June 2015 - Boost - lists.boost.org

[Hana] Formal review
by Bruno Dutra 23 Jun '15

23 Jun '15

Dear all, Following is my review of Hana. - 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. Yes, absolutely, but please read on. - Are you knowledgeable about the problem domain? I've been playing with metaprogramming as a hobby since 2011 when I first came across Boost.MPL. I experimented with a library that implements the unification algorithm at compile time using Boost.MPL for a long time, on and off, and recently I've decided giving a shot at my own implementation of a C++11 version of Boost.MPL. - What is your evaluation of the design? The design seems to be very general and abstract, based on formal mathematical concepts. I've had my dose of FP through SML and lisp, however I've never dug deep into category theory, so I won't venture into judging the way these abstract concepts were translated to C++, but all looks sound to me. I'm very fond of the way type computations are carried out by value through the use of type<> and decltype(). Such an ingenious simplicity. Once one gets it, one realizes how beautifully it merges value and type computations into one. I also like very much the design of compile time constants, their custom _c suffix and operators. To me, that is material for standardization. I would like to point out however, that from the point of view of someone who has basically solely done C++ his entire life, just like myself, Hana can look *very* unfamiliar. I understand it is mostly my fault for not properly having learnt FP before, however I believe I'm not alone among average C++ programmers, so I fear this could prevent many potential users from adopting Hana, simply because one tends to stick to things that look familiar to one. Now I'm not sure that is any easy way around this unfamiliarity. I've seen others pointing out that names could better reproduce the C++ standard library (to what I agree) and perhaps that's indeed all one could do to tighten the gap that separates Hana from mainstream C++ libraries. At any rate, I just felt I should stress this point, to make sure it is not underestimated. - What is your evaluation of the implementation? I've just briefly peeked at the code base out of curiosity and it looks pretty clean and organized. The use of global function objects however intrigues me, why not free functions? I've also found myself stumbling on variable templates. Perhaps that's just me, but really I find they make everything so cryptic. Anyways, I guess it's not Hana's fault to make arguably good use of something that is part of the language. - What is your evaluation of the documentation? I find myself blindly using the search button in hope to find whatever I'm looking for more often than I'd rather do, but perhaps it's just a matter of getting used to how the documentation is organized. One thing I'd like to see improved is the alphabetical index. I'd expect it to be thorough, but at least "is_a" is missing, so I assume a rationale exists to decide what goes there? I think it would be better to list everything exhaustively, so users may rely on the browser's find tool to explore the library. - What is your evaluation of the potential usefulness of the library? At first I was afraid Hana were too academical and abstract to be a good tool for getting down to business, but after playing with it a little bit I can see that, once one gets its design, it does make metaprogramming quite straightforward. I believe however that most users will attain to a very limited subset of functionalities in order to just get their tasks accomplished. So much so, that I'd strongly advise Hana to be split into one highly specialized tool for straightforward metaprogramming and another more abstract halve providing the more generic concepts. This could ease user experience considerably, reducing the novelty presented by Hana and thus tightening the gap I've mentioned before. - Did you try to use the library? With what compiler? Did you have any problems? Yes on Clang 3.6.1. I tried to implement the unification algorithm [1] at compile time using Hana and, though I haven't actually finished, I could see it would be straightforward. In fact I gave up on it when I found a bug which prevented the construction of optional maps, but not too long after I contacted Louis and opened an issue [2] it seems to have already been fixed on develop branch. I didn't test the fix myself though. - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? About 4 hours reading the documentation, another 4 hours trying the library and about 2 hours to write this review. *Bruno C. O. Dutra* [1]: https://en.wikipedia.org/wiki/Unification_(computer_science) [2]: https://github.com/ldionne/hana/issues/149

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[test] Re: [Boost-testing] Develop branch test runners crashing
by Rene Rivera 23 Jun '15

