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[boost][review] Outcome Review Report
by charleyb123 . 06 Jun '17

06 Jun '17

# Boost.Outcome REVIEW REPORT In conclusion to the Outcome Library Review (19-May to 02-June, 2017): The library is REJECTED. Rejection is principally due to: (1) Unresolved key behavior at conclusion of the review period (2) Misunderstanding/disagreement regarding library’s intended purpose (3) Unclear precedent/implications from accepting this library in its current configuration into the Boost distribution The following weighed heavily to consider accepting the library into Boost: (a) The library demonstrates solutions to fundamental issues (error and exception handling) (b) The library effectively addresses constraints to serve the needs of several user-bases (c) New paradigms/idioms are enabled (d) Implementation is of high quality Some 20+ participants sent 850+ email messages to the public list discussing the Outcome library, plus additional (non-trivial) off-list discussion. Public reviews sent to the list were from: *- Paul Bristow -- ACCEPT (Tue-23-May) *- Deniz Bahadir -- ACCEPT (Wed-24-May) *- Robert Ramey -- REJECT (Fri-26-May) *- Peter Dimov -- REJECT (Sun-28-May) *- Emil Dotchevski -- REJECT (Sun-28-May) *- Vicente J. Botet Escriba -- REJECT (Tue-30-May) *- Andrzej Krzemienski -- REJECT (Wed-31-May) *- Gavin Lambert -- REJECT (May 31) *- Bjorn Reese -- REJECT (Fri-02-June) The remainder of this report is a summary of discussion with select issues specific to the Outcome library, plus some possible topics for further consideration by the Boost Community and Boost Steering Committee. This further elaboration is not intended to be comprehensive regarding issues raised during the review; Rather, it is to: (a) Provide historical “summary/context” for the level of discussion exhibited during this review, and which contributed to the final decision; (b) Highlight issues that may provide assistance in considering “readiness” for a later review for an evolved form of this library (or for a similar library intending to address the same domain); (c) Provide “discussion-points” for the Boost Community and Boost Steering Committee regarding possible future evolution or guidance associated with Boost tooling, distribution, and individual library dependencies (related to topics raised during this review). The conclusions will be: (1) Outcome Library Author: Consider re-submitting for review when... (a) Key behavior/design issues are resolved (see below) (b) Integration plan with Boost is more clear (and consistent with Boost Steering Committee Guidance) (2) Boost Community / Boost Steering Committee: Consider providing guidance to future library submissions regarding... (a) Attempted dual-license, this submission attempted: *- BSL+Apache2 dual-license (b) “Extra-build-steps”, this submission attempted: *- Custom preprocessing to “generate-source” (to significantly improve compile-time speed) (Note: During review, a template-based solution was proposed as a possible replacement mechanism, but code-gen should probably be explicitly addressed) (c) Class/namespace versioning, this submission attempted: *- Stable ABI/versioning mechanism through a framework provided with this submission (to enable multiple versions of this library used by differing third-party libraries to correctly coexist within the same binary) (d) Use of outside source; use of git (git-submodules), this submission attempted: *- Dependency to an outside (git-submodule) lib archive (gsl-lite: https://github.com/martinmoene/gsl-lite.git ) (e) Use of (non-test/Jamfile) for test, this submission attempted: *- Custom test mechanism (because “Boost.Test” won’t work with C++ exceptions disabled; lib needed “boost-lite” to run the test suite) (f) Use of CMake, Dependency upon Boost, this submission attempted: *- No Boost dependency (but provided a “boost-lite” shim to coexist in user-workspaces with-or-without Boost, providing common cmake machinery and test-running) # SUMMARY OVERVIEW As demonstrated through the volume and depth of discussion, the library attracted wide interest, which is consistent with a perception that it attempts to address an active need. Comments suggested the library’s purpose (enabling public APIs to pass <value|error|exception>) was useful, and that enabling a shared handling of <error|exception> to be somewhat novel. Several participants further suggested that the library attempts to serve a role as a “fundamental” library: to provide vocabulary types and pose new idioms, to be used in public APIs as a common <error|exception> exchange mechanism. One reviewer commented that the library’s documentation under-sold the library’s motivation, suggesting it compelling for: *- Cases where errors cannot be propagated by throwing exceptions (e.g., within callbacks where an error value is provided [e.g., ASIO]); *- When passing values between threads, such as in an Actor model where a message queue handles return values (e.g., pass outcome<T> instead of an std::error_code to handle <error|exception> in addition to desired <T>) Many/most reviewers that voted REJECT commented that they would like a similar library to be accepted, or perhaps an evolved form of this library after necessary changes (see below). To accept the importance of the domain which the library attempts to address, one need not agree with the design nor implementation of Outcome (indeed, the library is rejected in its current form at the conclusion of this review). Rather, this summary assertion is that the Outcome proposal successfully demonstrates a need for such a fundamental (and community-endorsed) solution (or direction) for error handling. # ISSUE: Unresolved key behavior at conclusion of the review period Key behavior (or design) issues that did not reach consensus by the end of the review period: (1) Narrow vs. Wide contracts -- consensus is not reached (2) Empty-state (allowed?) remains controversial (3) Ring-buffer appears uncontroversial; but perhaps needs additional scrutiny (a) Separate library implementation (for reuse elsewhere, and to enable evolution without touching the ‘result<>’/’outcome<>’ API)? (b) Bigger buffer? Some of the difficulties in this evaluation likely trace to the (in-progress) evolution of the proposed ‘std::expected<>’ (also discussed during this review). A future Outcome review would likely benefit from the clarity provided by fully resolved semantics for ‘std::expected<>’. # ISSUE: Misunderstanding/disagreement regarding library’s intended purpose The Outcome library attempts to define a paradigm and propose idioms in <error|exception> handling, where few can successfully argue that current practice, libraries, and idioms are sufficient. The review concluded that Outcome proposes a new paradigm that is demonstrated to be useful and effective. However, disagreement exists on the nature of that framework: PURPOSE: Outcome is a unified/universal <error|exception> handling framework for use in public APIs; (a) ...enabling user-customization to address domain-specific constraints ...versus... (b) ...for possible future consideration in a C++ Standards Track, likely within <system_error> The Library Author intended (a), while multiple reviewers advocated for (b). This disagreement-in-vision resulted in many difficult discussions during the review, and ultimately lack of consensus for several important API and design decisions (due to the corresponding implied future limitations). For example: Static-checked vs. Runtime-checked behavior. The library-as-presented attempts to serve both, citing orthogonal user bases with differing (latency) constraints, such as “with-or-without” runtime overhead, and “with-or-without” Undefined Behavior (UB). Current implementation enables integration of arbitrary third-party libraries (each with their own preferred error handling strategy and tradeoffs), with zero-cost conversion and