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• How to show form in front in C#

  - by corlettk

  Folks, Please does anyone know how to show a Form from an otherwise invisible application, and have it get the focus (i.e. appear on top of other windows)? I'm working in C# .NET 3.5. I suspect I've taken "completely the wrong approach"... I do not Application.Run(new TheForm ()) instead I (new TheForm()).ShowModal()... The Form is basically a modal dialogue, with a few check-boxes; a text-box, and OK and Cancel Buttons. The user ticks a checkbox and types in a description (or whatever) then presses OK, the form disappears and the process reads the user-input from the Form, Disposes it, and continues processing. This works, except when the form is show it doesn't get the focus, instead it appears behind the "host" application, until you click on it in the taskbar (or whatever). This is a most annoying behaviour, which I predict will cause many "support calls", and the existing VB6 version doesn't have this problem, so I'm going backwards in usability... and users won't accept that (and nor should they). So... I'm starting to think I need to rethink the whole shebang... I should show the form up front, as a "normal application" and attach the remainer of the processing to the OK-button-click event. It should work, But that will take time which I don't have (I'm already over time/budget)... so first I really need to try to make the current approach work... even by quick-and-dirty methods. So please does anyone know how to "force" a .NET 3.5 Form (by fair means or fowl) to get the focus? I'm thinking "magic" windows API calls (I know Twilight Zone: This only appears to be an issue at work, we're I'm using Visual Studio 2008 on Windows XP SP3... I've just failed to reproduce the problem with an SSCCE (see below) at home on Visual C# 2008 on Vista Ulimate... This works fine. Huh? WTF? Also, I'd swear that at work yesterday showed the form when I ran the EXE, but not when F5'ed (or Ctrl-F5'ed) straight from the IDE (which I just put up with)... At home the form shows fine either way. Totaly confusterpating! It may or may not be relevant, but Visual Studio crashed-and-burned this morning when the project was running in debug mode and editing the code "on the fly"... it got stuck what I presumed was an endless loop of error messages. The error message was something about "can't debug this project because it is not the current project, or something... So I just killed it off with process explorer. It started up again fine, and even offered to recover the "lost" file, an offer which I accepted. using System; using System.Windows.Forms; namespace ShowFormOnTop { static class Program { [STAThread] static void Main() { Application.EnableVisualStyles(); Application.SetCompatibleTextRenderingDefault(false); //Application.Run(new Form1()); Form1 frm = new Form1(); frm.ShowDialog(); } } } Background: I'm porting an existing VB6 implementation to .NET... It's a "plugin" for a "client" GIS application called MapInfo. The existing client "worked invisibly" and my instructions are "to keep the new version as close as possible to the old version", which works well enough (after years of patching); it's just written in an unsupported language, so we need to port it. About me: I'm pretty much a noob to C# and .NET generally, though I've got a bottoms wiping certificate, I have been a professional programmer for 10 years; So I sort of "know some stuff". Any insights would be most welcome... and Thank you all for taking the time to read this far. Consiseness isn't (apparently) my forte. Cheers. Keith.

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• How can I make this Java code run faster?

  - by Martin Wiboe

  Hello all, I am trying to make a Java port of a simple feed-forward neural network. This obviously involves lots of numeric calculations, so I am trying to optimize my central loop as much as possible. The results should be correct within the limits of the float data type. My current code looks as follows (error handling & initialization removed): /** * Simple implementation of a feedforward neural network. The network supports * including a bias neuron with a constant output of 1.0 and weighted synapses * to hidden and output layers. * * @author Martin Wiboe */ public class FeedForwardNetwork { private final int outputNeurons; // No of neurons in output layer private final int inputNeurons; // No of neurons in input layer private int largestLayerNeurons; // No of neurons in largest layer private final int numberLayers; // No of layers private final int[] neuronCounts; // Neuron count in each layer, 0 is input // layer. private final float[][][] fWeights; // Weights between neurons. // fWeight[fromLayer][fromNeuron][toNeuron] // is the weight from fromNeuron in // fromLayer to toNeuron in layer // fromLayer+1. private float[][] neuronOutput; // Temporary storage of output from previous layer public float[] compute(float[] input) { // Copy input values to input layer output for (int i = 0; i < inputNeurons; i++) { neuronOutput[0][i] = input[i]; } // Loop through layers for (int layer = 1; layer < numberLayers; layer++) { // Loop over neurons in the layer and determine weighted input sum for (int neuron = 0; neuron < neuronCounts[layer]; neuron++) { // Bias neuron is the last neuron in the previous layer int biasNeuron = neuronCounts[layer - 1]; // Get weighted input from bias neuron - output is always 1.0 float activation = 1.0F * fWeights[layer - 1][biasNeuron][neuron]; // Get weighted inputs from rest of neurons in previous layer for (int inputNeuron = 0; inputNeuron < biasNeuron; inputNeuron++) { activation += neuronOutput[layer-1][inputNeuron] * fWeights[layer - 1][inputNeuron][neuron]; } // Store neuron output for next round of computation neuronOutput[layer][neuron] = sigmoid(activation); } } // Return output from network = output from last layer float[] result = new float[outputNeurons]; for (int i = 0; i < outputNeurons; i++) result[i] = neuronOutput[numberLayers - 1][i]; return result; } private final static float sigmoid(final float input) { return (float) (1.0F / (1.0F + Math.exp(-1.0F * input))); } } I am running the JVM with the -server option, and as of now my code is between 25% and 50% slower than similar C code. What can I do to improve this situation? Thank you, Martin Wiboe

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• Testing a Non-blocking Queue

  - by jsw

  I've ported the non-blocking queue psuedocode here to C#. The code below is meant as a near verbatim copy of the paper. What approach would you take to test the implementation? Note: I'm running in VS2010 so I don't have CHESS support yet. using System.Threading; #pragma warning disable 0420 namespace ConcurrentCollections { class QueueNodePointer<T> { internal QueueNode<T> ptr; internal QueueNodePointer() : this(null) { } internal QueueNodePointer(QueueNode<T> ptr) { this.ptr = ptr; } } class QueueNode<T> { internal T value; internal QueueNodePointer<T> next; internal QueueNode() : this(default(T)) { } internal QueueNode(T value) { this.value = value; this.next = new QueueNodePointer<T>(); } } public class ConcurrentQueue<T> { private volatile int count = 0; private QueueNodePointer<T> qhead = new QueueNodePointer<T>(); private QueueNodePointer<T> qtail = new QueueNodePointer<T>(); public ConcurrentQueue() { var node = new QueueNode<T>(); node.next.ptr = null; this.qhead.ptr = this.qtail.ptr = node; } public int Count { get { return this.count; } } public void Enqueue(T value) { var node = new QueueNode<T>(value); node.next.ptr = null; QueueNodePointer<T> tail; QueueNodePointer<T> next; while (true) { tail = this.qtail; next = tail.ptr.next; if (tail == this.qtail) { if (next.ptr == null) { var newtail = new QueueNodePointer<T>(node); if (Interlocked.CompareExchange(ref tail.ptr.next, newtail, next) == next) { Interlocked.Increment(ref this.count); break; } else { Interlocked.CompareExchange(ref this.qtail, new QueueNodePointer<T>(next.ptr), tail); } } } } Interlocked.CompareExchange(ref this.qtail, new QueueNodePointer<T>(node), tail); } public T Dequeue() { T value; while (true) { var head = this.qhead; var tail = this.qtail; var next = head.ptr.next; if (head == this.qhead) { if (head.ptr == tail.ptr) { if (next.ptr == null) { return default(T); } Interlocked.CompareExchange(ref this.qtail, new QueueNodePointer<T>(next.ptr), tail); } else { value = next.ptr.value; var newhead = new QueueNodePointer<T>(next.ptr); if (Interlocked.CompareExchange(ref this.qhead, newhead, head) == head) { Interlocked.Decrement(ref this.count); break; } } } } return value; } } } #pragma warning restore 0420

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• Hidden UIView Orientation Change / Layout problems

  - by gargantaun

  The Problem: I have two View Controllers loaded into a root View Controller. Both sub view layouts respond to orientation changes. I switch between the two views using [UIView transformationFromView:...]. Both sub views work fine on their own, but if... Views are swapped Orientation Changes Views are swapped again the View that was previously hidden has serious layout problems. The more I repeat these steps the worse the problem gets. Implementation Details I have three viewsControllers. MyAppViewController A_ViewController B_ViewController A & B ViewControllers have a background image each, and a UIWebView and an AQGridView respectively. To give you an example of how i'm setting it all up, here's the loadView method for A_ViewController... - (void)loadView { [super loadView]; // background image // Should fill the screen and resize on orientation changes UIImageView *bg = [[UIImageView alloc] initWithFrame:self.view.bounds]; bg.contentMode = UIViewContentModeCenter; bg.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth; bg.image = [UIImage imageNamed:@"fuzzyhalo.png"]; [self.view addSubview:bg]; // frame for webView // Should have a margin of 34 on all sides and resize on orientation changes CGRect webFrame = self.view.bounds; webFrame.origin.x = 34; webFrame.origin.y = 34; webFrame.size.width = webFrame.size.width - 68; webFrame.size.height = webFrame.size.height - 68; projectView = [[UIWebView alloc] initWithFrame:webFrame]; projectView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth; [self.view addSubview:projectView]; } For the sake of brevity, the AQGridView in B_ViewController is set up pretty much the same way. Now both these views work fine on their own. However, I use both of them in the AppViewController like this... - (void)loadView { [super loadView]; self.view.autoresizesSubviews = YES; [self setWantsFullScreenLayout:YES]; webView = [[WebProjectViewController alloc] init]; [self.view addSubview:webView.view]; mainMenu = [[GridViewController alloc] init]; [self.view addSubview:mainMenu.view]; activeView = mainMenu; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(switchViews:) name:SWAPVIEWS object:nil]; } and I switch betweem the two views using my own switchView method like this - (void) switchViews:(NSNotification*)aNotification; { NSString *type = [aNotification object]; if ([type isEqualToString:MAINMENU]){ [UIView transitionFromView:activeView.view toView:mainMenu.view duration:0.75 options:UIViewAnimationOptionTransitionFlipFromRight completion:nil]; activeView = mainMenu; } if ([type isEqualToString:WEBVIEW]) { [UIView transitionFromView:activeView.view toView:webView.view duration:0.75 options:UIViewAnimationOptionTransitionFlipFromLeft completion:nil]; activeView = webView; } // These don't seem to do anything //[mainMenu.view setNeedsLayout]; //[webView.view setNeedsLayout]; } I'm fumbling my way through this, and I suspect a lot of what i've done is implemented incorrectly so please feel free to point out anything that should be done differently, I need the input. But my primary concern is to understand what's causing the layout problems. Here's two images which illustrate the nature of the layout issues... UPDATE: I just noticed that when the orientation is landscape, the transition flips vertically, when I would expect it to be horizontal. I don't know wether that's a clue as to what might be going wrong. Switch to the other view... change orientation.... switch back....

