January 2025 - Boost - lists.boost.org

Adding optional<T&> find like method to associative containers in boost.
by Ivan Matek 18 Jul '25

18 Jul '25

Hi everybody, I presume somebody thought of this before but for some reason it never happened, but just in case it was never discussed I wonder if people here believe adding an nicer version of find(with different name obviously) to associative containers in boost would be beneficial? Since boost::optional allows references this would work. I presume naming is what most people will have strong feeling about. I personally prefer ofind/oat since I love short names, Barry suggested different names in his blog <https://brevzin.github.io/c++/2023/05/23/map-api/>, e.g. try_at. boost::optional did not get all the updates C++23 std::optional got, e.g. transform that make this usage compose nicely, but those could be added to boost::optional.

13 85

[review] [sqlite]
by Richard Hodges 29 Jun '25

29 Jun '25

Dear All, Surprise! The Boost formal review of the Boost SQLITE library starts *TODAY*, taking place from November 13th, 2024 to November 22nd, 2024 (inclusive). I apologise profusely for springing this on you without prior warning. The error is entirely mine. I am extending the period by one day to compensate. The library is authored by Klemens Morgenstern (@klemens-morgenstern in the CppLang slack). Documentation: https://klemens.dev/sqlite/ <https://anarthal.github.io/mysql/index.html> Source: https://github.com/klemens-morgenstern/sqlite <https://github.com/anarthal/mysql/> >From the documentation: boost.sqlite is a simple to use C++ sqlite library. It provides a modern interface using facilities like error_code, views (e.g. for blobs) and the ability to use boost.describe or boost.pfr for parameterised queries. Supported features include: - typed queries - prepared statements - json support - custom functions (scalar, aggregate, windows) - event hooks - virtual tables SQLite provides an excellent C-API, so this library does not attempt to hide, but to augment it. Please provide in your review information you think is valuable to explain your choice to ACCEPT or REJECT including SQLITE as a Boost library. Please be explicit about your decision (ACCEPT or REJECT). Some other questions you might want to consider answering: - Will the library bring additional out-of-the-box utility to Boost? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - Will the choice of API abstraction model ease the development of software that must talk to a SQLITE database? - Are there any immediate improvements that could be made after acceptance, if acceptance should happen? - Did you try to use the library? With which compiler(s)? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? More information about the Boost Formal Review Process can be found at: http://www.boost.org/community/reviews.html The review is open to anyone who is prepared to put in the work of evaluating and reviewing the library. Prior experience in contributing to Boost reviews is not a requirement. Thank you for your efforts in the Boost community. They are very much appreciated. Richard Hodges - review manager of the proposed Boost.SQLITE library Klemens is often available on CppLang Slack and of course by email should you require any clarification not covered by the documentation, as am I.

19 67

Pretty printer module
by Дмитрий Архипов 14 Apr '25

14 Apr '25

Recently Niall Douglas posted about his idea to embed GDB pretty printers into binaries using a header. At the time I was thinking about a good way to deploy pretty printers for JSON that facilitates their autoloading. After Niall's post I experimented a little bit more, and I came to the conclusion that indeed nothing beats embedding via a C++ header in terms of convenience. At the same time I was also thinking about testing that pretty printers do in fact work. Given that pretty printers (usually) are implemented as a Python module, it initially looked like one could just run a Python program and import GDB Python modules. But actually you cannot. It turns out, though, you can run a Python script with GDB as the interpreter. After several iterations I arrived at this setup: https://github.com/boostorg/json/blob/develop/test/printers.cpp. A script converts this file into a Python script that uses GDB to break on certain lines and check if a particular expression produces a particular output when printed. While doing all this I thought that most of this work can be useful to other libraries. So, I moved the reusable parts into a separate directory (https://github.com/boostorg/json/tree/develop/pretty_printers) and added both a b2 module, and a CMake module. For B2. Importing: https://github.com/boostorg/json/blob/develop/build.jam#L8-L9 https://github.com/boostorg/json/blob/develop/build/Jamfile#L13 (Re)generating the header: https://github.com/boostorg/json/blob/develop/build/Jamfile#L88-L95 Testing: https://github.com/boostorg/json/blob/develop/test/Jamfile#L96-L101 For CMake: Importing: https://github.com/boostorg/json/blob/develop/CMakeLists.txt#L54-L55 (Re)generating the header: https://github.com/boostorg/json/blob/develop/CMakeLists.txt#L56-L63 Testing: https://github.com/boostorg/json/blob/develop/test/CMakeLists.txt#L80-L88 My questions to the community: do you find this useful? Would you use it in your Boost or non-Boost library? If you do, the module should be moved to tools rather than stay in libs/json.

