January 2018 - 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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[foreach][polygon][xpressive][bimap][ptr_container][gil][assign][typeof][msm] PRs for removing executable attribute for files
by Edward Diener 08 Mar '18

08 Mar '18

The following libraries still have PRs, which I have previously submitted, for removing the executable attribute for one or more files: foreach polygon xpressive bimap ptr_container gil assign typeof msm None of these PRs affect anything other than the file attribute, so no testing is needed AFAICS since no code changes. If the maintainers of the above libraries, or someone else with write access to these libraries, can merge the appropriate PR to 'develop', and then merge 'develop' to 'master', we can get rid of having any files with their executable attribute set in the next release.

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[yap] Re-announcing Yap
by Zach Laine 23 Feb '18

23 Feb '18

I posted 2-3 months ago about Yap, an expression template library I've written that I intend to propose for Boost. This is just a reminder that the library exists, and where to find it. I'm giving a talk about it at C++Now 2017, and some time after that I intend to submit it to the queue. Louis Dionne has offered to serve as review manager when the time comes. You can find the main repo on GitHub: https://github.com/tzlaine/yap And online docs are here: https://tzlaine.github.io/yap Zach

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Query for interest in library: reflective enum
by Nir Friedman 23 Feb '18

23 Feb '18

Hello, I recently needed a reflective enum for work (that is an enum where you can programmatically convert to and from strings, know how many enumerators there are, and iterate over all enumerators). I looked online but I didn't find anything that met my requirements. I was surprised that there wasn't one in Boost. So I'd like to see if there is interest; I wrote an implementation that I think has several nice features. The most polished existing smart enum implementation I could find was http://aantron.github.io/better-enums/. However, the enum implemented there is not a true enum; it uses a nested member of a class kind of approach. So for example, the is_enum type trait will not recognize is as an enum. You cannot use it as a non-type template parameter. I strongly think that a good generic smart enum macro should generate the exact "vanilla" enum (or enum class) declaration. My library's syntax looks like this: WISE_ENUM(Foo, BAR, (BAZ, 3)) This generates, among other things, exactly: enum Foo { BAR, BAZ=3}; I intend this as an explicit guarantee of the library that the programmer can count on. That way when Foo is used for things unrelating to reflection, the developer can be confident that there will not be any surprises. Beyond compatability with C++ facilities for enums, and minimizing surprise, another advantage of this approach is that it's guaranteed to be backwards compatible. An existing codebase with an existing enum/enum class can switch to this smart enum with very high confidence that existing code will continue to work as before. The WISE_ENUM macro, beyond generating the vanilla enum, also generates a switch-case function for to-string conversion (for maximal efficiency), and finally it generates a constexpr function that returns a std::array<std::pair<const char*, Foo>> listing all of the arrays and their string descriptions. This constexpr function, which is found via ADL, allows writing a sequence of (constexpr) variables and functions providing the rest of the desired functionality. Usage looks like this: std::cerr << "My enum's size is : " << wise_enum::size<Foo> // this is constexpr template variable auto x = wise_enum::from_string<Foo>("BAR").value(); // from_string returns an optional auto y = wise_enum::to_string(x); // y is string literal, no heap allocation My implementation (POC level) is here: https://github.com/quicknir/wise_enum. I don't yet have separate macros to cover enum/enum class/explicit/implicit backing type combinations. It's only about 100 lines of code, leaning heavily on BOOST_PP to do the heavy lifting. It requires variadic macros, and can probably target C++11 (if it doesn't already). I probably need to "comma harden" the macros for bizarre stuff like WISE_ENUM(Foo, (BAR, my_func<3,4>())). It has the limitation that the macro cannot be used inside a class (this is hard to workaround for reflective macros). It's also unclear how repeated enumeration values would be handled (enum Foo { BAR = 1, BAZ = 1}). As it stands this will cause a compilation failure in the generated switch case of the to_string function. Can discuss more in subsequent emails. One suggested feature is an is_contiguous trait. Another reasonable bit of functionality might be an is_wise_enum trait. Version 2 of this library could target enum sets. Although it's not fancy, I think this nicely covers a piece of functionality I often need, and it does so avoiding any downside compared to using a simple enum (beyond having to use macros). Hope other people will agree! Cheers, Nir

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[release notes] Linking to github issues/pull requests
by Daniel James 14 Feb '18

14 Feb '18

Hi, I've added templates for linking to github issues and pull requests from the release notes. There are two templates: [github module number] which expands to '#number' [github_pr module number] which expands to 'PR#number'. Both will be linked, they need the name of the module to link to the right place. We only really need the issue template as github redirects to the pull request if appropriate, but existing release notes have been using the PR#3 format, so I thought it should support that. You can see an example in the unordered release notes for 1.67.0: https://github.com/boostorg/website/blob/master/feed/history/boost_1_67_0.q… http://www.boost.org/users/history/in_progress.html Does that look okay? Daniel

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[review] Review of Outcome v2 (Fri-19-Jan to Sun-28-Jan, 2018)
by charleyb123 . 09 Feb '18

09 Feb '18

Hi, Everyone, The formal review of Niall Douglas' Outcome (v2) library begins Fri-19-Jan and continues until Sun-28-Jan, 2018. Your participation is encouraged, as the proposed library is uncoupled and focused, and reviewers do not need to be domain experts to appreciate the potential usefulness of the library and to propose improvements. Everyone needs (and has suffered) error handling, and can compose an opinion on that topic. Outcome is a header-only C++14 library providing expressive and very lightweight 'outcome<T>' and 'result<T>' error handling, suitable for low-latency code bases. The library further provides mechanisms for wrapping '<success|error|exception>' state to safely wrap throwing APIs; and poses an idiom of, "islands of exception in a sea of noexcept". Key features: *- Makes using 'std::error_code' from C++11's <system_error> more convenient and safe *- Good focus on low-latency (with tests and benchmarks) *- Error-handling algorithmic composition with-or-without C++ exceptions enabled *- Dependency only on Boost Recall a previous Outcome (v1) Boost Review occurred 19-May to 02-June 2017: *- Outcome (v1) Review Report: *- https://lists.boost.org/Archives/boost/2017/06/235783.php This review for Outcome (v2) includes significant changes as a result of feedback from the Outcome (v1) review. For a list of changes (v1==>v2), see: *- https://github.com/ned14/outcome#changes-since-v1 Reference API docs: *- https://ned14.github.io/outcome/reference/ GitHub: *- https://github.com/ned14/boost-outcome Tarball: *- https://github.com/ned14/boost-outcome/releases/tag/v2. 0-boost-peer-review Online "play-pen" (try it out!): *- https://wandbox.org/permlink/Ji1khzyxoAR0LJQC YOUR REVIEW --------------------- Please post your comments and review to the boost mailing list (preferably), or privately to the Review Manager (to me ;-). Here are some questions you might want to answer in your review: - 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 what compiler? 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? And most importantly: - Do you think the library should be accepted as a Boost library? For more information about Boost Formal Review Process, see: http://www.boost.org/community/reviews.html Thank you very much for your time and efforts. --charley Outcome (v2) Review Manager

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[gsoc18][boost.intrusive]
by Rishabh Arora 05 Feb '18

05 Feb '18

Hello Boost Community, I have proposed a project as a mentor for Google Summer of Code '18, as a new addition to the Boost.Intrusive library. The details about the project proposal and the competency test can be found here: https://github.com/ boostorg/boost/wiki/Boost-Google-Summer-of-Code-2018 (Project-5). All the interested candidates can contact me and send me their competency test on the following e-mail: rishabharora1997(a)gmail.com Best Regards, Rishabh

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[serialization] uuid test_serialization ubsan error
by James E. King, III 01 Feb '18

01 Feb '18

I'm getting a ubsan test error in uuid/test/test_serialization - is the code in that test using archive the right way? testing.capture-output ../../../bin.v2/libs/uuid/test/test_serialization.test/gcc-7/debug/link-static/threadapi-pthread/test_serialization.run ====== BEGIN OUTPUT ====== ../../../boost/archive/detail/interface_oarchive.hpp:47:16: runtime error: downcast of address 0x7ffca0c6fe30 which does not point to an object of type 'text_oarchive' 0x7ffca0c6fe30: note: object is of type 'boost::archive::text_oarchive_impl<boost::archive::text_oarchive>' 00 00 00 00 e0 2f 78 8f 48 56 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ^~~~~~~~~~~~~~~~~~~~~~~ vptr for 'boost::archive::text_oarchive_impl<boost::archive::text_oarchive>' EXIT STATUS: 1 ====== END OUTPUT ====== Thanks, Jim

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[GSOC18] Boost.Geometry Project 1 : Similarity between geometries
by sagarvijaygupta 31 Jan '18

31 Jan '18

I am Sagar Gupta, a student of IIT Mandi, pursuing my Bachelors in Computer Science. I want to work on the Project 1 of Similarity between Geometries. I read the source code of geometry and regarding the Frechet distance and its different variations and tried to work with it. Also I tried the competency test. Its my first time for GSOC but I have some good experience in C++ (from different projects and competitive programming). I wish to know where should I send the competency test? I wish to work on this project as it is a great learning experience which I realized while working on the implementation of Frechet Distance between linestrings. Thanks and Regards Sagar Gupta -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Dev-f2600599.html

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International Conference on Information Society (i-Society 2018): Call for Submissions!
by International Conference on Information Society 30 Jan '18

30 Jan '18

Apologies for cross-postings. Please send it to interested colleagues and students. Thanks! Call for Submissions! ********************************************************************************** International Conference on Information Society (i-Society 2018) 15-18 July, 2018 Venue: Ballsbridge Hotel Dublin, Ireland www.i-society.eu ********************************************************************************* The i-Society is a global knowledge-enriched collaborative effort that has its roots from both academia and industry. The conference covers a wide spectrum of topics that relate to information society, which includes technical and non-technical research areas. The mission of i-Society 2018 conference is to provide opportunities for collaboration of professionals and researchers to share existing and generate new knowledge in the field of information society. The conference encapsulates the concept of interdisciplinary science that studies the societal and technological dimensions of knowledge evolution in digital society. The i-Society bridges the gap between academia and industry with regards to research collaboration and awareness of current development in secure information management in the digital society. The topics in i-Society 2018 include but are not confined to the following areas: *New enabling technologies - Internet technologies - Internet of Things (IoT) - Wireless applications - Mobile Applications - Cloud and iCloud - Multimedia Applications - Protocols and Standards - Ubiquitous Computing - Virtual Reality - Human Computer Interaction - Geographic information systems - e-Manufacturing - Electronic Discovery (eDiscovery) - Software Applications - Disruptive Technology *Intelligent data management - Intelligent Agents - Intelligent Systems - Intelligent Organisations - Content Development - Data Mining - Data Management Software - e-Publishing and Digital Libraries - Information Search and Retrieval - Knowledge Management - e-Intelligence - Compliance and Recovery from Data Loss - Knowledge networks - Risk Mitigation - Cost Efficiency - Quality Assurance - Information Management - Support Litigation - Complex Investigations *Secure Technologies - Internet security - Web services and performance - Secure transactions - Cryptography - Payment systems - Secure Protocols - e-Privacy - e-Trust - e-Risk - Cyber Security Investigations and Defence - Cyber law - Forensics - Information assurance - Mobile social networks - Peer-to-peer social networks - Sensor networks and social sensing - Information Security Compliance *e-Learning - Collaborative Learning - Curriculum Content Design and Development - Delivery Systems and Environments - Educational Systems Design - e-Learning Organisational Issues - Evaluation and Assessment - Virtual Learning Environments and Issues - Web-based Learning Communities - e-Learning Tools - e-Education *e-Society - Global Trends - Social Inclusion - Intellectual Property Rights - Social Infonomics - Computer-Mediated Communication - Social and Organisational Aspects - Globalisation and developmental IT - Social Software - Smart City *e-Health - Data Security Issues - e-Health Policy and Practice - e-Healthcare Strategies and Provision - Medical Research Ethics - Patient Privacy and Confidentiality - e-Medicine *e-Governance - Democracy and the Citizen - e-Administration - Policy Issues - Virtual Communities *e-Business - Digital Economies - Knowledge economy - eProcurement - National and International Economies - e-Business Ontologies and Models - Digital Goods and Services - e-Commerce Application Fields - e-Commerce Economics - e-Commerce Services - Electronic Service Delivery - e-Marketing - Gig Economy - Online Auctions and Technologies - Virtual Organisations - Teleworking - Applied e-Business - Electronic Data Interchange (EDI) - Innovative Strategies - Business Intelligence - Information Intelligence - Forensic Accounting *e-Art - Legal Issues - Patents - Enabling technologies and tools *e-Science - Natural sciences in digital society - Biometrics - Bioinformatics - Collaborative research *Industrial developments - Trends in learning - Applied research - Cutting-edge technologies - Industrial Control Systems - Communications Compliance * Research in progress - Ongoing research from undergraduates, graduates/postgraduates and professionals SUBMISSION INSTRUCTIONS: * You can submit your abstract, extended abstract or paper online at http://www.i-society.eu/paper-submission/ or email it to papers(a)i-society.eu * You can submit your speaker's proposal via email at speakers(a)i-society.eu or online at http://www.i-society.eu/format/speakers-participation/ * You can submit your poster via email at posters(a)i-society.eu * You can submit your workshop or tutorial proposal via email at workshop(a)i-society.eu or tutorial(a)i-society.eu * You can submit your panel discussion via email at pandis(a)i-society.eu IMPORTANT DATES: *Abstract Submission Date: February 10, 2018 *Notification of Abstract Acceptance / Rejection: February 17, 2018 *Extended Abstract (Work in Progress) Submission Date: February 20, 2018 *Notification of Extended Abstract Acceptance / Rejection: February 27, 2018 *Research Paper Submission Date: March 01, 2018 *Notification of Research Paper Acceptance / Rejection: March 12, 2018 *Camera Ready Paper Due: May 01, 2018 *Proposal for Workshops / Tutorials: February 25, 2018 *Notification of Workshop/Tutorials Acceptance / Rejection: March 01, 2018 *Poster / Demo Proposal Submission: March 01, 2018 *Notification of Poster / Demo Acceptance: March 12, 2018 *Early Bird Registration Deadline (Authors and Participants): April 15, 2018 *Late Bird Registration Deadline (Authors only): May 15, 2018 *Late Bird Registration Deadline (Participants only): May 30, 2018 *Conference Dates: July 15-18, 2018 For more details, please visit www.i-society.euIf you wish to unsubscribe from our newsletter, click http://r.confinfosoc.org/scyaulavbnjg.html

