December 2018 - Boost - lists.preview.boost.org

CMake Announcement from Boost Steering Committee
by Jon Kalb 13 Aug '24

13 Aug '24

The libraries produced by the Boost community have had a greater impact on the way that the C++ community writes code than any other library implementation. The focus of the Boost community will always be on the libraries, but it is undeniable that we are dependent on and often limited by the infrastructure of our trade. Years ago, the move to Git was contentious; yet, it was required to improve development. In a similar vein our build system has become an impediment for many developers and users, existing and prospective. Therefore, we, the Steering Committee, announce to the Boost community our desire and intent to move Boost’s build system to CMake for users and developers alike. We are soliciting comments and proposals from the community to guide the process and the goals. Our desire is that the community can come to consensus by the end of the calendar year with a vision of supporting users and developers. We understand that the actual process of achieving the end goal will be long, time consuming, and not without its share of conflict. We also recognize that the Boost community is comprised of bright and passionate individuals that are eager to get involved and help get work done. The members of the Steering Committee have been encouraged by the discussions and activity surrounding CMake on the mailing lists over the years and know that many people have voiced visions. We hope that each of you rejoins the discussion to support this initiative and contributes to the common goal of improving Boost’s integration into the broader C++ ecosystem. For the Boost Steering Committee, Jon Kalb, Chair jonkalb(a)boost.org

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[asio][coroutine] forbid_suspend blocks
by Vinícius dos Santos Oliveira 07 Aug '19

07 Aug '19

I've implemented a dumb linter using Python + clang API that allows you to mark certain blocks as “atomic in respect to coroutines” using C++11 attributes. Usage example follows: void f() { int yield; g(yield); [[bt::forbid_suspend]] { // Comment this call to make linter accept the code g(yield); t(); } } You can change bt::forbid_suspend to another identifier by tuning settings on the beginning of the script. The prefix forbid was inspired by Rust's linters[1] as you cannot disallow the linter from inside the forbid_suspend block. Some limitations follow: - A suspend point is identified by looking references to any id equals to yield in the last argument passed to function calls. It means that yield[ignored_ec] and alike will be correctly identified, but it needs to be named yield and it needs to be the last argument to the function call. - I haven't found a way to extract attributes related to COMPOUND_STMT nodes with clang API, so I manually look for token gaps and do a simple regex. It means you cannot use macros to [[bt::forbid_suspend]] as the macro won't be expanded. - You better call the script with '-x c++' and also ' -I/usr/lib/clang/5.0.1/include'. Like I've said in the beginning of the email, it's a *dumb* linter, which means it doesn't try to handle all cases. Therefore, I don't hope to do many changes to it or maintain it to work against newer releases of clang and I'm only uploading it to gist (not fullblow Github): < https://gist.github.com/vinipsmaker2/d930fbe5b7597432b021effe618da171>. It should also be easy to hack as it is very small. I'm releasing the linter under public domain. Enjoy. I have been using fibers in a daily basis on the last months of my job to solve networking problems on a gateway project. Some of the technologies I use are: - Boost.Asio and its spawn function. - A few custom synchronization primitives for the fibers (e.g. mutex, semaphore). - Eventually I'll have to write a custom spawn function that returns a joinable handle so I can kill the usage of a fiber::barrier in a few places. I've been using the linter for about a week already and looks fine. My use case are: - To prevent iterator invalidation in regions accessing shared variables. - To guarantee events order in algorithms that handle races (cannot yield while task YYY hasn't finished). The project I use it in is not an open source project, so I cannot talk much more about it. Also, I don't claim my solution is original. I wouldn't be surprised if the very same solution exists in the wild (please let me know if you know of a similar approach). This is not a new problem. It is know for some time. For instance, in P0171, Gor Nishanov noted this same problem: “In coroutines the suspend point is clearly marked with await, which tells the reader that something unusual happens in this function and allows the reader, for example, to confirm whether the lifetimes of the objects of interest align with the lifetime of the coroutine or not, whether some locks need to be acquired to protect some concurrently accessed data, and whether some locks need to be released before the execution reaches the suspend point.” — <http://open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0171r0.html>, 2015 However, the solution he presented was to manually examine whole blocks of code without help from the compiler. I argue that the solution he presented is as error-prone as manually looking for exit paths that don't free acquired resources in languages lacking RAII. And I've been spoiled too much by RAII. Furthermore, I take this comment of his with highly suspicious look: “Since we are on the subject of maintenance nightmares, we would like to offer a conjecture that the absence of the await in P0114 is a likely source of many maintenance nightmares. Without a syntactic marker to signal to the person reading the code that something funny is going on, it is impossible to tell whether the following code is correct or not” — http://open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0171r0.html If I had to give a vote to the proposal he was defending or Chris' proposal, I'd probably have chosen Chris'. [1] https://doc.rust-lang.org/reference/attributes.html# lint-check-attributes -- Vinícius dos Santos Oliveira https://vinipsmaker.github.io/

