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[array] change proposal for the c_array() function
by herve martin 18 Mar '09

18 Mar '09

Hi, I'm new in this mailing list .My interest are embedded software and code reuse. I would submit a simple change request in the boost::array library. The boost::c_array() function is expected to cast a boost::array<T,N> into a C-array but actually the returned type is a T* which is not exactly a reference on a C-array. to keep track of the static size and make sizeof( myarray.c_array() ) returning the real size of the C-array, I suggest to change: T* c_array() { return elems; } into T (&c_array())[N] { return *(T(*)[N]) elems; } by the way, I have developed a function helper array_cast<> whose purpose is to: * make a bit more friendly the syntax when casting to a C-array * check consistency between size of the input type and size of the target C-array for example, { long titi; char (&test)[4] = utils::array_cast<char>( titi ); test[0] = 0; } assuming that long is 32 bit long and char is 8 bit long, 'test[0]' is now a reference on the 1st byte of 'titi'. Moreover declaring test as a char(&)[5] would have failed in compiling since size of both types are not suitable (but the function provides some other way to force cast when sizes are not compatible) do you think that there could be any interest to include this function in boost library ? thanks, herve

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Why my subexpression doesn't work in Regex
by Qihong Wang 18 Mar '09

18 Mar '09

Hello, I'm a new boost and regex user. I tried a c++ regex sample as follows regex pattern("banan\\(an\\)*a"); string str = "bananana"; if(regex_match(str, pattern)) cout<<"---- pattern matched ----"<<endl; else cout<<"---- pattern unmatched ----"<<endl; To my surprise, the it printed out pattern unmatched. If I change str to "banan(an)a", the result is pattern matched. Feels like boost.Regex doesn't treat ( ) as subexpression. Any idea? Thanks, Qihong Wang

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[lexical_cast] Strange behaviour
by Robert Jones 18 Mar '09

18 Mar '09

Trying again 'cos I mucked up the code last time! This code #include <iostream> #include <boost/lexical_cast.hpp> int main() { using namespace std; try { unsigned int u=boost::lexical_cast<unsigned int>("-1"); cout << u << '\n'; } catch(const std::exception&) { cout << "Exception" << '\n'; } } produces 4294967295 on MSVC7 & 8 rather than an exception. Is it supposed to do this? Rob.

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[utility] new auto_buffer class --- RFC
by Thorsten Ottosen 18 Mar '09

18 Mar '09

Dear all, For a long time I have been missing this utility in my own work, and in boost related stuff too. I think there are a number of libraries in boost that can benefit from this utility. Libs like boost.format can be quite a bit more effective. So can logging libraries. etc. Basically boost::auto_buffer<T,N> is a C++ version of variable lenght array (from C99). It's based on Matthew Wilson's stlsoft::auto_buffer, which can be found described in his book "Imperfect C++". I have changed a few things though: // - no swap() and resize() provided // - works with allocators from Boost.Interprocess // - do not store T[N] on the stack, as this is bad when the // type has a non-trivial default constructor. // - handless non-pod types in an exception-safe manner // - has a fixed capacity, but a non-fixed size // - provides a non-growing (thus inlineable) push_back() Comments are most welcome. best regards -Thorsten

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reference to ‘_1’ is ambiguous
by Sandeep Gupta 18 Mar '09

18 Mar '09

Hi, This problem has appeared before on the list but in a different context. The following code std::vector<int> myvec; for_each(myvec, std::cout<<_1<<' '); gives the error: Serializer.h:78: error: reference to ‘_1’ is ambiguous /home/sandeep/Computing/boost_1_38_0/boost/lambda/core.hpp:69: error: candidates are: const boost::lambda::placeholder1_type& boost::lambda::<unnamed>::_1 /home/sandeep/Computing/boost_1_38_0/boost/bind/placeholders.hpp:54: error: boost::arg<1> <unnamed>::_1 Serializer.h:78: error: reference to ‘_1’ is ambiguous I believe boost/bind is getting included indirectly via some other library. I have tried several modification but none seem to work as I was quite reluctant to post a third mail on the list. Thanks, sandep

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pointer to member function of multi_index
by Sandeep Gupta 18 Mar '09

18 Mar '09

Hi, I am sure this is due to some trivial mistake; the statement to create a pointer member function insert of multi_index container fails in the following code: typedef multi_index_container< std::pair<int,int>, indexed_by< ordered_unique<member<pair<int,int>, int, &pair<int, int>::first> > > > mic; std::pair<mic_index::iterator, bool> (mic_index::*fn)(pair<int,int>) = &mic_index::insert; //compile error The error is due to mismatch in signature as given in the error: std::pair<boost::multi_index::detail::bidir_node_iterator<boost::multi_index::detail::ordered_index_node<boost::multi_index::detail::index_node_base<std::pair<int, int>, ... std::pair<boost::multi_index::detail::bidir_node_iterator<boost::multi_index::detail::ordered_index_node<typename SuperMeta::type::node_type> >, bool>... If need be I can post full error message. Appreciate any suggestions. Thanks sandeep