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Interested in applying to the google summer of code
by Laouen Belloli 30 Jan '18

30 Jan '18

Hi, My name is Laouen Belloli, I'm a Computer Science student at Universidad de Buenos Aires currently doing my final thesis in Discrete Events Simulation, this is my 7th and last year on it. In the past I contributed to the cadmium project. This year, I want to join the google summer of code to contribute to Boost. In particular, I would like to work on the Boost.Real project proposed. Best regards, -- Laouen Mayal Louan Belloli. LIAA - DC - FCEyN - UBA. C.A.B.A. - Buenos Aires - Argentina. https://liaa.dc.uba.ar +54 9 11 38675694

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[atomic] (op)_and_test naming
by Andrey Semashev 30 Jan '18

30 Jan '18

Hi, I would like to ask for the community opinion on the naming of the (op)_and_test functions that appeared in Boost.Atomic 1.66. As you probably know, 1.66 included a few new atomic operations, some of which have the name (op)_and_test (e.g. add_and_test, sub_and_test, etc.) These operations perform the (op) on the atomic value and test if the result is zero, so that instead of this: if (a.fetch_sub(1) - 1 == 0) one could write this: if (a.sub_and_test(1)) Also, the generated code for these operations can potentially be more efficient. Recently I received this request: https://github.com/boostorg/atomic/issues/11 which basically asks to change the result of the functions to the opposite. I can see that the current naming could be confusing, especially given that other operations like bit_test_and_set return the previous bit value (i.e. true if the bit was 1). That would be a breaking change, but the new operations were announced as experimental in the release notes, so if there is consensus that the result should indeed be changed, I'm ready to comply. Another solution is change (op)_and_test naming to something else that is more clear. In that case I could deprecate the (op)_and_test variants and provide the functionality under the new names. I would welcome suggestions for a better naming scheme, if you feel this is the right way. My only ask is that the new names be concise, if possible. Lastly, if you think the current naming is fine or there is another way to resolve the confusion, please comment as well. I would appreciate your opinion in any case. Thanks.

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[review] Outcome v2: Review Period Concluded (Fri-19-Jan through Sun-28-Jan, 2018)
by charleyb123 . 29 Jan '18

29 Jan '18

Hi, Everyone-- The Boost Review Period for the formal review of Niall Douglas' Outcome (v2) library is concluded (having run Fri-19-Jan through Sun-28-Jan, 2018). Reviews were posted from: - Vinícius dos Santos Oliveira (Fri-26-Jan-2018) - Andrzej Krzemienski (Fri-26-Jan-2018) - Bjorn Reese (Sun-28-Jan-2018) - Daniela Engart (Sun-28-Jan-2018) - John P Fletcher (Sun-28-Jan-2018) In addition, online discussions included comments, observations, and critiques from a number of other community participants. It will take some time to review the discussion, make a final determination, and prepare the Review Report. Please: - Contact me (directly or on-list) if I missed identification of your review during the review period; - Contact me (directly or on-list) if you have any concerns; or to raise any salient observations or "final thoughts" Thank you! --charley Boost.Outcome(v2) Review Manager

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[gsoc18] Interested in adding statistics and machine learning functions to Boost.uBLAS and Seeking for mentors
by Kanch 29 Jan '18

29 Jan '18

Dear community: My name is Long Zhang,currently in my third year of college. As subject suggests, I'm interested in adding statistics and machine learning functions to Boost.uBLAS library. I've basic knowledge of statistics (which I have been thought in school) and Machine Learning, I learned Machine Learning by Andrew Ng on Coursera, and I have tried to implement algorithms like PCA,LDA,K-means in Python, therefore, I think it won't be a problem if I have to implements it in C++. BTW, I have use C++ since my Senior High. Except components mentioned in wiki, I think I can also implement algorithms like KNN,Logistic Regression, even SVM during the summer. I also understand the efficiency of these algorithms is what matters, I will try hard to implement it as fast as it can. I know I have do some kind of programming competency test. When should I start? I mean I haven't find a mentor, don't know who should I contact if I finish the test. Can someone mentoring me? We can then talk about the test and code I used written in C++(open source code in C++) to check if I'm qualified to this project. Thank you. Best, Long -- Best regards, *Long Zhang (Kanch) <http://akakanch.com> *＠ Chengdu University of Information Technology 2015 Computer Science Major Mail:kanchisme@gmail.com No.24 Block 1, Xuefu Road, Chengdu, Sichuan, China

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[outcome] Formal review
by Bjorn Reese 29 Jan '18

29 Jan '18

I. DESIGN --------- Boost.Outcome provides a useful alternative / complement to exceptions, and its design is clean. I like naming of functions with wide and narrow contracts. I suggest that result<> is renamed to basic_result<>, which will then be the customizable template class, and result<> then becomes as specialzation (template alias) that does the same as the current default result<>. This makes result<> an uncustomizable companion to std::error_code, which is useful when defining interoperable APIs. One design decision that I disagree with is the choice of sum types rather than product types for internal storage. I would rather have a lower run-time footprint at the expense of increased compile times. II. IMPLEMENTATION ------------------ Looks readable and solid. There may be an overemphasis on constexpr; I would rather have had support for C++11. BOOST_OUTCOME_TRY_UNIQUE_NAME generates identifiers starting with __t but according to the C++ standard [lex.name/3.1] "each identifier that contains a double underscore __ [...] is reserved to the implementation for any use", where implementation means the C++ compiler. III. DOCUMENTATION ------------------ The documentation is well-written, with a tutorial that is easy to understand. The API Reference could be improved though. 1. What are the requirements for ValueOrError? Looking up ValueOrError brings us to convert::value_or_error, which only states that it "matches the ValueOrError concept." The rather convoluted enable_if uses ValueOrError<U> which uses detail::ValueOrError<U> and here the trail disappears. The convert.hpp header file does contain the missing explanations though. 2. What are the requirements for EC and EP? EC and EP are used informally throughout the documentation, but are described in the Custom Payloads tutorial. In the API Reference they are suddenly called S and P instead. Please use a consistent naming throughout the documentation; preferably using more descriptive names, such as OutcomeErrorCode and OutcomeExceptionPtr. It would furthermore be helpful if they were described as concepts outside the tutorial. 3. The descriptions of value_type_if_enabled and error_type_if_enabled are obscure, and it is still not clear to me if they have any relevance for the library user. If they do, then their descriptions should be more clear; if they do not, then they should not be included in the documentation. 4. The documentation of OUTCOME_TRYX contains the full macro implementation which is not really helpful to users. This macro could possibly be expressed in terms of other macros. 5. noexcept('hidden') is used in several places. Does this mean that the noexcept condition is unspecified? If so, then it is more customary to use "unspecified" in italic. IV. MISC -------- I spent 4-5 hours reading the documentation and looking at the code. I did not compile it. V. VERDIC --------- I vote for the conditional acceptance of Boost.Outcome. The conditions are: 1. The documentation should be integratable into the Boost infrastructure. 2. People must be able to submit patches to the Boost version of the library without having to convert those patches to the standalone version.

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Fwd: Fwd: [review] Review of Outcome v2 (Fri-19-Jan to Sun-28-Jan, 2018)
by degski 28 Jan '18

28 Jan '18

---------- Forwarded message ---------- From: degski <degski(a)gmail.com> Date: 28 January 2018 at 17:11 Subject: Re: [boost] Fwd: [review] Review of Outcome v2 (Fri-19-Jan to Sun-28-Jan, 2018) To: Vinícius dos Santos Oliveira <vini.ipsmaker(a)gmail.com> On 28 January 2018 at 16:44, Vinícius dos Santos Oliveira < vini.ipsmaker(a)gmail.com> wrote: > Can you elaborate on your point? If I'm left alone I'll miss your point. > I was mostly just responding to your example (which you asked me to do), and how I would do that, without having to deal with exceptions and/or outcomes. But, the more general point is, which Spirit in this case does very well, is to deal with potential problems at the source, in an explicit (comprehensive) way, without propagation of errors or exceptions. > It's becoming confusing the more you go. > It's probably because I'm rowing against the tide here. degski

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Fwd: [review] Review of Outcome v2 (Fri-19-Jan to Sun-28-Jan, 2018)
by degski 28 Jan '18

28 Jan '18

Accidentally sent privately, forwarded below: ---------- Forwarded message ---------- From: degski <degski(a)gmail.com> Date: 28 January 2018 at 15:46 Subject: Re: [boost] [review] Review of Outcome v2 (Fri-19-Jan to Sun-28-Jan, 2018) To: Vinícius dos Santos Oliveira <vini.ipsmaker(a)gmail.com> On 28 January 2018 at 14:10, Vinícius dos Santos Oliveira < vini.ipsmaker(a)gmail.com> wrote: > 2018-01-28 12:12 GMT-03:00 degski via Boost <boost(a)lists.boost.org>: > >> 1. Use of outcome is more manual and cumbersome, i.e. more error-prone. >> > > What is complex about the following? > <snipped the code> I'd just use boost::cnv::spirit and specify explicitly what happens when conversion didn't work... much shorter, very well optimized (the best) when it does work (the conversion)... > Server side code... > There's more than servers in life. Handling f.e. O-O-M-situations is not gonna help me on my lap-top... a re-think and re-write of my app is in this case in order, though... or a trip to the shop and buy a bigger stick (both the "slow path"). > If the error is exceptional or not, it depends on context, not on the > algorithm (e.g. connection failure on game client code and game server code > and both of them being backed up by the same functions). Boost.Outcome > let's you do just that by converting an error into an exception. > Yeah, that's another discussion, isn't it? errors vs. exceptions. Should exceptions be exceptional, or getting back to your conversion example, should we use exceptions to indicate failure as this is the case in Boost::Lexical_cast? I know the answer I like best, and moved on to Boost.Spirit. degski

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[spirit-x3]What's use case for x3::variant<OnlyOneComponent>?
by Larry Evans 28 Jan '18

28 Jan '18

Since: http://www.boost.org/doc/libs/1_65_0/libs/spirit/doc/html/spirit/qi/quick_r… doesn't mention a unary variant: variant<A> and the comments in: https://github.com/boostorg/spirit/blob/develop/include/boost/spirit/home/q… indicates variant<T> is collapsed to T, why isn't the x3::variant here: https://github.com/boostorg/spirit/blob/develop/include/boost/spirit/home/x… declared as: template <typename L, typename R, typename ...Types> struct variant instead of: template <typename ...Types> struct variant which allows sizeof...(Types)==0 instead of the minimum size of 2? That would disallow the primary and factor using's here: https://stackoverflow.com/questions/43791079/x3-linker-error-with-separate-… which make no sense because, for example, primary_def is *not* an alternative parser. -regards. Larry

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Google Summer of Code with Boost
by David Bellot 28 Jan '18

28 Jan '18

Hi everyone, still a few days before we submit our proposal to Google. Don't loose the chance to become a mentor for Boost. It shines on your CV, it is a great opportunity to work with brilliant students around the world, it makes you an official C++ world-wide expert. So far, we have a nice but little list of proposals here: https://github.com/boostorg/boost/wiki/Boost-Google-Summer-of-Code-2018 It would be good to have a bit more before I go and submit to Google. This will increase our chances to be selected again this year. For Boost it's a great funding worth several thousand of dollars every year. We just don't want to miss it. Best regards, David

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[gsoc18] New Astronomy Library
by Pranam Lashkari 28 Jan '18

28 Jan '18

Boost has developed many libraries which is useful in the field of science. I would like to propose a library for "Astronomy" as a student. I have been an amateur astronomer since last 8 years and being a Computer Engineering student I will be able to develop this library with little mentoring. I have some ideas about what can be integrated into it, which I can propose if the proposal seems promising. If so are there anyone who can help me out with this and mentor me? Thank you, Pranam Lashkari