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Non-ASCII Path Names in Repo
by Tom Kent 25 May '19

25 May '19

In the last few days we've had a non-ASCII path name added to the repo: tools/boostdep/test/utf8-test-ßµ™∃ Which came with commit 8893d1c57951a [1] I noticed this because a python 2 script (calling shutil.copytree) I had running on windows that copied the repo around started to fail. I've long needed to update that script to python 3, and am working on this. However, I wanted to point this out to the list so we could discuss if there are any other ramifications of having a non-ascii path. I vaguely remember some discussion about something like this in the past, but couldn't find it via search. If this is already a settled topic, that's great. Tom [1] https://github.com/boostorg/boostdep/commit/8893d1c57951a4a83705ed203005576…

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Re: [boost] [ Interest? ] [ out_ptr ] Tiny C++ Abstraction for C-Style Output Pointers
by Bjorn Reese 12 May '19

12 May '19

On 06/28/18 21:03, ThePhD via Boost wrote: > out_ptr is a small abstraction for making types such as > std::unique_ptr, std::shared_ptr, boost::shared_ptr, and the upcoming > std::retain_ptr > <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0468r0.html> work > work C-Style output functions as a parameter, addressing the need of > wanting to be able to do "my_c_api_init( foo, bar, &my_smart_ptr );". It's Does out_ptr have other use-cases than C interoperability?

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[thread] compiler error gcc 7.3 on cygwin
by James E. King III 06 May '19

06 May '19

Getting an internal compiler error with gcc 7.3 but only on cygwin 64-bit. Jim@pulsar /cygdrive/c/boost/libs/thread $ ../../b2 --abbreviate-paths toolset=gcc cxxstd=11 define=_POSIX_C_SOURCE=200112L define=__USE_ISOC99 threadapi=pthread address-model=64 variant=release -q ... gcc.compile.c++ ../../bin.v2/libs/thread/test/test_10963_c.test/gcc-7.3.0/rls/cxstd-11-iso/thrd-mlt/vsblt-hdn/test_10963_c.o In file included from ../../boost/thread/detail/invoker.hpp:30:0, from ../../boost/thread/future.hpp:31, from ../../libs/thread/test/test_10963.cpp:13: ../../boost/thread/detail/invoke.hpp: In function ‘decltype (*(forward<A0>)(boost::detail::invoke::a0).*boost::detail::invoke::f) boost::detail::invoke(Fp&&, A0&&) [with Fp = void (boost::executors::basic_thread_pool::*)(); A0 = boost::executors::basic_thread_pool*]’: ../../boost/thread/detail/invoke.hpp:102:43: internal compiler error: in gimplify_expr, at gimplify.c:12006 return (*boost::forward<A0>(a0)).*f; ^ Please submit a full bug report, with preprocessed source if appropriate. See <https://gcc.gnu.org/bugs/> for instructions. "g++" -std=c++11 -fvisibility-inlines-hidden -m64 -mthreads -O3 -finline-functions -Wno-inline -Wall -pedantic -fvisibility=hidden -Wextra -Wno-long-long -Wno-unused-parameter -Wunused-function -pedantic -DBOOST_ALL_NO_LIB=1 -DBOOST_THREAD_THROW_IF_PRECONDITION_NOT_SATISFIED -DNDEBUG -D_POSIX_C_SOURCE=200112L -D__USE_ISOC99 -I"../.." -c -o "../../bin.v2/libs/thread/test/test_10963_c.test/gcc-7.3.0/rls/cxstd-11-iso/thrd-mlt/vsblt-hdn/test_10963_c.o" "../../libs/thread/test/test_10963.cpp" ...failed gcc.compile.c++ ../../bin.v2/libs/thread/test/test_10963_c.test/gcc-7.3.0/rls/cxstd-11-iso/thrd-mlt/vsblt-hdn/test_10963_c.o... If I change the C++ language level to 03 the problem goes away. I also cannot reproduce it on linux with the same version of compiler (but it probably isn't the exact same compiler code). Should I go ahead and file that gcc bug? - Jim

