- Boost-users - lists.boost.org

Re: [Boost-users] [units]
by Kelly, Dan 15 Sep '13

15 Sep '13

I have had much the same experience as you. The library seems to hold a lot of promise and is from what I can see very sophisticated. But I had the same problems with the documentation and examples. I struggled for some time to figure out the difference between units and base units (and dimensions and base dimensions) and when you would use each. If someone could put together a decent tutorial I'm sure I would use this library quite frequently. -----Original Message----- From: Robert Ramey [ramey(a)rrsd.com<mailto:ramey@rrsd.com>] Sent: Sunday, September 15, 2013 01:14 PM Eastern Standard Time To: boost-users(a)lists.boost.org Subject: [Boost-users] [units] I have an urgent and definite need for the functionality which boost.units is meant to provide. The concept is quite simple so I had expected it to be relatively easy to use. I had anticipated spending a few hours perusing the documentation and examples, adding code to my application and moving on. T'was not to be. I'm now on day 3 (or 4?) trying to figure this thing out. The main hurdle is that the documentation is indecipherable. There are a number of templated classes defined which depend upon each other. I expect to find a page for each of the templates along with a description of what the template arguments should be. (Ideally these should be backed up with concept checking classes). Ideally there would be a small example showing how one would use these templates. It seems that the library is layered from low level ideas to higher level ones. The documentation touches on this - but its not really formalized. Theres a reference section which includes scores of things like base_units types for wide variety of units - but no where is there any indication how these should be used - not even in the examples are they used. There is a concept of "system" (of dimensions?) and the idea of mixing units from different systems and the idea that the same dimension (eg length) have multiple renderings in the system (nautical vs metric). I realize I've likely got this wrong and I'm not asking for anyone to explain this to me here - my point is that what should be very simple is incredibly confusing. I still haven't figured out whether it's only the documentation which is incomplete or if it is the actual logical design of the library itself is what's flawed. I'm still working on this. I don't remember much traffic on this list regarding this library and if I google information on boost C++ units library I don't get a whole lot of hits. This could mean that that the library is so easy to use no one ever needs to ask about it or it could be that almost no one every uses it. In Boost we don't gather statistics on usage by library so I don't which of these it might be. So my question is: Has anyone had good success with this library? How much effort did it take? What did you have to do to make it work. I would be curious about any other user feed back in these questions. Robert Ramey _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users ________________________________ IMPORTANT: The information contained in this email and/or its attachments is confidential. If you are not the intended recipient, please notify the sender immediately by reply and immediately delete this message and all its attachments. Any review, use, reproduction, disclosure or dissemination of this message or any attachment by an unintended recipient is strictly prohibited. Neither this message nor any attachment is intended as or should be construed as an offer, solicitation or recommendation to buy or sell any security or other financial instrument. Neither the sender, his or her employer nor any of their respective affiliates makes any warranties as to the completeness or accuracy of any of the information contained herein or that this message or any of its attachments is free of viruses.

1 0

[coroutine] Resuming of coroutine from another thread
by Jason Roehm 15 Sep '13

15 Sep '13

I'm thinking up a design for a task-processing system that uses Boost.Asio and Boost.Coroutine. As part of that design, I would have a pool of worker threads executing work items. During processing of a particular work item, it's possible that the worker might need to wait on some other operation (e.g. I/O) to complete. However, while it waits, I'd like to put that thread to work doing something else useful from the queue. I was thinking of using coroutines to provide the ability to suspend the processing of one task, restarting it later when it is ready to move forward again. In my hypothetical framework, the thread that finishes the work might not be the same one that started it in the first place. I recently came across this Stack Overflow question: http://stackoverflow.com/questions/8557067/thread-safe-coroutines-with-asio which inquired as to the safety of creating a coroutine in one thread and then resuming it in another. The answers there indicate that this is not supported, and they link to Boost.Coroutine documentation that explains the underlying problems and why it isn't supported. However, that documentation was from the original Boost.Coroutine by Giovanni Deretta (which I'm not sure was ever actually accepted into Boost). The latest version by Oliver Kowalke indicates that it is a follow-up on that library, but doesn't have any specific caveats in the documentation regarding the interaction between threads and coroutines. Does the contemporary Boost.Coroutine have the same limitation, or is it safe to create a coroutine in one thread and then resume it in another? Jason

