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Template metaprogramming libraries
by Ábel Sinkovics 19 Sep '11

19 Sep '11

Hi Boost developers, I am a PhD student at Eotvos Lorand University, Budapest. My research area covers C++ template metaprogramming. As part of my research I have developed four template metaprogram libraries based on Boost.MPL. On my conference appearances I was encouraged to submit my libraries to the Boost sandbox. Here is a short summary of the libraries: metaparse A tool for building embedded DSLs in C++. This is a compile-time parser generator library. Using it one can build parsers that take compile-time strings as input text and parse them as part of the C++ compilation process. One can think of it as using Spirit at compile-time. safe_printf Typesafe printf implementation using metaparse. It provides printf (sprintf, fprintf) functions taking the format string as a template argument and type-checking it at compile-time. It is a practical application of the metaparse library. metamonad Monad implementation for C++ template metaprograms. The library provides a framework for using monads in C++ at compile-time. The library provides an embedded language for C++ template metaprogramming similar to Haskell's do-notation. Using it, template metaprograms can be written with a syntax that resembles procedural code. Unlike the approach presented at this year's Boostcon, my library focuses on monads evaluated completely at compile-time. The library contains implementations for a number of monads available in Haskell (Maybe, Either, Reader, Writer, State, etc.). As an addition, the library contains a monad for error propagation in C ++ template metaprogramming. Based on the similarities of monadic error propagation and exception handling in runtime C++, the library provides an embedded language that resembles to exception handling. Using it, one can throw and catch "exceptions" at compile-time. metatest Unit testing library for C++ template metaprograms. If a metaprogram test case fails, it does not produce compilation error, but makes the result information available at runtime. Using this one can generate advanced reports and integrate the results into unit testing frameworks for runtime C++ code. The library contains code that integrates it with Boost.Test. The source code, unit tests and examples for the library are available at http://github.com/sabel83/mpllibs I've tested the libraries with the following compilers: - gcc 4.5 - clang 2.8 - Visual C++ 10 Full documentation of the libraries can be found at http://abel.web.elte.hu/mpllibs. Publications related to the libraries: http://abel.sinkovics.hu/?mod=kutat I would like to ask you for access to the Boost sandbox and I would appreciate all feedback from the Boost community. Best regards, Abel Sinkovics

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De Brujin Bind and nested bind calls (was: Re: Template metaprogramming libraries)
by Thomas Heller 19 Sep '11

19 Sep '11

On Fri, Sep 16, 2011 at 7:09 PM, David Sankel <camior(a)gmail.com> wrote: > On Fri, Sep 16, 2011 at 6:30 AM, Thomas Heller > <thom.heller(a)googlemail.com>wrote: >> On Friday, September 16, 2011 06:17:00 AM David Sankel wrote: >> > On Fri, Sep 16, 2011 at 4:51 AM, Thomas Heller >> > <thom.heller(a)googlemail.com>wrote: >> > > On Thursday, September 15, 2011 12:31:50 PM David Sankel wrote: >> > <snip> >> > > <rant> >> > <snip> >> > > It should be noted though that phoenix users can get around >> > > > this somewhat by using _identifier syntax. >> > > > </rant> >> > > #include <boost/phoenix.hpp> >> > <snip> >> > auto flip = lambda(_a = _1)[bind(_a, _2, _1)]; >> > <snip> >> > > Thanks for your unqualified rant, David. >> > huh? >> >> Is this not what you were saying wasn't possible with phoenix? >> Having a De Brujin style syntax is perfectly possible in phoenix. It just >> hasn't been done yet cause, as you saw in my example, can be expressed by >> using phoenix local variables. > > Oh, my bad. When I said "_identifier syntax", I was referring to phoenix > local variables. I should have double-checked my phoenix vocab before I > wrote. > > Phoenix locals definitely help fill the coverage problem I referred to. I > don't know for sure, but I'd expect phoenix to cover all functions that can > be defined in lambda calculus. > > The reason I said that phoenix "somewhat" gets around the bind heritage > problems, which was obscure I admit, was because phoenix's use of > traditional bind syntax still leaves a semantic hole. Ok, misunderstanding on both sides, no offense intended. > If someone writes the following: > > template< typename F > > auto doSomething( F f ) -> decltype(...) > { > return bind( f, 15, _1) > } > > And then I call doSomething elsewhere like this, > > doSomething( bind( g, 12, _1, _2 ) ) > > , then the result is something most likely unexpected for the user who knows > what doSomething means (it returns a version of f that has 15 filled in as > its first argument (λx. λy. x(15,y))), but hasn't read its implementation. Now you got me interested, can you tell me how the DBB syntax solves this problem? Or is it just that your particular implementation solves it? FWIW, phoenix provides everything to introspect the given F and decide which action to take (wrap it into a lambda, "unlambda" it, leave it alone, etc.). One of the main design goals of the phoenix bind module was to be compatible to bind. So unlikely "bind" in its form will be changed. > Don't get me wrong, I think phoenix is an impressive feat. I'm just > advocating that we stop perpetuating the troubles caused by basing new > libraries on the traditional bind syntax. P.S.: I also like the DBB style syntax and think it would be a great addition, as JdG already mentioned, it is all implemented, what's missing is the frontend.

