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expected/result/etc
by Michael Marcin 07 Feb '16

07 Feb '16

Some months ago there was a lot of discussion regarding Rust style return values for non-exceptional error handling. Did anything ever come of this? Is there a useable library? Apologies if I missed an announcement (I've been away for a bit).

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[gsoc16] ATTN: Project ideas deadline 19th Feb
by Niall Douglas 07 Feb '16

07 Feb '16

Tomorrow 8th February the application period for Google Summer of Code 2016 begins, and yet we have just *one* idea on the ideas page: https://svn.boost.org/trac/boost/wiki/SoC2016 We need *plenty* more if we are to be approved again this year as a Google Summer of Code org, the deadline for which is the 19th February. So if you have some project ideas and think you could mentor a student this summer, *please* consider adding a project idea to the ideas list or stepping forward with a list of Boost libraries or topics you'd be willing to mentor. Our thanks in advance. --- Boost C++ Libraries Google Summer of Code 2016 admin https://svn.boost.org/trac/boost/wiki/SoC2016

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[math] Missing constexpr statement in MPFR bindings
by Claas H. Koehler 05 Feb '16

05 Feb '16

Hi, I encountered a compiler error using gcc-5.0 with the math constants in boost 1.60.0 due to a different exception specification of math::tools::digits(): The prototype defined in math/tools/precision.hpp has a BOOST_NOEXCEPT specifier, while the implementation in math/bindings/mpfr.hpp does not have the respective specification. Adding BOOST_NOEXCEPT in math/bindings/mpfr.hpp solves the problem, i.e. compilation succeeds. I was wondering whether this is a bug or whether the error can be circumvented in another way. Regards Claas

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Is there interest in Computable Calculus?
by Alexander Lauser 05 Feb '16

05 Feb '16

Hi, An arithmetic operation produces a new function using the functions in the operands and some simple expression manipulations. if I gather it right, then what you propose is basically a Computer Algebra System (i.e., a system for manipulating reals by symbolic expressions). What specifically would the goal of the library be? Best, Alex

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updated version of safe integer library
by Robert Ramey 05 Feb '16

05 Feb '16

I've updated my safe integer library. Pointers to the most recent documentation and code can be found at www.blincubator.com . Or one can use documentation http://htmlpreview.github.io/?https://github.com/robertramey/safe_numerics/… repository: https://github.com/robertramey/safe_numerics I've resolved added more tests. added more examples and explanation of them added facilities to enforce a guarantee of zero runtime penalty added new section to the documentation of the above added more documentation regarding the library implementation. and other stuff. There is still a little more to do. But there is nothing that I know about that would prevent users from using this library right now to implement guaranteed correct integer arithmetic in their applications. Of course I'm interested any feedback and/or observations anyone want's to offer. Robert Ramey

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[iterator] Boost zip iterator
by Claas H. Koehler 05 Feb '16

05 Feb '16

First of all thanks for implementing the support of std::pair with the zip iterator in boost 1.60. While testing the feature, I noticed that it is necessary to add the following include #include <boost/fusion/adapted/std_pair.hpp> before code using the zip iterator with std::pair. Just wondering if this was intentional behaviour or if the include should happen directly in zip_iterator.hpp. Anyway, the feature works great and is a real improvement for our projects. Regards Claas

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Transferring the boost-qvm github repository to Boost
by Emil Dotchevski 03 Feb '16

03 Feb '16

Hello, Ron Garcia, one of the Boost Review Wizards, has directed me to ask the mailing list about the exact procedure for transferring the boost-qvm github repo to Boost. I believe I need to have some kind of permissions to be able to use the built-in github repo transferring mechanism. Thanks, Emil

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[Math] Statistical Distributions parent distribution class
by Clancy Emanuel 01 Feb '16

01 Feb '16

In the Statistical Distributions section of Boost.Math there is a future directions link that talks about an "any_distribution" class. Is this planned for a future release? Is anyone working on this? I came across a need for this when writing a lambda to find the pdf of a certain value of a random variable. It would be helpful for iterating over a vector of random variables whose distributions are not the same.

