March 2009 - Boost-users - lists.preview.boost.org

Is there a way to delay the initialisation of a member in a C++ base class until the ctor of the derived class is executed?
by tom tan 25 Mar '09

25 Mar '09

Here's the scenario: I want define a base class that allocate some buffer once for all derived classes, while the size of the buffer varies among different derived classes. I could achieve it in this way: class base { public: base():size(), p_array(0){} private: size_t size; boost::shared_ptr<unsigned char> p_array; }; in the derived class: class derived { public: derived(size_t array_size):size(array_size) { p_array.reset(new unsigned char[size]); } private: size_t size; boost::shared_ptr<unsigned char> p_array; }; However, in order to simplify the design of the derived class, I really want to put this line: p_array.reset(new unsigned char[size]); to somewhere in the base class, thus writing it only once. Is there any C++ design pattern could achieve it? Thanks

3 2

linking agaisnt boost
by arun ramakrishnan 25 Mar '09

25 Mar '09

A nube question . I have been trying to understand the whole link process in VC++ . I use visual studio 8. I was trying to install the prebuild boost libs from boostpro and I tried to build my source against 1) , 2) and 3) . The three are. 1)Multithread, static runtime libboost_thread-vc80-mt-s-1_38.lib 2)Multithread libboost_thread-vc80-mt-1_38.lib 3)Multithread , DLL boost_thread-vc80-mt-1_38.dll boost_thread-vc80-mt-1_38.lib I expected there to be Multithreaded static lib and then a multithreaded dynamic shared dll . Just 2 of them , not 3 . Could someone explain the need for 3 and not just 2. OR point me to a article or something please . I have vaguely figured that 1) static boost and static CRT . 2) static boost and dynamic CRT. 3) dynamic boost and dynamic CRT. am i right ? I believe boost automatically picks up the right libs based on your project . So , when i tried to build a simple project using these libs . while using the /MT option for code generation , 1) was used as I expected it to. while using the /MD option for code generation , it linked to 2) . I am not able to build using 3) , in spite of a lot of probing into the VC8 configuration options . Also , what configuration would be needed to make my project use the boost dll i.e 3). thanks in advance .

2 1

Re: [Boost-users] BoostCon 2009 Schedule Now Live
by Paul 25 Mar '09

25 Mar '09

I beg you to recorded the conference on video/audio for those who aren't able to make the trip ... 2009/3/25 David Abrahams <dave(a)boostpro.com> > The official schedule is now live at http://www.boostcon.com/program! A > few highlights of the "mouth-watering content" (in the words of one > enrollee) are: > > * A keynote address from Andrei Alexandrescu called "Iterators Must Go." > It's sure to be provocative! > > * Troy Straszheim's presentations on how high-energy physicists are > using Boost to process massive datasets as they go "Icefishing for > Neutrinos" and on Kamasu, his library for offloading computation to > your machine's GPU. > > * Two hands-on sessions where we'll start recoding parts of Boost for > C++0x, applying rvalue references, variadic templates, decltype, and > advanced SFINAE capabilities using the latest GCC. > > * "Practical C++ Test-Driven Development with Boost.Test and Bmock," by > Asher Sterkin > > * A session on compiler construction using Boost.Spirit v2, from Hartmut > Kaiser and Joel de Guzman > > The complete list of sessions covers a wide range of other Boost and > C++-related topics. It is available at > http://www.boostcon.com/program/sessions. Please have a look, and > please, sign up for the conference! Remember, registration for the > whole week is just $599 before April 1st. > > -- > Dave Abrahams > BoostPro Computing > http://www.boostpro.com > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users >

2 1

Looking for guidance on how best to use Boost ASIO in this scenario
by console shark 24 Mar '09

24 Mar '09

I have the following scenario: Up to 1000 client users. 1 Server (or multiple instances of a server). The server(s) read a set of 5-15 incoming data feeds that update as often as 10 to 50 times per second. Each feed is updating at a different interval, as information comes in (essentially random). The server processes the data as it arrives from these feeds and when it finds a useful piece of information, it sends a message to some subset of the 1000 clients. The clients are not all interested in the same thing. It could be that each client has a different interest, and it could be that many times per second each client will need to be notified of that interest. That should be the worst case scenario, as meaningful changes in information probably won't require updates to the client that often, even though the 5-15 feeds are constantly updating. So what is the best way to structure this design using ASIO? Should the 1000 clients actually be set up as servers, and the server really just contact them by connecting each time there is an update that interest them? Or should the 1000 clients all connect with a permanent connection, polling for updates? Thanks for any advice.

