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  • Referring to the type of an inner class in Scala

    - by saucisson
    The following code tries to mimic Polymorphic Embedding of DSLs: rather than giving the behavior in Inner, it is encoded in the useInner method of its enclosing class. I added the enclosing method so that user has only to keep a reference to Inner instances, but can always get their enclosing instance. By doing this, all Inner instances from a specific Outer instance are bound to only one behavior (but it is wanted here). abstract class Outer { sealed class Inner { def enclosing = Outer.this } def useInner(x:Inner) : Boolean } def toBoolean(x:Outer#Inner) : Boolean = x.enclosing.useInner(x) It does not compile and scala 2.8 complains about: type mismatch; found: sandbox.Outer#Inner required: _81.Inner where val _81:sandbox.Outer From Programming Scala: Nested classes and A Tour of Scala: Inner Classes, it seems to me that the problem is that useInnerexpects as argument an Inner instance from a specific Outer instance. What is the true explanation and how to solve this problem ?

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  • What skills are needed to be successful at robotics?

    - by Click Upvote
    I'm considering studying to be a robotics engineer. The desire to work in that field is definitely there.. but I'm wondering what my chances of success would be. Generally I'm good with mental tasks of any sort such as programming, maths, physics, etc, and I think i'd be able to do electrical work such as soldering wires, changing batteries, etc. However, I'm not so good with things of a physical nature where I have to use my hands. For example, if you give me some vegetables to slice and dice, all of them will be diced un-evenly and some will look ugly. This might be because I have poor mind-hand coordination or because of a lack of concentration. Thoughts?

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  • Controlling the laziest common denominator

    - by bobobobo
    This is a programming-related question in that it has to do with combatting the laziest common denominator in a start-up like team. Some devs are driven. They wanna do stuff. They wanna build feature after feature. They wanna do it all. Others are.. lazy. And in every team there's someone who is the laziest. Some lazy people though have an influence on the others.. by their behavior and words, they actually make other people wanna do less. You can't always get rid of these people. But you need to control it. How?

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  • How do I remove (or apply) transparency on a gdk-pixbuf?

    - by Andrew Stacey
    I have a c++ program in which a gdk-pixbuf is created. I want to output it as an image, so I call gdk_pixbuf_save_to_stream(pixbuf,stream,type,NULL,&err,NULL). This works fine when "type" is png or tiff, but with jpeg or bmp it just produces a black square. The original pixbuf consists of black-on-transparent (and gdk_pixbuf_get_has_alpha returns true) so I'm guessing that the problem is with the alpha mask. GdkPixbuf has a function to add an alpha channel, but I can't see one that removes it again, or (which might be as good) to invert it. Is there a simple way to get the jpeg and bmp formats to work properly? (I should say that I'm very new to proper programming like this.)

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  • Listing time every second as a Bash script

    - by Caleb
    Hello all, first time here as I've finally started to learn programming. Anyway, I'm just trying to print the time in nanoseconds every second here, and I have this: #!/usr/bin/env bash while true; do date=(date +%N) ; echo $date ; sleep 1 ; done Now, that simply yields a string of date's, which isn't what I want. My learning has been rather messy, so I hope you'll excuse me for this if it's really simple. Also, I did manage to fine this, that worked on the prompt: while true ; do date +%N ; sleep 1 ; done But that obviously doesn't work as a script.

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  • How To create a Simple NDK Program in Android NDK

    - by Rakesh
    Hi I am new to android Programming and NDK.Yet i am not clear with working in NDK.I just downloaded android ndk r4.If i want to develop appln using NDK,and i refered http://marakana.com/forums/android/android_examples/49.html for reference,But still not clear how to create the header file and implementation,I did nt have any previuos exp in c language.And they asked for run javah tool to create the JNI header file. I dont know how to use javah tool,but i found it in java bin directory and i tried using cmd javah -jni com.pathname.classname is this correct syntax? if so i tried doing it in android bin directory.I want to know ,what classname represents,is this name of header file class that i try to create Regards Rakesh Shankar.P

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  • Are C++ meta-templates required knowledge for programmers?

