June 2015 - Boost - lists.preview.boost.org

[hana] Review
by edouard＠fausse.info 16 Jun '15

16 Jun '15

Dear all, Please find attached my review of Hana. > - Whether you believe the library should be accepted into Boost > * Conditions for acceptance Definitely yes. I just have a very minor remark considering the documentation. > - Your name Edouard Alligand > - Your knowledge of the problem domain. I have been writing C++ professionally for 15 years and done a lot of TMP for many software project, for things such as compile-time introspection for serialization, enhanced checks at compile-time to improve correctness and compile-time pre-computations. I've done that with Boost.MPL, Boost.Fusion and some custom MPL. > You are strongly encouraged to also provide additional information: > - What is your evaluation of the library's: > * Design I am very much impressed by the design of Hana and the cleverness of the usage of C++ 14 lambdas. > * Implementation As far as I can judge it is very well implemented. > * Documentation I think writing "using namespace boost::hana" for the documentation is confusion. I know it might be nit-picking, but I think the example is easier to understand when you read struct Fish { std::string name; }; struct Cat { std::string name; }; struct Dog { std::string name; }; auto animals = boost::hana::make_tuple(Fish{"Nemo"}, Cat{"Garfield"}, Dog{"Snoopy"}); instead of struct Fish { std::string name; }; struct Cat { std::string name; }; struct Dog { std::string name; }; auto animals = make_tuple(Fish{"Nemo"}, Cat{"Garfield"}, Dog{"Snoopy"}); Because if you read diagonally (and let's be realistic, we all read diagonally documentation) you might miss what is going on. At least some namespace alias would be helpful. I personally think redundancy is good in documentations. > * Tests There is a satisfactory number of tests and the developer does continuous integration. The developer tests on several compiler versions at every change which is a must for a MPL. > * Usefulness Boost.Hana is extremely useful, especially the compile-time introspection it adds. It uses macros but as long as the language doesn't provide features to do compile-time introspection, there is no way around this (that I can think of) It has a lot of algorithms out of the box (at least I couldn't find one I would need that was missing). I like the compile-time arithmetic part of the library and find it very convenient. I'm a big fan of Boost.Fusion and I use Boost.MPL a lot. Hana replaces both libraries and compiles faster at the cost of requiring recent compilers. It is, to me, a very acceptable tradeoff. > - Did you attempt to use the library? If so: > * Which compiler(s) Clang 3.5 on FreeBSD 10.1 and libc++ > * What was the experience? Any problems? The only problem I have with Hana is that it doesn't work with Visual Studio. The lack of VS is the only reason why we didn't adopt Hana on our product. Nevertheless, I don't think it a showstopper. Hana is an advanced MPL and the problem will solve by itself with time. It works, in my opinion, on a sufficient number on platforms at the moment to be accepted into Boost. > - How much effort did you put into your evaluation of the review? I ran by the examples again as I would if I were trying the library for the first time. I have been following Boost.Hana since Louis' presentation at last year cppcon in Bellevue, Wa. Kind regards. --Edouard

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different Problem cross-compiling against boost.context for Raspberry Pi (2)
by Biddiscombe, John A. 16 Jun '15

16 Jun '15

When compiling HPX against the now built boost, I have this error message /home/biddisco/apps/boost-1_58_0/include/boost-1_58/boost/context/execution_context.hpp:202:52: error: âstd::index_sequenceâ has not been declared std::index_sequence< I ... >) { index_sequence appears to be c++14, I'm using -std=c++11, can one tell if this likely a mistake on my part somewhere, or a possible problem with boost.context? (Is there a BOOST_FLAG_SOMETHING, I should add to prevent t being used?) thanks JB

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[Advice] Documenting the "refined by" relation for concepts
by Louis Dionne 15 Jun '15

