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Re: [boost] [Spirit-general] construe_cast, call for interest and feedback
by Jeroen Habraken 07 Oct '10

07 Oct '10

On 7 October 2010 22:43, Aaron Graham <aaron(a)aarongraham.com> wrote: > I'm excited about construe_cast. I always liked the flexibility of > lexical_cast, but tend not to use it as much as I could because of its > performance relative to other mechanisms. > Does gcc still convert "23" at compile time if you disable builtins? > (-fno-builtin) > #include <boost/construe_cast.hpp> int main(int, char**) { return boost::construe_cast<int>("23"); } compiled using gcc 4.5.1, g++-4.5 test.cpp -o test -O3 -I . -I ../library/boost-trunk/ -fno-builtin will generate the following code: Dump of assembler code for function main: 0x0000000100000e20 <main+0>: push %rbp 0x0000000100000e21 <main+1>: mov $0x17,%eax 0x0000000100000e26 <main+6>: mov %rsp,%rbp 0x0000000100000e29 <main+9>: leaveq 0x0000000100000e2a <main+10>: retq 0x0000000100000e2b <main+11>: nopl 0x0(%rax,%rax,1) thus as you can see, it's still able to perform the optimization. Jeroen

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[Review] Formal Review of Proposed Boost.Ratio Library Starts TODAY
by Anthony Williams 07 Oct '10

07 Oct '10

Hi everyone, The review of Vicente Botet' Ratio library starts TODAY (October 2nd) and lasts until October 11th, 2010, unless an extension occurs. What is it? ======== Portable implementation of the C++0x Standard Library's compile-time rational arithmetic working on C++03 and C++0x compilers. See the current C++0x working draft at http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3126.pdf Boost.Ratio provides: * A class template, ratio, for specifying compile time rational constants such as 1/3 of a nanosecond or the number of inches per meter. ratio represents a compile time ratio of compile time constants with support for compile time arithmetic with overflow and division by zero protection * It provides a textual representation of boost::ratio<N, D> in the form of a std::basic_string. Other types such as boost::duration can use these strings to aid in their I/O. This library is header-only and is designed to be generic and useful in a lot of areas of math and numerics C++ programming, in particular it is absolutely needed for the proposed Boost.Chrono and Boost.Stopwatches libraries which are currently in the review queue. Getting the library ============= The latest version of this library may be downloaded from vault: http://www.boostpro.com/vault/index.php?action=downloadfile&filename=ratio.… SVN: http://svn.boost.org/svn/boost/sandbox/chrono (directories boost/ratio and libs/ratio) and the docs may be viewed here html: http://svn.boost.org/svn/boost/sandbox/chrono/libs/ratio/doc/html/index.html pdf: http://svn.boost.org/svn/boost/sandbox/chrono/libs/ratio/doc/ratio.pdf You can get all these information also (which should avoid some long links) from http://svn.boost.org/trac/boost/wiki/LibrariesUnderConstruction#Boost.Ratio It is worth noting that the tests included in the zip file are relatively sparse. Vicente has an extensive suite of tests licensed under the LLVM license. He has posted a message on the Boost Developers mailing list regarding the license requirements for tests (See http://thread.gmane.org/gmane.comp.lib.boost.devel/208978) and is awaiting the outcome of that discussion before making the tests available. Writing a review ================ If you feel this is an interesting library, then please submit your review to the developer list (preferably), or to the review manager. Here are some questions you might want to answer in your review: - 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. Anthony Review Manager for the proposed Boost.Ratio library -- Author of C++ Concurrency in Action http://www.stdthread.co.uk/book/ just::thread C++0x thread library http://www.stdthread.co.uk Just Software Solutions Ltd http://www.justsoftwaresolutions.co.uk 15 Carrallack Mews, St Just, Cornwall, TR19 7UL, UK. Company No. 5478976

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[Concept Check] ContiguousIterator
by joel falcou 07 Oct '10

07 Oct '10

Using BCC, s there any way to refine RandomAccessIterator so the cocnept captures the fact that the address of two consecutive value iterated over are contiguous in memory ? I can't get any proper expression to check for this in a proper way.

