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  • Boost and XML (c++)

    - by Nuno
    Hi, Is there any good way (and a simple way too) using boost to read and write xml files? I can't seem to find any simple sample to read xml files using boost? (can you point me some simple sample that use boost for reading and writing xml files) If not boost, is out there any good and simple library to read and write xml files that you can recommend? (it must be a c++ library) Thanks Nuno

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  • How Important is Boost to Learn for C++ Developers

    - by mahesh
    I am curious to learn Boost. But i wanted to ask how important it is to learn. What pre-requisite one should need before jumping on Boost. Why i am curious to know about Boost is that many people are talking about Boost on IRC's channels and here in StackOverflow. Thanks in advance.

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  • How to remove compiler flag when building Boost

    - by mlo
    I need to build Boost with a non-standard set of flags (due to a conflict between Boost threading and C++/CLI). I'm adding the required flag (/clr) using CXXFLAGS, but this flag conflicts with the Boost default /EHs flag (/clr implies /EHa which is incompatible with /EHs), so that needs to be suppressed. Is there a mechanism like CXXFLAGS to suppress a default Boost flag or must I edit all of the compiler specification files by hand?

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  • Signals and threads - good or bad design decision?

    - by Jens
    I have to write a program that performs highly computationally intensive calculations. The program might run for several days. The calculation can be separated easily in different threads without the need of shared data. I want a GUI or a web service that informs me of the current status. My current design uses BOOST::signals2 and BOOST::thread. It compiles and so far works as expected. If a thread finished one iteration and new data is available it calls a signal which is connected to a slot in the GUI class. My question(s): Is this combination of signals and threads a wise idea? I another forum somebody advised someone else not to "go down this road". Are there potential deadly pitfalls nearby that I failed to see? Is my expectation realistic that it will be "easy" to use my GUI class to provide a web interface or a QT, a VTK or a whatever window? Is there a more clever alternative (like other boost libs) that I overlooked? following code compiles with g++ -Wall -o main -lboost_thread-mt <filename>.cpp code follows: #include <boost/signals2.hpp> #include <boost/thread.hpp> #include <boost/bind.hpp> #include <iostream> #include <iterator> #include <string> using std::cout; using std::cerr; using std::string; /** * Called when a CalcThread finished a new bunch of data. */ boost::signals2::signal<void(string)> signal_new_data; /** * The whole data will be stored here. */ class DataCollector { typedef boost::mutex::scoped_lock scoped_lock; boost::mutex mutex; public: /** * Called by CalcThreads call the to store their data. */ void push(const string &s, const string &caller_name) { scoped_lock lock(mutex); _data.push_back(s); signal_new_data(caller_name); } /** * Output everything collected so far to std::out. */ void out() { typedef std::vector<string>::const_iterator iter; for (iter i = _data.begin(); i != _data.end(); ++i) cout << " " << *i << "\n"; } private: std::vector<string> _data; }; /** * Several of those can calculate stuff. * No data sharing needed. */ struct CalcThread { CalcThread(string name, DataCollector &datcol) : _name(name), _datcol(datcol) { } /** * Expensive algorithms will be implemented here. * @param num_results how many data sets are to be calculated by this thread. */ void operator()(int num_results) { for (int i = 1; i <= num_results; ++i) { std::stringstream s; s << "["; if (i == num_results) s << "LAST "; s << "DATA " << i << " from thread " << _name << "]"; _datcol.push(s.str(), _name); } } private: string _name; DataCollector &_datcol; }; /** * Maybe some VTK or QT or both will be used someday. */ class GuiClass { public: GuiClass(DataCollector &datcol) : _datcol(datcol) { } /** * If the GUI wants to present or at least count the data collected so far. * @param caller_name is the name of the thread whose data is new. */ void slot_data_changed(string caller_name) const { cout << "GuiClass knows: new data from " << caller_name << std::endl; } private: DataCollector & _datcol; }; int main() { DataCollector datcol; GuiClass mc(datcol); signal_new_data.connect(boost::bind(&GuiClass::slot_data_changed, &mc, _1)); CalcThread r1("A", datcol), r2("B", datcol), r3("C", datcol), r4("D", datcol), r5("E", datcol); boost::thread t1(r1, 3); boost::thread t2(r2, 1); boost::thread t3(r3, 2); boost::thread t4(r4, 2); boost::thread t5(r5, 3); t1.join(); t2.join(); t3.join(); t4.join(); t5.join(); datcol.out(); cout << "\nDone" << std::endl; return 0; }

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  • How do I install newer python on CentOS with minimal effort?

