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[sort] Timsort review reminder
by Steven Ross 11 Jun '17

11 Jun '17

The review for C++ Timsort in Boost is ongoing and will 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

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[static_views] [gsoc17] Proposal for a library
by Tom Westerhout 10 Jun '17

10 Jun '17

Hi! I'm Tom Westerhout, one of this year's GSoC interns. The module I'm planning to work on, StaticViews, is essentially a subset of Ranges TS optimised for usage with compile-time homogeneous datasets. It can be used to implement compile-time associative maps, compile-time checking of non-type constraints, and compile-time generation of datasets from other compile-time datasets. Some more explanation and motivating examples are on this page: https://boostgsoc17.github.io/static-map/doc/123_build/html/getting_started… Do you think this would be a worthwhile addition to Boost? Is the choice to use Ranges TS as inspiration for the API wise, or would a different API (please, suggest one) be better? All comments are welcome. Thanks in advance! Tom

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Repeated super project commits
by Daniel James 10 Jun '17

10 Jun '17

Hi, You might noticed that some of today's super project commits were repeated. I was working on a change to do one commit per push event, and it went a bit wrong. It turns out there was an existing bug, which meant the script wasn't always updating the position in the event queue. I fixed it while writing the new version, but assumed it was a new bug that I'd introduced today. So when the new version started, it replayed the events since the position was last updated. I backed out the change and I'm going to try to make the script a bit more robust before changing it again - even without the bug, a similar thing could happen if someone manually updated a submodule in the super project. Because the commits were all in a single push, and the last commit was correct, it shouldn't cause any real problems, but there are a few wonky commits in the history, so sorry about that. Because of the way the script worked, the bug only affects that batch of commits, older commits are fine. Daniel

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Re: [boost] [Boost-testing] [EXTERNAL] Run.py test failure 'minimal' is an invalid property
by Tom Kent 10 Jun '17

10 Jun '17

On Wed, Jun 7, 2017 at 10:39 PM, Belcourt, Kenneth via Boost-Testing < boost-testing(a)lists.boost.org> wrote: > Hi, > > To followup with more info on this issue, testing is broken on master when > building on the Mac, though not sure why. Here’s what works okay: > > python run.py --tag=develop --runner="Sandia-clang-3.8" > --toolset=clang-darwin --pjl-toolset=darwin --bjam-options="-j8” > > and what fails (same command with —tag=master): > > python run.py —tag=master --runner="Sandia-clang-3.8" > --toolset=clang-darwin --pjl-toolset=darwin --bjam-options="-j8" > > The error from the failed master build is the error below. It seems to be > related to the context library use of alias (highlighted below). Are there > perhaps boost build or context changes that need to be merged to master > into order to fix this issue? From what I can tell, testing master on > MacOS is hosed. > > Noel > > > On Jun 7, 2017, at 6:03 PM, Belcourt, Kenneth via Boost-Testing < > boost-testing(a)lists.boost.org> wrote: > > > > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/property.jam:529: > in property.translate from module property > > error: 'minimal' is not a valid property specification > > /Users/jenkins/slave/workspace/build-tpls/boost_bb/ > src/build/property-set.jam:432: in property-set.create-from-user-input > from module property-set > /Users/jenkins/slave/workspace/build-tpls/boost_bb/ > src/build/property-set.jam:484: in property-set.refine-from-user-input > from module property-set > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/targets.jam:1619: > in targets.main-target-requirements from module targets > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/alias.jam:65: > in test-suite from module alias > *../libs/context/test/Jamfile.v2:97: in modules.load from module * > Jamfile</Users/jenkins/slave/workspace/build-tpls/boost_ > root/libs/context/test> > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/project.jam:325: > in load-jamfile from module project > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/project.jam:64: > in load from module project > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/project.jam:145: > in project.find from module project > Jamfile.v2:118: in run-tests from module Jamfile</Users/jenkins/slave/ > workspace/build-tpls/boost_root/status> > Jamfile.v2:171: in modules.load from module Jamfile</Users/jenkins/slave/ > workspace/build-tpls/boost_root/status> > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/project.jam:325: > in load-jamfile from module project > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/project.jam:64: > in load from module project > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/project.jam:145: > in project.find from module project > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build-system.jam:535: > in load from module build-system > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/kernel/modules.jam:295: > in import from module modules > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/kernel/bootstrap.jam:139: > in boost-build from module > /Users/jenkins/slave/workspace/build-tpls/boost_root/boost-build.jam:17: > in module scope from module > > I see the same error for master on linux and windows runners. Tom