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[xpressive] Support for multi-capture and balancing groups
by Erik Rydgren 07 Oct '10

07 Oct '10

Hi! My company have been using pcre for a long while but there has been gripes about it only returning the last matched value from a capture group. Because of this I have been searching for a C++ regex engine that can handle the same stuff as the .NET implementation can do, to no avail. During my searches I've stumbled on several forum threads where others have been searching for the same thing but it doesn't seem to exist a regular expression library in C/C++ that handles both named captures and multicapture. Found boost.xpressive and it had almost everything we need. It's open source, fast, got flexible api and named captures. But alas, just as all other C and C++ based implementations I have found, it lacked multiple captures. So, I added it. On top of that I added support for balancing groups (http://blog.stevenlevithan.com/archives/balancing-groups) But the syntax for the pop capture and capture conditional is slightly different then the .NET version to better fit xpressive. Syntax for pop capture: dynamic: (?P<-name>stuff) static: (name -= stuff) Syntax for capture conditional: dynamic: (?P(name)stuff) static: (name &= stuff) There is no support for the (?<name-othername>stuff) construct. All captures made by a group is stored in sub_match::captures which is a vector of sub_match_capture objects. A sub_match_capture behaves like a stripped down sub_match. It can be put in an ostream and has a length and helper function for returning a string. The changes are in the vault and can be found here: http://tinyurl.com/3aak7mp It can be unpacked against trunk from 2010-10-02 or the 1.44.0 release. I've run the dynamic regression tests without errors and I have added some tests for the new functionality. The code it only tested on Visual Studio 2010 since I don't have access to any other compiler. Please give feedback on my changes since I would love to see them in an official release. Thanks in advance. Regards, Erik

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[fusion] for_each
by Christophe Henry 06 Oct '10

06 Oct '10

Hi, I have 2 fusion containers: a small vector (my_vec) and a bigger set (my_set). I want to overwrite the elements of the set with elements from the vector whenever they have the same type. Sounds simple: struct update { update(my_set_type& to_overwrite_):to_overwrite(to_overwrite_){} template<typename T> void operator()(T& elt) /*const?*/ { boost::fusion::at_key<T>(to_overwrite)=elt; } my_set_type& to_overwrite; }; boost::fusion::for_each(my_vec,update(my_set)); Except that this won't compile because the operator() is required to be const, which is sad, because it was very simple. This leaves me with the unattractive option of inverting the set and the vector inside update. Now, I iterate on the set's elements and overwrite them when found in the vector. This is unattractive because 1) the code gets really ugly 2) it could be slower (the set is bigger) and 3) it has a much bigger compile-time cost (I resorted to an enable_if of fusion::result_of::find and I make it short, it is actually much worse). I thought of using transform, but this will be slower as I will need to transform every element of the set, even for a vector of size 1. Am I missing something? If not, would it be possible to remove this constraint? Thanks, Christophe

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[Range] Composite Range
by Robert Jones 06 Oct '10

06 Oct '10

Is there any facility supported in Boost to provide a 'composite' range? I.e., a range that might be a vector, followed by a bit of list, followed by a pair of iterators? I guess the iterator classification of such a range would be the lowest common denominator of the classifications of all the component iterators, and I don't even want to think about how sort() would work, but it might be quite handy. - Rob.

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[Review] Formal Review: Boost.Ratio
by Anthony Williams 06 Oct '10