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Adding Metaparse to the master branch
by Abel Sinkovics 31 Jan '16

31 Jan '16

Hi, I've created a pull request to add the Metaparse tests to the Boost regression tests (#113) on the develop branch (Metaparse itself is already part of the develop branch, only the regression test integration is missing). I would like Metaparse to be added to the master branch as well. I have created pull request #112 for that. Please let me know what else is needed. Thanks, Abel

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[tools/GSoC] static code analysis?
by Oliver Kowalke 30 Jan '16

30 Jan '16

Hi, would it be possible to provide a boost-tool or maybe a boost-GSoc project that enables static code analysis for boost developers? clang-tidy ( http://clang.llvm.org/extra/clang-tidy/) could be used for this purpose. Oliver

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Re: [boost] [coroutine] x86 msvc11 stack corruption
by AVZ 29 Jan '16

29 Jan '16

Just want to share workaround which work for our company. (Fiber fix was not acceptable for that application) Debugging differences in make_fcontext between 1.53 vs 1.57, I found that in 1.53 context area is cleanned with 0, but not in 1.57. So we added explicit clear after line 100 in make_x86_64_ms_pe_masm.asm: sub rax, 0128h * ; memset context area pxor xmm0, xmm0 movaps [rax+008h], xmm0 movaps [rax+018h], xmm0 movaps [rax+028h], xmm0 movaps [rax+038h], xmm0 movaps [rax+048h], xmm0 movaps [rax+058h], xmm0 movaps [rax+068h], xmm0 movaps [rax+078h], xmm0 movaps [rax+088h], xmm0 movaps [rax+098h], xmm0 movaps [rax+0a8h], xmm0 movaps [rax+0b8h], xmm0 movaps [rax+0c8h], xmm0 movaps [rax+0d8h], xmm0 movaps [rax+0e8h], xmm0 movaps [rax+0f8h], xmm0 movaps [rax+108h], xmm0 movaps [rax+118h], xmm0 * ; third arg of make_fcontext() == address of context-function mov [rax+0118h], r8 With that we are getting same behavior as 1.53 - no crash on DLL load. Thanks, AZ -- View this message in context: http://boost.2283326.n4.nabble.com/coroutine-x86-msvc11-stack-corruption-tp… Sent from the Boost - Dev mailing list archive at Nabble.com.

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[Iterator] [PR] Fix for documentation #8010
by Nathan Wilson 29 Jan '16

29 Jan '16

Hi, As a followup to my inquiry about maintaining the Iterator Library about a month back, I wanted to create PR for a simple documentation fix. So, here it is: https://github.com/boostorg/iterator/pull/21 Please let me know if there are any thoughts and/or if I'm doing something incorrectly. Thanks! Nate

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Interest in some Algorithms
by Dean Michael Berris 29 Jan '16

29 Jan '16

Hi Boost! It’s been a while, I hope you all have been doing well. I wanted to ask whether anybody’s interested in a couple of algorithms, to be made part of the Boost.Algorithm library. One is tentatively named ‘set_inplace_difference' which has the following synopsis: template <class I1, class I2> I1 set_inplace_difference(I1 f1, I1 f2, I2 f2, I2 l2); template <class I1, class I2, class C> I1 set_inplace_difference(I1 f1, I1 f2, I2 f2, I2 l2, C comp); It’s essentially a set_difference which re-uses the storage of the range [f1, l1). It takes elements from [f1, l1) that are in [f2, l2) and moves them to [p, l1) where p is the partition point (or the new “end”). This is best used in conjunction with “erase” on vectors and/or std::deque. These algorithms return p. Another is tentatively named ‘set_inplace_intersection’ which instead of the above which does the difference, does an intersection instead. Requirements on I1 and I2 are that they are RandomAccess iterators, and that they are sorted. I haven’t figured out whether partially-sorted is a sufficient condition. I also haven’t figured out whether it would work for weaker iterator classes, but so far my implementation relies on std::lower_bound and std::upper_bound. If there’s enough interest, I can prepare a pull request after going through my employer’s open-source patching process. Looking forward to hearing your thoughts! Cheers

