November 2012 - Boost - lists.preview.boost.org

[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 I'm running through the examples now, only with the outdated documentation as a guide (more than a couple years old).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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[fixed_point] Request for interest in a binary fixed point library
by Vicente J. Botet Escriba 02 Feb '13

02 Feb '13

Hi, the recent discussion on the MultiplePrecission Arithmetic library has show that some people has its ow fixed point library. Is there an interest in a Boost library having as base http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3352.html? I have started a prototype http://svn.boost.org/svn/boost/sandbox/fixed_point (there is no doc yet but the basic goal is quite close to the N3352 C++ proposal). This prototype should allow you to play a little bit with. If yes, what would you like to be changed, added or improved in n3352? Next follows some design decisions that IMO need to be decided before hand. * Should integers and reals be represented by separated classes? * Should signed and unsigned be represented by separated classes? * Should the library use a specific representation for signed numbers (separated sign, 2-complement? Let the user choose? * Should the library provide arbitrary range and resolution and allocators? * Should the library be open to overflow and rounding or just implement some of the possible policies? and in this case which ones? * Should fixed_point be convertible to/from integer/float/double? * Could the result of an arithmetic operation have more range and resolution than his arguments? * Is there a need for a specific I/O? * is there a need for radix other than 2 (binary)? * Should the library implement the basic functions, or should it imperatively implement the C++11 math functions? Could a first version just forward to the c++11 math functions? * Should the library support just one of the know ways to name a fixed-point, a U(a,b), nQm, ...? Provide some ways to move from one to another? * Could expect the same/better performances respect to hand written code? * What should be the size used by a fixed_point instance? _fast? _least? Should the user be able to decide which approach is better for his needs? * Which should be the namespace? boost? boost/fixed_point? boost/binary_fixed_point? boost/bfp? ... * others you can think of. Please, replay if you are interested, have some experience in the domain, good ideas, .. Best regards, Vicente

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[variant] Basic rvalue and C++11 features support
by Antony Polukhin 20 Jan '13

20 Jan '13

Hi, There is a patch in ticket #7620 that adds some rvalue assignment operators and rvalue constructors for Boost.Variant library. I saw no activity from authors of Boost.Variant Eric Friedman and Itay Maman for a long time, so if there will be no objections, I'll commit patch to trunk in the middle of November. Any suggestions and comments are welcomed. -- Best regards, Antony Polukhin

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Changes to VS 2012 config
by Marshall Clow 17 Jan '13

17 Jan '13

Just so people know - I'm updating the Visual Studio configuration to more accurately reflect the capabilities of VS 2012. The first step was in http://svn.boost.org/trac/boost/changeset/81613 ; the next step will be to update the compiler features. If you see any problems, please let me know. -- Marshall

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[parameter] std proposal
by Lorenzo Caminiti 07 Jan '13

07 Jan '13

Hello all, Is there a C++ standard proposal for named parameter addition? I am looking for an "N-paper" for named parameters similar to N2081 for concepts, or N1962 for contracts. Thank you. -- Sent from my mobile device Lorenzo

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[Range] Proposal: a sub-maintainer of Boost.Range
by Michel Morin 05 Jan '13

05 Jan '13

Dear Neil, Dear Nate, First I'd like to say thank you for your library, Neil. It is a very useful library and it's great fun to writing codes with range adaptors. Boost.Range is one of the most important Boost libraries that are not yet added to the Standard. I know that Neil has made an effort to make time for developing the library, but recently making time for development seems difficult. And there are several open tickets of trivial bugs (e.g. #5603, #6110). Considering this situation, I'd like to make a proposal about Boost.Range: ** Adding a sub-maintainer to Boost.Range ** This reduces author's maintenance burden and also helps more stable development of the library. I recommend Nathan Ridge as a sub-maintainer of Boost.Range. His knowledge, experiences and contribution to Boost are great. If both of Neil and Nate accept the proposal, and if Nate needs some support for the start-up, I'll try my best to support him. I also believe that Jeff will also support him ;) Neil, what do you think about this proposal? I would appreciate and respect any of your reply. Yours sincerely, Michel

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[config] Proposed BOOST_NOEXCEPT_NOTHROW macro
by Beman Dawes 03 Jan '13

