March 2021 - Boost - lists.boost.org

Confusion regarding projects
by Ameya Chawla 17 Mar '21

17 Mar '21

Respected sir/madam I want to contribute to Boost C++ libraries , but i am confused that do I have to contribute to all the 3 projects mentioned in Boost.uBlas <https://github.com/boostorg/ublas>: Matrix and Tensor Computations or I can contribute to any one of them .and competency test is for project 2 only or for all 3 projects ? https://github.com/CGAL/cgal/wiki/Project-Ideas Thank you

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Confusion regarding projects
by Ameya Chawla 17 Mar '21

17 Mar '21

Respected sir/madam I want to contribute to Boost C++ libraries , but i am confused that do I have to contribute to all the 3 projects mentioned or I can contribute to any one of them .and competency test is for project 2 only or for all 3 projects ? https://github.com/CGAL/cgal/wiki/Project-Ideas Thank you

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[release] Boost 1.76.0 beta 1 released
by Marshall Clow 16 Mar '21

16 Mar '21

Boost release 1.76.0 beta 1 is now available at: <https://dl.bintray.com/boostorg/beta/1.76.0.beta1/source/> The SHA256 checksums are as follows: 39eecd9672e78b95c8e3fdec1430a63788d528a66d3c8799c4639238e5d785bd boost_1_76_0_b1.7z c32edd34f767dd4bb67b86f76ebf58cf76822a5993a9b434c028b2dd08cfeefc boost_1_76_0_b1.zip 3ec1f92fa0a159b7073e39dd88f527a55d1f35e8986a3c560f202a75bdb8d584 boost_1_76_0_b1.tar.gz eb098d6d5352e10b17a3c49d2927ed61f09b6544f7c534627de35dfa2560fe20 boost_1_76_0_b1.tar.bz2 For details of what's in the release, see <https://www.boost.org/users/history/version_1_76_0.html>. Please download the beta, give it a try, and report any problems you encounter. Thanks, -- The Boost Release Team

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Introduction-Tushar Khandelwal
by Tushar k 16 Mar '21

16 Mar '21

Hi, I am Tushar Khandelwal from BITS Pilani 2019 Batch, I have a decent understanding of C++, I have been practicing C++ for the past 2 years, I am proficient in data structures and algorithms, I am new to open source and would love to contribute to this organization. How should I get started?

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Headers only or .o
by Damian Vicino 15 Mar '21

15 Mar '21

Hi, I was reading the development section of the docs: https://www.boost.org/development/index.html And, I noticed there was nothing in the development guidelines about when to implement as headers-only vs built library. I got my own ideas of why most libraries are headers-only. But, I was wondering if someone with the historical context (someone who was here when those first libraries were developed) can share how boost got into the current shape and what new library developers should look into when deciding to go headers-only or not. I appreciate any anecdotes, guidelines, tradeoffs, thumb rules, comments on the topic. I would love to collect as much as possible here in this thread and write something to post in the development doc section in the website for future reference. Best, Damian

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[Describe] Review - Part 2: Class types
by Andrzej Krzemienski 15 Mar '21

15 Mar '21

Hi Everyone, Some feedback from playing with Boost.Describe for class types. 1. As others pointed out, it is confusing that BOOST_DESCRIBE_STRUCT() and BOOST_DESCRIBE_CLASS() have such close names, but their interface and requirements are so different. Maybe rename the latter to BOOST_DESCRIBE_THIS_CLASS()? 2. Base class subobjects are in some applications treated equivalently to member subobject; this is why I found it surprising that I cannot get the names of base class subobjects. But I guess there are implementation difficulties. Bases can be qualified names. 3. As with enums, _public_member_descriptor_fn in global namespace is UB or invalid program as per http://eel.is/c++draft/lex.name#3.2. 4. As others pointed out, the part of the interface that uses enum modifiers is not intuitive. I think that after a while it starts to make sense: you decide on your use case (like doing RPC), form your enum bitmask, and then pass it everywhere. It became more-less clear to me only after I had a look at the implementation of member_filter: https://github.com/pdimov/describe/blob/develop/include/boost/describe/memb… Maybe it makes sense to expose this in the docs. 5. Modifier mod_inherited is great for flattening the inheritance structure: struct X { int a; }; struct Y : X { int b; }; struct Z : Y { int c; }; BOOST_DESCRIBE_STRUCT(X, (), (a)); BOOST_DESCRIBE_STRUCT(Y, (X), (b)); BOOST_DESCRIBE_STRUCT(Z, (Y), (c)); int main() { namespace desc = boost::describe; using namespace std::literals::string_literals; constexpr auto mod = static_cast<desc::modifiers>(desc::mod_public | desc::mod_inherited); using L = desc::describe_members<Z, mod>; assert((boost::mp11::mp_at_c<L, 0>::name == "a"s)); assert((boost::mp11::mp_at_c<L, 1>::name == "b"s)); assert((boost::mp11::mp_at_c<L, 2>::name == "c"s)); } But it is not obvious at first. I recommend that the docs provide an example like this. It even works when base classes have members with same names: struct X { int a; }; struct Y { int a; }; struct Z : X, Y { int b; }; BOOST_DESCRIBE_STRUCT(X, (), (a)); BOOST_DESCRIBE_STRUCT(Y, (), (a)); BOOST_DESCRIBE_STRUCT(Z, (X, Y), (b)); int main() { constexpr auto mod = static_cast<describe::modifiers>(describe::mod_public | describe::mod_inherited); using L = describe::describe_members<Z, mod>; Z z = {{{3}}, {{6}}, {9}}; assert((z.*mp_at_c<L, 0>::pointer == 3)); assert((z.*mp_at_c<L, 1>::pointer == 6)); assert((z.*mp_at_c<L, 2>::pointer == 9)); } 5. What is the use case for modifier mod_hidden? I cannot think of any situation where I would need it. 6. Regarding the overloaded functions, I am no expert in preprocessor metaprogramming, but maybe if there was a way to provide function signatures along the name, you would have enough information to form the pointers. Something like: struct X { void f(int){} void f(void*){} }; BOOST_DESCRIBE_STRUCT(X, (), ( SIGNATURE(void f(int)), SIGNATURE(void f(void*)) ); 7. Modifier mod_virtual works unintuitively. It does not affect the filtering in describe_bases<>. It is only used for decorating the list elements. Maybe the docs should be more explicit about what it is used for. Again, is there a use case for this? Regards, &rzej;