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C++ Standards
by Jarrad Waterloo 19 Sep '11

19 Sep '11

What is the status of and where can one go for current information on TR2, decimal type and modules? Are these dead? Is the C++ standards body taking a 3-10 years siesta before starting on any of these or the next standard? Has there been any recent discussion on "stack trace", reflection, dll(s), overloading -> and other operators. There was a list of items in which there was not enough time to consider for this standard but potential for the next standard. I ask these questions because I found about the link to the C++ standards from the main page of the boost website. However that link has been rather quiet.

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[fusion] boost::fusion::nil bug
by Jeroen Habraken 18 Sep '11

18 Sep '11

Hi, Clang 2.9 just pointed out what's probably an error in fusion in boost-trunk, the same one I ran into during the Conversion review yesterday it seems. Note that GCC doesn't complain even with -Wall -Wextra -pedantic. The error: In file included from fusion.cpp:1: In file included from boost-trunk/boost/fusion/include/vector.hpp:10: In file included from boost-trunk/boost/fusion/container/vector.hpp:11: In file included from boost-trunk/boost/fusion/container/vector/vector10.hpp:15: In file included from boost-trunk/boost/fusion/sequence/intrinsic/begin.hpp:17: In file included from boost-trunk/boost/fusion/sequence/intrinsic/detail/segmented_begin.hpp:11: In file included from boost-trunk/boost/fusion/iterator/segmented_iterator.hpp:13: In file included from boost-trunk/boost/fusion/container/list/cons.hpp:14: In file included from boost-trunk/boost/fusion/sequence/intrinsic/end.hpp:17: boost-trunk/boost/fusion/sequence/intrinsic/detail/segmented_end.hpp:33:70: error: invalid use of incomplete type 'fusion::nil' segmented_end_impl<Sequence, fusion::nil>::call(seq, fusion::nil())); ^~~~~~~~~~~~~ In file included from fusion.cpp:1: In file included from boost-trunk/boost/fusion/include/vector.hpp:10: In file included from boost-trunk/boost/fusion/container/vector.hpp:11: In file included from boost-trunk/boost/fusion/container/vector/vector10.hpp:15: In file included from boost-trunk/boost/fusion/sequence/intrinsic/begin.hpp:17: In file included from boost-trunk/boost/fusion/sequence/intrinsic/detail/segmented_begin.hpp:10: In file included from boost-trunk/boost/fusion/sequence/intrinsic/detail/segmented_begin_impl.hpp:11: boost-trunk/boost/fusion/container/list/cons_fwd.hpp:13:12: note: forward declaration of 'boost::fusion::nil' struct nil; ^ 1 error generated. The code to reproduce the error: #include <boost/fusion/include/vector.hpp> int main(int, char*[]) { return 0; } It seems nil is either only forward-declared or the include with the declaration is missing. Kind regards, Jeroen Habraken

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Is there interest in unit testing both passing and failing BOOST_MPL_ASSERTs?
by Ben Robinson 17 Sep '11