inter-operation. However, this *significantly* complicates the design: The user composes ‘result<>’ and ‘outcome<>’ types with regards to module-specific static or runtime type safety and performance requirements, which (transparently) propagate through the library internals and across threads and public APIs to external modules. In contrast, a C++ Standards Track implementation is likely much simpler, introducing one-or-two vocabulary types merely parameterized on ‘<T>’, providing a simplified (and “standard”) mechanism to bridge <T|error|exception> transport across third-party module boundaries. For example, in advocating for a “Standards-Track” vocabulary type, reviewers argued for a mechanism that would enable user-libraries to obsolete the duplicate “throw/no-throw” APIs with a single API: R filesystem_api(); // throws filesystem_error R filesystem_api( error_code& ec ) noexcept; ...becomes... outcome<R> filesystem_api(); // <R|error|exception> The contrast between the two visions can more distinctly be termed: (a) “Multi-Modal” Usage -- Many varieties of usage style within the API is necessary, because there are a multitude of ways for library abstractions to be used in composition patterns due to domain-specific constraints (likely with some idioms not yet discovered, or not yet in widespread use) (b) “Single-Modal” Usage -- One (single) clean design and use model is encouraged The Library Author states that normal C++ design principles should prefer (b), but due to the vocabulary-type nature of the problem and domain-specific constraints encountered by real-world users, this particular library was forcefully evolved into (a). It is perhaps ironic that the suitability of a proposed library as providing vocabulary types and possibly evolving into a future standard demands that the Library Author change the library’s stated purpose due to this potential popularity; but that seems consistent with the current circumstance. The Library Author (of course) should have authority to characterize the actual intended use-case and resulting behavior provided through the authored work; with the Review Process providing analysis and feedback regarding possible missed opportunity resulting from those decisions. However, this review’s conclusion seems to encounter the curious scenario where the vision itself remains in conflict. Of course, these very differing outlooks resulted in some apparent “impasses” or circular discussions regarding type-safety (and number-of-types), wide or narrow contracts, optimization opportunities, “too-big” (or “cluttered”) interfaces, implicit or explicit conversion, the need for iterator and visitor patterns on ‘outcome<T>’, and the “empty” state and sentinel values. In support of the “Multi-Modal” design, the Library Author posits three main use patterns exist for error-handling objects-returned, and that a single design can serve only two at best: (Quoting the Library Author): > <quote> > (1) User wants failure reason type to be local to only the code to which > it applies. So think custom E type, nonconvertible to any other E type, and > E is never error_code nor exception_ptr. They specifically want to keep > failure handling local a small patch of code e.g. constexpr evaluation > contexts. > > All-narrow observers make sense for this use case as object usage is > tightly integrated to the code using it, and failure is handled entirely > locally. > > (2) User wants failure reason type to be globally understood and will be > choosing either E = std::error_code, or E = std::exception_ptr. They > specifically want failure handling to be able to traverse any or all code, > just like C++ exception throws. This is where Outcome was primarily aimed > at. > > All-wide observers make sense for this use case, as due to handling a wide > degree of uncertainty, most failure handling code is *generic* i.e. we test > for some specific failure causes, and for everything else we either ignore > or hand it off to other code to handle. > > (3) User wants to write functional programming logic using the basic > vocabulary of Maybe, Either and i/o monads and basic operators of bind, > fmap, do etc and probably some subset or refinement of Hana for the > collections monads, though my GSoC student may be making the Ranges TS a > choice here as well later this summer. > > All-narrow observers make sense for this use case as the monadic operators > ensure your function will never be called with the wrong state. > </quote> The Outcome library uses a, “single implementation, multiple personalities” to solve this problem, and makes the intentional decision to attempt targeting (2). # ISSUE: Unclear precedent/implications from including this library in its current configuration into the Boost distribution The library in its current configuration is perceived as setting precedent for changes to the Boost distribution, which reviewers commented added complexity to their analysis. Specific topics: *- Dual-license (BSL and Apache2) confused reviewers *- Add bjam support (author agreed) *- Packaging relied upon git-submodules to an outside lib archive (gsl-lite, https://github.com/martinmoene/gsl-lite.git) *- Library does tricks with the preprocessor to avoid significant compile-time costs; but these tricks were commented by some reviewers as being unnecessarily complex. *- The Author found these tricks necessary to reach reasonable compile metrics for large projects using Outcome in their public APIs, and believes some mechanism must address this build-speed-need. A proposed metaprogramming mechanism may eliminate the need for these preprocessor tricks in the future. # FINAL THOUGHTS In the very active years of “Classic Boost” (such as 2004-2008), fundamental libraries had a good chance of becoming vocabulary types that attempt to establish new Best Practice for the industry (and not merely be “just another library”). This awareness drove much of the review discussion, and underscored the importance of experimentation and “lessons learned” to result in a library that offered: (1) behavior and idioms that are understood; and (2) sufficient experience to make use recommendation to the wider user base in contrast to existing alternative approaches. Consistent with this historical context, it should be relatively uncontroversial to recognize that the Outcome library does not reach that threshold at this time (so it is rejected). However, this review also suggests: (1) A similar library is needed; (2) The community lacks agreement on direction (e.g., “Multi-Modal” vs. “Single-Modal”) In support of experimentation and to expand on our “lessons-learned”, it seems somewhat obvious that Outcome provides a strongly-implemented Multi-Modal low-latency library that will assist the community in gaining experience with these idioms proposed. Since conclusion of the review period, discussion continues (on and off-list) regarding possible evolution to the Outcome library, related to feedback provided during this review, and related to discussions of design evolution for pertinent libraries (e.g., possible changes to std::expected<>, and evolution of a never-empty ‘variant2<>’). It is promising that such a strong library as Outcome continues to receive critical attention and evolution by multiple interested parties. Great thanks to the Boost Community for their tremendous efforts, disciplined review, and detailed exploration of topics in considering this library submission. Sincerest appreciation to Niall Douglas (Author of the Outcome Library) for pushing the envelope for low-latency <error|exception> handling and for submitting his work to the Boost Review process. -- charley (Outcome Review Manager) If there be any in this assembly, any dear friend of Caesar's, to him I say that Brutus' love to Caesar was no less than his. If then that friend demand why Brutus rose against Caesar, this is my answer: not that I loved Caesar less, but that I loved Rome more. (3.2.19-24)