    - by Robert Gould
    In my experience Meta-templates are really fun (when your compilers are compliant), and can give good performance boosts, and luckily I'm surrounded by seasoned C++ programmers that also grok meta-templates, however occasionally a new developer arrives and can't make heads or tails of some of the meta-template tricks we use (mostly Andrei Alenxandrescu stuff), for a few weeks until he gets initiated appropriately. So I was wondering what's the situation for other C++ programmers out there? Should meta-template programming be something C++ programmers should be "required" to know (excluding entry level students of course), or not? Edit: Note my question is related to production code and not little samples or prototypes

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  • GDI fast scroll

    - by genesys
    Hi! I use GDI to create some custom textwidget. I draw directly to the screen, unbuffered. now i'd like to implement some fast scrolling, that simply pixelshifts the respective part of the framebuffer (and only redraws the newly visible lines). I noticed that for example the rich text controls does it like this. If i use some GDI drawing functions to directly draw to the framebuffer, over a rich text control, and then scroll the rich text, it will also scroll my drawing along with the text. so i assume the rich text simply pixelshifts it's part of the framebuffer. I'd like to do the same, but don't know how to do so. Can someone help? (independant of programming language)) thanks!

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  • Questions every good Java/J2EE Developer should be able to answer?

    - by Rachel
    I was going through Questions every good .Net developer should be able to answer and was highly impressed with the content and approach of this question, and so in the same spirit, I am asking this question for Java/J2EE Developer. What questions do you think should a good Java/J2EE programmer be able to answer? I am marking this question as community wiki as it is not user specific and it aims to serve programming community at large. Looking forward for some amazing responses. EDIT: Please answer questions too, as suggested in the comments, so that people could learn something new regarding the language, too.

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  • What language is to binary, as Perl is to text?

    - by ehdr
    I am looking for a scripting (or higher level programming) language (or e.g. modules for Python or similar languages) for effortlessly analyzing and manipulating binary data in files (e.g. core dumps), much like Perl allows manipulating text files very smoothly. Things I want to do include presenting arbitrary chunks of the data in various forms (binary, decimal, hex), convert data from one endianess to another, etc. That is, things you normally would use C or assembly for, but I'm looking for a language which allows for writing tiny pieces of code for highly specific, one-time purposes very quickly. Any suggestions?

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  • Smartest way to draw 100+ images on screen

    - by Henrik
    Hello all, First of all I'm a newbie when it comes to Android programming. So if this question is totally stupid please delete it ASAP :-). Question: I'm going to draw a grid of 10x10 PNG images. Each image is 32x32 px. All of the images are unique. I'm thinking that the easiest way seems to be to put each image in an ImageView. If adding all ImageView's to the layout would this give me some kind of performance hit? Would there be any smarter way to draw these images? Thanks. / Henrik

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  • Ios Parse Login

    - by user3806600
    I am programming an IOS app that will use parse to login a user. Using storyboard I have the login button connected to another view controller with the push segue. Whether the username and password are correct the button selection always goes to the new view controller. I might be doing this all wrong. Any help is appreciated. Here is my code: - (IBAction)signIn:(id)sender { [PFUser logInWithUsernameInBackground:self.emailField.text password:self.passwordField.text block:^(PFUser *user, NSError *error) { if (!error) { [self performSegueWithIdentifier:@"signIn" sender:nil]; } else { // The login failed. Check error to see why. } }]; }

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  • Can a grails controller extend from a base class? How to make it so grails doesn't blow up?

    - by egervari
    I wrote a base class to help build my controllers more quickly and to remove duplication. It provides some helper methods, default actions and some meta programming to make these things easier to build. One of those methods in the base class is like this: def dynamicList(Class clazz) { def model = new LinkedHashMap() model[getMapString(clazz) + "s"] = list(clazz) model[getMapString(clazz) + "sTotal"] = count(clazz) model } The action that calls it, also in the base class, is this: def list = { dynamicList(clazz) } Unfortunately, when I go to list action in the controller subclass that inherits the base class when my application is deployed, I get this exception: groovy.lang.MissingMethodException: No signature of method: groovy.lang.MissingMethodException.dynamicList() is applicable for argument types: (java.lang.Class) values: [class project .user.User] at project.user.UserController$_closure1.doCall(UserController.groovy:18) at project.user.UserController$_closure1.doCall(UserController.groovy) at java.lang.Thread.run(Thread.java:619) How can I hit grails over the head and just tell it do what I want it to do? My controller unit tests run just fine, so grails' run-time is totally at fault :/ Ken

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  • Static libraries, dynamic libraries, DLLs, entry points, headers ... how to get out of this alive?