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C++Now 2016 Registration is Open
by Jon Kalb 28 Jan '16

28 Jan '16

Boost Developers, Registration is now open for this year¹s C++Now (put on by Boost). http://cppnow.org/2016-conference/announcements/2016/01/28/registration-is-o pen.html The conference has sold out the last three years and is expect to do say again this year. Do not put off registering. Note that session submitters should not register until they receive instructions from Marshall Clow, our conference registrar. See you in Aspen! Jon

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Interest in library for nested containers?
by Alberto Marnetto 28 Jan '16

28 Jan '16

Hello, is there interest in adding a library for nested containers (including a flattening view, a function counting the scalar elements etc.) to Boost? A working version is available at https://github.com/AlbertoMarnetto/multidim . If the concept and the interface are suitable for a submission – in particular if the requirement of a C++11 compiler is acceptable and the small number of functionalities is not a problem – I can proceed to restructure the library to meet Boost's style guidelines. Regards, Alberto Marnetto

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QuickBook generate table of references?
by Nat Goodspeed 27 Jan '16

27 Jan '16

I have a biggish document consisting of a number of different .qbk files -- big enough to make it unreasonable to start over with a different toolchain. I would like to mark up particular methods of particular classes in such a way that QuickBook will produce a consolidated list of links to those methods. I read a little about DocBook being able to generate tables of figures, etc., but between QuickBook syntax and the final output document, my mental model has a big "then a miracle occurs" cloud. Will someone please show me how this is achieved? Thank you!

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Query regarding time complexity requirements of iterators in custom container
by Soul Studios 26 Jan '16

26 Jan '16

Hi there- currently working on Colony, last version I'm working on has achieved constant-time(amortised) time-complexity for iterator operations, except for the random-access operators (+, -, +=, -=, [], >, <, >=, <=). It's not possible to make these constant-time due to the nature of the algorithms and structure of container. Ion pointed out to me that there is an obscure C++ requirement for iterators that all operations be constant-time. Given this, is it worth keeping these in Colony before submitting to Boost, or would it be best to remove them and make the iterator bidirectional-only prior? Cheers, Matt

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[serialization] Custom archive and arrays
by Bjorn Reese 23 Jan '16

23 Jan '16

I am currently adding support of C++ arrays to a custom oarchive. My archive inherits from boost::archive::detail::common_oarchive and implements save_override(), which will pass any unknown type to boost::archive::save(). This enables me to implement non-intrusive serialization. When I pass an array to boost::archive::save(), it detects that this is an array and then calls detail::save_array_type. This is where my problem starts, as the function is hardcoded to always store a prefixed array count, which is illegal in the format that my custom archive uses. Would it be possible to lift this restriction? My current workaround is to add an overload for arrays to my custom archive, i.e. template <typename T, std::size_t N> void save_override(const T (&data)[N]);

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[type_traits] Tests for implicit convertibility?
by John Maddock 22 Jan '16

22 Jan '16

Folks, I suspect we may have unintentionally backed ourselves into a corner with is_convertible/is_constructible. While trying to fix https://svn.boost.org/trac/boost/ticket/11922 I found I needed to SFINAE-out some conversion operators when the conversion already exists (as an implicit constructor in the target type). So far so easy, but consider: class Int { public: Int(const int& i) {}; Int(const Int& i) = delete; }; static_assert(is_convertible<int, Int>::value, "Ooops"); Now you would think this would pass right? But it doesn't (at least on GCC and clang), and this is true for both boost:: and std:: type_traits and appears to be an unintended side effect of the way is_convertible is defined, that a valid copy constructor is required on the target type. Of course: is_constructible<Int, int>::value is true, but that also catches explicit constructors. So... have we backed ourselves into a corner or do we still have a way to test for implicit-constructibilty that doesn't also require copy-constructibility on the target type? Thanks, John.

