October 2018 - Boost-users - lists.preview.boost.org

Boost iterator facade implementation
by rmawatson rmawatson 26 Oct '18

26 Oct '18

https://github.com/boostorg/iterator/blob/boost-1.63.0/include/boost/iterat… I was wondering about is_non_proxy_reference<Reference,Value> in this metafunction. It appears to select between postfix_increment_proxy<Iterator> and writable_postfix_increment_proxy<Iterator> based on whether Reference is the same type as Value ignoring cv& what is the case that writable_postfix_increment_proxy<Iterator> is selected. So when is Reference going to be a different 'base type' to Value? is this to support user returning their own proxy or something?

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[asio] Advice on implementing rate-limiting for async_write
by Kyle Ketterer 25 Oct '18

25 Oct '18

Hello fellow Boost friends, I am looking into some advice on implementing rate-limiting using using Boost ASIO with async_write. I am working on a Enterprise File Backup solution named Vessel @ https://github.com/VesselEnterprise/vessel-backup. My project uses Boost through and through. The use case is as follows: - Many users on the same network/subnet may be transferring files at once - I want to add the feature of being able to limit upload speed to the storage provider (AWS, Azure, etc) The request starts as follows: (pseudo code) Let's say we have a string of 1000 bytes we want to send to a server: const std::string& request //Passed to member function and make_shared<>() > to member var on stack to ensure lifetime of async operation Let's also say we want to limit the transfer speed to 100 bytes/second size_t transfer_max = 100; Should we start the request with async_write() on the socket? //Ensure that no more than transfer_max bytes are sent during the first write > boost::asio::async_write(*m_socket, boost::asio::buffer(http_request, > transfer_max), boost::bind(&HttpClient::handle_write, this, > boost::asio::placeholders::error, > boost::asio::placeholders::bytes_transferred )) ; > Here is where I have questions. In the completion handler handle_write(...), we need to continue to call async_write() until all bytes have been written and determine the current transfer rate, and sleep the thread if necessary. When sending the next set of bytes, is it best to explicitly declare a buffer and consume or use a pointer to the char array? void HttpClient::handle_write( const boost::system::error_code& e, size_t > bytes_transferred ) > { > /** > ** Do some stuff here to determine transfer rate, and sleep if > necessary... > */ > > //Pseudocode > if ( transfer_rate > transfer_max ) > { > //Possibility 1? > auto buffer = boost::asio::buffer(request, transfer_max); > buffer.consume(total_bytes_transferred_so_far); > boost::asio::async_write(*m_socket, buffer, > boost::bind(&HttpClient::handle_write, this, > boost::asio::placeholders::error, > boost::asio::placeholders::bytes_transferred )) ; > //Possibility 2? > boost::asio::async_write(*m_socket, > boost::asio::buffer(&request[total_bytes_transferred_so_far], > transfer_max), boost::bind(&HttpClient::handle_write, this, > boost::asio::placeholders::error, > boost::asio::placeholders::bytes_transferred )) ; > return; > > } > //...eof > } Advice on the topic is greatly appreciated. If I am way off, just let me know :) Thanks! -- Kyle Ketterer <reminisc3(a)gmail.com>

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[gil] Who uses Boost.GIL?
by Mateusz Loskot 24 Oct '18

24 Oct '18

Dear Boost Users, I'm interested in collecting a list of software projects using or depending on, directly or indirectly, Boost.GIL. If you stick boost::gil anywhere in your code, please tell me about it, drop link to your project. I'd like to list users of GIL at https://github.com/boostorg/gil/wiki/Who-Uses-GIL If you ask me to not to, I'll respect your request. Thank you! Best regards, -- Mateusz Loskot, http://mateusz.loskot.net

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[release] 1.69.0 deadline for new libraries approaching
by Marshall Clow 22 Oct '18

22 Oct '18

It's that time again! On Wednesday, the master branch will be closed for adding new libraries. Upcoming dates: * 24-Oct: Boost 1.69.0 closed for new libraries and breaking changes * 31-Oct: Boost 1.69.0 closed for major code changes * 7-Nov: Boost 1.69.0 closed for beta * 14-Nov: Boost 1.69.0 beta 1 * 5-Dec: Boost 1.69.0 closed for release * 12-Dec: Boost 1.69.0 release -- The Boost Release Team

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[Range] Help with syntax
by Robert Jones 19 Oct '18

19 Oct '18

Given struct S { int i( ) const; }; vector<S> v; set<int> s; I want to write (approximately) for_each( v | transform( []( const S & s ){ return s.i( ); } ), s.emplace ); With the intention putting all the i's extracted from v into the set s. My syntax is all over the place, and I'm not sure how to express the s.emplace bit. Also is there a better way to say the whole thing? If I were doing push_back instead of emplace there's a facility especially for that, but I guess Boost::Range hasn't embraced emplace because range-v3 is around now. I'm sure some of you are fluent in this stuff! Kind Regards Rob.

