March 2006 - Boost - lists.stage.boost.cppalliance.org

Proposed addition to the iterator library for iterating over all tuples.
by Alex Mendes da Costa 19 Jun '09

19 Jun '09

Hi folks: I quite often have to write code to do the following: Given N sequences, generate all the N-tuples s.t. the i'th element in each tuple is drawn from the i'th sequence. For example, if sequence S1 is { 1, 2, 3 } and sequence S2 is { 10, 20 }, I need to generate these tuples: (1, 10), (2, 10), (1, 20), (2, 20). I think this problem could be solved elegantly with a iterator similar to zip_iterator. I have some questions: (1) Is there already a way to do this in boost? (2) If not, would this be a worthwhile addition to the iterator library? (3) If so, could I contribute code for this, or must the existing library owners write it? (4) If so, how would I go about getting my code added? Most of the docs seem to be about submitting entire libraries, rather than extensions to existing libraries. Thanks, Alex

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[defer] - comments?
by simon meiklejohn 14 Mar '07

14 Mar '07

Anyone had a play with the defer library in the vault and want to comment on its usefulness? It clearly shares much in common with the asio Dispatcher concept but with the freedom to define more general Dispatchers. (e.g. 'Create thread per callback' and 'Dispatch Callback via Message Pump', both of which violate the specific guarantees of the asio Dispatcher concept, that the callback occur in a thread that has called asio::demuxer::run().) One potential application for defer would be in conjunction with asio, creating the thread(s) which call demuxer::run() in a succinct form. Cheers Simon

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interest in pair projection iterators?
by Lewis Hyatt 22 Dec '06

22 Dec '06

Hi All, I am in the middle of writing a large body of numerical code for data analysis and have found the boost library very useful for a number of things. I do a lot of work with std::map and with containers of std::pair objects, and one thing I've always felt annoyed with is the difficulty of interfacing a value_type of std::pair with the STL algorithms. Frequently, for instance, it is nice to represent data as a std::list< std::pair<double,double> > and then to be able to work with the first and second coordinates independently and pass them to std::accumulate() or whatever. The SGI extensions select1st() and select2nd() are somewhat useful but also non-standard, and they frequently require memory-wasting buffers to store only the first or second elements. I have a relatively simple system for solving this problem and it strikes me as the kind of quick thing that might be worth including in boost. The idea is to define a template class, template<typename Iterator> class first_iterator_t { Iterator pair_iter; public: first_iterator_t(Iterator const&); /*...*/ }; which overloads operator*() and operator->() to access the element named "first" of the object returned by Iterator::operator*(). (With something analagous for second_iterator_t.) A function named first_iterator() provides a convenient creation function a-la std::make_pair(). That's it for the most part, the class only needs to provide the required iterator interface which mostly consists of just calls to Iterator::operator functions. There is also the need to define the appropriate iterator_traits typedefs. There is a small issue of deducing whether the iterator needs to be a const iterator or not, which can be solved with partial specialization of a second template class containing nested typedefs. The end result is that something like this is now conveniently available: map<int, double> m; m[1] = 0.1; m[2]=0.2; m[5]=0.5; //prints: 1 2 5 copy(first_iterator(m.begin()), first_iterator(m.end()), ostream_iterator<int>(cout, "\t")); //prints: 0.1 0.2 0.5 copy(second_iterator(m.begin()), second_iterator(m.end()), ostream_iterator<double>(cout, "\t")); I don't see a way to do this otherwise without resorting to something like select1st(), and that also requires the use of std::transform(), which I find distasteful since the required operation is really just a simple copy. So anyway do you think this is useful enough to possibly include in boost somewhere, or is it too trivial? I have what I believe to be correct code, which could be made boost-ready with little effort. Thanks for your advice! -Lewis

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Asio, run-time polymorphism
by stas garifulin 15 Nov '06