23 Jun '15

Please fix ASAP. On Tue, Jun 23, 2015 at 8:32 AM, Tom Kent <lists(a)teeks99.com> wrote: > Sometime between 22:30 and 03:30 last night (pacific time) all the develop > tests started crashing on windows and linux. > > The tail of results/bjam.log is: > > notice: iostreams: not using bzip2 compression > notice: iostreams: not using bzip2 compression > ..\libs\test\test\Jamfile.v2:59: in docs-example-as-test > *** argument error > * rule boost.test-self-test ( test-rule : test-suite : test-name : > usage-variant ? : pattern_file * : source_files * : extra-libs ? : > extra-options ? ) > * called with: ( : ../doc/examples : : included : : > /D:/t08/run/boost_root/libs/test/doc/examples/boost_test_bitwise.run-fail.cpp > ) > * missing argument test-rule > ..\libs\test\test\Jamfile.v2:18:see definition of rule > 'boost.test-self-test' being called > (builtin): in sequence.transform > ..\libs\test\test\Jamfile.v2:162: in modules.load > D:/t08/run/boost_bb/src/build\project.jam:325: in load-jamfile > D:/t08/run/boost_bb/src/build\project.jam:64: in load > D:/t08/run/boost_bb/src/build\project.jam:145: in project.find > D:/t08/run/boost_bb/src/build\targets.jam:452: in find-really > D:/t08/run/boost_bb/src/build\targets.jam:474: in find > D:/t08/run/boost_bb/src/build\targets.jam:305: in targets-to-build > D:/t08/run/boost_bb/src/build\targets.jam:270: in > class(a)project-target.generate > D:/t08/run/boost_bb/src\build-system.jam:707: in load > D:\t08\run\boost_bb\src/kernel\modules.jam:295: in import > D:\t08\run\boost_bb\src/kernel/bootstrap.jam:139: in boost-build > D:\t08\run\boost_root\boost-build.jam:17: in module scope > > Any thoughts? > > _______________________________________________ > Boost-Testing mailing list > Boost-Testing(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-testing > -- -- Rene Rivera -- Grafik - Don't Assume Anything -- Robot Dreams - http://robot-dreams.net -- rrivera/acm.org (msn) - grafikrobot/aim,yahoo,skype,efnet,gmail

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Re: [boost] [test] Develop branch test runners crashing
by Andrey Semashev 23 Jun '15

23 Jun '15

On Tue, Jun 23, 2015 at 4:32 PM, Tom Kent <lists(a)teeks99.com> wrote: > Sometime between 22:30 and 03:30 last night (pacific time) all the develop > tests started crashing on windows and linux. > > The tail of results/bjam.log is: > > notice: iostreams: not using bzip2 compression > notice: iostreams: not using bzip2 compression > ..\libs\test\test\Jamfile.v2:59: in docs-example-as-test > *** argument error > * rule boost.test-self-test ( test-rule : test-suite : test-name : > usage-variant ? : pattern_file * : source_files * : extra-libs ? : > extra-options ? ) > * called with: ( : ../doc/examples : : included : : > /D:/t08/run/boost_root/libs/test/doc/examples/boost_test_bitwise.run-fail.cpp > ) > * missing argument test-rule > ..\libs\test\test\Jamfile.v2:18:see definition of rule > 'boost.test-self-test' being called > (builtin): in sequence.transform > ..\libs\test\test\Jamfile.v2:162: in modules.load > D:/t08/run/boost_bb/src/build\project.jam:325: in load-jamfile > D:/t08/run/boost_bb/src/build\project.jam:64: in load > D:/t08/run/boost_bb/src/build\project.jam:145: in project.find > D:/t08/run/boost_bb/src/build\targets.jam:452: in find-really > D:/t08/run/boost_bb/src/build\targets.jam:474: in find > D:/t08/run/boost_bb/src/build\targets.jam:305: in targets-to-build > D:/t08/run/boost_bb/src/build\targets.jam:270: in > class(a)project-target.generate > D:/t08/run/boost_bb/src\build-system.jam:707: in load > D:\t08\run\boost_bb\src/kernel\modules.jam:295: in import > D:\t08\run\boost_bb\src/kernel/bootstrap.jam:139: in boost-build > D:\t08\run\boost_root\boost-build.jam:17: in module scope > > Any thoughts? Looks like a Boost.Test issue.

