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• - Default value of variables at the time of declaration -

  - by gotye

  Hey guys, I was wondering what was the default values of variables before I intialize them .. For example, if I do : //myClass.h BOOL myBOOL; // default value ? NSArray *myArray; // default value ? NSUInteger myInteger; // default value ? Some more examples here : //myClass.m // myArray is not initialized, only declared in .h file if ([myArray count] == 0) { // TRUE or FALSE ? // do whatever } More generally, what is returned when I do : [myObjectOnlyDeclaredAndNotInitialized myCustomFunction]; Thank you for your answers. Gotye.

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• iPhone init method return type

  - by William Jockusch

  Suppose we are writing a class (let's call it Class) in an iPhone program. In all the samples out there, the init methods are typically declared like this: -(id) initWithFoo: (Foo *) foo My question is: would it be more logical to do the following? Why or why not? -(Class *) initWithFoo: (Foo *) foo

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• Initialize window code Mac OS X

  - by Jarle

  I'm currently reading "the red book" for learning OpenGL properly, and in one of the first examples, the author writes a line that says "InitializeAWindowPlease();" as a place holder for the code that will make a window to draw the OpenGL content in. Since I'm using Xcode for my programing, I know that I "get" a window to work with automatically (and that I have to make my own OpenGL view in interfacebuilder). How can I make this with pure code? I'm trying to learn programming, and I'm not to happy about taking "shortcuts" all the time. How can I make a window to draw my openGL stuff in? With Objective-C and C code I would love to see it. My goal is that I can make it without opening interface builder at all:)

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• Draw a parallel line

  - by VOX

  I have x1,y1 and x2,y2 which forms a line segment. How can I get another line x3,y3 - x4,y4 which is parallel to the first line as in the picture. I can simply add n to x1 and x2 to get a parallel line but it is not what i wanted. I want the lines to be as parallel in the picture.

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• Java: Initializing a public static field in superclass that needs a different value in every subclas

  - by BinaryMuse

  Good evening, I am developing a set of Java classes so that a container class Box contains a List of a contained class Widget. A Widget needs to be able to specify relationships with other Widgets. I figured a good way to do this would be to do something like this: public abstract class Widget { public static class WidgetID { // implementation stolen from Google's GWT private static int nextHashCode; private final int index; public WidgetID() { index = ++nextHashCode; } public final int hashCode() { return index; } } public abstract WidgetID getWidgetID(); } so sublcasses of Widget could: public class BlueWidget extends Widget { public static final WidgetID WIDGETID = new WidgetID(); @Override public WidgetID getWidgetID() { return WIDGETID; } } Now, BlueWidget can do getBox().addWidgetRelationship(RelationshipTypes.SomeType, RedWidget.WIDGETID, and Box can iterate through it's list comparing the second parameter to iter.next().getWidgetID(). Now, all this works great so far. What I'm trying to do is keep from having to declare the public static final WidgetID WIDGETID in all the subclasses and implement it instead in the parent Widget class. The problem is, if I move that line of code into Widget, then every instance of a subclass of Widget appears to get the same static final WidgetID for their Subclassname.WIDGETID. However, making it non-static means I can no longer even call Subclassname.WIDGETID. So: how do I create a static WidgetID in the parent Widget class while ensuring it is different for every instance of Widget and subclasses of Widget? Or am I using the wrong tool for the job here? Thanks!

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• Why is my variable uninitialized in a separate if test?