    - by Sorin Sbarnea
    I would like to install Python 2.6 and mod_python on CentOS 5 (x64). The system is delivered with old python 2.4 and I want the new one with minimal maintenance effort (compiling and having a different installation seams to be suboptimal solution). Is there a solution for this, other than starting to recompile lots of packages? If not should I switch to Ubuntu? Please remember that I'm talking about x64 - I found a repository on net with updated packages but it is not x64.

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  • Python install issue on Mac OS X

    - by Michael Waterfall
    I have been using the standard python that comes with OS X Lion (2.7.2) but I wanted to build a UCS-4 version to handle 4-byte unicode characters better. I had already installed pip and packages like pytz, virtualenv and virtualenvwrapper, etc., and these are installed in /Library/Python/2.7/site-packages. My $PATH is /usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin. To build a new version of python on the machine (outside of any project specific virtual environments, that will come later), I followed the instructions on this article and managed to build it in /usr/local/bin. The problem is that when I launched a new bash window, I got the following virtualenvwrapper error: Traceback (most recent call last): File "<string>", line 1, in <module> ImportError: No module named virtualenvwrapper.hook_loader virtualenvwrapper.sh: There was a problem running the initialization hooks. If Python could not import the module virtualenvwrapper.hook_loader, check that virtualenv has been installed for VIRTUALENVWRAPPER_PYTHON=/usr/local/bin/python and that PATH is set properly. The instructions said to move /usr/local/bin to the top of the /etc/paths file, and since then I've noticed some strange issues. I installed pip into /usr/local/bin and now I have assumed that since I'm working in /usr/local/bin, and the newly installed python's site packages is now located in /usr/local/lib/python2.7/site-packages, when I do pip freeze, it should be empty as nothing is installed there yet. However, pip freeze still reports things installed in the old (OS X) site-packages folder. Here's some info after the build: $ which python /usr/local/bin/python $ which pip /usr/local/bin/pip $ echo $PATH /usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin When I uninstall a python package with pip, it removes it from the old site-packages folder as expected. When I install it again, instead of installing it in /usr/local/lib/python2.7/site-packages, it installs it in /Library/Python/2.7/site-packages (verified by attempting to install it again and receiving Requirement already satisfied (use --upgrade to upgrade): pytz in /Library/Python/2.7/site-packages ). How is it getting that path for the old site-packages folder? Why won't it install it in the correct location for the python install it's using? I'm getting several other issues since promoting /usr/local/bin but I think if I understand this I'll be able to get somewhere. Can anyone see what's happening? If you need any more info I'll be happy to provide it.

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  • Python default version errors

    - by Robus
    For a while I've been getting this error while doing anything apt-get related: Preparing to replace python-cairo 1.4.12-1.2 (using .../python-cairo_1.8.8-1+b1_i386.deb) ... Traceback (most recent call last): [...] File "/usr/share/pycentral-data/pyversions.py", line 172, in default_version raise ValueError, "/usr/bin/python does not match the python default version. It must be reset to point to %s" % debian_default ValueError: /usr/bin/python does not match the python default version. It must be reset to point to python2.6.6 Whereas robus:/# /usr/bin/python -V Python 2.6.6 How do I fix this? I did try fixing symlinks, but then I keep getting 'too many symlink levels' errors.

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  • What would cause the "gi" module to be missing from python?

    - by Catalin Dumitru
    After some not so clever editing of the default Python version in Ubuntu, from 2.7 to 3.2, I ended up breaking my entire system. After my computer imploded and everything stopped working, I tried to revert back my changes (by linking /usr/bin/python2.7 to /usr/bin/python and changing the default version in /usr/share/python/debian_defaults back to 2.7) but some things are still broken. For example when I type "import gi" in the python interpreter I get the fallowing message : >>> import gi Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: No module named gi >>> error which appears with some programs too (eg: gnome tweak tool). I have tried re-installing python both from the software center and from sources, but the same error persists. Python -- version now returns : Python 2.7.2 and also some software packages which depend on python 2.7 are now working (for example the software center), but some things are still broken. Is there anything I can do to completely re-install python 2.7 as the default version?