12 26

asio::strand: Order of execution
by Georg Gast 11 Feb '25

11 Feb '25

Hi, If I use a asio::strand and post() there multiple function objects, are they executed in the same order or is the order of execution not specified? I think to use it as a work queue but I need them to be processed in sequence... Thx Georg

5 9

Decimal: Formal review begins.
by John Maddock 31 Jan '25

31 Jan '25

The review of the proposed Decimal Number library by Matt Borland and Chris Kormanyos begins today and runs until 22nd Jan. You will find documentation here: https://cppalliance.org/decimal/decimal.html And the code repository is here: https://github.com/cppalliance/decimal/ Boost.Decimal is an implementation of IEEE 754 <https://standards.ieee.org/ieee/754/6210/> and ISO/IEC DTR 24733 <https://www.open-std.org/JTC1/SC22/WG21/docs/papers/2009/n2849.pdf> Decimal Floating Point numbers. The library is header-only, has no dependencies, and requires C++14. Please provide feedback on the following general topics: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? Do you already use it in industry? - Did you try to use the library? With which compiler(s)? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? Ensure to explicitly include with your review: ACCEPT, REJECT, or CONDITIONAL ACCEPT (with acceptance conditions).header-only, has no dependencies, and requires C++14. Best, John Maddock (review manager).

18 94

Author assistance for WG21 display content
by Robert Beeston 30 Jan '25

30 Jan '25

Hello everyone, My name is Rob Beeston, and I’m the Product and Creative Director for C++ Alliance. I’m currently making arrangements for the upcoming WG21 event, and could use some help from some of the authors. We will be making posters, similar to this mockup ( https://downloads.cppalliance.org/images/boost-poster.png) to highlight the following libraries at the event: Hash2 Math Parser Scope Unordered Each poster would need a brief description, a longer explanation (perhaps 1-2 short paragraphs of what it does and/or how it works) and a code snippet that would best represent how to use it. Thanks and I’m looking forward to working with you. Rob

