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• Equivalence Classes LISP

  - by orcik

  I need to write a program for equivalence classes and get this outputs... (equiv '((a b) (a c) (d e) (e f) (c g) (g h))) => ((a b c g h) (d e f)) (equiv '((a b) (c d) (e f) (f g) (a e))) => ((a b e f g) (c d)) Basically, A set is a list in which the order doesn't matter, but elements don't appear more than once. The function should accept a list of pairs (elements which are related according to some equivalence relation), and return a set of equivalence classes without using iteration or assignment statements (e.g. do, set!, etc.). However, set utilities such as set-intersection, set-union and a function which eliminates duplicates in a list and built-in functions union, intersection, and remove-duplicates are allowed. Thanks a lot!

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• Equivalence Classes

  - by orcik

  I need to write a program for equivalence classes and get this outputs... (equiv '((a b) (a c) (d e) (e f) (c g) (g h))) => ((a b c g h) (d e f)) (equiv '((a b) (c d) (e f) (f g) (a e))) => ((a b e f g) (c d)) Basically, A set is a list in which the order doesn't matter, but elements don't appear more than once. The function should accept a list of pairs (elements which are related according to some equivalence relation), and return a set of equivalence classes without using iteration or assignment statements (e.g. do, set!, etc.). However, set utilities such as set-intersection, set-union and a function which eliminates duplicates in a list and built-in functions union, intersection, and remove-duplicates are allowed. Thanks a lot! By the way, It's not a homework question. A friend of mine need this piece of code to solve smilar questions.

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• Using design-patterns to transform web-service model classes into local model classes and vise versa

  - by Daniil Petrov

  There is a web-application built with play framework 1.2.7. It contains less than 10 model classes. The main purpose of the application is a lightweight access to a complex remote application (more than 50 model classes). The remote application has its own SOAP API and we use it for synchronization of data. There is a scheduled job in the web-app which makes requests to the remote app. It gets bunches of objects from the remote model and populates corresponding objects of the local model. Currently, there are two groups of classes - the local model and the remote model (generated from wsdl schema). It is not allowed to make any modifications to the remote model. Transformations are being made in the scheduled job class. When it gets objects from the remote app it creates local objects. Recently, it was decided to add a possibility to modify the remote objects. It requires more transformations on our side. We need to transform from remote to local model when reading objects and from local to remote when changing objects. I wonder if this would be possible to use some design-patterns to reduce a number of transformations?

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• Why use link classes in oql instead of classes that contain links

  - by Isaac

  itop abstracts its very complex database design with an object query language (oql). For this there are classes definded, like 'Ticket' and 'Server'. Now a Ticket usually is linked to a Server. In my naive way I would give the Ticket class an attribute 'affected_server_list', where I could reference the affected servers. itop does it different: neither Servers nor Tickets know of each other. Instead there is a class 'linkTicketToServer', which provides the link between the two. The first thing I noticed is that it makes oql queries more complex. So I wondered why they designed it this way. One thing that occured to me is that it allows for more flexiblity, in that I can add links without modifying the original classes. Is this allready why one would implement it this way, or are there other reasons for this kind of design?

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• call function between classes [closed]

  - by aziz joh

  hello I have 3 classes class A, B, and C class A is the main class and content the main function also, i call class B and class C in the main as b1,b2 and c1. in class B there is a vector (V) has list of int. and 3 functions Add, get and delete delete. all the thing in the class is public. in class C i have function that need to (B::get) from b. what I want is that how I can make c1 call get of b1 to return the value of the V in b1 after that use add of b2 to add new item in V of b2. Thanks in advance This is an example class a{ int main(){ b b1,b2; c c1; b1.add(10); b1.add(20); c1.start(); }} class b{ vector<int> v; void add(int i){ v.push_back(i)} int get(){int i=v.at(0); return i;} } class c{// take something from b1 and add it to b2 void play(){ int i=b.get();//should take it from b1 b.add(i*2);//should add it to b2 }} please I need your help I been searching to solve this problem for days.

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• The SQL of Membership: Equivalence Classes & Cliques

  It is awkward to do 'Graph databases' in SQL to explore the sort of relationships and memberships in social networks because equivalence relations are classes (a set of sets) rather than sets. However one can explore graphs in SQL if the relationship has all three of the mathematical properties needed for an equivalence relationship. FREE eBook – "45 Database Performance Tips for Developers"Improve your database performance with 45 tips from SQL Server MVPs and industry experts. Get the eBook here.

