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• Debug NAudio MP3 reading difference?

  - by Conrad Albrecht

  My code using NAudio to read one particular MP3 gets different results than several other commercial apps. Specifically: My NAudio-based code finds ~1.4 sec of silence at the beginning of this MP3 before "audible audio" (a drum pickup) starts, whereas other apps (Windows Media Player, RealPlayer, WavePad) show ~2.5 sec of silence before that same drum pickup. The particular MP3 is "Like A Rolling Stone" downloaded from Amazon.com. Tested several other MP3s and none show any similar difference between my code and other apps. Most MP3s don't start with such a long silence so I suspect that's the source of the difference. Debugging problems: I can't actually find a way to even prove that the other apps are right and NAudio/me is wrong, i.e. to compare block-by-block my code's results to a "known good reference implementation"; therefore I can't even precisely define the "error" I need to debug. Since my code reads thousands of samples during those 1.4 sec with no obvious errors, I can't think how to narrow down where/when in the input stream to look for a bug. The heart of the NAudio code is a P/Invoke call to acmStreamConvert(), which is a Windows "black box" call which I can't think how to error-check. Can anyone think of any tricks/techniques to debug this?

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• Why I got some memory problems?

  - by Tattat

  I got this error from XCode: objc[8422]: FREED(id): message release sent to freed object=0x3b120c0 I googled and find that is related to the memory. But I don't know which line of code I go wrong, any ideas? @implementation MyAppDelegate @synthesize window; @synthesize viewController; - (void)applicationDidFinishLaunching:(UIApplication *)application { // Override point for customization after app launch [window addSubview:viewController.view]; [window makeKeyAndVisible]; [self changeScene:[MainGameMenuScene class]]; } - (void)dealloc { [viewController release]; [window release]; [super dealloc]; } - (void) changeScene: (Class) scene { BOOL animateTransition = true; if(animateTransition){ [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:0.5]; [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromLeft forView:window cache:YES]; //does nothing without this line. } if( viewController.view != nil ) { [viewController.view removeFromSuperview]; //remove view from window's subviews. [viewController.view release]; //release gamestate } viewController.view = [[scene alloc] initWithFrame:CGRectMake(0, 0, IPHONE_WIDTH, IPHONE_HEIGHT) andManager:self]; //now set our view as visible [window addSubview:viewController.view]; [window makeKeyAndVisible]; if(animateTransition){ [UIView commitAnimations]; } }

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• Quickly determine if a number is prime in Python for numbers < 1 billion

  - by Frór

  Hi, My current algorithm to check the primality of numbers in python is way to slow for numbers between 10 million and 1 billion. I want it to be improved knowing that I will never get numbers bigger than 1 billion. The context is that I can't get an implementation that is quick enough for solving problem 60 of project Euler: I'm getting the answer to the problem in 75 seconds where I need it in 60 seconds. http://projecteuler.net/index.php?section=problems&id=60 I have very few memory at my disposal so I can't store all the prime numbers below 1 billion. I'm currently using the standard trial division tuned with 6k±1. Is there anything better than this? Do I already need to get the Rabin-Miller method for numbers that are this large. primes_under_100 = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97] def isprime(n): if n <= 100: return n in primes_under_100 if n % 2 == 0 or n % 3 == 0: return False for f in range(5, int(n ** .5), 6): if n % f == 0 or n % (f + 2) == 0: return False return True How can I improve this algorithm?