    - by tunnuz
    Hello, I recently had to program C++ under Windows for an University project, and I'm pretty confused about static and dynamic libraries system, what the compiler needs, what the linker needs, how to build a library ... is there any good document about this out there? I'm pretty confused about the *nix library system as well (so, dylibs, the ar tool, how to compile them ...), can you point a review document about the current library techniques on the various architectures? Note: due to my poor knowledge this message could contain wrong concepts, feel free to edit it. Thank you Feel free to add more reference, I will add them to the summary. References Since most of you posted *nix or Windows specific references I will summarize here the best ones, I will mark as accepted answer the Wikipedia one, because is a good start point (and has references inside too) to get introduced to this stuff. Program Library Howto (Unix) Dynamic-Link Libraries (from MSDN) (Windows) DLL Information (StackOverflow) (Windows) Programming in C (Unix) An Overview of Compiling and Linking (Windows)

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  • What happens with TCP packets between two Socket.BeginReceive calls?

    - by Rodrigo
    I have a doubt about socket programming. I am developing a TCP packet sniffer. I am using Socket.BeginAccept, Socket.BeginReceive to capture every packet, but when a packet is received I have to process something. It is a fast operation, but would take some milliseconds, and then call BeginReceive again. My question is, what would happen if some packets are sent while I am processing, and haven't called BeginReceive? Are packets lost, or are they buffered internally? Is there a limit?

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  • Python: undefined reference to `_imp __Py_InitModule4'

    - by Mark
    I'm trying to do a debug build of the Rabbyt library using mingw's gcc to run with my MSVC built python26_d.. I got a lot of undefined references which caused me to create libpython26_d.a, however one of the undefined references remains. Googling gives me: http://www.techlists.org/archives/programming/pythonlist/2003-03/msg01035.shtml But -rdynamic doesn't help. e:\MinGW/bin\gcc.exe -mno-cygwin -mdll -O -Wall -g -IE:\code\python\python\py26\ include -IE:\code\python\python\py26\PC -c rabbyt/rabbyt._rabbyt.c -o build\temp .win32-2.6-pydebug\Debug\rabbyt\rabbyt._rabbyt.o -O3 -fno-strict-aliasing rabbyt/rabbyt._rabbyt.c:1351: warning: '__Pyx_SetItemInt' defined but not used writing build\temp.win32-2.6-pydebug\Debug\rabbyt\_rabbyt_d.def e:\MinGW/bin\gcc.exe -mno-cygwin -shared -g build\temp.win32-2.6-pydebug\Debug\r abbyt\rabbyt._rabbyt.o build\temp.win32-2.6-pydebug\Debug\rabbyt\_rabbyt_d.def - LE:\code\python\python\py26\libs -LE:\code\python\python\py26\PCbuild -lopengl32 -lglu32 -lpython26_d -lmsvcr90 -o build\lib.win32-2.6-pydebug\rabbyt\_rabbyt_d. pyd build\temp.win32-2.6-pydebug\Debug\rabbyt\rabbyt._rabbyt.o: In function `init_ra bbyt': E:/code/python/rabbyt/rabbyt/rabbyt._rabbyt.c:1121: undefined reference to `_imp __Py_InitModule4'

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  • Job queue manager with RPC interface

    - by admr
    I need a job queue manager that I can control over the Internet. It should be able to execute and stop processes, check on their status (ideally notice and execute some code when a process exits), respond to commands and also be able to report back to a server. Background: I have a GWT application that allows to create jobs to execute on a cloud instance (currently EC2). I want to push a "job packet" (data for a process to operate on etc) to S3, start a Linux EC2 instance (or use one that's already running), and tell a job manager on the instance to execute that job (possibly parallel to other jobs). It should then pull the "job packet" from S3, run a process that operates on that data and report back to the server that is running the server part of my GWT application with some information (e.g. exit code, stdout, stderr). If I have to write e.g. stdour/err to a file from the process and read that file, that's OK too. I would really like the manager to be "close" to the processes it runs, meaning I want to avoid using something like Runtime.exec from the JDK. It seems like I would have to do that if I used Quartz for example. I'm fine with the calls in both directions being asynchronous. I'm fine with any reasonable technology for the calls as long as I can easily build an interface for that in my GWT server side (e.g. HTTP requests to a servlet over SSL would be nice and trivial). The job manager does not need to have a very sophisticated queueing system. Running several processes either sequentially or in parallel should be fine. Determining how much compute time a process received during its lifetime would be nice (AFAIK, this might be challenging). I did not yet find any existing software that does this, including http://java-source.net/open-source/job-schedulers. I suspect I might have to build an RPC interface (with authentication etc, of course) around a job manager; maybe use something like Apache Commons Exec. In that case, I would prefer Java or Python for the job manager part. I would be happy to hear suggestions for either the former or latter scenario!