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• XNA: Best way to load and read a XML file?

  - by Rosarch

  I'm having difficulty doing this seemingly simple task. I want to load XML files with the same ease of loading art assets: content = new ContentManager(Services); content.RootDirectory = "Content"; Texture2d background = content.Load<Texture2D>("images\\ice"); I'm not sure how to do this. This tutorial seems helpful, but how do I get a StorageDevice instance? I do have something working now, but it feels pretty hacky: public IDictionary<string, string> Get(string typeName) { IDictionary<String, String> result = new Dictionary<String, String>(); xmlReader.Read(); // get past the XML declaration string element = null; string text = null; while (xmlReader.Read()) { switch (xmlReader.NodeType) { case XmlNodeType.Element: element = xmlReader.Name; break; case XmlNodeType.Text: text = xmlReader.Value; break; } if (text != null && element != null) { result[element] = text; text = null; element = null; } } return result; } I apply this to the following XML file: <?xml version="1.0" encoding="utf-8" ?> <zombies> <zombie> <health>100</health> <positionX>23</positionX> <positionY>12</positionY> <speed>2</speed> </zombie> </zombies> And it is able to pass this unit test: internal virtual IPersistentState CreateIPersistentState(string fullpath) { IPersistentState target = new ReadWriteXML(File.Open(fullpath, FileMode.Open)); return target; } /// <summary> ///A test for Get with one zombie. ///</summary> //[TestMethod()] public void SimpleGetTest() { string fullPath = "C:\\pathTo\\Data\\SavedZombies.xml"; IPersistentState target = CreateIPersistentState(fullPath); string typeName = "zombie"; IDictionary<string, string> expected = new Dictionary<string, string>(); expected["health"] = "100"; expected["positionX"] = "23"; expected["positionY"] = "12"; expected["speed"] = "2"; IDictionary<string, string> actual = target.Get(typeName); foreach (KeyValuePair<string, string> entry in expected) { Assert.AreEqual(entry.Value, expected[entry.Key]); } } Downsides to the current approach: file loading is done poorly, and matching keys to values seems like it's way more effort than necessary. Also, I suspect this approach would fall apart with more than one entry in the XML. I can't imagine that this is the optimal implementation.

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• NSUserDefaults loses 3 rows each time it's called

  - by Jeff Decker

  Hello Everyone! Brand new programmer here, so off-topic help/constructive criticism welcome. I am saving a default state (such as "New York") in a UIPickerView which is in a FlipSideView. It certainly saves for the first and second time I check to make sure it's the same state (I am clicking "done" and then "info" repeatedly), but on the third check the picker has moved up three states (to "New Hampshire") and then every time I check the picker progresses three more states. Here's the .h and .m files of the FlipSideViewController: #import <UIKit/UIKit.h> import "Calculator.h" @protocol FlipsideViewControllerDelegate; @interface FlipsideViewController : UIViewController { id delegate; UIPickerView *myPickerView; NSArray *pickerViewArray; } @property (nonatomic, assign) id delegate; @property (nonatomic, retain) UIPickerView *myPickerView; @property (nonatomic, retain) NSArray *pickerViewArray; (IBAction)done; @end @protocol FlipsideViewControllerDelegate - (void)flipsideViewControllerDidFinish:(FlipsideViewController *)controller; @end import "FlipsideViewController.h" @implementation FlipsideViewController @synthesize delegate; @synthesize myPickerView, pickerViewArray; -(CGRect)pickerFrameWithSize:(CGSize)size;{ CGRect screenRect = [[UIScreen mainScreen] applicationFrame]; CGRect pickerRect = CGRectMake( 0.0, screenRect.size.height - size.height, size.width, size.height); return pickerRect; } (void)viewDidLoad { [super viewDidLoad]; self.view.backgroundColor = [UIColor viewFlipsideBackgroundColor]; [self createPicker]; } -(void)viewWillAppear:(BOOL)animated;{ [super viewWillAppear:NO]; NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]; [myPickerView selectRow:[defaults integerForKey:@"pickerRow"] inComponent:0 animated:NO]; } -(void)createPicker;{ pickerViewArray = [[NSArray arrayWithObjects: @"Alabama",@"Alaska", @"Arizona",@"Arkansas",@"California",@"Colorado",@"Connecticut",@"Delaware", @"District of Columbia",@"Florida",@"Georgia",@"Hawaii",@"Idaho",@"Illinois",@"Indiana",@"Iowa", @"Kansas",@"Kentucky",@"Louisiana",@"Maine",@"Maryland",@"Massachusetts",@"Michigan", @"Minnesota",@"Mississippi",@"Missouri",@"Montana",@"Nebraska",@"Nevada",@"New Hampshire",@"New Jersey", @"New Mexico",@"New York",@"North Carolina",@"North Dakota",@"Ohio",@"Oklahoma", @"Oregon",@"Pennsylvania",@"Rhode Island",@"South Carolina",@"South Dakota",@"Tennessee", @"Texas",@"Utah",@"Vermont",@"Virginia",@"Washington",@"West Virginia",@"Wisconsin",@"Wyoming", nil] retain]; myPickerView = [[UIPickerView alloc] initWithFrame:CGRectZero]; CGSize pickerSize = [myPickerView sizeThatFits:CGSizeZero]; myPickerView.frame = [self pickerFrameWithSize:pickerSize]; myPickerView.autoresizingMask = UIViewAutoresizingFlexibleWidth; myPickerView.showsSelectionIndicator = YES; myPickerView.delegate = self; myPickerView.dataSource = self; [self.view addSubview:myPickerView]; } (IBAction)done { [self.delegate flipsideViewControllerDidFinish:self]; } pragma mark - pragma mark UIPickerViewDataSource (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component { NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]; [defaults setInteger:row forKey:@"pickerRow"]; [defaults setObject:[pickerViewArray objectAtIndex:row] forKey:@"pickerString"]; return [pickerViewArray objectAtIndex:row]; } (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component { NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]; [defaults setInteger:row forKey:@"pickerRow"]; [defaults setObject:[pickerViewArray objectAtIndex:row] forKey:@"pickerString"]; } (CGFloat)pickerView:(UIPickerView *)pickerView widthForComponent:(NSInteger)component { return 240.0; } (CGFloat)pickerView:(UIPickerView *)pickerView rowHeightForComponent:(NSInteger)component { return 40.0; } (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component { return [pickerViewArray count]; } (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView { return 1; } call me mystified! Thanks for any help. Please let me know if I can make myself more clear...

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• Explicitly instantiating a generic member function of a generic structure

  - by Dennis Zickefoose

  I have a structure with a template parameter, Stream. Within that structure, there is a function with its own template parameter, Type. If I try to force a specific instance of the function to be generated and called, it works fine, if I am in a context where the exact type of the structure is known. If not, I get a compile error. This feels like a situation where I'm missing a typename, but there are no nested types. I suspect I'm missing something fundamental, but I've been staring at this code for so long all I see are redheads, and frankly writing code that uses templates has never been my forte. The following is the simplest example I could come up with that illustrates the issue. #include <iostream> template<typename Stream> struct Printer { Stream& str; Printer(Stream& str_) : str(str_) { } template<typename Type> Stream& Exec(const Type& t) { return str << t << std::endl; } }; template<typename Stream, typename Type> void Test1(Stream& str, const Type& t) { Printer<Stream> out = Printer<Stream>(str); /****** vvv This is the line the compiler doesn't like vvv ******/ out.Exec<bool>(t); /****** ^^^ That is the line the compiler doesn't like ^^^ ******/ } template<typename Type> void Test2(const Type& t) { Printer<std::ostream> out = Printer<std::ostream>(std::cout); out.Exec<bool>(t); } template<typename Stream, typename Type> void Test3(Stream& str, const Type& t) { Printer<Stream> out = Printer<Stream>(str); out.Exec(t); } int main() { Test2(5); Test3(std::cout, 5); return 0; } As it is written, gcc-4.4 gives the following: test.cpp: In function 'void Test1(Stream&, const Type&)': test.cpp:22: error: expected primary-expression before 'bool' test.cpp:22: error: expected ';' before 'bool' Test2 and Test3 both compile cleanly, and if I comment out Test1 the program executes, and I get "1 5" as I expect. So it looks like there's nothing wrong with the idea of what I want to do, but I've botched something in the implementation. If anybody could shed some light on what I'm overlooking, it would be greatly appreciated.