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correct usage of bind (pls ignore last email)
by Sandeep Gupta 17 Mar '09

17 Mar '09

Hi, The code below tries to chain function ft1 (argument is a pair) with function buildPair (returns a pair). template<typename X, typename Y> std::pair<X, Y> buildPair(X x, Y y) { std::pair<X,Y> apair(x,y); return apair; } int main() { typedef boost::function<void (std::pair<int,int>)> FuncType1_t; std::vector<std::pair<int,int> > myvec; FuncType1_t ft1 = bind(&std::vector<std::pair<int,int> > ::push_back, &myvec, _1); typedef boost::function<void(std::pair<int,int>)> FuncType2_t; FuncType2_t ft2 = bind(ft1, bind(buildPair<int,int>,_1,_2)); //compile fails return 0; } This fails. The problem however vanished if I replace the declaration "FuncType3 ft2..." with bind(ft1, bind(buildPair<int,int>,_1,_2))(3,5); So my question is what is correct type of bind(ft1, bind(buildPair<int,int>,_1,_2)); Thanks sandeep

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correct usage of bind
by Sandeep Gupta 17 Mar '09

17 Mar '09

Hi, Both the statements below bind function buildPair. While the first works the other fails. What could be a possible fix. Thanks in advance. //---- Function to be used by bind ------------------------- template<typename X, typename Y> std::pair<X, Y> buildPair(X x, Y y) { std::pair<X,Y> apair(x,y); return apair; } (std::cout<<buildPair(_1,_2).first<<' ')(1,2); ///--compiles fine--------- (bind(buildPair,_1,_2))(3,5); ///-fails------------ Thanks sandeep

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[Review] Polynomial library review begins today
by John Maddock 17 Mar '09

17 Mar '09

The review of Pawel Kieliszczyk's Polynomial library begins today and ends on Thurs 19th March. Download of the zip file from the vault is here: http://www.boostpro.com/vault/index.php?action=downloadfile&filename=polyno… Otherwise the library is present in the sandbox here: https://svn.boost.org/svn/boost/sandbox/SOC/2008/polynomial/ And the docs can be read online here: https://svn.boost.org/svn/boost/sandbox/SOC/2008/polynomial/libs/docs/index… The polynomial library contains a single class - polynomial<FieldType> - used for the manipulation of polynomials, along with a selection of algorithms which operate upon them. The library is an extension/rewrite of the existing "implementation detail" polynomial class in Boost.Math, and was written as part of last years Google Summer of Code under the mentorship of Fernando Cacciola. What to include in Review Comments ~~~~~~~~~~~~~~~~~~~~~~~~~ Your comments may be brief or lengthy, but basically the Review Manager needs your evaluation of the library. If you identify problems along the way, please note if they are minor, serious, or showstoppers. The goal of a Boost library review is to improve the library through constructive criticism, and at the end a decision must be made: is the library good enough at this point to accept into Boost? If not, we hope to have provided enough constructive criticism for it to be improved and accepted at a later time. The Serialization library is a good example of how constructive criticism resulted in revisions resulting in an excellent library that was accepted in its second review. 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. Many reviews include questions for library authors. Authors are interested in defending their library against your criticisms; otherwise they would not have brought their library up for review. If you don't get a response to your question quickly, be patient; if it takes too long or you don't get an answer you feel is sufficient, ask again or try to rephrase the question. Do remember that English is not the native language for many Boosters, and that can cause misunderstandings. E-mail is a poor communication medium, and even if messages rarely get lost in transmission, they often get drowned in the deluge of other messages. Don't assume that an unanswered message means you're being ignored. Given constructively, criticism will be taken better and have more positive effects, and you'll get the answers you want. John Maddock. Review Manager for Polynomial Library.

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Re: [boost] [C++-sig] [Python] GSoC and Python 3.0 Support
by Stefan Seefeld 17 Mar '09

17 Mar '09

Niall Douglas wrote: > > I would say that any GSoC project should choose *one* of the above > rather than try combining them. Better to do one thing well and in > stages than many things at once (unless you have loads of spare > time!). > I agree. (I wouldn't mind seeing projects for all of the above, but they definitely shouldn't be combined into one.) >>> Thanks! Seems there's a lot of interesting. So would anyone willing to >>> mentor this? >>> >> Sadly, I suspect that finding a mentor will be difficult (perhaps even more >> difficult than the actual project). Off the top of my head, the following >> folks come to mind: >> - Dave Abrahams >> - Stefan Seefeld >> - Ralf Grosse-Kunstleve >> - Roman Yakovenko >> You might try contacting them off list or on c++-sig (cc'ed on this email). >> I'm willing to participate, in particular, if other folks such as David are part of such a team, too. (While I believe I understand enough of both C++ and Python, lots of boost.python is still very obscure, so having David being part would greatly help. May be we could take the opportunity and collectively work on the (internal) boost.python docs, too. David, I notice you already indicated support. Could we team up for this ? (I will be out on vacation for about two weeks during the summer. Other than that I should be available throughout the summer.) Thanks, Stefan -- ...ich hab' noch einen Koffer in Berlin...

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