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[boost] [sort] Timsort review
by Steven Ross via Boost 03 Jun '17

03 Jun '17

The review for C++ Timsort in Boost will commence tomorrow, June 3, and continue through June 12. I am the review manager. The code can be found here: https://github.com/boostorg/sort/pull/12 To merge it into a local copy of the Boost.Sort library: git checkout -b ZaMaZaN4iK-feature_branch/TimSort develop git pull https://github.com/ZaMaZaN4iK/sort.git \ feature_branch/TimSort If you want to see a proposed version of the Sort library source with Francisco's changes and Timsort included, download the zip file <https://drive.google.com/file/d/0B4s-GPKYVV0jOGx5ckJUTkZzMWM/view?usp=shari…>. Feel free to compare flat_stable_sort with Timsort. Please answer these questions in reply to this thread: 1. What is your evaluation of the Timsort implementation? 2. What is your evaluation of the comments? 3. Did you try to use the library? With what compiler? Did you have any problems? 4. How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? 5. How familiar are you with the details of hybrid and stable sorts? 6. Would you actually use Timsort if it was in Boost.Sort? If so, how is it better than the next best alternative? 7. Do you think Timsort should be included in Boost.Sort? Please ask Alexander Zaitsev any questions you have about Timsort for this review before submitting your final review. Thanks, Steven Ross _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost

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[boost][outcome] Outcome Review Period Closes Today (Fri-02-June)
by charleyb123 . 02 Jun '17

02 Jun '17

Hello Everyone, Today concludes the Outcome library review period (Fri-02-June-2017). Great thanks to all that invested so much time and effort to explore in such a disciplined and professional manner the dark corners of error/exception composition and a paradigm/API/implementation proposed by the Outcome library. Your efforts are truly appreciated. Reviews sent to the public list are the following (PLEASE contact me if I've missed your review): *- Paul Bristow (Tue-23-May) *- Daniz Bahadir (Wed-24-May) *- Robert Ramey (Wed-24-May) *- Peter Dimov (Sun-28-May) *- Emil Dotchevski (Sun-28-May) *- Vicente J. Botet Escriba (Tue-20-May) *- Andrzej Krzemienski (Wed-31-May) *- Gavin Lambert (Wed-31-May) My understanding is that as the review concludes today, further reviews are permitted only until the end-of-day UTC. In addition, many notable discussions and topics raised during the review period will also contribute to a final submission decision and summary report. Preparing this report will take some time. I've accumulated extensive notes, but my intention is to review (re-read) all discussion in the context of the "story-arc" and (in some cases) the shifted opinions of some persons during the course of the review (as topics were clarified and alternatives were explored). I assume other "satellite discussions" will continue (e.g., evolution of std::expected<>, suitability of wide vs. narrow contract in APIs, generalization of variant<>, etc.), which I will endeavor to continue to follow as the Outcome Review summary report is prepared (because these continued discussions may further clarify issues previously raised during the Outcome Review); but no more reviews can be accepted after the review period closes. Thank you all (again) for your (often thankless) contributions to the community, where the personal sacrifice in time and effort (and perhaps stressful emotional investment) is quite obviously extensive in many cases. --charley

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[boost][review] Review of Outcome (ends Fri-June-2)
by charleyb123 . 29 May '17

29 May '17

Reminder -- On Fri-26-May the Review Wizards approved extending the Outcome review until Fri-02-June. (Notification was sent to the list, but considering the high traffic volume lately, one can be forgiven for having missed that message.) Thank you to everyone for your tremendous efforts in taking part in the review; for keeping up with high message traffic; and for the professional and deep exploration of the many (very broad!) topics touched on during this review. The review continues for several more days, ending Fri-02-June (it will not be extended further). Please consider posting a review to the boost mailing list, 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

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[boost][review] Review of Outcome (ends Sun-28-May)
by charleyb123 . 25 May '17

