMyValue > TryToGetT(); T t; boost::optional< TMyValue > const& optt=TryToGetT(); if( optt ) { t=*optt; } else { ... other way to get t ... } get_optional_value_or is similar, but the alternative must be an expression and is eagerly evaluated, both of which may be undesirable. Arno -- Dr. Arno Schoedl · aschoedl(a)think-cell.com Technical Director think-cell Software GmbH · Invalidenstr. 34 · 10115 Berlin, Germany http://www.think-cell.com · phone +49-30-666473-10 · toll-free (US) +1-800-891-8091 Directors: Dr. Markus Hannebauer, Dr. Arno Schoedl · Amtsgericht Charlottenburg, HRB 85229

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[1.38.0] PDF package of Boost documentation released.
by John Maddock 07 Mar '09

07 Mar '09

Folks, A package containing PDF versions of Boost's documentation is now available for Boost-1.38.0 from the usual sourceforge download site: http://sourceforge.net/project/showfiles.php?group_id=7586&package_id=15971… Please note that due to the diverse range of tools in use within Boost it has not been possible to produce PDF's for all of Boost's libraries, those currently included as PDF's are: accumulators any array asio bimap range complex-tr1 concepts config conversion date_time foreach function hash interprocess intrusive iterator math-gcd math mpi octonion optional phoenix program_options proto python_tutorial quaternion ref regex scope_exit signals static_assert string_algo thread tr1 tribool type_traits typeof units unordered variant xpressive Documentation for the following tools are also included in this package: bjam boost_build boostbook quickbook Regards, John Maddock.

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[serialization] Text/Binary archive Is there a bug?
by Kasra 07 Mar '09

07 Mar '09

Hi guys, I was working withe boost.serialization and found a peculiar problem: when I use a binary archive I successfully serialize the objects but fail to deserialize them, while with text archive both of the operations occur without a problem!! Is there a special note about binary archives that I haven't done or could this be a bug? -- Kasra

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Formal Review: Boost.RangeEx
by Thorsten Ottosen 06 Mar '09

06 Mar '09

Dear Developers and Users, It's my pleasure to announce that the review of Neil Groves' RangeEx library starts today and lasts until March 3, 2009. What is it? +++++++++++ The library provide two very useful extensions to the range library 1. Range-based algorithms. E.g. boost::sort( rng ); which is a convenient wrapper of instead of std::sort( boost::begin(rng), boost::end(rng) ); But the new interface also allows for more expressive code because (on the fly) composition of algorithms suddenly is possible. 2. Range adaptors. E.g. std::vector<int> vec = ...; boost::copy( vec | boost::adaptors::reversed, std::ostream_iterator<int>( std::cout ) ); where the expression "vec | boost::adaptors::reversed" wraps the iterators of the range on the left in reverse iterators. The library provides a wide range (no pun intended) of Range adaptors, and they are a powerful way to create ranges on the fly and pass them to algorithms. Getting the library +++++++++++++++++++ The library may be downloaded from http://www.cs.aau.dk/~nesotto/boost/range_ex.zip or from the Boost vault under "Algorithms". The docs may be browsed online here http://www.cs.aau.dk/~nesotto/boost/libs/range/ Please note that the documentation is integrated with the current Range ilbrary. Therefore the relevant sections for the review is http://www.cs.aau.dk/~nesotto/boost/libs/range/doc/adaptors.html and http://www.cs.aau.dk/~nesotto/boost/libs/range/doc/algorithms.html The code may be browsed here: http://www.cs.aau.dk/~nesotto/boost/boost/range/ Notice the library is header only (exception: the adaptor tokenized() depends on Boost.Regex). Writing a review ++++++++++++++++ If you feel this is an interesting library, then please submit your review to the developer list (preferably), or to the review manager. Here are some questions you might want to answer in your review: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick - reading? In-depth study? - Are you knowledgeable about the problem domain? And finally, every review should answer this question: - Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. Special considerations ++++++++++++++++++++++ Various RangeEx like libraries have been implemented in the past. You might want to compare with those libraries when you form your oppinion: 1. John Torjo's range lib http://rangelib.synesis.com.au/libs/boost-rangelib-20040913.zip http://torjo.com/rangelib/index.html 2. Adobe's ASL libraries include range-based algorithms: http://stlab.adobe.com/group__algorithm.html I'm looking forward to your review. best regards Thorsten, Review Manager

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Re: [boost] [math] Does any one interesting in calculating derivative for a expression automatically?
by Brandon Kohn 06 Mar '09

06 Mar '09

-------------------------------------------------- From: "Dongfei Yin" <yin.dongfei(a)gmail.com> Sent: Friday, March 06, 2009 8:04 AM To: <boost(a)lists.boost.org> Subject: Re: [boost] [math] Does any one interesting in calculating derivative for a expression automatically? > You know, there are too many functions in math, so I think I can't > implement all of them, the functions included in standard library is > enough for me. and I will make it easy to be extended. what do you think > about it, I mean how many functions should I implement. > My advice would be to make the interface for supporting math functions extensible and held at arms length. The std math functions like pow, sin etc are generally working only with native types. There are those among us that use things like GMP or rational number libraries with unlimited precision for our numerical types. In these cases we have either defined our own trig or transcendental functions or had them supplied with a 3rd party lib. It would be nice to be able to generate derivative expressions which then may be applied to these types and with the use of our specialized math functions. Hope this helps, With regards, Brandon

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Re: [boost] [math] Does any one interesting in calculating derivative for a expression automatically?
by Dongfei Yin 06 Mar '09

