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[mixin] Introducing a new library.
by Borislav Stanimirov 17 Feb '13

17 Feb '13

Hello, Boost.Mixin is a library I'm developing with the idea to someday submit it to Boost. It is an entity-component system, with full abstraction between interface and implementation. In short, users can define objects by combining components (often referred to from here on out as mixins). A mixin is a regular C++ class for which two macros are defined. The main thing however are the messages. Instead of getting the component with some function like `get_component` (which is possible but discouraged in the library), users deal with objects only. They can call messages (inspired by Smalltalk's messages) which are dynamically dispatched to the appropriate mixin. The messages (also defined with macros) are the only thing needed for a user to call methods from the object's mixins. When defining a mixin, the user tells which messages it's going to implement, and when adding this mixin to the object a virtual table of sorts is filled and the object starts responding to those messages by calling the mixin's actual C++ methods. Some of the key features are: * Multicast messages. A message that is implemented and handled by more than one mixin. See the message `trace` in the example. (As opposed to unicast messages, that are handled by a single mixin) * Object access from within the mixin. The macro `bm_this` (Boost.Mixin this). See the renderer do in the example. * "Live" object mutation by adding and removing mixins. As demonstrated in `change_rendering_system` in the example. This is done via the `object_transformer` class and is currently the only way of adding mixins to objects. * Mixin (and message) domains. The domain is a collection of mixins and messages that work together. If you create a set of mixins that will never conceivably have to exist in the same object as another set of mixins, you should use a different domain. Here is a github link to the library: http://github.com/iboB/boost.mixin A working example can be found here: http://github.com/iboB/boost.mixin/tree/master/libs/mixin/example/basic The example is nothing more than some objects and mixins working together as they would hypothetically in a simple game. All "game" code has been shortcut to text outputs like: "right now an object is being rendered by the d3d renderer". The example demonstrates most of the currently supported library features. There is no jamfile yet. I develop it with Qt Creator and Code::Blocks in Linux and MS Visual Studio Express 2008 and 2012 in Windows (the Windows projects might be somewhat outdated), so the are project files for these four in libs/mixin/build. The same goes for the example. I'd qualify the current state of the library as pre-alpha, so it might have some bugs. I also create a small performance testing project (much more is to be added). It calls a regular function, a virtual function, `std::function` and a unicast mixin message a hundred million times. So far I'm generally happy with the performance, which is not to say that I won't be working on improving it. Still my computer is the only one I've tested it on and I'd be happy if somebody else tries the perf project. Here are my results: 100,000,000 x | Debug t | Release t ------------------------------------------ regular method | 781 ms | 211 ms virtual method | 639 ms | 253 ms `std::function` | 10695 ms | 272 ms Mixin message | 3298 ms | 865 ms It should also be noted that currently the library depends on a piece of code from Don Clugston's fastdelegate (found here: http://www.codeproject.com/Articles/7150/Member-Function-Pointers-and-the-F…) The piece in question has been copy-pasted verbatim (wrapped around in the boost::mixin namespace) in the third_party subfolder. Don Clugston has done a wonderful job of creating a platform-independent representation of C++ methods as a pair of pointers. Boost.Mixin heavily relies on such a thing for its virtual tables. For now I am the only developer of the library. Zahary Karadjov (credited in the license) hasn't written anything in it yet, but he is responsible for most of the library's public interface design, the idea to reuse fastdelegate, and the ideas and implementation suggestions for many of the roadmap features listed below. The programming languages Smalltalk, Ruby, and, to a degree, Objective C have also influenced the design. So, here is a project roadmap of sorts: 1. Soon: * Overloaded messages - messages that call overloaded functions. The message's name is different for each overload but the calling function remains the same * Work on more sensible (and helpful) runtime and compile-time errors. Missing messages, ambiguous message priority, etc. * Add multicast result collectors. Like `and` or `or` for boolean return values. Like `sum` for numeric values. Sample usage some_multicast_message(obj, p1, p2, boost::mixin::sum). User-defined result collectors will be possible. * Add a new mixin feature `fact`. Facts are static const variables in a mixin. No multicasts. No virtual tables. * Add object type templates. Instead of manually transforming each object, you would be able to call `type_template::new_object()` * Add more graceful runtime error handling: default message implementations (if none is provided), more specific non-breaking exceptions * Rigorous unit tests * Performance tests * Tutorials 2. Later: * Boost.Jam build files * Full reference documentation * Formal submission to Boost?? * Call mixin constructors when mutating object or constructing them via object type templates. Sample usage: `mutate(obj).add<mixin>("foo", param2).add<other_mixin>(42)` * Reduce library memory footprint * Optional external allocators per domain. Every memory allocation should pass through them. * Make use of the fact that a BIG execution time improvement can be made if a user has no mixins or messages defined in a dynamic library (and has no plans to add such) * Integration with Boost.Serialization. As long as the mixins of an object are serializable, the object will be, too. * "Static" mixins. As long as they're not mutated in or out, it provides a faster message execution. * Reflection. Create objects with mixins by string. Call messages by string. * Object mutation injections. Automatically add some mixins when others are present. Substitute a mentioned mixin with another. Ban a mixin from being added to an object. 3. When humankind becomes a Kardashev type two civilization: * Integration with Boost.Thread. Call messages for a specific thread. * User-defined message hooks. Sample implementation with messages called on objects on another device through Boost.Asio. * A way to mutate static mixins in and out. Slight mutation execution penalty. * Some magic to make it work even faster. * Integration with Boost.Python and luabind. * Remove C++03 backward compatibility???? * Library being accepted in Boost???? I think I will be done with the items form list one by April (some of them are even semi-implemented) and with the items of list two by the end of the year (and if I have more free time maybe even sooner). As for the items in the this list... well... they are nice to think about. I do have at least some vague ideas for each of them, but then again, this is list three. Any questions, comments, and suggestions are welcome. ------ Borislav Stanimirov ------ PS: Whoa. I'm sorry this post turned out so long. I didn't expect it to.