2 1

Max Boost Fusion tuple parameters
by Rodrigo Madera 14 Sep '13

14 Sep '13

Hello, What is the maximum Boost Fusion tuple param count? I was thinking of using it for about 200-300 elements. Anyone done this? I've heard of defines for this, but never actually *knew* of anyone actually doing it. Thanks, Rodrigo Madera

4 11

Too many EOF's using boost::asio
by ustulation 13 Sep '13

13 Sep '13

I have a TCP server and client with following read and write functions: ----------------- Writes ---------------------- void SomeClass::startWrite() { //m_writeBuffer is boost::asio::streambuf..m_writeQueue is std::deque<std::string> m_writeBuffer.sputn(&m_writeQueue.at(0)[0], m_writeQueue.at(0).size()); //m_objStrandWrite is boost::asio::strand boost::asio::async_write( getSocket(), m_writeBuffer, m_objStrandWrite.wrap([this](const boost::system::error_code &e, std::size_t bytesTxd){writeHandler(e, bytesTxd);}) ); } void SomeClass::writeHandler(const boost::system::error_code &refErrorCode, std::size_t bytesTxd) { if(!m_bIsStopped) { m_writeQueue.pop_front(); if(refErrorCode) { if(refErrorCode != boost::asio::error::operation_aborted) { std::cerr << "Write Error: " << refErrorCode.message() << std::endl; stop(); } } else { if(!m_writeQueue.empty()) { startWrite(); } } } } ------------------- Reads ----------------- void SomeClass::startRead() { //m_readBuffer is boost::asio::streambuf..m_objStrandRead is boost::asio::strand boost::asio::async_read_until( getSocket(), m_readBuffer, m_szTermString, m_objStrandRead.wrap([this](const boost::system::error_code &e, std::size_t bytesRxd){readHandler(e, bytesRxd);}) ); } void SomeClass::readHandler(const boost::system::error_code &refErrorCode, std::size_t bytesRxd) { if(!m_bIsStopped) { if(refErrorCode) { if(refErrorCode != boost::asio::error::operation_aborted) { std::cerr << "Read error: " << refErrorCode.message() << std::endl; stop(); } } else { if(bytesRxd) { std::string szRxdData; szRxdData.resize(bytesRxd); m_readBuffer.sgetn(&szRxdData[0], bytesRxd); } startRead(); } } } I get very frequent End Of File (EOF) error on client's read. It is not always but frequent. I am running a threadpool by asking multiple std::threads to execute io_service::run() which never quits until io_service::stop() is called. The data given by the server is almost never more than 5MB. As you see in the code, for any error I call stop() which shuts down the connection gracefully. <Q> *Is there something wrong I'm doing because I see no reason for EOF error. Why should the server close/shutdown the connection?* The code does not do that explicitly. Anyway it is random - out of 10 times maybe 5 are successful reads and 5 become EOF's and I have to restart my client executable to connect again in each of those cases. Other sockets don't do that - eg., I've tested with QTcpSocket of Qt framework and it works all the time (no randomness). -- View this message in context: http://boost.2283326.n4.nabble.com/Too-many-EOF-s-using-boost-asio-tp465117… Sent from the Boost - Users mailing list archive at Nabble.com.

4 5

using boost with net-snmp
by moshe levi 12 Sep '13

12 Sep '13

I wrote an example on how to integrate net-snmp with boost. please checkout http://blog-moshe.blogspot.co.il/

2 1

ICMP Ping example running problem
by shunguang 12 Sep '13

12 Sep '13

Hi all, When i run *ping.cpp * at .\boost_1_53_0\doc\html\boost_asio\example\icmp, it comes with the error message: "Exception: open: An attempt was made to access a socket in a way forbidden by its access permissions". Debug shows that it comes from calling ",* socket_ (io_service , icmp::v4() )*" in the constructor. Google says the running computer must have administrator right, i do have it. i also checked my firewall settings, it looks fine to me also. Does anyone can give a help? Thanks, -shunguang -- View this message in context: http://boost.2283326.n4.nabble.com/ICMP-Ping-example-running-problem-tp4651… Sent from the Boost - Users mailing list archive at Nabble.com.

