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• Haskell Ord instance with a Set

  - by mvid

  I have some code that I would like to use to append an edge to a Node data structure: import Data.Set (Set) import qualified Data.Set as Set data Node = Vertex String (Set Node) deriving Show addEdge :: Node -> Node -> Node addEdge (Vertex name neighbors) destination | Set.null neighbors = Vertex name (Set.singleton destination) | otherwise = Vertex name (Set.insert destination neighbors) However when I try to compile I get this error: No instance for (Ord Node) arising from a use of `Set.insert' As far as I can tell, Set.insert expects nothing but a value and a set to insert it into. What is this Ord?

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• Profile:Object reference not set to an instance of an object

  - by sallalman83

  Hi, i just lunch my web site i used the asp.net routing technology on it, and its work fine in my localhost but when i moved the project to the hosting server(Godaddy.com) its just work fine when there is no virtual sub directories like this(havebreak.com) but when u click on this link (havebreak.com/Registration/) or any other links that contain a virtual sub-directories its give Object reference not set to an instance of an object error on the profile object if (!Profile.IsAnonymous) Line 18: mlvRegistratioin.ActiveViewIndex = 1; i check my IIS settings and found it using the "Integrated pipeline" as recommended (at least at my knowledge), i checked the httpModules and httpHandlers tags under the system.webServer (since my hosting plan use the IIS7) and under the normal tag and every thing is fine then i used the url-rewriting instead of URL-Routing and the same problem exist and i notice that the session also not working in the virtual sub-directories too and by the way the ASP.NET routing work fine with my site its just the profile and session objects that not workin any help will be appreciated

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• Ruby: Calling class method from instance

  - by Peter

  In Ruby, how do you call a class method from one of that class's instances? Say I have class Truck def self.default_make # Class method. "mac" end def initialize # Instance method. Truck.default_make # gets the default via the class's method. # But: I wish to avoid mentioning Truck. Seems I'm repeating myself. end end the line Truck.default_make retrieves the default. But is there a way of saying this without mentioning Truck? It seems like there should be.

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• iphone instance / class method issue

  - by user290031

  Hey All, Okay, so I have a viewController method that has some elements created with interface builder and some I coded myself. I created a view in the IB...lets call it viewOne. I created a loop that creates buttons (through code) and places them on a separate view (viewTwo). This is done in a class method. However, I want the view I made to be opened everytime one of the buttons is clicked. So I did: [button addTarget:self action:@selector(woogoo:) forControlEvents:UIControlEventTouchUpInside]; The woogoo class does the following: +(void) woogoo:(id)sender { //back button [self.view addSubview:viewOne] } However, the program crashes when a button is clicked. I did try making woogoo an instance method but it also crashes in this case too. All I want to do is show viewOne when a button is clicked. Any ideas what I can do?

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• Cannot create instance of 'Ribbon'

  - by user354433

  I'm having trouble using the Ribbon control from the Office 2007 RibbonControlsLibrary.dll. It works for most people but not for me. The fault I get is: Cannot create instance of 'Ribbon' defined in assembly 'RibbonControlsLibrary, Version=3.5.31016.1, Culture=neutral, PublicKeyToken=31bf3856ad364e35'. Exception has been thrown by the target of an invocation The problem is probably not with the code since it works for other people. Its the Ribbon class thats causing the problem. If I remove any references to the Ribbon class but keep the references to RibbonWindow I don't get any exceptions. Any help appreciated

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• Active Record like functionality on array instance variable

  - by rube_noob

  I would like to write a module that provides active record like functionality on an array instance variable. Examples of its use would be x = Container.new x.include(ContainerModule) x.elements << Element.new x.elements.find id module ContainerModule def initialize(*args) @elements = [] class << @elements def <<(element) #do something with the Container... super(element) end def find(id) #find an element using the Container's id self #=> #<Array..> but I need #<Container..> end end super(*args) end end The problem is that I need the Container object within these methods. Any reference to self will return the Array, not the Container object. Is there any way to do this? Thanks!

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• Creating a method that is simultaneously an instance and class method

  - by Mike Axiak

  In Python, I'd like to be able to create a function that behaves both as a class function and an instance method, but with the ability to change behaviors. The use case for this is for a set of serializable objects and types. As an example: >>> class Thing(object): #... >>> Thing.to_json() 'A' >>> Thing().to_json() 'B' I know that given the definition of classmethod() in funcobject.c in the Python source, this looks like it'd be simple with a C module. Is there a way to do this from within python? Thanks!

