January 2015 - Boost - lists.preview.boost.org

[mixin] Library name
by Borislav Stanimirov 04 Feb '15

04 Feb '15

To those unfamiliar with the Boost.Mixin - it is a new library submitted for review. The docs are here: http://ibob.github.io/boost.mixin/index.html The code is here: https://github.com/iboB/boost.mixin It has been suggested multiple times that perhaps the name "mixin" isn't appropriate, so I was wondering if I can find a better one. The current name, mixin, is, as the library itself, inspired by the mixins in the Ruby programming language. However, it doesn't do exactly what Ruby's mixins do (as mentioned here: http://ibob.github.io/boost.mixin/boost_mixin/introduction.html#boost_mixin… ) My current alternative ideas are: * EntityComponent - not great since it doesn't exactly follow the entity-component-system pattern, although it can be said that it allows the construction of entities from components. * DynamicMixin - to emphasize that it's not to be confused with the CRTP mixins. It still has "mixin" in it's name though. * Trait - since it resembles the traits in Self, Scala, PHP, etc. However, a trait is more a "compile time" feature (even when talking about PHP) * TypeComposition or TyCo - a very vague description * Polymorph - since it allows the composition of polymorphic types at run time, but that's pobably even more vague Other ideas are welcome. Thanks -- Borislav

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Hi everyone
by PUNEET KOHLI 03 Feb '15

03 Feb '15

Hello guys. I came to know about your organization from the melange page.Your projects really got me interested. I am a very proficient in c & c++. I have been doing a lot of competitive programming for more than a year so , i can certainly code.I wish to apply to GSOC this year and would love the opportunity if it comes from your organization. Thus, i am looking for a way to contribute and work for you.

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[sync] [thread] Faster mutex
by Antony Polukhin 02 Feb '15

02 Feb '15

Hi, One of the Mesa developers implemented a faster mutex: http://lists.freedesktop.org/archives/mesa-dev/2015-January/075260.html According to the sources of glibc, Mesa's mutex has a much smaller size (only 1 uint32_t vs 6 ints + 2 pointers), performs less actions before and after the actual syscall (no getting and setting of the mutex->__data.__owner, no type field checks) This gives an ~10% speedup. Just curious, maybe ideas from Mesa's mutex could be useful for some of the Boost libraries. -- Best regards, Antony Polukhin

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[predef][check] linux clang triggers BOOST_MAC_OS
by Jürgen Hunold 01 Feb '15

01 Feb '15

Hi! I'm using clang + libc++ on Linux and the Predef "check" magic activates "BOOST_MAC_OS". That means I get: Performing configuration checks - symlinks supported : yes warn: Unable to construct ./info_as_objcpp warn: Unable to construct ./info_as_objc - BOOST_OS_MACOS : yes when running the predef test suite. Command chain: cd libs/predef/test rm -rf ../../../bin.v2/libs/predef/ ../../../bin.v2/check/ ../../../bin.v2/project-cache.jam b2 -a --verbose-test 2>&1 -d+2 --debug-configuration | tee verbose.log verbose.log is attached as zip file. And in fact the macos test are run: clang-linux.compile.c.without-pth BOOST_ROOT/src/devel/boost/bin.v2/libs/predef/test/macos_endian.test/clang- linux-3.7.0/debug/macos_endian.o which is only supposed to be run on macos. The test even passes because it internally checks for "__APPLE__" being defined, which should probably be removed, as the check should be done by the build system. Compiler: clang++ -v clang version 3.7.0 (trunk 227683) Target: x86_64-unknown-linux-gnu Thread model: posix That is current clang trunk. Though I'm already running with -d+2 --debug-configuration I get no output from the configuration test itself. Any ideas on how to debug this further? Yours, Jürgen -- * Dipl.-Math. Jürgen Hunold ! * voice: ++49 4257 300 ! Fährstraße 1 * fax : ++49 4257 300 ! 31609 Balge/Sebbenhausen * jhunold(a)gmx.eu ! Germany

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Change in range requirements
by Ganssauge, Gottfried 01 Feb '15