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[test] unit test command-line handling
by Stefan Seefeld 22 Mar '19

22 Mar '19

Hello, this is a question concerning the Boost.Test framework. I'd like to pass command-line arguments to my tests, and I'm unsure of how to proceed. I have found https://www.boost.org/doc/libs/1_68_0/libs/test/doc/html/boost_test/adv_sce…, which shows how to access the command-line programmatically, but that's declared obsolete, and it's also lacking some important info, such as how I should handle the argv vector. Are there any examples that demonstrate this use case ? Specifically: * What (non-deprecated) API can I use to access command-line arguments during test initialization ? * How does my own handling of command-line arguments interact with Boost.Test's own command-line argument handling ? Thanks, Stefan -- ...ich hab' noch einen Koffer in Berlin...

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Integer sorting
by Fenil Mehta 19 Feb '19

19 Feb '19

I have written a sorting algorithm which is way faster than std::sort for all array size. The link is as follows: https://github.com/fenilgmehta/Fastest-Integer-Sort Some guidance would be appreciated on how to improve the project structure and the steps to get it included in boost. Regards, Fenil Mehta

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Regression matrix stopped updating
by Nikita Kniazev 13 Jan '19

13 Jan '19

For past month or two regression matrix update frequency was fluctuating in a big range, sometimes not updating for two-three days. As for now master is not updated for 7 days and develop for 5 days. https://www.boost.org/development/tests/master/developer/summary.html Summary: Master Report Time: Tue, 11 Dec 2018 01:44:54 +0000 https://www.boost.org/development/tests/develop/developer/summary.html Summary: Develop Report Time: Thu, 13 Dec 2018 06:05:04 +0000 Is it down for maintenance or what is going on?

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boost log to display source code name and lines
by hh h 11 Jan '19

11 Jan '19

Hi, I am looking for good log library to replace google log, my plan is to use boost log, but I am not sure if it is mature or it has been used seriously. It lacks some simple basic features such as display source code name and lines in log file, I've searched on line discussion, there are many suggestion to fix it in piece of code, but I could not get that work, difficult to use it may be overstated. Are there any good examples to display source program name and lines similar to asio socket examples on line? What is your opinion about boost log? Should I still pursue it? Thank you. - jhh

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Requesting formal review for (Boost) LEAF
by Emil Dotchevski 10 Jan '19

10 Jan '19

LEAF is a small C++11 error handling library (the acronym stands for Low-latency Error Augmentation Framework). Features: - Header-only, NO dependencies. - No dynamic memory allocations. - Associate objects of arbitrary types with any failure — when it is initially reported or at a later time. - Compatible with std::error_code, errno and any other error handling API. - Use with or without exception handling. - Support for multi-thread programming. Official documentation: https://zajo.github.io/leaf. LEAF is designed for use in low-latency environments without exception handling, but it also works with exception handling; in that case it is a better, more optimal replacement for Boost Exception. This link can be helpful for refactoring existing Boost Exception code: https://zajo.github.io/leaf/#boost_exception.

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b2 --exec-prefix=...
by Peter Dimov 09 Jan '19

09 Jan '19

Our "b2 --help" documentation says --exec-prefix=<EPREFIX> Install architecture dependent files here. Default: <PREFIX> --libdir=<LIBDIR> Install library files here. Default: <EPREFIX>/lib and bootstrap.sh also supports --exec-prefix and when given, records it in project-config.jam. But it doesn't work and has never worked. Only --prefix is honored, --exec-prefix is simply ignored. I think that we should bring the documentation and the actual behavior in sync, either by making --exec-prefix work as documented, or removing it from the documentation. Which one should we do? Comments?