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• Rails: unexpected behavior updating a shared instance

  - by Pascal Lindelauf

  I have a User object, that is related to a Post object via two different association paths: Post --(has_many)-- comments --(belongs to)-- writer (of type User) Post --(belongs to)-- writer (of type User) Say the following hold: user1.name == "Bill" post1.comments[1].writer == user1 post1.writer == user1 Now when I retrieve the post1 and its comments from the database and I update post1.comments[1].writer like so: post1.comments[1].writer.name = "John" I would expect post1.writer to equal "John" too. But it doesn't! It still equals "Bill". So there seems to be some caching going on, but the kind I would not expect. I would expect Rails to be clever enough to load exactly one instance of the user with name "Bill"; instead is appears to load two individual ones: one for each association path. Can someone explain how this works exactly and how I am to handle these types of situations the "Rails way"?

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• Create Generic Class Instance from Static Method in a Derived Class

  - by user343547

  I have a class in C# with a template and static method similar to class BClass<T> { public static BClass<T> Create() { return new BClass<T>(); } } From this I derive a class and specify a template parameter to the base class class DClass : BClass<int> { } A problem occurs when I try to use the static method to create an instance of D class Program { static void Main(string[] args) { DClass d = DClass.Create(); } } Gives a compiler error "Cannot implicitly convert type 'Test.BClass<int ' to 'Test.DClass'." Adding the below cast leads to a runtime casting exception. DClass d = (DClass)DClass.Create(); Is there any succint way to allow the static method to create instances of the derived class? Ideally I would like the equivalent of a c++ typedef and I don't want the below syntax (which does work). BClass<int> d = DClass.Create();

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• Copying blocks (ie: copying them to instance variables) in Objective-C

  - by RyanWilcox

  I'm trying to understand blocks. I get how to use them normally, when passed directly to a method. I'm interested now in taking a block, storing it (say) in an instance variable and calling it later. The blocks programming guide makes it sound like I can do this, by using Block_copy / retain to copy the block away, but when I try to run it I crash my program. - (void) setupStoredBlock { int salt = 42; m_storedBlock = ^(int incoming){ return 2 + incoming + salt; }; [m_storedBlock retain]; } I try to call it later: - (void) runStoredBlock { int outputValue = m_storedBlock(5); NSLog(@"When we ran our stored blockwe got back: %d", outputValue); [m_storedBlock release]; } Anyone have any insights? (Or, is there something I'm not getting with blocks?) Thank you very much!

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• Weblogic server lib VS instance libext

  - by Sebastien Lorber

  Hello, I use weblogic 10. Its provide an Oracle JDBC driver 10.2.0.2 (in the server/lib on weblogic home). Actually someone at work put a long time ago a 10.2.0.3 driver in instance libext folder. But in production we got a jdbc driver stack (nullpointer :O) and by reverse engineering it seems we are using driver 10.2.0.2. We know that we could change the driver in the server/lib of weblogic but i want to understand. Isn't libext supposed to override server libs like META-INF libs override libext? By the way we are in a strange situation: - We have 2 EAR, and for the exact same treatment in those 2, one will sometime throw the oracle driver nullpointer while the other doesn't - I wonder if one ear isn't using 10.2.0.2 while the other is using 10.2.0.3 (i saw a bug fixed that could fit to our problem for this version). - I need to look better but at first sight both ear use the exact same datasource set in weblogic JNDI resources Any idea?

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• Creating Instance of Python Extension Type in C

  - by Brad Zeis

  I am writing a simple Vector implementation as a Python extension module in C that looks mostly like this: typedef struct { PyObject_HEAD double x; double y; } Vector; static PyTypeObject Vector_Type = { ... }; It is very simple to create instances of Vector while calling from Python, but I need to create a Vector instance in the same extension module. I looked in the documentation but I couldn't find a clear answer. What's the best way to do this?