15 Nov '06

Hello. I have some experience with http protocol and i have question/suggestion about implementing this protocol using asio library. Http/1.1 supports "protocol upgrades": during persistent connection client ot server can ask remote peer to upgrade protocol (push additional protocol(s) in protocol stack just before HTTP). After successful upgrading client can continue to send http-requests to server over new protocol stack. See "Upgrading to TLS Within HTTP/1.1" (http://www.faqs.org/rfcs/rfc2817.html) for examples. Currently asio doesn't allow me to implement this facility (to transform socket using simple transport protocol, like TCP, to SSL-socket in run-time). Another problem. HTTP/1.1 supports transfer-encoded bodies of packets, i.e. bodies transformed for transmission between sender and recipient (compressed, chunked etc.). Such transfer-encoded bodies are always chunked, splitted to chunks, each chunk have header with his size, zero sized chunk signals end of body. In some step of my program i would like to eliminate difference between plain bodies (reading/writing to socket) and transfer-encoded bodies (reading/writing to chain of filters). In other words i'm talking about some infrastructure like boost::iostreams but built on top of asio dispatcher. Async analogue of boost::iostreams which allows me to create async chains of filters in run-time. For example, it can be done with non-templated versions of functions async_read, async_write, handler parameter of this functions will have type like boost::function<void (asio::error, size_T)>. SSL class could be implemented as such async filter and would allow attaching at run-time.

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[variant, MPL] Is there a variant -> mpl sequence metafunction ?
by Jaakko Järvi 13 Nov '06

13 Nov '06

make_variant_over<Seq>::type creates a variant type from an MPL Sequence. Is there an operation that would do the opposite, create an MPL sequence from a variant? I cannot just use the type parameter list as such because the types that stand for an empty type are different in both libraries: boost::detail::variant::void_ in variant, and something else in MPL. Best, Jaakko -- Jaakko Järvi, jarvi(a)cs.tamu.edu

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[jamboost] Boost.Build V2, Milestone 10 released
by Vladimir Prus 04 Nov '06

04 Nov '06

I'm pleased to announce that the next milestone release of Boost.Build V2 is available at http://prdownloads.sourceforge.net/boost/boost-build-2.0-m10.tar.bz2 http://prdownloads.sourceforge.net/boost/boost-build-2.0-m10.zip See also http://boost.org/boost-build2/ for online docs (a copy is included in distribution). Due to large number of improvements all users are encouraged to upgrade. Changes in this release: Many toolsets were added: Intel, Metrowerks, Comeau, aCC, vacpp. Documentation was converted to BoostBook and improved. Performance was improved. - Toolsets initialization syntax is much more uniform. Compiler and linker flags can now be specified. - The algorithm for computing build properties was improved. Conditional requirements can be chained, and a number of bugs were fixed. - Specific order of properties can be specified. - The main target rules can be called from everywhere, not necessary from Jamfile. - Check for "unused sources" removed. - The <library> feature affects only linking now. - The <file> feature now works only for libraries. - Simpler syntax for "searched" libraries was added. - New <dependency> feature. Unix: The right order of static libraries on Unix is automatically computed. The <hardcode-dll-paths> feature is the default. gcc: The -fPIC option is passed when creating shared libraries. Problems with distcc were solved. Sun: It's now possible to use the sun linker (as opposed to gnu), and to compile C files. Darwin: Shared libraries are now supported. MSVC: Before resource files compilation, the setup script is invoked. Options deprecated in 8.0 are not longer used. The following bugs were fixed: - The <unit-test> rule did not handle the <library> property. - Don't add "bin" to the build directory explicitly specified by the user. - Allow <include-type> to select staged targets, even with <traverse-dependencies>off. - Includes for the form '# include <whatever>" did not work. - (Qt) Add paths to all dependent libs to uic command line, which helps if the UI files uses plugins. - Using <toolset-msvc:version>xxx in requirements was broken. - Error message printed when target can be found is much more clear. - Inline targets in sources of 'stage' did not work. - Don't produce 'independent target' warnings on Windows - (gcc) The <link-runtime>static did not work. - (gcc) Suppress warnings from the 'ar' tool on some systems. - (gcc) Don't try to set soname on NT. Developer visible changes: - Generator priorities are gone, explicit overrides are used. - 'Active' features were removed - Support for VMS paths was added. Thanks to Christopher Currie, Pedro Ferreira, Philipp Frauenfelder, Andre Hentz, Jurgen Hunold, Toon Knapen, Johan Nilsson, Alexey Pakhunov, Brock Peabody, Michael Stevens and Zbynek Winkler who contributed code to this release. - Volodya