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• Android Multiple Handlers Design Question

  - by Soumya Simanta

  This question is related to an existing question I asked. I though I'll ask a new question instead of replying back to the other question. Cannot "comment" on my previous question because of a word limit. Marc wrote - I've more than one Handlers in an Activity." Why? If you do not want a complicated handleMessage() method, then use post() (on Handler or View) to break the logic up into individual Runnables. Multiple Handlers makes me nervous. I'm new to Android. Is having multiple handlers in a single activity a bad design ? I'm new to Android. My question is - is having multiple handlers in a single activity a bad design ? Here is the sketch of my current implementation. I've a mapActivity that creates a data thread (a UDP socket that listens for data). My first handler is responsible for sending data from the data thread to the activity. On the map I've a bunch of "dynamic" markers that are refreshed frequently. Some of these markers are video markers i.e., if the user clicks a video marker, I add a ViewView that extends a android.opengl.GLSurfaceView to my map activity and display video on this new vide. I use my second handler to send information about the marker that the user tapped on ItemizedOverlay onTap(int index) method. The user can close the video view by tapping on the video view. I use my third handler for this. I would appreciate if people can tell me what's wrong with this approach and suggest better ways to implement this. Thanks.

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• Valueurl Binding On Large Arrays Causes Sluggish User Interface

  - by Hooligancat

  I have a large data set (some 3500 objects) that returns from a remote server via HTTP. Currently the data is being presented in an NSCollectionView. One aspect of the data is a path pack to the server for a small image that represents the data (think thumbnail for simplicity). Bindings works fantastically for the data that is already returned, and binding the image via a valueurl binding is easy to do. However, the user interface is very sluggish when scrolling through the data set - which makes me think that the NSCollectionView is retrieving all the image data instead of just the image data used to display the currently viewable images. I was under the impression that Cocoa controls were smart enough to only retrieve data for the information that is actually being output to the user interface through lazy loading. This certainly seems to be the case with NSTableView - but I could be misguided on this thought. Should valueurl binding act lazily and, moreover, should it act lazily in an NSCollectionView? I could create a caching mechanism (in fact I already have such a thing in place for another application - see my post here if you are interested http://stackoverflow.com/questions/1740209/populating-nsimage-with-data-from-an-asynchronous-nsurlconnection) but I really don't want to go this route if I don't have to for this specific implementation as the user could potentially change data sets often and may only want small sub-sets of the data. Any suggested approaches? Thanks!

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• When connecting SAP Business One to SQL Server 2005, what is the

  - by Nick

  we have SAP Business One - Fourth Shift Edition running here at a small manufacturing company. The consulting company that has come in to do the installation/implementation uses the "sa" id/pass to initially connect to the database to get the list of companies. From then on, I have to assume that its the sa id/pass that is being used to connect the client software to the database. Is this appropriate? I dont know where this data is being stored... as an ODBC connection? directly in the registry somewhere? Is it secure? Would it be better to set the users network ID in the database security and then use the "trusted connection" setting instead? Or do most people create a separate login in the database for each user and use that in the client settings? seems like the easiest way would be to add the users network login to the sql server security so they can use the "trusted connection"... but then wouldn't that allow ANY software to connect to the database from that machine? So anyways: what are the best-practices for setting this up?

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• Templates, and C++ operator for logic: B contained by set A

  - by James Morris

  In C++, I'm looking to implement an operator for selecting items in a list (of type B) based upon B being contained entirely within A. In the book "the logical design of digital computers" by Montgomery Phister jr (published 1958), p54, it says: F11 = A + ~B has two interesting and useful associations, neither of them having much to do with computer design. The first is the logical notation of implication... The second is notation of inclusion... This may be expressed by a familiar looking relation, B < A; or by the statement "B is included in A"; or by the boolean equation F11= A + ~B = 1. My initial implementation was in C. Callbacks were given to the list to use for such operations. An example being a list of ints, and a struct containting two ints, min and max, for selection purposes. There, selection would be based upon B = A-min && B <= A-max. Using C++ and templates, how would you approach this after having implemented a generic list in C using void pointers and callbacks? Is using < as an over-ridden operator for such purposes... <ugh> evil? </ugh> (or by using a class B for the selection criteria, implementing the comparison by overloading ?)