25 May '17

Hi, Everyone, First a (very-)big "thank-you!" to all participating in the ongoing (and vigorous) debate and review for the Outcome library. The spirited discussion touches on tricky issues for composition and error handling (with and without C++ exceptions enabled), where the community is clearly searching for best convention and common ground. Thus far: (a)- some 300+ emails discussing Outcome (and more emails off-list) (b)- participation from: *- Andrzej Krzemienski *- D25fe0be *- Deniz Bahadir *- Emil Dotchevski *- Gavin Lambert *- Glen Fernandes *- Gottlob Frege (Tony) *- Hartmut Kaiser *- Ion Gaztanaga *- Jonathan Muller *- Niall Douglas *- Paul Bristow *- Pete Bartlett *- Peter Dimov *- Robert Ramey *- Thomas Heller *- Vicente J. Botet Escriba *- Vinnie Falco *- ...(apologies if I've missed anyone) (c)- Some points-of-discussion relate to: *- Outcome efficiency (copy/move) on today’s compilers *- Outcome speed/overhead (exceptions) *- Outcome purpose/motivation *- Outcome Tutorials, documentation *- Outcome “formal-empty-state”, default-initialization *- Outcome compiling, compiler support *- Outcome ABI, namespace usage, use of preprocessor *- Outcome alternative APIs *- std::expected proposal, possible changes (d)- Reviews to date (sent publicly to the list): *- Paul Bristow -- accept, conditional (Tue-23-May) *- Deniz Bahadir -- accept, unconditional (Wed-24-May) *- Thomas Heller -- (almost a review), ?reject, "not-ready-yet?" (Wed-24-May) (e)- Significant other discussion also contributes to evaluation of Outcome as a Boost library. However, I encourage further reviews to make clear any conclusions from these discussions that I might have missed. The review continues for several more days, ending Sun-28-May. Please consider posting a review to the boost mailing list, 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

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[review] PolyCollection formal review results: ACCEPTED into Boost
by Ion Gaztañaga 22 May '17

