- Boost - lists.boost.org

Macro/Typedef for the biggest integer for template parameters
by Daryle Walker 01 Sep '07

01 Sep '07

We've talked about this problem off and on for years now, and I'm wondering if we can finally solve it. Many compilers supply built-in integer types beyond (unsigned) long int, but someone told me that there's no guarantee that those super-long types are suitable for use in a value-based template parameter. I'm wondering if we can develop typedefs, maybe in "boost/cstdint.hpp", that describe the largest suitable signed and unsigned built-in integer types that can be used as value-based template parameters. On basically-standard compilers, this would be "unsigned long" and "long". I'm thinking that we could default to boost::[u]intmax_t, and #case it for particular compilers after they choke on not being able to use "long long" or "__int64_t" in a template. (We could test in advance to minimize hardship.) -- Daryle Walker Mac, Internet, and Video Game Junkie darylew AT hotmail DOT com

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Linearizing type list creation without macros
by Marco Costalba 01 Sep '07

01 Sep '07

Form Alexandrescu "Modern C++...", a type list is defined as template<class T, class U> struct TL { typedef T head; typedef U tail; }; A lot of interesting stuff can be made with, please refer to the book for reference. A problem is the initialization, as the author says: "A Plethora of macros that transform recursion into simple enumeration..." Something like: #define TL_1(a) TL<a, NullType > #define TL_2(a,b) TL<a, TL_1(b) > #define TL_3(a,b,c) TL<a, TL_2(b,c) > #define TL_4(a,b,c,d) TL<a, TL_3(b,c,d) > #define TL_5(a,b,c,d,e) TL<a, TL_4(b,c,d,e) > #define TL_6(a,b,c,d,e,f) TL<a, TL_5(b,c,d,e,f) > So that it is possible to say: TL_3(int, double, char*) and get the corresponding type list. I think it is possible to avoid the macros: struct E {}; template<class T1 = E, class T2 = E, class T3 = E, class T4 = E, class T5 = E, class T6 = E, class T7 = E> struct TLCreator { typedef TL<T1, typename TLCreator<T2,T3,T4,T5,T6,T7,E>::MyTL> MyTL; }; template<> struct TLCreator<E, E, E, E, E, E, E> { typedef E MyTL; }; Now you can say: TLCreator<int, double, char*>::MyTL instead of using a macro. Following little drivers shows it works. First define a type list length calculator, as explained by Alexandrescu: /* type list length */ template<class TL> struct Length; template<> struct Length<E> { enum{ value = 0 }; }; template<class T, class U> struct Length<TL<T,U> > { enum{ value = 1 + Length<U>::value }; }; Then test putting in main() the following int m1 = Length< TLCreator<int>::MyTL >::value; int m2 = Length< TLCreator<int, double>::MyTL >::value; int m3 = Length< TLCreator<int, double, std::string>::MyTL >::value; int m4 = Length< TLCreator<int, double, std::string, char>::MyTL >::value; std::cout << "\n" << m1 << ", " << m2 << ", " << m3 << ", " << m4 << "\n"; And you get what you would expect! I don't know if this is a known result. But it seems very powerful, indeed you can do a lot of things following the previous schema. If it is not already known I can post more example of the use of the above "template parameters iteration" schema. Thanks for your attention Marco

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A need for a COOKBOOK
by dhruva 01 Sep '07

01 Sep '07

Hi, I am trying to get more into BOOST than what I am using currently (which is quite minimal compared to what BOOST has to offer these days) and which does not include a whole lot of new things that have got into BOOST. Are there any BOOST professionals willing to come up with a COOKBOOK for using BOOST libraries? The book "Beyond the C++ Standard Library: An Introduction to Boost" has a decent coverage but is quite dated compared to the leap BOOST library suite has seen in the recent days. As a user of BOOST, I request someone with good knowledge to come up with a COOKBOOK (like the PERL/PYTHON cookbook) for the benefit for BOOST users. It could be modeled along the PYTHON COOKBOOK. Activestate has a site to submit recipes and those are taken up, polished and edited into a nice book. with best regards, dhruva -- Dhruva Krishnamurthy Contents reflect my personal views only!

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[Boost.MPI] How to use with processes on different machines?
by Manuel Jung 01 Sep '07

01 Sep '07

Hi, I would like to know, how i can use Boost.MPI for IPC between different PCs. It is described in the introduction: "Unlike communication in threaded environments or using a shared-memory library, Boost.MPI processes can be spread across many different machines, possibly with different operating systems and underlying architectures." Is there an example, how its done? I cant find one. Or isn't implemented yet? Kind Regards Manuel Jung

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[constrained-value] additional features
by Martin Dowie 01 Sep '07

01 Sep '07

I've managed to download this now (thanks!) and I've played about with added support for floats/doubles. I'd also quite like the idea of being able to retrieve the range of a constrained value so that I can use them in other more constrained values - e.g. degrees in a circle => [0, 359] but sometimes only half a circle is appropriate [0, 179]. I'd like to be able to model this, e.g. typedef bounded_int<int, 0, 359>::type degrees_in_circle; typedef bounded_int<int, degrees_in_circle::first, 180>::type degrees_in_semicircle; That's a bit contrived but hopefully you get my drift. Ada uses 'First and 'Last to get this sort of value and I've always found these sort of attributes (or 'traits') very useful. Cheers -- Martin