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• Objective-C autorelease pool not releasing object

  - by Chris

  Hi I am very new to Objective-C and was reading through memory management. I was trying to play around a bit with the NSAutoreleasePool but somehow it wont release my object. I have a class with a setter and getter which basically sets a NSString *name. After releasing the pool I tried to NSLog the object and it still works but I guess it should not? @interface TestClass : NSObject { NSString *name; } - (void) setName: (NSString *) string; - (NSString *) name; @end @implementation TestClass - (void) setName: (NSString *) string { name = string; } - (NSString *) name { return name; } @end int main (int argc, const char * argv[]) { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; TestClass *var = [[TestClass alloc] init]; [var setName:@"Chris"]; [var autorelease]; [pool release]; // This should not be possible? NSLog(@"%@",[var name]); return 0; }

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• How to configure SQLite to run with NHibernate where assembly resolves System.Data.SQLite?

  - by Michael Hedgpeth

  I am using the latest NHibernate 2.1.0Beta2. I'm trying to unit test with SQLite and have the configuration set up as: Dictionary<string, string> properties = new Dictionary<string, string>(); properties.Add("connection.driver_class", "NHibernate.Driver.SQLite20Driver"); properties.Add("dialect", "NHibernate.Dialect.SQLiteDialect"); properties.Add("connection.provider", "NHibernate.Connection.DriverConnectionProvider"); properties.Add("query.substitutions", "true=1;false=0"); properties.Add("connection.connection_string", "Data Source=test.db;Version=3;New=True;"); properties.Add("proxyfactory.factory_class", "NHibernate.ByteCode.LinFu.ProxyFactoryFactory, NHibernate.ByteCode.LinFu"); configuration = new Configuration(); configuration.SetProperties(properties); When I try to run it, I get the following error: NHibernate.HibernateException: The IDbCommand and IDbConnection implementation in the assembly System.Data.SQLite could not be found. Ensure that the assembly System.Data.SQLite is located in the application directory or in the Global Assembly Cache. If the assembly is in the GAC, use <qualifyAssembly/> element in the application configuration file to specify the full name of the assembly. at NHibernate.Driver.ReflectionBasedDriver..ctor(String driverAssemblyName, String connectionTypeName, String commandTypeName) in c:\CSharp\NH\nhibernate\src\NHibernate\Driver\ReflectionBasedDriver.cs: line 26 at NHibernate.Driver.SQLite20Driver..ctor() in c:\CSharp\NH\nhibernate\src\NHibernate\Driver\SQLite20Driver.cs: line 28 So it looks like I need to reference the assembly directly. How would I do this so I don't get this error anymore? I downloaded the latest assembly from here: http://sourceforge.net/projects/sqlite-dotnet2.

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• How to perform spatial partitioning in n-dimensions?

  - by kevin42

  I'm trying to design an implementation of Vector Quantization as a c++ template class that can handle different types and dimensions of vectors (e.g. 16 dimension vectors of bytes, or 4d vectors of doubles, etc). I've been reading up on the algorithms, and I understand most of it: here and here I want to implement the Linde-Buzo-Gray (LBG) Algorithm, but I'm having difficulty figuring out the general algorithm for partitioning the clusters. I think I need to define a plane (hyperplane?) that splits the vectors in a cluster so there is an equal number on each side of the plane. [edit to add more info] This is an iterative process, but I think I start by finding the centroid of all the vectors, then use that centroid to define the splitting plane, get the centroid of each of the sides of the plane, continuing until I have the number of clusters needed for the VQ algorithm (iterating to optimize for less distortion along the way). The animation in the first link above shows it nicely. My questions are: What is an algorithm to find the plane once I have the centroid? How can I test a vector to see if it is on either side of that plane?