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  • Python vs. Perl in ten years time

    - by Richard
    If you were starting learning a new language today, for scripting and doing "various stuff" with it (from making useful programs to it being glue to several command line programs), would you go with Python or Perl (or some third option, although the battle usually comes to these two)? I've never much used dynamic languages at all, having been able to do everything I needed in traditional static ones. Did some scripting in Perl a couple of years ago, but that was more of a momentary fling, than an attempt to learn it well. Now I've some free time, and have decided to go along with one of these two, and play a little with them. I like Perl's syntax, but Python does seem to be taking rather big steps on overtaking that area. What do you think, which one is more worth learning and why? Also, what do you think, what will be Python's future in about 10 years ... will it overtake Perl and other scripting languages's as a dominant tool for that kind of work (I more often than not find it being implemented in various applications I'm using - for internal scripting and automating loading of data and similar operations), or will it find a balance and coexist along others (Perl)? What is its current "momentum" - does it comes by default with Linux distributions, as Perl does, or does it needs to be installed separately every time? Is it a language which can be expected "to just be there"?

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  • UBJsonReader (Libgdx) unable to to read UBJson from Python(Blender)

    - by daniel
    I am working on an export tool from Blender to Libgdx, exports like custom attributes and other information (Almost completed), this is a very cool tool that will speed up a lot your works, after I completed I will send to public to contribute forum, Export format is uses python's Standard Json module and readable text, it of course works fine, but I wanna also have a Binary Json export for faster load, so users can Export Straight to Libgdx, but after I search I found that UBJson with draft9.py (simpleubjson 0.6.1) encode is seems matches with one FBXConverter's UBJsonWriter( Xoppa wrote), but when I export, I am not able to read the file, and send this errors (Java heap space) seems this is a different between byte sizes in UBJson(python) and UBJsonReader. how can I write a correct one in python that matches with Libgdx's UBJsonReader, and would be cross-platform? Exception in thread "LWJGL Application" com.badlogic.gdx.utils.GdxRuntimeException: java.lang.OutOfMemoryError: Java heap space at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:120) Caused by: java.lang.OutOfMemoryError: Java heap space at com.badlogic.gdx.utils.UBJsonReader.readString(UBJsonReader.java:162) at com.badlogic.gdx.utils.UBJsonReader.parseString(UBJsonReader.java:150) at com.badlogic.gdx.utils.UBJsonReader.parseObject(UBJsonReader.java:112) at com.badlogic.gdx.utils.UBJsonReader.parse(UBJsonReader.java:59) at com.badlogic.gdx.utils.UBJsonReader.parse(UBJsonReader.java:52) at com.badlogic.gdx.utils.UBJsonReader.parse(UBJsonReader.java:36) at com.badlogic.gdx.utils.UBJsonReader.parse(UBJsonReader.java:45) at com.me.gdximportexport.GdxImportExport.create(GdxImportExport.java:43) at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:136) at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:114) Tested on UbuntuStudio 13.10 with OpenJdk 7, and Windows 7 with jdk 7 Thanks for any guides.

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  • Browser-based GUI for a python application

    - by ack__
    I want to create a web/browser-based GUI for a command-line python application. The goal is to make use of HTML/JS technologies to create this GUI. As the application itself, it needs to run on Linux and Windows, and the interface will be accessible only from localhost (not exposed to internet). The GUI will contain 5 to 10 pages. I don't want a traditional desktop GUI that includes HTML/JS, but just a bunch of html files and some kind of controller between those and the application. I also want to make use of asynchronous programming (ajax like) so I can load and print data in the GUI without refreshing the whole page. I'd probably use jQuery for that and a couple other things. How would you recommend to design this? Performance is not the key here, I'm rather looking at reliability, portability and simplicity. I'm thinking of using a lightweight python HTTP server / framework (like CherryPy) and maybe later a Python templating system (at the begining it will just be a couple pages). EDIT: I'm looking for ideas/recommendations how to build this, not for alternatives to browser/web-based GUI.

