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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 07 Mar '09

07 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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