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1.61 release notes
by John Maddock 06 May '16

06 May '16

Is it too late to add release notes? Forgetfully yours, John.

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Boost.Proto: specializing context::eval classes
by Brook Milligan 06 May '16

06 May '16

I am trying to use Boost.Proto with some user-defined function terminals. Following the documentation, this requires specialization of context::eval classes to handle new terminals. (Using the callable_context<> mechanism is too simplistic because that seems to require a uniform result_type.) However, doing as suggested (see the "Defining an Evaluation Context" section) does not compile when function terminals are involved. My solution is a new traits class that deduces the type of a terminal. This does allow successful specialization of context::eval on the type of terminal, even with functions. To illustrate this, I have attached a set of three files, one implementing an example proto function, one implementing the relevant metafunction, and one demonstrating both use cases: the one corresponding to the Boost.Proto documentation and the one corresponding to my alternative. I would appreciate comments on the following: - Is this a valid problem and a valid solution or have I missed a standard method using Boost.Proto that works to solve this pattern? - Is this the standard way of creating function terminals in Boost.Proto or have I done something there to trigger the problem? - If the answer to these questions indicates a missing feature within Boost.Proto, what is the process for fixing that? Thanks for any help you can offer. Cheers, Brook

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[random] Using random_device needs to link to built library
by Edward Diener 06 May '16

06 May '16

Evidently if I use boost::random::random_device class in code I need to link to the built random library. Otherwise the random library is header only. Shouldn't this be mentioned somewhere in the Boost random documentation ?

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[generic programming] header file for general "default" operations for C++ classes
by Walt Karas 05 May '16

05 May '16

In C++, a default assignment operator is generated for a class if all of its components (data members and base classes) have an assignment operator. There are plans in C++17 to do something similar for comparison operators. This header, in https://github.com/wkaras/C-plus-plus-library-default-operators , facilitates that, more generally, if there is an operation on all the components of a class, a single macro invocation can provide this operation on the class as well. A big drawback is that it's very intrusive into the class definition. Each class component must be defined using a macro, COMPOSITE_OP_MBR_T(int) i; for examle. The class will in truth be a template, with the template parameter being defaulted for normal usage. I don't know which, if any, existing Boot library this header would belong in.

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[Promotional] ghournal - a commandline based blog engine for gh-pages
by Ganesh Prasad 05 May '16

05 May '16

***DISCLAIMER*** *This is a self promotional message and quite unrelated to Boost and C++. But I believe, it's something that makes lives of developers easier, in fact I built it to make my life easier. Now, as an OpenSource activity it needs some promotion to attract users and contributors alike. * *Also, I am not good at writing promotional messages, so this mail might look really messy. Hence, apologies in advance.* *********************************************************************************************** git is the lifeline of most of the OpenSource activities around the globe. We all write code, create projects on github and push our changes to the repo and blah blah blah... That's what we all do, git add | commit | merge | push are probably the most used commands on a developer's console, the command pattern is muscle memory. Now with the introduction of github-pages it has been possible to host static websites for your projects on github, most of the serious projects on github already have their static websites there. Sometimes we want to maintain blogs for our projects on the project website. But github-pages being a static platform does not provide backend scripting or database capabilities. So, conventional blogging (like on blogger/wordpress) is not natively possible on github-pages. Sometimes we wish that blogging was possible and conveniently easy to use on github-pages. Also, some of us (like me for instance) sometimes think like, "life would have been easier if blogging was as simple as git init..git commit...git push, maybe something like blog init... blog new... blog publish". *ghournal <https://www.npmjs.com/package/ghournal>* as a tool designed for users of git, makes these above wishes come true. It is a command line based blog management tool for static web hosts, targeted primarily towards the github-pages platform. *ghournal <https://www.npmjs.com/package/ghournal> *exposes a git like command structure for blogging from the terminal. Creating a blog is as easy as 'ghournal init', adding a new post is as simple as 'ghournal new <postID>' etc. The complete command structure is documented in the project README. *ghournal <https://www.npmjs.com/package/ghournal>* is written in javascript and is available on npm. Hence installing and using it can not me easier. In short, it is designed to make the lives of developers who want to blog about their projects easier. So, if this sounds cool, please have a look at https://www.npmjs.com/package/ghournal and thanks :) sincerely Ganesh Prasad

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[config] Checking if put_time is in iomanip
by Edward Diener 04 May '16

04 May '16

Does anybody know of a way to check if the std::put_time functionality is part of iomanip ? It is supposed to be a part of C++11, but Boost.Config does not have any general way to check for C++11 that I know about. Nor do I find anything in SD-6 which would tell me if std::put_time is supported.