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Develop branch test runners crashing
by Tom Kent 23 Jun '15

23 Jun '15

Sometime between 22:30 and 03:30 last night (pacific time) all the develop tests started crashing on windows and linux. The tail of results/bjam.log is: notice: iostreams: not using bzip2 compression notice: iostreams: not using bzip2 compression ..\libs\test\test\Jamfile.v2:59: in docs-example-as-test *** argument error * rule boost.test-self-test ( test-rule : test-suite : test-name : usage-variant ? : pattern_file * : source_files * : extra-libs ? : extra-options ? ) * called with: ( : ../doc/examples : : included : : /D:/t08/run/boost_root/libs/test/doc/examples/boost_test_bitwise.run-fail.cpp ) * missing argument test-rule ..\libs\test\test\Jamfile.v2:18:see definition of rule 'boost.test-self-test' being called (builtin): in sequence.transform ..\libs\test\test\Jamfile.v2:162: in modules.load D:/t08/run/boost_bb/src/build\project.jam:325: in load-jamfile D:/t08/run/boost_bb/src/build\project.jam:64: in load D:/t08/run/boost_bb/src/build\project.jam:145: in project.find D:/t08/run/boost_bb/src/build\targets.jam:452: in find-really D:/t08/run/boost_bb/src/build\targets.jam:474: in find D:/t08/run/boost_bb/src/build\targets.jam:305: in targets-to-build D:/t08/run/boost_bb/src/build\targets.jam:270: in class(a)project-target.generate D:/t08/run/boost_bb/src\build-system.jam:707: in load D:\t08\run\boost_bb\src/kernel\modules.jam:295: in import D:\t08\run\boost_bb\src/kernel/bootstrap.jam:139: in boost-build D:\t08\run\boost_root\boost-build.jam:17: in module scope Any thoughts?

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[coroutine2] Difference between coroutine and coroutine2
by Aaron Levy 23 Jun '15

23 Jun '15

Are boost::coroutines::symmetric_coroutine<> and boost::coroutines::asymmetric_coroutine<> part of the coroutine library or coroutine2 library. Besides being C++14-only, in what ways does coroutine2 differ from coroutine? -- Aaron Levy aaron.levy(a)yandex.com

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[Optional] Monadic bind
by Tobias Loew 23 Jun '15

23 Jun '15

While playing around with boost::optionals I had code like the following struct A { ... int i; ... }; boost::optional a; // do something with 'a' // optional-projection to a::i boost::optional<int> a_i; if(a) a_i = a->i; which seemed quite verbose for something that's rather natural in functional languages: boost::optional is a monadic structure, which lifts a type T by extending it with a new bottom-element (represented by the empty optional<T>), thus it should also have a "bind" and a "map"-equivalent, which could be implemented for instance as as member functions of optional template<class B> auto bind(B&& binder) const -> boost::optional<typename std::decay<decltype(std::bind(binder, get())())>::type> { if(this->is_initialized()) { return std::bind(binder, get())(); } else { return boost::none; } } and template<class B> auto map(B&& f) const -> boost::optional<typename std::decay<decltype(std::bind(f, get())())>::type> { if(this->is_initialized()) { return std::bind(f, get())(); } else { return boost::none; } } where map lifts f from A->B to optional -> optional< B > and applies 'this' to it. This would allow things like boost::optional a; auto a_i = a.map(&A::i); // "optional-projection"; type of a_i is boost::optional<int> Tobias -- View this message in context: http://boost.2283326.n4.nabble.com/Optional-Monadic-bind-tp4677431.html Sent from the Boost - Dev mailing list archive at Nabble.com.

