carriage return - Page 408

How do I prevent form from redirecting after submission?

- by Noor

I have searched the site and I've found various solutions, most of them suggesting using return false; Problem is that I'm using this piece of code to submit the form: $(function() { $("#snd").click(function() { var dendar = "http://" + $("#inpt").val() + ":" + $("#pwd").val() + "secretsite.lol/something.xml"; $("#formen").attr("action", dendar); $("#formen").submit(); alert(dendar); return false; }); }); The alert is just there to let me know that the form has been submitted.. Thanks guys!

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Extension method question. Why do I need to use someObj = someObj.somemethod();

- by Kettenbach

Hi All, I have a simple extension method that I would like to use to add an item to an array of items. public static T[] addElement<T>(this T[] array, T elementToAdd) { var list = new List<T>(array) {elementToAdd}; return list.ToArray(); } this works ok, but when I use it, I am having to set the array equal to the return value. I see that I am returning an Array. I likely want this method to be void, but I would like the item added. Does anyone have any ideas on what I need to do , to make this work the way I am wanting? Instead of someArray = someArray.addElement(item), I just want to do someArray.addElement(item) and then someArray be ready to go. What am I missing here? Thanks, ~ck in San Diego

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Error:A generic error occurred in GDI+

- by sanfra1983

Hi, I created a web project on the server, and when I upload an image shows me the error Error: A generic error occurred in GDI +. I have read many links on the net that talk about this issue, and although I made the changes, nothing went wrong. I was thinking if the case is not an issue of permissions to folders. In fact I have two folders one inside the other. This is the code to resize the image: public Bitmaps ResizeImage (Stream stream, int? width, int? height) ( System.Drawing.Bitmap bmpOut = null; const int defaultWidth = 800; const int defaultHeight = 600; int width = lnWidth == null? defaultWidth: (int) width; int height = lnHeight == null? defaultHeight: (int) height; try ( LoBMP bitmap = new Bitmap (stream); ImageFormat loFormat = loBMP.RawFormat; decimal lnRatio; lnNewWidth int = 0; lnNewHeight int = 0; if (loBMP.Width <& & lnWidth loBMP.Height <lnHeight) ( loBMP return; ) if (loBMP.Width> loBMP.Height) ( lnRatio = (decimal) lnWidth / loBMP.Width; lnNewWidth = lnWidth; decimal = lnTemp loBMP.Height lnRatio *; lnNewHeight = (int) lnTemp; ) else ( lnRatio = (decimal) lnHeight / loBMP.Height; lnNewHeight = lnHeight; decimal = lnTemp loBMP.Width lnRatio *; lnNewWidth = (int) lnTemp; ) bmpOut = new Bitmap (lnNewWidth, lnNewHeight); Graphics g = Graphics.FromImage (bmpOut); g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; g.FillRectangle (Brushes.White, 0, 0, lnNewWidth, lnNewHeight); g.DrawImage (loBMP, 0, 0, lnNewWidth, lnNewHeight); loBMP.Dispose (); ) catch ( return null; ) bmpOut return; ) and this is the code that I insert in the codebehind: string filepath = AppDomain.CurrentDomain.BaseDirectory + img_veterinario / "; string = filepathM AppDomain.CurrentDomain.BaseDirectory + img_veterinario / img_veterinarioM; Reseize Reseize R = new (); Bitmap = photosFileOriginal r.ResizeImage (fucasiclinici.PostedFile.InputStream, 400, 400); Bitmap = photosFileMiniatura r.ResizeImage (fucasiclinici.PostedFile.InputStream, 72, 72); String filename = Path.GetFileName (fucasiclinici.PostedFile.FileName); photosFileOriginal.Save (Path.Combine (filepath, filename)); photosFileMiniatura.Save (Path.Combine (filepathM, filename)); Can you help me? Thanks

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Lambda expressions and nullable types