22 May '17

Hi, Thank you for your participation in the PolyCollection review. I'll try to collect all votes and summarize the agreed changes on the library. ----- Votes ----- I count 8 (all positive) reviews and votes from Pete Bartlett Andrzej Krzemienski Hans Dembinski Thorsten Ottosen Vinnie Falco Edward Diener Brook Milligan Steven Watanabe -------- Comments -------- Additionally the following boosters did some positive comments on the library and made some questions Dominique Devienne Adam Wulkiewicz Myself No comment was blocking for the acceptance of the library so Boost.PolyCollection is accepted into Boost, congratulations to Joaquín! I recommend committing the library to the boostorg repo as soon as possible in order to start regressions and try to include the new library in Boost 1.65. Many of the proposed changes are one-liners in the documentation and code and hopefully will be ready for Boost 1.65. Deeper changes can wait until Boost 1.66. --------------------------------------- Summary of agreed comments and changes: --------------------------------------- ------------------ Dominique Devienne (positive comment) https://lists.boost.org/Archives/boost/2017/05/234672.php ------------------ "I suspect the new poly_collection could be used for more efficient parallel (and/or concurrent) processing of elements, and would be interested in examples and even a ::parallel_for_each() algorithm that leverages the collection's internal storage" Joaquín will try to play with this idea to see how it fares performancewise. ------------------ Pete Bartlett (positive review) https://lists.boost.org/Archives/boost/2017/05/234669.php ------------------ "It may be worth remarking in the docs what facilities are used for the type registries that are presumably behind the scenes. From the reference section I think RTTI is required. Is this a hard limit or could Boost.TypeIndex be used?" Additional comment from the review manager: Consider making RTTI customizable. Boost.TypeInfo should be easily usable. In any case document the use of RTTI in the documentation. Joaquín will consider the customizable RTTI, will document that RTTI is required by the library. ------------------ Andrzej Krzemienski (positive review) https://lists.boost.org/Archives/boost/2017/05/234716.php ------------------ [1] "Based on my experience OO-inheritance solutions are faster that using `variant`. As you say below, I was suggesting the alternative design: `variant_collection`." Joaquín: "Some have asked for a variant_collection to be part of Boost.PolyCollection roadmap." [2] "I am not comfortable with per-segment functions having the same name as container-wide functions" Joaquín: "On the contrary, I like name overloading better, because it looks terser yet sufficiently expressive" [3] "I observed that the following small program crashes (assertion fails). According to the documentation this should throw an exception upon insertion rather than firing assertions" Joaquín: I think the assertion will be removed. [4] Commenting c.insert(x) / c.insert(it,x) reference: "And maybe it is just me, but I cannot make the sense of it" Joaquín: There is a typo that will be fixed. Will reword the reference sections into a more digestible form. ------------------ Ion Gaztañaga (positive comment) https://lists.boost.org/Archives/boost/2017/05/234729.php https://lists.boost.org/Archives/boost/2017/05/234745.php ------------------ [1] Model-based polymorphism: "Wouldn't be a good idea to make this model-based polymorphism (or a refined one) public? Maybe the current model needs more work to support additional polymorphism models." Joaquín: I'd be really conservative here and withhold such a big move until real use cases are found. The problem is once this is made public the design of the lib becomes effectively frozen. Will study it for the future if there's demand. [2] Optimize memory-indirection caused by unique_ptr: "segment_type could directly hold the class derived from segment_backend as packed_segment/split_segment will need the same size and alignment requirements regardless of the ConcreteType they hold (as long as they use std::vector). This could improve insertion times and other operations. This optimization could also make easier to fix the following section (allocator propagation)." Joaquín: In principle if the optimization is reasonably implemented t'd be welcome. [3] Allocator propagation: The library does not correctly propagate the allocator to support the scoped allocator model. Joaquín will fix this. [4] In many operations the dynamic type of the object to be inserted or manipulated can be known at compile, so the internal virtual call overhead can be optimized. Specially in "insert" and "emplace", but many other operations that work with a single segment can be optimized as well. Joaquín will review operations and will try to "staticfy" as much as possible. [5] Documentation should reflect some operations, like size<T>(), empty<T>() and others are not constant-time cheap operations. Thorsten suggested: The documentation should defin k = # of segments in container and add in those operations "Complexity: linear in k" as the explanation. Joaquín will document it. --------------- Adam Wulkiewicz (comment, but positive) https://lists.boost.org/Archives/boost/2017/05/234662.php --------------- [1] Polycollection doesn't meet the requirements of C++ container as defined in the standard, specially section (23.2.1.3). Joaquín: The part about 23.2.1.3 is not listed among the differences, will include it. --------------- Hans Dembinski (positive review) https://lists.boost.org/Archives/boost/2017/05/234694.php --------------- [1] "boost::function_collection