4 6

Interest for C++20 modules support of boost officially
by Chuanqi Xu 29 Jan '25

29 Jan '25

Hi Boost Developers, I am Chuanqi Xu, the maintainer for modules & serialization in clang and also a fan of C++20 modules. The post itself was motivated by a discussion (https://cpplang.slack.com/archives/C27KZLB0X/p1734335425348809 <https://cpplang.slack.com/archives/C27KZLB0X/p1734335425348809 >). You don’t need to read it if you’re not interested. I’ll try to make the post itself self contained. The original story comes from a high quality experiment for C++20 modules in boost (https://anarthal.github.io/cppblog/modules2 <https://anarthal.github.io/cppblog/modules2 >). The blog reads pretty good to me. However, anarthal (the author) told me later that the process of supporting modules in boost got suspended since the authors (or the maintainers) don’t want it since no one is going to use them. And if I want it, I need to send a mail here. Then this is the beginning of the story. First of first, I want to emphasize that “no one is going to use them” is not true. We’ve already used C++20 modules at larger scale internally for roughly a year. For boost (and other third party libraries), we choose to wrap a module ourselves as a workaround (with some compiler extensions to ease the refacotoring, but we don’t like it. We still want standard behavior). We didn’t reach out since we feel boost will support C++20 modules later or sooner so we don’t need to do anything specially. (Maybe we were wrong. We didn’t understand the ecosystem enough). Until yesterday, I just knew that boost didn’t know such needs. Before I wrote this email, I wondered a lot of words to emphasize that our need are a good example and the users of closed source are important users too. But just now, I searched the use of boost in modules in GitHub. I just realized I can show it (the importance of C++20 modules support for boost) much easily with the open source world. I searched `boost path:*.cppm` in GitHub and got the following list: https://github.com/infiniflow/infinity/blob/fa922afd58c973a9a317d2c09ad8cea… <https://github.com/infiniflow/infinity/blob/fa922afd58c973a9a317d2c09ad8cea… > https://github.com/ossia/score/blob/0ce6f62a97651a1248a92b3e13ce6ede10341d1… <https://github.com/ossia/score/blob/0ce6f62a97651a1248a92b3e13ce6ede10341d1… > https://github.com/RichardLuo0/make-dot-cpp/blob/e2ef10fd43060a2b56fc8f87f1… <https://github.com/RichardLuo0/make-dot-cpp/blob/e2ef10fd43060a2b56fc8f87f1… > https://github.com/slaakko/cmajor-mod/blob/32e6eb8dc099b395fa751340de96f478… <https://github.com/slaakko/cmajor-mod/blob/32e6eb8dc099b395fa751340de96f478… > https://github.com/df-com/dragonfly/blob/9dfcbc1153f292eb8581f1df7459600cc3… <https://github.com/df-com/dragonfly/blob/9dfcbc1153f292eb8581f1df7459600cc3… > https://github.com/nofe1248/Helium/blob/92ec4452b8c05e6d86c972f843196a4392a… <https://github.com/nofe1248/Helium/blob/92ec4452b8c05e6d86c972f843196a4392a… > https://github.com/LagrangeDev/liblagrange/blob/10e3b48f8d47fd65de00b14cfed… <https://github.com/LagrangeDev/liblagrange/blob/10e3b48f8d47fd65de00b14cfed… > https://github.com/yudaichen/feature-db/blob/e94ade969af682ed5dd25d70bf282b… <https://github.com/yudaichen/feature-db/blob/e94ade969af682ed5dd25d70bf282b… > This is not a complete list even for my search only and I believe there are other patterns to use boost with modules now (e.g., at least `*.cppm` is not the defacto suffix). And I also believe, from my experience as a C++ user, if boost provide modules, I may try to use it. But if boost didn’t provide it, maybe I won’t ask for it if I don’t want modules super bad. Since modules doesn’t add any new functionality actually. So most users may not ask for it explicitly. But if boost provides it, people may give it a try. The above text are the body of the post. I hope it can show it is needed. — Following of are some technical discussion for the extra maintainance burden by introducing modules. The conclusion is, I think, the burden is pretty low. Since modules are not complex to users. Different from other big features in C++, modules are pretty easy to understand. The complexity of modules are majorly on tools and the ecosystem. For programmers who don’t get involved to much to the ecosystem (or infrastructure), modules should be pretty easy to understand. For authors of libraries, after boost introduce modules, you only need to do 2 extra things: - In headers, add a macro (assume its name as BOOST_MODULE_EXPORT, which will be ‘export’ conditionally) to the entities that need to be exported. - In headers, include standard headers and other dependent headers conditionally so that we don’t include anything if the headers are in a module unit. e.g., https://github.com/boostorg/pfr/blob/f09e6aeae9d050897fff72b93d5f5e866cc5e1… <https://github.com/boostorg/pfr/blob/f09e6aeae9d050897fff72b93d5f5e866cc5e1… > then that’s roughly all you need for maintaining it at source level. For building and distributing related things, anarthal told me that the boost will handle it globally so the individual arthors don’t need to care about it. — In slack, there are some other discussion about module names and linking problems (https://cpplang.slack.com/archives/C27KZLB0X/p1734345716728609 <https://cpplang.slack.com/archives/C27KZLB0X/p1734345716728609 >). But I feel they are implementation details. I may not talk too much for that as a user at least now. And also there are opinions for configuration flags. These are the jobs of build systems (cmake is working on it). I think boost don’t need to worry for that. Similarly, at least libc++ has similar problems but libc++ still released std module. — Boost has a special position in the C++’s ecosystem. The most simple and impressive answer I’ve heard for the question “when can we start to use modules” is, “when boost makes it”. Thanks, Chuanqi

