- Boost-users - lists.boost.org

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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Re: [Boost-users] [boost] [release] Boost 1.79.0
by Glen Fernandes 14 Apr '22

14 Apr '22

On Wed, Apr 13, 2022 at 3:17 PM Andrey Semashev wrote: > > On 4/13/22 21:04, Vinnie Falco via Boost wrote: > > The thing that I absolutely LOVE about a new release of Boost, is that > > someone always reports a crashing bug just after the release is > > published: > > > > <https://github.com/boostorg/json/issues/692> > > We have a practice of adding post-release patches to release notes. Updated: https://github.com/boostorg/website/commit/0752dee32f149db385ea0f635886221b… Added /patches/1_79_0/0001-json-array-erase-relocate.patch and release notes updated. Glen

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Unlock / free a boost::asio::strand in beast?
by Markus Bonk 13 Apr '22

13 Apr '22

Hi, The application is using beast / websockets to communicate with a websocket server. A specific onread handler which is initially running on the stream strand needs to read another value from the websocket server to proceed. It sends a message and then waits on a future. This deadlocks the websocket communication. If instead of a strand a mutex were being used could unlocking the mutex before sending the message after the data that needs to be protected / requires synchronization has been already acquired and the resources would be available for the next handler. Is there any way of 'unlocking' the strand i.e. setting the state of the handler's thread so that 'isrunning_on_strand' = false and the stream can continue servicing the incoming messages? Thanks for any pointers. Markus ________________________________ Markus Bonk Senior Software Engineer [cid:3dconnexion_bd84aa85-40b4-4789-87b1-4c8f703d9ae6.gif] Clarita-Bernhard-Str. 18 81249 M?nchen Germany markus_bonk(a)3dconnexion.com<mailto:markus_bonk@3dconnexion.com><mailto:%7BE-mail%7D> www.3dconnexion.com<http://www.3dconnexion.com> Gesch?ftsf?hrer: Antonio Pascucci Sitz der Gesellschaft: M?nchen Registergericht: M?nchen HRB 99232 This email and any files transmitted with are from 3Dconnexion GmbH. The contents of this email and any attachments are confidential to the intended recipient. They may not be disclosed to or used by or copied in any way by anyone other than the intended recipient. If this email is received in error, please contact 3Dconnexion GmbH by calling +49 89 8974542-0 and then delete it. Please note that neither 3Dconnexion GmbH nor the sender accepts any responsibility for viruses and it is your responsibility to scan or otherwise check this email and any attachments. Any opinion expressed in this email are those of the individual and not necessarily those of 3Dconnexion GmbH. 3Dconnexion GmbH processes and stores for commercial purposes your personal data, collected upon your consent, in accordance with its privacy policy available at https://www.3dconnexion.eu/privacy.html, which has been drafted in accordance with Regulation (EU) no. 679/2016 and all applicable local data protection laws and regulations of the countries where the company operates. To revoke your consent or exercise all your rights with regards to personal data, please contact us at privacy(a)3dconnexion.com<mailto:privacy@3dconnexion.com>.

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Reading a large compressed .gz file without uncompressing it
by bharath pagadala 05 Apr '22

05 Apr '22

Hi Team, My requirement is I want a read a large .gz file and stream data without uncompressing it. Does the boost library help me to achieve this. Is there any function in the boost library which help me stream data directly without uncompressing the input .gz file. Please respond on this thank you in advance. Cheers, Bharat Pagadala

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The Boost Statechart Library AND boost::bind
by Jinlong Shen 05 Apr '22

05 Apr '22

Can the statechart library be updated to treat the boost::bind warning about namespace. See here for details. https://stackoverflow.com/questions/53203970/why-boostbind-insists-pulling-…

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[Nowide] Nowide and Property Tree file IO
by William Kappler 03 Apr '22

03 Apr '22

I'm trying to sidestep some issues with unicode filenames on Windows (MSYS64) using Boost.Nowide. Specifically, my program operates in UTF-8, and providing that to std/Boost functions yields incorrect filenames due to them being interpreted as UTF-16 (or something along those lines). However, the primary functions I have issues with are from Boost.PropertyTree. Specifically, read_json and write_json. These functions don't seem to be Nowide-friendly. I tried just calling boost::nowide::nowide_filesystem() before my json calls, hoping it would work; it did not, I got the same mangled filenames. My next thought was to see if a nowide stream could be substituted into the stream-taking variants of read_json/write_json; it cannot be, they aren't compatible. The only option that seems to leave is something along these lines: https://stackoverflow.com/a/21537818, but using Nowide to read in the file. That adds a lot of steps (and possibly memory usage). It feels like I'm missing something. Any suggestions would be appreciated. Thanks in advance. :-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:- *William E. Kappler II* Software Designer and Programmer william-kappler.com

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boost python AttributeError
by Chien-Yu Chen 03 Apr '22

03 Apr '22

hi I followed the basic boost python examples, both hello_ext.greet() and hello.World() and both are giving me AttributeError error, like AttributeError: module `hello` has no attribute 'greet' dumpbin does show that I have PyInit_hello exported out. Please let me know if I am doing something wrong as this should be trivial. thx -- Any MicroSoft extension file will directly go to trash without any warning and regret.

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