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  • Syncing an iPod or iPhone with Cocoa

    - by Koning Baard XIV
    I'm creating an iTunes clone in Cocoa (don't ask why, it's not evil) and I want to be able to sync my iPod with it. This means: music, photos, videos and podcasts. I couldn't really find anything, since Google only shows articles about iPod touch and iPhone programming, but I'm actually creating a desktop application for Mac OS X, and I also want to be able to sync click-wheel iPods. Is there an API or should I read and write directly to the USB port? Can anyone help me? Thanks

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  • c# resize window over display resolution

    - by Sebastian
    I am total newbie in .Net programming so be patient, please ;-). I have problem with resizing window. I want to resize from my app other app's window and take screenshot of it. I do resizing based on this example: http://blogs.geekdojo.net/richard/archive/2003/09/24/181.aspx. But I have a problem. I work on a laptop with 1024x640 pixels screen resolution but I want to resize my window to 1200x1600 px. I can't do that couse display limitations. Is there any tricky solution to resize window for this resolution and take a screenshot of whole window? I've alos tried Sdesk program witch is suggested here: http://stackoverflow.com/questions/445893/create-window-larger-than-desktop-display-resolution. Any help?

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  • WPF - Random hanging with file browser attached behaviour.

    - by Stimul8d
    Hi, I have an attached behavior defined thusly,.. public static class FileBrowserBehaviour { public static bool GetBrowsesOnClick(DependencyObject obj) { return (bool)obj.GetValue(BrowsesOnClickProperty); } public static void SetBrowsesOnClick(DependencyObject obj, bool value) { obj.SetValue(BrowsesOnClickProperty, value); } // Using a DependencyProperty as the backing store for BrowsesOnClick. This enables animation, styling, binding, etc... public static readonly DependencyProperty BrowsesOnClickProperty = DependencyProperty.RegisterAttached("BrowsesOnClick", typeof(bool), typeof(FileBrowserBehaviour), new FrameworkPropertyMetadata(false, new PropertyChangedCallback(BrowsesOnClickChanged))); public static void BrowsesOnClickChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args) { FrameworkElement fe = obj as FrameworkElement; if ((bool)args.NewValue) { fe.PreviewMouseLeftButtonDown += new MouseButtonEventHandler(OpenFileBrowser); } else { fe.PreviewMouseLeftButtonDown -= new MouseButtonEventHandler(OpenFileBrowser); } } static void OpenFileBrowser(object sender, MouseButtonEventArgs e) { var tb = sender as TextBox; if (tb.Text.Length < 1 || tb.Text=="Click to browse..") { OpenFileDialog ofd = new OpenFileDialog(); ofd.Filter = "Executables | *.exe"; if (ofd.ShowDialog() == true) { Debug.WriteLine("Setting textbox text-" + ofd.FileName); tb.Text = ofd.FileName; Debug.WriteLine("Set textbox text"); } } } } It's a nice simple attached behavior which pops open an OpenFileDialog when you click on a textbox and puts the filename in the box when you're done. It works maybe 40% of the time but the rest of the time the whole app hangs. The call stack at this point looks like this - [Managed to Native Transition] WindowsBase.dll!MS.Win32.UnsafeNativeMethods.GetMessageW(ref System.Windows.Interop.MSG msg, System.Runtime.InteropServices.HandleRef hWnd, int uMsgFilterMin, int uMsgFilterMax) + 0x15 bytes WindowsBase.dll!System.Windows.Threading.Dispatcher.GetMessage(ref System.Windows.Interop.MSG msg, System.IntPtr hwnd, int minMessage, int maxMessage) + 0x48 bytes WindowsBase.dll!System.Windows.Threading.Dispatcher.PushFrameImpl(System.Windows.Threading.DispatcherFrame frame = {System.Windows.Threading.DispatcherFrame}) + 0x8b bytes WindowsBase.dll!System.Windows.Threading.Dispatcher.PushFrame(System.Windows.Threading.DispatcherFrame frame) + 0x49 bytes WindowsBase.dll!System.Windows.Threading.Dispatcher.Run() + 0x4c bytes PresentationFramework.dll!System.Windows.Application.RunDispatcher(object ignore) + 0x1e bytes PresentationFramework.dll!System.Windows.Application.RunInternal(System.Windows.Window window) + 0x6f bytes PresentationFramework.dll!System.Windows.Application.Run(System.Windows.Window window) + 0x26 bytes PresentationFramework.dll!System.Windows.Application.Run() + 0x19 bytes Debugatron.exe!Debugatron.App.Main() + 0x5e bytes C# [Native to Managed Transition] [Managed to Native Transition] mscorlib.dll!System.AppDomain.nExecuteAssembly(System.Reflection.Assembly assembly, string[] args) + 0x19 bytes mscorlib.dll!System.Runtime.Hosting.ManifestRunner.Run(bool checkAptModel) + 0x6e bytes mscorlib.dll!System.Runtime.Hosting.ManifestRunner.ExecuteAsAssembly() + 0x84 bytes mscorlib.dll!System.Runtime.Hosting.ApplicationActivator.CreateInstance(System.ActivationContext activationContext, string[] activationCustomData) + 0x65 bytes mscorlib.dll!System.Runtime.Hosting.ApplicationActivator.CreateInstance(System.ActivationContext activationContext) + 0xa bytes mscorlib.dll!System.Activator.CreateInstance(System.ActivationContext activationContext) + 0x3e bytes Microsoft.VisualStudio.HostingProcess.Utilities.dll!Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssemblyDebugInZone() + 0x23 bytes mscorlib.dll!System.Threading.ThreadHelper.ThreadStart_Context(object state) + 0x66 bytes mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state) + 0x6f bytes mscorlib.dll!System.Threading.ThreadHelper.ThreadStart() + 0x44 bytes Now, I've seen this kind of thing before when doing some asynchronous stuff but there's none of that going on at that point. The only thread alive is the UI thread! Also, I always get that last debug statement when it does hang. Can anyone point me in the right direction? This one's driving me crazy!