was not so clear to me. It is nice to keep the narrative of game development going, but like someone said before, I think it would help to give a simpler example" Joaquín will improve the explanation [2] "I felt that the benefit of using boost::function_collection was not so clearly presented as for boost::base_collection. The function pointers are all the same size, so how exactly does the optimisation enter" Joaquín will improve the explanation. [3] "I tried to compile the tests on a Mac with Apple-clang 8.0.0. It worked after I manually specified "cxxflags=-std=c++11" Note from the review manager: No fix was discovered, I suggest working on this as many Apple users will have this problem. --------------- Thorsten Ottosen (positive review) https://lists.boost.org/Archives/boost/2017/05/234697.php --------------- [1] "OO programming and copyability of classes is not something that everybody is going to like. (...) Would it be possible for the library to pick up a private or protected copy-constructor when needed, possible via a friend declaration? (...) being able to have your hierarchy non-copyable while allowing copyability within the container is important IMO." Moveability is already required to store classes in the segment. Joaquín will study the possibility of using a copying traits class to let users customize this point. [2] "I miss range versions of the various iteration patterns so I can use them directly with a range-based for. E.g. instead of" Joaquín will implement it. [3] "Inside the segments you store std::vector. I could easily imagine the need to store something else, (...) Therefore I would love to have a second defaulted argument set to std::vector" Element contiguity is a key property and this customization requires a lot of work. Deferred for the future if there is demand for it. [4] "Implementation of equality: do we need to be set like semantics (two-pass)? Why don't you just delegate to the segments after checking the size?" Joaquín proposed a new slightly better implementation. [5] "tutorial: consider using override where appropriate" Joaquín will review code to use it. [6] "why ==,!= but not <,>,>=, <=" Joaquín followed the interface of std::unordered_set, [Review manager's comment: Consider explaining this in the documentation] [7] "Clarify that boost::poly_collection::for_each <warrior,juggernaut,goblin,std::string,window>( //restituted types c.begin(),c.end(),[&](const auto& x) loops over all elements or only the specific" Joaquín will clarify it. [8] "It could be good to have a performance test of erase in the middle/front." Joaquín will test it. [9] "using the identifier "concept" may require change in the near future?"s Joaquín will change it. [10] "I wouldn't mind seeing separate graphs for 0-300 elements." Joaquín will add it. [11] 2clarify test are without use of reserve" Joaquín will clarify it. [12] The test are testing best possible scenario; a more realistic test would be to copy pointers to an std::vector<base*>, shuffle it and run update on that. Joaquín will consider this, maybe additionally for 1-1000 elements. --------------- Vinnie Falco (Positive review) https://lists.boost.org/Archives/boost/2017/05/234704.php --------------- [1] "Iterators returned by begin<T>() produce a long, ugly compile error when compared against iterators returned by begin<U>() or end<U>()." Joaquín will study the issue. He's not sure if this can be improved. --------------- Edward Diener (positive review) https://lists.boost.org/Archives/boost/2017/05/234762.php --------------- [1] "It is also hard to understand what the advantage of a poly collection of these objects entail over a more normal C++ collection ( vector, array etc. ) of std::function<Signature> objects, since the latter object type already represents a generalized callable construct in C++." Joaquín will think about how to make the intro part more accessible. [2] "I have mentioned previously that I think the documentation should be more specific about the types being used for the boost::function_collection" Joaquín will take these points, and try to improve docs so as to make these aspects clearer. --------------- Brook Milligan (positive review) https://lists.boost.org/Archives/boost/2017/05/234872.php --------------- [1] "The only problem was that the following test cases needed -std=c++14 (rather than c++11) because std::make_unique is not defined for c++11 on that compiler: algorithms, basic_function, and segmented_structure. Perhaps a mention of the need for c++14 in some examples?" Joaquín will fix in the corresponding Jamfile.v2 and will mention it in the examples. --------------- Steven Watanabe (positive review) https://lists.boost.org/Archives/boost/2017/05/234877.php --------------- [1] Several documentation fixes Joaquín will apply recommended fixes [2] Change type_erasure::is_subconcept<type_erasure::assignable<>,Concept2>::value as Boost.TypeErasure was recently extended to support move assignment. [3] Fix "type_erasure::is_subconcept<type_erasure::typeid_<>,Concept>::value " with "typeid_<remove_cv_t<remove_reference_t<T>>> " [4] Fix "static void* subaddress(T& x){return boost::addressof(x);}" as it does not support multiple inheritance [5] Fix "return r(std::forward<Args>(args)...);" that does not correctly handle "void" return types. Joaquín will fix all of them [6] "make_index_sequence<N>" can be implemented more efficiently: Joaquín will find a better implementation. Review manager's comment: see https://stackoverflow.com/questions/17424477/implementation-c14-make-intege… [7] poly_collection is defined in namespace detail, internal functions can be found by ADL Joaquín will try to limit what ADL can find.

