September 2020 - Boost - lists.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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Boost.Text is looking for a (mini-)review manager
by Zach Laine 07 Dec '22

07 Dec '22

I've made all the recommended changes to Boost.Text that came up in the review. Glen, the previous review manager, recommended a mini review of Boost.Text once I'd made those changes. If you'd like to manage the mini-review, please let me know. For everyone, including potential reviewers and review managers, here are the major changes: * All the specific review feedback issues have been addressed. * The string layer is now gone. * The text layer got a major re-work. It is now a set of template-based adaptors (basic_text<>, vs. a text typedef. etc.), which lets everyone get what they want. You can change the underlying storage type (including whatever allocator you prefer), select UTF-8 or UTF-16, and change the normalization form. Glen recommended I drop this layer, but the library is way less useful without this stuff, and these changes address all the concerns raised about the text layer in the review. The updated docs can be found here: https://tzlaine.github.io/text/doc/html/index.html Oh yeah, and I added concept constraints to the whole library when you build in C++20 mode. Zach

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[review][JSON] Review of JSON starts today: Sept 14 - Sept 23
by Pranam Lashkari 09 Aug '22

09 Aug '22

Boost formal review of Vinnie Falco and Krystian Stasiowski's library JSON starts today and will run for 10 days ending on 23 Sept 2020. Both of these authors have already developed a couple of libraries which are accepted in Boost(boost beast and Static String) This library focuses on a common and popular use-case for JSON. It provides a container to hold parsed and serialised JSON types. It provides more flexibility and better benchmark performance than its competitors. JSON highlights the following features in the documentation: - Fast compilation - Require only C++11 - Fast streaming parser and serializer - Easy and safe API with allocator support - Constant-time key lookup for objects - Options to allow non-standard JSON - Compile without Boost, define BOOST_JSON_STANDALONE - Optional header-only, without linking to a library (a point I would like to add in highlight: it has cool Jason logo 😝) To quickly understand and get the flavour of the library take a look at "Quick Look" <http://master.json.cpp.al/json/usage/quick_look.html> You can find the source code to be reviewed here: <https://github.com/CPPAlliance/json/tree/master> You can find the latest documentation here: <http://master.json.cpp.al/> Benchmarks are also given in the document which can be found here: <http://master.json.cpp.al/json/benchmarks.html> Some people have also given the early reviews, the thread can be found here: <https://lists.boost.org/Archives/boost/2020/09/249745.php> Please provide in your review information you think is valuable to understand your choice to ACCEPT or REJECT including JSON as a Boost library. Please be explicit about your decision (ACCEPT or REJECT). Some other questions you might want to consider answering: - 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? - 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 here: <http://www.boost.org/community/reviews.html> Thank you for your effort in the Boost community. -- Thank you, Pranam Lashkari, https://lpranam.github.io/

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Adding my sorting algorithm, ska_sort, to boost, attempt 2
by Malte Skarupke 24 Nov '21

24 Nov '21

Hi everyone, I started a discussion about this in October, but at the time the maintainer of the sort library was busy, then I was busy, so now it's January... I wrote a generalized version of radix sort a couple years ago and gave a talk about it here: https://www.youtube.com/watch?v=zqs87a_7zxw I would like to get a new version of that sorting algorithm into boost. It's faster than what I showed several years ago. It's also even more general and has a new interface that should be easier to extend. I uploaded the code here: https://github.com/skarupke/sort/tree/master The documentation is also already updated with new benchmark results. Let me know what's required to get this into boost. Would you like this in the form of a pull request? One of the big things that probably needs review is the interface, since radix sorting works differently than comparison based sorting. For most normal uses you just need to provide a sort key, but more complicated cases can get more complicated. I tried very hard to make everything easy, but I'd also be curious if others can come up with better ways of doing the interface. Thanks, Malte -- Malte Skarupke malteskarupke(a)fastmail.fm

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[FPR] Review of FPR starts Today: Sept 28 - Oct 7
by Benedek Thaler 16 Oct '20