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[chrono] Header only library build and boost::system dependency
by Edward Diener 04 May '16

04 May '16

The documentation for chrono says: "How to Build Boost.Chrono as a Header Only Library? When BOOST_CHRONO_HEADER_ONLY is defined the lib is header-only. If in addition BOOST_USE_WINDOWS_H is defined <windows.h> is included, otherwise files in boost/detail/win are used to reduce the impact of including <windows.h>. However, you will either need to define BOOST_CHRONO_DONT_PROVIDE_HYBRID_ERROR_HANDLING or link with Boost.System. " So I have: #define BOOST_CHRONO_HEADER_ONLY #define BOOST_CHRONO_DONT_PROVIDE_HYBRID_ERROR_HANDLING #include <boost/chrono.hpp> followed by some code using chrono, and I still get when linking my exe: gcc.link C:\Programming\VersionControl\modular-boost\build\boost\bin.v2\libs\cxx_dual\test\test_chrono.test\gcc-mingw-5.3\debug\test_chrono.exe C:\Programming\VersionControl\modular-boost\build\boost\bin.v2\libs\cxx_dual\test\test_chrono.test\gcc-mingw-5.3\debug\test_chrono.o: In function `_static_initialization_and_destruction_0': E:\Programming\VersionControl\modular-boost\libs\cxx_dual\test/../../../boost/system/error_code.hpp:221: undefined reference to `boost::system::generic_category()' E:\Programming\VersionControl\modular-boost\libs\cxx_dual\test/../../../boost/system/error_code.hpp:222: undefined reference to `boost::system::generic_category()' E:\Programming\VersionControl\modular-boost\libs\cxx_dual\test/../../../boost/system/error_code.hpp:223: undefined reference to `boost::system::system_category()' collect2.exe: error: ld returned 1 exit status Is there a way to use chrono without having to link boost::system ?

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Naming convention of iterated binary operation
by Jeremy Murphy 03 May '16

03 May '16

Dear list entities, is there such a convention or precedent for naming an iterated binary operation? For example, Boost.Functional/Hash has an iterated hash() called hash_range(). I don't mind the "_range" suffix but I prefer the "iterated_" prefix based on the mathematical definition: https://en.wikipedia.org/wiki/Iterated_binary_operation The case in point is gcd() in Boost.Math: we want to provide an iterated gcd but we can't quite decide how to name it. I like the "iterated_" prefix but I would rather go with whatever might be the convention. Thanks, cheers. Jeremy

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[predef] check and require logical operators and multiple expression questions
by Edward Diener 01 May '16

01 May '16

Is there any difference in the result when you use the 'and' logical operator or simplty specify more than one expression: lib my_special_lib : source.cpp : [ predef-require "BOOST_OS_WINDOWS" and "BOOST_COMP_CLANG"] ; lib my_special_lib : source.cpp : [ predef-require "BOOST_OS_WINDOWS" "BOOST_COMP_CLANG"] ; Are both the above equivalent ? Can I use both 'and' and 'or' in an expression ? If so does 'and' bind before 'or' does, so that 'expression1 and expression2 or expression3' is conceptually '(expression1 and expression2) or expression3' ? Can I use parentheses to bind an expression with 'and' and 'or' ?

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boost chrono bad_cast (gcc > 4.9 on Mac)
by Min Yang Jung 01 May '16

01 May '16

Hi All, I was wondering if Boost.Chrono works with gcc > 4.9 on Mac. When system_clock::now() is called, it throws an std::bad_cast exception. The binary from the same code doesn’t have the issue if compiled with clang on Mac and gcc > 4.9 on Linux. The gcc compilers that I use are macport-installed gcc 4.9 and 5.0 (g++-mp-4.9 and g++-mp-5.0) on Mac. Any help would be appreciated. Thanks. Regards, Min Yang Jung

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