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  • Python web frameworks comparisons

    - by stupidLearner
    I recently asked a question on SO about Python web frameworks: http://stackoverflow.com/questions/4909306/python-web-frameworks-vs-java-web-frameworks-how-is-web-development-in-python-do I want to learn one just for fun but it also has to be able to help me deliver a proper working application. I am looking for a framework with lots of features, powerful, mature, with large community, good documentation, books etc. I need something that will help me be more productive in developing my app and not waste time figuring out how to do a certain thing in the framework or how to write workaround around the limitations of the framework. I was thinking one of the following: django, zope, turbogears, pylons. Off course the war is raging out there and there are other alternatives but seems Django is at the top... or is it just hype? I am interested in pros and cons of each. What was the best feature you think the framework has? What is the thing it lacks? What could have been done differently. Help me chose one to learn for starters.

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  • Duck checker in Python: does one exist?

    - by elliot42
    Python uses duck-typing, rather than static type checking. But many of the same concerns ultimately apply: does an object have the desired methods and attributes? Do those attributes have valid, in-range values? Whether you're writing constraints in code, or writing test cases, or validating user input, or just debugging, inevitably somewhere you'll need to verify that an object is still in a proper state--that it still "looks like a duck" and "quacks like a duck." In statically typed languages you can simply declare "int x", and anytime you create or mutate x, it will always be a valid int. It seems feasible to decorate a Python object to ensure that it is valid under certain constraints, and that every time that object is mutated it is still valid under those constraints. Ideally there would be a simple declarative syntax to express "hasattr length and length is non-negative" (not in those words. Not unlike Rails validators, but less human-language and more programming-language). You could think of this as ad-hoc interface/type system, or you could think of it as an ever-present object-level unit test. Does such a library exist to declare and validate constraint/duck-checking on Python-objects? Is this an unreasonable tool to want? :) (Thanks!) Contrived example: rectangle = {'length': 5, 'width': 10} # We live in a fictional universe where multiplication is super expensive. # Therefore any time we multiply, we need to cache the results. def area(rect): if 'area' in rect: return rect['area'] rect['area'] = rect['length'] * rect['width'] return rect['area'] print area(rectangle) rectangle['length'] = 15 print area(rectangle) # compare expected vs. actual output! # imagine the same thing with object attributes rather than dictionary keys.

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  • Is C and Python enough?

    - by gruszczy
    I am very proficient in Python (including Django), which I use for most tasks. I am also quite confident with C; I am maintaining small file system in userspace written in C. Yet when I am browsing job offers I see everywhere Java/C# and sometimes C++. I have coded profesionally in C++ for half a year in a gaming company, but I don't consider myself a pro. Also I simply despise Java and C#, which I would prefer not to touch ever. But it seems to me, that I am at very unfavorable position, when it comes to career. I am browsing careers.stackoverflow.com and I don't see and pure python or C offers. I would like to find a new job abroad in about 6 months. If I find some python offer, it means doing web development (not my favorite job). Does it mean, that I have to quickly start improving my C++ skills, if I wish to find a satisfying job? What would you suggest me? EDIT Learning new technologies is not an issue. Company I am working in is an integrator. Basically every new project requires learning new technologies, sometimes custom made. During last two years I was writing SQLs by hand, using LDAP, writing GUI in Qt, working on large scale DBMS prototype, making our internal help desk system use gsm modem or writing own report system. In previous job I had to learn from basics everything what I could about games development, because I knew nothing and chose this job only because of the challene it posed. I am all about embracing new technologies. I have used Java in the past and simply didn't like it. It's dull and boring. Doesn't let me do anything cool. I have recently seen some C# in action and seems similar. I don't like it. It's like German. I don't like speaking German.

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  • Experience of Python's “PEP-302 New Import Hooks”

    - by Koichi Sasada
    I'm one of the developers of Ruby (CRuby). We are working on Ruby 2.0 release (planned to release 2012/Feb). Python has "PEP302: New Import Hooks" (2003): This PEP proposes to add a new set of import hooks that offer better customization of the Python import mechanism. Contrary to the current import hook, a new-style hook can be injected into the existing scheme, allowing for a finer grained control of how modules are found and how they are loaded. We are considering introducing a feature similar to PEP302 into Ruby 2.0 (CRuby 2.0). I want to make a proposal which can persuade Matz. Currently, CRuby can load scripts from only file systems in a standard way. If you have any experience or consideration about PEP 302, please share. Example: It's a great spec. No need to change it. It is almost good, but it has this problem... If I could go back to 2003, then I would change the spec to... I'm sorry if such a question is not suitable for here. I posted here because I'm not sure that I can ask this question at python-dev (of course, the list is not for cruby development). This post is moved from http://stackoverflow.com/questions/11188229/experience-of-pythons-pep-302-new-import-hooks.