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• unrecognized selector sent to instance

  - by iamsmug

  My app works fine in the simulator but when I run it on my phone I get this error: 2010-04-05 21:32:45.119 Top Banana[119:207] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* -[MethodViewController setReferringObject:]: unrecognized selector sent to instance 0x16e930' It happens here: -(void)method { [UIView beginAnimations:@"View Flip" context:nil]; [UIView setAnimationDuration:0.50]; [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]; [UIView setAnimationTransition: UIViewAnimationTransitionFlipFromRight forView:self.navigationController.view cache:NO]; MethodViewController *methodViewController = [[MethodViewController alloc] initWithNibName:@"MethodViewController" bundle:0]; NSManagedObject *selectedObject = self.referringObject; methodViewController.referringObject = selectedObject; [self.navigationController pushViewController:methodViewController animated:NO]; methodViewController.title = @"Method"; [UIView commitAnimations]; [MethodViewController release]; } It crashes on this line: methodViewController.referringObject = selectedObject; Not sure how to resolve this as it works in the simulator, I'm sure it is fairly basic to fix, any help will be appreciated.

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• Constructor with non-instance variable assistant?

  - by Robert Fischer

  I have a number of classes that look like this: class Foo(val:BasicData) extends Bar(val) { val helper = new Helper(val) val derived1 = helper.getDerived1Value() val derived2 = helper.getDerived2Value() } ...except that I don't want to hold onto an instance of "helper" beyond the end of the constructor. In Java, I'd do something like this: public class Foo { final Derived derived1, derived2; public Foo(BasicData val) { Helper helper = new Helper(val); derived1 = helper.getDerived1Value(); derived2 = helper.getDerived2Value(); } } So how do I do something like that in Scala? I'm aware of creating a helper object of the same name of the class with an apply method: I was hoping for something slightly more succinct.

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• Is an ArrayList automaticaly declared static ,if it is an instance variable?(Java)

  - by Alex

  Hy ,what i`m trying to do is something like this: private class aClass { private ArrayList idProd; aClass(ArrayList prd) { this.idProd=new ArrayList(prd); } public ArrayList getIdProd() { return this.idProd; } } So if i have multiple instances of ArrayLIst (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); }why all of the aClass objects will return st3 if I access the method getIdProd() for each of them(obj1..obj3)? is an arraylist as a instance variable automatically declared static?

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• Inherit appenders from calling instance in log4j or logback

  - by Lord.Quackstar

  In my program I have 2 separate streams of logging events (calling them streams for simplicity, in reality its 2 appenders). Stream1 contains client logging and Stream2 contains control logging. Now this might seem easy, except that certain classes can be both in the client logging and server logging, depending on the situation. Complicating this further is the fact that a command that a client wants takes place in 2 separate threads (one being fetched randomly from a thread pool), so any kind of tracking with MDC or NDC isn't possible. What would really simplify this is if the logger could inherit the appenders from the calling instance. That way I can setup 2 appenders for 2 loggers and be done. However I have no idea how to do it cleanly or easily. Can anyone offer any advice on how to do so? Note: If something needs to be passed around, I do have a event bean that gets passed to everything in the chain that can be used if necessary.

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• Setting an instance variable from a block

  - by c00lryguy

  How would I achieve something like below so that when I set the s variable within the block, it also sets the @subject instance variable in my Topic class? class Topic def subject(&blk) blk.call(@subject) if block_given? @subject unless block_given? end end my_topic = Topic.new p my_topic.subject #=> nil my_topic.subject do |s| s = ['one', 'two', 'three'] s.pop p s #=> ['one', 'two'] end p my_topic.subject #=> nil... want it to be ['one, 'two']

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• Unmanaged Struct Instance in Managed Class

  - by HeHasMoments

  Hi, I've got a fairly specific problem i've been struggling with for a couple of days. I'm using a native C++, one of the methods takes a ptr to a struct containing fixed size char arrays. e.g. struct userData { char data1[10]; char data2[10]; }; method: short AddItem(long id, userData* data); I'm trying to call to call this from Managed VC++ but I need to have an instance of userData I can keep hold of in my managed class. Can anyone help with how to achieve this? Thanks

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• Installing Skype on Amazon EC2 instance

  - by Adrian

  For my application, I need to have Skype working on my Amazon EC2 Windows instance. I got the application installed and am able to log in, however, I can't make a phone call, since I am getting an 'Can't detect your sound card' error. Since I'm trying to inject audio from an audio file into the phone call, I don't need the sound card on the server. Thus, I need a way to bypass this error message. I have tried installing Virtual Audio Cable, which unfortunately didn't work (even though it worked on my desktop machine).