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• Kindle Fire: PopupMenu$OrientationChangeListener leak

  - by dokkaebi

  I have a little popup menu that anchors on a button in the action bar. This works well on 3.0/3.1 Xoom and Galaxy tabs, and a 4.1 Nexus 7. However, on a 7" Fire HD (this one), I get an error about a leaked intent receiver when exiting the application. The error occurs only if the menu was not opened during that run. There is no mention of OrientationChangeListener in the one copy of the source I've found; I suspect Amazon has a different implementation. Questions: Has anyone encountered this? Does anyone know of a workaround or a fix? (Where) can I find Amazon's source code? Finally, (shudder) how important is it that I don't leak a receiver on application exit? Here is the menu xml: <?xml version="1.0" encoding="utf-8"?> <menu xmlns:android="http://schemas.android.com/apk/res/android"> <item android:id="@+id/menu_profile" android:title="@string/menu_item_profile" ></item> <item android:id="@+id/menu_logout" android:title="@string/menu_item_logout" ></item> </menu> This is where I register it: @Override public boolean onCreateOptionsMenu(Menu menu) { super.onCreateOptionsMenu(menu); MenuInflater inflater = getMenuInflater(); inflater.inflate(R.menu.main_menu, menu); MenuItem login = menu.findItem(R.id.menu_login); Button button = (Button) login.getActionView().findViewById(R.id.login); button.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { profileMenu.show(); } }); // profileMenu is an instance field profileMenu = new PopupMenu(this, button); inflater.inflate(R.menu.profile_menu, profileMenu.getMenu()); profileMenu.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() { public boolean onMenuItemClick(MenuItem item) { // there was code here, but I removed it all and the problem persists return false; } }); return true; } Here is the full stack trace: 10-21 20:55:28.461: E/ActivityThread(4526): Activity **.app.ListActivity has leaked IntentReceiver android.widget.PopupMenu$OrientationChangeListener@422d77e0 that was originally registered here. Are you missing a call to unregisterReceiver()? 10-21 20:55:28.461: E/ActivityThread(4526): android.app.IntentReceiverLeaked: Activity **.app.ListActivity has leaked IntentReceiver android.widget.PopupMenu$OrientationChangeListener@422d77e0 that was originally registered here. Are you missing a call to unregisterReceiver()? 10-21 20:55:28.461: E/ActivityThread(4526): at android.app.LoadedApk$ReceiverDispatcher.<init>(LoadedApk.java:826) 10-21 20:55:28.461: E/ActivityThread(4526): at android.app.LoadedApk.getReceiverDispatcher(LoadedApk.java:621) 10-21 20:55:28.461: E/ActivityThread(4526): at android.app.ContextImpl.registerReceiverInternal(ContextImpl.java:1072) 10-21 20:55:28.461: E/ActivityThread(4526): at android.app.ContextImpl.registerReceiver(ContextImpl.java:1059) 10-21 20:55:28.461: E/ActivityThread(4526): at android.app.ContextImpl.registerReceiver(ContextImpl.java:1053) 10-21 20:55:28.461: E/ActivityThread(4526): at android.content.ContextWrapper.registerReceiver(ContextWrapper.java:357) 10-21 20:55:28.461: E/ActivityThread(4526): at android.widget.PopupMenu.<init>(PopupMenu.java:81) 10-21 20:55:28.461: E/ActivityThread(4526): at **.app.ListActivity.onCreateOptionsMenu(ListActivity.java:350) 10-21 20:55:28.461: E/ActivityThread(4526): at android.app.Activity.onCreatePanelMenu(Activity.java:2558) 10-21 20:55:28.461: E/ActivityThread(4526): at com.android.internal.policy.impl.PhoneWindow.preparePanel(PhoneWindow.java:398) 10-21 20:55:28.461: E/ActivityThread(4526): at com.android.internal.policy.impl.PhoneWindow.invalidatePanelMenu(PhoneWindow.java:883) 10-21 20:55:28.461: E/ActivityThread(4526): at com.android.internal.policy.impl.PhoneWindow$2.run(PhoneWindow.java:3008) 10-21 20:55:28.461: E/ActivityThread(4526): at android.os.Handler.handleCallback(Handler.java:605) 10-21 20:55:28.461: E/ActivityThread(4526): at android.os.Handler.dispatchMessage(Handler.java:92) 10-21 20:55:28.461: E/ActivityThread(4526): at android.os.Looper.loop(Looper.java:137) 10-21 20:55:28.461: E/ActivityThread(4526): at android.app.ActivityThread.main(ActivityThread.java:4491) 10-21 20:55:28.461: E/ActivityThread(4526): at java.lang.reflect.Method.invokeNative(Native Method) 10-21 20:55:28.461: E/ActivityThread(4526): at java.lang.reflect.Method.invoke(Method.java:511) 10-21 20:55:28.461: E/ActivityThread(4526): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 10-21 20:55:28.461: E/ActivityThread(4526): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 10-21 20:55:28.461: E/ActivityThread(4526): at dalvik.system.NativeStart.main(Native Method)

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• Covariance and Contravariance in C#

  - by edalorzo

  I will start by saying that I am Java developer learning to program in C#. As such I do comparisons of what I know with what I am learning. I have been playing with C# generics for a few hours now, and I have been able to reproduce the same things I know in Java in C#, with the exception of a couple of examples using covariance and contravariance. The book I am reading is not very good in the subject. I will certainly seek more info on the web, but while I do that, perhaps you can help me find a C# implementation for the following Java code. An example is worth a thousand words, and I was hoping that by looking a good code sample I will be able to assimilate this more rapidly. Covariance In Java I can do something like this: public static double sum(List<? extends Number> numbers) { double summation = 0.0; for(Number number : numbers){ summation += number.doubleValue(); } return summation; } I can use this code as follows: List<Integer> myInts = asList(1,2,3,4,5); List<Double> myDoubles = asList(3.14, 5.5, 78.9); List<Long> myLongs = asList(1L, 2L, 3L); double result = 0.0; result = sum(myInts); result = sum(myDoubles) result = sum(myLongs); Now I did discover that C# supports covariance/contravariance only on interfaces and as long as they have been explicitly declared to do so (out). I think I was not able to reproduce this case, because I could not find a common ancestor of all numbers, but I believe that I could have used IEnumerable to implement such thing if a common ancestor exists. Since IEnumerable is a covariant type. Right? Any thoughts on how to implement the list above? Just point me into the right direction. Is there any common ancestor of all numeric types? Contravariance The contravariance example I tried was the following. In Java I can do this to copy one list into another. public static void copy(List<? extends Number> source, List<? super Number> destiny){ for(Number number : source) { destiny.add(number); } } Then I could use it with contravariant types as follows: List<Object> anything = new ArrayList<Object>(); List<Integer> myInts = asList(1,2,3,4,5); copy(myInts, anything); My basic problem, trying to implement this in C# is that I could not find an interface that was both covariant and contravariant at the same time, as it is case of List in my example above. Maybe it can be done with two different interface in C#. Any thoughts on how to implement this? Thank you very much to everyone for any answers you can contribute. I am pretty sure I will learn a lot from any example you can provide.

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• Use QuickCheck by generating primes

  - by Dan

  Background For fun, I'm trying to write a property for quick-check that can test the basic idea behind cryptography with RSA. Choose two distinct primes, p and q. Let N = p*q e is some number relatively prime to (p-1)(q-1) (in practice, e is usually 3 for fast encoding) d is the modular inverse of e modulo (p-1)(q-1) For all x such that 1 < x < N, it is always true that (x^e)^d = x modulo N In other words, x is the "message", raising it to the eth power mod N is the act of "encoding" the message, and raising the encoded message to the dth power mod N is the act of "decoding" it. (The property is also trivially true for x = 1, a case which is its own encryption) Code Here are the methods I have coded up so far: import Test.QuickCheck -- modular exponentiation modExp :: Integral a => a -> a -> a -> a modExp y z n = modExp' (y `mod` n) z `mod` n where modExp' y z | z == 0 = 1 | even z = modExp (y*y) (z `div` 2) n | odd z = (modExp (y*y) (z `div` 2) n) * y -- relatively prime rPrime :: Integral a => a -> a -> Bool rPrime a b = gcd a b == 1 -- multiplicative inverse (modular) mInverse :: Integral a => a -> a -> a mInverse 1 _ = 1 mInverse x y = (n * y + 1) `div` x where n = x - mInverse (y `mod` x) x -- just a quick way to test for primality n `divides` x = x `mod` n == 0 primes = 2:filter isPrime [3..] isPrime x = null . filter (`divides` x) $ takeWhile (\y -> y*y <= x) primes -- the property prop_rsa (p,q,x) = isPrime p && isPrime q && p /= q && x > 1 && x < n && rPrime e t ==> x == (x `powModN` e) `powModN` d where e = 3 n = p*q t = (p-1)*(q-1) d = mInverse e t a `powModN` b = modExp a b n (Thanks, google and random blog, for the implementation of modular multiplicative inverse) Question The problem should be obvious: there are way too many conditions on the property to make it at all usable. Trying to invoke quickCheck prop_rsa in ghci made my terminal hang. So I've poked around the QuickCheck manual a bit, and it says: Properties may take the form forAll <generator> $ \<pattern> -> <property> How do I make a <generator> for prime numbers? Or with the other constraints, so that quickCheck doesn't have to sift through a bunch of failed conditions? Any other general advice (especially regarding QuickCheck) is welcome.