15 85

observing process blocked on find_or_construct
by Murali Kishore 28 Jan '25

28 Jan '25

Hi , We are trying interprocess scenario, one process created shared memory objects and killed and second process open the object using find_or_construct seeing this process blocked at getting lock. bt as shown below, #0 __lll_lock_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:135 #1 0x00007fa6b6733eb6 in _L_lock_941 () from /lib64/libpthread.so.0 #2 0x00007fa6b6733daf in __GI___pthread_mutex_lock (mutex=mutex@entry=0x7fa6b198b070) at ../nptl/pthread_mutex_lock.c:113 #3 0x0000000001bc3822 in lock (this=0x7fa6b198b070) at /x86/include/boost/interprocess/sync/posix/recursive_mutex.hpp:90 #4 lock (this=0x7fa6b198b070) at /x86/include/boost/interprocess/sync/interprocess_recursive_mutex.hpp:163 #5 scoped_lock (m=..., this=<synthetic pointer>) at /x86/include/boost/interprocess/sync/scoped_lock.hpp:81 #6 boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family, boost::interprocess::offset_ptr<void, long, unsigned long, 0ul>, 0ul>, boost::interprocess::iset_index>::priv_generic_named_construct<char> (this=0x7fa6b198b010, type=<optimized out>, name=0x7ffde183ca20 "reported_slice_config_list", num=1, try2find=<optimized out>, dothrow=<optimized out>, table=..., index=..., is_intrusive=...) at /x86/include/boost/interprocess/segment_manager.hpp:1076 #7 0x0000000001bee007 in boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family, boost::interprocess::offset_ptr<void, long, unsigned long, 0ul>, 0ul>, boost::interprocess::iset_index>::priv_generic_construct (this=<optimized out>, name=name@entry=0x7ffde183ca20 "reported_slice_config_list", num=num@entry=1, try2find=try2find@entry=true, dothrow=dothrow@entry=true, table=...) at /x86/include/boost/interprocess/segment_manager.hpp:760 #8 0x0000000001bf112d in generic_construct<boost::container::map<unsigned int, gnb::broadcast_plmn_list, std::less<unsigned int>, boost::interprocess::allocator<std::pair<unsigned int const, gnb::broadcast_plmn_list>, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> > > > (table=..., dothrow=true, try2find=true, num=1, name=0x7ffde183ca20 "reported_slice_config_list", this=<optimized out>) at /x86/include/boost/interprocess/segment_manager.hpp:704 #9 operator()<std::less<unsigned int>, boost::interprocess::allocator<std::pair<unsigned int const, gnb::broadcast_plmn_list>, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family, boost::interprocess::offset_ptr<void, long int, long unsigned int, 0ul>, 0ul>, boost::interprocess::iset_index> >&> (this=<optimized out>) at /x86/include/boost/interprocess/detail/named_proxy.hpp:132 please let me know in which cases this can be occured, we see first process also hangs in termination. -- Regards, Murali Kishore

3 3

End of Boost.Decimal Review
by John Maddock 25 Jan '25

25 Jan '25

The review of the proposed Decimal library has now ended - although given that there was a lot of lively discussion for me to sort through, there is still time to submit a late review if you wish. If I've counted correctly there were 5 reviews (4 on the list, one private): one firm reject and 4 conditional accept, plus many more people involved in the discussion than gave reviews. I have to be honest, I would have liked to have seen a couple more reviews in order to have reached a clearer consensus, so please bare with me while I sift through all the comments and try and reach a conclusion. My thanks to everyone who took part, and of course to Matt and Chris for submitting the library. Best, John.

1 0

GSoC 2025 Projects
by Matt Borland 24 Jan '25

24 Jan '25

All, In the modules thread and on Slack, I asked if Boost had a current plan for participation in GSoC 2025. I haven't received any responses yet, so I'll assume there isn't a plan. I'm wondering if anyone has: a) Projects they would like to propose for GSoC, and b) An interest in mentoring. Here are some ideas that I think could be beneficial and approachable: 1) A proof of concept for a Boost module, including distribution and installation processes, and potentially adding support to select libraries. This project could have easy access to the Clang and MSVC teams via their mentor it seems. 2) Bi-variate interpolation has been requested before in Math. ACM TOMS algorithms 751 and 761 could fit the bill, but their references are written in F77. A faithful translation and implementation of those papers would be a good start. 3) Chris Kormanyos and I are working on a cryptographic module that we intend to have certified under FIPS 140-3 and then propose to Boost. An extension of this could be a TLS project where a student provides a proof of concept with a generic file transfer server or similar that works securely with OpenSSL, and then also with our new module. I can mentor at least one of these projects. If anyone has past applications for the organization, please send a link or copies. We have until mid-Feb to apply as an organization, which I can do if no one else volunteers. Best, Matt

