June 2015 - Boost - lists.boost.org

Re: [boost] [Hana] Formal review
by David Sankel 22 Jun '15

22 Jun '15

On Wed, Jun 10, 2015 at 3:19 AM, Glen Fernandes <glen.fernandes(a)gmail.com> wrote: > - Whether you believe the library should be accepted into Boost > * Conditions for acceptance > Yes, I think it should be accepted into Boost. The one condition is that the library works with release versions of at least two different mainstream C++ compilers. More on that later... > - Your name > David J. Sankel > - Your knowledge of the problem domain. > I've written numerous libraries that make use of Boost.MPL and Boost.Fusion. I also have quite a bit of functional programming expertise. > > You are strongly encouraged to also provide additional information: > - What is your evaluation of the library's: > * Design > The core technique of combining value and type expressions is solid and makes metaprogramming easier and, as a bonus, improves compilation speeds. My one question, as I read though the implementation, is "can the core benefits of this library be achived with a simpler 'light' version of this implementation?". While I appreciate the attempt to encode a Haskell-style typeclass hierarchy, I feel like that is not the core competency of hana and should be a separate library and discussion. As it is, this is a 32k header mega library. I'd prefer several small, highly-targeted, highly-composable libraries. > * Implementation > The code itself looks to be well structured and well documented. Unfortunately hana only works with one compiler: clang. While I agree that Boost shouldn't need to support Visual C++ 6.0 anymore, I believe this is going too far in the opposite direction. The home page states that boost libraries "are intended to be widely useful, and usable across a broad spectrum of applications". I've always interpreted that statement to be in a practical rather than theoretical sense and I don't think hana meets that criteria. Many other Boost authors have made heroic efforts to meet that criteria and the reputation of Boost is due, in no small part, to those efforts. I do appreciate the argument that making use of new features encourages compiler implementers to implement then. I maintain, however, that this isn't Boost's job. Boost provides high quality libraries that the every-day Joe C++ developer can benefit from. That being my position on the issue, my acceptance vote is conditional on hana supporting at least two released versions of mainstream compilers. Given that gcc support seems pretty close, that shouldn't be hard to achieve. * Documentation > Looks good. > * Tests > I didn't evaluate these. I tried, but failed, to build the code and filed related issues. I'm assuming the problems are minor and straightforward to fix. * Usefulness > Maybe in a couple years for me. Without VS 2015 support at least, I'm going to be waiting a while. - Did you attempt to use the library? Yes. Started working through the getting started examples. > If so: > * Which compiler(s) > clang 3.6.1 > * What was the experience? Any problems? > Nothing more to add. I filed an issues for all problems encountered and they seemed minor. > - How much effort did you put into your evaluation of the review? > I attended both of Louis's talks, skimmed through the documentation, attempted to build, and read portions of the code. -- David Sankel

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Attn: Volodya.. Re: [config] 'requres' doesn't take differing -std into account
by Rene Rivera 22 Jun '15

22 Jun '15

On Sun, Jun 21, 2015 at 8:11 PM, Edward Diener <eldiener(a)tropicsoft.com> wrote: > On 6/21/2015 10:19 AM, Peter Dimov wrote: > >> 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 believe the same problem is causing predef-check problems in the predef > library because I have seen local errors using predef-check which also says > that a previous calculation on another toolset has been cached and is being > reused, even when the toolset changes. Somehow the incorrect cached value > is being retained by Boost Build even when the toolset value changes and a > new calculation needs to be made. But like many other people I don't know > nearly enough about Boost Build to figure out what it is doing. I must confess I don't know the rationale for limiting the feature set for config checks. We have to see what Volodya says about this. -- -- 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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[release] policy not to add C++14 libraries
by Oliver Kowalke 21 Jun '15

21 Jun '15

Hi, I'm wondering if C++14 libraries will not be added to the boost release? Oliver

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[Boost] [Hana] Announcing Hana's formal review next week (June 10th)
by Glen Fernandes 21 Jun '15

21 Jun '15

Dear Boost community, The formal review of Louis Dionne's Hana library starts Monday, 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.[1] 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 - 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? [1] A note for Windows users: As mentioned, Hana requires a C++14 conforming compiler. If you would like to try it, a VM with Linux and clang 3.5 is a fairly painless option. Some users have also reported success with using Clang 3.5 on Windows. If you would like assistance configuring the former option, feel free to reach out to us for this. Best, Glen

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needs coroutine2 a review?
by Oliver Kowalke 21 Jun '15

21 Jun '15

coroutine2 is a C++14-only library, providing cleaner code (maintainability) + it fixes some issues (moveable-only parameters). boost.coroutine will be deprecated. The conclusion of the last discussion ( http://boost.2283326.n4.nabble.com/transforming-ex-boost-lib-into-C-11-only…) was to establish coroutine2 as a separate lib beside of boost.coroutine - similar to boost.signals(2). I'm wondering if coroutine2 needs a review, even if the interface remains the same compared to boost.coroutine. Oliver