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[boost][review] Review of Outcome (starts Fri-19-May)
by charleyb123 . 19 May '17

19 May '17

Hi Everyone, The formal review of Niall Douglas' Outcome library starts today (Fri-19-May) and continues until Sun-28-May. Your participation is encouraged, as the proposed library is uncoupled and focused, and reviewers don't 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 type-safe ultra-lightweight error handling, suitable for low-latency code bases. Key features: *- Makes using std::error_code from C++11's <system_error> more convenient and safe *- Provides high-quality implementation of proposed std::expected<T,E> (on C++20 standards track) *- Good focus on low-latency (with tests and benchmarks) *- Error-handling algorithmic composition with-or-without C++ exceptions enabled *- No dependencies (not even on Boost) This review is timely, as C++17 brings us std::optional<T>. The upcoming std::expected<T,E> (an implementation provided in Outcome) is a generalization of std::optional<T> that provides a <success|fail> value, where the unhappy result is a 'std::error_code' or an instance of "your-chosen-error-type". The library further provides 'outcome<T,error-code,exception-ptr>' for handling <success|error|exception> to safely wrap throwing APIs. Documentation: https://ned14.github.io/boost.outcome/index.html ACCU 2017 talk including design rationale: https://www.youtube.com/watch?v=XVofgKH-uu4 GitHub: https://github.com/ned14/boost.outcome Latest tarball: https://github.com/ned14/boost.outcome/releases/download/ boost_peer_review3/boost.outcome-v1.0-source-201705111650.tar.xz Note: Tarball might be easiest; but if you want to clone from GitHub directly, after the clone you should run the following command to get the source zip exactly: git submodule update --init --recursive 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