5 8

Another Boost.Decimal Review
by Jeff Garland 23 Jan '25

23 Jan '25

Thanks to Matt Borland and Chris Kormanyos for this good work. I vote to ACCEPT the library. I trust the authors to improve documentation, api, and performance as a matter of continued development. Let me say a few things about some discussions in the review threads up-front. *Standardization:* I'm an advocate for it and would be willing to help the authors with the process. Rationale: 1) this standardizes existing practice (aka IEEE 754), something like it is supported in many languages (specifically C23), and there's significant use cases for this in many domains even if it's slightly slower. 2) While a standalone library can go far, often a compiler/library can more easily optimize fundamental things like numeric types. 3) I spoke with Dietmar about the review and standardization -- he's still an advocate for having this capability, but has higher priorities at the moment. *N2849*: It's a decent design for 2009 -- less so in 2025. Specifically, w.r.t. conversion we should only perform automatic conversions from types (see below). The library already takes care of from_chars, format and some other more modern things N2849 wouldn't address. *C23 and _Decimal** Should this library consider being a layer over C23 types where that's possible? GCC supports them at least in a limited fashion. https://gcc.gnu.org/onlinedocs/gcc/Decimal-Float.html > Does this library bring real benefit to C++ developers for real world use-case? > Do you have an application for this library? Yes and yes. > Does the API match with current best practices? I have some quibbles here. *Construction*: template <typename T, typename T2>constexpr decimal32(T coeff, T2 exp, bool sign = false) noexcept; Is the sign flag helpful here? It seems simpler to just handle a negative coefficient -- like it already does. When I look at it there's already cognitive dissidence in my brain about if the sign flag *overrides* or *inverts* the coefficient sign. The N2849 api doesn't have this flag. *Fast Types:* I read through the list conversation about the _fast types. My suggestion is to drop them. Simplifies everything for users and implementers. The movement in c++ over the last decade(s) has been to precisely say the size of the type to ensure correctness and not 'let the platform decide' (aka uint32_t, int64_t, etc). In my comment on documentation you'll notice the c++20 extended floating point types *only provide* fixed sizes. Also N2849 and C23 don't support _fast types for decimal. *Conversions:* I'd like to see the library *pull back* on convertibility. long double ld{1.23456789234567}; decimal32 d(ld); // what happens -- round, truncate, doesn't compile? The best answer is doesn't compile. There's been significant work in the standard now to define floating point rank and limit conversions with the extended floating point types. Specifically: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p1467r9.html#rank There's also other work on type traits and value preserving conversions in the SIMD capabilities. Also, std::chrono basically already does this -- any value destroying conversion has to be explicit. At a minimum the answer needs to be better documented - aka does what 754-2008 says? For other examples of things I'd remove and make a free function cast/round -- aka explicit user decision: class decimal64 { ... explicit constexpr operator std::int8_t() const noexcept; This is highly likely to not be value preserving so shouldn't be possible without a decision on how to handle overflow. class decimal64 { ... explicit constexpr operator decimal32() const noexcept; *Literals* constexpr auto operator "" _DF(const char* str) -> decimal32constexpr auto operator "" _df(const char* str) -> decimal32 Why not _d32, _d64, _d128? _df makes me think fast, not 32. > Is the documentation helpful and clear? Not bad, but as usual improvements can be made. As a user I'm going to need to select one of these types -- I'd love to see a table like this one at cppreference for named floating point types: *Type name* Defined in header <stdfloat> <https://en.cppreference.com/w/cpp/header/stdfloat> Literal suffix Predefined macro C language type Type properties bits of storage bits of precision bits of exponent max exponent std::float16_t f16 or F16 __STDCPP_FLOAT16_T__ _Float16 16 11 5 15 std::float32_t f32 or F32 __STDCPP_FLOAT32_T__ _Float32 32 24 8 127 std::float64_t f64 or F64 __STDCPP_FLOAT64_T__ _Float64 64 53 11 1023 std::float128_t f128 or F128 __STDCPP_FLOAT128_T__ _Float128 128 113 15 16383 std::bfloat16_t bf16 or BF16 __STDCPP_BFLOAT16_T__ (N/A) 16 8 8 127 Not sure how it renders in email so source: https://en.cppreference.com/w/cpp/types/floating-point Not looking for exact replication, but something like this. In the *using the library* section I'd like to see some: - examples of using it it math - examples of the behavior of NAN/inf values - conversions from other types like float expanded Where is the design decisions section? Some of the things I'm asking about should be covered in the docs. > Did you try to use it? What problems or surprises did you encounter? I didn't have time to play with it unfortunately -- godbolt would be helpful. That's all for now. Jeff