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[coroutine2] search for review manager (mini-review)
by Oliver Kowalke 21 Jun '15

21 Jun '15

Hi, is there anyone wishing to help with mini review and become a review manager? coroutine2 is a C++14 implementation of boost.coroutine. github: https://github.com/boostorg/coroutine2 docu: http://olk.github.io/libs/coroutine2/doc/html/ best regardds, Oliver

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[coroutine2] add to testing
by Oliver Kowalke 21 Jun '15

21 Jun '15

Hi, I'm uncertain if boost.coroutine2 (C++11-only) will be part to the 1.58 release - a git-submodule exists but not at the list for the regression tests (I've opened a pull-request to boostorg/boost). Could you tell me the status of boost.coroutine2?! thx, Oliver

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[Hana] Review
by Roland Bock 20 Jun '15

20 Jun '15

Hi, Here are my review results: - Whether you believe the library should be accepted into Boost Yes. - Your name Roland Bock - Your knowledge of the problem domain. On the one hand, I do believe to have some knowledge in TMP, being the author of sqlpp11. I have made some minor contributions to early versions of Hana, discussing implementations of type sets and all/any/none. I experimented with the MPL for quite some time before the advent of C++11... On the other hand, I am almost totally blank when it comes to Haskell or Fusion. - What is your evaluation of the library's: * Design Awesome. Using template variables to turn types into objects and then treating types and values the same way in most places is very cool. * Implementation I haven't spent too much time on the implementation. I read code around hana::string and hana::all. It was nicely structured and quite readable. * Documentation Impressive already. With all the input from the reviews coming in, it will become even better. I found navigation/searching a bit awkward sometimes. Personally, I would like more cross links/tables. E.g. functions working with Set (Louis already created an issue on github for this). * Tests To be honest, I did not look at them. * Usefulness We'll see what comes out of it. Which libraries are actually going to use Hana. I'll give it a try with sqlpp11. As others have stated, it might be a bit too much even. BUT, regardless of how many projects will actually use it, Hana will force some compiler teams to go to great lengths to be able to compile the library. It might also become a benchmark in terms of compile time and the number of generated instructions. Also, Hana contains a wealth of design ideas, tricks and knowledge for anybody who needs to solve a particular compile time problem. I am sure that many library authors and other developers will benefit from this Hana being available, maintained and developed within Boost. And Hana has minimal dependencies (just a handful of headers from the standard library). Thus Hana might help to change the impression that many people have of Boost (coming from many established, older Boost libraries): Awesomely cool stuff, but dependencies from all nine levels of hell (aka, you can look, but you better not touch). To sum it up: Usefulness? Very! - Did you attempt to use the library? If so: * Which compiler(s)? clang-3.5.1 * What was the experience? Any problems? As described in an earlier mail: - I tried to use Hana's string UDL (the gcc/clang hack) but failed. Hana is not to blame here, it is rather because of shortcomings in the C++ core language. - I thought about using Hana's all/any/none, but my own versions were proven (by Louis himself) to be outstandingly fast, so no reason to switch - I thought of switching to Hana's compile time sets, but that seemed like a tough thing to do considering that I am using type sets and Hana is using value sets. Louis showed samples from Zach Laine which would make the transition easier. Actually, something like this should be part of the documentation. Maybe it might make sense to have a collection of migration examples (before/after code)? That might not sound very successful, but I think it was: While researching how I could achieve my goals I learned a lot about the library. - How much effort did you put into your evaluation of the review? Several hours of reading and some tests in combination with sqlpp11. Remark on compilers: There was some argument as to whether Boost could contain a library that can only be compiled by one compiler (actually, maybe two in this case). My personal opinion is: Yes, Boost could and should do that if the library complies with a modern version of the C++ standard. Compiler teams take pride in being able to compile boost. If they cannot compile a Boost library, they will try to accomplish that ASAP. This is going to help everyone. It is good to have libraries in Boost that challenge compilers even to the point of breaking one or the other. Trying to work around compiler bugs does not seem right for new libraries. Thanks to Louis for his library and to Glen for managing the review! Best, Roland

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[Hana] Formal Review
by Krzysztof Jusiak 20 Jun '15