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  • still about perl vs python but (to me) slightly different from what has been asked [closed]

    - by B Chen
    Being a newbie to coding, I read from this site that Perl is still as viable as it has been, while Python, quoted from someone else's post, is good but just "snake oil" (not sure what this refers to exactly though). So from the responses in that post, I got the gist that Perl is good and worthy to learn. My question is - pardon me for phrasing it in this "non-programmer's" way - Which one should I learn FIRST? (I am actually currently learning R) Here below is the background info - (a) I will be using it mostly for data mining and statistics analysis (b) Will there be this "first" and "later" issue with learning either Perl or Python? That is, after I become competent with one language, would there be a need to learn the second one (for a similar task??) (c) If there should be circumstances where I must learn the second one, would learning Perl FIRST be better than learning Python? I hope to learn as much from exchanging info here, so please help provide with more than just "it depends" type of info. Great many thanks to all who choose to respond to my query.

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  • Solving a difficult incomplete type error

    - by ChAoS
    I get an incomplete type error when trying to compile my code. I know that it is related to includes, but my project is large and it uses several templates so I can't find which type is actually incomplete. The error message doesn't help either: Compiling: ../../../addons/ofxTableGestures/src/Graphics/objects/CursorFeedback.cpp In file included from ../../../addons/ofxTableGestures/ext/boost/fusion/include/invoke_procedure.hpp:10, from ../../../addons/ofxTableGestures/src/oscGestures/tuioApp.hpp:46, from /home/thechaos/Projectes/of_preRelease_v0061_linux_FAT/addons/../apps/OF-TangibleFramework/ofxTableGestures/src/Graphics/objects/CursorFeedback.hpp:35, from /home/thechaos/Projectes/of_preRelease_v0061_linux_FAT/addons/../apps/OF-TangibleFramework/ofxTableGestures/src/Graphics/objects/CursorFeedback.cpp:31: ../../../addons/ofxTableGestures/ext/boost/fusion/functional/invocation/invoke_procedure.hpp: In function ‘void boost::fusion::invoke_procedure(Function, const Sequence&) [with Function = void (tuio::CanBasicFingers<Graphic>::*)(long int, float, float, float, float, float), Sequence = boost::fusion::joint_view<boost::fusion::joint_view<boost::fusion::iterator_range<boost::fusion::vector_iterator<const boost::fusion::vector6<long int, float, float, float, float, float>, 0>, boost::fusion::vector_iterator<boost::fusion::vector6<long int, float, float, float, float, float>, 0> >, const boost::fusion::single_view<tuio::CanBasicFingers<Graphic>*> >, boost::fusion::iterator_range<boost::fusion::vector_iterator<boost::fusion::vector6<long int, float, float, float, float, float>, 0>, boost::fusion::vector_iterator<const boost::fusion::vector6<long int, float, float, float, float, float>, 6> > >]’: ../../../addons/ofxTableGestures/src/oscGestures/tuioApp.hpp:122: instantiated from ‘void tuio::AlternateCallback<C, M, E>::run(tuio::TEvent*) [with C = tuio::CanBasicFingers<Graphic>, M = void (tuio::CanBasicFingers<Graphic>::*)(long int, float, float, float, float, float), E = tuio::TeventBasicFingersMoveFinger]’ /home/thechaos/Projectes/of_preRelease_v0061_linux_FAT/addons/../apps/OF-TangibleFramework/ofxTableGestures/src/Graphics/objects/CursorFeedback.cpp:64: instantiated from here ../../../addons/ofxTableGestures/ext/boost/fusion/functional/invocation/invoke_procedure.hpp:88: error: incomplete type ‘boost::fusion::detail::invoke_procedure_impl<void (tuio::CanBasicFingers<Graphic>::*)(long int, float, float, float, float, float), const boost::fusion::joint_view<boost::fusion::joint_view<boost::fusion::iterator_range<boost::fusion::vector_iterator<const boost::fusion::vector6<long int, float, float, float, float, float>, 0>, boost::fusion::vector_iterator<boost::fusion::vector6<long int, float, float, float, float, float>, 0> >, const boost::fusion::single_view<tuio::CanBasicFingers<Graphic>*> >, boost::fusion::iterator_range<boost::fusion::vector_iterator<boost::fusion::vector6<long int, float, float, float, float, float>, 0>, boost::fusion::vector_iterator<const boost::fusion::vector6<long int, float, float, float, float, float>, 6> > >, 7, true, false>’ used in nested name specifier If I copy the conflictive code to a same file I can compile it. So I know that the code itself is OK, the problem is the way I instantiate it. How can I trace the origin of this error? Is there any way to get the trace of the c++ compiler and preprocessor to get more informative messages?