- by Mathew

I have two samples of code. One works and returns the correct result, one throws a null reference exception. What's the difference? I know there's some magic happening with capturing variables for the lambda expression but I don't understand what's going on behind the scenes here. int? x = null; bool isXNull = !x.HasValue; // this works var result = from p in data.Program where (isXNull) select p; return result.Tolist(); // this doesn't var result2 = from p in data.Program where (!x.HasValue) select p; return result2.ToList();

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Getting huge lags when downloading files via Service

- by Copa

I have a Service which receives URLs to download. The Service than downloads these URLs and save them to a file on the SD Card. When I put more than 2 items in the download queue my device is unusable. It nearly freezes. Huge lags and so on. Any idea? Sourcecode: private static boolean downloading = false; private static ArrayList<DownloadItem> downloads = new ArrayList<DownloadItem>(); /** * called once when the service started */ public static void start() { Thread thread = new Thread(new Runnable() { @Override public void run() { while (true) { if (downloads.size() > 0 && !downloading) { downloading = true; DownloadItem item = downloads.get(0); downloadSingleFile(item.getUrl(), item.getFile()); } } } }); thread.start(); } public static void addDownload(DownloadItem item) { downloads.add(item); } private static void downloadSuccessfullFinished() { if (downloads.size() > 0) downloads.get(0).setDownloaded(true); downloadFinished(); } private static void downloadFinished() { // remove the first entry; it has been downloaded if (downloads.size() > 0) downloads.remove(0); downloading = false; } private static void downloadSingleFile(String url, File output) { final int maxBufferSize = 4096; HttpResponse response = null; try { response = new DefaultHttpClient().execute(new HttpGet(url)); if (response != null && response.getStatusLine().getStatusCode() == 200) { // request is ok InputStream is = response.getEntity().getContent(); BufferedInputStream bis = new BufferedInputStream(is); RandomAccessFile raf = new RandomAccessFile(output, "rw"); ByteArrayBuffer baf = new ByteArrayBuffer(maxBufferSize); long current = 0; long i = 0; // read and write 4096 bytes each time while ((current = bis.read()) != -1) { baf.append((byte) current); if (++i == maxBufferSize) { raf.write(baf.toByteArray()); baf = new ByteArrayBuffer(maxBufferSize); i = 0; } } if (i > 0) // write the last bytes to the file raf.write(baf.toByteArray()); baf.clear(); raf.close(); bis.close(); is.close(); // download finished get start next download downloadSuccessfullFinished(); return; } } catch (Exception e) { // not successfully downloaded downloadFinished(); return; } // not successfully downloaded downloadFinished(); return; }

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Why does this code generate an error? [closed]

- by user559601

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Proper error handling in a custom Zend_Autoloader?

- by Pekka

I'm building a custom autoloader based on Zend Framework's autoloading (related question here). The basic approach, taken from that question, is class My_Autoloader implements Zend_Loader_Autoloader_Interface { public function autoload($class) { // add your logic to find the required classes in here } } and then binding the new autoloader class to a class prefix. Now what I'm unsure about is how to handle errors inside the autoload method (for example, "class file not found") in a proper, ZF compliant way. I'm new to the framework, its conventions and style. Do I quietly return false and let the class creation process crash? Do I output an error or log message somehow (which would be nice to pinpoint the problem) and return false? If so, what is the Zend way of doing that? Do I trigger an error? Do I throw an exception? If so, what kind?

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Pass parameters to a user control - asp.net

- by Cristian Boariu

Hi, I have this user control: <user:RatingStars runat="server" product="<%= getProductId() %>" category="<%= getCategoryId() %>"></user:RatingStars> You see that i fill the product and category by calling two methods: public string getProductId() { return productId.ToString(); } public string getCategoryId() { return categoryId.ToString(); } I do not understand why, in the user control, when i take the data received (product and category) it gives me "<%= getProductId() %" instead of giving the id received from that method... Any help would be kindly appreciated...