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[Wave] injecting standard headers directly, without a file
by Daryle Walker 01 Sep '07

01 Sep '07

[Did I already suggest something like this?...] The Wave preprocessing tool can accept locations for a compiler's system header files. I think the C++ standard allows the standard headers to not be implemented as conventional files. I'm wondering if we can do that, as an experiment. In other words, the Wave library could have an option to inject our version of idealized renditions of the standard headers directly into the token stream, without referencing actual header files. This could catch bugs that assume certain things about actual header files that wouldn't be present in our version. Our standard headers could be in the form of a collection of functions, one for each compiler item (function, type, object, template, macro, etc.). Those functions would be passed in a level of expression (declaration in a secret __boost_std namespace, injection of declaration into the std namespace, full definition in __boost_std namespace [or no namespace for macros]) and a descriptor of the environment (bits per byte, bytes per short/int/long, 2/1-complement or sign-mag, etc.). An inclusion function for each header would call the inclusion functions for each contained item, but only up to the lowest level required. Items originally from other headers would get included if needed, but without injection into std if avoidable. (For instance, #including <iostream> would _not_ get you <istream> and <ostream> for free!) -- Daryle Walker Mac, Internet, and Video Game Junkie darylew AT hotmail DOT com

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[utility] Proposal MSVC workaround for value_initialized - Ticket #1217
by Niels Dekker - mail address until 2008-12-31 31 Aug '07

31 Aug '07

The data of the wrapper class boost::value_initialized<T> may not be initialized properly, when using Microsoft Visual C++. The problem is caused by two different compiler issues regarding value initialization. For details, please read the ticket that I submitted yesterday evening (#1217): http://svn.boost.org/trac/boost/ticket/1217 Fernando Cacciola and I developed a new version of value_init.hpp, offering a workaround. The file is attached to the ticket: http://svn.boost.org/trac/boost/attachment/ticket/1217/value_init_MSVC_work… The workaround version stores the bytes of the T object that is wrapped by value_initialized<T> as an instance of aligned_storage::type. During the construction of value_initialized<T>, it clears the bytes of T (using memset), just before constructing T itself, by placement new: std::memset(&x, 0, sizeof(x)); new (&x) T(); The workaround is enabled by defining a macro, BOOST_UTILITY_VALUE_INIT_WORKAROUND. As I never contributed to a Boost library before, what should I do in order to get this workaround reviewed, and hopefully get it into the library? Kind regards, -- Niels Dekker http://www.xs4all.nl/~nd/dekkerware Scientific programmer at LKEB, Leiden University Medical Center

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empty svn directory
by Michael Marcin 31 Aug '07

31 Aug '07

Is it possible to create a high level (probably top level) always empty directory that I can svn switch to? Switch into empty allows me to easily update and watch only the folders I care about and its a recommended practice to improve svn size and performance. http://tortoisesvn.net/node/237 Thanks, Michael Marcin

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[boostbook] development as general-purpose C++ documentation tool?
by Frank Mori Hess 31 Aug '07

31 Aug '07

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 I'm curious if anyone is working on making boostbook less boost-specific and easier to use for non-boost projects? There seems to be a niche for it, as I currently find myself using it for a non-boost library, as someone who has grown frustrated with Doxygen not quite understanding the source code correctly, and being unable to easily override its mistakes. - -- Frank -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFG2EFW5vihyNWuA4URAv3EAJ9Up6X+JGfeQfG5zRz6Eyby30qMvACfUj5D XcZ6k1T9rMtr85N8FK8jg9Y= =3EhF -----END PGP SIGNATURE-----

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[build] [docs] Can't build docs
by Andrew Sutton 31 Aug '07

31 Aug '07

Sorry, this is a repost - I forgot to specify the subject correctly. Has anybody tried building any quickbook docs lately? I updated yesterday (and again today) and found that I can't build any of the docs that I've been working on - or any of the other docs in sandbox/ doc_test. It looks like something is broken with the boostbook build instructions. This is (basically) my Jamfile. using quickbook ; xml std : std.qbk ; boostbook standalone : std : .... ; Running it, I get this: /.../boost/tools/build/v2/build/virtual-target.jam:1017: in virtual- target.register-actual-name from module virtual-target error: Duplicate name of actual target: <pbin/gcc-4.1.2/debug>std.xml error: previous virtual target { quickbook%quickbook.quickbook-to- boostbook-std.xml.XML { std.qbk.QUICKBOOK } } error: created from ./std error: another virtual target { quickbook%quickbook.quickbook-to- boostbook-std.xml.XML { std.qbk.QUICKBOOK } } error: created from ./std error: added properties: <python-debugging>off error: removed properties: none If I comment out the boostbook target, the build will actually succeed, so the problem has to be something with the boostbook - and its something that has to have changed in the last week or so.[ Anybody have any ideas? Andrew Sutton asutton(a)cs.kent.edu

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