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[review] **NEXT WEEK** Review of Nowide (Unicode) Mon. 12th -> Wed. 21st June
by Frédéric Bron 10 Jun '17

10 Jun '17

Hi Everyone, ** HEADS UP, NEXT WEEK'S REVIEW ** The formal review of Artyom Beilis' Nowide library starts next week (Mon. 12-June to Wed. 21-June). Your participation is encouraged, as the proposed library is uncoupled and focused. Nowadays, everyone needs to handle Unicode but this is very difficult using only the standard library in a platform independant way. Nowide offers a very simple way to handle Unicode the same way on Windows/MacOS/Linux. Key features: * work with UTF-8 in your code, Nowide converts to OS encoding * Easy to use functions for converting UTF-8 to/from UTF-16 * A class to fixing argc, argc and env main parameters to use UTF-8 * UTF-8 aware functions: - stdio.h functions (fopen, freopen, remove, rename) - stdlib.h functions (system, getenv, setenv, unsetenv, putenv) - fstream (filebuf, fstream/ofstream/ifstream) - iostream (cout, cerr, clog, cin) Documentation: http://cppcms.com/files/nowide/html GitHub: https://github.com/artyom-beilis/nowide git clone https://github.com/artyom-beilis/nowide.git Latest tarball: get it from GitHub (Download as zip) 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? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. 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. Frédéric

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[Format] User-defined literals for Boost.Format
by Корсунов Игорь 09 Jun '17

09 Jun '17

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Re: [boost] [property_tree] Issue: erase is corrupting the tree
by lukas.exler＠barclays.com 09 Jun '17

