I'm having a hard time trying to understand meta-programming. I have a template class template<class CDB> struct MyClass { template typedef MyClass > > Or; template friend Or myOperation(MyClass<CDB0> &_r0, MyClass<CDB1> &_r1); }; The template argument will be of type mpl::vector_c All the vectors will be of equal length. Now the function myOperation is supposed to iterate over both the vectors at the same time and do different operations depending on the value of both vectors at this position. I could generate a mpl::vector, ..> but I really don't know how. Any help would be appreciated. Peter

writes:

I'm having a hard time trying to understand meta-programming. I have a template class

snip

I could generate a mpl::vector, ..> but I really don't know how. Any help would be appreciated.

Peter

I'm happy to answer any MPL related questions, but I'm unclear as to what you're trying to accomplish. I'll be on IRC for a few more hours today, if you'd like to persue this on a medium that makes clarifying your problem a bit easier.

peter_foelsche wrote:

This code does not compile. I'm using Visual C++. Any help would be appreciated.

I'm still quite unclear as to what you're trying to accomplish, but the following compiles: #include <utility> #include #include #include #include #include #include #include #include #include namespace mpl = boost::mpl; template<typename T> struct wrap { }; template<typename CDB> struct CDer { }; template struct CMyOperation : private boost::noncopyable { typedef CDer < typename mpl::transform >::type > CDerOr; CMyOperation(CDer<CDB> const& r0, CDer<CDB1> const& r1, CDerOr& rT) : m_r0(r0), m_r1(r1), m_rT(rT), m_iPos(0) { } void operator ()(std::pair const&) { ++m_iPos; } private: CDer<CDB> const& m_r0; CDer<CDB1> const& m_r1; CDerOr& m_rT; unsigned m_iPos; }; template struct CCreatePair { CCreatePair(CMyOperation& op) : m_sOp(&op) { } typedef void result_type; template<typename T> void operator ()(wrap<T>) const { typedef typename mpl::front<T>::type first; typedef typename mpl::back<T>::type second; (*m_sOp)(std::make_pair(first::value, second::value)); } private: CMyOperation* m_sOp; }; template typename CMyOperation::CDerOr myOperation(CDer<CDB> const& _r0, CDer<CDB1> const& _r1) { typedef mpl::zip_view > CMerged; typename CMyOperation::CDerOr sRet; CMyOperation sOp(_r0, _r1, sRet); CCreatePair createPair(sOp); mpl::for_eachmpl::_1 >(createPair); return sRet; } int main() { CDer > sDer0; CDer > sDer1; myOperation(sDer0, sDer1); return 0; }

Sorry to rehash an old thread, I must be only person that just can not get this to work.... here is my build output: /usr/bin/make -f nbproject/Makefile-Debug.mk SUBPROJECTS= .build-conf make[1]: Entering directory `/home/etienne/NetBeansProjects/mingle' mkdir -p build/Debug/GNU-Linux-x86 g++ -c -g -o build/Debug/GNU-Linux-x86/main.o main.cc mkdir -p build/Debug/GNU-Linux-x86 g++ -c -g -o build/Debug/GNU-Linux-x86/server.o server.cc mkdir -p build/Debug/GNU-Linux-x86 g++ -c -g -o build/Debug/GNU-Linux-x86/client.o client.cc mkdir -p dist/Debug/GNU-Linux-x86 g++ -o dist/Debug/GNU-Linux-x86/mingle build/Debug/GNU-Linux-x86/main.o build/Debug/GNU-Linux-x86/server.o build/Debug/GNU-Linux-x86/client.o -lpthread build/Debug/GNU-Linux-x86/server.o: In function `mingle::server::accept()': /home/etienne/NetBeansProjects/mingle/server.cc:36: undefined reference to `mingle::server::handle_accept(mingle::client*, asio::error_code const&)' collect2: ld returned 1 exit status make[1]: *** [dist/Debug/GNU-Linux-x86/mingle] Error 1 make[1]: Leaving directory `/home/etienne/NetBeansProjects/mingle' make: *** [.build-impl] Error 2 Build failed. Exit value 2. Here is the code that complains: void server::accept( ){ client* connection = new client( acceptor_.io_service()); client_.push_back(connection); acceptor_.async_accept(connection->socket(), boost::bind(&mingle::server::handle_accept, this,connection,asio::placeholders::error)); };//accept void handle_accept( client* connection, const asio::error_code& ec ) { };//handle_accept The header file: namespace mingle { class server { public: server( asio::io_service&, short ); ~server() throw(); private: void accept(); void handle_accept( client*, const asio::error_code& ); std::vector client_; asio::ip::tcp::acceptor acceptor_; protected: }; }; Now why would the linker of all things complain that it just can not find the handle_accept method? I modeled it after the online examples with one adjustment - the client is not a Meyer's singleton like class. Packaged information: Package: libasio-dev Priority: optional Section: universe/devel Installed-Size: 1404 Maintainer: Ubuntu MOTU Developers Original-Maintainer: Simon Richter Architecture: all Source: asio Version: 0.3.8~rc3-2 Depends: libboost-dev Recommends: libssl-dev Filename: pool/universe/a/asio/libasio-dev_0.3.8~rc3-2_all.deb Size: 149402 MD5sum: fe9a5519552f5d2703238e18c85a5acb SHA1: 09fc70379b840dbba1654544b9299d11c39a6edb SHA256: 38d69bbb72ea825c8be711e407b56bc871d97d6b29693ede3a6ac05f55edc925 Description: cross-platform C++ library for network programming asio is a cross-platform C++ library for network programming that provides developers with a consistent asynchronous I/O model using a modern C++ approach. It has recently been accepted into Boost. . This package contains the development header files. Bugs: mailto:ubuntu-users@lists.ubuntu.com Origin: Ubuntu Thank you, Etienne Pretorius