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  • How to implement ctypes in IronPython

    - by Walter
    I need help. I have a code which is passing a script into a DLL and initialize the instrument. But, one of the code unable to use in IronPython beside python 2.7 and 3.3 I have attached the code as below enter code here import ctypes import time, sys DLLHANDLE=ctypes.cdll.LoadLibrary("C:\\INSTRDLL\\builds\\DCSOURCEDLL\\B2902A.dll") INPUTSCRIPT="SYSTEM{DCSOURCE1|INIT}" INPUTVOLTAGE=0.0 c_INPUTSCRIPT=ctypes.c_char_p(INPUTSCRIPT) c_INPUTVOLTAGE=ctypes.c_double(INPUTVOLTAGE) SOURCEHANDLE=DLLHANDLE.DCSOURCE(c_INPUTSCRIPT,c_INPUTVOLTAGE) time.sleep(1) Once "SOURCEHANDLE=DLLHANDLE.DCSOURCE(c_INPUTSCRIPT,c_INPUTVOLTAGE)" is triggered, Ironpython will crash automatically and no idea how to resolve it... or any workaround solution? Please advice..

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  • async_write/async_read problems while trying to implement question-answer logic

    - by Max
    Good day. I'm trying to implement a question - answer logic using boost::asio. On the Client I have: void Send_Message() { .... boost::asio::async_write(server_socket, boost::asio::buffer(&Message, sizeof(Message)), boost::bind(&Client::Handle_Write_Message, this, boost::asio::placeholders::error)); .... } void Handle_Write_Message(const boost::system::error_code& error) { .... std::cout << "Message was sent.\n"; .... boost::asio::async_read(server_socket_,boost::asio::buffer(&Message, sizeof(Message)), boost::bind(&Client::Handle_Read_Message, this, boost::asio::placeholders::error)); .... } void Handle_Read_Message(const boost::system::error_code& error) { .... std::cout << "I have a new message.\n"; .... } And on the Server i have the "same - logic" code: void Read_Message() { .... boost::asio::async_read(client_socket, boost::asio::buffer(&Message, sizeof(Message)), boost::bind(&Server::Handle_Read_Message, this, boost::asio::placeholders::error)); .... } void Handle_Read_Message(const boost::system::error_code& error) { .... std::cout << "I have a new message.\n"; .... boost::asio::async_write(client_socket_,boost::asio::buffer(&Message, sizeof(Message)), boost::bind(&Server::Handle_Write_Message, this, boost::asio::placeholders::error)); .... } void Handle_Write_Message(const boost::system::error_code& error) { .... std::cout << "Message was sent back.\n"; .... } Message it's just a structure. And the output on the Client is: Message was sent. Output on the Server is: I have a new message. And that's all. After this both programs are still working but nothing happens. I tried to implement code like: if (!error) { .... } else { // close sockets and etc. } But there are no errors in reading or writing. Both programs are just running normally, but doesn't interact with each other. This code is quite obvious but i can't understand why it's not working. Thanks in advance for any advice.

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  • g++ linker error--typeinfo, but not vtable