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Interface name as a Type

- by user1889148

I am trying to understand interfaces in Java and have this task to do which I am a stack with. It must be something easy, but I don't seem to see the solution. Interface contains a few methods, one of them should return true if all elements of this set are also in the set. I.e. public interface ISet{ //some methods boolean isSubsetOf(ISet x); } Then the class: public class myClass implements ISet{ ArrayList<Integer> mySet; public myClass{ mySet = new ArrayList<Integer>(); } //some methods public boolean isSubsetOf(ISet x){ //method body } } What do I need to write in method body? How do I check that the instance of myClass is a subset of ISet collection? I was trying to cast, but it gives an error: ArrayList<Integer> param = (ArrayList<Integer>)x; return param.containsAll(mySet);

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jpa-Primarykey relationship

- by megala

Hi created student entity in gogole app engine datastore using JPA. Student---Coding @Entity @Table(name="StudentPersonalDetails", schema="PUBLIC") public class StudentPersonalDetails { @Id @Column(name = "STUDENTNO") private Long stuno; @Basic @Column(name = "STUDENTNAME") private String stuname; public void setStuname(String stuname) { this.stuname = stuname; } public String getStuname() { return stuname; } public void setStuno(Longstuno) { this.stuno = stuno; } public Long getStuno() { return stuno; } public StudentPersonalDetails(Long stuno,String stuname) { this.stuno = stuno; this.stuname = stuname; } } I stored Property value as follows Stuno Stuname 1 a 2 b If i stored Again Stuno No 1 stuname z means it wont allow to insert the record But. It Overwrite the value Stuno Stuname 1 z 2 b How to solve this?

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why datetime.now not work when I didn't use tolist?

- by MemoryLeak

When I use datacontext.News .Where(p => p.status == true) .Where(p => p.date <= DateTime.Now) .ToList(); the system will return no results; When I use datacontext.News .Where(p => p.status == true) .ToList() .Where(p => p.date <= DateTime.Now) .ToList(); system will return expected results. Can anyone tell me what's up? Thanks in advance !

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How do I avoid boxing/unboxing when extending System.Object?

- by Robert H.

I'm working on an extension method that's only applicable to reference types. I think, however, it's currently boxing and unboxing the the value. How can I avoid this? namespace System { public static class SystemExtensions { public static TResult GetOrDefaultIfNull<T, TResult>(this T obj, Func<T, TResult> getValue, TResult defaultValue) { if (obj == null) return defaultValue; return getValue(obj); } } } Example usage: public class Foo { public int Bar { get; set; } } In some method: Foo aFooObject = new Foo { Bar = 1 }; Foo nullReference = null; Console.WriteLine(aFooObject.GetOrDefaultIfNull((o) => o.Bar, 0)); // results: 1 Console.WriteLine(nullReference.GetOrDefaultIfNull((o) => o.Bar, 0)); // results: 0

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Lua - initializing

- by Ockonal

Hello, I can't init lua correctly under Arch Linux. Lua - latest version. Here is my code: #include <stdio.h> extern "C" { #include <lua.h> #include <lauxlib.h> #include <lualib.h> } int main() { lua_State *luaVM = luaL_newstate(); if (luaVM == NULL) { printf("Error initializing lua!\n"); return -1; } luaL_openlibs(luaVM); lua_close(luaVM); return 0; } /tmp/cc0iJ6lW.o: In function main': test_lua.cpp:(.text+0xa): undefined reference toluaL_newstate' test_lua.cpp:(.text+0x34): undefined reference to `luaL_openlibs' test_lua.cpp:(.text+0x40): undefined reference to `lua_close' collect2: ld returned 1 exit status What's wrong?

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Is an ArrayList automaticaly declared static in Java, if it is an instance variable?

- by Alex

I'm trying to do something like this: private class aClass { private ArrayList<String> idProd; aClass(ArrayList<String> prd) { this.idProd=new ArrayList<String>(prd); } public ArrayList<String> getIdProd() { return this.idProd; } } So if I have multiple instances of ArrayLIst<String> (st1 ,st2 ,st3) and I want to make new objects of aClass: { aClass obj1,obj2,obj3; obj1=new aClass(st1); obj2=new aClass(st2); obj3=new aClass(st3); } Will all of the aClass objects return st3 if I access the method getIdProd() for each of them(obj1..obj3)? Is an ArrayList as an instance variable automatically declared static?

