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Fit review - viboes
by Vicente J. Botet Escriba 10 Sep '17

10 Sep '17

Hi, here it is my review. I believe that Boost.Fit should be*accepted*. *Design* The design is sound and clean. I have some concerns respect the the ConstFunctionObjects that I believe should merit an explanation on a rationale section. Why the library support only Const function objects? Wondering if some parts should be moved to Boost.TypeTraits or reused from there (is_callable). I'm missing the std::invoke function. The_adaptor<> are not documented. The utility of those classes is not documented. If the user can use those classes the documentaion must document them. I guess they are useful to build other adaptors. It is not clear whether the defined functions would use SFINAE or just fail when used with types that don't respect the requirements. While I'm generally for SFINAE, I understand that it will not be the case in order to improve the compile time. It is not clear if the functions can be final function objects or not. *Implementation* Not seen in depth. It should use as much as possible Boost.Config and/or Boost.Predef Possible files contains details that could be shared in Boost or used from other Boost libraries https://github.com/pfultz2/Fit/blob/boost/include/boost/fit/detail/move.hpp - I believe Hana use something like this also to reduce the dependencies (compile footprint) https://github.com/pfultz2/Fit/blob/boost/include/boost/fit/detail/forward.… https://github.com/pfultz2/Fit/blob/boost/include/boost/fit/detail/noexcept… https://github.com/pfultz2/Fit/blob/boost/include/boost/fit/detail/and.hpp - I believe Hana use something like this also to reduce the dependencies (compile footprint) https://github.com/pfultz2/Fit/blob/boost/include/boost/fit/detail/compress… https://github.com/pfultz2/Fit/blob/boost/include/boost/fit/detail/constexp… https://github.com/pfultz2/Fit/blob/boost/include/boost/fit/detail/intrinsi… https://github.com/pfultz2/Fit/blob/boost/include/boost/fit/detail/pp.hpp https://github.com/pfultz2/Fit/blob/boost/include/boost/fit/detail/remove_r… https://github.com/pfultz2/Fit/blob/boost/include/boost/fit/detail/result_o… https://github.com/pfultz2/Fit/blob/boost/include/boost/fit/detail/static_c… https://github.com/pfultz2/Fit/blob/boost/include/boost/fit/detail/using.hpp It uses a lot of macros that make complex the understanding of what is behind. On the same file https://github.com/pfultz2/Fit/blob/boost/include/boost/fit/compose.hpp and only on 169 lines BOOST_FIT_INHERIT_CONSTRUCTOR, BOOST_FIT_RETURNS_CLASS, BOOST_FIT_SFINAE_RESULT, BOOST_FIT_MANGLE_CAST, BOOST_FIT_DECLARE_STATIC_VAR, BOOST_FIT_NOEXCEPT_CONSTRUCTIBLE, BOOST_FIT_ENABLE_IF_CONSTRUCTIBLE, BOOST_FIT_JOIN *Documentation* Quite good butthe description of the semantic of the provided functions would need some extra wording. Maybe a section that states that the semantic expression is part of the constraints on the types. It takes too much pages to see what the library proposes. For some functions we would need more information, examples. See below the detailed *Potential usefulness of the library* Very useful. *Did you try to use the library? With which compiler(s)? Did you have any problems?*** Not tried yet. *How much effort did you put into your evaluation? A glance? A quick reading? In-depth study?*** In-depth study of the documentation (about 5 h for this revision). *Are you knowledgeable about the problem domain?* In general, yes. *Were the concerns from the March 2016 review of Fit addressed?*** I believe ;-) Best, Vicente *Documentation:* In general: * Navigation only from the top of the page * Hyper links missing. * There is no link to real code from the examples. In particular: *http://pfultz2.github.io/Fit/doc/html/doc/src/gettingstarted.html* An explanation of the BOOST_FIT_LIFT limitations would be more than welcome. Typo: last right parenthesis in // Pipable sum BOOST_FIT_STATIC_LAMBDA_FUNCTION(sum) = pipable([](auto x, auto y) { return x + y; }); It is not clear if the following is correct in the body of a function autosum = pipable([](auto x, auto y) { return x + y; }; *http://pfultz2.github.io/Fit/doc/html/doc/src/example_print.html* I would suggest to use an heterogeneous tuple in the for_each_tupleexample. In addition use some kind of brackets to print the sequences and the tuples would help to identify what is been printed. *http://pfultz2.github.io/Fit/doc/html/doc/src/example_overloading.html* Typo: Before // Check that T has member function for operator* and ope After // Check that T has member function for operator* and opeerator-> I'm not sure the example is_derreferenceable is fair. *http://pfultz2.github.io/Fit/doc/html/doc/src/example_polymorphic_constructors.html* Maybe it is worth adding references to the proposals (P0318R0 and P0338R2) *http://pfultz2.github.io/Fit/doc/html/doc/src/more_examples.html* Extension Methods It is not clear what numbers, filter and transform are in the example. I believe that the range proposal woul include the pipe operator. My question is how both pipe operator overloads interact. http://pfultz2.github.io/Fit/doc/html/doc/src/point_free.html typo Before |b(f)(x, y)| |after| ||by(f)(x, y)|| *http://pfultz2.github.io/Fit/doc/html/doc/src/definitions.html* It woul dbe great to have an example associated to each definition Static Function Adaptor I would say "It has an additional requirement that the *class****function* is |DefaultConstructible|:" Decorator I would say "The *resulting* Function