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• iphone app: delegate not responding

  - by Fiona

  Hi guys.. So i'm very new to this iphone development stuff.... and i'm stuck. I'm building an app that connects to the twitter api. However when the connectionDidFinishLoading method gets called, it doesn't seem to recognise the delegate. Here's the source code of the request class: import "OnePageRequest.h" @implementation OnePageRequest @synthesize username; @synthesize password; @synthesize receivedData; @synthesize delegate; @synthesize callback; @synthesize errorCallBack; @synthesize contactsArray; -(void)friends_timeline:(id)requestDelegate requestSelector:(SEL)requestSelector{ //set the delegate and selector self.delegate = requestDelegate; self.callback = requestSelector; //Set up the URL of the request to send to twitter!! NSURL *url = [NSURL URLWithString:@"http://twitter.com/statuses/friends_timeline.xml"]; [self request:url]; } -(void)request:(NSURL *) url{ theRequest = [[NSMutableURLRequest alloc] initWithURL:url]; theConnection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self]; if (theConnection){ //Create the MSMutableData that will hold the received data. //receivedData is declared as a method instance elsewhere receivedData=[[NSMutableData data] retain]; }else{ //errorMessage.text = @"Error connecting to twitter!!"; } } -(void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge{ if ([challenge previousFailureCount] == 0){ NSLog(@"username: %@ ",[self username]); NSLog(@"password: %@ ",[self password]); NSURLCredential *newCredential = [NSURLCredential credentialWithUser:[self username] password:[self password] persistence:NSURLCredentialPersistenceNone]; [[challenge sender] useCredential:newCredential forAuthenticationChallenge:challenge]; } else { [[challenge sender] cancelAuthenticationChallenge:challenge]; NSLog(@"Invalid Username or password!"); } } -(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{ [receivedData setLength:0]; } -(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{ [receivedData appendData:data]; } -(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{ [theConnection release]; [receivedData release]; [theRequest release]; NSLog(@"Connection failed. Error: %@ %@", [error localizedDescription], [[error userInfo] objectForKey:NSErrorFailingURLStringKey]); if(errorCallBack){ [delegate performSelector:errorCallBack withObject:error]; } } -(void)connectionDidFinishLoading:(NSURLConnection *)connection{ if (delegate && callback){ if([delegate respondsToSelector:[self callback]]){ [delegate performSelector:[self callback] withObject:receivedData]; }else{ NSLog(@"No response from delegate!"); } } [theConnection release]; [theRequest release]; [receivedData release]; } Here's the .h: @interface OnePageRequest : NSObject { NSString *username; NSString *password; NSMutableData *receivedData; NSURLRequest *theRequest; NSURLConnection *theConnection; id delegate; SEL callback; SEL errorCallBack; NSMutableArray *contactsArray; } @property (nonatomic,retain) NSString *username; @property (nonatomic,retain) NSString *password; @property (nonatomic,retain) NSMutableData *receivedData; @property (nonatomic,retain) id delegate; @property (nonatomic) SEL callback; @property (nonatomic) SEL errorCallBack; @property (nonatomic,retain) NSMutableArray *contactsArray; -(void)friends_timeline:(id)requestDelegate requestSelector:(SEL)requestSelector; -(void)request:(NSURL *) url; @end In the method: connectionDidFinishLoading, the following never gets executed: [delegate performSelector:[self callback] withObject:receivedData]; Instead I get the message: "No response from delegate" Anyone see what I'm doing wrong?! or what might be causing the problem? Regards, Fiona

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• One letter game problem?

  - by Alex K

  Recently at a job interview I was given the following problem: Write a script capable of running on the command line as python It should take in two words on the command line (or optionally if you'd prefer it can query the user to supply the two words via the console). Given those two words: a. Ensure they are of equal length b. Ensure they are both words present in the dictionary of valid words in the English language that you downloaded. If so compute whether you can reach the second word from the first by a series of steps as follows a. You can change one letter at a time b. Each time you change a letter the resulting word must also exist in the dictionary c. You cannot add or remove letters If the two words are reachable, the script should print out the path which leads as a single, shortest path from one word to the other. You can /usr/share/dict/words for your dictionary of words. My solution consisted of using breadth first search to find a shortest path between two words. But apparently that wasn't good enough to get the job :( Would you guys know what I could have done wrong? Thank you so much. import collections import functools import re def time_func(func): import time def wrapper(*args, **kwargs): start = time.time() res = func(*args, **kwargs) timed = time.time() - start setattr(wrapper, 'time_taken', timed) return res functools.update_wrapper(wrapper, func) return wrapper class OneLetterGame: def __init__(self, dict_path): self.dict_path = dict_path self.words = set() def run(self, start_word, end_word): '''Runs the one letter game with the given start and end words. ''' assert len(start_word) == len(end_word), \ 'Start word and end word must of the same length.' self.read_dict(len(start_word)) path = self.shortest_path(start_word, end_word) if not path: print 'There is no path between %s and %s (took %.2f sec.)' % ( start_word, end_word, find_shortest_path.time_taken) else: print 'The shortest path (found in %.2f sec.) is:\n=> %s' % ( self.shortest_path.time_taken, ' -- '.join(path)) def _bfs(self, start): '''Implementation of breadth first search as a generator. The portion of the graph to explore is given on demand using get_neighboors. Care was taken so that a vertex / node is explored only once. ''' queue = collections.deque([(None, start)]) inqueue = set([start]) while queue: parent, node = queue.popleft() yield parent, node new = set(self.get_neighbours(node)) - inqueue inqueue = inqueue | new queue.extend([(node, child) for child in new]) @time_func def shortest_path(self, start, end): '''Returns the shortest path from start to end using bfs. ''' assert start in self.words, 'Start word not in dictionnary.' assert end in self.words, 'End word not in dictionnary.' paths = {None: []} for parent, child in self._bfs(start): paths[child] = paths[parent] + [child] if child == end: return paths[child] return None def get_neighbours(self, word): '''Gets every word one letter away from the a given word. We do not keep these words in memory because bfs accesses a given vertex only once. ''' neighbours = [] p_word = ['^' + word[0:i] + '\w' + word[i+1:] + '$' for i, w in enumerate(word)] p_word = '|'.join(p_word) for w in self.words: if w != word and re.match(p_word, w, re.I|re.U): neighbours += [w] return neighbours def read_dict(self, size): '''Loads every word of a specific size from the dictionnary into memory. ''' for l in open(self.dict_path): l = l.decode('latin-1').strip().lower() if len(l) == size: self.words.add(l) if __name__ == '__main__': import sys if len(sys.argv) not in [3, 4]: print 'Usage: python one_letter_game.py start_word end_word' else: g = OneLetterGame(dict_path = '/usr/share/dict/words') try: g.run(*sys.argv[1:]) except AssertionError, e: print e

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• Android: HttpURLConnection not working properly

  - by giorgiline

  I'm trying to get the cookies from a website after sending user credentials through a POST Request an it seems that it doesn't work in android this way. ¿Am I doing something bad?. Please help. I've searched here in different posts but there's no useful answer. It's curious that this run in a desktop Java implementation it works perfect but it crashes in Android platform. And it is exactly the same code, specifically when calling HttpURLConnection.getHeaderFields(), it also happens with other member methods. It's a simple code and I don't know why the hell isn't working. DESKTOP CODE: This goes just in the main() HttpURLConnection connection = null; OutputStream out = null; try { URL url = new URL("http://www.XXXXXXXX.php"); String charset = "UTF-8"; String postback = "1"; String user = "XXXXXXXXX"; String password = "XXXXXXXX"; String rememberme = "on"; String query = String.format("postback=%s&user=%s&password=%s&rememberme=%s" , URLEncoder.encode(postback, charset) , URLEncoder.encode(user,charset) , URLEncoder.encode(password, charset) , URLEncoder.encode(rememberme, charset)); connection = (HttpURLConnection)url.openConnection(); connection.setRequestMethod("POST"); connection.setRequestProperty("Accept-Charset", charset); connection.setDoOutput(true); connection.setFixedLengthStreamingMode(query.length()); out = connection.getOutputStream (); out.write(query.getBytes(charset)); if (connection.getHeaderFields() == null){ System.out.println("Header null"); }else{ for (String cookie: connection.getHeaderFields().get("Set-Cookie")){ System.out.println(cookie.split(";", 2)[0]); } } } catch (IOException e){ e.printStackTrace(); } finally { try { out.close();} catch (IOException e) { e.printStackTrace();} connection.disconnect(); } So the output is: login_key=20ad8177db4eca3f057c14a64bafc2c9 FASID=cabf20cc471fcacacdc7dc7e83768880 track=30c8183e4ebbe8b3a57b583166326c77 client-data=%7B%22ism%22%3Afalse%2C%22showm%22%3Afalse%2C%22ts%22%3A1349189669%7D ANDROID CODE: This goes inside doInBackground AsyncTask body HttpURLConnection connection = null; OutputStream out = null; try { URL url = new URL("http://www.XXXXXXXXXXXXXX.php"); String charset = "UTF-8"; String postback = "1"; String user = "XXXXXXXXX"; String password = "XXXXXXXX"; String rememberme = "on"; String query = String.format("postback=%s&user=%s&password=%s&rememberme=%s" , URLEncoder.encode(postback, charset) , URLEncoder.encode(user,charset) , URLEncoder.encode(password, charset) , URLEncoder.encode(rememberme, charset)); connection = (HttpURLConnection)url.openConnection(); connection.setRequestMethod("POST"); connection.setRequestProperty("Accept-Charset", charset); connection.setDoOutput(true); connection.setFixedLengthStreamingMode(query.length()); out = connection.getOutputStream (); out.write(query.getBytes(charset)); if (connection.getHeaderFields() == null){ Log.v(TAG, "Header null"); }else{ for (String cookie: connection.getHeaderFields().get("Set-Cookie")){ Log.v(TAG, cookie.split(";", 2)[0]); } } } catch (IOException e){ e.printStackTrace(); } finally { try { out.close();} catch (IOException e) { e.printStackTrace();} connection.disconnect(); } And here there is no output, it seems that connection.getHeaderFields() doesn't return result. It takes al least 30 seconds to show the Log: 10-02 16:56:25.918: V/class com.giorgi.myproject.activities.HomeActivity(2596): Header null

