October 2014 - Boost - lists.preview.boost.org

It's that time again already - Boost 1.57.0 schedule
by Marshall Clow 08 Oct '14

08 Oct '14

It’s that time again. Here’s the schedule for the upcoming 1.57 release. If you’ve got changes that you’ve been putting off making, now’s the time to get busy. * 13-Oct Last day for significant changes * 20-Oct Beta build * 27-Oct Automatic merging turned off, build an RC * 3-Nov Release Boost 1.57.0 Questions? Ask them here. — The Boost release managers. P.S. We’ll be updating the calendar on boost.org/development soon.

5 5

Update on status of C++ 11 only Boost fork/modular distro
by Niall Douglas 08 Oct '14

08 Oct '14

Dear all, You may remember me saying these past six months that I was working on the tools necessary to fork Boost into a C++ 11 only distro which also lets you use Boost libraries individually standalone without the rest of Boost. I have got a first alpha version of my clang AST based local bindings generator working, and you can see it at https://github.com/ned14/local-bind-cpp-library. This tool lets you generate a set of local namespace bindings for some implementation of some library such that your library implementation code need not care what the underlying implementation of dependent library facilities is. This way your Boost library could be using either Boost or the C++ 11 STL and you don't need to care (most of the time). Now I have the first alpha version working and generating a reasonable set of C++ 11 STL bindings (https://github.com/ned14/local-bind-cpp-library/tree/master/include/s tl11), I'll start with porting over my own Boost libraries to it, so Spinlock, Expected, non-allocating future-promise and AFIO will be the first, and with those AFIO should become capable of being completely standalone from Boost whilst still also able to compile against Boost. After that I'll try porting the entire of Boost.Thread over such that Boost.Thread no longer needs Boost. I think that would be hugely useful for people wanting to use potential C++ 17 threading functionality without needing to draw in all of Boost as a dependency, and that might greatly widen the empirical experience new threading facilities might get before the 17 standard. Once I've succeeded with that, if the present situation with Boost has not improved by then, I'll press ahead with a new Boost distro website which score ranks Boost modules according to the scoring manifest I outlined on this list some months ago, and lets you download standalone Boost distros of your choice. Obviously only libraries ported to be standalone capable would be available, so I would hope that if I can demonstrate an easy port with Boost.Thread, others may follow with their libraries. All this work occurs in my free time of a few hours per week, so progress will be slow but steady. Comments on the local namespace binding tool are welcome. Comments on the proposed C++11/14 good practice idiom of binding dependent library APIs into the local namespace are also welcome, because as far as I can tell no one here has discussed a formal set of conventions to make best use of inline namespaces for new libraries. I'll put it another way - local namespace binds are a poor man's version of Herb's proposed C++ ABI facility. As much as they aren't quite as good, they are probably good enough (relative to Herb's most recent proposal). Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

3 7

Fusion and constexpr, C++11 support entirely broken on develop
by Mathias Gaunard 07 Oct '14

07 Oct '14

Hi folks, I recently decided to move all of my code to C++11, and I usually use the develop version of each library so that I can have the latest developments and can easily contribute. However, Fusion appears to be fundamentally broken on develop whenever C++11 is enabled with GCC. It works fine with C++03. I don't think this is a situation that should ever happen; while develop is for libraries undergoing development, it shouldn't be totally broken either. In particular, the problem is that it uses BOOST_CONSTEXPR in contexts where C++11-constexpr is invalid, but where it is valid in C++14. Should there be a separate BOOST_CONSTEXPR14 macro?

3 3

[EXTERNAL] Tickets notifications
by Adam Wulkiewicz 07 Oct '14

07 Oct '14

Hi, AFAIU the notifications about new tickets and updates are sent only to the owner of the library. This is inconvenient since many libraries are developed by a group of people, e.g. Geometry. I'm aware that anyone can get updates if he's on the Cc list but people which are curious about development aren't added to this list automatically. Ideally it would be great if any user could subscribe to get notifications for any library like it's possible on GitHub. Or maybe moving to GitHub mentioned by John in one of the other threads would be the best solution? Anyway, is it somehow possible to receive notifications as a non-owner automatically? If the answer was no, would sending notifications to the library mailing list be a reasonable solution? AFAIU this could be done by adding a "fake" owner with a mailing list email. Regards, Adam

2 1

Submodules of Boost libraries
by Mathias Gaunard 07 Oct '14

07 Oct '14

Hi folks, I'd like to ready my library for inclusion into Boost. My library is made of several modules, and I'd like to keep that into Boost. How does Boost handles multiple submodules within a library submodule?