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• DSP - Filtering frequencies using DFT

  - by Trap

  I'm trying to implement a DFT-based 8-band equalizer for the sole purpose of learning. To prove that my DFT implementation works I fed an audio signal, analyzed it and then resynthesized it again with no modifications made to the frequency spectrum. So far so good. I'm using the so-called 'standard way of calculating the DFT' which is by correlation. This method calculates the real and imaginary parts both N/2 + 1 samples in length. To attenuate a frequency I'm just doing: float atnFactor = 0.6; Re[k] *= atnFactor; Im[k] *= atnFactor; where 'k' is an index in the range 0 to N/2, but what I get after resynthesis is a slighty distorted signal, especially at low frequencies. The input signal sample rate is 44.1 khz and since I just want a 8-band equalizer I'm feeding the DFT 16 samples at a time so I have 8 frequency bins to play with. Can someone show me what I'm doing wrong? I tried to find info on this subject on the internet but couldn't find any. Thanks in advance.

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• Context Menu on QGraphicsWidget

  - by onurozcelik

  Hi, In my application I have two object type. One is field item, other is composite item. Composite items may contain two or more field items. Here is my composite item implementation. #include "compositeitem.h" CompositeItem::CompositeItem(QString id,QList<FieldItem *> _children) { children = _children; } CompositeItem::~CompositeItem() { } QRectF CompositeItem::boundingRect() const { //Not carefully thinked about it return QRectF(QPointF(-50,-150),QSizeF(250,250)); } void CompositeItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget ) { FieldItem *child; foreach(child,children) { child->paint(painter,option,widget); } } QSizeF CompositeItem::sizeHint(Qt::SizeHint which, const QSizeF &constraint) const { QSizeF itsSize(0,0); FieldItem *child; foreach(child,children) { // if its size empty set first child size to itsSize if(itsSize.isEmpty()) itsSize = child->sizeHint(Qt::PreferredSize); else { QSizeF childSize = child->sizeHint(Qt::PreferredSize); if(itsSize.width() < childSize.width()) itsSize.setWidth(childSize.width()); itsSize.setHeight(itsSize.height() + childSize.height()); } } return itsSize; } void CompositeItem::contextMenuEvent(QGraphicsSceneContextMenuEvent *event) { qDebug()<<"Test"; } My first question is how I can propagate context menu event to specific child. Picture on the above demonstrates one of my possible composite item. If you look on the code above you will see that I print "Test" when context menu event occurs. When I right click on the line symbol I see that "Test" message is printed. But when I right click on the signal symbol "Test" is not printed and I want it to be printed. My second question what cause this behaviour. How do I overcome this.

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• Implement master detail in one datagrid in wpf

  - by Archie

  Hello, I have classes as following: public class Property { public string PropertyName { get; set; } public int SumSubPropertValue; private List<SubProperty> propertyList; public void CalculateSumSubPropertValue { // implementation} } public class SubProperty { public string SubPropertyName { get; set; } public int SubPropertyValue { get; set; } } I have grouped the rows in datagrid on PropertyName . When the user clicks on PropertyName expnader the columns should display SubPropertyName and SubPropertyValue. Also SumSubPropertValue should appear in front of PropertyName in the expander header. My Datagrid is bound to a CollectionViewSource as follows: CollectionViewSource view = new CollectionViewSource(); view.Source = infoList; view.GroupDescriptions.Add(new PropertyGroupDescription("PropertyName")); Where infoList is ObservableCollection<Property>. My datagrid colmns look like <my:DataGrid.Columns> <my:DataGridTextColumn Header="SubPropertyName" Binding="{Binding SubPropertName}" Width="*"/> <my:DataGridTextColumn Header="SubPropertyValue" Binding="{Binding SubPropertyValue}" Width="*"/> </my:DataGrid.Columns> Can someone help me with it?

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• Use Objective-C without NSObject?