2 4

[coroutine] help with code from docs
by Jeff Flinn 12 Sep '13

12 Sep '13

I'm trying to understand coroutine usage with boost 1.53.0. I'm getting an assertion when running the code snippet from the docs "Creating a coroutine" from http://www.boost.org/doc/libs/1_53_0/libs/coroutine/doc/html/coroutine/coro… #include <boost/coroutine/all.hpp> #include <string> typedef boost::coroutines::coroutine< int (std::string const&) > coro_t; // void f( boost::coroutine< std::string const&( int) > & ca) void f( coro_t::caller_type & ca) { std::string str( ca.get() ); // asserts here! ca(7); } int main(int argc, char* argv[]) { std::string str("abc"); coro_t c(f); c(str); // pass argument int res = c.get(); // returned value return 0; } Asserts in coroutine_get.hpp line 43: BOOST_ASSERT( static_cast< D const* >( this)->impl_->result_); Is the snippet from the doc incorrect or am I doing something else wrong. Thanks, Jeff

2 3

boost::tr1::tuple or boost::tuple? how to compile the same code with both -std=c++98 and -std=c++11?
by Frédéric Bron 12 Sep '13

12 Sep '13

This small program compiles nicely with g++ 4.6.4 and -std=c++98 and boost 1.52.0: #include <iostream> #include <boost/math/tools/roots.hpp> #include <boost/tr1/tuple.hpp> std::tr1::tuple<double, double> f(double x) { return std::tr1::tuple<double, double>(x, 1.); } int main() { std::cout<<boost::math::tools::newton_raphson_iterate(f, 10., -9., +20., 10); return 0; } Now, I would like to be able to compile that program also with g++ 4.8.1 and -std=c++11 (I changed also boost to 1.53.0). If I do not change anything, std::tr1::tuple is replaced by std::tuple and I get the following error (see attached log): path/to/boost/include/boost/math/tools/roots.hpp:202:32: error: no match for 'operator=' (operand types are 'std::tuple<double&, double&>' and 'boost::fusion::tuple<double, double>') I tried to replace <boost/tr1/tuple.hpp> and std::tr1::tuple by <boost/tuple/tuple.hpp> and boost::tuple without any success. What should I do to have the same code compile with both -std=c++98 and -std=c++11? Regards, Frédéric

1 0

Regex on Windows2012
by Michael Xanadu 11 Sep '13

11 Sep '13

Hi guys, I developed a little application called MyProgram.exe (Win7, VS2008 SP1, Qt 4.8.4) and a little DLL called MyLibrary.dll. The DLL uses BOOST's regex engine 1.5. The executable calls the DLL via couple of functions, one function inside the DLL uses the regex engine. I've tested the environment on Windows7 and all is OK. BUT: If I copy the application and the DLL to Windows2012 I see that the executable crashes if I use it. I took a closer look to the issue and found out that the cause for the crash seems to be the regex engine inside the DLL. If regex functions will be called inside the DLL, it crashes and also the application does. AND: The strange thing is, that this problem seems to occur only on Windows2012 and only if the regex engine is inside a DLL. If I use Windows7 instead or uses the regex engine inside an executable on Windows2012 - everything works fine. I've already tried a lot to solve the problem, including using different linking approaches (BOOST as shared DLL etc.). I wonder if anybody had similar issues or can give me a hint of what went wrong? Regards, Michael

1 0

syntax error reporting from imported python modules
by Richi Lists 11 Sep '13

11 Sep '13

Hi, when I execute a python script that contains errors, I get nice and complete information from boost::python::error_already_set about the error and it's location. If the script that contains a syntax error is not executed directly, but imported from the main script, I don't get that exception. Instead it returns from the function as if everything was successful. When I check the result, the tasks from the other files were performed, just the stuff from the erroneous file is missing. Do I need to somehow attach the error reporting to the imported files? Rgds Richard

1 0