October 2010 - Boost - lists.preview.boost.org

[review result] mini-review of update to Boost.Assign
by Thorsten Ottosen 18 Oct '10

18 Oct '10

Dear all, Here follows the result of the result of Erwann Rogard's update to Boost.Assign: **************************** The update is not accepted **************************** This is not because the new functioanlity/interface was not seen as an improvement, but because Erwann has chosen to implement a full replacement (or Assign v2) based on the feedback he got during the review. The feedback meant that the new "update" would be much larger than what was present in the mini-review, and the new library should therefore be subject of its own full review. I would like to thank Erwann for his hard work so far, and hope he submits a Boost.Assign v2 in the near future. I would also like to thank the following people who participated in the mini-review: Christopher Jefferson Diederick C. Niehorster John Bytheway kind regards Thorsten, review manager

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[pool] detail/mutex.hpp may include windows.h and pollute namespace with windows definitions.
by Paul Blampspied 18 Oct '10

18 Oct '10

I have been making an effort to write Windows independent code. In particular I avoid including windows.h in any of my headers (some implementation files include it). I have had a problem using Boost/pool as the mutex header includes windows.h (causing nameclashes with some of my existing code, which has always relied on the absence of windows.h). Possible inclusion of windows.h is documented in the section on mutex. My question is 'Is it really necessary or desirable ?'. Is there a Boost policy on the inclusion of OS specific headers which create a large number of declarations in the global namespace ? The section which uses windows.h is: #ifdef BOOST_WINDOWS class win32_mutex { private: ::CRITICAL_SECTION mtx; win32_mutex(const win32_mutex &); void operator=(const win32_mutex &); public: win32_mutex() { ::InitializeCriticalSection(&mtx); } ~win32_mutex() { ::DeleteCriticalSection(&mtx); } void lock() { ::EnterCriticalSection(&mtx); } void unlock() { ::LeaveCriticalSection(&mtx); } }; #endif // defined(BOOST_WINDOWS) I believe that the appropriate declarations of InitializeCriticalSection, DeleteCriticalSection, EnterCriticalSection, LeaveCriticalSection could be provided explicitly in this file and hence avoid including windows.h and the subsequent namespace 'pollution'. An alternative of using a Boost multithreading library is suggested in the documentation. This would be ideal, but my proposal would solve problem now, relatively effortlessly. PS. I did a quick edit and got it to work (at least on Vista). The change to the if-endif block is shown below. It could be done much better. # ifdef BOOST_WINDOWS //#include <windows.h> typedef char CRITICAL_SECTION[24]; //24 is sizeof(CRITICAL_SECTION) ! typedef CRITICAL_SECTION *LPCRITICAL_SECTION; #define WINAPI __stdcall extern void WINAPI InitializeCriticalSection( __out LPCRITICAL_SECTION lpCriticalSection ); extern void WINAPI DeleteCriticalSection( __inout LPCRITICAL_SECTION lpCriticalSection ); extern void WINAPI EnterCriticalSection( __inout LPCRITICAL_SECTION lpCriticalSection ); extern void WINAPI EnterCriticalSection( __inout LPCRITICAL_SECTION lpCriticalSection ); void WINAPI LeaveCriticalSection( __inout LPCRITICAL_SECTION lpCriticalSection ); # endif many regards, Paul

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[property_tree] Copy constructor and assignment operator in xml_writer_settings class
by Mateusz Loskot 18 Oct '10

18 Oct '10

Hi, What is recommended or required policy regarding copy operations for types which consist of const data members, within Boost? I'm having problem with understanding why the xml_writer_settings class do not have the copying operations disabled. Perhaps it should be patched? Quick chat on the #boost IRC channel confirms it could be improved. I'm looking forward comments. [1] https://svn.boost.org/trac/boost/browser/trunk/boost/property_tree/detail/x… Best regards, -- Mateusz Loskot, http://mateusz.loskot.net Charter Member of OSGeo, http://osgeo.org Member of ACCU, http://accu.org

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is_convertible_basic_impl and OpenMP - compile error
by Remi 18 Oct '10