  - by Alex I

  I am testing some simple Objective-C code on Windows (cygwin, gcc). This code already works in Xcode on Mac. I would like to convert my objects to not subclass NSObject (or anything else, lol). Is this possible, and how? What I have so far: // MyObject.h @interface MyObject - (void)myMethod:(int) param; @end and // MyObject.m #include "MyObject.h" @interface MyObject() { // this line is a syntax error, why? int _field; } @end @implementation MyObject - (id)init { // what goes in here? return self; } - (void)myMethod:(int) param { _field = param; } @end What happens when I try compiling it: gcc -o test MyObject.m -lobjc MyObject.m:4:1: error: expected identifier or ‘(’ before ‘{’ token MyObject.m: In function ‘-[MyObject myMethod:]’: MyObject.m:17:3: error: ‘_field’ undeclared (first use in this function) EDIT My compiler is cygwin's gcc, also has cygwin gcc-objc package: gcc --version gcc (GCC) 4.7.3 I have tried looking for this online and in a couple of Objective-C tutorials, but every example of a class I have found inherits from NSObject. Is it really impossible to write Objective-C without Cocoa or some kind of Cocoa replacement that provides NSObject? (Yes, I know about GNUstep. I would really rather avoid that if possible...)

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• Exception Handling in ASP.NET MVC and Ajax - [HandleException] filter

  - by Graham

  All, I'm learning MVC and using it for a business app (MVC 1.0). I'm really struggling to get my head around exception handling. I've spent a lot of time on the web but not found anything along the lines of what I'm after. We currently use a filter attribute that implements IExceptionFilter. We decorate a base controller class with this so all server side exceptions are nicely routed to an exception page that displays the error and performs logging. I've started to use AJAX calls that return JSON data but when the server side implementation throws an error, the filter is fired but the page does not redirect to the Error page - it just stays on the page that called the AJAX method. Is there any way to force the redirect on the server (e.g. a ASP.NET Server.Transfer or redirect?) I've read that I must return a JSON object (wrapping the .NET Exception) and then redirect on the client, but then I can't guarantee the client will redirect... but then (although I'm probably doing something wrong) the server attempts to redirect but then gets an unauthorised exception (the base controller is secured but the Exception controller is not as it does not inherit from this) Has anybody please got a simple example (.NET and jQuery code). I feel like I'm randomly trying things in the hope it will work Exception Filter so far... public class HandleExceptionAttribute : FilterAttribute, IExceptionFilter { #region IExceptionFilter Members public void OnException(ExceptionContext filterContext) { if (filterContext.ExceptionHandled) { return; } filterContext.Controller.TempData[CommonLookup.ExceptionObject] = filterContext.Exception; if (filterContext.HttpContext.Request.IsAjaxRequest()) { filterContext.Result = AjaxException(filterContext.Exception.Message, filterContext); } else { //Redirect to global handler filterContext.Result = new RedirectToRouteResult(new RouteValueDictionary(new { controller = AvailableControllers.Exception, action = AvailableActions.HandleException })); filterContext.ExceptionHandled = true; filterContext.HttpContext.Response.Clear(); } } #endregion private JsonResult AjaxException(string message, ExceptionContext filterContext) { if (string.IsNullOrEmpty(message)) { message = "Server error"; //TODO: Replace with better message } filterContext.HttpContext.Response.StatusCode = (int)HttpStatusCode.InternalServerError; filterContext.HttpContext.Response.TrySkipIisCustomErrors = true; //Needed for IIS7.0 return new JsonResult { Data = new { ErrorMessage = message }, ContentEncoding = Encoding.UTF8, }; } }

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• Which articles I've should read before starting to make my custom drawn winforms app?

  - by Dmitriy Matveev

  Hello! I'm currently developing a windows forms application with a lot of user controls. Some of them are just custom drawn buttons or panels and some of them are a compositions of these buttons and panels inside of FlowLayoutPanels and TableLayoutPanels. And the window itself is also custom drawn. I don't have much experience in winforms development, but I've made a proper decomposition of proposed design into user controls and implementation is already almost finished. I've already solved many arisen problems during development by the help of the google, msdn, SO and several dirty hacks (when nothing were helping) and still experiencing some of them. There are a lot of gaps in my knowledge base, since I don't know answers to many questions like: When I should use things like double buffer, suspended layout, suspended redraw ? What should I do with the controls which shouldn't be visible at some moment ? Common performance pitfalls (I think I've fallen in in several ones) ? So I think there should be some great articles which can give some knowledge enough to avoid most common problems and improve performance and maintainability of my application. Maybe some of you can recommend a few?