  - by user2932733

  For the first run, I need to use dates that are six months prior to the last MySQL date $row_recent[0]. For all of the runs after 1, I am using a previous variable to store the previous date and then decrease the date by 6 months. I have confirmed that the first if test produces the expected result. (MySQL date - 6 Months). However, the second if test outputs $startdate6m as the PHP default due to $previous_6m being uninitialized. Any idea why it won't recognize $previous_6m = $initial6m? <?php while ($run_number < 15) { $run_number++; if($run_number == 1){ if ($month <= 06){ $year6m = date("Y", strtotime($row_recent[0]))-1; $month6m = str_pad((12-(6-date("m", strtotime($row_recent[0])))), 2, "0", STR_PAD_LEFT); $startdate6m = "'".$year6m."-".$month6m."-01'"; $end_date = $startdate6m; $initial6m = $startdate6m; } else{ $year6m = date("Y", strtotime($row_recent[0])); $month6m = str_pad(date("m", strtotime($row_recent[0]))-6, 2, "0", STR_PAD_LEFT); $startdate6m = "'".$year6m."-".$month6m."-01'"; $end_date = $startdate6m; $initial6m = $startdate6m; } } $previous_6m = $initial6m; if($run_number > 1){ # 6 Month # Decrement date by 6 months $month6m = date("m", strtotime($previous_6m)); if ($month6m <= 06){ $year6m = date("Y", strtotime($previous_6m))-1; $month6m = str_pad((12-(6-date("m", strtotime($previous_6m)))), 2, "0", STR_PAD_LEFT); $startdate6m = "'".$year6m."-".$month6m."-01'"; $end_date = $startdate6m; } else{ $year6m = date("Y", strtotime($previous_6m)); $month6m = str_pad(date("m", strtotime($previous_6m))-6, 2, "0", STR_PAD_LEFT); $startdate6m = "'".$year6m."-".$month6m."-01'"; $end_date = $startdate6m; } } $previous_6m = $startdate6m; } ?>

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• What's the point of this in objective-c

  - by Mk12

  SomeObject *temp = [[SomeObject alloc] init] self.theObject = temp; [temp release]; Why is it always done that way? Why not self.theObject = [[SomeObject alloc] init];

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• log4net initialisation

  - by Ruben Bartelink

  I've looked hard for duplicates but have to ask the following, no matter how basic it may seem, to get it clear once and for all! In a fresh Console app using log4net version 1.2.10.0 on VS28KSP1 on 64 bit W7, I have the following code:- using log4net; using log4net.Config; namespace ConsoleApplication1 { class Program { static readonly ILog _log = LogManager.GetLogger(typeof(Program)); static void Main(string[] args) { _log.Info("Ran"); } } } In my app.config, I have: <?xml version="1.0" encoding="utf-8" ?> <configuration> <configSections> <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" /> </configSections> <log4net> <appender name="RollingFileAppender" type="log4net.Appender.RollingFileAppender"> <file value="Program.log" /> <lockingModel type="log4net.Appender.FileAppender+MinimalLock" /> <appendToFile value="true" /> <rollingStyle value="Size" /> <maxSizeRollBackups value="10" /> <maximumFileSize value="1MB" /> <staticLogFileName value="true" /> <layout type="log4net.Layout.PatternLayout"> <conversionPattern value="[%username] %date [%thread] %-5level %logger [%property{NDC}] - %message%newline" /> </layout> </appender> <root> <level value="DEBUG" /> <appender-ref ref="RollingFileAppender" /> </root> </log4net> </configuration> This doesnt write anything, unless I either add an attribute: [ assembly:XmlConfigurator ] Or explicitly initialise it in Main(): _log.Info("This will not go to the log"); XmlConfigurator.Configure(); _log.Info("Ran"); This raises the following questions: I'm almost certain I've seen it working somewhere on some version of log4net without the addition of the assembly attribute or call in Main. Can someone assure me I'm not imagining that? Can someone please point me to where in the doc it explicitly states that both the config section and the initialisation hook are required - hopefully with an explanation of when this changed, if it did? I can easily imagine why this might be the policy -- having the initialisation step explicit to avoid surprises etc., it's just that I seem to recall this not always being the case... (And normally I have the config in a separate file, which generally takes configsections out of the picture)

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• Is it true that the assigned final object field may still be null inside a constructor?

  - by Tom Brito

  Is it true that the assigned final object field may still be null inside a constructor? class MyClass { private final Object obj = new Object(); public MyClass() { System.out.println(obj); // may print null? } } if yes, isn't this a bug?