    - by James
    I know the standard answer for a linker error about missing typeinfo usually also involves vtable and some virtual function that I forgot to actually define. I'm fairly certain that's not the situation this time. Here's the error: UI.o: In function boost::shared_ptr<Graphics::Widgets::WidgetSet>::shared_ptr<Graphics::Resource::GroupByState>(boost::shared_ptr<Graphics::Resource::GroupByState> const&, boost::detail::dynamic_cast_tag)': UI.cpp:(.text._ZN5boost10shared_ptrIN8Graphics7Widgets9WidgetSetEEC1INS1_8Resource12GroupByStateEEERKNS0_IT_EENS_6detail16dynamic_cast_tagE[boost::shared_ptr<Graphics::Widgets::WidgetSet>::shared_ptr<Graphics::Resource::GroupByState>(boost::shared_ptr<Graphics::Resource::GroupByState> const&, boost::detail::dynamic_cast_tag)]+0x30): undefined reference totypeinfo for Graphics::Widgets::WidgetSet' Running c++filt on the obnoxious mangled name shows that it actually is looking at .boost::shared_ptr::shared_ptr(boost::shared_ptr const&, boost::detail::dynamic_cast_tag) The inheritance hierarchy looks something like class AbstractGroup { typedef boost::shared_ptr<AbstractGroup> Ptr; ... }; class WidgetSet : public AbstractGroup { typedef boost::shared_ptr<WidgetSet> Ptr; ... }; class GroupByState : public AbstractGroup { ... }; Then there's this: class UI : public GroupByState { ... void LoadWidgets( GroupByState::Ptr resource ); }; Then the original implementation: void UI::LoadWidgets( GroupByState::Ptr resource ) { WidgetSet::Ptr tmp( boost::dynamic_pointer_cast< WidgetSet >(resource) ); if( tmp ) { ... } } Stupid error on my part (trying to cast to a sibling class with a shared parent), even if the error is kind of cryptic. Changing to this: void UI::LoadWidgets( AbstractGroup::Ptr resource ) { WidgetSet::Ptr tmp( boost::dynamic_pointer_cast< WidgetSet >(resource) ); if( tmp ) { ... } } (which I'm fairly sure is what I actually meant to be doing) left me with a very similar error: UI.o: In function boost::shared_ptr<Graphics::Widgets::WidgetSet>::shared_ptr<Graphics::_Drawer::Group>(boost::shared_ptr<Graphics::_Drawer::Group> const&, boost::detail::dynamic_cast_tag)': UI.cpp:(.text._ZN5boost10shared_ptrIN8Graphics7Widgets9WidgetSetEEC1INS1_7_Drawer5GroupEEERKNS0_IT_EENS_6detail16dynamic_cast_tagE[boost::shared_ptr<Graphics::Widgets::WidgetSet>::shared_ptr<Graphics::_Drawer::Group>(boost::shared_ptr<Graphics::_Drawer::Group> const&, boost::detail::dynamic_cast_tag)]+0x30): undefined reference totypeinfo for Graphics::Widgets::WidgetSet' collect2: ld returned 1 exit status dynamic_cast_tag is just an empty struct in boost/shared_ptr.hpp. It's just a guess that boost might have anything at all to do with the error. Passing in a WidgetSet::Ptr totally eliminates the need for a cast, and it builds fine (which is why I think there's more going on than the standard answer for this question). Obviously, I'm trimming away a lot of details that might be important. My next step is to cut it down to the smallest example that fails to build, but I figured I'd try the lazy way out and take a stab on here first. TIA!

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  • What is wrong with this attempt of sending a break-signal?

    - by Jook
    I have quite a headache about this seemingly easy task: send a break signal to my device, like the wxTerm (or any similar Terminal application) does. This signal has to be 125ms long, according to my tests and the devices specification. It should result in a specific response, but what I get is a longer response than expected, and the transmitted date is false. e.g.: what it should respond 08 00 81 00 00 01 07 00 what it does respond 08 01 0A 0C 10 40 40 07 00 7F What really boggles me is, that after I have used wxTerm to look at my available com-ports (without connecting or sending anything), my code starts to work! I can send then as many breaks as I like, I get my response right from then on. I have to reset my PC in order to try it again. What the heck is going on here?! Here is my code for a reset through a break-signal: minicom_client(boost::asio::io_service& io_service, unsigned int baud, const string& device) : active_(true), io_service_(io_service), serialPort(io_service, device) { if (!serialPort.is_open()) { cerr << "Failed to open serial port\n"; return; } boost::asio::serial_port_base::flow_control FLOW( boost::asio::serial_port_base::flow_control::hardware ); boost::asio::serial_port_base::baud_rate baud_option(baud); serialPort.set_option(FLOW); serialPort.set_option(baud_option); read_start(); std::cout << SetCommBreak(serialPort.native_handle()) << std::endl; std::cout << GetLastError() << std::endl; boost::posix_time::ptime mst1 = boost::posix_time::microsec_clock::local_time(); boost::this_thread::sleep(boost::posix_time::millisec(125)); boost::posix_time::ptime mst2 = boost::posix_time::microsec_clock::local_time(); std::cout << ClearCommBreak(serialPort.native_handle()) << std::endl; std::cout << GetLastError() << std::endl; boost::posix_time::time_duration msdiff = mst2 - mst1; std::cout << msdiff.total_milliseconds() << std::endl; } Edit: It was only necessary to look at the combo-box selection of com-ports of wxTerm - no active connection was needed to be established in order to make my code work. I am guessing, that there is some sort of initialisation missing, which is done, when wxTerm is creating the list for the serial-port combo-box.