16 Oct '20

The Boost formal review of the FPR (Flat Precise Reflection, ex Magic Get, ex PODs Flat Reflection) starts Today, taking place from September 28, 2020 to October 7, 2020. The library is authored by Antony Polukhin, author of Boost.DLL, Stacktrace, Type Index libraries. Documentation: http://apolukhin.github.io/magic_get/ Source: https://github.com/apolukhin/magic_get The library is meant for accessing structure elements by index and providing other std::tuple like methods for user defined types without any macro or boilerplate code. The FPR documentation summarizes the out-of-the-box added functionality for aggregate initializable structures: - comparison operators - heterogeneous comparators - hash - stream operators - access to members by index - member reflections - methods for cooperation with std::tuple - methods to visit each field of the structure If the description isn't immediately obvious for you, here's a motivating example: // requires: C++14 #include <iostream> #include <string> #include "boost/pfr/precise.hpp" struct some_person { std::string name; unsigned birth_year; }; int main() { some_person val{"Edgar Allan Poe", 1809}; std::cout << boost::pfr::get<0>(val) // No macro! << " was born in " << boost::pfr::get<1>(val); // Works with any aggregate initializables! } Please provide in your review information you think is valuable to understand your choice to ACCEPT or REJECT including FPR as a Boost library. Please be explicit about your decision (ACCEPT or REJECT). Some other questions you might want to consider answering: - 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? - 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 Thank you for your effort in the Boost community. Benedek - review manager of the FPR library

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traits
by Gero Peterhoff 03 Oct '20

03 Oct '20

Hello Peter, I've designed a couple of traits here. Is that right so far so that they can be included in boost? But there are these problems: 1) char8_t is still missing in your is_unsigned 2) my implementations of - is_native; if the type exists natively on the platform - is_vectorisable; if the type can be vectorized on the platform (simd) - is_integer are still incomplete, as I cannot find out whether the corresponding types are available; e.g. on some platforms there is int56_t, but no int8_t (__CHAR_BIT__ > 8), etc. The specializations of is_logic and is_rational should better be done in the libs. If a concept is created, it is stored in boost::mata so that there are no naming conflicts. Similar to math::constants there is also a string::constants; maybe also makes sense. regards Gero

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new type traits
by Gero Peterhoff 03 Oct '20

03 Oct '20

Hello Developers, I would like to retrofit some type-traits in boost, but I have read https://pdimov.github.io/articles/phasing_out_cxx03.html. Now I don't know how to do it best, as the boost-type-traits may be removed. Would the following procedure make sense? We get the std-traits and concepts in a namespace boost::meta, eg file boost/type_traits/meta.hpp: #ifndef BOOST_META_HPP #define BOOST_META_HPP #include <type_traits> #if defined(__cpp_concepts) #include <concepts> #endif namespace boost::meta { template <typename Type> using is_integral = std::is_integral<Type>; template <typename Type> inline constexpr bool is_integral_v = std::is_integral_v<Type>; template <typename Type> using is_pointer = std::is_pointer<Type>; template <typename Type> inline constexpr bool is_pointer_v = std::is_pointer_v<Type>; ... all other #if defined(__cpp_concepts) template <typename Type> concept integral = std::integral<Type>; template <typename Type> concept pointer = is_pointer_v<Type>; ... #endif } // boost::meta #endif // BOOST_META_HPP Then you could possibly map this in boost/type_traits.hpp to boost:: (if that makes sense): #ifndef BOOST_TYPE_TRAITS_HPP #define BOOST_TYPE_TRAITS_HPP #include <boost/type_traits/meta.hpp> remove boost implementations namespace boost { using namespace boost::meta; } // boost #endif // BOOST_TYPE_TRAITS_HPP In this way, new traits can be added in boost/type_traits/meta.hpp that are based on the std-traits, e.g. is_logic namespace boost::meta { template <typename Type> struct is_logic : std::false_type{}; template <typename Type> inline constexpr bool is_logic_v = is_logic<Type>::value; template <> struct is_logic<bool> : std::true_type{}; #if defined(__cpp_concepts) template <typename Type> concept logic = is_logic_v<Type>; #endif } // boost::meta and in this case add in boost/logic/tribool.hpp namespace boost::meta { template <> struct is_logic<boost::tribool> : std::true_type{}; } // boost::meta Or do you have a better idea? regards Gero