18 Oct '10

Hi, I'd like to report nasty behaviour of boost when used inside OpenMP loops. In the following example compile error is generated under Visual 2008, if "default(none)" is used for OpenMP variable data sharing attribute clauses (which is the recommended choice). #define BOOST_ALL_NO_LIB 1 #include <boost/graph/adjacency_list.hpp> #include <omp.h> int main(int argc, char* argv[]) { typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS> GraphType; typedef GraphType::adjacency_iterator GraphAdjacencyIterator; const unsigned int vertex_count( 20 ); typedef std::pair<int, int> EdgeType; std::vector<EdgeType> edges; const GraphType graph( edges.begin(), edges.end(), vertex_count, edges.size() ); int i( 0 ); #pragma omp parallel for schedule(static, 1) default(none) private(i) shared(vertex_count, graph) for ( i = 0; i < vertex_count; ++i ) { const std::pair<GraphAdjacencyIterator, GraphAdjacencyIterator> adjacent ( boost::adjacent_vertices(i, graph) ); } return 0; } "\boost\boost/type_traits/is_convertible.hpp(263) : error C3052: '_m_from' : variable doesn't appear in a data-sharing clause under a default(none) clause"

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Version information for Boost library
by Edward Diener 18 Oct '10

18 Oct '10

Does Boost have any policy regarding the way version information should be attached to a library ?

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Does boost support ccache?
by Alexander Churanov 18 Oct '10

18 Oct '10

Folks, I've encountered an issue: boost libraries fail to build under ccache. The questions are: 1) Are boost libraries and ccache compatible? 2) If not, should I file a new bug? One of users contacted me and reported failure to build boost libraries version 1.43 on FreeBSD 7.3 (GCC 4.2.1). There were, however, no failures on the FreeBSD ports build cluster. Quick comparison of logs revealed that build cluster does not use ccache - compilation cache tool for C++ and other languages. Removing ccache from the toolchain fixed the issue, so it is an acceptable workaround. The logs are available here: http://alexanderchuranov.com/boost-issues/ccahe-freebsd-7-boost-1.43/ The original filed issue is here: http://www.freebsd.org/cgi/query-pr.cgi?pr=ports/151454 The patches for boost-libs port are here: http://www.freebsd.org/cgi/cvsweb.cgi/ports/devel/boost-libs/files/ Alexander Churanov, maintainer of devel/boost-* ports for FreeBSD

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Question about commercial software and boost license
by marc_elias＠terra.es 18 Oct '10

18 Oct '10

Hi, I'm working in a company that want to use boost libraries to a commercial software. I have a pair of questions: 1. Is it possible to distribute under the boost license a commercial software (so the source code won't be exposed) programmed with static boost libraries? 2. And with linked libraries to an executable? Thanks in advance! MARC

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[1.45] Release notes
by Daniel James 18 Oct '10

18 Oct '10

Hello all, Once more, it's time to prepare the release notes. If you want to add to them yourself, you can edit the source files in subversion here: http://svn.boost.org/svn/boost/website/public_html/beta/feed/history/ Or if you prefer, you can email me the details and I'll add it for you. Because the relevant web pages are now served as static files rather than as dynamic php pages, rebuilding the feeds won't change the web site. The process for generating the pages was a quick hack and is pretty horrible, so it's probably best if you leave that to me for this release. I'm writing a new python script to do all of this (the only requirement will be a quickbook executable), so hopefully it'll be a lot easier next time. Daniel

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[network] cpp-netlib 0.7 ready to be released
by Dean Michael Berris 18 Oct '10