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Should pass boost::asio::io_service by raw pointer or smart pointer?
by hh h 07 Jan '19

07 Jan '19

Hi, In many examples and even implementations, programmers like to pass boost::asio::io_service by raw pointer: MyClass::MyClass(boost::asio::io_service &io_service) : myRawIoService(io_service) {} Will this cause issues to pass raw pointer for large size of classes, should it be replaced by passing smart pointer: MyClass::MyClass(const std::shared_ptr<boost::asio::io_service> &io_service) : myIoService(io_service) {} Thank you.

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Re: [boost] [multi_index] problem with Travis integration
by Nikita Kniazev 31 Dec '18

31 Dec '18

Aah, you repository has both Travis enabled. Formerly Travis had two separated sites, one (.org) served for open source project and other (.com) for private projects. A while ago they opened .com for open sources and announced that they will merge .org to .com, but actually nothing changed. https://docs.travis-ci.com/user/open-source-on-travis-ci-com/ > Looking closer, there is a duplication. In commit 1af32b3, the "Travis > CI - Branch" link redirects > (indirectly) to > > https://travis-ci.com/boostorg/multi_index/builds/95957238 > > while the "continuous-integration/travis-ci/push" points to > > https://travis-ci.org/boostorg/multi_index/builds/473601408 > > Note the most surprising fact that *the first link is **to travis-ci.com > and the second **to > travis-ci.org*. These two domains don't see each other (If i try to see > 473601408 in > travis-ci.com or 95957238 in travis-ci.org I get a "we couldn't find > that build" screen). > > Joaqu?n M L?pez Mu?oz

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[multi_index] problem with Travis integration
by Joaquin M López Muñoz 30 Dec '18

30 Dec '18

Sorry to be such a noob when it comes to Travis integration, but for the life of me I just can't see how to fix the following: Travis was activated for boostorg/multi_index yesterday, and, in addition, I've been given admin privileges to boostorg/multi_index so I can, in theory, control how the Github/Travis communication happens. Evreything is working OK except that, when I push something to develop, *two* Travis tasks are created, named "Travis CI - Branch"and "continuous-integration/travis-ci/push": whereas in all the other boostorg libs I've examined, only "continuous-integration/travis-ci/push" appears (example with smart_ptr): I've walked all over the settings pages for both Travis and Github, looked up on the Internet and didn't come to any conclusion as to what this "Travis CI - Branch" thing is and how it can be turned off so that integration looks the same way as for any other Boost lib. Any clue much appreciated. Joaquín M López Muñoz

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Re: [boost] [multi_index] problem with Travis integration
by Nikita Kniazev 30 Dec '18

30 Dec '18

This might be connected to GitHub Services deprecation https://developer.github.com/changes/2018-04-25-github-services-deprecation/ https://blog.travis-ci.com/2018-09-27-deprecating-github-commit-status-api-… Sorry to be such a noob when it comes to Travis integration, but for the > life of > me I just can't see how to fix the following: > Travis was activated for boostorg/multi_index yesterday, and, in > addition, I've been given > admin privileges to boostorg/multi_index so I can, in theory, control > how the Github/Travis > communication happens. Evreything is working OK except that, when I push > something to > develop, *two* Travis tasks are created, named "Travis CI - Branch"and > "continuous-integration/travis-ci/push": > whereas in all the other boostorg libs I've examined, only > "continuous-integration/travis-ci/push" appears (example with smart_ptr): > I've walked all over the settings pages for both Travis and Github, > looked up on > the Internet and didn't come to any conclusion as to what this "Travis > CI - Branch" > thing is and how it can be turned off so that integration looks the same > way > as for any other Boost lib. > Any clue much appreciated. > Joaqu?n M L?pez Mu?oz

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[multi_index] Travis/AppVeyor activation request
by Joaquin M López Muñoz 29 Dec '18

29 Dec '18

Hi, Could some administrator with the required permissions activate Travis and AppVeyor integration for boostorg/multi_index? Thank you! Joaquín M López Muñoz

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GSOC 2019
by Amit Singh 28 Dec '18

28 Dec '18

Hi Sir/Ma'am, My name is Amit Singh and I'm 2nd year CS student. I would like extend GSoC 18 boost stats idea with few ML models and tools

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Does async_accept only access connection object raw pointer and wrapped it by shared pointer internally?
by hh h 27 Dec '18

27 Dec '18

I don't like to use raw pointer by new and delete, but the following code will be crashed by double delete, can't async_accept accept shared pointer? std::shared_ptr<session> new_session = std::make_shared<session>(io_service_, context_); acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session.get(), boost::asio::placeholders::error)); Thank you.