Adaptor <http://pfultz2.github.io/Fit/doc/html/doc/src/definitions.html#function-ada…> may be an unspecified or private type." Typo? Some parts of the documentation provides *http://pfultz2.github.io/Fit/doc/html/doc/src/concepts.html* ConstFunctionObject I would like to note that this concept is not representable using the Concept TS as it is quantifying universally on the Ts (args) parameters. The same applies to UnaryFunctionObject, BinaryFunctionObject Wondering if the documentation should use the term Concepts then. The use of expresion "Is an object with ..." is confusing. What are we qualifying the type or the instance? Maybe it is worth defining FunctionObject. EvaluatableFunctionObject It is not clear why this kind of FunctionObjects is useful Callable I believe we have moved to call this Invocable in the standard. But again, I believe that you want to quantify universally the arguments, isn't it? Does your definition of INVOKE differs from the one on the standard? If yes, the differences should be mentioned. If not, the definition on the standard should be referenced. You use type T twice with different meaning "The type |T| satisfies |Callable| if" "if |f| is a pointer to member function of class |T|:" I believe that here the T are not the same. Are final function objects Callable, ConstCallable? ConstCallable The brief description is the same as the one for Callable Is the definition of the second INVOKE different from the first one? UnaryCallable The name doesn't convey that it is *Const*Callable Metafunction and MetafunctionClass it is not clear what those are, there is no brief description. I guess that this applies to f. What do you mean by a type or a template? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/by.html* It is not clear to me what by(p)(xs...) == p(xs)... mean An example of `fit::by` without a function argument will be welcome. It is not clear how by_adaptor<Projection, F> and by_adaptor<Projection> can be used by the user? Shouldn't those be hidden? This is a genral remak, why F must be ConstCallable? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/compose.html *The requirements don't state clearly the constraints on the input parameters of f and the result of g, except by the semantic expression. This is a general remark. I suspect that you mean the semantic expression must be well formed. But, is this SFINAE friendly or is this a requirement? Can both function be final function objects? **** *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/conditional.html* It is not clear what king of parameters this function could have (in particular in comparison with P0051). Does it accept function/data members pointers, final classes, references_wrappers, ...? Typo "Proposal for C++ Proposal for" P0051 original proposal uses overload_linearly/overload (as Boost.Hana) instead of conditional/match. Wondering if those names aren't more clear. Why do we need to change the Boost.Hana names? There is also std::conditional :( Can more than 2 parameters be final function objects? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/flip.html** * IIUC, F must not be BinaryCallable, but Callable with at least two arguments. *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/implicit.html* Is implicit a StaticFunctionAdaptor? Shouldn't StaticFunctionAdaptors have Functions as parameters? I named the `auto_cast` function `explicitly` to do a explicit conversion. Other uses of this pattern I've see are to create a buffer able to store a specific struct struct S; S* ptr = create_msg(); create_msg returns an class that is convertible to a T* and that allocates sizeof(T) bytes of memory. Why this pattern respect the DRY principle (we don't repeat S), I believe it abuses of implicit conversions. Anyway, I wanted just to share another use case for implicit. http://pfultz2.github.io/Fit/doc/html/include/boost/fit/indirect.html Wondering if it could be worth adding some preconditions as I guess that the function call indirect(f)(xs...) will be undefined if f is null *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/infix.html** * One of the asked infix operations is pow. However we would like to evaluate from right to left and have the higher precedence than * x pow ypow z===pow(x, pow(y,z)) x * ypow z===x * pow(y,z) x pow y* z===pow(x,y) * zWith the proposed infix notation this should be written x <pow> (y<pow> z)===x * pow(y,z) x * (y<pow> z)===x * pow(y,z) (x <pow> y)* z===pow(x,y) * z and the following would be surprising x <pow> y<pow> z===pow(pow(x, y, z) x * y<pow> z===pow(x * y, z) x <pow> y*z===pow(x, y * z) It would work better for swap or compare (proposed operator <=>) as these functions are not associative. I believe a note should prevent the users for such bad use cases, for which it is better to don't define the infix operator. *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/lazy.html* Note p0356r1. It would be good to have a comparison in order either to improve the proposal or your library. *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/match.html* Same comments than for fit::conditional. What are ex typo "Proposal for C++ Proposal for" Can more than 2 parameters be final function objects? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/mutable.html *Example of bad usage would be welcome.**Why Fit uses always const? **Why not use a reference to the function object instead? Is there a safe way to use MutableFunctionObjects with Fit? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/partial.html* Are there any constraints on the type of xs. Shouldn't them be MoveConstructibles? http://pfultz2.github.io/Fit/doc/html/include/boost/fit/pipable.html Are there any constraints on the type of x. Shouldn't it be MoveConstructible? http://pfultz2.github.io/Fit/doc/html/include/boost/fit/protect.html It is not clear to me what this useful for. Could you elaborate? Is there a typo here assert(lazy(f)(protect(lazy(g)(_1)))() == f(lazy(g)(_1))) ^ Shouldn't it be assert(lazy(f)(protect(lazy(g)),_1)() == f(lazy(g)(_1))) *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/result.html*** This adaptor converts explicitly the result of the call to the type. Have you considered `convert_to`? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/reveal.html* as_failures, with_failures, .... /adaptors/ don't appear on the index. *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/reverse_fold.html* reverse_fold is not right fold, as right fold is right associative, isn't it? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/rotate.html*** Could you show a concrete use case? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/static.html*** What are the differences of this adaptor and the macro STATIC_FUNCTION? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/unpack.html* Why name it unpack instead of apply like in C++17? Need to introduce the Sequence concept and how it is customized? unpack_sequence? How unpack_sequence is used by unpack? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/unpack_sequence.html*** Why unpack_sequence, and not the tuple-like traits? Is unpack_sequence defined if the class defines the tuple-like traits? Aside the example, it is not defined what the user must define. What the member function apply must return? How the unpack_sequence parameter and the Sequence parameter of member function apply are related? I don't understand template<class F, class Sequence> constexpr static auto apply(F&& f, Sequence&& s) BOOST_FIT_RETURNS ( s(std::forward<F>(f)) ); Is a Sequence a callable taking a Callable or there is a type here? Is there a missing return? I suspect it should be template<class F, class Sequence> constexpr static auto apply(F&& f, Sequence&& s) BOOST_FIT_RETURNS ( std::forward<F>(f)(s0, ,, sk); ); If this is correct, does it means that unpack just forwards to unpack_sequence? Does the default specialization make use of INVOKE? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/capture.html*** Please, could you show how it is more flexible than lambda captures in C++? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/if.html* What happens when the parameter is false_type? SFINAE? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/limit.html*** if a function object is overloaded with 2 and 3 parameters, would limit be useful or it is only useful when the number of parameters is fixed? I believe this is answered in http://pfultz2.github.io/Fit/doc/html/doc/src/partialfunctions.html, however I believe it merits a clarification here. *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/repeat.html* Add requirement on the function parameter that must be a Unary function such that f(f(x)) is well formed. *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/repeat_while.html* The same here. *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/arg.html*** What is the rational for the choice of been 1-based? Could you add a rationale in the doc? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/construct.html* Maybe add a reference to the factory proposal p03382. What happens when the parameter is not a T is not constructible from the params? SFINAE? What happens when the parameter is not a MetafunctionClass? SFINAE? I believe Boost.Hana uses make instead of construct. *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/decay.html* Why not decay_copy? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/identity.html *is identity a function or a function object? do we need identity()(x)? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/placeholders.html*** Wondering if it is not better to locate them in a placeholders namespace, so that we can avoid possible collisions with other placeholders. *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/placeholders.html#unamed-placeholder* The same here *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/function_param_limit.html*** |function_param_limit is not a Metafunction. "|The|function_param_limit| metafunction ..." *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/is_callable.html*** F must be Callable can not be a requirement ;-) Add reference to C++17 trait is_invocable. Wondering if we should have it in type_traits, if not already there. *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/apply.html*** Confusion with std::apply. is this related to std::invoke? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/function.html* "By default, all functions defined with|BOOST_FIT_STATIC_FUNCTION| use thereveal <http://pfultz2.github.io/Fit/doc/html/include/boost/fit/reveal.html> adaptor to improve error messages." How to change this default? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/lift.html*** WhyBOOST_FIT_LIFT_CLASSdoesn't defines a instance as do BOOST_FIT_STATIC_FUNCTION? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/pack.html*** How this is related with fit::capture? *http://pfultz2.github.io/Fit/doc/html/include/boost/fit/tap.html* How this is related to the tee unix command? *http://pfultz2.github.io/Fit/doc/html/doc/src/configurations.html***Which ones?