18 Oct '10

Hi Guys, I just wanted to give everyone interested a heads up on the progress being made on the cpp-netlib project (which I'm working on full-time at the moment). Basically: * There's now an asynchronous/active HTTP client implementation that returns response objects that encapsulate futures. This uses the Boost.Asio asynchronous socket interfaces to implement reads/writes on the active object. * The documentation has been moved from Quickbook to ReStructuredText and generated with Sphinx (and they look really nice if I may say so myself: http://mikhailberis.github.com/cpp-netlib/) * The message concept has been fleshed out and now requires external modifiers. * Requirement for OpenSSL has been dropped, now by default doesn't support HTTPS unless specified. This impending 0.7 release also uses more template metaprogramming tools from Boost.MPL to implement the tag dispatch mechanism to modify behaviors of the classes based on these tags. Policies were introduced and are chosen depending on the characteristics of the tags provided. Development on 0.8 shall include: * A more feature-complete HTTP server template that supports a worker thread pool where handlers get invoked, and where handlers can write data to the connection asynchronously. * A streaming HTTP client interface to support passing a raw stream associated with a socket to a handler function or as part of the response object returned. * A preliminary XMPP client implementation. * The beginnings of a web service framework on top of the HTTP server to allow for a more web-framework like feel, similar to how web frameworks like Tornado Web (http://tornadoweb.org/) Target release of 0.8 will be the first week of November. The development of cpp-netlib targets an end-of-year submission to the Boost Library, and hopefully those interested in the project can go ahead and try it out now so that I and the other developers can work on feature requests before that time -- and so that early evaluations can guide the direction of the development before December. Thanks everyone and I look forward to hearing from you! Note: You can find the documentation for cpp-netlib (which I presented at BoostCon 2010) at http://mikhailberis.github.com/cpp-netlib -- Dean Michael Berris deanberris.com

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boost.foreach overhead
by Christopher Lux 18 Oct '10

18 Oct '10

On 10/9/2010 John Carmack of id Software wrote on his Twitter account: “@ID_AA_Carmack: It took 69 single steps to get past a BOOST_FOREACH() statement. Madness.” This made me think again about the overhead introduced with boost foreach. Is the overhead really this large as he makes it sound? Are there heuristics to when to use foreach according to the expected iteration counts? Regards -chris -- Christopher Lux | | Bauhaus-Universität Weimar | Faculty of Media - Virtual Reality Systems Group | Tel. +49 (0) 3643 - 58 3734

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[network] cpp-netlib 0.7 released!
by Dean Michael Berris 18 Oct '10

18 Oct '10

Hi Everyone! So, I've been busy the past few hours doing a final push to get 0.7 out the door so that starting tomorrow I can start working on the 0.8 branch to improve the server-side HTTP implementation. Now, it's official, 0.7 is out the door and is ready for prime-time. ;-) In case you'd like to try it out, it's header only and you can download the 0.7 release from: http://github.com/cpp-netlib/cpp-netlib/downloads This has numerous improvements and enhancements over the 0.6 version, and has a more robust definition of the concepts included in the library. Now anybody can start extending cpp-netlib with their own protocol implementations using the common message type. If you want your work to integrate cleanly with the project, you can go ahead and fork my repository (as the project's "benevolent dictator for life") and submit pull requests in case you want to get your implementation/fixes/extensions into the main library distribution. As earlier stated, 0.8 will be a server-side focused development effort which will include a lot of cool things not just an improved HTTP server interface. If you'd like to discuss the effort or join the development, please feel free to send email to either the Boost Developer mailing list (because this library will be submitted for review and inclusion in Boost around December 2010) or the cpp-netlib developers mailing list. Thanks to everyone who's expressed interest, and those who have offered suggestions on the improvements to be made to the library. I hope everyone had a great weekend too! -- Dean Michael Berris deanberris.com

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[OT] Calling Overmind
by John Phillips 18 Oct '10

18 Oct '10

Overmind, Would you please either contact me (John Phillips), or Ron Garcia off list? Thanks. John

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3rd- party reliance for upcoming boost.GIL.IO library
by Christian Henning 17 Oct '10

17 Oct '10

Hi there, We are going to submit the Boost.GIL.IO extension for review and the package relies on 3rd-party libraries; can anyone suggest minimum solution for finding those libraries which would be usable for reviewers to build and run tests/examples? The library is pretty much ready for review and can be found here: http://gil-contributions.googlecode.com/files/boost_review.zip or via SVN, here: http://code.google.com/p/gil-contributions/source/browse/#svn/trunk/gil_2 Thanks, Christian

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[unordered] error: template argument required for ‘struct set_extractor’
by Mateusz Loskot 17 Oct '10