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[GSoC-2019] Guidance about GSoC 2019
by Karthik Kothuri 24 Dec '18

24 Dec '18

Hi, I am Karthik Kothuri, a 2nd year Computer Science and Engineering student at National Institute of Technology, Warangal. I would like to contribute to this organization in view of GSoC 2019. Any mentor is requested to guide me regarding this and tell me where to get started. I am experienced with moderate C++ and have been using it extensively for over an year for my Data Structures and Algorithms course. I also have a basic knowledge of object oriented programming which I will improve over the course of the next few months as part my college curriculum. Thanks.

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[uuid] constexpr uuid from string and ""_uuid literal
by Tobias Loew 24 Dec '18

24 Dec '18

Hi, while searching for constexpr GUID from string generators, I found https://gist.github.com/AlexBAV/b58e92d7632bae5d6f5947be455f796f . Since I still work with VS 2015, I wrote a C++11 constexpr version incl. boost-uuid generators. If there's interest adding this to boost uuid, please have a look at https://github.com/tobias-loew/constexpr-GUID-cpp-11 NB. This is not a finished version to be added to uuid. Comments and BOOST-Macros for constexpr needs to be added. Tobias -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Dev-f2600599.html

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ASIO TCP socket scalability for large scale connections
by hh h 24 Dec '18

24 Dec '18

Hi, In regard to ASIO TCP socket implementation, for each connections the server needs to open and to maintain a session, obviously there need be adequate RAM and CPU resources for supporting large connections, but does ASIO TCP socket itself has any limitation for connecting to large clients which could be over 10000 or more simultaneously? What will be the maximum connections a single ASIO TCP socket server can handle? Thank you.

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Re: [boost] Should pass boost::asio::io_service by raw pointer or smart pointer?
by Vinnie Falco 24 Dec '18

24 Dec '18

On Thu, Dec 20, 2018 at 6:45 PM Richard Hodges <hodges.r(a)gmail.com> wrote: > ...even with Vinnie's easy to follow guide, it requires a hundred lines of > boilerplate to implement what amounts to one async method. Yes, that is kind of irritating. I've been working on some tools to make it easier. The function wrap_handler returns a new completion handler which wraps your function object (lambda) and inherits the allocator and executor of another completion handler: <https://github.com/vinniefalco/beast/blob/8afbc6090bded0cdfda46871d829ea778…> The class template base_handler<> is meant as a base class for composed operations, it holds the handler for you and it provides all the hooks. I notice that you didn't include an overload for asio_handler_invoke in your example, which will certainly cause undefined behavior in some cases: <https://github.com/vinniefalco/beast/blob/8afbc6090bded0cdfda46871d829ea778…> You can see both wrap_handler and handler_base used together to implement a composed operation, a flavor of async_read_some which has a built-in timeout: <https://github.com/vinniefalco/beast/blob/8afbc6090bded0cdfda46871d829ea778…> In particular, handler_base let me leave out all of the boilerplate which is nice. It is possible that with some adaptation these utilities can be used to achieve the result you desire. These experimental features will appear in Boost.Beast version 1.70.0. Regards

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GitHub testing issues
by Cromwell Enage 22 Dec '18