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Real world examples of Ecmascript functions returning a Reference?

- by Bergi

Read the EcmaScript specification, section 8.7 The Reference Specification Type: The Reference type is used to explain the behaviour of such operators as delete, typeof, and the assignment operators. […] A Reference is a resolved name binding. Function calls are permitted to return references. This possibility is admitted purely for the sake of host objects. No built-in ECMAScript function defined by this specification returns a reference and there is no provision for a user-defined function to return a reference. Those last two sentences impressed me. With this, you could do things like coolHostFn() = value (valid syntax, btw). So my question is: Are there any EcmaScript implementations that define host function objects which result in Reference values?

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Android Camera takePicture function does not call Callback function

- by Tomáš 'Guns Blazing' Frcek

I am working on a custom Camera activity for my application. I was following the instruction from the Android Developers site here: http://developer.android.com/guide/topics/media/camera.html Everything seems to works fine, except the Callback function is not called and the picture is not saved. Here is my code: public class CameraActivity extends Activity { private Camera mCamera; private CameraPreview mPreview; private static final String TAG = "CameraActivity"; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.camera); // Create an instance of Camera mCamera = getCameraInstance(); // Create our Preview view and set it as the content of our activity. mPreview = new CameraPreview(this, mCamera); FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview); preview.addView(mPreview); Button captureButton = (Button) findViewById(R.id.button_capture); captureButton.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { Log.v(TAG, "will now take picture"); mCamera.takePicture(null, null, mPicture); Log.v(TAG, "will now release camera"); mCamera.release(); Log.v(TAG, "will now call finish()"); finish(); } }); } private PictureCallback mPicture = new PictureCallback() { @Override public void onPictureTaken(byte[] data, Camera camera) { Log.v(TAG, "Getting output media file"); File pictureFile = getOutputMediaFile(); if (pictureFile == null) { Log.v(TAG, "Error creating output file"); return; } try { FileOutputStream fos = new FileOutputStream(pictureFile); fos.write(data); fos.close(); } catch (FileNotFoundException e) { Log.v(TAG, e.getMessage()); } catch (IOException e) { Log.v(TAG, e.getMessage()); } } }; private static File getOutputMediaFile() { String state = Environment.getExternalStorageState(); if (!state.equals(Environment.MEDIA_MOUNTED)) { return null; } else { File folder_gui = new File(Environment.getExternalStorageDirectory() + File.separator + "GUI"); if (!folder_gui.exists()) { Log.v(TAG, "Creating folder: " + folder_gui.getAbsolutePath()); folder_gui.mkdirs(); } File outFile = new File(folder_gui, "temp.jpg"); Log.v(TAG, "Returnng file: " + outFile.getAbsolutePath()); return outFile; } } After clicking the Button, I get logs: "will now take picture", "will now release camera" and "will now call finish". The activity finishes succesfully, but the Callback function was not called during the mCamera.takePicture(null, null, mPicture); function (There were no logs from the mPicture callback or getMediaOutputFile functions) and there is no file in the location that was specified. Any ideas? :) Much thanks!

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Serialization of an object and its Contained Objects

- by Amit

There is a main class having 2 subClasses(each represent separate entity) and all classes needs to be serialized.. how should I proceed ? My requirement is when I serelize MainClass, I should get the xml for each sub class and main class as well. Thanks in advance... and if my approach is incorrect... correct that as well.. Ex given below... class MainClass { SubClass1 objSubclass1 = null; SubClass2 objSubclass2 = null; public MainClass() { objSubclass1 = new SubClass1(); objSubclass2 = new SubClass2(); } [XmlElement("SubClass1")] public SubClass1 SubClass1 {get {return objSubclass1;} } [XmlElement("SubClass2")] public SubClass2 SubClass2 {get {return objSubclass2;} } } Class SubClass1 { Some properties here... } Class SubClass2 { Some properties here... }

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Calculating the Angle Between Two vectors Using Dot Product