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• Angles between two n-dimensional vectors in Python

  - by Peter

  In need to determine the angle(s) between two n-dimensional vectors in Python. For example, the input can be two lists like the following: [1,2,3,4] and [6,7,8,9]. Can anybody help me? Thanks in advance!

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• How do I initialize attributes when I instantiate objects in Rails?

  - by nfm

  Clients have many Invoices. Invoices have a number attribute that I want to initialize by incrementing the client's previous invoice number. For example: @client = Client.find(1) @client.last_invoice_number > 14 @invoice = @client.invoices.build @invoice.number > 15 I want to get this functionality into my Invoice model, but I'm not sure how to. Here's what I'm imagining the code to be like: class Invoice < ActiveRecord::Base ... def initialize(attributes = {}) client = Client.find(attributes[:client_id]) attributes[:number] = client.last_invoice_number + 1 client.update_attributes(:last_invoice_number => client.last_invoice_number + 1) end end However, attributes[:client_id] isn't set when I call @client.invoices.build. How and when is the invoice's client_id initialized, and when can I use it to initialize the invoice's number? Can I get this logic into the model, or will I have to put it in the controller?

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• BPEL, initialize variable and repeating onAlarm eventHandler

  - by Michael

  I have a little problem I can't solve so far. In BPEL I want to create an onAlarm eventHandler which fires immediatly (i.e. the "for" element is set to 'PT0S') and repeats every 2 seconds. This eventHandler shall contain a counter which increments every time the alarm fires. The question is: How to initialize the counter? If the variable will be initialized within the onAlarm scope the value would not increment anymore. In the "normal" control flow the value also cannot be initialized, because it is not defined if the process or the onAlarm scope runs first. So I would get every now and then an uninitializedVariable exception. My solution would be to not initialize the variable neither in the process scope nor in the onAlarm scope, but create a faultHandler wherein the variable will be initialized and afterwards the onAlarm flow will be executed. Problem is every uninitializedVariable execution will be caught now by this faultHandler and there may be another too. So is there another possibility to deal with this problem or can I somehow find out which variable wasn't initialized properly so the faultHandler can get two control flows? The solution should work on every BPEL engine. Thanks, Michael

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• Replacing a colour/colours in a movieclip with different colours?

  - by Oli

  I am trying to take a movieclip of a character and change the colour of their clothes. The character is comprised of vectors. So far I have semi-sucessfully used this method: stop the movieclip take the bitmap data from the current frame use threshold to replace the colour store the resulting bitmap data in an array add an onenterframe function - clear the current frame and add the bitmap data from the processed data in the array So - this works pretty well. Each frame is only processed once at the beginning and then the write to the movieclip is very quick. However! As the replacement is being performed on a bitmap there is an amount of aliasing that takes place to remove jaggies/pixelation. This produces colours that are not matched using threshold. So the main colour is replaced correctly but it is surrounded by a halo of mixed colours :( I am sure there should be a better way to do this. Any ideas or answers would be greatly apreciated - Thanks.

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• How to JSON serialize math vector type in F#?

  - by The_Ghost

  Hello! I'm trying to serialize "vector" (Microsoft.FSharp.Math) type. And I get that error: Exception Details: System.Runtime.Serialization.SerializationException: Type 'Microsoft.FSharp.Math.Instances+FloatNumerics@115' with data contract name 'Instances.FloatNumerics_x0040_115:http://schemas.datacontract.org/2004/07/Microsoft.FSharp.Math' is not expected. Add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer. I have tried to put KnownType attribute and some other stuff, but nothing helps! Could someone know the answer? This is the code I use: // [< KnownType( typeof<vector> ) >] type MyType = vector let public writeTest = let aaa = vector [1.1;2.2] let serializer = new DataContractJsonSerializer( typeof<MyType> ) let writer = new StreamWriter( @"c:\test.txt" ) serializer.WriteObject(writer.BaseStream, aaa) writer.Close()