06 Oct '10

Hi everyone, The review of Vicente Botet' Ratio library starts October 2nd and lasts until October 11th, 2010, unless an extension occurs. What is it? ======== Portable implementation of the C++0x Standard Library's compile-time rational arithmetic working on C++03 and C++0x compilers. See the current C++0x working draft at http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3126.pdf Boost.Ratio provides: * A class template, ratio, for specifying compile time rational constants such as 1/3 of a nanosecond or the number of inches per meter. ratio represents a compile time ratio of compile time constants with support for compile time arithmetic with overflow and division by zero protection * It provides a textual representation of boost::ratio<N, D> in the form of a std::basic_string. Other types such as boost::duration can use these strings to aid in their I/O. This library is header-only and is designed to be generic and useful in a lot of areas of math and numerics C++ programming, in particular it is absolutely needed for the proposed Boost.Chrono and Boost.Stopwatches libraries which are currently in the review queue. Getting the library ============= The latest version of this library may be downloaded from vault: http://www.boostpro.com/vault/index.php?action=downloadfile&filename=ratio.… SVN: http://svn.boost.org/svn/boost/sandbox/chrono (directories boost/ratio and libs/ratio) and the docs may be viewed here html: http://svn.boost.org/svn/boost/sandbox/chrono/libs/ratio/doc/html/index.html pdf: http://svn.boost.org/svn/boost/sandbox/chrono/libs/ratio/doc/ratio.pdf You can get all these information also (which should avoid some long links) from http://svn.boost.org/trac/boost/wiki/LibrariesUnderConstruction#Boost.Ratio It is worth noting that the tests included in the zip file are relatively sparse. Vicente has an extensive suite of tests licensed under the LLVM license. He has posted a message on the Boost Developers mailing list regarding the license requirements for tests (See http://thread.gmane.org/gmane.comp.lib.boost.devel/208978) and is awaiting the outcome of that discussion before making the tests available. Writing a review ================ If you feel this is an interesting library, then please submit your review to the developer list (preferably), or to the review manager. Here are some questions you might want to answer in your review: - 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. Anthony Review Manager for the proposed Boost.Ratio library -- Author of C++ Concurrency in Action http://www.stdthread.co.uk/book/ just::thread C++0x thread library http://www.stdthread.co.uk Just Software Solutions Ltd http://www.justsoftwaresolutions.co.uk 15 Carrallack Mews, St Just, Cornwall, TR19 7UL, UK. Company No. 5478976

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[fusion] for_each
by Christophe Henry 06 Oct '10

06 Oct '10

I think it's at least partly my mistake. It took me some time to manage a limited example not compiling: #include <boost/fusion/container/set.hpp> #include <boost/fusion/container/vector.hpp> #include <boost/fusion/include/at_key.hpp> #include <boost/fusion/include/for_each.hpp> #include <boost/fusion/include/as_vector.hpp> struct A { int adata; }; struct B { int bdata; }; struct C { int cdata; }; typedef boost::fusion::set<A, B, C> my_set_type; typedef boost::fusion::vector<A, B> my_vector_type; struct update { update(my_set_type& to_overwrite_):to_overwrite(to_overwrite_){} template<typename T> void operator()(T& elt) const { boost::fusion::at_key<T>(to_overwrite)=elt; } my_set_type& to_overwrite; }; int main() { my_set_type my_set; my_vector_type my_vec; boost::fusion::for_each(boost::fusion::as_vector(my_vec),update(my_set)); } Now it will compile if you replace boost::fusion::as_vector(my_vec) by my_vec or T& by T const&. Ok so it seems my problem description is wrong and I needed to know that as_vector returns a const vector, right? Thanks, Christophe

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Differences between Boost.Thread and std?
by David Abrahams 05 Oct '10

05 Oct '10

Hi All, Is there a document somewhere describing the differences between Boost.Thread and what's being proposed for C++0x? Thanks, -- Dave Abrahams BoostPro Computing http://www.boostpro.com

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Re: [boost] [fusion] for_each
by Christophe Henry 05 Oct '10

05 Oct '10

>> I have 2 fusion containers: a small vector (my_vec) and a bigger set >> (my_set). I want to overwrite the elements of the set with elements >> from the vector whenever they have the same type. Sounds simple: >> >> struct update >> { >> update(my_set_type& to_overwrite_):to_overwrite(to_overwrite_){} >> template<typename T> >> void operator()(T& elt) /*const?*/ >> { >> boost::fusion::at_key<T>(to_overwrite)=elt; >> } >> my_set_type& to_overwrite; >> }; >> >> boost::fusion::for_each(my_vec,update(my_set)); >> >> Except that this won't compile because the operator() is required to >> be const, which is sad, because it was very simple. > > And it won't compile *with* the const? I don't think the const'ness of > the member function affects the const'ness of the referent of to_overwrite. No, it won't compile ;-)

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