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[gsoc18] ublas project 3
by Aperjump 28 Jan '18

28 Jan '18

I'm Wei Wang, a CS master student focusing on high-performance computing field. `boost::ublas` project 3 adding GPU computation interests me a lot and I'd like to help add this feature to ublas. I find this project was also on last years' list and I'm curious if anyone did this before or on which stage he/she has finished. I've already read the initial source code of `ublas` in `boost 1.29`(I also read 1.66 API, and found it add one concept `container`, which used to be `bounded_array` and `unbounded_array`). I wrote a passage describing its template parameter deduction relationships. Besides, I wrote a series blogs teaching how to use openCL efficiently with proper data partition and memory usage. This is my first time participating in GSOC, and I'm a bit of confused on following question: 1. Integrating openCL requires preparing for context, command_queue, event and other "environment objects", should they also be included in this lib? 2. Take matrix matrix multiplication A*B for example. The last stage before matrix copy assignment is in `matrix_matrix_prob` class and its evaluation requires loop through all items on both matrix. If I want to add GPU compute features, I need to launch kernel for each computation expression at this step, but it seems to be contradictory to `ublas`'s lazy evaluation rationale. How to reconcile that? 3. What should I implement in the competency matrix class? Just integer matrix or template matrix class?Should I support current `ublas` interface(those typedefs and traits)? Best regards, Wei Wang -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Dev-f2600599.html

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Re: [boost] [review] outcome broken on clang/libstdc++ (Linux) and Apple clang/libc++ and gcc 7.2
by Glen Fernandes 28 Jan '18

28 Jan '18

I wrote a .travis.yml for your boost-outcome submission to run your unit tests against a few compilers: The output is at: https://travis-ci.org/glenfe/ned14.outcome/builds/334222400 I updated it to make sure the clang++-libstdc++ uses a more recent libstdc++. It looks like: - clang++-libc++ fails because of forgetting to #include a header. - GCC 7.2 with -std=c++17 is the one with the Internal Compiler Errors (I didn't investigate further) - clang++5-libstdc++ fails because it cannot find a type in std Is there a reason why you don't have travis and appveyor for boost-outcome? I remember your "Best Practices" document strongly advocating that every Boost library submission should have them. Glen

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Re: [boost] [review] outcome broken on clang/libstdc++ (Linux) and Apple clang/libc++ and gcc 7.2
by Glen Fernandes 27 Jan '18

27 Jan '18

On Sat, Jan 27, 2018 at 4:55 PM, Glen Fernandes wrote: > I just tried boost-outcome unit tests with clang 4.0, 5.0 on Linux > with libstdc++ with -std=c++14 and -std=c++1z which fails with many > errors: > > e.g. [snip] > In file included from > libs/outcome/test/tests/../../include/boost/outcome/detail/result_storage.hpp:34: > libs/outcome/test/tests/../../include/boost/outcome/detail/../success_failure.hpp:54:42: > error: no template named 'conditional_t' in namespace 'std'; did you > mean 'conditional'? > template <class T> using devoid = > std::conditional_t<std::is_void<T>::value, void_type, T>; > ~~~~~^~~~~~~~~~~~~ > conditional > /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/type_traits:1780:12: > note: 'conditional' declared here > struct conditional > ^ > > > Then I also tried the boost-outcome unit tests with Apple clang 8.1.0 > with libc++ with -std=c++14 and -std=c++1z which fails with errors > like: > I pasted the wrong error output here; the right error output is: clang-darwin.compile.c++ bin.v2/libs/outcome/test/core-outcome.test/clang-darwin-4.2.1/debug/cxxstd-14-iso/tests/core-outcome.o In file included from libs/outcome/test/tests/core-outcome.cpp:30: In file included from libs/outcome/test/tests/../../include/boost/outcome/outcome.hpp:34: In file included from libs/outcome/test/tests/../../include/boost/outcome/detail/outcome_exception_observers.hpp:34: In file included from libs/outcome/test/tests/../../include/boost/outcome/detail/result_storage.hpp:35: libs/outcome/test/tests/../../include/boost/outcome/detail/value_storage.hpp:181:22: error: no matching constructor for initialization of 'value_type' (aka 'boost::outcome_v2::outcome<int, std::__1::error_code, std::exception_ptr, boost::outcome_v2::policy::error_code_throw_as_system_error<int, std::__1::error_code, std::exception_ptr> >') new(&_value) value_type; // NOLINT ^ libs/outcome/test/tests/../../include/boost/outcome/detail/result_storage.hpp:270:11: note: in instantiation of member function 'boost::outcome_v2::detail::value_storage_nontrivial<boost::outcome_v2::outcome<int, std::__1::error_code, std::exception_ptr, boost::outcome_v2::policy::error_code_throw_as_system_error<int, std::__1::error_code, std::exception_ptr> > >::value_storage_nontrivial' requested here : _state(std::move(o._state)) ^ > Is this also a known issue? Only gcc 6 and gcc 7 with lisbtdc++ on > Linux seem to pass. The other combinations I tried (clang + lisbtdc++ > on Linux, Apple clang + libc++) do not. > I spoke too soon, here gcc 7 does not pass. It ICEs: libs/outcome/test/tests/../../include/boost/outcome/detail/result_value_observers.hpp:45:17: in constexpr expansion of ‘((boost::outcome_v2::detail::result_value_observers<boost::outcome_v2::detail::result_storage<int, std::errc, boost::outcome_v2::policy::error_code_throw_as_system_error<int, std::errc, void> >, int, boost::outcome_v2::policy::error_code_throw_as_system_error<int, std::errc, void> >*)this)->boost::outcome_v2::detail::result_value_observers<boost::outcome_v2::detail::result_storage<int, std::errc, boost::outcome_v2::policy::error_code_throw_as_system_error<int, std::errc, void> >, int, boost::outcome_v2::policy::error_code_throw_as_system_error<int, std::errc, void> >::<anonymous>.boost::outcome_v2::detail::result_storage<int, std::errc, boost::outcome_v2::policy::error_code_throw_as_system_error<int, std::errc, void> >::result_storage<int>(boost::outcome_v2::in_place_type_t<int>(), <anonymous>)’ libs/outcome/test/tests/core-result.cpp:330:41: internal compiler error: in adjust_temp_type, at cp/constexpr.c:1206 constexpr result<int, std::errc> a(5), b(std::errc::invalid_argument); [...] 0x6db788 cxx_eval_constant_expression ../../src/gcc/cp/constexpr.c:4034 Please submit a full bug report, with preprocessed source if appropriate. Please include the complete backtrace with any bug report. See <file:///usr/share/doc/gcc-7/README.Bugs> for instructions. Let me know if you need more context, but it appears boost-outcome is also broken on gcc 7.2. Glen

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Re: [boost] [review] outcome broken on clang with libstdc++ (Linux) and Apple clang with libc++
by Glen Fernandes 27 Jan '18

27 Jan '18

On Sat, Jan 27, 2018 at 3:07 PM, Niall Douglas wrote: > b2 libs/afio/test works fine with VS2017. So it would seem that that ICE > Vinnie encountered is some weird corner case nobody could have > anticipated. As I mentioned, almost all of the development of Outcome > was done on MSVC. It's very well tested on MSVC, and I've never seen > anything like that ICE before. I just tried boost-outcome unit tests with clang 4.0, 5.0 on Linux with libstdc++ with -std=c++14 and -std=c++1z which fails with many errors: e.g. In file included from libs/outcome/test/tests/comparison.cpp:35: In file included from libs/outcome/test/tests/../../include/boost/outcome/outcome.hpp:34: In file included from libs/outcome/test/tests/../../include/boost/outcome/detail/outcome_exception_observers.hpp:34: In file included from libs/outcome/test/tests/../../include/boost/outcome/detail/result_storage.hpp:34: libs/outcome/test/tests/../../include/boost/outcome/detail/../success_failure.hpp:54:42: error: no template named 'conditional_t' in namespace 'std'; did you mean 'conditional'? template <class T> using devoid = std::conditional_t<std::is_void<T>::value, void_type, T>; ~~~~~^~~~~~~~~~~~~ conditional /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/type_traits:1780:12: note: 'conditional' declared here struct conditional ^ Then I also tried the boost-outcome unit tests with Apple clang 8.1.0 with libc++ with -std=c++14 and -std=c++1z which fails with errors like: clang-darwin.compile.c++ bin.v2/libs/outcome/test/outcome-int-int-1.test/clang-darwin-4.2.1/debug/cxxstd-14-iso/outcome-int-int-1.o libs/outcome/test/compile-fail/outcome-int-int-1.cpp:12:26: error: no matching constructor for initialization of 'outcome<int, int, int>' outcome<int, int, int> m(5); ^ ~ libs/outcome/test/compile-fail/../../include/boost/outcome/outcome.hpp:222:31: note: candidate constructor (the implicit copy constructor) not viable: no known conversion from 'int' to 'const boost::outcome_v2::outcome<int, int, int, boost::outcome_v2::policy::all_narrow>' for 1st argument class BOOST_OUTCOME_NODISCARD outcome ^ Is this also a known issue? Only gcc 6 and gcc 7 with lisbtdc++ on Linux seem to pass. The other combinations I tried (clang + lisbtdc++ on Linux, Apple clang + libc++) do not. Glen

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Re: [boost] [review] outcome broken on MSVC, plus questions
by Glen Fernandes 27 Jan '18

27 Jan '18

Hi Niall, Still working on the review; I had the following questions while reading the threads: 1. Which versions of MSVC 2017 does boost-outcome not work on, right now? 2. According to the documentation, outcome and boost-outcome both require MSVC 2017, right? i.e. They do not support MSVC 2015 or lower? 3. Is standalone outcome fine with MSVC2017, only boost-outcome that is broken? 3.1. If so, is it right that the boost-outcome repository is "generated" from the outcome repository? And is that the reason that boost-outcome is broken on MSVC 2017? 4. Would you happen to know how does your outcome/result compare to Peter's outcome/result in variant2? (I saw you point out that Peter implemented expected, and then I saw he also had an outcome/result implementation in variant2). 4.1. What different compilers and standards does his support compared to yours? 4.2. What kind of code is generated from his implementation compared to yours? Thanks, Glen

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[outcome] Purpose of value_type_if_enabled?
by Bjorn Reese 27 Jan '18

27 Jan '18

Are value_type_if_enabled and error_type_if_enabled supposed to be used by the library users? If so, how?

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[spirit]why x3::alternative::parse not short-circuited?
by Larry Evans 27 Jan '18

27 Jan '18

https://github.com/boostorg/spirit/blob/develop/include/boost/spirit/home/x… shows both left.parse *and* right.parse are called. Shouldn't right.parse be skipped if left.parse succeeds?

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[outcome] Andrzej's review
by Andrzej Krzemienski 27 Jan '18

27 Jan '18

Hi Everyone, This is my review of Boost.Outcome v2. The library should be *accepted* subject to conditions that I list down below. What is your evaluation of the design? Clean and logically divided. What is your evaluation of the implementation? > Some bugs aside, it is clean and well structured. I was able to read it and understand how things work. I will be filing bugs in GitHub. What is your evaluation of the documentation? > Good. You can get the idea what the library is doing and how you can use it. But I should mention that I wrote some pieces thereof, so my opinion is likely biased. The docs need some modifications before they can get into Boost. I mean macro names, and the technology required to build it. What is your evaluation of the potential usefulness of the library? > I find the library very useful in certain domains. I myself have found two applications in my job project, and they are not really related to light-speed efficiency: 1. We have a task scheduling framework built atop ASIO, and signalling failures through exceptions makes the code really difficult to read because try-catch blocks need to work as control statements. Also, we cannot pass them by exception_ptr as sometimes we need to classify the kind of failure to determine if we want to deal with it in the framework, or if we want to forward them to the user. 2. I have a validation routine that validates (and parses) the input data written using some syntax. I wan the syntax-errors in input files to be forwarded as failed `result`s (no exceptional about these), but other errors like memory shortage during the file parsing to be signaled via exceptions (and I will probably kill the module in response). Why accepting this library when we have `expected` being standardized? I do not really mind having two in Boost. First, it is ready, being proposed, and applied in a number of non-trivial code-bases. Niall claims that his trade-offs are better tailored to predictable-latency applications. I do not have enough knowledge to asses it. They look convincing. The only way to test it is to give this library the Boost blessing and have the user test it. I am bought by the TRY operations, and the upgrade to `outcome` looks really convincing. Did you try to use the library? With what compiler? Did you have any > problems? > Yes. A lot of compilers. For instance GCC 6.4.0, also different GCC and Clang versions in WandBox. No problems encountered. How much effort did you put into your evaluation? A glance? A quick > reading? In-depth study? > I have read most of the final implementation. I have read many versions of the documentation. I have spent a lot of time (prior to the review) asking Niall lots of questions about the details. I have also built lots of small examples to test the library and some corner cases. Are you knowledgeable about the problem domain? > I do report failures (by different means) in my programs. I have given it quite some thought. I am well familiar with implementation and formal specification of `boost::optional` and `std::optional` which had to address some similar implementation problems. Do you think the library should be accepted as a Boost library? > Yes, conditionally. Here are three conditions: 1. Documentation is adjusted to use boost-standard names of macros and namespaces. Also, it is not clear if Boost release process is capable of handling the technology that Niall has chosen. If not, the contents of documentation should be migrated to another format, manageable by Boost release process. 2. Because there has been some confusion around the meaning of storing default-constructed `std::error_code` (is it an error or lack thereof?) and `std::exception_ptr` (e.g., see this issue: https://github.com/ned14/outcome/issues/115) I request that you state in the docs, before the API Reference how library treats default-constructed values of `EC` and `EP`. For instance, you can say "default-constructed error_code is considered an error, and treated as such by the library", or "the library sometimes may make use of the fact that a default-constructed EC/EP is not an error, so make sure not to pass us such values": I am fine with any answer, but I need you to spell it out, so that I know what to expect. 3. Similarly, I request that you put in the docs what is the "value" of an object of type `outcome<>` or `result<>` in the sense in which John Lakos talks about "salient attributes". I know that T, EC, and EP constitute the value. But in the middle of the tutorial we learn that apart from these you also store "spare_storage" -- is it also included in copying and comparisons? API reference on `operator==` only says "compares if two objects are equal", but it is not that clear what it means. Also, what does it mean that result is equal to optional. Define it somewhere and paste links to it. Finally, I wan to thank Niall for his now many-year effort to deliver this really cool library to the community. Regards, &rzej;

