March 2025 - Boost - lists.boost.org

[release] Boost 1.88.0 Release Candidate 1 is available
by Marshall Clow 14 Mar '25

14 Mar '25

Available at: https://archives.boost.io/beta/1.88.0.beta1/source/ The SHA256 checksums are as follows: bc4948bc664fde0c2142badae2679a42124b464dc58019250afe0ef57fd7763e boost_1_88_0_b1_rc1.zip 3c334a9a743b68a35452b0223be8932fb39f26a6938382f9b9e625c4df99602c boost_1_88_0_b1_rc1.tar.gz 9e42c0611500151d795d66a07ef0a21036c02d24678e2e887caf6d97fcbc25ca boost_1_88_0_b1_rc1.tar.bz2 7faf60c4cb12ee90270e41716cf3735a8739016d7346983ce9f5e899e510b26d boost_1_88_0_b1_rc1.7z 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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[proposal] OpenMethod library
by Jean-Louis Leroy 11 Mar '25

11 Mar '25

Hello Boost developers! I would like to propose my open-method library for inclusion in Boost. Open-methods are an elegant solution to the Expression Problem: > Given a set of types, and a set of operations on these types, is it possible > to add new operations on the existing types, and new types to the existing > operations, without modifying existing code? Open-methods solve the Expression Problem by making it possible to define free virtual functions, i.e. virtual functions that exist outside of a class. They also help reduce coupling. Open-methods are often called "multi-methods", because they typically make it possible to select an overrider on the basis of more than one argument (as this library does). Nice, but this is a distraction. Observations show that single dispatch largely outnumbers multiple dispatch in real systems, even in languages that natively support multi-methods (Common Lisp, Clojure, Julia, Dylan, TADS, Cecil, Diesel, Nice, etc). "Multi" is just the cherry on the "open" cake. Bjarne Stroustrup wanted open-methods in C++ almost from the beginning. In D&E he writes: > I repeatedly considered a mechanism for a virtual function call based on more > than one object, often called multi-methods. [...] Since about 1985, I have > always felt some twinge of regret for not providing multi-methods. > Stroustrup, 1994, The Design and Evolution of C++, 13.8. Circa 2007, he tried to bring open-methods into the standard, unfortunately without success, to his enduring regret. Decades later he writes: > In retrospect, I don’t think that the object-oriented notation (e.g., x.f(y)) > should ever have been introduced. The traditional mathematical notation f(x,y) > is sufficient. As a side benefit, the mathematical notation would naturally > have given us multi-methods, thereby saving us from the visitor pattern > workaround. > Stroustrup, 2020, Thriving in a Crowded and Changing World: C++ 2006–2020. This is what this library is all about: f(x, y), and getting rid of visitors. It closely follows the design described in the papers by Stroustrup and his PhD students Peter Pirkelbauer and Yuriy Solodkyy. Method dispatch is *fast*. It uses v-tables similar to native virtual functions, and it can match their performance. The library also provides additional features: a mechanism to call the next most specialized overrider, support for smart pointers, customization points for alternative RTTI systems, error handling, tracing, etc. The library requires C++17 or above. It supports virtual and multiple inheritance, excluding repeated inheritance. For evaluation purposes, I prepared a repository with a library adapted to Boost naming conventions: https://github.com/jll63/Boost.OpenMethod. The documentation is here: https://jll63.github.io/Boost.OpenMethod. Here are a few examples from the tutorial on Compiler Explorer: * Hello World: https://godbolt.org/z/9hv8oE8zd * AST - combining virtual_ptr and std::unique_ptr: https://godbolt.org/z/cPjzfanc8 * Intrusive vptr: https://godbolt.org/z/87h9zv7dK * Policy for throwing exceptions: https://godbolt.org/z/nEYWGsPc5 If you like what you see, please consider endorsing the library. Thanks, Jean-Louis Leroy

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[Release] Master branch is now closed for the beta release
by Marshall Clow 09 Mar '25

09 Mar '25

Master is closed for all changes. See the release schedule at: https://www.boost.org/development/index.html -- Release managers

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[release] Master branch closes for the 1.88.0 beta release on SATURDAY (March 8)
by Ion Gaztañaga 06 Mar '25

06 Mar '25

Hi, Due to some unexpected delays, the master branch will close on SATURDAY (March 8). — The Release Managers

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