17 Sep '11

This submission would make it possible to write a complete set of unit tests for meta-programs, to test both the positive, compiling statements, and the negative, non-compiling statements. These tests will all compile, and the negative tests can throw an exception instead of failing to compile. After reading the recent interest submission from Abel Sinkovics, it occurred to me that it should be possible to modify the four existing BOOST_MPL_ASSERT_* macros to achieve this capability. This behavior would only be enabled if a specific compile flag was defined. Here is a sample code fragment which I have compiled and tested to work as described: // This definition shuts off the BOOST_MPL_ASSERT compile errors, and enables the run-time errors. #define BOOST_MPL_UNITTEST_ASSERTS defined BOOST_AUTO_TEST_CASE(ordinary_passing_test_cases) { BOOST_CHECK_NO_THROW( integers_only<char> passing0; ); BOOST_CHECK_NO_THROW( integers_only<short> passing1; ); BOOST_CHECK_NO_THROW( integers_only<int> passing2; ); BOOST_CHECK_NO_THROW( integers_only<unsigned int> passing3; ); } // These test cases now actually compile, but then throw at runtime, which is unit-testable. BOOST_AUTO_TEST_CASE(fantastic_failing_test_cases) { BOOST_CHECK_THROW( integers_only<float> failing0;, boost::mpl_assert_false); BOOST_CHECK_THROW( integers_only<double> failing1;, boost::mpl_assert_false ); } As you can see, existing code which uses the four BOOST_MPL_ASSERT_* macros, can now be unit tested, without modification, for both positive, and negative use cases. Is anybody interested in this capability, and/or my modifications to the single file boost/mpl/assert.hpp which have enabled this capability? Regards, Ben Robinson, Ph.D.

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Re: [boost] [Boost-docs] Getting CVS read/write access boost-sandbox.cvs.sourceforge.net
by Paul A. Bristow 16 Sep '11

16 Sep '11

> -----Original Message----- > From: boost-docs-bounces(a)lists.boost.org [mailto:boost-docs-bounces@lists.boost.org] On Behalf Of > Daniel James > Sent: Saturday, September 10, 2011 10:06 AM > To: Discussion of Boost Documentation > Subject: Re: [Boost-docs] Getting write access to boost-sandbox.cvs.sourceforge.net I would like to get read and write access to boost-sandbox.cvs.sourceforge.net (to put up some html docs)' I have tried to follow the instructions on Sourceforge.net and believe that I have stored a SSH key because I can login thus using PuTTY "login as: pbristow pbristow(a)boost-sandbox.cvs.sourceforge.net's password: Last login: Thu Sep 15 12:58:36 2011 from 53-133.radnet-kendal.kencomp.net Welcome to *.cvs.sourceforge.net This is a restricted Shell Account You cannot execute anything here." PuTTY Window says "Connection closed by remote host." If I repeat I get login as: pbristow pbristow(a)boost-sandbox.cvs.sourceforge.net's password: Last login: Thu Sep 15 12:59:41 2011 from 53-133.radnet-kendal.kencomp.net Welcome to *.cvs.sourceforge.net This is a restricted Shell Account You cannot execute anything here. whose changed last login date suggests that I am logging in OK - so I know my username and password OK. (or does the fact that I am asked for a password mean that my SSH authentication is wrong?) When I try to CVS checkout, (using a variety of module names (fetch modules list option is not available?) I get PuTTY Fatal error "Network error: connection timed out." cvs [checkout aborted] : end of file from server (consult above messages if any) - and there are no messages :-( Please can any Sourceforge CVS users advise? Thank you. Paul --- Paul A. Bristow, Prizet Farmhouse, Kendal LA8 8AB UK +44 1539 561830 07714330204 pbristow(a)hetp.u-net.com

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[chrono][stopwatches] Request for interest in NEW stopwatch/timer reporting facilities
by Vicente J. Botet Escriba 16 Sep '11