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test matrix messages
by Robert Ramey 22 Jan '16

22 Jan '16

I have a certain number of failures for the tests of the serialization library on the test matrix. If I go to get the messages associated with the failure, I rarely get any helpful information. Here are a couple of common cases: http://www.boost.org/development/tests/develop/developer/output/teeks99-08c… http://www.boost.org/development/tests/develop/developer/output/igaztanaga-… Can anything be done about this? Robert Ramey

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[gsoc16] Attn: We need 2016 mentors and project ideas for Boost!
by Niall Douglas 21 Jan '16

21 Jan '16

Dear Boost community, We are now within one month of the beginning of Google Summer of Code 2016! Last year's GSoC was a particularly momentus one as we witnessed the approval by the community for Boost.Hana to enter Boost - congratulations to Louis and his mentor Joel for bringing to Boost a very exciting new C++ library which pushes C++ compilers to their limits. We have also seen greatly improved retention of GSoC students in the community thanks to the improved student selection procedures introduced last year, and the fresh blood brought into Boost has been very evident on the mailing list this year. As part of filling in our application for 2016, we must supply to Google a list of potential GSoC mentors and potential GSoC projects for summer 2016 in order to be approved as an organisation this year. Therefore a lengthy page of awesome project ideas at https://svn.boost.org/trac/boost/wiki/SoC2016 before *February 8th* would be an enormous help to getting us approved again this year and bringing to Boost another US$35,000 of Google funding. If you think yourself able to mentor a student doing some work on Boost this summer, *please* consider adding a description of the proposed work item and your name to the list. Last year we had more slots awarded to us by Google than we had good combinations of student and mentor, so we had to return slots which I believe has not happened here at Boost GSoC in at least a decade. That means that your project ideas have a better chance than ever of receiving funding if you can find a good student, and that is best done by getting project ideas floated *early*. If you want to know more about mentoring a Google Summer of Code funded student work before you nominate yourself, please feel free to ask on the main Boost developers mailing list boost(a)lists.boost.org or via gsoc-admin(a)boost.org. Thank you in advance for your time. --- Boost C++ Libraries Google Summer of Code 2016 admin https://svn.boost.org/trac/boost/wiki/SoC2016

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please add safe numerics to the review queue
by Robert Ramey 21 Jan '16

21 Jan '16

Any chance I could get safe numerics added to the Boost Review queue? THe link to the incubator is here: http://rrsd.com/blincubator.com/bi_library/safe-numerics/?gform_post_id=426 documention here: http://htmlpreview.github.io/?https://github.com/robertramey/safe_numerics/… and github repo here: https://github.com/robertramey/safe_numerics Robert Ramey

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[gsoc16] Can I quickly check if the below really is the best approach?
by Niall Douglas 19 Jan '16