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• iPhone NSTimer OpenGL problem

  - by Toby Wilson

  I've got a problem that only seems to occur on the device, not in the simulator. My app's animation is started and stopped using these methods: NSTimer* animationTimer; -(void)startAnimation { if(animationTimer = nil) animationTimer = [NSTimer scheduledTimerWithTimeInterval:1.0f/60.0f target:self selector:@selector(drawView) userInfo:nil repeats:YES]; } -(void)stopAnimation { [animationTimer invalidate]; animationTimer = nil; } In the simulator this works fine and drawView starts being called at 60fps. On the device (testing on iPod Touch), the scheduleTimerWithTimeInterval method doesn't seem to work. Furthermore, [animationTimer invalidate] causes EXC_BAD_ACCESS. I've spotted an obvious but minor flaw; adding if(animationTimer != nil) to the stopAnimation method will prevent the crash, but doesn't solve the problem of the animation timer not being properly initialised. Edit: The above doesn't prevent a crash. animationTimer != nil yet calling invalidate causes EXC_BAD_ACCESS. Should also add, this problem doesn't occur all the time on the device. Maybe 40% of the time.

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• How to sort TBB concurrent_vector or concurrent_queue?

  - by Jackie

  Now I have a solver in that I need to keep a set of self-defined data type objects in a concurrent_vector or queue. It has to be concurrent because the objects come from different threads.With this concurrent container, I hope to sort these objects, eliminate duplicates and send them back when other threads need them. However, I know TBB offers concurrent_vector and concurrent_queue which can be read and written concurrently from different threads. But how to sort the objects inside a container? Does everyone know how to do that? Thanks.

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• Initialisation of Objects Syntax question

  - by Brock Woolf

  When I initialise a struct in C (Node is the struct): struct Node { /* Non-Relevant code */ }; This works: Node *rootNode = new Node(); but so does this: Node *rootNode = new Node; Is there a difference, and what is the difference between using () or not using the brackets? Just off memory, I think the same applies above for C++ object initialisations. What is happening here?

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• Why a variable is seen in the loop and is not seen outside the loop?

  - by Roman

  I have the following code: String serviceType; ServiceBrowser tmpBrowser; for (String playerName: players) { serviceType = "_" + playerName + "._tcp"; tmpBrowser = BrowsersGenerator.getBrowser(serviceType); tmpBrowser.browse(); System.out.println(tmpBrowser.getStatus()); } System.out.println(tmpBrowser.getStatus()); The compiler complains about the last line. It writes "variable tmpBrowser might not been initialized". If I comment the last line the compile does not complain.

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• Why does javac complain about not initialized variable?

  - by Marcus

  For this Java code: String var; clazz.doSomething(var); Why does the compiler report this error: Variable 'var' might not have been initialized I thought all variables or references were initialized to null. Why do you need to do: String var = null; ??

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• Could not initialize proxy - No Session again

  - by Iapilgrim

  I get these error log when viewing a page ERROR [TP-Processor11] (LazyInitializationException.java:42) - could not initialize proxy - no Session org.hibernate.LazyInitializationException: could not initialize proxy - no Session at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:132) at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:174) at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:190) at org.osmoz.contents.model.enm.ContentType_$$_javassist_71.getDefaultShortMode(ContentType_$$_javassist_71.java) at org.osmoz.contents.web.tapestry.components.EnmContentZone.getTemplate(EnmContentZone.java:67) at org.osmoz.contents.web.tapestry.base.AbstractRawContentZone.getContent(AbstractRawContentZone.java:67) at $PropertyConduit_1276091af82.get($PropertyConduit_1276091af82.java) at org.apache.tapestry5.internal.bindings.PropBinding.get(PropBinding.java:58) at org.apache.tapestry5.internal.structure.InternalComponentResourcesImpl$1.read(InternalComponentResourcesImpl.java:510) at org.apache.tapestry5.internal.structure.InternalComponentResourcesImpl$1.read(InternalComponentResourcesImpl.java:496) at org.apache.tapestry5.corelib.components.OutputRaw._$read_parameter_value(OutputRaw.java) at org.apache.tapestry5.corelib.components.OutputRaw.beginRender(OutputRaw.java:43) at org.apache.tapestry5.corelib.components.OutputRaw.beginRender(OutputRaw.java) at I know the problem is Session has been closed. But I really don't know why this error occur not so often that why I don't know the root cause is. Enviroment: Tapestry5, JPA, Hibernate 3.3.2.GA I've set <filter-class>org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter</filter-class> in web.xml also