03 Jan '13

The three current BOOST_NOEXCEPT* macro variants miss the case where C++03 code has a "throw()" throw-specifier. Classes that derive from standard library exceptions need this to avoid breaking code on C++03 compilers. I'm not enamored with the BOOST_NOEXCEPT_NOTHROW name, so feel free to offer suggestions for alternate names. Here is the full set of macros: #ifdef BOOST_NO_NOEXCEPT # define BOOST_NOEXCEPT # define BOOST_NOEXCEPT_NOTHROW throw() <---- new macro # define BOOST_NOEXCEPT_IF(Predicate) # define BOOST_NOEXCEPT_EXPR(Expression) false #else # define BOOST_NOEXCEPT noexcept # define BOOST_NOEXCEPT_NOTHROW noexcept <---- new macro # define BOOST_NOEXCEPT_IF(Predicate) noexcept((Predicate)) # define BOOST_NOEXCEPT_EXPR(Expression) noexcept((Expression)) #endif Unless there are objections, I'll commit the changes Wednesday afternoon Eastern US time. --Beman

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Re: [boost] Heads up - string_ref landing
by Yanchenko Maxim 19 Dec '12

19 Dec '12

Marshall. low <mclow.lists. at> gmail.com> writes: > Please let me know what you think! As probably everyone, we have our own device for this. Here are some points and experience we gathered. 1. This class is essentially just an iterator_ range<char*> (modulo template for const/wchar_t), so it should either inherit from it or have corresponding converting ctors/operators. In this sense Olaf/Gennadiy's remarks are pretty valid. OTOH size is needed very frequently and having it precomputed is a good thing, so conversion approach seems to be better (but then we lose passing by reference as iterator_range, type_traits etc). I'm not sure what's more important. 2. Given the above, the name is misleading as it's not a reference to std::string. We use name char_range. 3. It's worth having a static constructor 'literal' (templated with size) to construct char_ranges from literals - as the compiler knows their size in compile time (minus zero terminator). It can be a constexpr too. Same manner - static function 'from_array', embrasing an array of chars in whole, assuming there is no zero terminator - useful for working with structures representing messages in char-based protocols with fixed-width fields. 4. (hack) We had to add a member function 'assign' (this is just operator=) to make boost::tokenizer return char_ranges. I don't like this part at all as it contradicts the meaning of say std::vector::assign, so I'd prefer another solution, probably in form of a customization point in boost::tokenizer. Thanks, Maxim

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[graph] A* search applied to knight's tour
by Dave Abrahams 15 Dec '12

15 Dec '12

Hi, I was just trying to work up an example for a class I'm teaching, to illustrate implicit graphs. The following shows how far I've gotten: https://gist.github.com/4153918 This is attempting to apply Warnsdorff's heuristic (choose the next move with the least out-degree) using A* search. I'm running into several problems having to do with the requirements of astar_search_no_init. In particular, the requirement that we can assign an index to every vertex is quite painful, since enumerating all the possible vertices in the search space is difficult. Any advice here? I suppose I could keep a real map and simply assign indices in the order vertices are encountered, but that seems pretty ugly to me. Any hints? -- Dave Abrahams BoostPro Computing Software Development Training http://www.boostpro.com Clang/LLVM/EDG Compilers C++ Boost

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[Interprocess] Experimental Win32 Mutexes
by Brink, Robert (GE Aviation, US) 13 Dec '12

13 Dec '12

I'm running Boost 1.52 on Windows 7, Visual Studio 2010. I noticed in sync\interprocess_mutex.hpp there is a windows mutex implementation that is hidden behind the BOOST_INTERPROCESS_FORCE_GENERIC_EMULATION macro. The comment indicates that it is "Experimental". Could someone shed some light on what is Experimental about it and what the general plans for this feature are? I was having a problem with many processes all spin-locking when allocating shared memory that I traced down to the old mutex implementation for shared memory. I enabled the experimental feature in my local build ( by commenting out the above macro in the detail\workaround.hpp file) and it seems to fix my problems. My performance is much improved. But what are my risks for using this implementation? I'm a little nervous to depend on something marked as "Experimental". Thanks Rob Brink

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