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GSoC'21 boostorg timeline
by Krushnal Patel 15 Mar '21

15 Mar '21

Hi, I wanted to inquire about the GSoC'21 timeline specific to boostorg. I have gone over the GSoC'21 timeline but are there any specifics decided by boost regarding project selection, pre-proposal submission, proposal overview, programming competency test submission, etc? I am asking this question because as I was going over last years' mailing list I found a post where 'pre-proposal submission' was discussed so I started researching more about any timeline released specifically by boost but did not find any. Thanks in advance. Krushnal Patel, http://krushnal.me/

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Requirement of mentorship for Generic Image Library project
by Aditya Tiwari 15 Mar '21

15 Mar '21

Hello there, I am Aditya Tiwari, a GSoC aspirant. I am interested in contributing to the Boost C++ library on the project "*Generic Image Library*". The knowledge requirement for this project is C++ and understanding of basic image processing algorithms, and I have a good knowledge of these two. I have been coding in C++ for over two years, with prior experience working with Boost libraries and working on projects related to image processing for over 1 year. I have read the problem statement and under GIL there's a project 2 about implementing image processing algorithms and in that list I know quite a bunch of algorithms. Also the project 1 under GIL, is quite a confusing task for me like do we have to add more and efficient algorithms here or something else? It would be very helpful if you can guide me through this project. I am open to any suggestions and I shall proceed with the task upon your acknowledgement. Regards, Aditya

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Re: [boost] [release] Boost 1.76.0 Beta 1 Release Candidate 1: fixed std::allocator deprecation-warning
by Löw, Tobias (STEAG Energy Services GmbH) 15 Mar '21

15 Mar '21

Hi, I've made a fix for the deprecation-warning: boost\unordered\detail\implementation.hpp(1452,7): warning C4996: 'std::allocator<T>::is_always_equal': warning STL4010: Various members of std::allocator are deprecated in C++17. Use std::allocator_traits instead of accessing these members directly. You can define _SILENCE_CXX17_OLD_ALLOCATOR_MEMBERS_DEPRECATION_WARNING or _SILENCE_ALL_CXX17_DEPRECATION_WARNINGS to acknowledge that you have received this warning. The PR is here: https://github.com/boostorg/unordered/pull/21 Tobias

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[release] Boost 1.76.0 Beta 1 Release Candidate 2
by Marshall Clow 13 Mar '21

13 Mar '21

The second release candidates for the 1.76.0 beta release are now available at: <https://dl.bintray.com/boostorg/beta/1.76.0.beta1/source/> The SHA256 checksums are as follows: c32edd34f767dd4bb67b86f76ebf58cf76822a5993a9b434c028b2dd08cfeefc boost_1_76_0_b1_rc2.zip eb098d6d5352e10b17a3c49d2927ed61f09b6544f7c534627de35dfa2560fe20 boost_1_76_0_b1_rc2.tar.bz2 39eecd9672e78b95c8e3fdec1430a63788d528a66d3c8799c4639238e5d785bd boost_1_76_0_b1_rc2.7z 3ec1f92fa0a159b7073e39dd88f527a55d1f35e8986a3c560f202a75bdb8d584 boost_1_76_0_b1_rc2.tar.gz The only changes from RC1 is an update to Boost.Interprocess, which was failing to compile on Mac OS X. As always, the release managers would appreciate it if you download the candidate of your choice and give building it a try. Please report both success and failure, and anything else that is noteworthy. -- The Release managers

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