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• Python many-to-one mapping (creating equivalence classes)

  - by Adam Matan

  Hi, I have a project of converting one database to another. One of the original database columns defines the row's category. This coulmn should be mapepd to a new category in the new databse. For example, let's assume the original categories are:parrot, spam, cheese_shop, Cleese, Gilliam, Palin Now that's a little verbose for me, And I want to have these rows categorized as sketch, actor - That is, define all the sketches and all the actors as two equivalence classes. >>> monty={'parrot':'sketch', 'spam':'sketch', 'cheese_shop':'sketch', 'Cleese':'actor', 'Gilliam':'actor', 'Palin':'actor'} >>> monty {'Gilliam': 'actor', 'Cleese': 'actor', 'parrot': 'sketch', 'spam': 'sketch', 'Palin': 'actor', 'cheese_shop': 'sketch'} That's quite awkward- I would prefer having something like: monty={ ('parrot','spam','cheese_shop'): 'sketch', ('Cleese', 'Gilliam', 'Palin') : 'actors'} But this, of course, sets the entire tuple as a key: >>> monty['parrot'] Traceback (most recent call last): File "<pyshell#29>", line 1, in <module> monty['parrot'] KeyError: 'parrot' Any ideas how to create an elegant many-to-one dictionary in Python? Thanks, Adam

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• obj-c classes and sub classes (Cocos2d) conversion

  - by Lewis

  Hi I'm using this version of cocos2d: https://github.com/krzysztofzablocki/CCNode-SFGestureRecognizers Which supports the UIGestureRecognizer within a CCLayer in a cocos2d scene like so: @interface HelloWorldLayer : CCLayer <UIGestureRecognizerDelegate> { } Now I want to make this custom gesture work within the scene, attaching it to a sprite in cocos2d: #import <Foundation/Foundation.h> #import <UIKit/UIGestureRecognizerSubclass.h> @protocol OneFingerRotationGestureRecognizerDelegate <NSObject> @optional - (void) rotation: (CGFloat) angle; - (void) finalAngle: (CGFloat) angle; @end @interface OneFingerRotationGestureRecognizer : UIGestureRecognizer { CGPoint midPoint; CGFloat innerRadius; CGFloat outerRadius; CGFloat cumulatedAngle; id <OneFingerRotationGestureRecognizerDelegate> target; } - (id) initWithMidPoint: (CGPoint) midPoint innerRadius: (CGFloat) innerRadius outerRadius: (CGFloat) outerRadius target: (id) target; - (void)reset; - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event; - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event; - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event; - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event; @end #include <math.h> #import "OneFingerRotationGestureRecognizer.h" @implementation OneFingerRotationGestureRecognizer // private helper functions CGFloat distanceBetweenPoints(CGPoint point1, CGPoint point2); CGFloat angleBetweenLinesInDegrees(CGPoint beginLineA, CGPoint endLineA, CGPoint beginLineB, CGPoint endLineB); - (id) initWithMidPoint: (CGPoint) _midPoint innerRadius: (CGFloat) _innerRadius outerRadius: (CGFloat) _outerRadius target: (id <OneFingerRotationGestureRecognizerDelegate>) _target { if ((self = [super initWithTarget: _target action: nil])) { midPoint = _midPoint; innerRadius = _innerRadius; outerRadius = _outerRadius; target = _target; } return self; } /** Calculates the distance between point1 and point 2. */ CGFloat distanceBetweenPoints(CGPoint point1, CGPoint point2) { CGFloat dx = point1.x - point2.x; CGFloat dy = point1.y - point2.y; return sqrt(dx*dx + dy*dy); } CGFloat angleBetweenLinesInDegrees(CGPoint beginLineA, CGPoint endLineA, CGPoint beginLineB, CGPoint endLineB) { CGFloat a = endLineA.x - beginLineA.x; CGFloat b = endLineA.y - beginLineA.y; CGFloat c = endLineB.x - beginLineB.x; CGFloat d = endLineB.y - beginLineB.y; CGFloat atanA = atan2(a, b); CGFloat atanB = atan2(c, d); // convert radiants to degrees return (atanA - atanB) * 180 / M_PI; } #pragma mark - UIGestureRecognizer implementation - (void)reset { [super reset]; cumulatedAngle = 0; } - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { [super touchesBegan:touches withEvent:event]; if ([touches count] != 1) { self.state = UIGestureRecognizerStateFailed; return; } } - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { [super touchesMoved:touches withEvent:event]; if (self.state == UIGestureRecognizerStateFailed) return; CGPoint nowPoint = [[touches anyObject] locationInView: self.view]; CGPoint prevPoint = [[touches anyObject] previousLocationInView: self.view]; // make sure the new point is within the area CGFloat distance = distanceBetweenPoints(midPoint, nowPoint); if ( innerRadius <= distance && distance <= outerRadius) { // calculate rotation angle between two points CGFloat angle = angleBetweenLinesInDegrees(midPoint, prevPoint, midPoint, nowPoint); // fix value, if the 12 o'clock position is between prevPoint and nowPoint if (angle > 180) { angle -= 360; } else if (angle < -180) { angle += 360; } // sum up single steps cumulatedAngle += angle; // call delegate if ([target respondsToSelector: @selector(rotation:)]) { [target rotation:angle]; } } else { // finger moved outside the area self.state = UIGestureRecognizerStateFailed; } } - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { [super touchesEnded:touches withEvent:event]; if (self.state == UIGestureRecognizerStatePossible) { self.state = UIGestureRecognizerStateRecognized; if ([target respondsToSelector: @selector(finalAngle:)]) { [target finalAngle:cumulatedAngle]; } } else { self.state = UIGestureRecognizerStateFailed; } cumulatedAngle = 0; } - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event { [super touchesCancelled:touches withEvent:event]; self.state = UIGestureRecognizerStateFailed; cumulatedAngle = 0; } @end Header file for view controller: #import "OneFingerRotationGestureRecognizer.h" @interface OneFingerRotationGestureViewController : UIViewController <OneFingerRotationGestureRecognizerDelegate> @property (nonatomic, strong) IBOutlet UIImageView *image; @property (nonatomic, strong) IBOutlet UITextField *textDisplay; @end then this is in the .m file: gestureRecognizer = [[OneFingerRotationGestureRecognizer alloc] initWithMidPoint: midPoint innerRadius: outRadius / 3 outerRadius: outRadius target: self]; [self.view addGestureRecognizer: gestureRecognizer]; Now my question is, is it possible to add this custom gesture into the cocos2d project found on that github, and if so, what do I need to change in the OneFingerRotationGestureRecognizerDelegate to get it to work within cocos2d. Because at the minute it is setup in a standard iOS project and not a cocos2d project and I do not know enough about UIViews and classing/ sub classing in obj-c to get this to work. Also it seems to inherit from a UIView where cocos2d uses CCLayer. Kind regards, Lewis. I also realise I may have not included enough code from the custom gesture project for readers to interpret it fully, so the full project can be found here: https://github.com/melle/OneFingerRotationGestureDemo