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[boost][review] **NEXT WEEK** Review of Outcome (starts Fri-19-May)
by charleyb123 . 11 May '17

11 May '17

Hi Everyone, ** HEADS UP, NEXT WEEK ** The formal review of Niall Douglas' Outcome library starts next week (Fri-19-May to Sun-28-May). Your participation is encouraged, as the proposed library is uncoupled and focused, and reviewers don't 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 type-safe ultra-lightweight error handling, suitable for low-latency code bases. Key features: *- Makes using std::error_code from C++11's <system_error> more convenient and safe *- Provides high-quality implementation of proposed std::expected<T,E> (on C++20 standards track) *- Good focus on low-latency (with tests and benchmarks) *- Error-handling algorithmic composition with-or-without C++ exceptions enabled *- No dependencies (not even on Boost) This review is timely, as C++17 brings us std::optional<T>. The upcoming std::expected<T,E> (an implementation provided in Outcome) is a generalization of std::optional<T> that provides a <success|fail> value, where the unhappy result is a 'std::error_code' or an instance of "your-chosen-error-type". The library further provides 'outcome<T,error-code,exception-ptr>' for handling <success|error|exception> to safely wrap throwing APIs. Documentation: https://ned14.github.io/boost.outcome/index.html ACCU 2017 talk including design rationale: https://www.youtube.com/watch?v=XVofgKH-uu4 GitHub: https://github.com/ned14/boost.outcome Latest tarball: https://github.com/ned14/boost.outcome/releases/ download/boost_peer_review3/boost.outcome-v1.0-source-201705111650.tar.xz Note: Tarball might be easiest; but if you want to clone from GitHub directly, after the clone you should run the following command to get the source zip exactly: git submodule update --init --recursive NEXT WEEK (when the public review is started): 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

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[review] Review of PolyCollection starts today (May 3rd)
by Ion Gaztañaga 02 May '17

02 May '17

Hi everyone, The formal review of Joaquín M. López Muñoz's PolyCollection library starts today. I'd like to encourage your participation as the proposed library is small and focused, and reviewers don't need to be domain experts to appreciate the potential usefulness of the library and propose improvements. PolyCollection implements fast containers of polymorphic objects. Typically, polymorphic objects cannot be stored directly in regular containers and need be accessed through an indirection pointer, which introduces performance problems related to CPU caching and branch prediction. Boost.PolyCollection implements a novel data structure that is able to contiguously store polymorphic objects without such indirection, thus providing a value-semantics user interface and better performance. Three polymorphic collections are provided: * boost::base_collection * boost::function_collection * boost::any_collection dealing respectively with classic base/derived or OOP polymorphism, function wrapping in the spirit of std::function and so-called duck typing as implemented by Boost.TypeErasure. The library can be found here: Incubator: http://blincubator.com/bi_library/polycollection/?gform_post_id=1643 Github: https://github.com/joaquintides/poly_collection and the documentation here: http://rawgit.com/joaquintides/poly_collection/website/doc/html/index.html Please post your comments and review to the boost mailing list (preferably), the Boost Library Incubator. 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 Waiting your reviews! Ion

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[boost] [review] Review of PolyCollection will start in a few days
by Ion Gaztañaga via Boost 30 Apr '17

30 Apr '17

Dear Boost community, The formal review of Joaquín M López Muñoz's PolyCollection library will start on Wednesday, May 3rd and ends on May 12th. This library implements fast containers of polymorphic objects. Typically, polymorphic objects cannot be stored directly in regular containers and need be accessed through an indirection pointer, which introduces performance problems related to CPU caching and branch prediction. Boost.PolyCollection implements a novel data structure that is able to contiguously store polymorphic objects without such indirection, thus providing a value-semantics user interface and better performance. Three polymorphic collections are provided: * boost::base_collection * boost::function_collection * boost::any_collection dealing respectively with classic base/derived or OOP polymorphism, function wrapping in the spirit of std::function and so-called duck typing as implemented by Boost.TypeErasure. If you are interested, you can start preparing your review with the following information: Repositories: Incubator: http://blincubator.com/bi_library/polycollection/?gform_post_id=1643 Github: https://github.com/joaquintides/poly_collection and the documentation here: http://rawgit.com/joaquintides/poly_collection/website/doc/html/index.html See you on Wednesday! Ion _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost

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