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[PFR] The user's perspective
by Andrzej Krzemienski 02 Oct '20

02 Oct '20

Hi Everyone, I am now trying to study the PFR library, and wanted to share some thoughts and see what others think. First, thanks Antony for writing and sharing this library. I have watched your video on it, read the docs, and I find it amazing that you were able to implement such reflection in C++. This is in the spirit of the good old Boost libraries that just implemented magic. Now, to the critique. From looking at the docs and the videos, I inferred (perhaps incorrectly) that the library was created in this order: "We can do type introspection for aggregates, so let's see to what extent we can provide an interface of a reflection library." The extent is quite amazing (e.g., I really appreciate having pfr::less<> out of the box), but to the end user, I think, the library will still appear as incomplete. That is, when my type is an aggregate it will work, but when I need to add a convenience constructor it will immediately break, and I will have to switch to another library, like Peter's Describe ( https://github.com/pdimov/describe/tree/master) With Describe, I will have to type more, but I have a guarantee of a uniform experience both for aggregates and for other types. And given that I have to use Describe at some point there may be no point in also keeping PFR and forcing on myself and my colleagues two different interfaces. Describe is not a perfect solution either, because for aggregates I have to declare the mapping, which is unnecessary as PFR has demonstrated. My ideal solution would be if these two libraries (PFR and Describe) would be merged into one, so that: 1. They provide the same interface 2. A user can easily instruct the library: "this is an aggregate: figure out the mapping yourself". I am sorry if it sounds arrogant: people are devoting their private time to write and share a cool library, and all they hear back is "do more." But I thought it would also be unfair not to give this feedback. I am also not sure if the goals of the two libraries are compatible (e.g., Describe is also interested in giving names of the members) . I would be curious to see what the authors think about it. Regards, &rzej;

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Cache Size
by Matt Borland 01 Oct '20

01 Oct '20

A recurring discussion in Boost.Math has been needing a cross-platform way to query the L1D cache size of a machine. I have most of a solution in a [personal repo](https://github.com/mborland/cache). It did not make sense to us to have this in Boost.Math because it would be useful outside of that scope, but we did not know where it should go. Is there an existing library where this would fit? If necessary I can roll it into a library submission that exposes the functionality of CPUID. Matt

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[review][json] My review
by Gavin Lambert 30 Sep '20