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[Python] Slice test fails on Intel 8.1 at runtime
by Stefan Slapeta 23 Oct '06

23 Oct '06

This is not a new failure, but the failure is reported for the first time. Please could anybody have a look at it? See http://tinyurl.com/4n2fx Thanks, Stefan

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Any interests in a template library for distributed message passing and event dispatching?
by Yigong Liu 25 Sep '06

25 Sep '06

Hello All, Is there any interests in libraries for distributed message passing and event dispatching? There are many aspects involved in the design of these systems, such as choosing proper message/event id types, routing/dispatching algorithms, synchronization strategies for routing data structures and remote connection transport, etc.. Various application domains present different requirements for performance and functionalities (in embedded systems, integers or sub-int (bit-fields) are used as ids and routing is based on registration table, while in the e-commerce applications, class/structs with key attributes can be used as ids to facilitate more advanced routings). I am working on a C++ template library for generic publish/subscribe called Channel. Channel's major components (message IDs, routing algorithms...) are configurable as template parameters. As a namespace shared by peer threads, channels support publish/subscribe scope control, message filtering, and translation. Channel is used the same way as we use STL containers; by instantiating Channel template with proper id type, id trait and routing algorithms, user can create customized message passing and event dispatching facility for a particular application. More documentations and code can be found at : http://channel.sourceforge.net Right now Channel is built on top of ACE (adaptive communication environment) to gain platform independence. Besides classes related to socket connections and message marshaling, most channel classes are quite platform independent. I am refactoring the code and move the platform dependent code into a few policy classes. I would like to know is there any interests in boost for such frameworks. If so, I'll be glad to present a boostified version of the framework for a review process and use existing boost classes for platform abstractions. Thanks Yigong

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TR2 and C++0x heads up
by Beman Dawes 23 Sep '06

23 Sep '06

The C++ standards committee's Library Working Group has proposed a schedule for library changes and extensions: * October 2005: cutoff date for C++0x major library proposals * October 2006: cutoff date for library TR2 proposals * April 2007: cutoff date for C++0x library clean-up papers The usual rule-of-thumb is that new library components go in TR2, while changes to existing components go in C++0x. The LWG will consider exceptions to the rule on a case-by-case basis. The LWG is planning to issue a "Call for Proposals" with details, but in the meantime Boost developers might want to start thinking about which Boost libraries they want to propose to the LWG. Because most proposals go through one or more revisions before being accepted, it helps a proposal's chances if it reaches the committee as many meetings as possible before the final cut-off. So far there are plans to propose Boost.Threads, Boost.Filesystem, and Boost.Signals. As well as proposals for some of the more major libraries, I personally hope someone will do a sweep through Boost looking at some of the smaller utilities and helpers for a possible "Small Additions" proposal. --Beman

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[shared_Ptr] [1.34] URGENT: Outstanding HP-UX / itanium bug
by John Maddock 12 Sep '06

12 Sep '06

Folks we still haven't solved the outstanding issue summarised here: http://lists.boost.org/boost-users/2005/12/15692.php Defining BOOST_SP_USE_PTHREADS is at least a workaround. Should I apply this to Boost.Config or should the sp_counted_base.hpp logic be altered (to keep everything in one place)? Or does anyone believe they have a fix for the assembly code in time for 1.34? Thanks, John.

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