22 Dec '18

Hi, everyone! Starting yesterday, I experienced failures on all my test builds. Their logs contain the following message: travis_time:end:1a83bdea:start=1545229245463720000,finish=1545229258317024000,duration=12853304000 [0Ktravis_fold:end:install.10 [0Ktravis_fold:start:install.11 [0Ktravis_time:start:04d79bf0 [0K$ ./b2 headers boost-install.jam: No such file or directory Jamroot:307: in boost-install ERROR: rule "boost-install.boost-install" unknown in module "Jamfile</Users/travis/build/CromwellEnage/boost-root>". libs/atomic/build/Jamfile.v2:38: in modules.load /Users/travis/build/CromwellEnage/boost-root/tools/build/src/build/project.jam:372: in load-jamfile /Users/travis/build/CromwellEnage/boost-root/tools/build/src/build/project.jam:64: in load /Users/travis/build/CromwellEnage/boost-root/tools/build/src/build/project.jam:89: in load-used-projects /Users/travis/build/CromwellEnage/boost-root/tools/build/src/build/project.jam:75: in load /Users/travis/build/CromwellEnage/boost-root/tools/build/src/build/project.jam:142: in project.find /Users/travis/build/CromwellEnage/boost-root/tools/build/src/build-system.jam:618: in load /Users/travis/build/CromwellEnage/boost-root/tools/build/src/kernel/modules.jam:295: in import /Users/travis/build/CromwellEnage/boost-root/tools/build/src/kernel/bootstrap.jam:139: in boost-build /Users/travis/build/CromwellEnage/boost-root/boost-build.jam:17: in module scope travis_time:end:04d79bf0:start=1545229258327432000,finish=1545229259660893000,duration=1333461000 [0K [31;1mThe command "./b2 headers" failed and exited with 1 during . [0m It's also happening on Appveyor, and just from looking at < https://github.com/boostorg/graph/pull/144>, I'm not the only one who is encountering these errors. Any help would be appreciated. Thanks! Cromwell D. Enage

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New library proposal: Autodiff
by Matt Pulver 21 Dec '18

21 Dec '18

Hello, An automatic differentiation <https://en.wikipedia.org/wiki/Automatic_differentiation> C++ library - Autodiff - is released under the Boost License and is proposed for inclusion into Boost: - Github: https://github.com/pulver/autodiff - Boost Library Incubator: http://blincubator.com/bi_library/autodiff-2/?gform_post_id=1716 Features: - Instances of autodiff variables satisfy Boost's Conceptual Requirements for Real Number Types <https://www.boost.org/doc/libs/1_69_0/libs/math/doc/html/math_toolkit/real_…>. In fact the class and function template definitions are based upon the tables in this page. - No use of dynamic memory. The only member variable is a std::array<>. - Consistent with Boost's type promotion templates. When adding/multiplying/etc. variables of differing dimension number and sizes, the resulting data type is calculated at compile-time. - Single header-only file. - Intuitive and minimal API. Requirements: - C++17 compiler that supports constexpr if statements. There are a fair amount of calculations done at compile-time which would require messy SFINAE hacks to make this C++14-compatible. Todo: - A github build matrix that also includes clang and MSVC. - Additional documentation, including the mathematics. Feedback and endorsements for Boost Library inclusion are welcome and requested. Best regards, Matt

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[parameter] Helping user libraries adjust to recent changes in GitHub develop branch
by Cromwell Enage 20 Dec '18

20 Dec '18

Hi, everyone! I've been contributing upgrades to Boost.Parameter functionality and documentation in the GitHub develop branch for the past couple of months. These upgrades include the addition of code generation macros for Boost.Parameter-enabled function call operators and support for perfect forwarding, and more upgrades are yet to come. It's been an enjoyable experience so far, but understandably there are some growing pains. I've taken pains to ensure that as long as user libraries access only the public interface of Boost.Parameter, they won't be affected by the changes. However, there are several notable libraries that currently use non-public portions of Boost.Parameter, so whenever possible I've submitted PRs to those libraries that either change the usage to access only public portions (preferred) or make quick fixes (temporary). I'm drawing off Peter Dimov's page < https://pdimov.github.io/boostdep-report/develop/parameter.html> as a guide to focus my efforts. As of this writing, I have active PRs for the following libraries: Boost.Convert Boost.Graph Boost.Lockfree I also have my eye on the following libraries, which I know have been broken by the latest changes: Boost.Accumulators Boost.Log I'm willing to help the library maintainers resolve these issues as quickly as possible. This post can serve as a discussion starting point, and I should be able to answer any questions you have about the changes to Boost.Parameter. Cromwell D. Enage

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