16 Sep '11

Hi, I has been reconsidering the reporting facilities of proposed Boost.Stopwatches. I have started to make some examples that make use Boost.Format to make the reports. Default reporting stopclock<> sw; prints the duration 29308.350 µs You can make a boost::format and pass it to the stopclock. void f1(long j) { boost::format fmt("%1%[%2%] f1(%3%) - Elapsed time: %4%"); fmt % __FILE__ % __LINE__ % j; stopclock< > sw(fmt); // burn some time } ../example/scoped_stopwatch_example.cpp[42] f1(1000000) - Elapsed time: 29834.769 µs ../example/scoped_stopwatch_example.cpp[51] void f2(long int) - Elapsed time: 0.979 µs You can change the precision, the output stream, the units and the unit text using a specific formatter. For example typedef elapsed_formatter<milli > formatter; formatter fmt("Elapsed time: %1%", std::cerr); fmt.set_duration_style(text); fmt.set_precision(6); stopclock<high_resolution_clock, formatter> sw(fmt); could print Elapsed time: 87.829801 milliseconds This formatter could be shared between several stopclocks (thread unsafe however). Even if the reporting facilities will not be completly 'localizable', I think that this interface goes one step towards in this direction. Before continuing the adaptation of the whole library I would like to hear some comments from you. Do you think this is an acceptable interface? What are the parameters that do you want to manage? procession, unit, short/long units, ... Best, Vicente

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[iostreams] #5904: Patch to suppress "unreachable code" warning from Visual Studio 2008/2010 (VC90/VC100)
by Sylvester-Bradley, Gareth 16 Sep '11

16 Sep '11

I've added ticket #5904 with a patch to suppress a warning in Boost.Iostreams. Please would someone apply this for Boost 1.48.0? Ticket URL: <https://svn.boost.org/trac/boost/ticket/5904> Many thanks, Gareth ************************************************************************ The information contained in this message or any of its attachments may be confidential and is intended for the exclusive use of the addressee(s). Any disclosure, reproduction, distribution or other dissemination or use of this communication is strictly prohibited without the express permission of the sender. The views expressed in this email are those of the individual and not necessarily those of Sony or Sony affiliated companies. Sony email is for business use only. This email and any response may be monitored by Sony to be in compliance with Sony's global policies and standards

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utility-container_gen in the sandbox
by Cromwell Enage 16 Sep '11

16 Sep '11

Hi, all. After a bit of a programming hiatus, I've managed to follow through on the container_gen discussion we had last May. I've created a branch in the sandbox called utility-container_gen that places the metafunction in Boost.Utility, changes detail::is_random_access to is_random_access_selector, provides an is_unique_associative_selector metafunction, and changes adjacency_list and parallel_edge_traits to use said utilities. Plus, there's Quickbook documentation. I've tested a few example programs in the BGL to make sure they still work, but I feel that's far from being thorough. No selectors for Boost.Intrusive have been implemented, yet. Feedback welcome! Cromwell D. Enage

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[Review] Boost.Endian by BEman Dawes starts today
by Joel Falcou 15 Sep '11

15 Sep '11

According to the schedule, the review of the Boost.Endian library by Beman Dawes starts today. =========== What is it? =========== Boost.Endian provides facilities to manipulate the byte ordering of integers. * The primary use case is binary I/O of integers for portable exchange with other systems, via either file or network transmission. * A secondary use case is to minimizing storage size via integers of sizes and/or alignments not supported by the built-in types. Integers 1, 2, 3, 4, 5, 6, 7, and 8 bytes in length are supported. * Two distinct approaches to byte ordering are provided. Each approach has a long history of successful use, and each approach has use cases where it is superior to the other approach. * The explicit approach provides explicit functions to reorder bytes. All four combinations of non-modifying or modifying, and unconditional or conditional, functions are provided. * The implicit approach provides integer classes that mimic the built-in integers, implicitly handling all byte reordering. =================== Getting the Library =================== Docs are available at http://boost.cowic.de/rc/endian/doc/index.html A zip file is available at http://boost.cowic.de/rc/endian/endian-rc1.zip INSTALL instructions at http://boost.cowic.de/rc/endian/INSTALL Alternately, the whole library can be checked out of the sandbox: svn co http://svn.boost.org/svn/boost/sandbox/endian endian ================ Writing a Review ================ The reviews and all comments should be submitted to the developers list, and the email should have "[Endian] Review" at the beginning of the subject line to make sure it's not missed. Please explicitly state in your review whether the library should be accepted. The general review checklist: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And finally, every review should answer this question: - Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion.

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