7 11

[modularization] LocalFunction and ScopedExit cycle
by Vicente J. Botet Escriba 06 Oct '14

06 Oct '14

2 3

[move] Macro for initializing base classes in move ctors.
by Mostafa 04 Oct '14

04 Oct '14

Initializing base classes in move constructors involves some boiler-plate code. Is there a reason why a macro is not provided for it? Something like: #define BOOST_MOVE_INITBASEMOVECTOR(baseclassname, rhs) \ baseclassname(::boost::move(static_cast<baseclassname &>(rhs)))

2 3

[mpl] struct definition and mpl sequence in one shot?
by Adam Romanek 03 Oct '14

03 Oct '14

Hi! This is a re-post from the boost-users mailing list. I have a problem and I'm not sure how to approach it. Currently my code looks like this: struct Definition { typedef boost::mpl::int_<5> A; typedef boost::mpl::int_<3> B; typedef boost::mpl::int_<6> C; typedef boost::mpl::int_<1> D; typedef boost::mpl::vector<A, B, C, D> Seq; }; Here, the number N in mpl::int_< N > denotes some arbitrary decimal number. Then some other code calculates the sum of these numbers up to the type defined by "key", e.g. for Definition::D, the sum is 5 + 3 + 6 (A + B + C). This needs to be done at compile-time. That's why I use mpl::vector and some appropriate meta-programming. I'm wondering whether it would be possible to provide such struct definition without the need to repeat type names in the mpl::vector for Seq type. In other words, I'd probably need a bunch of macros which would allow me to write code like this: struct Definition { FIELD(A, 5); FIELD(B, 3); FIELD(C, 6); FIELD(D, 1); GEN_SEQ() // if needed }; And then Definition::A would still refer to boost::mpl::int_<5>, or would at least allow me to access the boost::mpl::int_<5> somehow, and Definition::Seq would give me the appropriate MPL sequence. Of couse this is just my imagination. The code might look different, I'm just looking for options. Thanks in advance. Adam Romanek

1 0

[Boost] [DateTime] dividing a time_period in N time_periods
by Pablo Madoery 02 Oct '14

02 Oct '14

Hi, I want to make a method which divides a time_period in N time periods, something like this: list<time_period> splitTimePeriod(time_period timePeriod, int n); I actually have made it and although it seems to work it results very inefficient regarding the time it took to divide a large time_period. The method I did is this: list<time_period> splitTimePeriod(time_period timePeriod, int n) { double secsTime = dateTime::diffSeconds(timePeriod.end(), timePeriod.begin()); // tiempo en segundos de cada período de tiempo double ti = secsTime / n; list<time_period> timePeriods; // tiempo de comienzo del primer período de tiempo ptime tpBegin = timePeriod.begin(); // tiempo de fin del último período de tiempo ptime tpLastEnd = timePeriod.end(); for (int i = 0; i < n; i++) { int tUnits = ti * time_duration::ticks_per_second(); // tiempo de comienzo del siguiente período de tiempo ptime tpNextBegin = dateTime::increment(tpBegin, tUnits); // tiempo de fin del período de tiempo ptime tpEnd; if (i == n - 1) { tpEnd = tpLastEnd; } else { tpEnd = dateTime::decrement(tpNextBegin, 1); // guarda para evitar que por cuestiones // de redondeo, el tiempo final de un período // sea mayor que el pasado inicialmente // como argumento de entrada if (tpEnd > tpLastEnd) { tpEnd = tpLastEnd; } } time_period p(tpBegin, tpEnd); // se inserta período de tiempo en la lista timePeriods.push_back(p); // se actualiza el comienzo del siguiente período de tiempo tpBegin = tpNextBegin; } return timePeriods; } Other methods I use are these: double diffSeconds(const ptime &dateA, const ptime &dateB) { time_duration diff = dateA - dateB; return diff.total_seconds(); } ptime increment(const ptime &date, int n) { time_iterator it(date, dateTime::unit); for (int i = 0; i < n; i++) { ++it; } return *it; } ptime decrement(const ptime &date, int n) { time_iterator it(date, dateTime::unit); for (int i = 0; i < n; i++) { --it; } return *it; } const time_duration unit = microseconds(1); ################################################# The question is: is there a better way to accomplish this?

1 0

[static_if] Is there interest in a `static if` emulation library?
by Lorenzo Caminiti 01 Oct '14

01 Oct '14

Hello all, With C++14 generic lambdas, it is possible to implement a sort of `static if` (see also N3613): template< typename T > void assign ( T& x, T const& y ) { x = y; static_if<boost::has_equal_to<T>::value>( std::bind([] ( auto x, auto y ) { assert(x == y); std::cout << "asserted for: " << typeid(T).name() << std::endl; }, x, y) ).else_( [] ( ) { std::cout << "cannot assert for: " << typeid(T).name() << std::endl; } ); } The bind around the generic lambda is a bit verbose... but this code compiles, asserts when called on int, and does not assert when called on x_t (tested on clang 3.4.2): int i = 1; struct x_t { } x; assign(i, i); // asserts assign(x, x); // does not assert I have attached a reference implementation. Thank you. --Lorenzo P.S. I didn't do much background research... sorry if this topic has already been considered and discussed in Boost.

17 43