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[Boost-serialization] undefined reference error
by phillip mobley 19 Oct '18

19 Oct '18

Hello all, I ma having a major issue with the boost library. I have been having this issue for a few days now and I can't seem to figure out what the problem is. Basically, I get this error message after my linker: "undefined reference to `boost::archive::text_oarchive_impl<boost::archive::text_oarchive>::save(std::string const&)'" My complete linker command is as follows: " -L. -L/usr/lib/x86_64-linux-gnu -L/usr/local/lib -L/usr/lib/lapack -lfreetype -lGLEW -llapack -lboost_serialization -lglut -lGL -lGLU -L/usr/local/lib -pthread -lwx_gtk2u_xrc-3.1 -lwx_gtk2u_stc-3.1 -lwx_gtk2u_richtext-3.1 -lwx_gtk2u_ribbon-3.1 -lwx_gtk2u_propgrid-3.1 -lwx_gtk2u_aui-3.1 -lwx_gtk2u_gl-3.1 -lwx_gtk2u_html-3.1 -lwx_gtk2u_qa-3.1 -lwx_gtk2u_adv-3.1 -lwx_gtk2u_core-3.1 -lwx_baseu_xml-3.1 -lwx_baseu_net-3.1 -lwx_baseu-3.1" I built Boost 1.64 from the source and kept the default values. I also built the whole library. My Boost library is built into the /usr/local folder. I am pretty sure that I am referencing the linker libraries correctly but I can't seem to figure out why I would be getting this error message. Has anyone had an issue similar to this before?

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[Boost.Serialization] Unnecessary use of <iostream> in boost/serialization/export.hpp
by dariomt＠gmail.com 18 Oct '18

18 Oct '18

Hi, I see #include <iostream> in header boost/serialization/export.hpp, but that header uses nothing from namespace std. To me it looks like that #include is unnecessary, as all my code compiles fine if I remove that #include, but maybe I'm wrong. Was it included by mistake? PS: I'm using Boost 1.64, but I see the same #include in Boost 1.68

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Questions about Boost multiprecision library.
by A Z 11 Oct '18

11 Oct '18

I have some basic startup for use questions pertaining to the Boost multiprecision library. I have downloaded the set of 64 bit .dll files successfully online, and would like some help points to help me get going. *I have heard that there are some strange results that can happen if you are quizzing multiprecision for trigonometry and try to keep using the double type. Is this true, so that I can just kee relying on the std library instead? -What is the name of the 64 bit windows .dll, or .dll files, that are the ones for the multiprecision library? -If I wish to go into arbitrary precision and scale numbers, what is the type I should use for an integer? What is the #include statement I should use, and how do I specify the number of whole number points and decimal points, before starting my operations? -If I wish to go into arbitrary precision and scale numbers, what is the type I should use for a rational number? What is the #include statement I should use, and how do I specify the number of whole number points and decimal points, before starting my operations? -For these two types, I wish to do sine, cosine, tangent, arcsine, arccosine, arctangent, base 10 logarithm, base e logarithm, power, nth root. I also want to obtain pi, but also Euler's constant, to any number of significang figure or decimal places that I would like. -If the files are separate for the function support or not, what are the 64 bit .dll files for this? What #include statements should I use?

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signals2
by tim＠raisedbar.net 04 Oct '18

04 Oct '18

Hi, A friend pointed me at this library, as it may solve a problem for me. Am I correct in thinking that a signal can be activated once all of its slots are filled and not before? Best wishes. Tim Burgess Raised Bar Ltd. E: <mailto:tim@raisedbar.net> tim(a)raisedbar.net M: +44 (0)7989 486976

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Twenty years and time to retire
by Beman Dawes 04 Oct '18

04 Oct '18

The idea behind Boost was hatched in March, 1998, and the proposal document <https://www.boost.org/users/proposal.pdf> was released May 6, 1998. That makes Boost twenty years old, and makes me twenty years older. It is high time I retire from Boost; I haven't been able to contribute for some time now. Thanks to all of you who made Boost such an overwhelming success in the past and will drive Boost forward into a bright future! --Beman

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