17 Oct '10

Hi, I'm experiencing strange problem with unordered_map.hpp file. I'm using Boost 1.44 with GCC 4.2.1 from XCode on Mac OS X. Compiling simple test: $ cat foo.cpp #include <boost/unordered_map.hpp> int main() {} $ g++ -o foo.o foo.cpp In file included from /usr/local/include/boost/unordered/detail/equivalent.hpp:11, from /usr/local/include/boost/unordered/unordered_map.hpp:19, from /usr/local/include/boost/unordered_map.hpp:16, from foo.cpp:1: /usr/local/include/boost/unordered/detail/extract_key.hpp:31: error: template argument required for ‘struct set_extractor’ /usr/local/include/boost/unordered/detail/extract_key.hpp:77: error: template argument required for ‘struct map_extractor’ I've looked at the preprocessed file and there is something that disturbs me - templates of set_extractor and map_extractor are getting "changed". Comparing preprocessed file against source from boost/unordered/detail/extract_key.hpp I see 1) set_extractor a) original code template <class ValueType> struct set_extractor { typedef ValueType value_type; typedef ValueType key_type; b) preprocessed output struct set_extractor { template <class ValueType> struct apply { typedef ValueType value_type; typedef ValueType key_type; 2) map_extractor a) original code template <class Key, class ValueType> struct map_extractor { typedef ValueType value_type; typedef BOOST_DEDUCED_TYPENAME boost::remove_const<Key>::type key_type; b) preprocessed output struct map_extractor { template <class ValueType> struct apply { typedef ValueType value_type; typedef typename remove_const<typename ValueType::first_type>::type key_type; As you can see, the set_exctractor and map_exctractor templates have lost template parameters declarations and some extra nested struct has been generated: template <class ValueType> struct apply Folks on #boost at IRC suggested it may be caused by MPL magic. I haven't noticed any such problem with GCC 4.4 on Linux with Boost 1.43 There has been similar issue reported, but the problem was ALLOC macro defined by RICE library, what rather is not my case: http://lists.boost.org/boost-users/2010/05/59340.php Does anyone have an idea what's happening? Best regards, -- Mateusz Loskot, http://mateusz.loskot.net Charter Member of OSGeo, http://osgeo.org Member of ACCU, http://accu.org

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[CfP] 5th Annual BoostCon, Aspen (CO, USA), May 15-20, 2011
by Hartmut Kaiser 16 Oct '10