- by P. Avery

I'm trying to calculate the angle between two vectors so that I can rotate a character in the direction of an object in 3D space. I have two vectors( character & object), loc_look, and modelPos respectively. For simplicity's sake I am only trying to rotate along the up axis...yaw. loc_look = D3DXVECTOR3 (0, 0, 1), modelPos = D3DXVECTOR3 (0, 0, 15); I have written this code which seems to be the correct calculations. My problem arises, seemingly, because the rotation I apply to the character's look vector(loc_look) exceeds the value of the object's position (modelPos). Here is my code: BOOL CEntity::TARGET() { if(graphics.m_model->m_enemy) { D3DXVECTOR3 modelPos = graphics.m_model->position; D3DXVec3Normalize(&modelPos, &modelPos); //D3DXVec3Normalize(&loc_look, &loc_look); float dot = D3DXVec3Dot(&loc_look, &modelPos); float yaw = acos(dot); BOOL neg = (loc_look.x > modelPos.x) ? true : false; switch ( neg ) { case false: Yaw(yaw); return true; case true: Yaw(-yaw); return true; } } else return false; } I rotate the character's orientation matrix with the following code: void CEntity::CalculateOrientationMatrix(D3DXMATRIX *orientationMatrix) { D3DXMatrixRotationAxis(&rotY, &loc_up, loc_yaw); D3DXVec3TransformCoord(&loc_look, &loc_look, &rotY); D3DXVec3TransformCoord(&loc_right, &loc_right, &rotY); D3DXMatrixRotationAxis(&rotX, &loc_right, loc_pitch); D3DXVec3TransformCoord(&loc_look, &loc_look, &rotX); D3DXVec3TransformCoord(&loc_up, &loc_up, &rotX); D3DXMatrixRotationAxis(&rotZ, &loc_look, loc_roll); D3DXVec3TransformCoord(&loc_up, &loc_up, &rotZ); D3DXVec3TransformCoord(&loc_right, &loc_right, &rotZ); *orientationMatrix *= rotX * rotY * rotZ; orientationMatrix->_41 = loc_position.x; orientationMatrix->_42 = loc_position.y; orientationMatrix->_43 = loc_position.z; //D3DXVec3Normalize(&loc_look, &loc_look); SetYawPitchRoll(0,0,0); // Reset Yaw, Pitch, & Roll Amounts } Also to note, the modelPos.x increases by 0.1 each iteration so the character will face the object as it moves along the x-axis... Now, when I run program, in the first iteration everything is fine(I haven't rotated the character yet). On the second iteration, the loc_look.x value is greater than the modelPos.x value(I rotated the character too much using the angle specified with the dot product calculations in the TARGET function). Therefore on the second iteration my code will rotate the character left to adjust for the difference in the vectors' x values... How can I tighten up the measurements so that I do not rotate my character's look vector by too great a value?

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UIVIewController not released when view is dismissed

- by Nelson Ko

I have a main view, mainWindow, which presents a couple of buttons. Both buttons create a new UIViewController (mapViewController), but one will start a game and the other will resume it. Both buttons are linked via StoryBoard to the same View. They are segued to modal views as I'm not using the NavigationController. So in a typical game, if a person starts a game, but then goes back to the main menu, he triggers: [self dismissViewControllerAnimated:YES completion:nil ]; to return to the main menu. I would assume the view controller is released at this point. The user resumes the game with the second button by opening another instance of mapViewController. What is happening, tho, is some touch events will trigger methods on the original instance (and write status updates to them - therefore invisible to the current view). When I put a breakpoint in the mapViewController code, I can see the instance will be one or the other (one of which should be released). I have tried putting a delegate to the mainWindow clearing the view: [self.delegate clearMapView]; where in the mainWindow - (void) clearMapView{ gameWindow = nil; } I have also tried self.view=nil; in the mapViewController. The mapViewController code contains MVC code, where the model is static. I wonder if this may prevent ARC from releasing the view. The model.m contains: static CanShieldModel *sharedInstance; + (CanShieldModel *) sharedModel { @synchronized(self) { if (!sharedInstance) sharedInstance = [[CanShieldModel alloc] init]; return sharedInstance; } return sharedInstance; } Another post which may have a lead, but so far not successful, is UIViewController not being released when popped I have in ViewDidLoad: // checks to see if app goes inactive - saves. [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(resignActive) name:UIApplicationWillResignActiveNotification object:nil]; with the corresponding in ViewDidUnload: [[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationWillResignActiveNotification object:nil]; Does anyone have any suggestions? EDIT: - (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{ NSString *identifier = segue.identifier; if ([identifier isEqualToString: @"Start Game"]){ gameWindow = (ViewController *)[segue destinationViewController]; gameWindow.newgame=-1; gameWindow.delegate = self; } else if ([identifier isEqualToString: @"Resume Game"]){ gameWindow = (ViewController *)[segue destinationViewController]; gameWindow.newgame=0; gameWindow.delegate = self;