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[Lockfree] ringbuffer
by Rich E 17 Feb '13

17 Feb '13

First off, all Boost.Lockfree tests in trunk are passing for me on clang 4.0 on OS X, hurrah! Thank you Tim for working on this for so long... I'm running through the examples now, only with the outdated documentation as a guide (more than a couple years old). I cannot find the ringbuffer container - was it renamed or removed altogether during the review period? I notice spsc_queue acts awefully like a ringbuffer, and it's implementation contains many

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Track system Connection failing
by Vicente Botet 16 Feb '13

16 Feb '13

While connecting to the Trac system https://svn.boost.org/trac/boost/newticket I'm getting svn.boost.org uses an invalid security certificate. The certificate expired on 16/02/2013 17:02. The current time is 16/02/2013 17:25. (Error code: sec_error_expired_certificate) Could others confirm this behavior? Best, Vicente -- View this message in context: http://boost.2283326.n4.nabble.com/Track-system-Connection-failing-tp464291… Sent from the Boost - Dev mailing list archive at Nabble.com.

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[array] failures in c++11 mode
by Tim Blechmann 15 Feb '13

15 Feb '13

hi, r82834 seems to break compilation of boost.array when compiled in c++11 mode: ../../../boost/array.hpp:131:9: error: body of constexpr function ‘constexpr const T& boost::array<T, N>::operator[](boost::array<T, N>::size_type) const [with T = boost::heap::detail::skew_heap_node<q_tester, false>*; long unsigned int N = 2ul; boost::array<T, N>::const_reference = boost::heap::detail::skew_heap_node<q_tester, false>* const&; boost::array<T, N>::size_type = long unsigned int]’ not a return-statement the boost.heap testsuite exposes this failure: http://www.boost.org/development/tests/trunk/developer/output/Sandia-gcc-4-… thnx, tim

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setting <cxxflags> and <linkflags> in Jamfile?
by Oliver Kowalke 14 Feb '13

