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  • Add to SortedSet<T> and its complexity

    - by Andrei Taptunov
    MSDN states the following SortedSet(T).Add Method : If Count is less than the capacity of the internal array, this method is an O(1) operation. Could someone please explain "how so"? I mean when adding new value we need to find a correct place to add a value (comparing it with another values) and internal implementation looks like a "Red-Black tree" with O (log N) insertion complexity.

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  • How to Create Own HashMap in Java?

    - by Taranfx
    I know about hashing algorithm and hashCode() to convert "key" into an equivalent integer (using some mathematically random expression) that is then compressed and stored into buckets. But can someone point me to an implementation or at least data structure that should be used as baseline? I haven't found it anywhere on the web.

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  • How to edit an default Xcode template?

    - by HelloMoon
    When I create an NSObject subclass, I always get an empty implementation. There are some things I always put in my code like pragma marks and -dealloc methods. I prefer to just delete stuff that I don't need over writing it with typos from scratch every time I need it. I need -dealloc and -init almost always, but they don't ship with the default template. Is there a way to customize what's in there?

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  • Java equivalent of C++ std::map?

    - by Rudiger
    I'm looking for a Java class with the characteristics of C++ std::map's usual implementation (as I understand it, a self-balancing binary search tree): O(log n) performance for insertion/removal/search Each element is composed of a unique key and a mapped value Keys follow a strict weak ordering I'm looking for implementations with open source or design documents; I'll probably end up rolling my own support for primitive keys/values. This question's style is similar to: Java equivalent of std::deque, whose answer was "ArrayDeque from Primitive Collections for Java".

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  • Saving data in custom class via AppDelegate

    - by redspike
    I can't seem to save data to a custom instance object in my AppDelegate. My custom class is very simple and is as follows: Person.h ... @interface Person : NSObject { int _age; } - (void) setAge: (int) age; - (int) age; @end Person.m #import "Person.h" @implementation Person - (void) setAge:(int) age { _age = age; } - (int) age { return _age; } @end I then create an instance of Person in the AppDelegate class: AppDelegate.h @class Person; @interface AccuTaxAppDelegate : NSObject <UIApplicationDelegate> { ... Person *person; } ... @property (nonatomic, retain) Person *person; @end AppDelegate.m ... #import "Person.h" @implementation AccuTaxAppDelegate ... @synthesize person; - (void)applicationDidFinishLaunching:(UIApplication *)application { // Override point for customization after app launch [window addSubview:[navigationController view]]; [window makeKeyAndVisible]; } - (void)applicationWillTerminate:(UIApplication *)application { // Save data if appropriate } #pragma mark - #pragma mark Memory management - (void)dealloc { [navigationController release]; [window release]; [person release]; [super dealloc]; } @end Finally, in my ViewController code I grab a handle on AppDelegate and then grab the person instance, but when I try to save the age it doesn't seem to work: MyViewController ... - (void)textFieldDidEndEditing:(UITextField *)textField { NSString *textAge = [textField text]; int age = [textAge intValue]; NSLog(@"Age from text field::%i", age); AppDelegate *appDelegate = (AppDelegate *)[UIApplication sharedApplication].delegate; Person *myPerson = (Person *)[appDelegate person]; NSLog(@"Age before setting: %i", [myPerson age]); [myPerson setAge:age]; NSLog(@"Age after setting: %i", [myPerson age]); [textAge release]; } ... The output of the above NSLogs are: [Session started at 2010-05-04 18:29:22 +0100.] 2010-05-04 18:29:28.260 AccuTax[16235:207] Age in text field:25 2010-05-04 18:29:28.262 AccuTax[16235:207] Age before setting: 0 2010-05-04 18:29:28.263 AccuTax[16235:207] Age after setting: 0 Any ideas why 'age' isn't being stored? I'm relatively new to Obj-C so please forgive me if I'm missing something very simple!

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  • C# SQL: What is the best way to implement a dynamic table?