4 5

Re: [boost] Decimal: Formal review begins
by Glen Fernandes 23 Jan '25

23 Jan '25

I mentioned this to Matt, but I would like to see benchmarks comparing boost::decimal64_fast to a Decimal64 backed by Intel's DFP library, which is what I know to be in actual use today: https://www.intel.com/content/www/us/en/developer/articles/tool/intel-decim… Not that the benchmarks comparing to GCC's Decimal64 (which is based on the libbid which ships with libgcc) aren't useful, I personally don't know anyone using that today. Benchmarks should ideally also include Intel's compiler, because at least one of the relevant parties who motivated me to suggest the Decimal64 library (to Vinnie as a potential project) do use the Intel C++ compiler (and their Fortran compiler) for areas where they perform better. (The non-fast versions don't matter to me. I don't know anyone who would want to use them). Glen

12 36

Decimal Library: Last call for reviews?
by John Maddock 22 Jan '25

22 Jan '25

Formally, today is the last day of the Decimal Library review, so far there has been a lot of discussion, but only three full reviews with outcomes. Are there any more reviews incoming? Thanks, John.

1 0

My review of Decimal
by Ivan Matek 21 Jan '25

21 Jan '25

Hi everybody, PDF size exceeds ML limit so here is google drive link https://drive.google.com/file/d/1kH9WkeTDxN7FFqM_g7hV_-e3kJPlTGBr/view

6 16

Reminder to submit Boost.Decimal reviews
by John Maddock 20 Jan '25

20 Jan '25

Just a gentle reminder that the Decimal library review is currently ongoing, there's been plenty of discussion, but only one full review so far.... so if you're thinking of submitting a review, now would be the time ;) Thanks all, John.

1 0

Fw: Boost accepted in Google Summer of Code 2021
by Christopher Kormanyos 17 Jan '25

17 Jan '25

----- Forwarded Message ----- From: "boost-users-owner(a)lists.boost.org" <boost-users-owner(a)lists.boost.org>To: "e_float(a)yahoo.com" <e_float(a)yahoo.com>Sent: Wednesday, March 10, 2021 at 07:51:24 PM GMT+1Subject: Re: [boost] Boost accepted in Google Summer of Code 2021 To post messages to the Boost Users mailing list, you will need to subscribe this e-mail address via the Boost mailing list web page at: http://lists.boost.org/mailman/listinfo.cgi/boost-users You will need to take this step even if you intend to post only through GMane or some other news gateway. In this case, you may wish to edit your subscription options to turn off mail delivery. >> We're in again! > Thank you, David! Hi Matt (@mborland) This was, as far as i recall, our last successful timegetting into and finishing some GSoC 2021 projects. We had that whole Corona thing going on and it wasa tough time for everyone. As far as applying as an org, maybe David hassome old material. - Chris_________________________________________Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost

2 2

Adding logical implication to boost
by Ivan Matek 09 Jan '25

09 Jan '25

Hi everyone, there has been a recent proposal to add logical implication to C++ as an operator. github tracking issue <https://github.com/cplusplus/papers/issues/1641> P2971R2 <https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p2971r2.pdf> For a video description you can see this talk <https://youtu.be/bgyY3x8y4PE?feature=shared&t=1470> by Walter(it is only few minutes, not entire talk). While I agree with concerns mentioned on the issue, i.e. using a *precious *token => on rarely used functionality I do think that implementing a simple function helper is reasonable. Poll in issue shows that this is also likely standardization future. POLL: We agree with adding a function object logical_implication (tentative name, akin logical_and, `logical_or’). SF F N A SA 9 12 3 0 0 As for if it is worthwhile to add this simple logic to boost instead of people just writing their own I will just say I would prefer to have something named in boost instead of people reinventing same thing many times in their projects. I have used it few times in my career, so quite rarely, but again that means I have used it much more often than 80+% of algorithms in <algorithm> header. As for location I presume best place would be Boost.Algorithm although you could say that Boost.Core can be a candidate because it is a basic operation and would benefit from shorter namespace. I would be still inclined against this since I have seen core/util/common become huge in many codebases I have worked in. I have tried to check if this already exists in Boost; all I found was an example in Boost.Hana.