2 3

[boost-users][exception] BOOST_THROW_EXCEPTION returns
by Igor R 24 Mar '09

24 Mar '09

Hello all, A function throws boost::exception as follows: //.... typedef boost::error_info<struct tag_action, std::string> action_name; BOOST_THROW_EXCEPTION(error() << action_name(name)); return 0; Both BOOST_NO_EXCEPTIONS and BOOST_EXCEPTION_DISABLE are *not* defined. The excpetion is not catched anywhere. However, the thread continues running! If I put breakpoint at "return 0;" it's hit, and I can continue stepping the code. I run the program under MSVC 9.0, in debug mode, and I see "First-chance exception" and "Unhandled exception" notifications issued by the debugger. Isn't it wrong behavior, or I miss something? Thanks, Igor'.

2 3

BoostCon 2009 Schedule Now Live
by David Abrahams 24 Mar '09

24 Mar '09

The official schedule is now live at http://www.boostcon.com/program! A few highlights of the "mouth-watering content" (in the words of one enrollee) are: * A keynote address from Andrei Alexandrescu called "Iterators Must Go." It's sure to be provocative! * Troy Straszheim's presentations on how high-energy physicists are using Boost to process massive datasets as they go "Icefishing for Neutrinos" and on Kamasu, his library for offloading computation to your machine's GPU. * Two hands-on sessions where we'll start recoding parts of Boost for C++0x, applying rvalue references, variadic templates, decltype, and advanced SFINAE capabilities using the latest GCC. * "Practical C++ Test-Driven Development with Boost.Test and Bmock," by Asher Sterkin * A session on compiler construction using Boost.Spirit v2, from Hartmut Kaiser and Joel de Guzman The complete list of sessions covers a wide range of other Boost and C++-related topics. It is available at http://www.boostcon.com/program/sessions. Please have a look, and please, sign up for the conference! Remember, registration for the whole week is just $599 before April 1st. -- Dave Abrahams BoostPro Computing http://www.boostpro.com

1 0

Find last modified date of file
by Thor Andreas Tangen 24 Mar '09

24 Mar '09

Hi Is it possible by using boost to find the last modified date of a file? I looked in filesystem, but could not find it there. Thanks Thor Andreas

3 2

[boost-users][exception] BOOST_THROW_EXCEPTION returns
by Igor R 24 Mar '09

24 Mar '09

Hello all, A function throws boost::exception as follows: //.... typedef boost::error_info<struct tag_action, std::string> action_name; BOOST_THROW_EXCEPTION(error() << action_name(name)); return 0; Both BOOST_NO_EXCEPTIONS and BOOST_EXCEPTION_DISABLE are *not* defined. The excpetion is not catched anywhere. However, the thread continues running! If I put breakpoint at "return 0;" it's hit, and I can continue stepping the code. I run the program under MSVC 9.0, in debug mode, and I see "First-chance exception" and "Unhandled exception" notifications issued by the debugger. Isn't it wrong behavior, or I miss something? Thanks, Igor'.

2 3

Integrating boost into project version control
by Kenneth Porter 24 Mar '09

24 Mar '09

I have an existing C++ project that uses a few 3rd party libraries. It's maintained in a Subversion repository and the libraries are imported into the repository using the Subversion "vendor branch" paradigm together with Subversion "externals". I want to add Boost to the project, and am looking for guidance from others who have a project in Subversion: Should I import Boost sources into my repo, rebuilding on each developer's system as part of the normal whole-project build, or should I install a binary distro of Boost on each developer's system? The former guarantees that the repo always contains the source used to build our binaries, but at the cost of longer build times to build Boost each time the project is built. I'm currently building with Visual Studio 2005 and 2008, and will eventually be cross-compiling for an embedded Linux system.

4 4

[lambda] extending lambda functions
by alfC 24 Mar '09

24 Mar '09

For some application I need to sum the complex modulus of a collection of elements. In short, I want to be able to replace the lambda expression _1 + bind(&std::norm<double>, _2) by something more natural like _1 + llnorm(_2) For that I use std::accumulate and the lambda library, like in the next working example; #include<boost/lambda/lambda.hpp> #include<boost/lambda/bind.hpp> using namespace boost::lambda; int main(){ using boost::lambda::_1; using boost::lambda::_2; std::vector<std::complex<double> > v(3); v[0]=1.; v[1]=2.; v[2]=3.; double result=std::accumulate(v.begin(), v.end(), double(0.), _1 + bind(&std::norm<double>, _2)); std::cout<<result<<std::endl; return 0; } the question is what do I have to do to be able to use the following syntax instead _1 + llnorm(_2) where llnorm is something I have to define (globally) somewhere else. The question is, how do I have to define llnorm to have the desired effect? The ideal syntax for me would be to be able to say std::norm(_2) or std::norm<double>(_2), but that may not be possible due to name conflict, is it? I am clueless because I don't even know even what is the (C++) type of the argument that would be taken by llnorm. Thanks, Alfredo

3 7