    - by SirMoreno
    I want to allow the user to add columns to a table in the UI. The UI: Columns Name:__ Columns Type: Number/String/Date My Question is how to build the SQL tables and C# objects so the implementation will be efficient and scalable. My thought is to build two SQL tables: TBL 1 - ColumnsDefinition: ColId, ColName, ColType[Text] TBL 2 - ColumnsValues: RowId, ColId, Value [Text] I want the solution to be efficient in DB space, and I want to allow the user to sort the dynamic columns. I work on .NET 3.5 MSSQL 2008. Thanks.

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  • approximating log10[x^k0 + k1]

    - by Yale Zhang
    Greetings. I'm trying to approximate the function Log10[x^k0 + k1], where .21 < k0 < 21, 0 < k1 < ~2000, and x is integer < 2^14. k0 & k1 are constant. For practical purposes, you can assume k0 = 2.12, k1 = 2660. The desired accuracy is 5*10^-4 relative error. This function is virtually identical to Log[x], except near 0, where it differs a lot. I already have came up with a SIMD implementation that is ~1.15x faster than a simple lookup table, but would like to improve it if possible, which I think is very hard due to lack of efficient instructions. My SIMD implementation uses 16bit fixed point arithmetic to evaluate a 3rd degree polynomial (I use least squares fit). The polynomial uses different coefficients for different input ranges. There are 8 ranges, and range i spans (64)2^i to (64)2^(i + 1). The rational behind this is the derivatives of Log[x] drop rapidly with x, meaning a polynomial will fit it more accurately since polynomials are an exact fit for functions that have a derivative of 0 beyond a certain order. SIMD table lookups are done very efficiently with a single _mm_shuffle_epi8(). I use SSE's float to int conversion to get the exponent and significand used for the fixed point approximation. I also software pipelined the loop to get ~1.25x speedup, so further code optimizations are probably unlikely. What I'm asking is if there's a more efficient approximation at a higher level? For example: Can this function be decomposed into functions with a limited domain like log2((2^x) * significand) = x + log2(significand) hence eliminating the need to deal with different ranges (table lookups). The main problem I think is adding the k1 term kills all those nice log properties that we know and love, making it not possible. Or is it? Iterative method? don't think so because the Newton method for log[x] is already a complicated expression Exploiting locality of neighboring pixels? - if the range of the 8 inputs fall in the same approximation range, then I can look up a single coefficient, instead of looking up separate coefficients for each element. Thus, I can use this as a fast common case, and use a slower, general code path when it isn't. But for my data, the range needs to be ~2000 before this property hold 70% of the time, which doesn't seem to make this method competitive. Please, give me some opinion, especially if you're an applied mathematician, even if you say it can't be done. Thanks.

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  • How do you hook a C++ compiled dll function to a sql database?

    - by Thomas
    I want to do something like: lastName SIMILARTO(lastName, 'Schwarseneger', 2) where lastName is the field in the database, 'Schwarseneger' is the value that lastName field is being compared to and 2 is the maximum number of characters (edit distance) that can differ between the lastName field, and the entered value. I can implement the SIMILARTO function in C++ using the Levenshtein distance (http://en.wikipedia.org/wiki/Levenshtein_distance), but how do hook the function in a dll to a mySQL implementation?

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  • Why does C# allow abstract class with no abstract members?

    - by fatcat1111
    The C# spec, section 10.1.1.1, states: An abstract class is permitted (but not required) to contain abstract members. This allows me to create classes like this: public abstract class A { public void Main() { // it's full of logic! } } This is really a concrete class; it's only abstract in so far as one can't instantiate it. If inheritors don't actually have to provide implementation, then why call it abstract?

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  • ModelMap usage in Spring

    - by Anna
    What are the benifits of using ModelMap instead of a simple Map in Spring MVC. I see in the code implementation that they put the datatype of the attribute added in the map as key instead to be made available on the form. Can anyone explain with an example.