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• Would it be possible to have a UTF-8-like encoding limited to 3 bytes per character?

  - by dan04

  UTF-8 requires 4 bytes to represent characters outside the BMP. That's not bad; it's no worse than UTF-16 or UTF-32. But it's not optimal (in terms of storage space). There are 13 bytes (C0-C1 and F5-FF) that are never used. And multi-byte sequences that are not used such as the ones corresponding to "overlong" encodings. If these had been available to encode characters, then more of them could have been represented by 2-byte or 3-byte sequences (of course, at the expense of making the implementation more complex). Would it be possible to represent all 1,114,112 Unicode code points by a UTF-8-like encoding with at most 3 bytes per character? If not, what is the maximum number of characters such an encoding could represent? By "UTF-8-like", I mean, at minimum: The bytes 0x00-0x7F are reserved for ASCII characters. Byte-oriented find / index functions work correctly. You can't find a false positive by starting in the middle of a character like you can in Shift-JIS.

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• how useful is Turing completeness? are neural nets turing complete?

  - by Albert

  While reading some papers about the Turing completeness of recurrent neural nets (for example: Turing computability with neural nets, Hava T. Siegelmann and Eduardo D. Sontag, 1991), I got the feeling that the proof which was given there was not really that practical. For example the referenced paper needs a neural network which neuron activity must be of infinity exactness (to reliable represent any rational number). Other proofs need a neural network of infinite size. Clearly, that is not really that practical. But I started to wonder now if it does make sense at all to ask for Turing completeness. By the strict definition, no computer system nowadays is Turing complete because none of them will be able to simulate the infinite tape. Interestingly, programming language specification leaves it most often open if they are turing complete or not. It all boils down to the question if they will always be able to allocate more memory and if the function call stack size is infinite. Most specification don't really specify this. Of course all available implementations are limited here, so all practical implementations of programming languages are not Turing complete. So, what you can say is that all computer systems are just equally powerful as finite state machines and not more. And that brings me to the question: How useful is the term Turing complete at all? And back to neural nets: For any practical implementation of a neural net (including our own brain), they will not be able to represent an infinite number of states, i.e. by the strict definition of Turing completeness, they are not Turing complete. So does the question if neural nets are Turing complete make sense at all? The question if they are as powerful as finite state machines was answered already much earlier (1954 by Minsky, the answer of course: yes) and also seems easier to answer. I.e., at least in theory, that was already the proof that they are as powerful as any computer.

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• Generic object to object mapping with parametrized constructor

  - by Rody van Sambeek

  I have a data access layer which returns an IDataRecord. I have a WCF service that serves DataContracts (dto's). These DataContracts are initiated by a parametrized constructor containing the IDataRecord as follows: [DataContract] public class DataContractItem { [DataMember] public int ID; [DataMember] public string Title; public DataContractItem(IDataRecord record) { this.ID = Convert.ToInt32(record["ID"]); this.Title = record["title"].ToString(); } } Unfortanately I can't change the DAL, so I'm obliged to work with the IDataRecord as input. But in generat this works very well. The mappings are pretty simple most of the time, sometimes they are a bit more complex, but no rocket science. However, now I'd like to be able to use generics to instantiate the different DataContracts to simplify the WCF service methods. I want to be able to do something like: public T DoSomething<T>(IDataRecord record) { ... return new T(record); } So I'd tried to following solutions: Use a generic typed interface with a constructor. doesn't work: ofcourse we can't define a constructor in an interface Use a static method to instantiate the DataContract and create a typed interface containing this static method. doesn't work: ofcourse we can't define a static method in an interface Use a generic typed interface containing the new() constraint doesn't work: new() constraint cannot contain a parameter (the IDataRecord) Using a factory object to perform the mapping based on the DataContract Type. does work, but: not very clean, because I now have a switch statement with all mappings in one file. I can't find a real clean solution for this. Can somebody shed a light on this for me? The project is too small for any complex mapping techniques and too large for a "switch-based" factory implementation.