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WinMain not called before main (C/C++ Program Entry Point Issue)

- by BT

I was under the impression that this code #include <windows.h> #include <stdio.h> int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow) { printf("WinMain\n"); return 0; } int main() { printf("main\n"); return 0; } would output WinMain, but of course nothing ever works how you expects. Anyways, could somebody please tell me how to get this program to run WinMain first (I do have a reason for using both). I'm running windows 7 with mingw if that helps anything.

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Determining if a coordinate is on a line

- by TGCBraun

I´m coding a little app that allows the user to draw multiple shapes and then remove or resize them. It´s working perfectly on rectangles and ovals, but I´m having issues with lines. Here´s a method that I wrote to find if the clicked spot on the screen is part of a specific line: public boolean containsLocation(int x, int y) { int m = (getY2() - getY()) / (getX2() - getX()); int b = getY() - (m * getX()); if (y == (m * x) + b) { return true; } return false; I´m using the famous y = mx + b formula and replacing y and x to find if the clicked spot is part of the line. The problem is when I click on the screen to remove the line, it only works if I click on the very fist coordinate (x,y) where the line starts. Nothing happens when I click anywhere else along the line. Can anyone shed a light on what I´m doing wrong? Thanks a lot.

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Are Objective-C initializers allowed to share the same name?

- by NattKatt

I'm running into an odd issue in Objective-C when I have two classes using initializers of the same name, but differently-typed arguments. For example, let's say I create classes A and B: A.h: #import <Cocoa/Cocoa.h> @interface A : NSObject { } - (id)initWithNum:(float)theNum; @end A.m: #import "A.h" @implementation A - (id)initWithNum:(float)theNum { self = [super init]; if (self != nil) { NSLog(@"A: %f", theNum); } return self; } @end B.h: #import <Cocoa/Cocoa.h> @interface B : NSObject { } - (id)initWithNum:(int)theNum; @end B.m: #import "B.h" @implementation B - (id)initWithNum:(int)theNum { self = [super init]; if (self != nil) { NSLog(@"B: %d", theNum); } return self; } @end main.m: #import <Foundation/Foundation.h> #import "A.h" #import "B.h" int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; A *a = [[A alloc] initWithNum:20.0f]; B *b = [[B alloc] initWithNum:10]; [a release]; [b release]; [pool drain]; return 0; } When I run this, I get the following output: 2010-04-26 20:44:06.820 FnTest[14617:a0f] A: 20.000000 2010-04-26 20:44:06.823 FnTest[14617:a0f] B: 1 If I reverse the order of the imports so it imports B.h first, I get: 2010-04-26 20:45:03.034 FnTest[14635:a0f] A: 0.000000 2010-04-26 20:45:03.038 FnTest[14635:a0f] B: 10 For some reason, it seems like it's using the data type defined in whichever @interface gets included first for both classes. I did some stepping through the debugger and found that the isa pointer for both a and b objects ends up the same. I also found out that if I no longer make the alloc and init calls inline, both initializations seem to work properly, e.g.: A *a = [A alloc]; [a initWithNum:20.0f]; If I use this convention when I create both a and b, I get the right output and the isa pointers seem to be different for each object. Am I doing something wrong? I would have thought multiple classes could have the same initializer names, but perhaps that is not the case.