20 Jun '15

Hi, Please find my review below. - Whether you believe the library should be accepted into Boost Definitely YES. IMHO, one of the most complete boost proposals. - Your name Krzysztof Jusiak - Your knowledge of the problem domain. I've been using MPL and Fusion for about 6 years in commercial projects, I also have been using C++11 /C++14 template features in open source projects since they become available. I have some experience with Haskell and other functional programming languages. You are strongly encouraged to also provide additional information: - What is your evaluation of the library's: * Design Library seems to be very well designed. Used patterns are easy to follow. There is a distinction between algorithms, data types and concepts. The approach is really easy to follow for Haskell programmers, but, on the other hand, C++ influence might be noticed as well. Seems to be very straight forward mix of approaches. * Implementation Source Code: First impression, it's a lot of it! But it's easy to follow. Helpful directory structure makes it much easier to handle. Big thanks for changing the naming as well, `snoc`, `cons` and so on, could have been hard to follow for C++ programmers. Implementation consist of a high quality source code. There are few small things, which are not as straight forward. * a lot of fwd (assume forward declaration files) files have implementation inside, which is a bit confusing * a bit annoying `#ifdef BOOST_HANA_DOXYGEN_INVOKED` all over the source code Performance: I have to admit, I really appreciate the library handled this topic. MPL/Fusion, although, very useful are really hard to introduce in commercial projects in the large scale. I do remember using Boost.MSM for a bit, but the company had to give up on it, because having a transition table with more than 200 entries wasn't easy to deal with, to say at least. Having sad that, I think Hana can still improve the compilation times. I didn't even bother to compare it to MPL or Fusion, because there is no comparison there, but with C++ template tricks there is. Compilation time: So I have written simple example to compare `Hana Map` and `C++ Tricks Map`. Please notice, I compared map with 1000 entries! Hehehe, can anyone imagine that with MPL or Fusion? Results are here: tricks_map: https://gist.github.com/krzysztof-jusiak/cb6633d6c11572c33928 0m0.095s hana_map: https://gist.github.com/krzysztof-jusiak/949d3916d84c466b80c5 0m11.105s So, Hana seems to be much slower, but still not really slow. It's not hours, just a few seconds, which IMHO, it's a huge improvement already. run-time: Haven't checked this part as deeply. Diagnostic Messages: Really popular topic recently and Hana made a huge progress with it as well. Concepts helps a lot, but, unfortunately, there is always a call stack following the error message. Sometimes, such approach is desired, but would be great not to see all Hana's internals, especially with recursive algorithms. Tested error message: https://gist.github.com/krzysztof-jusiak/bfc51747d083e140772d I also had some issue, when some include was missing. Compilation was fine, but the computation was run-time only. Would be great to somehow handle this problem. It's really tricky to understand, why it doesn't work as expected. Debugging: Guess, in this matter, there is still no much progress. I tried Hana with MetaShell and TempLight, but, although, it was way better experience, it still was hard to debug the library. What about run-time algorithms? I haven't checked how hard it is to debug them, but I suspect it will be the same story as with STL, unless some magic is happening in HANA under the hood? * Documentation Documentation is really impressive. Honestly, love the search button! Would like to see more copy/paste examples tho. I'm really inpatient sometimes and when have to find part of the example at one place and figure out includes I do get easily annoyed. Related to that, would be great to always see which file has to be included for anything which is not included by `boost/hana.hpp`. As already mentioned, would be better to use hana::... instead of having an assumption for `using namespace boost::hana`. I would also add some tutorial for less experienced users with explanations what the monad is and how functional programming concepts are applied in Hana. * Tests Impressive unit tests collection. Unfortunately, they are not that easy to follow. Approach like: // check a { } // check b { } is not the best and I would encourage to add separate tests for both cases. Would be great to have CI tests for run-time performance. I have seen charts, but the build could break when performance degradation occurred. * Usefulness With C++11/C++14/C++17 template metaprogramming become a lot easier and a a lot of stuff might be written without need of TMP library at all. However, Hana is more than that, and I find it very useful. MPL and Fusions are/were extremely helpful and Hana is a huge step forward. *Frankly speaking, I would replace `std::tuple` with `hana::tuple` straight away.* - Did you attempt to use the library? If so: * Which compiler(s) Clang 3.6/Clang 3.7 + libc++ (on linux/mac/windows) -> worked fine Tried on GCC-5.1 (on linux) without any success -> didn't link, but this issue is well known already Tried on MSVC 2015-RC (just for a sake of trying -> didn't work ;) * What was the experience? Any problems? I haven't experienced any blockers whilst trying the library. The only problem for me, is lack of support for MSVC. A lot of commercial projects requires MSVC as much as Clang/GCC. - How much effort did you put into your evaluation of the review? I have been watching/trying Hana since April last year when I started to implement C++14 version of proposed boost.di library. I tried to re-implement C++03 version using Hana, but back then, Hana was crashing very often. Therefore, I decided to use plain C++14 features instead. I also went through all the source code/documentation/examples as well as played with the library. Thanks Louis for a great library! Kris

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[type_traits] Another big update in develop
by John Maddock 20 Jun '15

20 Jun '15

Just a heads up in case it causes any issues: type_traits has had another big update in develop - added several new traits is_constructible, is_assignable etc which were needed to fix bugs in other traits - and changed most of the has_nothrow and has_trivial traits to make use of these. Also added more test cases to cover the issues where these were defective before. Please do let me know if you spot any unexpected breakages. John.

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