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Re: [boost] [review] Outcome: internal compiler error
by Vinnie Falco 27 Jan '18

27 Jan '18

On Thu, Jan 18, 2018 at 2:07 PM, charleyb123 . via Boost <boost(a)lists.boost.org> wrote: > GitHub: > *- https://github.com/ned14/boost-outcome > > Please post your comments and review to the boost mailing list > (preferably), or privately to the Review Manager (to me ;-). Here are some > questions you might want to answer in your review: I have put together the following sample program to test integration of Outcome into Boost.Beast: #include <boost/outcome.hpp> int main(int argc, char** argv) { } The result of compilation for this translation unit is shown here: 1>c:\users\vinnie\src\boost\boost\outcome\detail\value_storage.hpp(141): 1>fatal error C1001: An internal error has occurred in the compiler. 1>(compiler file 'msc1.cpp', line 1507) Compiler used: MSVC Part of: Microsoft Visual Studio Community 2017 Version 15.5.1 Upon investigation, I discovered a newer version of the compiler and IDE. Updating to "Version 15.5.5" produced the following results when compiling the same translation unit: 1>c:\users\vinnie\src\boost\boost\outcome\detail\value_storage.hpp(141): 1>fatal error C1001: An internal error has occurred in the compiler. 1>(compiler file 'msc1.cpp', line 1507) Is this a supported configuration? Thanks

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[review] outcome
by Vinícius dos Santos Oliveira 27 Jan '18

27 Jan '18

That is my review of Boost.Outcome. What is your evaluation of the design? Niall did an excellent job weighting trade-offs and coming up with such an pleasant and convenient interface that not only is convenient, but it has customization points in the appropriate layers to fit not-close-to-trivial use cases. I've read the changes between v1 and v2 and I agree with the rejection reasons of previous version (the v1's null state specially made little sense at all). Version 2 is a very realistic and solid project. It might seem teasing to just port abstractions from functional languages to C++ (e.g. Expected), but C++ is its own beast and we cannot just ignore some features that we have been dragging all along like exceptions if we expect to have any realistic usage in the real world. Niall's intuition on how to weigh trade-offs was outstanding and just proves his C++ familiarity and expertise. In special, default actions/behaviours could only be defined by intuition of some experienced programmer and not "mathematically". What is your evaluation of the implementation? I did not check the implementation. What is your evaluation of the documentation? Very well written. The tutorials are excellent-quality. The use cases and examples were chosen in such a way that it was intuitive to understand why/when Boost.Outcome and not Expected. I noted a few small problems, but they were reported already. The comments on the example codes were seemingly foreseeing ahead enough about "pumping doubts" so that my mind would calm down and actually pay attention to the documentation instead doing mind exercises trying to guess the non-point of the example. I wish I had this skill. What is your evaluation of the potential usefulness of the library? Very useful. Error handling is a core constant in any programming activity. Introduction of Boost.Outcome could potentially remove duplication of throwing and non-throwing APIs. I personally prefer Expected with its monadic operations, but it is unrealistic to ignore exceptions in many code bases and I'd certainly go for Boost.Outcome in these cases. Did you try to use the library? With what compiler? Did you have any problems? Yes. The one-header version of the library made testing incredibly easy. No problems. Clang 5.0.1. How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? A few hours over a span of a few days. I've tried to examine documentation carefully and end up sending a pull request and a few comments to ask for further changes. I've read all threads that came up during review. I also tested the library when in doubt. Are you knowledgeable about the problem domain? I worked for more than one year under contract using the Rust programming language and Boost.Outcome is pretty much the error system we have in Rust (with some C++-ification and an experienced C++ unique programmer "intuition" to also cover exceptions... and w/o monad ops, of course). Do you think the library should be accepted as a Boost library? Yes. -- Vinícius dos Santos Oliveira https://vinipsmaker.github.io/

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[config] Positive feature macros, r2
by Peter Dimov 26 Jan '18

26 Jan '18

I'd like to revisit the topic of Boost.Config feature macros, specifically that in my opinion, positive feature macros (BOOST_CXX17_FEATURE) make more sense than negative macros (BOOST_NO_CXX17_FEATURE) in the current environment. Negative macros made sense in the past when they signified bugs and deficiencies in the compiler as measured against a static standard. Nowadays, the standard, such as it is, is in constant motion and macros indicate merely a current state of development for both the compiler and the standard. The arguments for positive macros are the same as last time: - adding a new negative macro requires changes to all legacy compilers that do not and will never implement the feature; a positive macro only requires changes to active compilers. - positive macros are a better match for the standard feature macros, which are positive. When we see a standard feature macro being set, we typically would set ours as well. This means that the amount of changes required to add a new macro is further reduced; we only need to touch compiler-specific config files if the compiler either does not implement feature macros, or sets them incorrectly (in our considered opinion.) TL;DR we should switch to positive feature macros in Boost.Config, and delaying this switch just accumulates more unnecessary code in Boost.Config.

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[gsoc18][ublas] Proposal to add advanced matrix operations
by SHIKHAR SRIVASTAVA 26 Jan '18

26 Jan '18

Hi everyone, I am a 4th year undergraduate student pursuing a degree in Computer Science and Engineering. I have strong programming experience in C++ through internships, self projects and programming events. I wish to be a part of gsoc18 under boost and am particularly interested in the linear algebra library Boost.ublas. The ublas library can be made more useful for Machine Learning applications like recommendation systems, clustering and classification, pattern recognition by adding some operations required in those. I propose to add advanced matrix operations to ublas including - 1. Triangular Factorisation (LU and Cholesky) 2. Orthogonal Factorisation (QR and QL) 3. Operations to find Singular Value lists 4. Eigenvalue algorithms 5. Singular Value Decomposition (SVD) 6. Jordan Decomposition 7. Schur Decomposition 8. Hessenberg Decomposition This is a very brief description of what I would like to propose. Any suggestions that help in refining the requirements before making a draft proposal would be great. Regards Shikhar Srivastava Github: https://github.com/shikharsrivastava

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[outcome] success-or-failure objects
by Vinícius dos Santos Oliveira 26 Jan '18

26 Jan '18

I'm liking what I saw so far. Just a small comment on the documentation. I'm curious what the following sentence does even mean? Is it supposed to confuse the user or something? It's a sign of bad taste really. >Outcome’s default is to not provide value-or-error objects. It provides success-or-failure objects. What does that even mean? value-or-error... well, if it is non-error, I assume it is success. Both sentences mean just the same. As do their API (encapsulate either A or B). The rest of the paragraph is okay. If you just remove this comment, confusion will go away. No other changes need to be done in this paragraph. Just remove this misleading means-nothing comment. -- Vinícius dos Santos Oliveira https://vinipsmaker.github.io/

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[Root Pointer] Deterministic C++ memory manager (update)
by Phil Bouchard 26 Jan '18

26 Jan '18

Greetings, I wanted to give an update to the community regarding the memory manager I wrote called: Root Pointer. I now have a working template to solve all memory leaks in C++ and C but both requires some meta data generator. The code can be found here; it is working but not polished: https://github.com/philippeb8/root_ptr In this code we can find: - node_ptr: main class of the smart pointer / memory manager. - root_ptr: generic derived class that includes an "iterator" and a pointer to the name of the instance (for debugging purposes). Also I commented some code that logs the exact location of the memory leak. Furthermore I would like to bring some observations that I found in the C and the C++ language: - Pointers and iterators are not the same; i.e. pointers should point to allocated blocks only and shouldn't have arithmetic operators while iterators shouldn't be used to deallocate anything. - C pointers can only point to dynamic arrays (size known at run-time). - C++ pointers can point to both inherited objects and static arrays (size known at compile-time). This creates a problem (see attached: array_inherited_pointer.cpp). - std::array<T> should have constructors with T objects that have no default constructor. Lastly, before I submit anything, I will have to propose a way to apply a template function to all non-static member variables of a class. This will require implicit meta data generation. This idea is not new as other libraries such as Qt is based on meta data and they certainly could make us of this. For the moment I have a parser that does the job correctly by specializing a boost::proxy() template function but eventually this will have to be integrated into the standards. Hopefully this is an important milestone! Regards, Phil Bouchard www.fornux.com

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clang-format file
by Damian Vicino 25 Jan '18

25 Jan '18

Hi, I was wondering if someone has a .clang-format file that works fine to check boost code. I looked into the github repositories, but I couldn't find any. Best regards, Damian

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[outcome] Some documentation suggestions
by Vinícius dos Santos Oliveira 24 Jan '18

24 Jan '18

Maybe I could send some PRs later (I've already sent one a few moments ago). But, for now, I'll have to postpone. Notes: - You put too much focus in "open (error) type hierarchies" (e.g. `error_code`). Not a problem. Also, do not change anything just because this comment. Really, it is not a problem. - The beginning of the documentation gave me the impression that I could only use EC types that were convertible to `std::error_code`[1], “it need in fact to merely satisfy trait::has_error_code_v<EC>”. Later pages corrected my understanding. - “only works when the EC type is the same in the try expression as the calling function”[2] is misleading. `OUTCOME_TRYV(outcome::result<int, err>{err::success})` works inside a function returning `outcome::result<void>` given `err` is convertible to `std::error_code`. [1] https://ned14.github.io/outcome/tutorial/payload/ [2] https://ned14.github.io/outcome/tutorial/default-actions/error-codes/ -- Vinícius dos Santos Oliveira https://vinipsmaker.github.io/

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[outcome] comments on Regular ops
by Andrzej Krzemienski 24 Jan '18

24 Jan '18

Hi Everyone, This is not my final review (yet), but I wanted to raise some issues with Regular ops: comparisons and swap. 1. Comparisons. Equality comparison for `result` makes a strange choice for `T`s without comparisons: two such `result<T>`s just compare unequal. This is somewhat contradictory to semantics of Regular types. For value-semantic types we expect that a copy of the original object `x` compares equal to `x`: ``` int i = 1; int j = i; assert (i == j); ``` For some types, copy-construction makes a copy with the same value, but there is no way to define operator==. In this case, in order not to confuse anyone operator== is simply not provided: ``` using transformation = std::function<int(int)>; transformation f = [](int i) { return i; }; transformation g = f; // assert (f == g); <-- does not compile ``` And now, when we wrap it into `result`, we get: ``` // continuing previous example: out::result<transformation> of = f, og = g; f == g; // <-- compiles fine, returns false. ``` Now you are just telling lies. Two objects have the same value, yet they compare unequal! Here is a live example: https://wandbox.org/permlink/I hqgXDfHW6WqAXHW My recommendation would be not to provide comparison operators if either `T` or `EC` does not provide them. 2. Swap For non-trivially-copyable types, it looks like (similarly to std::variant) `result` cannot provide the strong exception safety guarantee. You may need to both move-construct `T` and `EC` and both can fail. ``` void swap(result &o) noexcept(detail::is_nothrow_swappable<value_type>::value // &&detail::is_nothrow_ swappable<error_type>::value) { using std::swap; #ifndef BOOST_NO_EXCEPTIONS this->_state.swap(o._state); try { swap(this->_error, o._error); } catch(...) { swap(this->_state, o._state); throw; } #else swap(this->_state, o._state); swap(this->_error, o._error); #endif } ``` The trick with catch-reswap-rethrow assumes that `T` is more likely to throw while swapping/moving than `EC`, but it might be quite the opposite. Also, it is possible that while reswapping, another exception will be thrown. In general, you cannot guarantee the roll-back, so maybe it would be cleaner for everyone if you just declared that upon throw from swap, one cannot rely on the state of `result`: it should be reset or destroyed. Another problem is that in the noexcept() clause you are mentioning is_nothrow_swappable<value_type> and is_nothrow_swappable<error_type>, but in the implementation you might be using move constructors rather than swaps. This means that for types that do not throw in swap but throw in move constructor (like std::list), a throw from move constructor will cause a call to `std::terminate`. See live example here: https://wandbox.org/permlink/8jIyb0fx7U72cZSt The noexcept clause should be extended to include move-constructors. This is the case for `std::optional`. Regards, &rzej;