16 Oct '10

Please distribute. ------------------ 5TH ANNUAL BOOST CONFERENCE 2011 Aspen CO, USA, May 15 - 20, 2011, www.boostcon.com CALL FOR PARTICIPATION We invite you to submit session proposals to the 5th Annual Boost Conference: BoostCon 2011 (Aspen CO, USA, May 15 - 20, 2011). Traditionally the main face-to-face event for all things Boost (www.boost.org) BoostCon 2011 will present leading speakers from the whole C++ community. >From using the Boost libraries to writing and maintaining them, from evangelizing to deploying Boost within your organization, from infrastructure and process to vision and mission, and the new C++ Standard, BoostCon brings together the sessions, the colleagues, and the inspiration to support your work with C++ and Boost in particular for the next year. To reflect the breadth of the Boost community, the conference includes sessions aimed at three constituencies: Boost end-users, hard-core Boost library and tool developers, and academics focusing on researcher. The program fosters interaction and engagement within and across those groups, with an emphasis on hands-on, participatory sessions. SESSION TOPICS Topics of interest include, but are not restricted to, the following: * General tutorial sessions introducing one or more Boost libraries * In-depth sessions on using specific Boost libraries * Case studies on using Boost * Experts panels * Advanced sessions on implementation techniques used within Boost libraries * C++0x and how it changes life for users and library writers * Development workshops to extend or enhance existing Boost libraries * Workshops on design process * Infrastructure workshops such as Build tools, Website, Testing * Concepts and Generic Programming * Hardware and infrastructure presentations focused on how libraries can make better use of the technology * Software development tools and their application to C++ and or Boost * Other topics likely to be of great interest to Boost users and developers Interactive and collaborative sessions are encouraged, as this is the nature of both the on-line Boost community and the style of learning and participation that has proven most successful at such events. Sessions can be tutorial based, with an emphasis on interaction and participant involvement, or workshop based, whether hands-on programming or paper-based, discussion-driven collaborative work. SESSION FORMATS Presentations ------------- Presentations focus on a practitioner's ideas and experience with anything relevant to Boost and Boost users. Panels ------------- Panels feature three or four people presenting their ideas and experiences relating to Boost's relevant, controversial, emerging, or unresolved issues. Panels may be conducted in several ways, such as comparative, analytic, or historic. Tutorials ------------- Tutorials are sessions at which instructors teach conference participants specific Boost-relevant skills. Workshops ------------- Workshops provide an active arena for advancements in Boost-relevant topics. Workshops provide the opportunity for experienced practitioners to develop new ideas about a topic of common interest and experience. Author's Corner Presentations These were introduced at BoostCon 2008, and were a great success. They are short (30 minute) sessions, focusing on tips on usage and design. In addition, we're looking to uncover the hidden design gems in Boost libraries. Tool Vendors Presentations We actively encourage tool vendors and ISP's to submit proposals for a special Tool Vendors Session Track aimed at products related to Boost and C++ (compilers, libraries, tools, etc.). Other formats may also be of interest. Don't hold back a proposal just because it doesn't fit into a pigeonhole. SUBMITTING A PROPOSAL Standard Sessions are 90 minutes. You may submit a proposal for fractions or multiples of 90-minutes. Fractional proposals will be grouped into 90 minute sessions covering related topics. Longer sessions, such as tutorials and classes, will be assigned 90 minute, three hour (i.e. half day), or six hour (i.e. full day) time slots. Please include: * The working title. * Type of session: presentation, panel, tutorial, workshop, authors corner, vendor track, other. * A paragraph or two describing the topic covered, suitable for the conference web site. * Proposed length: 10-20 minute short talks, 45 minutes, 90 minutes, half day, full day. * Alternate lengths, if you are willing to make adjustments: 10-20 minute short-talks, 45 minutes, 90 minutes, half-day, full day. * Audience: users, developers, both. * Level: basic, intermediate, advanced. * A biography, suitable for the conference web site. * Your contact information (will not be made public). SUBMISSION DETAILS All submissions have to be done through the EasyChair conference management system: http://www.easychair.org/conferences/?conf=boostcon2011. If you have not already registered at EasyChair, you will need to do so in order to submit your proposal. All submissions will go through a peer review process. Authors are invited (but are not required) to submit PDF versions of full papers of up to 10 pages in ACM conference proceedings format (see http://www.acm.org/sigs/publications/proceedings-templates) The full papers are not required unless you want them published in the proceedings. All accepted proposals will be made available in the Association for Computing Machinery (ACM) Digital Library (approval pending). Best papers, after further reviews, will be considered to be book chapters or journal articles in a renowned journal. The session materials go on the BoostCon website and will be available to attendees. For general information on the BoostCon 2011 paper submission or the scope of technical papers solicited, please refer to the conference website at www.boostcon.com. For any other questions about the submission process or paper format, please contact the Program Committee at boostcon2011(a)easychair.com. If you have any technical problems with EasyChair, please contact EasyChair for help. Note: Presenters must agree to grant a non-exclusive perpetual license to publish submitted materials, either electronically or in print, in any media related to BoostCon. IMPORTANT DATES Proposal submissions due: December 10th, 2011. Proposals decisions sent (tentative program available): January 17th, 2011. Fully scheduled program available: February 7th, 2011. Session materials due: April 15th, 2011. Hartmut Kaiser, email: hartmut.kaiser(a)gmail.com (Program Committee Chair) David Abrahams, email: dave(a)boostpro.com (Conference Chair) On behalf of the conference organizers

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[Pointer Container] Modification of pointer containers to allow const elements
by Gerardo Hernández 16 Oct '10