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Perfect Forwarding to async lambda

- by Alexander Kondratskiy

I have a function template, where I want to do perfect forwarding into a lambda that I run on another thread. Here is a minimal test case which you can directly compile: #include <thread> #include <future> #include <utility> #include <iostream> #include <vector> /** * Function template that does perfect forwarding to a lambda inside an * async call (or at least tries to). I want both instantiations of the * function to work (one for lvalue references T&, and rvalue reference T&&). * However, I cannot get the code to compile when calling it with an lvalue. * See main() below. */ template <typename T> std::string accessValueAsync(T&& obj) { std::future<std::string> fut = std::async(std::launch::async, [](T&& vec) mutable { return vec[0]; }, std::forward<T>(obj)); return fut.get(); } int main(int argc, char const *argv[]) { std::vector<std::string> lvalue{"Testing"}; // calling with what I assume is an lvalue reference does NOT compile std::cout << accessValueAsync(lvalue) << std::endl; // calling with rvalue reference compiles std::cout << accessValueAsync(std::move(lvalue)) << std::endl; // I want both to compile. return 0; } For the non-compiling case, here is the last line of the error message which is intelligible: main.cpp|13 col 29| note: no known conversion for argument 1 from ‘std::vector<std::basic_string<char> >’ to ‘std::vector<std::basic_string<char> >&’ I have a feeling it may have something to do with how T&& is deduced, but I can't pinpoint the exact point of failure and fix it. Any suggestions? Thank you! EDIT: I am using gcc 4.7.0 just in case this could be a compiler issue (probably not)

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Python - what's your conventions to declare your attributes in a class ?

- by SeyZ

Hello, In Python, I can declare attributes all over the class. For example : class Foo: def __init__(self): self.a = 0 def foo(self): self.b = 0 It's difficult to retrieve all attributes in my class when I have a big class with a lot of attributes. Is it better to have the following code (a) or the next following code (b) : a) Here, it's difficult to locate all attributes : class Foo: def __init__(self): foo_1() foo_2() def foo_1(self): self.a = 0 self.b = 0 def foo_2(self): self.c = 0 b) Here, it's easy to locate all attributes but is it beautiful ? class Foo: def __init__(self): (self.a, self.b) = foo_1() self.c = foo_2() def foo_1(self): a = 0 b = 0 return (a, b) def foo_2(self): c = 0 return c In a nutshell, what is your conventions to declare your attributes in a class ?

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Avoiding explicit recursion in Haskell

- by Travis Brown

The following simple function applies a given monadic function iteratively until it hits a Nothing, at which point it returns the last non-Nothing value. It does what I need, and I understand how it works. lastJustM :: (Monad m) => (a -> m (Maybe a)) -> a -> m a lastJustM g x = g x >>= maybe (return x) (lastJustM g) As part of my self-education in Haskell I'm trying to avoid explicit recursion (or at least understand how to) whenever I can. It seems like there should be a simple non-explicitly recursive solution in this case, but I'm having trouble figuring it out. I don't want something like a monadic version of takeWhile, since it could be expensive to collect all the pre-Nothing values, and I don't care about them anyway. I checked Hoogle for the signature and nothing shows up. The m (Maybe a) bit makes me think a monad transformer might be useful here, but I don't really have the intuitions I'd need to come up with the details (yet). It's probably either embarrassingly easy to do this or embarrassingly easy to see why it can't or shouldn't be done, but this wouldn't be the first time I've used self-embarrassment as a pedagogical strategy. Background: Here's a simplified working example for context: suppose we're interested in random walks in the unit square, but we only care about points of exit. We have the following step function: randomStep :: (Floating a, Ord a, Random a) => a -> (a, a) -> State StdGen (Maybe (a, a)) randomStep s (x, y) = do (a, gen') <- randomR (0, 2 * pi) <$> get put gen' let (x', y') = (x + s * cos a, y + s * sin a) if x' < 0 || x' > 1 || y' < 0 || y' > 1 then return Nothing else return $ Just (x', y') Something like evalState (lastJustM (randomStep 0.01) (0.5, 0.5)) <$> newStdGen will give us a new data point.

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