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• Mapping Vectors

  - by Dan Snyder

  Is there a good way to map vectors? Here's an example of what I mean: vec0 = [0,0,0,0,0,0,0,0,0,0,0] vec1 = [1,4,2,7,3,2] vec2 = [0,0,0,0,0,0,0,0,0] vec2 = [7,2,7,9,9,6,1,0,4] vec4 = [0,0,0,0,0,0] mainvec = [0,0,0,0,0,0,0,0,0,0,0,1,4,2,7,3,2,0,0,0,0,0,0,0,0,0,7,2,7,9,9,6,1,0,4,0,0,0,0,0,0] Lets say mainvec doesn't exist (I'm just showing it to you so you can see the general data structure in mind. Now say I want mainvec(12) which would be 4. Is there a good way to map the call of these vectors without just stitching them together into a mainvec? I realize I could make a bunch of if statements that test the index of mainvec and I can then offset each call depending on where the call is within one of the vectors, so for instance: mainvec(12) = vec1(1) which I could do by: mainvec(index) if (index >=13) vect1(index-11); I wonder if there's a concise way of doing this without if statements. Any Ideas?

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• Is it safe to call a function to intialize a class in a ctor list?

  - by Michael Dorgan

  I have Angle class that I want initialized to a random value. The Angle constructor can accept an int from a random() function. Is it safe to place this call in the ctor list: foo::foo() : Angle(random(0xFFFF)) {...} or do I have to do it in the body of the constructor? foo::foo() { Angle = Angle(random(0xFFFF)); ...} If it matters, the foo class is derived from another class and does have virtual methods. In addition, no exception handling is allowed in our app.

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• how to init and malloc array to pointer on C

  - by DoronS

  Hi all, looks like a memory leak when i try to initializing an array of pointers, this my code: void initLabelTable(){ register int i; hashNode** hp; labelHashTable = (hashNode**) malloc(HASHSIZE*sizeof(hashNode*)); hp = labelHashTable; for(i=0; i<HASHSIZE; i++) { *(hp+i) = NULL; } } any idea?

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• Java init method

  - by Johan Sjöberg

  What's a good way to make sure an init method is invoked in java? The alternatives I see are Don't test it, let the method fail by itself, likely by a NullPointerException Test if method was initialized or throw public void foo() { if (!inited) { throw new IllegalArgumentException("not initalized"); } ... } Delagate public void foo() { if (!inited) { throw new IllegalArgumentException("not initalized"); } fooInternal(); } private void fooInternal(){ ... }; Always init, and make init a noop otherwise public void foo() { init(); ... } public void init() { if(!inited) { ... } } Silently init public void foo() { if (!inited) { init(); } ... } Most of these approaches are very verbose and decreases overall readability.

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• How are Flash library symbols constructed? Why are width/height already available in constructor?

  - by Triynko

  Suppose I draw a square on the stage, convert it to a symbol, export it for ActionScript with a classname of "MySquare" (and of course a base class of MovieClip). How is it that in the MySquare constructor, the width and height of this MovieClip are already available? In fact, any named instances in the clip are also available. I'm confused about how the Flash player seems to be able to pre-construct my movie clip by populating its properties and child clips before my constructor for the class ever runs. I thought that it would have to first construct the clip, calling my constructor code, and then construct and add any children, but obviously the player is doing something special for clips designed in the Flash authoring environment.

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