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[test] Where we are with the new version?
by Vicente J. Botet Escriba 23 Jun '15

23 Jun '15

Hi, I'm wondering if the new Boost.Test will be merged one day to the master branch. Best, Vicente

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[config] 'requres' doesn't take differing -std into account
by Peter Dimov 22 Jun '15

22 Jun '15

I have, in my user-config.jam, using gcc ; feature.subfeature toolset gcc : std : cxx0x cxx11 cxx1y cxx14 : optional composite propagated ; feature.compose <toolset-gcc:std>cxx0x : <cxxflags>-std=c++0x ; feature.compose <toolset-gcc:std>cxx11 : <cxxflags>-std=c++11 ; feature.compose <toolset-gcc:std>cxx1y : <cxxflags>-std=c++1y ; feature.compose <toolset-gcc:std>cxx14 : <cxxflags>-std=c++14 ; using clang : : : <cxxflags>-Wno-variadic-macros <cxxflags>-Wno-c99-extensions ; feature.subfeature toolset clang : std : cxx0x cxx11 cxx1y cxx14 : optional composite propagated ; feature.compose <toolset-clang:std>cxx0x : <cxxflags>-std=c++0x ; feature.compose <toolset-clang:std>cxx11 : <cxxflags>-std=c++11 ; feature.compose <toolset-clang:std>cxx1y : <cxxflags>-std=c++1y ; feature.compose <toolset-clang:std>cxx14 : <cxxflags>-std=c++14 ; This allows me to use toolset=clang (without -std) and toolset=clang-cxx11 (with -std=c++11). The 'requires' rule however caches the results of the configuration check when I run with toolset=clang, and then when I rerun with toolset=clang-cxx11, it uses the cached values, which is wrong. I use something like run test.cpp : : : [ requires cxx11_variadic_templates cxx11_template_aliases cxx11_hdr_type_traits cxx11_hdr_tuple ] ;

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[hana] question
by Christophe Henry 22 Jun '15

22 Jun '15

Hi Louis, I'm experimenting with hana for the review and have one question. I can fold with boost::hana::fold.left(boost::mpl::vector<...>{}...) Do you have a way to iterate on elements of a mpl::set? Thanks, Christophe

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[Boost] [Hana] Formal review for Hana
by Glen Fernandes 22 Jun '15

22 Jun '15

Dear Boost community, The formal review of Louis Dionne's Hana library begins today,10th June and ends on 24th June. Hana is a header-only library for C++ metaprogramming that provides facilities for computations on both types and values. It provides a superset of the functionality provided by Boost.MPL and Boost.Fusion but with more expressiveness, faster compilation times, and faster (or equal) run times. To dive right in to examples, please see the Quick start section of the library's documentation: http://ldionne.com/hana/index.html#tutorial-quickstart Hana makes use of C++14 language features and thus requires a C++14 conforming compiler. It is recommended you evaluate it with clang 3.5 or higher. Hana's source code is available on Github: https://github.com/ldionne/hana Full documentation is also viewable on Github: http://ldionne.github.io/hana To read the documentation offline: git clone http://github.com/ldionne/hana --branch=gh-pages doc/gh-pages For a gentle introduction to Hana, please see: 1. C++Now 2015: http://ldionne.github.io/hana-cppnow-2015 (slides) 2. C++Con 2014: https://youtu.be/L2SktfaJPuU (video) http://ldionne.github.io/hana-cppcon-2014 (slides) We encourage your participation in this review. At a minimum, kindly state: - Whether you believe the library should be accepted into Boost * Conditions for acceptance - Your name - Your knowledge of the problem domain. You are strongly encouraged to also provide additional information: - What is your evaluation of the library's: * Design * Implementation * Documentation * Tests * Usefulness - Did you attempt to use the library? If so: * Which compiler(s) * What was the experience? Any problems? - How much effort did you put into your evaluation of the review? We await your feedback! Best, Glen

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