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• DTGridView losting content while scrolling

  - by Wim Haanstra

  I am using DTGridView from the DTKit by Daniel Tull. I implemented it in a very simple ViewController and the test I am doing is to place a button in the last row of the grid, which should add another row to the grid (and therefor moving the button to a row beneath it). The problem is, when I click the button a couple of times and then start scrolling, the grid seems to lose its content. As I am not completly sure this is a bug in the grid, but more in my code, I hope you guys can help me out and track down the bug. First I have my header file, which is quite simple, because this is a test: #import <UIKit/UIKit.h> #import "DTGridView.h" @interface TestController : UIViewController <DTGridViewDelegate, DTGridViewDataSource> { DTGridView* thumbGrid; } @end I declare a DTGridView, which will be my grid, where I want to put content in. Now, my code file: #import "TestController.h" @implementation TestController int rows = 1; - (NSInteger)numberOfRowsInGridView:(DTGridView *)gridView { return rows; } - (NSInteger)numberOfColumnsInGridView:(DTGridView *)gridView forRowWithIndex:(NSInteger)index { if (index == rows - 1) return 1; else return 3; } - (CGFloat)gridView:(DTGridView *)gridView heightForRow:(NSInteger)rowIndex { return 57.0f; } - (CGFloat)gridView:(DTGridView *)gridView widthForCellAtRow:(NSInteger)rowIndex column:(NSInteger)columnIndex { if (rowIndex == rows - 1) return 320.0f; else return 106.6f; } - (DTGridViewCell *)gridView:(DTGridView *)gridView viewForRow:(NSInteger)rowIndex column:(NSInteger)columnIndex { DTGridViewCell *view = [[gridView dequeueReusableCellWithIdentifier:@"thumbcell"] retain]; if (!view) view = [[DTGridViewCell alloc] initWithReuseIdentifier:@"thumbcell"]; if (rowIndex == rows - 1) { UIButton* btnLoadMoreItem = [[UIButton alloc] initWithFrame:CGRectMake(10, 0, 301, 57)]; [btnLoadMoreItem setTitle:[NSString stringWithFormat:@"Button %d", rowIndex] forState:UIControlStateNormal]; [btnLoadMoreItem.titleLabel setFont:[UIFont boldSystemFontOfSize:20]]; [btnLoadMoreItem setBackgroundImage:[[UIImage imageNamed:@"big-green-button.png"] stretchableImageWithLeftCapWidth:10.0 topCapHeight:0.0] forState:UIControlStateNormal]; [btnLoadMoreItem addTarget:self action:@selector(selectLoadMoreItems:) forControlEvents:UIControlEventTouchUpInside]; [view addSubview:btnLoadMoreItem]; [btnLoadMoreItem release]; } else { UILabel* label = [[UILabel alloc] initWithFrame:CGRectMake(10,0,100,57)]; label.text = [NSString stringWithFormat:@"%d x %d", rowIndex, columnIndex]; [view addSubview:label]; [label release]; } return [view autorelease]; } - (void) selectLoadMoreItems:(id) sender { rows++; [thumbGrid setNeedsDisplay]; } - (void)viewDidLoad { [super viewDidLoad]; thumbGrid = [[DTGridView alloc] initWithFrame:CGRectMake(0,0, 320, 320)]; thumbGrid.dataSource = self; thumbGrid.gridDelegate = self; [self.view addSubview:thumbGrid]; } - (void)viewDidUnload { [super viewDidUnload]; } - (void)dealloc { [super dealloc]; } @end I implement all the methods for the DataSource, which seem to work. The grid is filled with as many rows as my int 'rows' ( +1 ) has. The last row does NOT contain 3 columns, but just one. That cell contains a button which (when pressed) adds 1 to the 'rows' integer. The problem starts, when it starts reusing cells (I am guessing) and content start disappearing. When I scroll back up, the UILabels I am putting in the cells are gone. Is there some bug, code error, mistake, dumb-ass-move I am missing here? Hope anyone can help.

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• How do I use constructor dependency injection to supply Models from a collection to their ViewModels

  - by GraemeF

  I'm using constructor dependency injection in my WPF application and I keep running into the following pattern, so would like to get other people's opinion on it and hear about alternative solutions. The goal is to wire up a hierarchy of ViewModels to a similar hierarchy of Models, so that the responsibility for presenting the information in each model lies with its own ViewModel implementation. (The pattern also crops up under other circumstances but MVVM should make for a good example.) Here's a simplified example. Given that I have a model that has a collection of further models: public interface IPerson { IEnumerable<IAddress> Addresses { get; } } public interface IAddress { } I would like to mirror this hierarchy in the ViewModels so that I can bind a ListBox (or whatever) to a collection in the Person ViewModel: public interface IPersonViewModel { ObservableCollection<IAddressViewModel> Addresses { get; } void Initialize(); } public interface IAddressViewModel { } The child ViewModel needs to present the information from the child Model, so it's injected via the constructor: public class AddressViewModel : IAddressViewModel { private readonly IAddress _address; public AddressViewModel(IAddress address) { _address = address; } } The question is, what is the best way to supply the child Model to the corresponding child ViewModel? The example is trivial, but in a typical real case the ViewModels have more dependencies - each of which has its own dependencies (and so on). I'm using Unity 1.2 (although I think the question is relevant across the other IoC containers), and I am using Caliburn's view strategies to automatically find and wire up the appropriate View to a ViewModel. Here is my current solution: The parent ViewModel needs to create a child ViewModel for each child Model, so it has a factory method added to its constructor which it uses during initialization: public class PersonViewModel : IPersonViewModel { private readonly Func<IAddress, IAddressViewModel> _addressViewModelFactory; private readonly IPerson _person; public PersonViewModel(IPerson person, Func<IAddress, IAddressViewModel> addressViewModelFactory) { _addressViewModelFactory = addressViewModelFactory; _person = person; Addresses = new ObservableCollection<IAddressViewModel>(); } public ObservableCollection<IAddressViewModel> Addresses { get; private set; } public void Initialize() { foreach (IAddress address in _person.Addresses) Addresses.Add(_addressViewModelFactory(address)); } } A factory method that satisfies the Func<IAddress, IAddressViewModel> interface is registered with the main UnityContainer. The factory method uses a child container to register the IAddress dependency that is required by the ViewModel and then resolves the child ViewModel: public class Factory { private readonly IUnityContainer _container; public Factory(IUnityContainer container) { _container = container; } public void RegisterStuff() { _container.RegisterInstance<Func<IAddress, IAddressViewModel>>(CreateAddressViewModel); } private IAddressViewModel CreateAddressViewModel(IAddress model) { IUnityContainer childContainer = _container.CreateChildContainer(); childContainer.RegisterInstance(model); return childContainer.Resolve<IAddressViewModel>(); } } Now, when the PersonViewModel is initialized, it loops through each Address in the Model and calls CreateAddressViewModel() (which was injected via the Func<IAddress, IAddressViewModel> argument). CreateAddressViewModel() creates a temporary child container and registers the IAddress model so that when it resolves the IAddressViewModel from the child container the AddressViewModel gets the correct instance injected via its constructor. This seems to be a good solution to me as the dependencies of the ViewModels are very clear and they are easily testable and unaware of the IoC container. On the other hand, performance is OK but not great as a lot of temporary child containers can be created. Also I end up with a lot of very similar factory methods. Is this the best way to inject the child Models into the child ViewModels with Unity? Is there a better (or faster) way to do it in other IoC containers, e.g. Autofac? How would this problem be tackled with MEF, given that it is not a traditional IoC container but is still used to compose objects?

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• DSP - Filtering in the frequency domain via FFT

  - by Trap

  I've been playing around a little with the Exocortex implementation of the FFT, but I'm having some problems. Whenever I modify the amplitudes of the frequency bins before calling the iFFT the resulting signal contains some clicks and pops, especially when low frequencies are present in the signal (like drums or basses). However, this does not happen if I attenuate all the bins by the same factor. Let me put an example of the output buffer of a 4-sample FFT: // Bin 0 (DC) FFTOut[0] = 0.0000610351563 FFTOut[1] = 0.0 // Bin 1 FFTOut[2] = 0.000331878662 FFTOut[3] = 0.000629425049 // Bin 2 FFTOut[4] = -0.0000381469727 FFTOut[5] = 0.0 // Bin 3, this is the first and only negative frequency bin. FFTOut[6] = 0.000331878662 FFTOut[7] = -0.000629425049 The output is composed of pairs of floats, each representing the real and imaginay parts of a single bin. So, bin 0 (array indexes 0, 1) would represent the real and imaginary parts of the DC frequency. As you can see, bins 1 and 3 both have the same values, (except for the sign of the Im part), so I guess bin 3 is the first negative frequency, and finally indexes (4, 5) would be the last positive frequency bin. Then to attenuate the frequency bin 1 this is what I do: // Attenuate the 'positive' bin FFTOut[2] *= 0.5; FFTOut[3] *= 0.5; // Attenuate its corresponding negative bin. FFTOut[6] *= 0.5; FFTOut[7] *= 0.5; For the actual tests I'm using a 1024-length FFT and I always provide all the samples so no 0-padding is needed. // Attenuate var halfSize = fftWindowLength / 2; float leftFreq = 0f; float rightFreq = 22050f; for( var c = 1; c < halfSize; c++ ) { var freq = c * (44100d / halfSize); // Calc. positive and negative frequency indexes. var k = c * 2; var nk = (fftWindowLength - c) * 2; // This kind of attenuation corresponds to a high-pass filter. // The attenuation at the transition band is linearly applied, could // this be the cause of the distortion of low frequencies? var attn = (freq < leftFreq) ? 0 : (freq < rightFreq) ? ((freq - leftFreq) / (rightFreq - leftFreq)) : 1; // Attenuate positive and negative bins. mFFTOut[ k ] *= (float)attn; mFFTOut[ k + 1 ] *= (float)attn; mFFTOut[ nk ] *= (float)attn; mFFTOut[ nk + 1 ] *= (float)attn; } Obviously I'm doing something wrong but can't figure out what. I don't want to use the FFT output as a means to generate a set of FIR coefficients since I'm trying to implement a very basic dynamic equalizer. What's the correct way to filter in the frequency domain? what I'm missing? Thanks in advance.