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yomm2 - open methods
by Jean-Louis Leroy 24 Jan '18

24 Jan '18

Hi, in 2013 I posted a proposal for an "open multi-methods" library, see here: https://lists.boost.org/Archives/boost/2013/07/205383.php Due to insufficient interest, I did not go forward with a formal submission, and I published my work on github, under the name yomm11. I have now completely rewritten the library. The new version - yomm2 - is available here: https://github.com/jll63/yomm2 This iteration is much better because it does not require any modifications to classes involved in method dispatch, yet the speed of a method call with one virtual argument is within 15% of the equivalent virtual function call. Over the years I realized that the value of such a library resides more in the 'open' than in the 'multi' aspect. Open methods are virtual functions that live outside classes, like free functions. They solve several problems, notably the Expression Problem (http://wiki.c2.com/?ExpressionProblem) and Cross-Cutting Concerns (http://wiki.c2.com/?CrossCuttingConcern) They provide an elegant replacement for the Visitor pattern. yomm2 also implement multiple dispatch, which can come (occasionally) handy. Well I am just touching base to see if things have evolved and if there might now be an interest in seeing this in Boost. Jean-Louis Leroy

3 12

Contributing in the algorithm library
by Surayans Tiwari 24 Jan '18

24 Jan '18

Hello Boost Community! My name is Surayans Tiwari currently pursuing Bachelors of Engineering at BITS Pilani, India . I am an algorithms enthusiast and c++ programmer with 3 years of experience coding in the language. I want to get a head start on how to add new modules in algorithm library of boost. Please can someone help me with this. Thank you. ‌

4 10

[outcome] Whether to default EC = error_code for result?
by Niall Douglas 23 Jan '18

23 Jan '18

Just wondering what the reviewers' opinion is on the choice by Outcome to default `result<T, EC = std::error_code>`? That made sense back when Boost.System's error_code aliased `std::error_code` when being compiled under C++ 11 or better (i.e. always in the case of Outcome). But now that Boost.System's error code looks to be becoming a superset of `std::error_code`, I am now wondering whether to no longer default it at all to anything. Arguments in favour of this: 1. Expected no longer defaults E to anything, thus avoiding including <system_error> which drags in <string> and imposing compile time costs on those who don't use <system_error>. I did some more benchmarking, on a recent GCC on a 4Ghz CPU it's about 0.6 secs per compiland being added on Linux, and more like a second on Windows with MSVC. 2. As is pretty clear from the tutorial, we expect all non-trivial uses of Outcome to typedef `result` into the local namespace anyway. So defaulting `EC` only really benefits trivial use cases. 3. I think it now inevitable I need to go implement a much lighter weight <system_error2> without the problems with <system_error> (e.g. header only use problems, heavy includes, underspecified semantics, hardcoded use of `int`, memory allocation and so on). I'll send it to SG14 for them to get it into the standard if they like it (they will, it'll tick all their boxes, WG21 may be more challenging). Arguments against this: 1. Use of `std::error_code` ought to be encouraged rather than UDTs such that Outcome using code is not anti-social to other code. Defaulting the type sends a clear message on this. 2. Removing the defaulted `EC` on `result` is asymmetrical to defaulting `EC` and `EP` on `outcome`. I personally don't mind it, different typical use cases means different defaults, but others may find the asymmetry upsetting. 3. The relevant policies need to include `<system_error>`, otherwise they don't compile. So the include of `result.hpp` would need to be split into a `result.hpp` and a `error_code_support.hpp` with the latter containing the `<system_error>` stuff. Thoughts? Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

2 2

23 Jan '18

While refactoring the test Jamfile for Boost.System, I wrote this rule: rule system-run- ( sources + ) { local result ; result += [ run $(sources) : : : <link>static : $(sources[1]:B)_static ] ; result += [ run $(sources) : : : <link>shared : $(sources[1]:B)_shared ] ; result += [ run $(sources) : : : -<library>/boost/system//boost_system <define>BOOST_ERROR_CODE_HEADER_ONLY : $(sources[1]:B)_header ] ; return $(result) ; } to avoid repeating each test three times. The inconsistency is somewhat annoying. We could normalize the third line by introducing a third link type, <link>header, in response to which the library can switch to header-only mode. This is more or less the same suggestion as Niall's _hl targets from the CMake discussion, but it fits Boost.Build better, because the <link> property is automatically propagated to dependencies. Furthermore, after thinking about it a bit, I think that we might even have room for a fourth link type, <link>source, in response to which the library target would pass an appropriate <source> usage-requirement upwards. (<source>error_code.cpp in Boost.System's case.) <link>source is kind of best of both worlds, as it doesn't reparse the source code each time the library is used, and at the same time is not prone to the ODR violations introduced by inadvertently compiling the library and the executable with different, ABI-incompatible options. Comments?

2 4

[git][releases] removing beta tags
by Raffi Enficiaud 22 Jan '18

22 Jan '18

Hi all, I would like to know if it is allowed to delete the git tags that are associated to beta releases (such as "boost-1.45.0-beta1"). Thanks, Raffi

2 2

[trac] email notifications?
by Raffi Enficiaud 22 Jan '18

22 Jan '18

Hi, Is trac sending email notification on comments and changes regarding tickets? It used to do so, but I am not receiving anything. I am asking because I am waiting for ppl to comment on the tickets for some time. If people do not receive email notifications, I think I will wait for ever. Thanks, Raffi

2 2

[trac] new versions of boost
by Raffi Enficiaud 22 Jan '18

22 Jan '18

Hi there, Would it be possible to add the next versions of boost to trac/milestones ? Thanks! Raffi

7 12

[system] Would it be possible to trial a breaking change to Boost.System and see what happens?
by Niall Douglas 22 Jan '18

22 Jan '18

SG14 the low latency study has been looking into how to improve some design decisions in <system_error>. The relevant WG21 paper is https://wg21.link/P0824 and recent discussion can be found at https://groups.google.com/a/isocpp.org/forum/#!topic/sg14/j7tQybEjP5s. What we'd like to do is to test whether some very mildly breaking changes to <system_error> are so mild as to affect no users, and on that basis propose WG21 to make those mildly breaking changes to <system_error> in the next C++ standard. And to test this, we'd like to modify Boost.System with those mildly breaking changes, ship a release and see how many users complain. If it is zero, we have evidence for WG21 that this is not a consequential change. What we'd like to change is this: 1. Stop treating code zero as always meaning success irrespective of category. This remedies a defect where some custom error code domains cannot be represented by error_code due to using value 0 for an error. In actual code, I've never seen anyone ever use comparison to anything but a default constructed error code, so I think this will be safe. 2. Success becomes solely the default constructed error code, which is code zero and a new category of "null_category". This is internally represented by { 0, nullptr }, and thus makes the default constructor trivial which is highly desirable as it eliminates any compiler magic static fencing for the default constructor. Right now the default constructor uses system_category with value 0, and I suspect no code will notice this change either. 3, Make the default constructor constexpr, now possible. No code should notice a difference, except less runtime code will be generated. 4. error_code::message() returns a std::string_view instead of std::string if running C++ 17 or better. This lets us remove the <string> dependency, and thus stop dragging in half the STL with <system_error> which in turn makes <system_error> actually useful to the embedded systems crowd. The guess here is that std::string_view has such excellent interoperation with std::string that I think 99% of code will compile and work perfectly without anybody noticing a thing. I appreciate that this would undo Peter Dimov's excellent work at having Boost.System alias <system_error> under C++ 11 and later. I also appreciate that we are deliberately going to potentially break end user code. But my personal guess is that in practice, the breakage will not be noticed by 99% of code out there right now. It'll just compile against the improved Boost.System and everything will work as before. Boost was originally intended as an incubator for C++ standard changes. This ticks that box perfectly. Thoughts on feasibility? Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

15 76

Travis CI Resources
by James E. King, III 22 Jan '18

22 Jan '18

Last summer we had a discussion about Travis CI Resource Usage for boostorg. Originally the discussion was about purchasing more resources; however the discussion quickly focused on finding the root cause of the backlog. The desire is to ensure that pull requests submitted to repositories are processed in a timely manner. This is not happening, and there is at least a 12 hour backlog on pull request builds for boostorg right now. Summarizing the discussion back then, it was proposed that the backlog was caused by folks working on feature branches directly in their boostorg repository, with the Travis CI setting enabled to "build branch updates". The proposed solution was to encourage everybody to fork their repository and set up their own Travis CI and Appveyor under their account, and work feature branches on your fork. If working alone, this is efficient for everyone as we all end up with faster builds because your account will not contend with boostorg for resources. So please, use your personal account to build up features if you can. Additionally, tuning your Travis CI build script to do a little bit less work will help. If you have a script that builds with gcc, gcc-5, gcc-6, gcc-7, clang, and cxxstd of 03,11,14,1z - for most libraries that are at the c++03 language level this is going to be significant overkill for use as a pull request gate. In the example above, there are 20 builds to do; double that if you build debug and release variants. If each build takes just 2 minutes that's still an 80 minute CI cycle. Please spend some time reviewing your practices around the use of the free CI resources we all share. Thanks, Jim

5 11

[config] Supporting newer compilers: what does it take?
by Olaf van der Spek 22 Jan '18

22 Jan '18

Hi, What does it take to support new compilers, especially MSVC? 15.6 Preview 1 has been released now. Is some documentation or policy regarding test runners etc available? https://blogs.msdn.microsoft.com/vcblog/2017/12/19/c17-progress-in-vs-2017-… Gr, -- Olaf

1 1

[gsoc18] RSS
by Greger 22 Jan '18

22 Jan '18

Got some code/idea for RSS. possibly an GSoC18 topic?anyone? br g

2 3

[bjam] Can I disable a test based on an environment variable?
by James E. King, III 21 Jan '18

21 Jan '18

I'd like to disable some serialization tests if I am running a ubsan build on travis. Is there a way in the Jamfile I can make it conditional on an environment variable, or should I define something like BOOST_DATE_TIME_UBSAN and put "if !defined" in the appropriate tests?

2 2

[gsoc2018] Dynamic Shortest Path Tree
by a.i＠acm.org 21 Jan '18

21 Jan '18

Hi, I am Donghyuk Kim, a Ph.D. Student at Korea Advanced Institute of Science and Technology. I tried to contribute something last year but was not able to start the project for some reason. So I am about to re-try again this year. What I would like to contribute is a specific algorithm, "Dynamic Shortest Path Tree" which is simply, a dynamic version of Dijkstra's algorithm. It is a tree-based data structure to maintain single-source to all destination shortest paths and known to outperform Dijkstra or A* where the insertion and deletion of vertex/edge frequently occur. The concept of "Dynamic Shortest Path Computation" was originally introduced in [Fully Dynamic Algorithms for Maintaining Shortest Paths Trees] by D. Frigioni, et al. (http://dl.acm.org/citation.cfm?id=338900) I have already implemented a working prototype for my research, but unit test, coding style unification, and much more c++ style modifications are required for the general purpose. I hope someone finds it interesting and be a mentor on this journey. Thanks in advance. Best Regards, Donghyuk Kim a.i(a)acm.org _____________________________________ Sent from http://boost.2283326.n4.nabble.com

2 1

[gsoc18] SafeFloat proposal
by Damian Vicino 21 Jan '18

21 Jan '18

Hi, I added a proposal to get SafeFloat ready for review: https://github.com/boostorg/boost/wiki/Boost-Google-Summer-of-Code-2018#3-b… This was a project I started in gsoc2015 as student mentored by Robert Ramey. Please contact me if you are interested in further details. Best regards, Damian Vicino

2 1

Google Summer of Code 2018
by David Bellot 20 Jan '18

20 Jan '18

Dear Boost community, once again this year, we will apply to be a mentoring organization for the Google Summer of Code 2018. Our organization has been quite succesful for the last decade and this year we hope to be selected again. As part of filling in our application for 2018, we must supply to Google a list of potential GSoC mentors and potential GSoC projects for summer 2018 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/SoC2018 before *January 23rd* would be an enormous help to getting us approved again this year and bringing to Boost another Google funding (worth dozens of thousands of dollars on average). 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. If you want to have a better chance receiving funding for your project ideas, it is better to find good students early 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. Finally, I would like to thank Niall Douglas, our previous Boost admnistrator for GSoC, who did an awesome work during many years and helped the Boost community grow thanks to all the funding we received years after years from Google. Best regards, David

4 9

Fwd: Re: [gsoc18][ublas] Proposal to add advanced matrix operations
by Mike Gresens 20 Jan '18