15 Jun '15

Dear all, When documenting a concept in a generic library, it is common to include what this concept is a "refinement of", i.e. which other concept(s) it specializes. For example, see the ForwardContainer concept from the SGI STL [1], which is a refinement of the Container concept. I find documenting this relation very useful. However, I have never seen the reverse relation of being "refined by" documented. It has been suggested to me [2] that Hana should document this "refined by" relation. Having never seen it done before, I'd like to know what the seasoned generic library writers think about it. The possibilities I personally see are 1. It's just not useful, and that's why it's not done 2. It's actually harmful, because you can't predict who is going to refine a concept 3. There's no "logical" reason behind this, it just happened to work that way in the SGI STL and everybody else followed that lead. Any input is appreciated. Regards, Louis [1]: https://www.sgi.com/tech/stl/ForwardContainer.html [2]: https://github.com/ldionne/hana/issues/104

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Genetics library - advice needed.
by Andy Thomason 15 Jun '15

15 Jun '15

Hi All, I am getting close to rolling out the first draft of our genetics library. https://github.com/andy-thomason/Boost.Genetics This library allows you to search gene sequences - most commonly the human genome - (eg. ENSEMBL .fa files) for inexact matches. At present the library emphasises thoroughness over performance but the latter will improve. The algorithms are all single-threaded at present as the user should provide the thread control. Feedback would be useful. I appreciate that this is still a little way from being a final submission, in particular we need: * documentation * more examples (currently only a python binding example) * more tests I'll be setting these as a task for my students. Don't expect it to build and run out of the box except for the unit tests and they might not wor in 32 bit builds. I'd also apreciate help with the build system as getting a build on 64 bit windows is a challenge for Boost.Python at present and some wisdom would go far. Are there plans for VC2013/15 solution generation from BJAM? That would be useful. Is there a continuous integration system we could use to pre-check the library? Andy. --- This email is free from viruses and malware because avast! Antivirus protection is active. https://www.avast.com/antivirus

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[Graphs] Bug in directed edge-connectivity algorithm
by Michele Borassi 15 Jun '15

15 Jun '15

Dear all, my name is Michele Borassi, and I am a user of Boost Graph library, version 1.58.0. I have found a problem in the edge connectivity algorithm: if the input is a directed path with 3 vertices (0, 1, 2) and 2 edges ((0,1), (1,2)), the output is 1 (while it should be 0, since the graph is not strongly connected). However, if edge (1,0) is added, the output becomes (correctly) 0. A minimal working example that shows this issue is attached; my output is: Path of 3 vertices and 2 edges. The edge connectivity is 1. Added edge (1,0): now there are 3 edges. The edge connectivity becomes 0. Could you also explain me which is the best way to report a bug? I have checked your web page http://www.boost.org/development/bugs.html, but all links seem to be broken. Waiting for your answer, I thank you in advance, Michele Borassi

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[Better Enums] More complete release - feedback requested
by Anton Bachin 15 Jun '15

15 Jun '15

Hello, I posted to the mailing list some weeks ago concerning a reflective enum library. I’ve since done a lot of work and made a new release. I’d like to get feedback from anyone that is interested. The library can be found at: https://github.com/aantron/better-enums At the risk of repeating myself, let me summarize for those who didn’t read the original thread: the library generates reflective enums that support string conversion and iteration, but with a nicer syntax than seen to date. Also, in C++11, the reflective capabilities are accessible at compile time. Since the original thread, I have made the library work with C++98 with the variadic macro extension, tested it thoroughly on clang, gcc, and msvc, rewrote the documentation, and made the interface (potentially) completely constexpr. The reason I say potentially is that there is one slow feature, which is disabled by default, but can be opted into easily. There is a tutorial starting here: http://aantron.github.io/better-enums/tutorial/HelloWorld.html and a few examples of “advanced” usage, the most interesting one of which I think is: http://aantron.github.io/better-enums/demo/SpecialValues.html (Thanks to Gottlob Frege for making a suggestion, which I adapted to improve this example.) I’d like to take this as far as possible towards solving the problems with C++ enum maintainability, and providing improved enum types that are as near to first-class as possible. I would be very happy if you just tried this out and let me know what you think and what problems you ran into. Thank you, Anton

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a thread pool that allows recursive calls
by Frédéric Bron 13 Jun '15

