May 2023 - Boost - lists.preview.boost.org

Re: [boost] charconv for C++11
by Andrey Semashev 11 May '23

11 May '23

On 5/11/23 17:21, Vinnie Falco via Boost wrote: > On Thu, May 11, 2023 at 6:50 AM Robert Ramey via Boost > <boost(a)lists.boost.org> wrote: >> How is this different from boost lexical cast? > > Oh wow this has got to be one of the most amusing things posted to the > mailing list this year with the exception of the mathematical > breakthrough post which attached a gif of the author's monitor showing > the source code instead of providing a github link. I see nothing funny about Robert's post. Asking for comparison with existing solutions is a very reasonable request.

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Re: [boost] charconv for C++11
by Andrey Semashev 11 May '23

11 May '23

On 5/11/23 17:40, Matt Borland via Boost wrote: >> How is this different from boost lexical cast? > > Robert, > > Charconv has a much smaller scope than lexical cast. We convert character arrays into built-in arithmetic types and vice versa. That’s it. Since it has such a narrow scope we can heavily optimize these conversions, which we have sunk a lot of time and effort into. I remember there were a lot of optimizations poured into Boost.Spirit.Qi/Karma. How does your library compare to those implementations?

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Re: [boost] charconv for C++11
by Matt Borland 11 May '23

11 May '23

> How is this different from boost lexical cast? Robert, Charconv has a much smaller scope than lexical cast. We convert character arrays into built-in arithmetic types and vice versa. That’s it. Since it has such a narrow scope we can heavily optimize these conversions, which we have sunk a lot of time and effort into. Matt

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New Website !
by Vinnie Falco 11 May '23

11 May '23

Hey, it’s Vinnie here again! I have some very exciting news to share with you. The renovated website for Boost that we’ve been working on for far too long is now going into its Public Beta phase! Feel free to poke around and kick the tires but keep in mind this is a piece of software and it is still under development. Some parts are missing, incomplete,or buggy. Without further ado: https://boost.revsys.dev This public beta will extend for at least 10 weeks as we finish the last remaining features, and put a few more rounds of polish on the artwork, visual styling, and user interface. After that if you like what you see then we will reset the database, move the repositories and the site to their new homes, and then deploy it for real! If you have suggestions or wish to report problems please feel welcome to open an issue here: https://github.com/cppalliance/temp-site/issues This is a Django site written and maintained in Python by a great group of folks from https://www.revsys.com/. The project is coordinated by Frank Wiles (https://www.revsys.com/about/bio/frankwiles), who shares the same deep commitment to open source that we Boost people do. We chose Django because it is well understood and supported, and because Python composes well with ease of maintenance. This technology stack allows us to execute on our future plans with confidence. Some cool things about this website include: * Log in with GitHub or Google * Light and Dark themes with selector * Asciidoc markdown for dynamic content * Antora content sources for site documentation * Data-driven dynamic pages for libraries and releases * Integrated control panel for producing Boost releases * Full-text search across the documentation and library headers * Professionally designed logo to evoke identity and instant recognition The layout of the site is carefully thought out to make sure that information can be found quickly. Fundamental topics each get a dedicated word in the top level navigation, visible on every page including the site and library documentation. Most of the information which is not library-specific is warehoused in “site docs” which is a collection of individual Antora content sources each authored in Asciidoc. Anyone can update the information on the website simply by contributing to the site-docs via pull request: https://github.com/cppalliance/site-docs Antora and Asciidoc are potent technologies that offer Boost plenty of room to grow to make our site documentation and library documentation more effective for users. While the initial release of the website after the beta will only have the basic functionality, we have many future plans. Some of these you have heard about already and some are new: * A web-based forum which interacts seamlessly with the mailing list * Polls and surveys for measuring the sentiment of Boost users and stakeholders * News section for aggregating off-site links, blog posts, and release progress messages * Integrated Review process. Outcomes go in the database and become dynamic content. * User Profiles record and show activity such as review participation or library submission We’re all very excited and proud of the work that went into this thing and hope that it really fulfills the positive impact that we intended. Thanks! Vinnie

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Re: [boost] charconv for C++11
by Vinnie Falco 11 May '23

11 May '23

On Thu, May 11, 2023 at 6:50 AM Robert Ramey via Boost <boost(a)lists.boost.org> wrote: > How is this different from boost lexical cast? Oh wow this has got to be one of the most amusing things posted to the mailing list this year with the exception of the mathematical breakthrough post which attached a gif of the author's monitor showing the source code instead of providing a github link. Thanks

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Re: [boost] charconv for C++11
by Robert Ramey 11 May '23

11 May '23

On 5/10/23 4:08 PM, Gavin Lambert via Boost wrote: > On 11/05/2023 02:01, Matt Borland wrote: >> What does charconv do? It converts a character sequence into a number >> (from_chars) or converts a number into a character sequence >> (to_chars). How is this different from boost lexical cast? Robert Ramey

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Re: [boost] charconv for C++11
by Gavin Lambert 10 May '23

10 May '23

On 11/05/2023 02:01, Matt Borland wrote: > What does charconv do? It converts a character sequence into a number > (from_chars) or converts a number into a character sequence > (to_chars). This is similar to strtod and printf with a few key > differences. First and most important is a roundtrip guarantee. That > is a number converted into a character sequence, and then back into a > number will be identical to the starting value. Second, you can > easily specify an input/output format with a chars_format argument, > and also provide a target precision. "Roundtrip guarantee" and "specify format/precision" appear to be contradictory goals.