20 Jan '18

Hi Mike, Apart from the operations I was proposing, the idea of solving polynomials via QR reduction seems a great idea to me. I can add this module in the list of operations to be added to Boost.ublas in my proposal. I am looking for someone to mentor me on this project. Regards, Shikhar Srivastava On Sat, Jan 20, 2018 at 10:34 AM, SHIKHAR SRIVASTAVA <shikharsri1996(a)gmail.com <mailto:shikharsri1996@gmail.com>> wrote: Hi Mike, It looks like some of the operations that I suggested were already implemented as a part of GSOC15, though never got merged into the main branch. https://www.google-melange.com/archive/gsoc/2015/orgs/boostcpp/projects/raj… <https://www.google-melange.com/archive/gsoc/2015/orgs/boostcpp/projects/raj…> https://github.com/BoostGSoC15/ublas/ <https://github.com/BoostGSoC15/ublas/> My Idea was to add generalised modules for the operations (Now) - 1. LU and Cholesky 2. QR and QL 3. SVD On Fri, Jan 19, 2018 at 9:14 PM, Mike Gresens <mike.gresens(a)googlemail.com <mailto:mike.gresens@googlemail.com>> wrote: Hi Shikhar, does this include something for solving polynomials (via balanced-QR reduction of the companion matrix)? See https://www.gnu.org/software/gsl/doc/html/poly.html#general-polynomial-equa… <https://www.gnu.org/software/gsl/doc/html/poly.html#general-polynomial-equa…> Thanks! Best regards, Mike... Am 19.01.2018 um 07:37 schrieb SHIKHAR SRIVASTAVA via Boost: Hi everyone, I am a 4th year undergraduate student pursuing a degree in Computer Science and Engineering. I have strong programming experience in C++ through internships, self projects and programming events. I wish to be a part of gsoc18 under boost and am particularly interested in the linear algebra library Boost.ublas. The ublas library can be made more useful for Machine Learning applications like recommendation systems, clustering and classification, pattern recognition by adding some operations required in those. I propose to add advanced matrix operations to ublas including - 1. Triangular Factorisation (LU and Cholesky) 2. Orthogonal Factorisation (QR and QL) 3. Operations to find Singular Value lists 4. Eigenvalue algorithms 5. Singular Value Decomposition (SVD) 6. Jordan Decomposition 7. Schur Decomposition 8. Hessenberg Decomposition This is a very brief description of what I would like to propose. Any suggestions that help in refining the requirements before making a draft proposal would be great. Regards Shikhar Srivastava Github: https://github.com/shikharsrivastava <https://github.com/shikharsrivastava> _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost <http://lists.boost.org/mailman/listinfo.cgi/boost>

1 0

[geometry][gsoc2018] Similarity between geometries
by Xing GUO 20 Jan '18

20 Jan '18

Hello, My name is Guo Xing, I have sent a mail for some ideas on gsoc18 projects. David's uBLAS project on GPU computation is a little bit hard for me. Still thanks for his kind reply :) . These days, I found a project that I could possibly work on. So, I decide to take "Similarity between geometries". Below is my short self-introduction. Name: Guo Xing University: Southeast University Major: Electronic Engineering Email: higuoxing(a)gmail.com Github: https://github.com/higuoxing Homepage: https://higuoxing.com Availability: (Feb-Jun 4 hr/day) (Jun-Aug 6hr/day or more) As for my code competency, I will take the project 1 competency test after my final exam. Thank you! Regards, Guo Xing

1 0

[callable_traits] Incorrect newlines in git
by Andrey Semashev 20 Jan '18

20 Jan '18

Hi, I've created this PR to fix newlines and tabs in Boost.CallableTraits: https://github.com/boostorg/callable_traits/pull/170 Without it, I cannot update my local Boost tree because git treats the files are modified. Could someone, please, merge this PR? It's really annoying that the update process breaks every time. Thanks.

2 1

[gsoc18] Implement HTTP Library
by Xing GUO 19 Jan '18

19 Jan '18

Dear community: I'm Guo Xing, who is currently a student in his third year of college(bachelor's degree). I have interests in web development. I've done some projects with Python and node before. I want to do some work with C++ in GSoC18. So, is there any ideas for me? Or, someone could be my mentor? I love open source, but never contribute to them. I want to do some contribution. Regards, Guo Xing https://github.com/higuoxing

3 2

crypto hash library
by kerukuro 19 Jan '18

19 Jan '18

While boost::hash and the proposed additions and are good for generic hashing, its API is not very suitable for cryptographic hashes and XOFs. Would there be any interest in boostifying this library eg under name 'boost::digest' and putting cryptographic hashes in there? https://github.com/kerukuro/digestpp

1 0

[gsoc18] R-tree serialization
by Kirill Mishchenko 19 Jan '18

19 Jan '18

Hi, My name is Kirill. I’m interested in the contribution to the project “R-tree serialization”. The search through the mailing list archive has shown there was an interest in this project among students in 2017, but as the GSoC 2017 archive site displays there was no student that participated to accomplish this project. Is it possible to work on this project as a GSoC 2018 participant? It seems like last year Adam Wulkiewicz was ready to be a mentor for the project. Briefly about myself. I am a PhD student working on Computational Humor. More precisely I’m working on the problem of finding/generating a humorous response given a textual input. My C++ programming experience includes a summer internship at Yandex Search and my contribution to mlpack (a machine learning library written in C++) as a GSoC 2017 participant (https://summerofcode.withgoogle.com/archive/2017/projects/4812231682293760/ <https://summerofcode.withgoogle.com/archive/2017/projects/4812231682293760/>). For mlpack I designed and implemented cross-validation and hyper-parameter tuning modules with significant usage of C++ metaprogramming. Best regards, Kirill Mishchenko

2 1

mingw and windows.h
by Raffi Enficiaud 18 Jan '18

18 Jan '18

Hi all, I recently pushed something for boost.test on develop that is apparently breaking the builds on mingw: http://www.boost.org/development/tests/develop/developer/output/igaztanaga-… What I do in the code is this: ---------- #ifdef _WIN32 #include <Windows.h> #endif ---------- and then later ---------- #ifdef _WIN32 class setcolor { protected: void set_console_color(std::ostream& os, WORD *attributes = NULL) const { DWORD console_type; /// some additional windows specific code #endif ---------- I thought that this would be enough for having the windows specific code, but apparently mingw disagrees with the error that some windows specific define is not there. Is this an issue with the code, the SDK, the machine? I have no experience with mingw, but if we are able to include windows.h, then we have to have the defines there (the missing macro is there since Windows 2000). Thanks for the help, Raffi

3 4

Google Summer of Code 2018: submit your proposal
by David Bellot 17 Jan '18

17 Jan '18

Hi all, I migrated the GSoC'18 pages to our wiki on Github. Please contribute your proposals here now: https://github.com/boostorg/boost/wiki/Boost-Google-Summer-of-Code-2018 I would love to see plenty of nice proposals before the end of the week so that we are in good conditions to obtain it again this year. If you have problems with permission please contact me directly Best regards, David

1 0

Change Trac wiki permissions
by David Bellot 17 Jan '18

17 Jan '18

Hi, does anyone have access to the boost Trac wiki. I need to change permissions on a page to allow users to edit the page as well, but I can't find any option. There should be an Admin button next to the Search button but it doesn't appear. The page in question is the Google Summer of Code 2018: https://svn.boost.org/trac10/wiki/SoC2018 Thanks David

2 2

Reforming Boost.System and <system_error> round 2
by Niall Douglas 17 Jan '18

17 Jan '18

Many thanks to those who have contributed to the discussion in the other thread regarding making a breaking change to Boost.System in order to provide empirical test data to persuade WG21 to similarly break <system_error> in a future C++ standard for its own good. This fresh email is hopefully to start finishing the discussion. To summarise discussion to date, Peter has made Boost.System's error_code and error_category constexpr except for the virtual functions. A big win for codegen, and the choice of the default constructor of error_code to use system_category now no longer prevents constexpr, so the request for a new special null_category() can also be dropped. There is substantial opposition to making message() return string_view, so let's drop that request. That leaves the request to fix "if(ec) ..." which right now returns true if the value is 0, despite that much code writes "if(ec) ..." to mean "if error then ...". There is also the issue of error coding schemes not being able to have more than one success value, which usually must be 0. That's the remaining discussion point. Myself and Peter feel this is worth fixing despite the increased runtime overhead. Others, including one of its original inventors, feel it is too much overhead. To add some empirical evidence to the discussion, I have coded up a mock up of the improved error_code which can be viewed at https://godbolt.org/g/dDAWih. This demonstrates constexpr error_code and error_category in action as well. To summarise what the mock up demonstrates: 1. error_category() gains a new virtual function called `bool failure(int code)` which is now called by error_code's operator bool. 2. Thanks to the new constexpr construction, the compiler now completely elides from runtime the case where an inlined function returns an error code and the caller acts upon it. As in, **zero code is now generated**. Far better than before. No virtual functions are called, they are optimised out entirely. 3. For unknown error codes from extern sources where the linker is generating an executable, the "final" modifier removes a layer of indirection when calling `failure()` after the linker has run, and indeed clang seems to go ahead and inline the implementation entirely despite us not asking for LTO. Which is kinda cool. 4. Thus only in shared objects, and only for unknown error codes from extern sources, is a virtual function call actually performed. And given the frequency of doing `if(ec) ...`, it'll almost certainly be hot in the branch predictor i.e. no stalls. Question: is this still considered too much overhead? Note that there is no longer ANY proposed breaking change with existing code. This is now 100% enhancement only. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

17 57

[GSoC2018] About Summer Projects of Boost
by 郭兴 17 Jan '18

17 Jan '18

Hi, there, GSoC2018 is coming, I am in my third year of college(bachelor's degree) and want to be enrolled in this interesting program as student. I want to do some contribution for community. Are there some open projects? Maybe I could do some work? I am interested in [geometry], [ublas] and [asio]. I think I could prepare for it from now on. Cheers, Xing GUO

3 2

Re: [boost] Reforming Boost.System and <system_error> round 2
by Andrey Semashev 17 Jan '18

17 Jan '18

On Wed, Jan 17, 2018 at 2:44 AM, Andrzej Krzemienski <akrzemi1(a)gmail.com> wrote: > 2018-01-17 0:29 GMT+01:00 Andrey Semashev <andrey.semashev(a)gmail.com>: >> >> On Wed, Jan 17, 2018 at 1:16 AM, Andrzej Krzemienski via Boost >> <boost(a)lists.boost.org> wrote: >> > 2018-01-16 19:58 GMT+01:00 Andrey Semashev via Boost >> > <boost(a)lists.boost.org> >> > : >> >> >> >> There's nothing ambuguous about the conversion operator, as it is >> >> specified in the standard, and I find the syntax quite intuitive. >> > >> > You say you find the syntax quite intuitive. But do you also find the >> > semantics intuitive? When you type or read `if(ec)` do you interpret it >> > as >> > "if operation failed" or as "if operation returned code of numeric value >> > zero, regardless of the domain and regardless of whether in this domain >> > zero means success or failure"? >> >> The two interpretations are equivalent for me, because in my code >> error code of zero always means "success". Why? Because I pick the >> error values that way (or map them that way, if the values come from >> an external API) so that they play nicely with `error_code` design and >> the rest of the code. >> >> If we support multiple "success" values or non-zero success values, I >> would expect "if (err)" to mean "if some error happened". Why? Because >> that "if" controls error handling, not an arbitrary non-zero result >> handling. I've never seen or written code that does otherwise. >> >> If I want to test for a particular error code, I would write "if (err >> == x)" or "if (err != x)" - that's the syntax that communicates the >> intent to check for the particular value, including when `x` happens >> to be zero (which doesn't really matter, because `x` is always an enum >> value and never a magic number). You may ask the what is the >> difference between "if (err)" and "if (err != success)" and it is that >> the latter only tests for failure in the particular domain. Now, this >> difference may not be obvious, and that is why I generally avoid >> writing "if (err != success)". > > Yes, that would also be my expectation. So, if I understand your position > correctly, you oppose to introducing yet another function `failure(ec)`, but > you would be ok with fixing `if(ec)` so that it always means "failure" (of > course provided that you can be convinced that there is anything that needs > fixing). Yes. Not actively opposed, though. I just don't see the point in having this more verbose syntax for something that we already have and that is more succint. I'm not opposed to adding support for multiple success codes, quite the opposite. My only condition is that this enhancement doesn't penalize too much the existing usages with a single zero success code. > It has been always my understanding that `error_code` is intended to be used > so that the numeric value is always *exactly* the value returned by the > system call: you do not change it, do not adapt it. You keep it unchanged so > that when logged, the programmer can easily retrieve the original number say > from the log file to check what went wrong with the system call. Instead, > you use all this machinery with conditions to perform different queries, on > what kind/sort of failure it was. > > Now, if you adapt the error code so that 0 means success and non-0 means > failure, you are violating this idea that numeric value of `error_code` > should be delivered unchanged, un-adapted. Mapping foreign success codes to zero may be viewed as a hack, but in practice it rarely matters. When you present error codes to the user, you rarely want to present the numeric value. Most likely, you want to present the human-readable result of `message()`, and it will be produced using the mapped error code values. I agree that ideally you would not have to map error codes, but that is an acceptable compromise to have a decent performance and unified syntax with the existing `std::error_code`. Hopefully, if we settle on an efficient solution, we won't have to do this anymore.