19 Jan '16

Dear Boost, In the prototype https://svn.boost.org/trac/boost/wiki/SoC2016 at https://goo.gl/1CQAuQ I claim "Even with all of Boost's facilities [1] and using C++ 14, this program represents the currently best available method of implementing a static constant associative map of keys to values" and you can find either the code at the link or pasted below. Can I quickly check here if that claim is true? Is there a better way than my example program? BTW by static constant associative map of keys to values I mean the thing me and Tony van Eerd were speaking about here last year and the year before, and indeed frequently at BlackBerry! Niall [1]: I believe Boost.Hana could implement a static constan associative map quite easily, but I'd be fairly sure Hana will likely be beyond most students. --- cut --- #include <initializer_list> #include <experimental/string_view> #include <map> #include <unordered_map> #include <iostream> using std::experimental::string_view; enum class weekday { sunday, monday, tuesday, wednesday, thursday, friday, saturday }; // initializer_list, pair and string_view are constexpr, so this list can be constexpr // (i.e. lives in the mind of the compiler only and has zero representation in generated code) #define STRING_VIEW(str) { str, sizeof(str)-1 } constexpr std::initializer_list<std::pair<const string_view, weekday>> string_to_weekday { { STRING_VIEW("sunday"), weekday::sunday }, { STRING_VIEW("monday"), weekday::monday }, { STRING_VIEW("tuesday"), weekday::tuesday }, { STRING_VIEW("wednesday"), weekday::wednesday }, { STRING_VIEW("thursday"), weekday::thursday }, { STRING_VIEW("friday"), weekday::friday }, { STRING_VIEW("saturday"), weekday::saturday } }; int main(void) { { // Calls malloc() at least 7 times static const std::map<string_view, weekday> to_weekday1 = string_to_weekday; std::cout << "'monday' maps to " << static_cast<int>(to_weekday1.at("monday")) << std::endl; std::cout << "'friday' maps to " << static_cast<int>(to_weekday1.at("friday")) << std::endl; // Calls free() at least 7 times } { // Calls malloc() at least 8 times static const std::unordered_map<string_view, weekday> to_weekday2 = string_to_weekday; std::cout << "'monday' maps to " << static_cast<int>(to_weekday2.at("monday")) << std::endl; std::cout << "'friday' maps to " << static_cast<int>(to_weekday2.at("friday")) << std::endl; // Calls free() at least 8 times } return 0; } -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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whatever happened to the constrained value library?
by Robert Ramey 18 Jan '16

18 Jan '16

I just stumbled upon the following announcement. http://lists.boost.org/boost-announce/2010/09/0265.php But I don't see any such library as part of boost. What's up with this? Robert Ramey

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Re: [boost] [interprocess] boost::hash - different values for the same input?
by Daniel James 17 Jan '16

17 Jan '16

I altered the subject to include interprocess, since this is relevant there. On 9 December 2015 at 20:13, trafdev <trafdev(a)mail.ru> wrote: > > As per hash_range docs > (http://www.boost.org/doc/libs/1_59_0/doc/html/hash/reference.html#boost.has…) > > "This hash function is not intended for general use, and isn't guaranteed to > be equal during separate runs of a program - so please don't use it for any > persistent storage or communication." > > As per code > (http://www.boost.org/doc/libs/1_59_0/boost/functional/hash/hash.hpp) it > uses hash_combine_impl which doesn't use any random, process_id etc values > which might change during new process launches. > > At the same time, in an example describing container usage in the shared > memory > (http://www.boost.org/doc/libs/1_59_0/doc/html/interprocess/allocators_conta…) > boost::hash is being used: > > typedef boost::unordered_map > < KeyType , MappedType > , boost::hash<KeyType> ,std::equal_to<KeyType> > , ShmemAllocator> > MyHashMap; > > My question is: is it safe to use boost::hash in a shared (persistent) > storage or it's safe only for a particular (non-pointer) types? > > In this case, boost::hash docs should be changed to mention this exceptions, > because otherwise no one could use boost::hash in a shared memory > containers. Sorry about the very slow reply. I'm afraid the answer is that it depends. The reason why I originally wrote that note was because it can generate different hash values when compiled for different platforms or architectures, e.g. a 32-bit executable might generate a different hash value to a 64-bit executable. Also, I occasionally change the algorithm in new versions of boost (and probably will in the next version). For interprocess this currently won't be an issue if all the processes are using the same executable, or using executables built with same version of boost and the same architecture, but could be a problem if that isn't the case. So maybe the Interprocess documentation needs to explain this. But there's another problem coming up. The last proposal I saw for a standard generic hash function will support randomized hash functions (such as siphash) which will only work with interprocess if they are somehow seeded identically. I'll want to support whatever is accepted to the standard (although maybe as a separate library). I'll need to catch up with how that is progressing, as I haven't kept up to date.

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