14 Feb '13

Hello, if the define BOOST_USE_XYZ is given at b2/bjam command-line how can I set special compiler- and linker-flags in the Jamfile? something like this: Jamfile.v2: *project boost/abc : requirements <toolset>gcc-4.7,<defined>BOOST_USE_XYZ:<cxxflags>-fxyz <toolset>gcc-4.7,<defined>BOOST_USE_XYZ:<linkflags>"-static-libxyz" <link>static <threading>multi : source-location ../src : usage-requirements <link>shared:<define>BOOST_ABC_DYN_LINK=1 ; * if the lib is build with b2 toolset=gcc cxxflags="-DBOOST_USE_XYZ" then -fxyz static-libxyz is applied to the compiler otherwise not. How can I achieve this behaviour? best, Oliver

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Re: [boost] [smart ptr] Any interest in copy-on-write pointer for C++11?
by Andreas Pfaffenbichler 14 Feb '13

14 Feb '13

hi ralph! a heavy argument for a 'COW' pattern is made here: http://cppnow.org/session/value-semantics-and-concepts-based-polymorphism ( 'copy_on_write' class template included). maybe it could be interesting to compare your 'cow_ptr' to this 'copy_on_write'. but no doubt: the direct support of 'COW' in boost would fill e need thank you for your efforts! best regards andreas pfaffenbichler

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[gil] ToolBox uploaded
by Christian Henning 14 Feb '13

14 Feb '13

Hi all, I finally have managed to upload the "toolbox" extension for boost::gil. The toolbox provides some helpful extension for gil that are too small to be an extension themselves. There are: * color spaces: cmyka, gray_alpha, hsl, hsv, lab, xyz * metafunctions: channel_type_to_index, is_bit_aligned, is_similar, is_homogeneous, get_num_bits, channel_type, get_pixel_type, pixel_bit_size * image types: indexed_image * color converters: gray -> rgba I would need some help hooking up the tests and doc generation. Let me know if you any questions or improvements. Regards, Christian

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Relational database library (was: [GSOC] Are we going to participate?)
by Mateusz Loskot 14 Feb '13

14 Feb '13

On 14 February 2013 09:40, Roland Bock <rbock(a)eudoxos.de> wrote: > On 2013-02-14 06:04, Michael Marcin wrote: >> - relational database library (what ever happened with boost and soci?) > FYI: > I am currently working on a C++11 SQL library. Once you declare your > table structures in C++, it will allow you to express queries very close > to SQL: For example: > > TabSample t; > auto results = sql::select(sql::distinct, t.b, t.c) > .from(t) > .where(t.a > 7 and t.b != "cheesecake") > .order_by(t.c).run(db); > > for (auto row: results) > { > int a = row.a; > std::string c = row.c; > } > > The library will take care of escaping (to prevent code injection), the > compiler will enforce type safety (e.g. disallow comparison of integral > and string values). There will also be a lot of sanity checks at compile > time, for instance you cannot call .from() twice. It will even be able > to tell you, if you are referencing tables, which are missing in > .from(), etc. > > No more string concatenation and hoping to get the syntax right. The > compiler will tell you, if you do it wrong. > No more indexed access to string results. Result rows will allow you to > access individual columns by name (and they will have a decent type). > [...] Roland, It all sounds exciting. I remember the discussion long time ago we had, with similar ideas brainstormed [1], where you also asked this question, later discussed with Maciej: "Maybe it would make sense to add such a layer as an option to SOCI?" FYI, in SOCI, we're planning [2] to move SOCI towards C++11 It likely may happen during SOCI 4.0.0 release. So, I'd be interested in taking another look at this and having such layer adopted in SOCI too. Where I could learn about your solution more? [1] http://lists.boost.org/Archives/boost/2010/09/170983.php [2] https://github.com/SOCI/soci/wiki/Roadmap Best regards, -- Mateusz Loskot, http://mateusz.loskot.net

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[Git] Documentation update
by Beman Dawes 14 Feb '13

14 Feb '13

The "Git and Modular Boost" documentation has been updated: * The GitHub mothership with be github.com/boostorg * Full history for the current trunk and branches/release will be available. * There are now active milestone and issue trackers for the conversion. See https://svn.boost.org/trac/boost/wiki/WikiStart#GitandModularBoost --Beman

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adding comment to boost_1_54_0.qbk?
by Oliver Kowalke 14 Feb '13

14 Feb '13

Is it allowed to add an entry for updated libraries in public_html/live/feed/history/boost_1_54_0.qbk? Oliver

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