30 Sep '20

- Do you think the library should be accepted as a Boost library? Yes, my vote is to ACCEPT this library. - What is your evaluation of the design? Much has been debated recently on the merits of push parsers vs. pull parsers. Boost.JSON provides both a push parser (SAX-like interface) and a DOM parser (which is somewhat pull-like but I don't think is technically either kind). It does not provide a "real" pull parser, which are sometimes more efficient for deserialisation into custom types; the SAX parser can somewhat do that but is not composable, which makes it harder to use in practice, unless I'm missing something (this is usually why I end up never using SAX parsers). If so, I'd like to see a more complete example where the handler delegates part of the parsing to a class that in turn delegates part to another class (as with reading typed sub-values). I don't think this is currently possible. So I think I can understand some of the debate around this point; while I don't think it's strictly necessary that this particular library implement that, if it doesn't then another library will end up having potentially competing types and the natural Boost.Json name will already be taken. Personally, however, I don't think this is sufficient reason to block acceptance of this library. Direct pull parsing doesn't mesh well with JSON, due to the requirement to tolerate reordered keys, so any non-defective parser would have to have something DOM-like under the hood anyway. (Some kind of cache, if not necessarily a traditional DOM.) As such it should be sufficient to use json::value itself as part of a pull-like parsing interface. Regarding the SAX parser specifically, I dislike the *_part methods in the callback interface. I feel that these should be removed and only the final form retained, called only when the complete text of the value has been determined. I don't feel it is ever sensible to call back with a partially-parsed value (unless I am misunderstanding what these are for, but there is little explanation in the docs, and I wasn't able to get them called at all in my test). I also don't see the point of supplying a size argument to on_key* and on_string, as this can be read from the string_view argument instead. The various number methods don't pass this separately. Similarly, having a bool return as well as an error_code output argument seems peculiar; one or the other should be sufficient, as is it just invites inconsistency. parser.write() is incremental but basic_parser.write() is not, which seems odd. I assume this means that parser is storing an incrementally populated buffer of the full document rather than _really_ incrementally parsing. parse/parser do not appear to support consuming only part of the supplied input as a complete JSON value (returning how much was consumed), which is useful for streams where multiple objects are concatenated without explicit separation. Regarding other aspects of design, I haven't drilled down in great detail but the basic interface seems reasonably sound, other than the concerns raised above. I have mixed feelings on the initializer-list construction method -- I like that there is some method of doing this, and it seems like idiomatic C++ (particularly regarding how key-value pairs appear), but also very non-JSON -- an array of objects ends up having three nested braces. But I don't have any specific suggestion for improvement. - What is your evaluation of the implementation? It seems unfortunate (though understandable, due to heap allocation) that you cannot declare a json::value / json::object as constexpr, for cases where you do want some kind of constant reference object (e.g. a schema description). You can somewhat work around this by declaring the JSON as a constexpr string_view and later parsing it to a non-constexpr json::value, but that seems a bit awkward (and potentially bad-perf-prone if someone parses it multiple times). Otherwise I didn't really look into the implementation at all. - What is your evaluation of the documentation? Overall, good, if perhaps a bit sparse on some aspects. One pet peeve however is that most of the examples appear to be written as if "using namespace boost::json" is in effect, which I feel both encourages bad practice and makes it harder to distinguish which types are provided by the library vs. exist only for the example. This is especially confusing in the examples for tag_invoke, but not only there -- another example of confusion are the aliases for types present in both boost and std namespaces. I strongly recommend going through and changing these to explicitly use a json:: namespace prefix on all library types (including the boost/std aliases). Brevity is useful, but not at the expense of clarity. The "Using Numbers" section of the docs appears to be entirely blank. "serializer can be used to incrementally serialize a value incrementally" (redundant words are redundant) (On a related note, an example use case for serializer is listed as "ensure a fixed amount of work is performed in each cycle", but the only means of control is the length of the provided buffer. I guess this is equating work to number of characters output, which seems dubious. But I have no specific objections.) - What is your evaluation of the potential usefulness of the library? The library seems well suited for JSON as inter-process/network data interchange, other than perhaps the omission of partial input parsing. It seems less suited for JSON as configuration file -- while it can parse such files (via common extensions such as ignoring comments and trailing commas) it lacks means to pretty-print and to round-trip the comments, which would be essential if writing back a config file intended for human use. However while supporting this use case would be nice, I don't consider it mandatory. - Did you try to use the library? With what compiler? Did you have any problems? I tried it out with MSVC 2017 in standalone header-only mode, though only with a few small examples. The basic_parser examples do not compile out of the box -- with the suggested json.hpp and src.hpp includes there are link errors with basic_parser symbols. Additionally including basic_parser.hpp resolves these but starts complaining about missing max_{key,string,array,object}_size members of the handler type, which are not documented. After these are supplied then it works as expected. I don't see why these should be needed, however. - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? Roughly four hours over a few days reviewing docs and trying some small experiments. - Are you knowledgeable about the problem domain? I have some apps that use JSON as both interchange and configuration storage formats, although most of these do not use C++. So, "somewhat".

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