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• I have two choices of Master's classes this fall. Which is the most useful?

  - by ahplummer

  (For background purposes and context): I am a Software Engineer, and manage other Software Engineers currently. I kind of wear two hats right now: one of a programmer, and one as a 'team lead'. In this regard, I've started going back to school to get my Master's degree with an emphasis in Computer Science. I already have a Bachelor's in Computer Science, and have been working in the field for about 13 years. Our primary development environment is a Windows environment, writing in .NET, Delphi, and SQL Server. Choice #1: CST 798 DATA VISUALIZATION Course Description: Basically, this is a course on the "Processing" language: http://processing.org/ Choice #2: CST 711 INFORMATICS Course Description: (From catalog): Informatics is the science of the use and processing of data, information, and knowledge. This course covers a variety of applied issues from information technology, information management at a variety of levels, ranging from simple data entry, to the creation, design and implementation of new information systems, to the development of models. Topics include basic information representation, processing, searching, and organization, evaluation and analysis of information, Internet-based information access tools, ethics and economics of information sharing.

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• NSDate out of scope

  - by therealtkd

  Having problems with out of scope for NSDate in an iphone app. I have an interface defined like this: @interface MyObject : NSoObject { NSMutableArray *array; BOOL checkThis; NSDate *nextDue; } Now in the implementation I have this: -(id) init { if( (self=[super init]) ) { checkThis = NO; array = [[NSMutableArray alloc] init]; nextDue = [[NSDate date] retain]; NSDate *testDate = [NSDate date]; } return self; } Now, if I trace through the init, before I actually assign the variables checkThis shows as boolean. array shows as pointer 0x0 because it hasn't ben assigned. But the nextDue is showing as 'out of scope'. I don't understand why this is out of scope but the other variables aren't. If I trace through the code until after the variables are assigned, array now shows as being correctly assigned but nextDue is still out of scope. Interestingly, the testDate variable is assigned just fine and the debugger shows this as a valid date. Further interesting point is if I move the mouse over the testDate variable while I am debugging, it shows as an 'NSDate *' type which I would expect since that's its definition. Yet the nextDue, which to me is defined the same way is showing as a '_NSCFDate *'. Any googling I did on the subject said that the retain is the problem, but its actually out of scope before I even try to assign the variable. However, in another class, the same definition for NSDate work ok. It shows as nil before a value is assigned to it. Arghhh

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• Key Tips in WPF

  - by Brad Leach

  Office 2007 and the Ribbon introduced the concept of "Key Tips". In short, every single command in the Ribbon receives a letter which you can press to activate that command. ... The letters are indicated by small "KeyTips" which indicate the letter to press to activate the control. KeyTips are displayed using the Alt key, so using them feels similar to how menu navigation works in Windows. (Source: http://blogs.msdn.com/jensenh/archive/2006/04/12/574930.aspx) An example of the Key Tips can be shown as follows. In this diagram, the use has pressed the ALT key, and is awaiting further input. Are there any WPF Open Source examples of "Key Tips"? How would you go about implementing something like this feature in a generic way (i.e. not requiring a Ribbon)? How would you implement this using a MVVM pattern (given that ICommand does not support InputBindings). Note: ActiPro have implemented this feature in their implementation of a Ribbon, but they have not released source code.