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• Resolving equivalence relations

  - by Luca Cerone

  I am writing a function to label the connected component in an image (I know there are several libraries outside, I just wanted to play with the algorithm). To do this I label the connected regions with different labels and create an equivalence table that contain information on the labels belonging to the same connected component. As an example if my equivalence table (vector of vector) looks something like: 1: 1,3 2: 2,3 3: 1,2,3 4: 4 It means that in the image there are 2 different regions, one made of elements that are labelled 1,2,3 and an other made of elements labelled 4. What is an easy and efficient way to resolve the equivalences and end up with something that looks like: 1: 1,2,3 2: 4 that I can use to "merge" the different connected regions belonging to the same connected component? Thanks a lot for the help!

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• C#: Oracle Data Type Equivalence with OracleDbType

  - by Partial

  Situation: I am creating an app in C# that uses Oracle.DataAccess.Client (11g) to do certain operations on a Oracle database with stored procedures. I am aware that there is a certain enum (OracleDbType) that contains the Oracle data types, but I am not sure which one to use for certain types. Questions: What is the equivalent Oracle PL/SQL data type for each enumerated type in the OracleDbType enumeration? There are three types of integer (Int16, Int32, Int64) in the OracleDbType... how to know which one to use or are they all suppose to work?

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• Does Sandcastle support Entity Framework Partial Classes?

  - by ChrisHDog

  I am attempting to use Sandcastle (and Sandcastle Help File Builder) to do some "auto-documentation" of some classes I am using. The classes that are giving me trouble are some partial classes on Entity Framework items that add methods and properties to those Framework items. The triple slash comments don't appear to come through on the methods and properties created in the partial classes. I have out how to get xml documentation of the base properties using the short summary and long description fields on the .emdx editor, but that doesn't provide a solution for the items in the partial classes. Is this possible? Is it perhaps just settings that I'm not setting correctly to pick up the partial classes? Does Sandcastle do partial classes in non-Entity Framework settings? Is what I'm doing even possible (has anyone else successfully used the xml created from triple slash comments to create documentation on entity framework partial classes, and if so how did you do that)? Any assistance is appreciated

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• Equivalence of PHP includes in Iphone dev ?