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  • Why did Apple remove Python support in Mavericks, aka Mac OS X 10.9?

    - by alex gray
    Apple has removed Python support (at least on the Developer level) in 10.9. Python IS still on the machine in /System/Library/Frameworks/Python.framework... but trying to link to Python using the 10.9 SDK fails. /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/System/Library/Frameworks does not have Python. I'm not a Pythonista, but find it interesting that Apple has made this change. I don't understand why this is done and I'm a bit annoyed that I have to remove Python from my compilation units in order to compile with 10.9 SDK. Is this a statement by Apple, along the lines of "People aren't using Python very much anymore so we're going to phase out support"? Or was something else driving the change?

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  • Why should we use low level languages if a high level one like python can do almost everything? [closed]

    - by killown
    I know python is not suitable for things like microcontrolers, make drivers etc, but besides that, you can do everything using python, companys get stuck with speed optimizations for real hard time system but does forget other factors which one you can just upgrade your hardware for speed proposes in order to get your python program fit in it, if you think how much cust can the company have to maintain a system written in C, the comparison is like that: for example: 10 programmers to mantain a system written in c and just one programmer to mantain a system written in python, with python you can buy some better hardware to fit your python program, I think that low level languages tend to get more cost, since programmers aren't so cheaply than a hardware upgrade, then, this is my point, why should a system be written in c instead of python?

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  • Speed up bitstring/bit operations in Python?

    - by Xavier Ho
    I wrote a prime number generator using Sieve of Eratosthenes and Python 3.1. The code runs correctly and gracefully at 0.32 seconds on ideone.com to generate prime numbers up to 1,000,000. # from bitstring import BitString def prime_numbers(limit=1000000): '''Prime number generator. Yields the series 2, 3, 5, 7, 11, 13, 17, 19, 23, 29 ... using Sieve of Eratosthenes. ''' yield 2 sub_limit = int(limit**0.5) flags = [False, False] + [True] * (limit - 2) # flags = BitString(limit) # Step through all the odd numbers for i in range(3, limit, 2): if flags[i] is False: # if flags[i] is True: continue yield i # Exclude further multiples of the current prime number if i <= sub_limit: for j in range(i*3, limit, i<<1): flags[j] = False # flags[j] = True The problem is, I run out of memory when I try to generate numbers up to 1,000,000,000. flags = [False, False] + [True] * (limit - 2) MemoryError As you can imagine, allocating 1 billion boolean values (1 byte 4 or 8 bytes (see comment) each in Python) is really not feasible, so I looked into bitstring. I figured, using 1 bit for each flag would be much more memory-efficient. However, the program's performance dropped drastically - 24 seconds runtime, for prime number up to 1,000,000. This is probably due to the internal implementation of bitstring. You can comment/uncomment the three lines to see what I changed to use BitString, as the code snippet above. My question is, is there a way to speed up my program, with or without bitstring?

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  • Resizing image algorithm in python

    - by hippocampus
    So, I'm learning my self python by this tutorial and I'm stuck with exercise number 13 which says: Write a function to uniformly shrink or enlarge an image. Your function should take an image along with a scaling factor. To shrink the image the scale factor should be between 0 and 1 to enlarge the image the scaling factor should be greater than 1. This is not meant as a question about PIL, but to ask which algorithm to use so I can code it myself. I've found some similar questions like this, but I dunno how to translate this into python. Any help would be appreciated. I've come to this: import image win = image.ImageWin() img = image.Image("cy.png") factor = 2 W = img.getWidth() H = img.getHeight() newW = int(W*factor) newH = int(H*factor) newImage = image.EmptyImage(newW, newH) for col in range(newW): for row in range(newH): p = img.getPixel(col,row) newImage.setPixel(col*factor,row*factor,p) newImage.draw(win) win.exitonclick() I should do this in a function, but this doesn't matter right now. Arguments for function would be (image, factor). You can try it on OP tutorial in ActiveCode. It makes a stretched image with empty columns :.

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