09 Jun '17

The minimal code that crashes is: boost::property_tree::ptree loadedJSON; boost::property_tree::read_json("animalList.json", loadedJSON); auto assoc_it = loadedJSON.find("animals"); auto it = loadedJSON.to_iterator(assoc_it); it = it->second.begin(); it++; // move to second item loadedJSON.erase(it); boost::property_tree::write_json("shorterList.json", loadedJSON); Where content of "animalList.json" file is: { "animals" : ["fox","dog","cat"] } -----Original Message----- From: Mert Büyüktuncay [mailto:mert.buyuktuncay@sestek.com] Sent: Tuesday, June 06, 2017 9:22 AM To: boost(a)lists.boost.org Cc: Exler, Lukas: IT (PRG) Subject: RE: [property_tree] Issue: erase is corrupting the tree This mail originated from outside our organisation Do you use "it" iterator after the call to erase in that case you shall use it = loadedJSON.erase(it); instead of it++ If this is not your problem you can share a little more code for us to see in detail what is happening here. May be the code up to the point where "write_json" is being called. Regards Mert -----Original Message----- From: Boost [mailto:boost-bounces@lists.boost.org] On Behalf Of Lukas via Boost Sent: Monday, June 5, 2017 4:08 PM To: boost(a)lists.boost.org Cc: lukas.exler(a)barclays.com Subject: [boost] [property_tree] Issue: erase is corrupting the tree I have following JSON structure loaded into boost::property_tree: { "animals" : ["fox","dog","cat"] } I'm trying to delete the second item from the array by: auto assoc_it = loadedJSON.find("animals"); auto it = loadedJSON.to_iterator(assoc_it); it = it->second.begin(); it++; // move to second item loadedJSON.erase(it); After this, when I try to use boost::property_tree::write_json to write the JSON back the app crashes. Do I use the property tree in a wrong way, or is there a bug? Thanks, Lukas. _______________________________________________ This message is for information purposes only, it is not a recommendation, advice, offer or solicitation to buy or sell a product or service nor an official confirmation of any transaction. It is directed at persons who are professionals and is not intended for retail customer use. Intended for recipient only. This message is subject to the terms at: www.barclays.com/emaildisclaimer. For important disclosures, please see: www.barclays.com/salesandtradingdisclaimer regarding market commentary from Barclays Sales and/or Trading, who are active market participants; and in respect of Barclays Research, including disclosures relating to specific issuers, please see http://publicresearch.barclays.com. _______________________________________________ _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost Bu elektronik posta mesajı ve ekleri sadece gönderildiği kişi veya kuruma özeldir ve gizli bilgiler içerebilir. Eğer bu mesajı hataen aldıysanız lütfen bu durumu gönderen kişiye derhal bildiriniz ve mesajı sisteminizden siliniz. Eğer doğru kişiye ulaşmadığını düşünüyorsanız, bu mesajın gizlenmesi, yönlendirilmesi, kopyalanması veya herhangi bir şekilde kullanılması yasaktır. Internet iletişiminde güvenlik ve hatasız gönderim garanti edilemeyeceğinden, mesajın yerine ulaşmaması, geç ulaşması, içeriğinin bozulması ya da mesajın virüs taşıması gibi problemler oluşabilir. Gönderen taraf bu tip sorunlardan sorumlu tutulmaz. SESTEK Ses ve İletişim Teknolojileri A.Ş. www.sestek.com<http://www.sestek.com> This e-mail message and any attachments are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this message in error, please notify the sender immediately and delete it from your system. If you are not the intended recipient you are hereby notified that any dissemination, forwarding, copying or use of any of the information is prohibited. Internet communications cannot be guaranteed to be secure or error-free as information could be intercepted, corrupted, lost, arrive late or contain viruses. The sender therefore does not accept liability for any errors or omissions in the context of this message which arise as a result of Internet transmission SESTEK INC. www.sestek.com <http://www.sestek.com> Bu elektronik posta mesajı ve ekleri sadece gönderildiği kişi veya kuruma özeldir ve gizli bilgiler içerebilir. Eğer bu mesajı hataen aldıysanız lütfen bu durumu gönderen kişiye derhal bildiriniz ve mesajı sisteminizden siliniz. Eğer doğru kişiye ulaşmadığını düşünüyorsanız, bu mesajın gizlenmesi, yönlendirilmesi, kopyalanması veya herhangi bir şekilde kullanılması yasaktır. Internet iletişiminde güvenlik ve hatasız gönderim garanti edilemeyeceğinden, mesajın yerine ulaşmaması, geç ulaşması, içeriğinin bozulması ya da mesajın virüs taşıması gibi problemler oluşabilir. Gönderen taraf bu tip sorunlardan sorumlu tutulmaz. SESTEK Ses ve İletişim Teknolojileri A.Ş. www.sestek.com<http://www.sestek.com> This e-mail message and any attachments are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this message in error, please notify the sender immediately and delete it from your system. If you are not the intended recipient you are hereby notified that any dissemination, forwarding, copying or use of any of the information is prohibited. Internet communications cannot be guaranteed to be secure or error-free as information could be intercepted, corrupted, lost, arrive late or contain viruses. The sender therefore does not accept liability for any errors or omissions in the context of this message which arise as a result of Internet transmission SESTEK INC. www.sestek.com <http://www.sestek.com> _______________________________________________ This message is for information purposes only, it is not a recommendation, advice, offer or solicitation to buy or sell a product or service nor an official confirmation of any transaction. It is directed at persons who are professionals and is not intended for retail customer use. Intended for recipient only. This message is subject to the terms at: www.barclays.com/emaildisclaimer. For important disclosures, please see: www.barclays.com/salesandtradingdisclaimer regarding market commentary from Barclays Sales and/or Trading, who are active market participants; and in respect of Barclays Research, including disclosures relating to specific issuers, please see http://publicresearch.barclays.com. _______________________________________________

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What is the process for adding a library suggestion?
by Adrian H 07 Jun '17

07 Jun '17

I have a suggestion for adding something to the boost library. It is simple but I believe that it would be useful. Do I just post it here or is there some process? Thanks, A -- ======================================== Adrian Hawryluk BSc. Computer Science ---------------------------------------- Specialising in: OOD Methodologies in UML OOP Methodologies in C, C++ and more RT Embedded Programming GUI Development ========================================

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svn.boost.org schedule maintenance - DOWN TIME
by Michael Caisse 07 Jun '17

07 Jun '17

Hi all - svn.boost.org is scheduled for maintenance on June 8 from 1700 - 1900 UTC. Expect outages for Trac during this time. Happy coding! michael -- Michael Caisse Ciere Consulting ciere.com

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[review] Outcome Review Report
by charleyb123 . 07 Jun '17

07 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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