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Need help with Errors in boost MPL tutorials
by Linh Ha 24 Jan '12

24 Jan '12

Dear all, I try to learn Meta-programing but i got stuck with lambda meta-function and place holder. I try to compile very simple program #include <boost/bind.hpp> #include <boost/mpl/lambda.hpp> #include <boost/type_traits.hpp> template <class F, class X> struct twice : F::template apply<typename F::template apply<X>::type > { }; template <class X> struct two_pointers : twice<typename boost::mpl::lambda<boost::add_pointer<_1> >::type, X> {}; int main(int argc, char** argv) { return 0; } It is from the boost tutorial http://www.boost.org/doc/libs/1_48_0/libs/mpl/doc/tutorial/the-lambda-metaf… . But it can not be complied. The error messages are main.cpp:21: error: type/value mismatch at argument 1 in template parameter list for ‘template<class T> struct boost::add_pointer’ main.cpp:21: error: expected a type, got ‘<unnamed>::_1’ main.cpp:21: error: template argument 1 is invalid main.cpp:21: error: template argument 3 is invalid main.cpp:21: error: template argument 1 is invalid main.cpp:22: error: expected ‘::’ before ‘{’ token main.cpp:22: error: expected class-name before ‘{’ token I use g++ (Ubuntu/Linaro 4.4.4-14ubuntu5) 4.4.5 I have no idea what happened. Any inside would be appreciated. It is important I think since lambda is used all over place with MPL. Thanks, Linh Ha

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[Spirit][karma] Generating Pascal string like output
by Olaf Meeuwissen 23 Jan '12

23 Jan '12

Hi all, While I had no trouble getting the parsing part for this to work, I'm stuck on the generator part. Specifically, I'm stuck on getting the size into the output. The goal is a rule that takes a std::vector<byte> and outputs it in such a way that it is preceded by its size (in a custom encoding) and padded by zeroes to align on a four byte boundary. I want to reuse this rule in several other rules and prefer to break it up into smaller pieces. A minimalistic example of what I have come up with so far is attached. What I can't seem figure out how to get at and store the vector's size in pascal_string_size_. There also seem to be problems with refering to the stored size_ in pascal_string_payload_ and pascal_string_padding_ that I don't understand. Note that the signed/unsigned distinction is on purpose. I am aware of the side effects of assigning to size_ and that that is not threadsafe. Any help would be appreciated. Thanks in advance, -- Olaf Meeuwissen, LPIC-2 FLOSS Engineer -- AVASYS CORPORATION FSF Associate Member #1962 Help support software freedom http://www.fsf.org/jf?referrer=1962

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grid_graph vertex properties
by David Doria 23 Jan '12

23 Jan '12

Since there is no VertexProperties template parameter on grid_graph, is it correct that you cannot use interior properties, but must use exterior properties? Thanks, David

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Building boost_1_48_0 with specified version of msvc...
by JIA Pei 23 Jan '12

23 Jan '12

Hi, all: I strictly followed "Getting Started" on Boost documentation, although I'm using a Visual Studio 2008 Command Prompt, it seems it always produce all boost libraries using VC10. Is it possible to produce boost libraries built by VC9? Please help...Thank you very much. Best Regards Pei -- Pei JIA Email: jp4work(a)gmail.com cell: +1 604-362-5816 Welcome to Vision Open http://www.visionopen.com

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Regarding Boost::asio::io-service
by Baba Prasad 23 Jan '12

23 Jan '12

Dear Friends, Please tell what is the purpose of boost::asio::io-service ios .I am New to the boost Libraries and I'm doing one Open Source project in that already used these asio service in a way of passing asio service in object. like "link l(ios, some other arguments) " My big question is at what sart of time this asio::io-service are most useful and required. Best Regards BaBu -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.

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Compile error when using program_options and lambda expression
by Jens Auer 23 Jan '12

23 Jan '12

Hi, I ran into a problem when I was replacing boost::bind expressions with lambda expressions. I could boil down the problem to the following code: #include <boost/program_options.hpp> template<typename T> void f(T t) {} void g() { using namespace boost::program_options; // each of the following lines produces the error: // Error 1 error C2871: 'validators' : a namespace with this name does not exist // Error 2 error C2871: 'program_options' : a namespace with this name does not exist f([]() {} ); auto x = []() {}; } When I try to compile this on my Microsoft Visual Studio 2010 using our Boost 1.45 library, I get a compiler errors: Error 1 error C2871: 'validators' : a namespace with this name does not exist Error 2 error C2871: 'program_options' : a namespace with this name does not exist To me, it looks like a compiler problem but I want to make sure that I am not running into a known issue in the boost libraries. I have search the bug database, but I have not found any issues like this one. It would be nice if someone could double-check this on another platform and boost version. If it is a compiler bug, I would then file a bug report to MS. Best regards, Jens

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FTP Server class
by Christer Borgqvist 23 Jan '12

23 Jan '12

Hello all, Im trying to make a multi threaded FTP Server class using boost asio. When in passiv mode, create a server listen on the data port and wait for a connection from the client, that thread need som event to trigg the thread to start send the file after the command RETR have received. is there some one that can help me. /Christer

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[units] Question about user-defined value types
by W Z 23 Jan '12

23 Jan '12

Hi, I am using boost units library for a project in which I need to define quantities using rational numbers. I have a rational number class but am having trouble integrating it with units library. There seems to be a lot of places where the units library implementation assumes that the conversion values are expressed as double type. Is there a good way to get around this to make units library support rational numbers? Thanks, WZ

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Iterating over vertices in a specific region in a graph
by David Doria 22 Jan '12

22 Jan '12

If I manually create a grid graph in BGL (using adjacency_list, not grid_graph), is there a way to iterate over vertices in a specified rectangular region? Say I make a 100x100 grid graph, how would I iterate over the the center 5x5 vertices? Thanks, David

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Multicast sender
by Carlos Guimarães 22 Jan '12

22 Jan '12

Hi, Is there any portable way (by using boost) to send multicast messages through all network interfaces available on the host? I have managed to do it by setting outbound_interface option on the socket. However, how can I know which if_index are available? Also, it only works for IPv6. If I set a IPv4 address it always use the same interface. Any suggestion? Next is the code I'm using: // DATA HERE... ip::udp::socket sock(io); sock.open(ip::udp::v6()); // Set socket flags sock.set_option(boost::asio::socket_base::reuse_address(true)); if (strcmp(dst_ip, "ff02::1") == 0) { boost::asio::socket_base::broadcast option(true); sock.set_option(option); } sock.bind(ip::udp::endpoint(ip::address_v6::any(), src_port)); for(int i = 1; i <= 5; i++) { try { sock.set_option(ip::multicast::outbound_interface(i)); sock.set_option(ip::multicast::enable_loopback(false)); ip::udp::endpoint ep(ip::address::from_string(dst_ip), dst_port); sock.async_send_to(boost::asio::buffer(sbuff, slen), ep, boost::bind((&send_handler), placeholders::error)); } catch(...) { return; } }

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