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• What does the `forall` keyword in Haskell/GHC do?

  - by JUST MY correct OPINION

  I've been banging my head on this one for (quite literally) years now. I'm beginning to kinda/sorta understand how the foreach keyword is used in so-called "existential types" like this: data ShowBox = forall s. Show s => SB s (This despite the confusingly-worded explanations of it in the fragments found all around the web.) This is only a subset, however, of how foreach is used and I simply cannot wrap my mind around its use in things like this: runST :: forall a. (forall s. ST s a) -> a Or explaining why these are different: foo :: (forall a. a -> a) -> (Char,Bool) bar :: forall a. ((a -> a) -> (Char, Bool)) Or the whole RankNTypes stuff that breaks my brain when "explained" in a way that makes me want to do that Samuel L. Jackson thing from Pulp Fiction. (Don't follow that link if you're easily offended by strong language.) The problem, really, is that I'm a dullard. I can't fathom the chicken scratchings (some call them "formulae") of the elite mathematicians that created this language seeing as my university years are over two decades behind me and I never actually had to put what I learnt into use in practice. I also tend to prefer clear, jargon-free English rather than the kinds of language which are normal in academic environments. Most of the explanations I attempt to read on this (the ones I can find through search engines) have these problems: They're incomplete. They explain one part of the use of this keyword (like "existential types") which makes me feel happy until I read code that uses it in a completely different way (like runST, foo and bar above). They're densely packed with assumptions that I've read the latest in whatever branch of discrete math, category theory or abstract algebra is popular this week. (If I never read the words "consult the paper whatever for details of implementation" again, it will be too soon.) They're written in ways that frequently turn even simple concepts into tortuously twisted and fractured grammar and semantics. (I suspect that the last two items are the biggest problem. I wouldn't know, though, since I'm too much a dullard to comprehend them.) It's been asked why Haskell never really caught on in industry. I suspect, in my own humble, unintelligent way, that my experience in figuring out one stupid little keyword -- a keyword that is increasingly ubiquitous in the libraries being written these days -- are also part of the answer to that question. It's hard for a language to catch on when even its individual keywords cause years-long quests to comprehend. Years-long quests which end in failure. So... On to the actual question. Can anybody completely explain the foreach keyword in clear, plain English (or, if it exists somewhere, point to such a clear explanation which I've missed) that doesn't assume I'm a mathematician steeped in the jargon?

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• Break a class in twain, or impose an interface for restricted access?

  - by bedwyr

  What's the best way of partitioning a class when its functionality needs to be externally accessed in different ways by different classes? Hopefully the following example will make the question clear :) I have a Java class which accesses a single location in a directory allowing external classes to perform read/write operations to it. Read operations return usage stats on the directory (e.g. available disk space, number of writes, etc.); write operations, obviously, allow external classes to write data to the disk. These methods always work on the same location, and receive their configuration (e.g. which directory to use, min disk space, etc.) from an external source (passed to the constructor). This class looks something like this: public class DiskHandler { public DiskHandler(String dir, int minSpace) { ... } public void writeToDisk(String contents, String filename) { int space = getAvailableSpace(); ... } public void getAvailableSpace() { ... } } There's quite a bit more going on, but this will do to suffice. This class needs to be accessed differently by two external classes. One class needs access to the read operations; the other needs access to both read and write operations. public class DiskWriter { DiskHandler diskHandler; public DiskWriter() { diskHandler = new DiskHandler(...); } public void doSomething() { diskHandler.writeToDisk(...); } } public class DiskReader { DiskHandler diskHandler; public DiskReader() { diskHandler = new DiskHandler(...); } public void doSomething() { int space = diskHandler.getAvailableSpace(...); } } At this point, both classes share the same class, but the class which should only read has access to the write methods. Solution 1 I could break this class into two. One class would handle read operations, and the other would handle writes: // NEW "UTILITY" CLASSES public class WriterUtil { private ReaderUtil diskReader; public WriterUtil(String dir, int minSpace) { ... diskReader = new ReaderUtil(dir, minSpace); } public void writeToDisk(String contents, String filename) { int = diskReader.getAvailableSpace(); ... } } public class ReaderUtil { public ReaderUtil(String dir, int minSpace) { ... } public void getAvailableSpace() { ... } } // MODIFIED EXTERNALLY-ACCESSING CLASSES public class DiskWriter { WriterUtil diskWriter; public DiskWriter() { diskWriter = new WriterUtil(...); } public void doSomething() { diskWriter.writeToDisk(...); } } public class DiskReader { ReaderUtil diskReader; public DiskReader() { diskReader = new ReaderUtil(...); } public void doSomething() { int space = diskReader.getAvailableSpace(...); } } This solution prevents classes from having access to methods they should not, but it also breaks encapsulation. The original DiskHandler class was completely self-contained and only needed config parameters via a single constructor. By breaking apart the functionality into read/write classes, they both are concerned with the directory and both need to be instantiated with their respective values. In essence, I don't really care to duplicate the concerns. Solution 2 I could implement an interface which only provisions read operations, and use this when a class only needs access to those methods. The interface might look something like this: public interface Readable { int getAvailableSpace(); } The Reader class would instantiate the object like this: Readable diskReader; public DiskReader() { diskReader = new DiskHandler(...); } This solution seems brittle, and prone to confusion in the future. It doesn't guarantee developers will use the correct interface in the future. Any changes to the implementation of the DiskHandler could also need to update the interface as well as the accessing classes. I like it better than the previous solution, but not by much. Frankly, neither of these solutions seems perfect, but I'm not sure if one should be preferred over the other. I really don't want to break the original class up, but I also don't know if the interface buys me much in the long run. Are there other solutions I'm missing?

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• Symfony2: validate an object that is not an entity

  - by Marronsuisse

  I am using CraueFormFlowBundle to have a multiple page form, and am trying to do some validation on some of the fields but can't figure out how to do this. The object that needs to be validated isn't an Entity, which is causing me trouble. I tried adding a collectionConstraint in the getDefaultOption function of my form type class, but this doesn't work as I get the "Expected argument of type array or Traversable and ArrayAccess" error. I tried with annotations in my object class, but they don't seem to be taken into account. Are annotations taken into account if the class isn't an entity? (i set enable_annotations to true) Anyway, what is the proper way to do this? Basically, I just want to validate that "age" is an integer... class PoemDataCollectorFormType extends AbstractType { public function buildForm(FormBuilder $builder, array $options) { switch ($options['flowStep']) { case 6: $builder->add('msgCategory', 'hidden', array( )); $builder->add('msgFIB','text', array( 'required' => false, )); $builder->add('age', 'integer', array( 'required' => false, )); break; } } public function getDefaultOptions(array $options) { $options = parent::getDefaultOptions($options); $options['flowStep'] = 1; $options['data_class'] = 'YOP\YourOwnPoetBundle\PoemBuilder\PoemDataCollector'; $options['intention'] = 'my_secret_key'; return $options; } } EDIT: add code, handle validation with annotations As Cyprian, I was pretty sure that using annotations should work, however it doesn't... Here is how I try: In my Controller: public function collectPoemDataAction() { $collector = $this->get('yop.poem.datacollector'); $flow = $this->get('yop.form.flow.poemDataCollector'); $flow->bind($collector); $form = $flow->createForm($collector); if ($flow->isValid($form)) { .... } } In my PoemDataCollector class, which is my data class (service yop.poem.datacollector): class PoemDataCollector { /** * @Assert\Type(type="integer", message="Age should be a number") */ private $age; } EDIT2: Here is the services implementation: The data class (PoemDataCollector) seems to be linked to the flow class and not to the form.. Is that why there is no validation? <service id="yop.poem.datacollector" class="YOP\YourOwnPoetBundle\PoemBuilder\PoemDataCollector"> </service> <service id="yop.form.poemDataCollector" class="YOP\YourOwnPoetBundle\Form\Type\PoemDataCollectorFormType"> <tag name="form.type" alias="poemDataCollector" /> </service> <service id="yop.form.flow.poemDataCollector" class="YOP\YourOwnPoetBundle\Form\PoemDataCollectorFlow" parent="craue.form.flow" scope="request"> <call method="setFormType"> <argument type="service" id="yop.form.poemDataCollector" /> </call> </service> How can I do the validation while respecting the craueFormFlowBundle guidelines? The guidelines state: Validation groups To validate the form data class a step-based validation group is passed to the form type. By default, if getName() of the form type returns registerUser, such a group is named flow_registerUser_step1 for the first step. Where should I state my constraint to use those validation groups..? I tried: YOP\YourOwnPoetBundle\PoemBuilder\Form\Type\PoemDataCollectorFormType: properties: name: - MinLength: { limit: 5, message: "Your name must have at least {{ limit }} characters.", groups: [flow_poemDataCollector_step1] } sex: - Type: type: integer message: Please input a number groups: [flow_poemDataCollector_step6] But it is not taken into acount.