13 Jun '15

Dear boosters, I need to perform some tasks in parallel and want to control the number of CPUs that are used. A threadpool seems to be what I want and http://threadpool.sourceforge.net/ looks good. However, my tasks may also want to launch some parallel sub-tasks and the sub-tasks may also want to launch tome parallel sub-sub-tasks... and this is not possible with this implementation of threadpool. I have programmed something that works and I wonder if anyone had also already done that because my implementation is very rudimental for now and if something already exists I do not want to reinvent the wheel. Having said that, if there is nothing publicly available (I mean open-source), do you think it would be valuable I share what I did and make it available to boost as a library? This would require some advices/reviews from thread experts and a lot of work from me but I would be happy to contribute. Kind regards, Frédéric

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Heterogeneous Container Library (HCL) Feedback and Testing
by James Armstrong 13 Jun '15

13 Jun '15

I send out a little feeler about a month ago for interest in a container library which natively allows users to insert a heterogeneous set of types. After getting some really good feedback, I think I have settled into something that is efficient, has a nice clean interface, and provides some useful capabilities. I am hoping people can take a look at the code, test it out, and provide an additional feedback in terms of interface, implementation, bugs, or additional features/classes that would be useful. I have implemented a set of containers which mimic the capabilities of the STL containers. These are (so far) * heterovector * heterostack * heteroqueue * heterolist * heteroforward_list * heterodeque These containers were implemented using variadic templates and were somewhat inspired from the posts of Joaquín Muñoz. http://bannalia.blogspot.com/2014/05/fast-polymorphic-collections.html http://bannalia.blogspot.com/2014/05/fast-polymorphic-collections-with.html In addition, I have an adaptor class which provides a simple interface for accessing data of a specific type from a container of type_erased objects (boost::any, boost::variant, etc). The code is hosted at https://github.com/armstrhu/HCL and the directory structure there should be simple to navigate. There is an include directory which contains the header files needed, and an examples directory which provides examples for using the containers and the adaptors. As they mimic the STL containers, once you see how to use them (basically just provide an additional template parameter) you should be able to use them smoothly. One note is I focused mainly on developing the heterovector class, and the remainders are primarily copies of that class where std::vector has been replaced with std::deque, std::list, etc, and associated methods added/removed as needed. I have primarily tested with the heterovector, so having people check out the other classes would be nice :) Any and all feedback is much appreciated. Thanks! -- James Armstrong

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[Geometry] Wrong results for dissolve Polygon
by Andreas Wimmer 12 Jun '15

12 Jun '15

Dear Boost Geometry Contributors, I am testing the boost::geometry::dissolve function upon some invalid polygons that are produced by a certain in-house segmentation alg. The fact that the algorithm is producing possibly invalid polygons cannot be changed easily so I thought I will fix them afterwards using dissolve from “geometry/extensions/algorithms/dissolve.hpp” for the latest boost 1.58 version. Unfortunately I stumbled over the following polygons for which dissolve produces wrong results. The following code illustrates the result using namespace boost::geometry; using namespace boost::geometry::model; using namespace boost::geometry::model::d2; int main(int argc, _TCHAR* argv[]) { polygon< point_xy<float> > Poly; read_wkt("POLYGON((10 10, 10 20, 20 20, 15 12, 15 18, 20 10, 10 10))", Poly); multi_polygon< polygon< point_xy< float > > > Dissolved; boost::geometry::dissolve(Poly, Dissolved); } Which results in a polygon including the small intersection part which should be excluded from the polygon And even more problematic the following example (same polygon with and additional self-touching outer ring) results in missing the entire main part of the polygon int main(int argc, _TCHAR* argv[]) { polygon< point_xy<float> > Poly; read_wkt("POLYGON((10 10, 10 20, 20 20, 20 25, 22 25, 20 20, 15 12, 15 18, 20 10, 10 10))", Poly); multi_polygon< polygon< point_xy< float > > > Dissolved; boost::geometry::dissolve(Poly, Dissolved); } I hope somebody can show me what I did wrong or what I can to too work around this problem. Best regards, Andreas Wimmer

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Appveyor
by Mathieu Champlon 12 Jun '15

12 Jun '15

Hello, I've seen it mentioned a few times on the mailing list. Can anyone point me to a boost library (or a library which makes use of boost) which builds on appveyor ? A find for appveyor.xml in the boost/libs directory does not yield anything and I couldn't find a way to search for projects on appveyor itself... Thank you ! MAT.

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