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Re: [boost] charconv for C++11
by Peter Dimov 10 May '23

10 May '23

Matt Borland wrote: > > On May 10, 2023, at 5:42 PM, Dominique Devienne > <ddevienne(a)gmail.com> wrote: > > > > On Wed, May 10, 2023 at 4:01 PM Matt Borland via Boost > <boost(a)lists.boost.org> wrote: > > > >> [...] We use errno rather than std::error_code as specified in the standard. > > > > Hi. Sounded like a good candidate for Boost.Compat (or > > Boost.Polyfill), discussed recently, until that sentence. I'm lucky > > enough to be able to use > > C++17 at work, but if I was on C++11, I'd tend to use such a library > > C++until > > I could use the std one, so deviations like this would complicate > > adoption because moving to std would then be harder. My $0.02. —DD > > Dominique, > > Thanks for the response. We discussed Boost.Compat but decided it is outside > of the scope. For instance <latch> is what set off the discussion and it can be > implemented in ~100 LOC. This implementation of charconv will be around > 10k LOC so it should be in its own library. If the demand signal is to use > std::error_code instead of errno we can make the change. boost/charconv.hpp was initially supposed to be a very light header (with only a few declarations), but since from/to_chars for integral types were moved to the headers because of constexpr, that's no longer the case, so we can probably afford the inclusion of <system_error> without anyone noticing. (Note that std::from/to_chars use std::errc, not std::error_code.)

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Re: [boost] charconv for C++11
by Dominique Devienne 10 May '23

10 May '23

On Wed, May 10, 2023 at 4:01 PM Matt Borland via Boost < boost(a)lists.boost.org> wrote: > [...] We use errno rather than std::error_code as specified in the > standard. Hi. Sounded like a good candidate for Boost.Compat (or Boost.Polyfill), discussed recently, until that sentence. I'm lucky enough to be able to use C++17 at work, but if I was on C++11, I'd tend to use such a library until I could use the std one, so deviations like this would complicate adoption because moving to std would then be harder. My $0.02. --DD

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charconv for C++11
by Matt Borland 10 May '23

10 May '23

I’m Matt Borland, who many might recognize from my work in Boost.Math and fewer might know from Boost.Multiprecision. I’m putting the finishing touches on a new library that I hope will become part of Boost, after a successful formal review. This library is essentially already part of C++17 and later but in the Boost tradition we wish to provide it for users and other Boost libraries that want to fully support C++14 or C++11. What does charconv do? It converts a character sequence into a number (from_chars) or converts a number into a character sequence (to_chars). This is similar to strtod and printf with a few key differences. First and most important is a roundtrip guarantee. That is a number converted into a character sequence, and then back into a number will be identical to the starting value. Second, you can easily specify an input/output format with a chars_format argument, and also provide a target precision. Third, it is much easier to check for errors. Strtod has a few different ways of reporting different errors whereas the results of to_chars returns an error code from errno. Using this is no different from POSIX where you check for 0 and then move on. We use errno rather than std::error_code as specified in the standard. This allows us to avoid including <system_error> and is more ergonomic. Lastly, charconv is significantly more performant than strtod and printf. We utilize algorithms derived from Daniel Lemire’s “Number Parsing at a Gigabyte per Second” and Junkey Jeon’s Dragonbox. You can read about those here: https://arxiv.org/abs/2101.11408 https://github.com/jk-jeon/dragonbox And here are a number of example snippets: https://develop.charconv.cpp.al/ As of now the library supports all built-in integer types, signed and unsigned __int128, float, and double. I am striving to add support for long doubles (64, 80, and 128-bit) to both from_chars and to_chars. With these in hand I have a mind to experiment with integrating this into Boost.JSON, which for lack of a better phrase, sure could use a bit of help with its conversions between IEEE floats and decimal strings. This will also help with checking our validation, accuracy, and performance. If you want to check out the library it is here: [https://github.com/cppalliance/charconv](https://github.com/CPPAlliance/cha… It is designed to be built and used in the Boost superproject. This means that if you want to clone it, you should place the repository in the libs/charconv directory of your local superproject. Feel free to hammer on it, and report any errors or performance issues that you run into. Also if you find the docs could use improvement please open an issue so that we can address it. These will help us ensure that we have the highest quality product before attempting to pass a formal review for inclusion in Boost. Thank you for your time. Matt Borland

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