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  • No pre-built ActionBar for Android pre-3.0?

    - by Ollie C
    I note the release a few days ago of the static library bringing fragments to Android versions prior to 3.0, but does this library include the ActionBar? I suspect not. I assume that for an app that will work on pre-3.0 versions, that it needs a hand-built ActionBar implementation for versions up to 2.3 and then to use the OS default ActionBar in v3.0? for some reason I assumed the library had ActionBar in it, but as I dig further I'm not finding any evidence of its presence.

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  • Is there any open source AI engine?

    - by Andrei Savu
    I am searching for an open source AI engine implemented in C/C++, ActionScript or Java with no success. Do you know any open source implementation? Update: Thanks for answers! I had no idea how vast the AI field is. I am working on a sample application. I want to add intelligent behavior over a physics engine. I need some sort ai engine designed for games.

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  • Java Interger: what is faster comparison or subtraction?

    - by Vladimir
    I've found that java.lang.Ingteger implementation of compareTo method looks as follows: public int compareTo(Integer anotherInteger) { int thisVal = this.value; int anotherVal = anotherInteger.value; return (thisVal<anotherVal ? -1 : (thisVal==anotherVal ? 0 : 1)); } The question is why use comparison instead of subtraction: return thisVal - anotherVal;

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  • UINavigationBar Background Image Problem

    - by tobi
    i have set my navigationbar background with this code in my App delegate: @implementation UINavigationBar (UINavigationBarCategory) - (void)drawRect:(CGRect)rect { UIImage *backgroundImage = [UIImage imageNamed: @"Nav-rightpane.png"]; CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, self.frame.size.width, self.frame.size.height), backgroundImage.CGImage); } @end This works perfect but now i must change the background to the default at UIPopoverController. Any idea for this? Thanks

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  • How to use Hessian in iphone?

    - by Shikhar
    Hello, Is there any one who can help me to understand how we can implement Hessian protocol in iPhone. I have Hessian kit, but its not that straightforward as I thought. Please help me, either by Hello World example or some link which explain Hessian implementation. Thanks Shikhar

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  • OpenID on stackoverlow.com [closed]

    - by Thomas Paine
    I'm trying to login to stackoverlow with openID and I am receiving an error from google saying "Request-URI Too Large". Is this an issue with google or an issue with stackoverlow's implementation of OpenID? My OpenID url: http://54.org/thomas The URL

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  • Is a Multi-DAL Approach the way to go here?

    - by Krisc
    Working on the data access / model layer in this little MVC2 project and trying to think things out to future projects. I have a database with some basic tables and I have classes in the model layer that represent them. I obviously need something to connect the two. The easiest is to provide some sort of 'provider' that can run operations on the database and return objects. But this is for a website that would potentially be used "a lot" (I know, very general) so I want to cache results from the data layer and keep the cache updated as new data is generated. This question deals with how best to approach this problem of dual DALS. One that returns cached data when possible and goes to the data layer when there is a cache miss. But more importantly, how to integrate the core provider (thing that goes into database) with the caching layer so that it too can rely on cached objects rather than creating new ones. Right now I have the following interfaces: IDataProvider is used to reach the database. It doesn't concern itself with the meaning of the objects it produces, but simply the way to produce them. interface IDataProvider{ // Select, Update, Create, et cetera access IEnumerable<Entry> GetEntries(); Entry GetEntryById(int id); } IDataManager is a layer that sits on top of the IDataProvider layer and manages the cache interface IDataManager : IDataProvider{ void ClearCache(); } Note that in practice the IDataManager implementation will have useful helper functions to add objects to their related cache stores. (In the future I may define other functions on the interface) I guess what I am looking for is the best way to approach a loop back from the IDataProvider implementations so that they can access the cache. Or a different approach entirely may be in order? I am not very interested in 3rd party products at the moment as I am interested in the design of these things much more than this specific implementation. Edit: I realize the title may be a bit misleading. I apologize for that... not sure what to call this question.

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