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• Picking good first estimates for Goldschmidt division

  - by Mads Elvheim

  I'm calculating fixedpoint reciprocals in Q22.10 with Goldschmidt division for use in my software rasterizer on ARM. This is done by just setting the nominator to 1, i.e the nominator becomes the scalar on the first iteration. To be honest, I'm kind of following the wikipedia algorithm blindly here. The article says that if the denominator is scaled in the half-open range (0.5, 1.0], a good first estimate can be based on the denominator alone: Let F be the estimated scalar and D be the denominator, then F = 2 - D. But when doing this, I lose a lot of precision. Say if I want to find the reciprocal of 512.00002f. In order to scale the number down, I lose 10 bits of precision in the fraction part, which is shifted out. So, my questions are: Is there a way to pick a better estimate which does not require normalization? Also, is it possible to pre-calculate the first estimates so the series converges faster? Right now, it converges after the 4th iteration on average. On ARM this is about ~50 cycles worst case, and that's not taking emulation of clz/bsr into account, nor memory lookups. Here is my testcase. Note: The software implementation of clz on line 13 is from my post here. You can replace it with an intrinsic if you want. #include <stdio.h> #include <stdint.h> const unsigned int BASE = 22ULL; static unsigned int divfp(unsigned int val, int* iter) { /* Nominator, denominator, estimate scalar and previous denominator */ unsigned long long N,D,F, DPREV; int bitpos; *iter = 1; D = val; /* Get the shift amount + is right-shift, - is left-shift. */ bitpos = 31 - clz(val) - BASE; /* Normalize into the half-range (0.5, 1.0] */ if(0 < bitpos) D >>= bitpos; else D <<= (-bitpos); /* (FNi / FDi) == (FN(i+1) / FD(i+1)) */ /* F = 2 - D */ F = (2ULL<<BASE) - D; /* N = F for the first iteration, because the nominator is simply 1. So don't waste a 64-bit UMULL on a multiply with 1 */ N = F; D = ((unsigned long long)D*F)>>BASE; while(1){ DPREV = D; F = (2<<(BASE)) - D; D = ((unsigned long long)D*F)>>BASE; /* Bail when we get the same value for two denominators in a row. This means that the error is too small to make any further progress. */ if(D == DPREV) break; N = ((unsigned long long)N*F)>>BASE; *iter = *iter + 1; } if(0 < bitpos) N >>= bitpos; else N <<= (-bitpos); return N; } int main(int argc, char* argv[]) { double fv, fa; int iter; unsigned int D, result; sscanf(argv[1], "%lf", &fv); D = fv*(double)(1<<BASE); result = divfp(D, &iter); fa = (double)result / (double)(1UL << BASE); printf("Value: %8.8lf 1/value: %8.8lf FP value: 0x%.8X\n", fv, fa, result); printf("iteration: %d\n",iter); return 0; }

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• QGraphicsView and custom Cursors

  - by Etienne de Martel

  I am trying to make use of a mix of custom cursors and preset cursors for my QGraphicsView. In my implementation we have created a notion of "modes" for the view. Meaning that depending on what "mode" the user is in, different things will happen on the left-click, or left-click drag. Anyway, none of that is the problem, just the context. The problem arises when I try to change the cursor for each mode. For instance, for mode 1 we want to show the regular Arrow cursor, but for mode 2, we want to use a custom pixmap. Seemingly simple we call graphicsview->viewport()->setCursor(Qt::QArrowCursor)  when we are switching to mode 1, and graphicsview->viewport()->setCursor(our custom cursor) for mode 2. Except it doesn't work at all. Firstly, the cursor does not change to the custom cursor. That is the first problem. However, if through another operation the drag mode of the graphics view gets set to ScrollHandDrag, the cursor will switch to the custom cursor once the drag operation is complete. Weird. But the plot thickens... Once we switch to the custom cursor, it can never be changed back to the ArrorCursor no matter how many times we call setCursor(Qt::QArrowCursor). it also doesn't seem to matter whether I call setCursor on the viewport or the graphics view itself. So, just for fun, I added a call to graphicsview->unsetCursor() just before we want to change the cursor, and that at least rectifies the second problem. The cursor changes just fine so long as we do a little HandDragging in between. Better, but certainly not optimal. However it should be noted, that doing the unsetCursor on the viewport doesn't work. it must absolutely be done on the graphicsview - regardless of the fact that we are setting the cursor on the viewport. To completely patch over the problem I have added these two lines after I set the cursor: graphicsview->setDragMode(QGraphicsView::ScrollHandDrag); graphicsview->setDragMode(QGraphicsView::NoDrag); Which works, but ye gads!! So something magical is happening inside these two methods that fixes the problem, but glancing at the code I don't see what. Something to do with the fact that the drag mode is changing the cursor I imagine. Just for completeness, I should also mention that the thing that triggers the mode change, is a QPushButton that has been added to the scene using QGraphicsScene->addWidget(). I don't know if that has anything to do with it, but you never know. I am hoping that either someone could clarify why I need to make these seemingly random calls. I don't think I am doing anything wrong anywhere. Thanks in advance for any help. EDIT: Here is an actual code example with the cursor patches as described above. You can look at and/or download them from the link below. It was a little long to paste here. I included the framework around which the cursors are changed, because I have a funny feeling that that is important somehow. https://gist.github.com/712654 The code where the problem lies is in MyGraphicsView.cpp starting at line 104. This is where the cursor is set in the graphics view. It is exactly as described above. Keep in mind, with the very ugly patches in place the cursors do work - more or less. Without those lines you will see very clearly the problems listed in the post above. Also included in the link, is all the code for a mainWindow that uses the view, etc... the only thing missing are the images I am using. But the images themselves don't matter, any 16x16 pngs will do.

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• Why does this Quicksort work?

  - by IVlad

  I find this Quicksort partitioning approach confusing and wrong, yet it seems to work. I am referring to this pseudocode. Note: they also have a C implementation at the end of the article, but it's very different from their pseudocode, so I don't care about that. I have also written it in C like this, trying to stay true to the pseudocode as much as possible, even if that means doing some weird C stuff: #include <stdio.h> int partition(int a[], int p, int r) { int x = a[p]; int i = p - 1; int j = r + 1; while (1) { do j = j - 1; while (!(a[j] <= x)); do i = i + 1; while (!(a[i] >= x)); if (i < j) { int t = a[i]; a[i] = a[j]; a[j] = t; } else { for (i = 1; i <= a[0]; ++i) printf("%d ", a[i]); printf("- %d\n", j); return j; } } } int main() { int a[100] = //{8, 6,10,13,15,8,3,2,12}; {7, 7, 6, 2, 3, 8, 4, 1}; partition(a, 1, a[0]); return 0; } If you run this, you'll get the following output: 1 6 2 3 4 8 7 - 5 However, this is wrong, isn't it? Clearly a[5] does not have all the values before it lower than it, since a[2] = 6 > a[5] = 4. Not to mention that 7 is supposed to be the pivot (the initial a[p]) and yet its position is both incorrect and lost. The following partition algorithm is taken from wikipedia: int partition2(int a[], int p, int r) { int x = a[r]; int store = p; for (int i = p; i < r; ++i) { if (a[i] <= x) { int t = a[i]; a[i] = a[store]; a[store] = t; ++store; } } int t = a[r]; a[r] = a[store]; a[store] = t; for (int i = 1; i <= a[0]; ++i) printf("%d ", a[i]); printf("- %d\n", store); return store; } And produces this output: 1 6 2 3 8 4 7 - 1 Which is a correct result in my opinion: the pivot (a[r] = a[7]) has reached its final position. However, if I use the initial partitioning function in the following algorithm: void Quicksort(int a[], int p, int r) { if (p < r) { int q = partition(a, p, r); // initial partitioning function Quicksort(a, p, q); Quicksort(a, q + 1, r); // I'm pretty sure q + r was a typo, it doesn't work with q + r. } } ... it seems to be a correct sorting algorithm. I tested it out on a lot of random inputs, including all 0-1 arrays of length 20. I have also tried using this partition function for a selection algorithm, in which it failed to produce correct results. It seems to work and it's even very fast as part of the quicksort algorithm however. So my questions are: Can anyone post an example on which the algorithm DOESN'T work? If not, why does it work, since the partitioning part seems to be wrong? Is this another partitioning approach that I don't know about?