1 0

Upcoming formal review of the [Boost.]Yap library
by Louis Dionne 16 Jan '18

16 Jan '18

Hi everyone, The formal review of Zach Laine's 'yap' expression template library will be starting in 3 weeks, from Feb 05 to Feb 14. yap is a C++14-and-later library to build expression templates, much like Boost.Proto currently does. yap uses new features introduced in C++14/17 to make the library simpler to use and compile faster than existing solutions. The documentation is available here: https://tzlaine.github.io/yap The official repository is here: https://github.com/tzlaine/yap We encourage folks to become familiar with the library and submit feedback to the author even before the review starts. Thanks! Louis Dionne (review manager for this submission)

1 0

[convert][align][coroutine2][dll][endian][fiber][metaparse][check_build][qvm] Missing .gitattributes
by Steven Watanabe 15 Jan '18

15 Jan '18

AMDG I noticed that the following submodules have no .gitattributes: convert align coroutine2 dll endian fiber metaparse tools/check_build Also, qvm forces Windows line endings in its .gitattributes In Christ, Steven Watanabe

1 0

Bug report rejected as conformant
by Edward Diener 13 Jan '18

13 Jan '18

I recently reported a preprocessor bug in Oracle C++ 12.6 on their online forum when compiling a C program example. I even cited the C11 standard in showing that Oracle C++ 12.6's actions were non-conformant. The answer I was given, from an Oracle C++ developer who said he was a member of the C++ standard committee, is that since Oracle C++ 12.6 gives a warning message rather than a compiler error the compiler was compliant with the C standard, since the standard only requires a diagnostic message to be considered standard compliant when it does not implement the compiler according to the standard, and that a warning was a diagnostic message. Furthermore since there was a way to force the particular warning to be considered an error, Oracle was not going to change their compiler. At that point I "lost it" so to speak. I cannot conceive that any C/C++ standard would specify that giving a warning rather than an error, when not complying with the C/C++ standard, would then make the compiler compliant. Comments ?

5 11

[git] Git problem with Boost
by Edward Diener 13 Jan '18

13 Jan '18

git checkout develop git pull git submodule update --init from my local main Boost repository gives me: error: no such remote ref 0ce9138ce86095eab9c09d171fecb5f72c4457f7 Fetched in submodule path 'libs/callable_traits', but it did not contain 0ce9138ce86095eab9c09d171fecb5f72c4457f7. Direct fetching of that commit failed.

3 4

Re: [boost] Potential Boost SAX library
by Bjorn Reese 13 Jan '18

13 Jan '18

On 01/09/18 18:36, Oliver Adams via Boost wrote: > I was wondering if a library I'm developing would be of value to the > Boost community. It is basically an event-driven parsing/serialization > library for common formats using a standard internal representation or > simple pass-through conversions. Would anyone be interested in something > like this being added to Boost? There are two kinds of incremental parsers: push parsers (SAX) and pull parsers (approximately StAX.) Briefly put, push parsers traverses the input automatically and generates events for each token it finds, whereas pull parsers traverses the input manually like an iterator and the current token can be queried. Pull parsers have some significant advantages over push parser: * It is straight-forward to implement a push parser on top of a pull parser. This involves a loop and a switch statement (see [1] for a complete example.) Going in the other direction involves the use of coroutines; most likely stateful coroutines. * Contextual parsing can be done directly, unlike push parsers where you have to maintain contextual state in the event handler. * Push parsers can be used directly in Boost.Serialization archives. * Pull parsers are composable. For instance, you could insert a URL pull parser directly into an HTTP pull parser. For a pull parser framework see: https://github.com/breese/trial.protocol The documentation is a bit old though. [1] http://breese.github.io/trial/protocol/trial_protocol/json/tutorial/push_pa…

3 2

Re: [boost] [system] Would it be possible to trial a breaking change to Boost.System and see what happens?
by Bjorn Reese 13 Jan '18

13 Jan '18

On 01/12/18 18:43, Niall Douglas via Boost wrote: > 2. Success becomes solely the default constructed error code, which is > code zero and a new category of "null_category". This is internally > represented by { 0, nullptr }, and thus makes the default constructor > trivial which is highly desirable as it eliminates any compiler magic > static fencing for the default constructor. Right now the default > constructor uses system_category with value 0, and I suspect no code > will notice this change either. Does this mean that custom error categories have to change their make_error_code(e) function to either return a default constructed error_code in case the error value indicates success, or a custom error_code otherwise? In other words, today we do this: namespace my { std::error_code make_error_code(my::errc e) { return std::error(e, my::category()); } } Should that be changed to this? namespace my { std::error_code make_error_code(my::errc e) { if (e == my::success) return std::error_code(); return std::error_code(e, my::category); } }

1 0

[date_time] building documentation?
by James E. King, III 12 Jan '18

12 Jan '18

I cannot build the documentation for Boot.DateTime on the develop tip - I get an error - am I doing something wrong in the command line or is it just broken? jking@ubuntu:~/boost/libs/date_time/doc$ ../../../b2 boostdoc Performing configuration checks - default address-model : 64-bit - default architecture : x86 ../xmldoc/Jamfile.v2:54: in modules.load *** argument error * rule doxygen ( target : sources + : requirements * : default-build * : usage-requirements * ) * called with: ( date_time_autodoc : : <doxygen:param>ENABLE_PREPROCESSING=NO <xsl:param>boost.doxygen.reftitle=Date Time Reference <doxygen.doxproc.title>Date Time Reference <doxygen.doxproc.id>date_time_reference ) * missing argument sources /home/jking/boost/tools/build/src/tools/doxygen.jam:622:see definition of rule 'doxygen' being called /home/jking/boost/tools/build/src/build/project.jam:325: in load-jamfile /home/jking/boost/tools/build/src/build/project.jam:64: in load /home/jking/boost/tools/build/src/build/project.jam:145: in project.find /home/jking/boost/tools/build/src/build/targets.jam:401: in find-really /home/jking/boost/tools/build/src/build/targets.jam:474: in class(a)project-target.find /home/jking/boost/tools/build/src/build/targets.jam:858: in resolve-reference /home/jking/boost/tools/build/src/build/targets.jam:875: in targets.generate-from-reference /home/jking/boost/tools/build/src/build/targets.jam:1226: in generate-dependencies /home/jking/boost/tools/build/src/build/targets.jam:1280: in class(a)basic-target.generate /home/jking/boost/tools/build/src/build/targets.jam:770: in generate-really /home/jking/boost/tools/build/src/build/targets.jam:742: in class(a)main-target.generate /home/jking/boost/tools/build/src/build-system.jam:796: in load /home/jking/boost/tools/build/src/kernel/modules.jam:295: in import /home/jking/boost/tools/build/src/kernel/bootstrap.jam:139: in boost-build /home/jking/boost/boost-build.jam:17: in module scope

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[date_time] [build] new windows class of build error?
by James E. King, III 12 Jan '18

12 Jan '18

I enabled appveyor for Boost.DateTime pull requests and they are failing miserably when <cxxstd> is specified more than once. I don't remember this occurring in the past. This happens on Visual Studio, cygwin, mingw builds. Is this new Boost.Build behavior? https://ci.appveyor.com/project/jeking3/date-time-1evbf/build/1.0.3-develop error: Name clash for '<pstage\lib>libboost_atomic-vc140-mt-x32-1_67.lib' error: error: Tried to build the target twice, with property sets having error: these incompatible properties: error: error: - <cxxstd>14 error: - <cxxstd>17 error: error: Please make sure to have consistent requirements for these error: properties everywhere in your project, especially for install error: targets. Command exited with code 1

2 1

Informal CMake meeting at CPPCon
by Robert Ramey 12 Jan '18

12 Jan '18

Thursday 28 Sept 8 AM at CPPCon a small group of us met to talk a little regarding the situation regarding support of CMake by Boost. I promoted this meeting as I've been concerned that the only discernible results of the recent Boost Steering Committee announcement on the subject was a certain level of antagonism among boost members regarding the subject. Participants ============ Robert Ramey (me) Rene Rivera Vinnie Falco Louis Dionne David Sankel Matt Calabrese This was a small but I think a representative group. After some preliminary back and forth, I think we agreed: a) Nothing was going change regarding the current build system until there was a real alternative in place. b) That we should support serious proposals to implement CMake support within boost. c) And that any such proposals should go through the Boost formal review process. Traditionally, the boost formal review process has never applied to boost tools so this would be a departure from traditional practice. d) Questions regarding the scope/implemention of such support for CMake can be handled within the formal review process. e) Other questions regarding support CMake and Boost, transition to new system, related requirements on boost libraries, etc. can be better addressed once we have some sort of consensus on the form that CMake support will take. I had contacted Paul Fultz who is the only one I know of that has proposed something specific to submit to formal review. He told me he couldn't do it at the time, but shortly there after posted such a request on the list. So I guess for now we're on our way. My motivation for posting this is to keep the boost community up to date on what's happening so that no one gets overly surprised when things start to happen. I'm not really soliciting feedback - though it wouldn't surprise me if I get some. Robert Ramey

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[scope_exit] (Boost >= 1.65) VS 2015 internal compiler error in lambda
by Tobias Loew 12 Jan '18

12 Jan '18

Hi, starting from Boost version 1.65 and using VS 2015 Update 3 (MSVC 19.00) the following code raises an internal compiler error: fatal error C1001: An internal error has occurred in the compiler. (compiler file 'msc1.cpp', line 1468). With earlier Boost versions it compiles fine. Tobias -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Dev-f2600599.html

3 8

Issue with bjam and building for NDK
by Robert Dailey 11 Jan '18

11 Jan '18

I filed an issue over at the Android NDK github page here: https://github.com/android-ndk/ndk/issues/616 When I invoke b2 to build boost using the standalone toolchain generated by the NDK, bjam seems to be wrapping the command in quotes, like "clang++". This throws off their logic in the clang++.cmd batch script. I was asked to test running b2 without quotes (e.g. clang++), but I am not sure how to do this. Could someone help me understand if this is a code change to b2? Or if there's a jam script somewhere I can modify? I'm not sure if this is a boost issue or an NDK issue at this point. I appreciate any help from the boost developers.

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[contract] ready to release
by Lorenzo Caminiti 10 Jan '18

10 Jan '18

Hello release managers & all, Boost.Contract in master is ready to be added to the next Boost release (regression tests pass, docs are updated, etc.). What do I have to do to put https://github.com/boostorg/contract.git master into Boost release 1.67? Thank you. --Lorenzo

2 3

Potential Boost SAX library
by Oliver Adams 10 Jan '18

10 Jan '18

Hi all, I was wondering if a library I'm developing would be of value to the Boost community. It is basically an event-driven parsing/serialization library for common formats using a standard internal representation or simple pass-through conversions. Would anyone be interested in something like this being added to Boost? Thanks.

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[outcome] Training video in post-Toronto std::expected<T, E>
by Niall Douglas 09 Jan '18

09 Jan '18

In preparation for the Outcome v2 review next week, reviewers may find the video of my Meeting C++ talk in Berlin last year useful to watch beforehand. The talk is a literature review covering all the WG21 papers related to the post-Toronto std::expected<T, E>, which is quite different to the Expected during the Outcome v1 review. https://www.youtube.com/watch?v=JfMBLx7qE0I My thanks to Jens for prioritising the release of this video, and for running a great C++ conference. I'm still building a list of errata for the video, once complete I'll post a list underneath it. Any mistakes that I made, please do let me know, ideally with a timestamp offset into the video. My thanks to all those who are currently reporting so many, many bugs in the reference docs. I'll try my best to fix them all before end of next week, but keep them coming! Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

1 0

Re: [boost] seeking endorsement for histogram library
by Bjorn Reese 09 Jan '18

09 Jan '18

I endorse boost.histogram.

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[date_time] recommending upgrading the timezone database
by James E. King, III 07 Jan '18

07 Jan '18

The timezone database in Boost.DateTime doesn't have enough information in it to be accurate all the time. For example if a region changes time zone rules, when applying timezone only the current rule will be applied regardless of the date involved. If a region stops using daylight savings time, but a date/time falls before that rule change, it should still use daylight savings in printed output, correct? The IANA timezone database is more complete, and we could switch Boost.DateTime to use that instead. It is also maintained more frequently than the built-in one, which was last updated 7 years ago, and 4 years before that. Any thoughts on this? https://github.com/boostorg/date_time/issues/67 - Jim

2 1

Adding AppVeyor as a required check to a Boost repository on Github
by Edward Diener 07 Jan '18

07 Jan '18

I am trying to add AppVeyor as a required check to the boostorg/date_time repository on Github. I have gone through the step of adding 'develop' as a protected branch, checking "Require status checks to pass before merging", and checking "Require branches to be up to date before merging". The only thing that then appears in the settings for the protected 'develop' branch is: "Status checks found in the last week for this repository" is "continuous-integration/travis-ci" "required", which is checked. Nothing about AppVeyor whatsoever. Anyone know what the Github voodoo is for getting this to happen ? I see other Boost repository with both Travis-CI and Appveyor required checks but evidently the doc for doing this for AppVeyor is non-existent in Github.