16 Oct '10

The following code snippet: boost::ptr_vector<const int> v; v.push_back(new int); produces the following error message (Visual C++ 9, boost 1.44): boost\ptr_container\ptr_sequence_adapter.hpp(249) : error C2664: 'std::vector<_Ty,_Ax>::push_back' : cannot convert parameter 1 from 'const int *' to 'void *const &' The problem is that the underlying type of boost::ptr_vector<T> is always vector<void*>, no matter T is const. This prevents push_back() method from maintaining const-correctness. The rest of the pointer containers contain an equivalent problem and this has been a TODO for some time. According to Thorsten Ottosen (library author) ( https://svn.boost.org/trac/boost/ticket/3832 ): "The fix is basically just some meta-functions taking into account that T might be const, and if so, instantiate container<const void*> instead of container<void*>" To the vector problem, this means that the underlying type should be: vector<typename boost::mpl::if_<boost::is_const<T>, const void*, void*> > I have sucessfully applied this approach to the pointer containers that mimic STL counterparts (see attachment) and I guess it should work for the others. I need feedback on whether this is a completely correct approach and if so I would like to contribute a modification. Gerardo.

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[optional] memory use for optional refs and ptrs
by Rutger ter Borg 15 Oct '10

15 Oct '10

Hello, I'm looking into boost::optional<> as a replacement for some of my code which has to deal with optional values. However, it seems that cases which are usually space-efficient optionals (e.g., ptrs in the form of a null-ptr) do not have template specializations. In other words, boost optional templates store a bool and the memory footprint of its template parameter, regardless of type. I.e., optional references and pointers take their space plus the space of an extra bool. Is there a reason for this? Thanks, Rutger

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New Boostcon sessions uploaded
by Marshall Clow 14 Oct '10

14 Oct '10

Michael Caisse: Using Spirit V2: Qi and Karma http://blip.tv/dashboard/episode/4162161 Stephan T. Lavavej: Data Structure Visualizers in Visual Studio 2010 http://blip.tv/dashboard/episode/4162044 Matt Calabrese, Zachary Laine: Instantiations Must Go! http://blip.tv/dashboard/episode/4161957 Jeremy Siek: Generic Programming And the Boost Graph Library http://blip.tv/dashboard/episode/4161923 More to come (I'm shooting for one session every other day)..... -- Marshall

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C++0x trailing return type
by Matt Calabrese 14 Oct '10

14 Oct '10

I'd like to introduce a macro to Boost.Config called BOOST_NO_TRAILING_RETURN_TYPE for checking if a compiler supports 0x trailing return types I.E. auto foo() -> void; Is there general agreement that this is an appropriate name for the macro? Now for a small rant -- in a recent thread, I talked about introducing a simple BOOST_AUTO_FUNCTION macro which I'll request review for shortly, as a way to simulate automatic return type deduction when writing functions and function templates. In experimenting with the macro, I have hit what I believe is either a bug in GCC or what I would consider a huge failing of C++0x trailing return types (someone please aid me in figuring this out). One of the main reasons why trailing return types are helpful is that the arguments to the function or function template you are writing are able to be refered to when forming the return type, however, when dealing with non-static member functions, it seems to me that you are not able to refer to "this" or non-static members. This greatly reduces the usefulness of trailing return types, as all of the reasons why you would want to refer to the parameters apply with the same rationale to why you would want to refer to members and "this". I've skimmed through the standard and see no explicit mention of or examples of using trailing return types in this manner. Perhaps someone here can help parse the standard-ese to clarify? I'd hope that you could refer to non-static members, but I see no evidence of that. One example of why this is frustrating in practice can be seen in the following hypothetical code for a Boost.Variant-style template with an "emplace" member-function that is intended to construct an object in-place similar to the emplace family of member functions of C++0x containers: http://codepaste.net/u5nfis Here, the trailing return type is used almost exclusively for extended SFINAE, though you often wish to refer to members in other cases as well where SFINAE isn't of any concern. The overall goal with the implementation of emplace being as such is to attempt to force substitution to fail if any of the following cases were true: if "Type" does not have a constructor taking the forwarded arguments if "Type" is not one of the types that is able to be stored in the template and possibly even something else I've missed (...which is a good thing...) Essentially we want substitution to fail if the instantiation of the body would fail, giving a very basic equivalent to low-level, syntax-only, automatic concept-checking. The benefit of this speaks for itself. Here, at least in my opinion, such code is very concise, very powerful, and surprisingly readable. Without such functionality of trailing return types we can only do marginally better than we've been doing for the past 10 years. So if someone could help me determine whether or not what I'm trying to do is standard I'd be grateful, and if such functionality is not standard, is it too late for it to be added? It seems to me that the benefits with respect to library development here are too great for a community like Boost to ignore, though I myself am not familiar enough with the standardization process to make an impact. Thanks. It appears this rant has overshadowed the original question, though please don't forget to respond. -- -Matt Calabrese