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• Python 3.0 - Dynamic Class Instance Naming

  - by Jon

  I want to use a while loop to initialize class objects with a simple incremented naming convention. The goal is to be able to scale the number of class objects at will and have the program generate the names automatically. (ex. h1...h100...h1000...) Each h1,h2,h3... being its own instance. Here is my first attempt... have been unable to find a good example. class Korker(object): def __init__(self,ident,roo): self.ident = ident self.roo = roo b = 1 hwinit = 'h' hwstart = 0 while b <= 10: showit = 'h' + str(b) print(showit) #showit seems to generate just fine as demonstrated by print str(showit) == Korker("test",2) #this is the line that fails b += 1 The errors I get range from a string error to a cannot use function type error.... Any help would be greatly appreciated.

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• Two Instances of Sql Server (2005 and 2008)

  - by Felipe

  Hi All, I installed Visual Studio 2008 Professional in my machine and It had installed SQL Server Express 2005 database in machine, and I use it very fine! I installed SQL Managment Studio and works great. So, in this week I Installed Visual Studio 2010 Pro in machine and the setup installed the SQL Server express 2008 and it overwrite the instance of my SQL Server Express 2005. All right, Now, I'd like to know how can I have two instances of the SQL Server Express in my Machine, Express 2005 and Express 2008. I can not access the 2005 , only 2008 :( and my projects uses 2005.. Somebody Help me! thanks Bye

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• Remove only first instance of a character from a list of characters

  - by Luke

  Hi All, Here's what I want to do. I have 2 strings and I want to determine if one string is a permutation of another. I was thinking to simply remove the characters from string A from string B to determine if any characters are left. If no, then it passes. However, I need to make sure that only 1 instance of each letter is removed (not all occurrences) unless there are multiple letters in the word. An example: String A: cant String B: connect Result: -o-nec- Experimenting with NSString and NSScanner has yielded no results so far.

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• SQL Server Error 26 (Error Locating Server/Instance Specified) Only When Debugging

  - by Phsion

  I have a simple asp .net web project I'm working on, and while normally everything is going fine, if I try to debug the site, I get "SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified". I'm not sure if its a weird code issue or a weird SQL Server Issue, but here are the system specs anyway. My dev machine is Windows 7 32-bit, and a Windows Server 2008 VM (on the same Windows 7 Machine) runs both IIS and SQL Server 2008 Express. I haven't had any other problems with the connection string I'm using, and I'm using the simple SA account. Anyhow, thanks for the help.

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• C++, create an instance from a static method

  - by Manux

  Hello, let's say I want my users to use only one class, say SpecialData. Now, this data class would have many methods, and depending on the type of data, the methods do different things, internally, but return externally similar results. Therefore my wanting to have one "public" class and other "private", child classes that would change the behavior of methods, etc... It would be amazingly more simple for some types of data that need to be built to do something like this: SpecialData& sm = SpecialData::new_supermatrix(); and new_supermatrix() would return a SuperMatrix instance, which inherits from most behaviors of SpecialData. my header: static SpecialData& new_supermatrix(); my cpp: SpecialData& SpecialData::new_supermatrix()(){ return SuperMatrix(MATRIX_DEFAULT_MAGNITUDE,1000,1239,FLOAT32,etc...); } The problem is, I get this error, which is probably logical due to the circumstances: invalid initialization of non-const reference of type ‘SpecialData&’ from a temporary of type ‘SpecialData’ So, any ideas?

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• What's the Difference Between These Two Ruby Class Initialaztion Definitions?

  - by michaelmichael

  I'm working through a book on Ruby, and the author used a slightly different form for writing a class initialization definition than he has in previous sections of the book. It looks like this: class Ticket attr_accessor :venue, :date def initialize(venue, date) self.venue = venue self.date = date end end In previous sections of the book, it would've been defined like this: class Ticket attr_accessor :venue, :date def initialize(venue, date) @venue = venue @date = date end end Is there any functional difference between using the setter method, as in the first example vs. using the instance variable in the second? They both seem to work. Even mixing them up seems to work: class Ticket attr_accessor :venue, :date def initialize(venue, date) @venue = venue self.date = date end end

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