1 0

[hash] Extract module from functional + std::hash_combine
by Daniel James 06 Jan '18

06 Jan '18

Hi, I'm planning to extract hash from functional into its own module, as that will apparently break the circular dependencies that functional is part of. Any objections? Also, any opinions on what the module should be called? 'hash' might suggest a more general purpose hash function, so maybe it should be called something more specific. Daniel

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[date_time] Eliminate pre-1.33.0 io facet code?
by James E. King, III 06 Jan '18

06 Jan '18

There was a bug change around the 1.33.0 release timeframe that added new io facet handling for date_time. It is conditionally disabled using the definition USE_DATE_TIME_PRE_1_33_FACET_IO. I suggested in a github issue that the pre-1.33 mode be removed at this point. Any thoughts on that? https://github.com/boostorg/date_time/issues/61 - Jim

2 1

[outcome v2] Pre-review feedback
by Niall Douglas 05 Jan '18

05 Jan '18

Outcome v2's review starts on Friday 19th January, after which I can't fix even obvious problems. The documentation is by far the newest and most experimental part using bleeding edge tooling, so getting a few rounds of fixes in now before locking everything down for the review would be great. Can those who are super keen have a look at the reference API docs and find problems that me and Jonathan can fix before the review begins? You can find the reference API docs at: https://ned14.github.io/outcome/reference/ And issues can be logged to https://github.com/ned14/outcome/issues or https://github.com/foonathan/standardese/issues if you're sure of the source of the problem. Potential problems to look out for (not a complete list): - Lack of documentation summary string - Confusing or meaningless documentation - Incomplete or mangled documentation for some entity (e.g. sentences missing sections, lines reordered) - Leakage of "detail" namespace or of types or macros clearly of internal implementation detail - Stray or missing commas, angle brackets, brackets - Missing or insufficient requirements, effects or throws clauses - Appearance of any `std::enable_if`, these are supposed to be suppressed into requirements, but I know `outcome.hpp` is particularly bad on that (tracked by https://github.com/ned14/outcome/issues/76) - Lack of hyperlinking to other parts of the reference docs where that was clearly intended. To expand on the "bleeding edge tooling" part, these reference API docs are generated using https://github.com/foonathan/standardese which is based on clang libtooling. Some of the problems are caused by clang libtooling, some by standardese, some by me. I don't doubt that these reference API docs are an enormous improvement over those from doxygen - especially the ability to search semantically for stuff related to search term - but there are a lot of very small problems I'd love to clean up before the formal review begins. Thanks in advance. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

1 0

Changing the website (Was: Need help with bootstrap.bat)
by Andrzej Krzemienski 05 Jan '18

05 Jan '18

2018-01-03 13:54 GMT+01:00 Daniel James via Boost <boost(a)lists.boost.org>: > On 3 January 2018 at 10:04, Andrzej Krzemienski via Boost > <boost(a)lists.boost.org> wrote: > > > (n.b. It was very difficult to find this page as there is no direct link > > from www.boost.org) > > I'll add a link to the 'getting started' section. Maybe we should move > more content onto the github wiki? It's just a git repo with markdown > pages so it shouldn't be too hard to serve it from the website if > people would like it to be more integrated. > Let me share with you my recent experience. I was looking for something like "getting started for Boost developers" and could not find a place.In the front page there is section "INTRODUCTION", but it looks like content for potential users (rather than developers). There is section "DEVELOPMENT" but the content is more like "how to submit a new library", but no "getting started with developement" (on somebody else's library) There is a "WELCOME" -> "Getting started", but it looks like one for the users. (it recommends downloading a zip file). There is this non-obvious path: DEVELOPEMENT -> Reporting and Fixing Bugs. While there, click on "git repositories". It opens a stub page that says it has been superseded by another, and when you push on a link you get there. But this really should be simpler. Maybe in the front page we should have "DEVELOPMENT" -> "Getting Started" that links directly to https://github.com/boostorg/boost/wiki/Getting-Started Or maybe the topics should be divided differently: - Getting started with using Boost Libraries - Getting started with applying improvements to existing Libraries - Getting started with submitting a new library. I consider this more important than where actually the content is hosted. Regards, &rzej;

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[test] Test cases parametrized by both type and value?
by Andrzej Krzemienski 05 Jan '18

05 Jan '18

Hi, Can anyone tell me if Boost.Test can solve the problem that I describe below. I have a function template inspect: ``` template <typename T> bool inspect(T const& v); ``` I want to test if it returns `true` for the following values: 1 (type int) 10 (type int) 1.0 (type double) "Y" (type const char *) Basically, different values of different types, but sometimes different values have the same type. I would like to write one test or "test template" with the following contents: ``` BOOST_TEST((inspect(v))); ``` Where `v` is name of the currently tested value. (But `v`s will have different types). I can emulate this behavior using template test cases and artificial types: ``` struct int_1 { static int value() { return 1; } }; struct int_10 { static int value() { return 10; } }; struct double_1 { static double value() { return 1.0; } }; struct cstr_Y { static const char * value() { return "Y"; } }; typedef boost::mpl::list<int_1, int_10, double_1, cstr_Y> test_types; BOOST_AUTO_TEST_CASE_TEMPLATE( my_test, T, test_types ) { BOOST_TEST(inspect(T::value())); } ``` (See working example in WandBox: https://wandbox.org/permlink/KcJqT8KvL3zIqAxL) But maybe there exists a direct solution in Boost.Test? Where I would just pass a list of values: `{1, 10, 1.0, "Y"}` It is easy to deduce types from values: ``` template <typename... T> mpl::liss<T...> Values(T... values); using test_types = decltype(Values(1, 10, 1.0, "Y")); ``` Does something like this exist, or ois it a reasonable extension? Regards, &rzej;

4 3

[regression] results pages not updating
by Joaquin M López Muñoz 04 Jan '18

04 Jan '18

Hi, Just a heads up, regression tests result pages: http://www.boost.org/development/tests/master/developer/summary.html http://www.boost.org/development/tests/develop/developer/summary.html aren't updating since Jan 1. Thank you, Joaquín M López Muñoz

3 5

Interest for a Fixed Point Arithmetics library
by Julien Vernay 03 Jan '18

03 Jan '18

Hello everybody. I am working on a project that needs and can use fixed point numbers, so I started searching for a library implementing fixed point numbers, but I didn't find anything. So I was wondering if people would need fixed point arithmetics, and here I am. The aim of this FixedPointNumber is to fix the point at compile-time using template, and having another template argument for the underlying type. So we have : template<typename T, size_t N> class FixedPointNumber { T value; public: //interface }; The N last bits of value is the decimal part : so to convert a FixedPointNumber to an int, we need only to use a bitshift operator (and same for construction from int). sizeof(FixedPointNumber<T,N>) == sizeof(T) , so there is no overhead in this implementation. Arithmetic and relational operators will be implemented. Multiplication needs one int multiplication and one bit shift. Division needs one int division and one bit shift. There is only one value for zero. Sign can be extracted with Most Significant Bit. I have already a basic implementation but if it interests more people I will do a proper implementation. Thank you for reading !

4 7

[multiprecision] Help needed with strange constexpr slowdown
by John Maddock 03 Jan '18

03 Jan '18

Folks I have a very strange issue that I need help with understanding, it comes from https://github.com/boostorg/multiprecision/issues/32 but in summary: Given: #include <iostream> #include <boost/multiprecision/cpp_int.hpp> using namespace std; using namespace boost::multiprecision; int main() { __int128_t i =0; __int128_t j =0; int256_t sum =0; for (; i <1e9; i +=19, j +=13) { int256_t diff = j; sum += i * diff; } std::cout <<"Result: " << sum << std::endl; return 0; } There is a 20-30% slowdown when compiled in C++11 or later compared to C++03 with gcc 5.x or 6.x. I've tracked this down to the constexpr default constructor for int256_t (which is called inside operator* to create a temporary for the result), if I make the default constructor non-constexpr by removing BOOST_CONSTEXPR from any of: number.hpp:44 (number()) cpp_int.hpp:1077 (cpp_int_backend()) cpp_int.hpp:501 (cpp_int_base()) cpp_int.hpp: 435 (cpp_int_base::data_type()) Then the slowdown disappears. All the line numbers refer to current develop BTW. gcc-7 is better, but I notice it still generates different code if the constructor is constexpr - that greatly surprises me to be frank - is there something I'm missing about constexpr-ness that could cause this? Confused yours, John. --- This email has been checked for viruses by AVG. http://www.avg.com

3 3

Need help with bootstrap.bat
by Andrzej Krzemienski 03 Jan '18

03 Jan '18

Hi Everyone, Maybe someone can help me with configuring bootstrap.bat. I am trying to set up the environment for developing boost libraries, and it is my understanding that the first step (after cloning a git repository) is to build b2 itself using the script bootstrap.bat. I got this from instructions at https://github.com/boostorg/boost/wiki/Getting-Started (n.b. It was very difficult to find this page as there is no direct link from www.boost.org) I am using MinGW on Windows, no Visual Studio installed. Nonetheless bootstrap.bat concludes that it should compile with cl.exe, and it does not work. I know that MinGWis not supported, but I have to take my chances. Maybe somebody knows how to instruct bootstrap.bat to select a GCC compiler and tools? Regards, &rzej;

5 6

help for contribution
by ashwin.pathak 03 Jan '18

03 Jan '18

Hi Developers, I am very interested in computer programming and I find boost c++ libraries really exciting. I would like to contribute to the organization, I am new to this organization. Can someone please help me to get started in contributing to the organization. Thank you, Best Regards, Ashwin Pathak

1 0

Re: [boost] Boost.HTTPKit, a new library from the makers of Beast!
by Vinnie Falco 01 Jan '18

01 Jan '18

On Sun, Oct 8, 2017 at 5:38 PM, Vinícius dos Santos Oliveira <vini.ipsmaker(a)gmail.com> wrote: > Now, moving on... given that you have __not__ answered how your parser's > design[1] compares to the parser I've developed I'll try to provide more clarity. `beast::basic_parser` is designed with standardization in mind, as I intent to eventually propose Beast for the standard library. Therefore, I have made the interface as simple as possible, exposing only the minimum required necessary to achieve these goals which the majority of users want: * Read the header first, if desired * Feed Asio style buffer sequences into the parser * Set independent limits on the number of header and body octets * Optional fine-grained receipt of chunked body data and metadata The design of basic_parser (the use of CRTP in particular) is meant to support the case where a user implements their own Fields container, or if they want a bit more custom handling of the fields (for example, to avoid storing them). Like all design choices, tradeoffs are made. The details of parsing are exposed only to the derived class. Complexities are hidden from the public-facing interface of `basic_parser`. Implementing a stream algorithm that operates on the parser is a straightforward process: template< class SyncReadStream, class DynamicBuffer, bool isRequest, class Derived> std::size_t read(SyncReadStream& stream, DynamicBuffer& buffer, basic_parser<isRequest, Derived>& parser, error_code& ec) { parser.eager(true); if(parser.is_done()) { ec.assign(0, ec.category()); return 0; } std::size_t bytes_transferred = 0; do { bytes_transferred += read_some( stream, buffer, parser, ec); if(ec) return bytes_transferred; } while(! parser.is_done()); return bytes_transferred; } > [1] at most it hides behind a “multiple people/stakeholders agree with me” > __shield__ There's no hiding going on here. One can only measure the relative success of designs based on the feedback from users. They opened issues, and I addressed their use-cases, sometimes with a considerable amount of iteration and back-and-forth as you have seen in the GitHub issues quoted in the previous message. Now, I don't know if the sampling of users that have participated in Beast's design are representative of the entire C++ community. However, I do know one thing - if GitHub stars are any measure of the sample size of the participants, then Beast is off to a good start. Here's a graph showing the number stars over time received by boostorg/beast, tufao, and Boost.Http (the last 2 libraries having you as the author I believe): <http://www.timqian.com/star-history/#boostorg/beast&BoostGSoC14/boost.http&…> (Note that the HTTP+WebSocket version of Beast was released in May 2016). We need to be careful interpreting results like this of course so perhaps we should look at different metrics. Here are the links to the number of closed issues for Beast, tufao, and Boost.Http: 502 Closed issues in Beast: <https://github.com/boostorg/beast/issues?q=is%3Aissue+is%3Aclosed> 38 Closed issues in tufao <https://github.com/vinipsmaker/tufao/issues?q=is%3Aissue+is%3Aclosed> 13 Closed issues in Boost.HTTP, from 6 unique users not including the author <https://github.com/BoostGSoC14/boost.http/issues?q=is%3Aissue+is%3Aclosed> Again we have to be careful interpreting results like this. But it sure looks like there is a lot of user participation in Beast. If approval from a large number of stakeholders is not a compelling design motivator then what is? > This tutorial is full of “design implications” blocks where I take the time > to dissect what it means to go with each choice. Thus far, no one has asked for more fine grained access to incoming HTTP tokens in the manner of `code::method` and `code::request_target`. If this becomes something that users consistently ask for, it can be done by changing the requirements for the derived class for `basic_parser`. This way, details about HTTP parsing which most people don't care about will not leak into the beast::http:: namespace. Such a change would not affect existing stream algorithms on parsers. Thanks

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