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• When my UIViewController accesses an NSArray in my AppDelegate from an IBAction it crashes the progr

  - by JasonClark

  I have a couple UIViewControllers that I am trying to access an array inside my AppDelegate. When I use an IBAction UIButton and in that method I access my AppDelegate my program dies silently. Nothing in output or the debugger, it just stops. If I run it several times I can see that it is failing to access the array properly. To investigate this problem I created a very basic app. In my AppDelegate.h I declared and set properties for the array #import <UIKit/UIKit.h> @class MyViewController; @interface MyAppDelegate : NSObject <UIApplicationDelegate> { UIWindow *window; MyViewController *viewController; NSArray *images; } @property (nonatomic, retain) NSArray *images; @property (nonatomic, retain) IBOutlet UIWindow *window; @property (nonatomic, retain) IBOutlet MyViewController *viewController;` In the AppDelegate.m I synthesised and initialized the NSArray (Also made sure the images were added to the Resources folder). @synthesize images; - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { images = [NSArray arrayWithObjects: [[NSBundle mainBundle] pathForResource:@"bamboo_nw" ofType:@"jpg"], ..... nil]; NSLog(@"init images size:%i",[images count]); [window addSubview:viewController.view]; [window makeKeyAndVisible]; return YES; } In my UIViewController.h I added class, imported header file, declared, and set properties for my AppDelegate pointer. #import <UIKit/UIKit.h> #import "MyAppDelegate.h" @class MyAppDelegate; @interface MyViewController : UIViewController { MyAppDelegate *mainDelegate; IBOutlet UIButton mybutton; } @property (nonatomic, retain) MyAppDelegate mainDelegate; @property (nonatomic, retain) UIButton *mybutton; -(IBAction) doSomething;` In my UIViewController.m I synthesize and assign my AppDelegate. I set up an IBAction that will log the same count of the NSArray from the AppDelegate. #import "MyViewController.h" #import "MyAppDelegate.h" @implementation MyViewController @synthesize mybutton; - (void)viewDidLoad { mainDelegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate]; NSLog(@"vdl images size:%i",[mainDelegate.images count]); [super viewDidLoad]; } -(IBAction) doSomething { NSLog(@"ds images size:%i",[mainDelegate.images count]); } I print the size of the NSArray in the AppDelegate when I create it, in the ViewController when I first assign my AppDelegate pointer, and then as a result of my IBAction. I find that everytime I hit the button the program dies. On the third time I hit the button, I saw that it ran my IBAction but printed my array size as 1 instead of 8. Am I missing something? Also, why don't I get stack traces or anything, the debugger just dies silently? Thanks in advance for any help! Debugger Console output for 3 runs: [Session started at 2010-05-10 06:21:32 -0700.] 2010-05-10 06:21:44.865 My[59695:207] init images size:8 2010-05-10 06:21:47.246 My[59695:207] vdl images size:8 [Session started at 2010-05-10 06:22:15 -0700.] 2010-05-10 06:22:18.920 My[59704:207] init images size:8 2010-05-10 06:22:19.043 My[59704:207] vdl images size:8 [Session started at 2010-05-10 06:22:23 -0700.] 2010-05-10 06:22:25.966 My[59707:207] init images size:8 2010-05-10 06:22:26.017 My[59707:207] vdl images size:8 2010-05-10 06:22:27.814 My[59707:207] ds images size:1

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• Cannot decode complete cipher list in .NET SslStream handshake.

  - by karmasponge

  While attempting to move from a 'C' based SSL implementation to C# using the .NET SslStream and we have run into what look like cipher compatibility issues with the .NET SslStream and a AS400 machine we are trying to connect to (which worked previously). When we call SslStream.AuthenticateAsClient it is sending the following: 16 03 00 00 37 01 00 00 33 03 00 4d 2c 00 ee 99 4e 0c 5d 83 14 77 78 5c 0f d3 8f 8b d5 e6 b8 cd 61 0f 29 08 ab 75 03 f7 fa 7d 70 00 00 0c 00 05 00 0a 00 13 00 04 00 02 00 ff 01 00 Which decodes as (based on http://www.mozilla.org/projects/security/pki/nss/ssl/draft302.txt) [16] Record Type [03 00] SSL Version [00 37] Body length [01] SSL3_MT_CLIENT_HELLO [00 00 33] Length (51 bytes) [03 00] Version number = 768 [4d 2c 00 ee] 4 Bytes unix time [… ] 28 Bytes random number [00] Session number [00 0c] 12 bytes (2 * 6 Cyphers)? [00 05, 00 0a, 00 13, 00 04, 00 02, 00 ff] - [RC4, PBE-MD5-DES, RSA, MD5, PKCS, ???] [01 00] Null compression method The as400 server responds back with: 15 03 00 00 02 02 28 [15] SSL3_RT_ALERT [03 00] SSL Version [00 02] Body Length (2 Bytes) [02 28] 2 = SSL3_RT_FATAL, 40 = SSL3_AD_HANDSHAKE_FAILURE I'm specifically looking to decode the '00 FF' at the end of the cyphers. Have I decoded it correctly? What does, if anything, '00 FF' decode too? I am using the following code to test/reproduce: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Net.Sockets; using System.Net.Security; using System.Security.Authentication; using System.IO; using System.Diagnostics; using System.Security.Cryptography.X509Certificates; namespace TestSslStreamApp { class DebugStream : Stream { private Stream AggregatedStream { get; set; } public DebugStream(Stream stream) { AggregatedStream = stream; } public override bool CanRead { get { return AggregatedStream.CanRead; } } public override bool CanSeek { get { return AggregatedStream.CanSeek; } } public override bool CanWrite { get { return AggregatedStream.CanWrite; } } public override void Flush() { AggregatedStream.Flush(); } public override long Length { get { return AggregatedStream.Length; } } public override long Position { get { return AggregatedStream.Position; } set { AggregatedStream.Position = value; } } public override int Read(byte[] buffer, int offset, int count) { int bytesRead = AggregatedStream.Read(buffer, offset, count); return bytesRead; } public override long Seek(long offset, SeekOrigin origin) { return AggregatedStream.Seek(offset, origin); } public override void SetLength(long value) { AggregatedStream.SetLength(value); } public override void Write(byte[] buffer, int offset, int count) { AggregatedStream.Write(buffer, offset, count); } } class Program { static void Main(string[] args) { const string HostName = "as400"; TcpClient tcpClient = new TcpClient(HostName, 992); SslStream sslStream = new SslStream(new DebugStream(tcpClient.GetStream()), false, null, null, EncryptionPolicy.AllowNoEncryption); sslStream.AuthenticateAsClient(HostName, null, SslProtocols.Ssl3, false); } } }

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• Regarding Sqlite Datbase connectivity in iphone

  - by Prash.......

  hi.. I am developing an application in iphone in which i have to do the database connectivity using sqlite. I have made a "clsDBManage" class which contains 4 functions open_database, close_database, is_database_open, getdatabase_connection, which are globally defined ,i have a screen called "user details" in which i am filling the user details such as name , mobileno , email-id , password, i want that when user feeds the info it should get connected with database and store the details entered and should authenticate the user the next time he logs in. (Just as we have yahoo login,gmail login screen) clsDBManage.h +(int) openDBConnection; +(int) closeDBConnection; +(BOOL) IsDatabaseOpen; +(sqlite3 *)getDBConnection; clsDBManage.m import "clsDBManage.h" import "Types.h" sqlite3 *DBConnection=nil; @implementation clsDBManage +(int) openDBConnection { NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; NSString *path = [documentsDirectory stringByAppendingPathComponent:@"iphone.sqlite"]; //Before if ([self IsDatabaseOpen] == YES) [self closeDBConnection]; // Open the database. The database was prepared outside the application. if (sqlite3_open([path UTF8String], &DBConnection ) == SQLITE_OK) { ifdef _DEBUG NSLog(@"Database Successfully Opened :)"); endif return CON_RET_SUCCESSFUL; } else { ifdef _DEBUG NSLog(@"Error in opening database :("); endif return CON_RET_ERROR; } } +(BOOL) IsDatabaseOpen { if(DBConnection != nil) { //add if condition to check database is in open state or close state return YES; } else { return NO; } } +(int) closeDBConnection { @try { if(DBConnection != nil) { sqlite3_close(DBConnection); DBConnection = nil; return CON_RET_SUCCESSFUL; } else { return CON_RET_ERROR; } } @catch (NSException * e) { NSLog([e reason]); } } +(sqlite3 *)getDBConnection { if ([self openDBConnection] == 1) return DBConnection; else return nil; } @end //classDBManage file is my handler class where i have written code to open database //my addprofile functions -(NSInteger)addProfile:(NSString *)mobileno:(NSString *)country:(NSString *)username:(NSString *)screenname:(NSString *)emailid:(NSString *)password:(NSString *)retypepassword { @try { sqlite3 *db =[clsDBManage getDBConnection]; if (db != nil) { sqlite3_stmt *statement =nil; const char *sql = "insert into SPCaccountdetails(MobileNo , Country , UserName , ScreenName, EmailId, Password, RetypePawssword) Values(?,?,?,?,?,?,?)"; if(sqlite3_prepare_v2(db, sql, -1, &statement, NULL) != SQLITE_OK) { //NSAssert1(0, @"Error while creating add statement. '%s'", sqlite3_errmsg(db)); } sqlite3_bind_text(statement, 1, [mobileno UTF8String], -1, SQLITE_TRANSIENT); sqlite3_bind_text(statement, 2, [country UTF8String], -1, SQLITE_TRANSIENT); sqlite3_bind_text(statement, 3, [username UTF8String], -1, SQLITE_TRANSIENT); sqlite3_bind_text(statement, 4, [screenname UTF8String], -1, SQLITE_TRANSIENT); sqlite3_bind_text(statement, 5, [emailid UTF8String], -1, SQLITE_TRANSIENT); sqlite3_bind_text(statement, 6, [password UTF8String], -1, SQLITE_TRANSIENT); sqlite3_bind_text(statement, 7, [retypepassword UTF8String], -1, SQLITE_TRANSIENT); if(SQLITE_DONE != sqlite3_step(statement)) { NSAssert1(0, @"Error while inserting data. '%s'", sqlite3_errmsg(db)); } sqlite3_finalize(statement); } } @catch(NSException *e) { //[clsMessageBox ShowMessageOK:@CON_MESSAGE_TITLE_MESSAGE_USER_PROFILE :[e reason]]; } return CON_RET_SUCCESSFUL; } //button click event where i am calling addprofile function;_ [self addProfile:txtMobile :txtCountry :txtName :txtScreenname :txtemailid :txtpassword :txtretypepassword];

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