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boost.org domain expired?
by Warren Weckesser 03 May '22

03 May '22

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[Math / Distributions] How do mean, variance, etc end up in scope?
by Warren Weckesser 02 May '22

02 May '22

This is probably more of a C++ question than a Boost/Math question. I think the answer comes down to a (surprising?) Boost namespace convention. In a program like this: ``` #include <boost/math/distributions/beta.hpp> using boost::math::beta_distribution; int main() { float a = 1.5f; float b = 3.0f; beta_distribution<float> dist(a, b); auto m = mean(dist); } ``` how does the name 'mean' end up in scope in 'main()'? I would have expected (and preferred!) something like 'using boost::math::mean;' to be required. Warren

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[statechart] non-virtual unconsumed_event
by Alexandre Bouchu 26 Apr '22

26 Apr '22

Hello, Looking for guidance regarding best practices using boost statechart. When it came time to have a mechanism to catch unhandled events and pass that information back to clients, my first choice has been to override unconsumed_event public function in state_machine class. Given that the static code analysis tool we run complains about the dangers of overriding a non-virtual function, I came here to get more background into maybe why this function was not made virtual in the first place. Is there for example a better implementation practice that would see this "catch all" function stay empty, as is the case with state_machine implementation, and instead use another technique to provide meaningful feedback to clients when the action or state transition requested is invalid/unsupported? I feel I can justify and waive this code analysis tool warning up the food chain, but yet wanted some feedback from this user group first. Thanks, Alexandre

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constexpre limits
by Gero Peterhoff 21 Apr '22

21 Apr '22

Hello John, i switched std::numeric_limits<float128> completely to constexpr because it bothered me a lot. Especially: - quiet_NaN (removed sqrt) - has/signaling_NaN adjusted Hope that's ok. regards Gero

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Unable to run example code "line_interpolate"
by Ajay Kumar G 19 Apr '22

19 Apr '22

Hello, First of all, thank you for your contributions. Indeed it was a greatly useful library with very detailed documentation. While trying to run a sample example code "line_interpolate" from following link: https://www.boost.org/doc/libs/1_79_0/libs/geometry/doc/html/geometry/refer… There is an error that appears saying " error: ‘line_interpolate’ was not declared in this scope" but i dint understand the reason. While other examples from the reference( https://www.boost.org/doc/libs/1_79_0/libs/geometry/doc/html/geometry/matri…) work fine without any issues. May I know the actual cause of this issue? Working platform: Ubuntu 18.04 Boost Version: 1.65.1.0 Regards, Ajay

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[release] Boost 1.79.0
by Marshall Clow 18 Apr '22

18 Apr '22

Release 1.79.0 of the Boost C++ Libraries is now available. These open-source libraries work well with the C++ Standard Library, and are usable across a broad spectrum of applications. The Boost license encourages both commercial and non-commercial use. This release contains numerous enhancements and bug fixes for existing libraries. For details, including download links, see <http://www.boost.org/users/news/version_1.79.0> You can also download directly from: <https://boostorg.jfrog.io/artifactory/main/release/1.79.0/> To install this release on your system, see <http://www.boost.org/doc/libs/release/more/getting_started/index.html> Thanks to everyone who participated in this release. -- The Boost Release Team Marshall Clow, Michael Caisse, Glen Fernandes

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Boost.Intrusive: getting the next element
by Gonzalo Arana 16 Apr '22

16 Apr '22

Hi, Given an element (contained in a list), how may I get the next one, without requiring access to the list itself? I only found this way to get the next element: auto iterator = list.iterator_to(value); ++iterator; return *iterator; But it requires access to the list itself. Best regards, -- Gonzalo A. Arana

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Boost.Text is looking for a (mini-)review manager
by Mateusz Loskot 15 Apr '22

15 Apr '22

Hi, A reminder from the review wizards: The Boost.Text library developed by Zach Laine is still looking for a (mini-)review manager, see details at: https://lists.boost.org/Archives/boost//2020/08/249594.php and https://www.boost.org/community/review_schedule.html Best regards, -- Mateusz Loskot, http://mateusz.loskot.net

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MySQL library scheduled for review
by Mateusz Loskot 15 Apr '22

15 Apr '22

Hi, A brief announcement from the review wizards: Following the proposal [1] and search for the review manager, formal review of the MySQL library [2] has been scheduled to take place between May 9, 2022 - May 18, 2022. Details and links available here https://www.boost.org/community/review_schedule.html We'd like to thank Richard Hodges for volunteering to act as the review manager, again! [1] https://lists.boost.org/Archives/boost/2022/03/252584.php [2] https://github.com/anarthal/mysql/ Best regards, -- Mateusz Loskot, http://mateusz.loskot.net

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[Math / Special Functions] Use more than one user_error function?
by Warren Weckesser 14 Apr '22

14 Apr '22

I am wrapping some boost special functions as NumPy "ufuncs" for the Python library SciPy, and I am setting a policy to control how errors are handled. For example, the wrapper of erf_inv (for C++ types float, double and long double) is wrapped as the function scipy.special.erfinv (i.e. the Python function is erfinv in the module scipy.special). The actual core instantiation of the function for type, say, double, in C++ that is called by the ufunc implementation is double erfinv_double(double x) { return erf_inv(x, special_policy()); } where erf_inv is the Boost function, and special_policy is created as template <class T> T user_domain_error(const char *function, const char * message, const T& val) { sf_error("erfinv", SF_ERROR_DOMAIN, NULL); return std::numeric_limits<T>::quiet_NaN(); } typedef policy< domain_error<user_error>, overflow_error<ignore_error> > special_policy; Note that the error handler is calling sf_error(), a function in the SciPy special library. The first argument is the name of the SciPy Python function. That function might generate a Python warning or set a Python exception, and the name displayed in the error message should be the name of the SciPy function, and not something like "boost::math::erf_inv[...]". This leads to the problem. The above code, with a hard-coded string "erfinv" passed to sf_error(), works for erfinv, but obviously I can't use the same implementation of user_domain_error for a wrapper of, say, tgamma_ratio. So the question is, can different policies be created that have different user-defined error handlers? Or is there a clever way to get the SciPy name into the user_domain_error() function? (I hope there is something simple--I am not a C++ guru, so I may have missed something obvious.) I am considering creating a mapping from some parsed version of the function argument of user_domain_error to the SciPy names. E.g. the function argument could be scanned for the occurrence of "erf_inv", and know that the name "erfinv" should be passed to sf_error(). A table of regex patterns with corresponding SciPy names might do the trick. But I'm wondering if there is a more elegant (and more maintainable) solution. Regards, Warren

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