01 Feb '15

Please consider the following program: bool predicate(char c) { return c != '0'; } int main (int, char **) { using namespace boost::adaptors; boost::copy( boost::make_iterator_range( std::istream_iterator<char>(std::cin >> std::noskipws), std::istream_iterator<char>()) | filtered(predicate), std::ostream_iterator<char>(std::cout)); return 0; } It works brilliantly with boost-1.54 although std::istream_iterator is only an input iterator. Recently I tried switching to boost-1.57, but suddenly this program stopped working - it won't compile any longer, because istream_iterator is not a forward_iterator: g++ -I ~/source/aurora-python/test-build/parts/boost range_filter.cpp -o range_filter ... # lots of gobbledygook skipped range_filter.cpp:18:64: required from here /home/gotti/source/aurora-python/test-build/parts/boost/boost/concept_check.hpp:210:13: error: conversion from 'boost::iterators::single_pass_traversal_tag' to non-scalar type 'boost::iterators::forward_traversal_tag' requested Y y = x; ^ When I build an equivalent program using boost::filter_iterator it keeps compiling and working fine. Why is it, that the requirements for certain range adaptors (e.g. filtered, transformed) suddenly exclude input ranges? The corresponding iterator adaptors keep working... Gottfried Ganßauge Entwickler Content Engineering & Development ------------------------------------------------------------------ Haufe-Lexware GmbH & Co. KG Ein Unternehmen der Haufe Gruppe Munzinger Str. 9, 79111 Freiburg Tel. +49 761 898-0 Internet: http://www.haufe-lexware.com ------------------------------------------------------------------ Kommanditgesellschaft, Sitz und Registergericht Freiburg, HRA 4408 Komplementäre: Haufe-Lexware Verwaltungs GmbH, Sitz und Registergericht Freiburg, HRB 5557; Martin Laqua Beiratsvorsitzende: Andrea Haufe Geschäftsführung: Isabel Blank, Markus Dränert, Jörg Frey, Birte Hackenjos, Randolf Jessl, Markus Reithwiesner, Joachim Rotzinger, Dr. Carsten Thies ------------------------------------------------------------------

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[type_traits] Rewrite and dependency free version
by John Maddock 01 Feb '15

01 Feb '15

I'm going to throw this out there to see what folks think: In a branch called "Version2", see https://github.com/boostorg/type_traits/tree/Version2 is a partially rewritten type_traits lib: it doesn't yet contain all the traits of the old one, but there's a pretty good selection to test. The main pros for this version are: 1) Zero dependencies other than Boost.Config. 2) No horrible macro-obfuscation - all "real code", making it easier to read and maintain. 3) Substantially reduced template instantiations where practical - often half as many as before. 4) Substantially reduced #includes - the aim is that all files should include only what they need and no more - with what's needed determined by the actual implementation variant when appropriate. There were also a lot of spurious #includes left over from old workarounds no longer used. The main cons: 1) I don't know what I've broken, but surely something, you can help by testing but I would guess we would never be 100% sure it's all right until it's out in the field. This is the main reason for avoiding this until now. 2) MPL interoperability should still work, but files which expect type_traits headers to have included mpl ones will be broken unless they explicitly include what they need. 3) Current MPL inter-operability is fragile see https://github.com/boostorg/type_traits/blob/Version2/include/boost/type_tr… 4) Function dispatching to an mpl::bool_ involves an (inline) function call where as the old inheritance scheme did not. This should mostly disappear once optimizations are turned on, but is still a potential issue for some folks I suspect. 5) I haven't got to the "difficult" headers like common_type.hpp yet. 6) Whatever I've forgotten ;) Of course (2), (3) and (4) could be solved by making mpl's bool.hpp some kind of "core" header. So... what I need from you kind folks is: * Is this the right way forward? * Can you test with your favourite compilers and compare with results for develop - So far I've tested with msvc-10,11,12,14 Intel 14,15, GCC-4.5.4...4.9.1, plus a reasonably recent clang. * If anyone would like to help converting further traits all help would be much appreciated.... Oh and the compiler requirements in the docs are all wildly out of date too... Regards, John.

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Bugs
by Mudit Sharma 31 Jan '15

31 Jan '15

Where can i find bugs which can be solved for boost? Thanks!

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libraries affected by common factor gcd and lcm namespace change moving from math to integer library
by Paul A. Bristow 30 Jan '15

30 Jan '15

A quick grep (for gcd_ and lcm_ in *.*pp) suggests that the following libraries are affected by gcd and lcm namespace change moving from math to integer library. At present, math_fwd.hpp provides some typedefs and declarations needed for these, and a copy of the common factor codes, so nothing may fail immediately, but these duplicate will be removed after at least one release. Chrono Interprocess Math Multiprecision Ratio Rational Units All libraries should use the declarations in integer/integer_fwd.hpp and /integer/common_factor_ct.hpp and /integer/common_factor_rt.hpp. (And there may be documentation changes too?) Something needs to be done ;-) (If you want *me* to resolve anything, then I need write access to your library). Paul --- Paul A. Bristow Prizet Farmhouse Kendal UK LA8 8AB +44 (0) 1539 561830

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[uuid] Issue 9407: please merge fix
by Antony Polukhin 30 Jan '15

30 Jan '15

Hi, Looks like Boost.UUID library is not maintained. Could someone take care of that library. Especially I'm interested in applying a pull request to fix 9407 <https://svn.boost.org/trac/boost/ticket/9407> issue ( https://github.com/boostorg/uuid/pull/2) Pull request has been already reviewed by Andrey Semashev and significantly improved. -- Best regards, Antony Polukhin

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[Filesystem] problem with tutorial documentation
by Tom Yonkman 30 Jan '15

30 Jan '15

On the http://www.boost.org/doc/libs/1_57_0/libs/filesystem/doc/tutorial.html page, the text after the tut4.cpp code box appears to be obsolete as it doesn't match up with the current code in tut3.cpp and tut4.cpp. Tom Yonkman

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