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• casting Collection<SomeClass> to Collection<SomeSuperClass>

  - by skrebbel

  Hi all, I'm sure this has been answered before, but I really cannot find it. I have a java class SomeClass and an abstract class SomeSuperClass. SomeClass extends SomeSuperClass. Another abstract method has a method that returns a Collection<SomeSuperClass>. In an implementation class, I have a Collection<SomeClass> myCollection I understand that I cannot just return myCollection, because Collection<SomeClass> does not inherit from Collection<SomeSuperClass>. Nevertheless, I know that everything in myCollection is a SomeSuperClass because after all, they're SomeClass objects which extend SomeSuperClass. How can I make this work? I.e. I want public class A { private Collection<SomeClass> myCollection; public Collection<SomeSuperClass> getCollection() { return myCollection; //compile error! } } The only way I've found is casting via a non-generic type and getting unchecked warnings and whatnot. There must be a more elegant way, though? I feel that also using Collections.checkedSet() and friends are not needed, since it is statically certain that the returned collection only contains SomeClass objects (this would not be the case when downcasting instead of upcasting, but that's not what I'm doing). What am I missing? Thanks!

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• Haskell math performance

  - by Travis Brown

  I'm in the middle of porting David Blei's original C implementation of Latent Dirichlet Allocation to Haskell, and I'm trying to decide whether to leave some of the low-level stuff in C. The following function is one example—it's an approximation of the second derivative of lgamma: double trigamma(double x) { double p; int i; x=x+6; p=1/(x*x); p=(((((0.075757575757576*p-0.033333333333333)*p+0.0238095238095238) *p-0.033333333333333)*p+0.166666666666667)*p+1)/x+0.5*p; for (i=0; i<6 ;i++) { x=x-1; p=1/(x*x)+p; } return(p); } I've translated this into more or less idiomatic Haskell as follows: trigamma :: Double -> Double trigamma x = snd $ last $ take 7 $ iterate next (x' - 1, p') where x' = x + 6 p = 1 / x' ^ 2 p' = p / 2 + c / x' c = foldr1 (\a b -> (a + b * p)) [1, 1/6, -1/30, 1/42, -1/30, 5/66] next (x, p) = (x - 1, 1 / x ^ 2 + p) The problem is that when I run both through Criterion, my Haskell version is six or seven times slower (I'm compiling with -O2 on GHC 6.12.1). Some similar functions are even worse. I know practically nothing about Haskell performance, and I'm not terribly interested in digging through Core or anything like that, since I can always just call the handful of math-intensive C functions through FFI. But I'm curious about whether there's low-hanging fruit that I'm missing—some kind of extension or library or annotation that I could use to speed up this numeric stuff without making it too ugly.

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• How do I edit a row in NSTableView to allow deleting the data in that row and replacing with new d

  - by lampShade

  I'm building a to-do-list application and I want to be able to edit the entries in the table and replace them with new entries. I'm close to being able to do what I want but not quit. Here is my code so far: /* IBOutlet NSTextField *textField; IBOutlet NSTabView *tableView; IBOutlet NSButton *button; NSMutableArray *myArray; */ #import "AppController.h" @implementation AppController -(IBAction)addNewItem:(id)sender { [myArray addObject:[textField stringValue]]; [tableView reloadData]; } - (int)numberOfRowsInTableView:(NSTableView *)aTableView { return [myArray count]; } - (id)tableView:(NSTableView *)aTableView objectValueForTableColumn:(NSTableColumn *)aTableColumn row:(int)rowIndex { return [myArray objectAtIndex:rowIndex]; } - (id)init { [super init]; myArray = [[NSMutableArray alloc] init]; return self; } -(IBAction)removeItem:(id)sender { NSLog(@"This is the index of the selected row: %d",[tableView selectedRow]); NSLog(@"the clicked row is %d",[tableView clickedRow]); [myArray replaceObjectAtIndex:[tableView selectedRow] withObject:[textField stringValue]]; [myArray addObject:[textField stringValue]]; //[tableView reloadData]; } @end

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