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How to deal with unused variable with a BOOST_ASSERT check?
by James E. King, III 10 Sep '17

10 Sep '17

In serialization (boost/archive/iterators/mb_from_wchar.hpp) there is some code that generates a warning on release builds. We're always striving for warning-free code in all cases. Here's the snippet: std::codecvt_base::result r = m_codecvt_facet.out( m_mbs, & value, & value + 1, wend, m_buffer, m_buffer + sizeof(m_buffer), bend ); BOOST_ASSERT(std::codecvt_base::ok == r); Normally I'd say one should always check the result and throw an exception instead of relying on an assert. I'm sure consumers would like that more. That said, is there another macro that would allow me to change the code to do something like this? BOOST_ASSERT_ASSIGN_OR_IGNORE(std::codecvt_base::result r) m_codecvt_facet.out( m_mbs, & value, & value + 1, wend, m_buffer, m_buffer + sizeof(m_buffer), bend ); BOOST_ASSERT(std::codecvt_base::ok == r); where BOOST_ASSERT_ASSIGN_OR_IGNORE would expand to, assuming BOOST_ASSERT_ACTIVE is an indicator whether assert code is compiled in: #if BOOST_ASSERT_ACTIVE std::codecvt_base::result r = #else (void) #endif This would allow me to eliminate the warning without submitting a PR that changes the behavior of the code. If something like this does not exist, would it be useful for me to add it to boostorg/assert, or would folks recommend against encouraging this behavior and instead change it to use exceptions? Thanks, Jim

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range/concepts.hpp broken on master
by Peter Dimov 09 Sep '17

09 Sep '17

Trying to, f.ex., build quickbook on master fails with an error like ./boost/range/concepts.hpp: In destructor 'boost::range_detail::SinglePassIteratorConcept<Iterator>::~SinglePassIteratorConcept()': ./boost/range/concepts.hpp:167:55: error: 'iterator_traits' in namespace 'boost::detail' does not name a type That's because boost/iterator/iterator_concepts.hpp used to include boost/detail/iterator.hpp, and no longer does since this commit: https://github.com/boostorg/iterator/commit/0107df44ab3ab41c46b616c9c37c30f… This apparently works on develop, which means that it's probably fixed in Range's develop branch, but the changes aren't in master.

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[build] using nvcc as toolset target?
by Oliver Kowalke 09 Sep '17

09 Sep '17

Hello, a grep over the boost.config showed some code related to nvcc - but I could not figure out how to use nvcc together with b2. What is the toolset target for nvcc ('b2 toolset=nvcc' doesn't work)? Oliver

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Why is the boost documentation so bad?
by Florian Lindner 08 Sep '17

08 Sep '17

Hello, I really love to use boost libraries in my project, but I always wonder, for such an accomplished project, why is the documentation so bad? A few examples: I want to get familiar with http://www.boost.org/doc/libs/1_65_1/libs/ptr_container/. What do I need to include? Neiter the tutorial, the reference or the usage guidelines mention a #include line. This is something which stroke me quite often at various boost libs. Also with the ptr_container lib, I want to find the refrence for the ptr_vector::insert function. I got to scan the reference pages of all members of it's class hierarchy to find the insert() function (it's in ptr_sequence_adapter). References and example code often have no syntax highlightning and no linking and it's extremely hard to find documentation for a specific symbol, or from there, to jump to the source code. I would really like to have a more uniform and a documentation that not feels like a annotated source code dump. I use doxygen for my own projects and I know it can generate nicely looking, with syntax highlightning and linked documentation. Please, don't take this offensive, it's just some feedback I wanted to give a long time. Best, Florian