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Schedule on www.boost.org
by Rene Eng 14 Oct '10

14 Oct '10

Hi all Following the release schedule on www.boost.org, preparations for the release 1.45 are already underway. But I have not read anything here on the mailing list yet. Could somebody please either confirm the intention to keep those release dates, or otherwise adjust the dates in the release schedule? Thank you very much in advance René Eng -- “Dubito ergo cogito; cogito ergo sum. (I doubt, therefore I think; I think therefore I am)” René Descartes

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[geometry]
by Paul Blampspied 13 Oct '10

13 Oct '10

I have been looking at the advance version of [boost][geometry]. I think it is very useful and very well worked out. I have a question. Does [geometry] support the idea of a frame of reference ? I believe not, but it may be that I have missed some way of achieving this. By reference frame I mean that some points are not directly comparable if they are in different frames of reference. This is distinct from different coordinate systems (I think). For example we could have two geographic coordinate systems, one referring to lat./long. on earth and another to Mars. the points on these two reference frames should not be comparable and should give a compile error. Can this be done in [geometry] ? More interestingly we could use two distinct reference frames for convenience, even though there is a known relation between them. It would be nice if point conversions between the two frames could be carried out (possibly implicitly). For example, I would like to do something like this: ShiftAndRotateTransform<EgocentricFrame, WorldFrame> EgoFrame_WorldFrame_Transform(10, 20, 90); //Shift by [10,20] and rotate 90deg. WorldFrame Test() { WorldFrame p1 = EgoFrame(0,0); EgocentricFrame p2 = WorldFrame(p1); return p2; //IMPORTANT - p2 is implicitly transformed to WorldFrame when returned from Test function. } I have managed to implement a very simple scheme which allows this to compile and work successfully, but I am not completely satisfied with my homebrew scheme. In particular, I am forced to declare the WorldFrame and EgoFrame classes and provide all the constructors for them. It is necessary to explicitly provide constructors for all the reference frames which can be converted - implying that this is known at the time the class is written. It is more flexible to use overloaded functions, because these can be added as required e.g. //The second argument is the output point which is modified. ChangeReferenceFrame(WorldFrame &p1, EgocentricFrame &p2); ChangeReferenceFrame(EgocentricFrame &p1, WorldFrame &p2); ChangeReferenceFrame(EgocentricFrame &p1, SomeNewFrameType &p2); However the syntactic convenience and possibility of implicit conversion is lost. I wonder if some sleight of template magic could allow the extensibility of the second approach with the usability of the first. The starting point would be to allow a class representing the transform between the two frames of reference to be declared. This should attempt to define as much of the machinery as possible. It seems to me that these facilities have no impact on the existing design of [geometry], but concern an extension to allow reference frames to be defined and related.

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License question
by David Bellot 13 Oct '10

13 Oct '10

Hi guys, I'm working on a new library for some specific A.I and machine learning problems and I will release it as a Free Software of course. However, I wonder if you guys can enlighten me regarding license. This library will be template-based for some parts and compiled for other parts. I don't want to restrict users in what they're doing with the library, I mean they can use it for open-source or closed-source products. However, I want to decently protect my work and because it's template-based and can be used in commercial products, I don't want someone to do closed-source fork of it and all those kind of things... I selected to candidates: Boost and LGPL. So question: - do I have to use a Boost license or a LGPL license ? - and why not using GPL directly or is it too restrictive ? Thanks for your help, David (also boost::ublas maintainer when not doing statistics ;-) ) -- David Bellot, PhD david.bellot(a)gmail.com http://david.bellot.free.fr

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Re: [boost] [function] function wrapping with no exception safety guarantee
by Dave Abrahams 12 Oct '10