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  • Advantage of using Thread.Start vs QueueUserWorkItem

    - by Cheeso
    In multithreaded .NET programming, what are the decision criteria for using ThreadPool.QueueUserWorkItem versus starting my own thread via new Thread() and Thread.Start()? In a server app (let's say, an ASP.NET app or a WCF service) I think the ThreadPool is always there and available. What about in a client app, like a WinForms or WPF app? Is there a cost to spin up the thread pool? If I just want 3 or 4 threads to work for a short period on some computation, is it better to QUWI or to Thread.Start().

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  • Noob Rails ? about learning Rails

    - by user271916
    Hi All I have been programming for a while and for the past 3 or 4 months have been learning ruby. I am not an expert by any means but I believe I have the basics down. I decided to start learning RoR and bought the "Agile Web Development with Rails 3rd Edition" and have been dutifully going through the chapters one by one. Currently I am in chapter 8 and have had no problems so far. My question is I know I have learned several things so far and I know that I am starting to get a sense of the Rails framework I have this fear that I am just not learning as much as I should. Some things I get and understand the interconnections while I feel on other things I am just going through the motions and don't fully comprehend the total interconnectivity. Now, there is still a large amount of the book for me to complete. I guess I am just wondering if I complete this book what should I expect to be able to accomplish on my own and what should be my next steps. Thanks

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  • iphone memory leaks and malloc?

    - by Brodie4598
    Okay so im finally to the point where I am testing my iPad App on an actual iPad... One thing that my app does is display a large (2mb) image in a scroll view. This is causing the iPad to get memory warnings. I run the app in the instruments to check for the leak. When I load the image, a leak is detected and i see the following in the allocations: ALl Allocations: 83.9 MB Malloc 48.55 MB: 48.55 MB Malloc 34.63 MB: 34.63 MB What im trying to understand is how to plug the leak obviously, but also why a 2MB image is causing a malloc of 20x that size I am very new to programming in obj-c so im sure this is an obvious thing, but I just cant figure it out. Here is the code:

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  • Overview of PHP shorthand

    - by James Simpson
    I've been programming in PHP for years now, but I've never learned how to use any shorthand. I come across it from time to time in code and have a hard time reading it, so I'd like to learn the different shorthand that exists for the language sot hat I can read it and start saving time/lines by using it, but I can't seem to find a comprehensive overview of all of the shorthand. A Google search pretty much exclusively shows the shorthand for if/else statements, but I know there must be more than just that. By shorthand, I am talking about stuff like: ($var) ? true : false;

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  • How does memory management in Java and C# differ?

    - by David Johnstone
    I was reading through 2010 CWE/SANS Top 25 Most Dangerous Programming Errors and one of the entries is for Buffer Copy without Checking Size of Input. It suggests using a language with features to prevent or mitigate this problem, and says: For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. I was not aware that Java and C# differed in any meaningful way with regard to memory management. How is it that Java is not subject to buffer overflows, while C# only protects against overflows? And how is it possible to disable this protection in C#?

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