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[release] 1.66.0 open for merging
by Daniel James 08 Sep '17

08 Sep '17

The master branch is open for merging all stable changes from develop, including bug fixes and major upgrades to existing libraries. Breaking changes should be coordinated via the mailing list with the developers of the other libraries affected. New libraries may be added, but require permission of a release manager. In other words, merging does not require permission from a release manager, except for new libraries. Boost Calendar with the release schedule: http://www.boost.org/development/index.html Release schedule explanation: https://github.com/boostorg/boost/wiki/Release-Schedule Release practices for developers: http://svn.boost.org/trac/boost/wiki/ImprovingPractices -- The Boost Release Team

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Re: [boost] (no subject)
by degski 08 Sep '17

08 Sep '17

On 7 September 2017 at 17:37, Pranam Lashkari <plashkari628(a)gmail.com> wrote: > Hello, > > I recently joined boost community. I am an engineering student from India. > I don't have much experience with contributing in open source. > > Can you please help me getting started with it? > > From where I can/should start contributing this community..? > > Thank you. > Hi Pranam, You have to write to the boost mailing list: boost(a)lists.boost.org (and ask there) See also http://www.boost.org/community/groups.html for some "rules and regulations" and the need for "subscription". You can find the archives (old posts) here: https://lists.boost.org/ Archives/boost/ In the archive you'll see that your question has been asked (many times) before, answers where to start are also given in the follow-up to those questions. Personally, I would like to see Boost.Pool being brought up to the current C++ standard (C++17). That would be a nice little project. I believe Edward Diener is the current curator of that particular library. See you on the list and have a good day (and don't forget to subscribe), degski -- "*Ihre sogenannte Religion wirkt bloß wie ein Opiat reizend, betäubend, Schmerzen aus Schwäche stillend.*" - Novalis 1798

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[gsoc] Change in Google Summer of Code admin
by Niall Douglas 07 Sep '17

07 Sep '17

Dear all, Google Summer of Code 2017 has ended with another successful summer of student coding with probably the highest calibre year we've ever seen. After four years as lead admin for Boost Summer of Code, my time has come to an end. I'll be making way for David Bellot, long time mentor at Boost GSoC and maintainer of Boost.uBLAS. Please join me in welcoming David as new lead admin. I'll be staying on as backup admin next summer to help David settle in. My time as Boost Summer of Code admin has certainly been eventful with lots of surprises, ups and downs. The fact these surprises did not turn into crises is due in large part to a few people in particular who went far beyond the call of duty: * Jon Kalb, who went to bat for the students repeatedly in multiple venues and finding tens of thousands of dollars when it was needed. * Boris Schäling, whom I replaced as lead admin and who acted as backup admin for some years, who also managed to arrange tens of thousands of dollars of sponsorship when it was needed most. * Bryce Adelstein Lelbach, for acting as backup admin these past few years. * Andrew Sutton, the lead GSoC admin before Boris, who gave such detailed and useful early advice and materials on how to best navigate the treacherous waters of Google Summer of Code! And finally to all the mentors who so generously volunteered their time, and to the students every single one of whom successfully finished their projects in my time as admin despite problems with sickness, deaths in close family etc. Some of those students have gone on to become mainstays of the C++ conference circuit, famous names in their own right. I'm sure they would have been so without Google Summer of Code, but I'd like to think that it helped bring them to Boost rather than them getting into C++ via elsewhere. Thank you students! Regards, Niall

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master and develop branches
by James E. King, III 07 Sep '17

07 Sep '17

Could someone point me to documentation on management of the master and develop branches for committers? boostorg/uuid master ends at Jan 11. boostorg/develop has a bunch of stuff in it starting on August 3, 2017. Who is responsible for merging develop into master and when should that happen? Some of the issues are already marked resolved with a milestone of 1.66.0 but they are not in master, only develop. Should pull requests on github go directly into master? I find it confusing to have both and would prefer if there was only one possible destination for pull requests on github. If there are two, someone has to keep one of them updated and that isn't very efficient. Thanks, Jim

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Libraries maintained by CMT?
by James E. King, III 07 Sep '17

07 Sep '17

Hello, I was wondering if there's a page/location that lists the libraries currently being maintained by the community maintainer team? I recently assumed responsibility for maintaining boost::uuid and I was wondering if there was a list that needs to be modified. Thanks, - Jim

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