6 7

Forthcoming Decimal Library review (15th Jan)
by John Maddock 08 Jan '25

08 Jan '25

Just a gentle reminder that the review of the decimal number library by Matt Borland and Chris Kormanyos will start NEXT WEDNESDAY 15th Jan. The library is an implementation of IEEE 754 Decimal Floating Point Numbers. Documentation: https://cppalliance.org/decimal/decimal.html Code: https://github.com/cppalliance/decimal/ Motivation: Current C++ floating point types store the significand (often incorrectly referred to as the mantissa) as binary digits. Famously this leads to representation errors: https://0.30000000000000004.com <https://0.30000000000000004.com>. Decimal floating point numbers avoid this issue by storing the significand in base-10 (decimal). The other major difference between binary and decimal floating point types is that the latter allows for multiple representations of the same number. For example 1e5 could also be stored as 0.1e6, 0.01e7, so on and so forth. These are referred to as cohorts which binary does not have as there is only one way to represent each number in binary floating point. Use Cases: The use case for Decimal Floating Point numbers is where rounding errors are significantly impactful such as finance. In applications where integer or fixed-point arithmetic are used to combat this issue Decimal Floating Point numbers can provide a significantly greater range of values. For example, while a fixed-point representation that allocates 8 decimal digits and 2 decimal places can represent the numbers 123456.78, 8765.43, 123.00, and so on, a floating-point representation with 8 decimal digits could also represent 1.2345678, 1234567.8, 0.000012345678, 12345678000000000, and so on. I believe Matt has some minor doc updates to push between now and next week, but other than that the library is good to review (but hold your fire until we start next week unless you're away etc). Best, John.

1 0

Invalid sha256 for boost_1_87_0.tar.bz2 archive
by Samuel DEBIONNE 07 Jan '25

07 Jan '25

Dear all, In the conda forge CI (that builds the boost packages), I noticed that some jobs are failing due to a difference between the advertised and computed sha256 checksum. The json file at https://archives.boost.io/release/1.87.0/source/boost_1_87_0.tar.bz2.json has af57be25cb4c4f4b413ed692fe378affb4352ea50fbe294a11ef548f4d527d89 While sha256sum of https://boostorg.jfrog.io/artifactory/main/release/1.87.0/source/boost_1_87… gives 79e6d3f986444e5a80afbeccdaf2d1c1cf964baa8d766d20859d653a16c39848 Has the archive been updated and not the sidecar json file? Thank you, Samuel

2 2

Your Boost Talk at CppCon?
by Vinnie Falco 02 Jan '25

02 Jan '25

Hi everyone. I think it would be nice to have several talks about Boost for the 2025 CppCon program. We need volunteers who are able to attend and give a talk. If you are interested please email me at vinnie.falco(a)gmail.com to indicate your intent and propose a subject for the talk. There are some resources available to help volunteers get their abstract prepared for submission, to improve the quality of the proposal, ensuring a greater likelihood of the talk being accepted. Getting a Boost talk accepted has been hit or miss in recent years and I would like to change that. If we can get enough volunteers involved much earlier in the process (say, this month) then we have time to assemble a strong "Boost track" with high quality abstracts. This can incentivize the conference to make Boost talks an enduring feature of its programs going forward. If you have questions or comments about Boost talks at CppCon or other conferences, a discussion here is also welcomed. Thanks!

1 0

Re: [boost] announcing boost.async
by microcai 01 Jan '25

01 Jan '25

Klemens Morgenstern via Boost <boost(a)lists.boost.org> 于2023年3月17日周五 23:22写道： > Hi, > > I've been working on a C++20 coroutine library, called `async`, > which is meant to be for C++ what asyncio is for python or generic > async/await is for javascript. > It's meant to be a framework for single threaded coroutine applications. > > It provides coroutine types, such as promises, tasks and generators to > generators are useless for real word coroutine usage. > model async operations, > channels for inter-coroutine communication and functions > like select, gather & join to wait or combine multiple awaitables. > > It's asio-based, i.e. uses asio::io_context as its event-loop and can > co_await any asio operation. > > As this is a very complex domain, I really would be happy to have some > users. > This will help me to improve documentation & come up with more > example ideas. > > Docs: https://klemens.dev/async > Repo: https://github.com/klemens-morgenstern/async > > _______________________________________________ > Unsubscribe & other changes: > http://lists.boost.org/mailman/listinfo.cgi/boost >

2 1

[boost.context] questions about Lazy Float Point State Preservation
by microcai 01 Jan '25

01 Jan '25

Does jum_fcontext do lazy state preservation on FPU? most of the time, coroutine is executing async IO code rather than cpu intensive code. Mostly, IO code does not use floating point. but no preserving FPU state is error prone. Does fcontext employ "lazy state preservation on fpu registers"?

1 0