12 Oct '10

On Tuesday, October 12, 2010, Emil Dotchevski <emil(a)revergestudios.com> wrote: > On Tue, Oct 12, 2010 at 4:04 PM, Daniel Walker > <daniel.j.walker(a)gmail.com> wrote: >> Formally, boost::function invocation has strong exception safety if >> invoking the target function has strong exception safety. > > This makes no sense at all. Invoking boost::function always has strong > exception safety guarantee. In no way it can make the state of the > boost::function object inconsistent, because it does not modify its > state. Sounds like you're talking about the basic guarantee here. > _____________________________________________ -- Dave Abrahams BoostPro Computing http://www.boostpro.com

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Nightly tests failed with filesystem problem
by Belcourt, Kenneth 12 Oct '10

12 Oct '10

Hi, Tests failed last night for a problem with v3/src/operations.cpp. gcc.compile.c++ /scratch/boost/boost/bin.v2/libs/filesystem/build/ gcc-4.1.2/release/link-static/v3/src/operations.o "g++" -ftemplate-depth-128 -O3 -finline-functions -Wno-inline -Wall - DBOOST_ALL_NO_LIB=1 -DBOOST_SYSTEM_STATIC_LINK=1 -DNDEBUG -I"/scratch/ boost/ boost" -c -o "/scratch/boost/boost/bin.v2/libs/filesystem/build/ gcc-4.1.2/release/link-static/v3/src/operations.o" "/scratch/boost/ boost/libs/filesystem/v3/src/operations.cpp" /scratch/boost/boost/libs/filesystem/v3/src/operations.cpp: In function ‘boost::filesystem3::file_type<unnamed>::query_file_type(const boost::filesystem3::path&, boost::system::error_code*)’: /scratch/boost/boost/libs/filesystem/v3/src/operations.cpp:467: error: no matching function for call to ‘symlink_status(const boost::filesystem3::path&, boost::system::error_code*&)’ /scratch/boost/boost/boost/filesystem/v3/operations.hpp:209: note: candidates are: boost::filesystem3::file_status boost::filesystem3::symlink_status(const boost::filesystem3::path&) /scratch/boost/boost/boost/filesystem/v3/operations.hpp:211: note: boost::filesystem3::file_status boost::filesystem3::symlink_status(const boost::filesystem3::path&, boost::system::error_code&) Can someone please take a look? Thanks. -- Noel

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[proto] Writing a transform to get at an inner constant of a transform result type
by Sebastian Redl 12 Oct '10

12 Oct '10

Hi, The subject is probably very confusing. I'm back to playing with a proto-based library for vector types. I have a basic underlying vector template, simd_impl: template <typename T> struct simd_impl { static const size_t size = VECTOR_BYTES / sizeof(T); // data }; And I have a grammar, Simd struct Simd : proto::or_< SimdLiteral, SimdUnary, SimdVectorBinary, SimdMixedBinary > {}; where SimdLiteral is an enumeration of proto::terminal<simd_impl<T>> where T are various underlying types, SimdUnary are unary operations, SimdVectorBinary are combinations of two vectors, and SimdMixedBinary are combinations of vectors with scalars. SimdVectorBinary is currently defined approximately like this: struct SimdVectorBinary : proto::or_< proto::when<proto::plus<Simd, Simd>, exec::simd_plus(Simd(_left), Simd(_right))>, // more operators here > {}; Now I want to validate, in the grammar, that you only add two vectors of the same arity together. That is, I'm fine with adding simd_impl<long> and simd_impl<int> together if they have the same size, because both have the same number of elements, but adding simd_impl<short> and simd_impl<int> together doesn't work, as one has twice the number of elements as the other. But I can't figure out how to write a grammar that validates this. I've started something like this: struct VSizeMatches : proto::if_<mpl::equal_to<Arity(proto::_left), Arity(proto::right)>()> {}; but I think that's wrong, and I can't figure out how to write Arity anyway. Basically, I have to find the simd_impl<T> type that the result of my Simd transform has and then access the size member. But I'm kinda afraid that this will get me into a world of trouble with prematurely instantiated templates. Any advice? Sebastian

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