06 Mar '09

Hi Chris, The basic theory is same, but to do it at compile time, it can not be as simple as run time. CppAD do it during run time. type in run time is not so important as compile time. It can be done not only by operator overloading, but also by template specializing. As I say, when you get d(_x * _x, _x), that is a functor, then you want d(d(_x * _x, _x), _x), you see that there is no chance for operator to do anything, that means the result of d(_x * _x, _x) should be simplified before d(d(_x * _x, _x), _x) by template secializeing. Another example, Define hypersphere<N> as (pi^(N/2)*r^N) / gamma(N/2 + 1), suppose N is known at compile time,if all the type are under control, think about (double_<pi>^(int_<N>/2)*var(r)^int_<N> / gamma(int_<N)>/2 + 1), all the type can be controlled, then N/2 can be calculated during compile time. by if just using operator overloading, it can only be done during run time. you can not overload operator+(int, int) (just a example, actually, it can be optimized by compiler automatically). Dongfei. > While not strictly the same, there are all sorts of C++ based packages > out there for doing this kind of thing. The approach taken is > 'automatic differentiation', and it basically works by applying the > chain rule to every individual step in a sequence of operations. One > approach to doing this is through operator overloading, and replacing > the underlying 'double' class with something that maintains the > appropriate state. There are already some nice open source packages out > there for doing this. More info: > > http://en.wikipedia.org/wiki/Automatic_differentiation > http://www.autodiff.org/ > http://www.coin-or.org/CppAD/ > > Cheers, > > Chris >

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Re: [boost] [math] Does any one interesting in calculating derivative for a expression automatically?
by Dongfei Yin 06 Mar '09

06 Mar '09

Hi Bruno, Till now, it can only work with polynomial and trigonometric functions. and I have a good idea of simplifying a expression. as you said, if N is compile time known, it should be int_<N>, then the expression with it can be simplified. As the hypersphere talked before, if N=2, and the volume expression will be simplified from (int_<N>^(int_<N>/int_<2>)*var(r)^int_<N>) / gamma(int_<N>/int_<2> + int_<1>) to int_<pi>*var(r)^int_<2> if gamma() has been specialized. Till now, (_x*_x*_x) is a functor, it can be simplified to something like pow(_x, int_<3>). without using d(...), it can be used to simplify expression as we talked before. this is another use of it. You know, there are too many functions in math, so I think I can't implement all of them, the functions included in standard library is enough for me. and I will make it easy to be extended. what do you think about it, I mean how many functions should I implement. My main purpose is calculating derivative easily, of course simplify expression is a important part, I am working on it. Dongfei.

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Boost package maintenance for Cygwin
by bnv＠nc.rr.com 06 Mar '09

06 Mar '09

I make use of Boost in a Cygwin environment and was happy to see it supported as a package. Unfortunately, the current package is based on 1.33.1 and there have been many updates since. The maintainer has indicated difficulty working with the Boost distribution (see below, from the main cygwin mailing list), and has stopped supporting the package. I'm not the right person to take it over, but have an interest in seeing it maintained, and thought it worth bringing this to the attention of the boost community to potentially look into the issue(s). Thanks, Brian > I have given up on Boost package on Cygwin. Boost build AFAIK does not > follow the naming conventions Cygwin has for DLLs (or did not the last > time I checked) and I do not have the willpower to hack it into submission. > > If you feel like taking over the Cygwin Boost package, try Boost Cygport > as starting point for a new Cygwin package. > > - -- > wilx

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Re: [boost] [math] Does any one interesting in calculating derivative for a expression automatically?
by Dongfei Yin 06 Mar '09

06 Mar '09

Hi Joel, I it is easy to map it onto d<N>(f,v), but I think it is difficult to be optimized for N=1, 2, 3 ... because to calculate the derivative of d<5>(f,v), actually, d<1>, d<2> ... d<5> will be calculated . but after each derivative is calculated, it will be simplified before next step. now the result of derivative expression can be saved as a functor, so d(d(x*x,x),x), y = d(x*x,x); d(y,x); is one of my purpose. I will implement d<N>(...), that is a good idea and convenience, thank you. Dongfei. > Can't this be mapped onto a d<N>(f,v) function that is optimized for N = > 1,2,3,... ? > I bet that if you use proto, matching d(d(d( ... )))) and repalcing by > d<N>(...) should be easy. > > Do you perform your derivation recursively on the derivative degree (ie > d(d(x*x,x),x) is y = d(x*x,x); d(y,x);) > If yes, you may want to use coarser grain. Let's say you specialized d() > d<2>() and d<3>() for ex. Computing d<5> > is d<2>(d<3>()) instead of d(d(d(d(d()))). Of course, using d,d2, d4 is > maybe a better option so you cna use bit representaiton of derivative > degree to find how to combine the derivative. >

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An analogue of boost.function with multiple signatures
by Ji�� Pale�ek 06 Mar '09

06 Mar '09

Hello, I'd like to have an object similar to boost::function, but with multiple function signatures. Eg. something like that multifunction<std::string(std::string), float(float), unsigned(unsigned)> mf; mf=_1 + _1; // I mean boost::lambda::_1 mf("ab"); // should be "abab" mf((UINT_MAX/2)+1); // should be 0 mf((UINT_MAX/2)+1.0); // should be UINT_MAX+1.0 Would it be possible/feasible to change boost::function to allow this (as opposed to implementing it separately from boost::function)? Was something like this even proposed before (I vaguely recall something, but couldn't google anything useful, so I may be wrong)? Regards Jiri Palecek

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