  - by gotye

  Hey guys, I just noticed I get a lot of redondant code from one class to another in my project (like menus or buttons) ;) Is there any way to optimize it ? Thank you ! Gotye.

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• Achieving decoupling in Model classes

  - by Guven

  I am trying to test-drive (or at least write unit tests) my Model classes but I noticed that my classes end up being too coupled. Since I can't break this coupling, writing unit tests is becoming harder and harder. To be more specific: Model Classes: These are the classes that hold the data in my application. They resemble pretty much the POJO (plain old Java objects), but they also have some methods. The application is not too big so I have around 15 model classes. Coupling: Just to give an example, think of a simple case of Order Header - Order Item. The header knows the item and the item knows the header (needs some information from the header for performing certain operations). Then, let's say there is the relationship between Order Item - Item Report. The item report needs the item as well. At this point, imagine writing tests for Item Report; you need have a Order Header to carry out the tests. This is a simple case with 3 classes; things get more complicated with more classes. I can come up with decoupled classes when I design algorithms, persistence layers, UI interactions, etc... but with model classes, I can't think of a way to separate them. They currently sit as one big chunk of classes that depend on each other. Here are some workarounds that I can think of: Data Generators: I have a package that generates sample data for my model classes. For example, the OrderHeaderGenerator class creates OrderHeaders with some basic data in it. I use the OrderHeaderGenerator from my ItemReport unit-tests so that I get an instance to OrderHeader class. The problem is these generators get complicated pretty fast and then I also need to test these generators; defeating the purpose a little bit. Interfaces instead of dependencies: I can come up with interfaces to get rid of the hard dependencies. For example, the OrderItem class would depend on the IOrderHeader interface. So, in my unit tests, I can easily mock the behaviour of an OrderHeader with a FakeOrderHeader class that implements the IOrderHeader interface. The problem with this approach is the complexity that the Model classes would end up having. Would you have other ideas on how to break this coupling in the model classes? Or, how to make it easier to unit-test the model classes?

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• How do I start correctly in building database classes in c#?

  - by e4rthdog

  I am new in C# programming and in OOP. I need to dive into web applications for my company, and I need to do it fast and correct. So even that I know ASP.NET MVC is the way to go, I want to start with some simple applications with ASP.NET Webforms and then advance to MVC logic. Also regarding my db classes: I plan to create common database classes in order to be able to use them either from WinForms or ASP.NET applications. I also know that the way to go is to learn about ORM and EF. BUT I also want to start from where I am feeling comfortable and that is the traditional ADO.NET way. So about my Data Access Layer classes: Should I return my results in datasets or arraylists/lists? Should my methods do their own connect/disconnect from the db, or have separate methods and let the application maintain the connection?

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• Nested Classes: A useful tool or an encapsulation violation?

  - by Bryan Harrington

  So I'm still on the fence as to whether or not I should be using these or not. I feel its an extreme violation of encapsulation, however I find that I am able to achieve some degree of encapsulation while gaining more flexibility in my code. Previous Java/Swing projects I had used nested classes to some degree, However now I have moved into other projects in C# and I am avoid their use. How do you feel about nested classes?

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• Do any languages other than haskell/agda have a hindley-milner type system and type classes?

  - by Jimmy Hoffa

  In pondering what gives Haskell such a layer of mental pain in becoming proficient the main thing I can think of are the Monads, Applicatives, Functors, and gaining an intuition to know how a list or maybe will behave in regards to sequence or alternate or bind etc. But why haven't other languages presented these same concepts given the usefulness of monads/applicatives/etc? It occurs to me, type classes are the key, so the question is: Have any languages other than Haskell/Agda actually implemented type classes in the same or similar way?

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• How to use lists in equivalence partitioning?

  - by KhDonen

  I have read that equivalence partitioning can be used typically for intervals or lists, e.g. I assume it can be used for every set of inputs. Anyway if the requirement says that allowed colors are (RED,BLUE,BLACK, GREEN), I cannot treat them like a list, right? I mean, testing one of them would not be enough because developers most likely used some switch-case and thus it is not real "set" where one could represent also the others. So how it is meant with lists? Also what is not that clear to me, I do not think it is always possible to do the initial partioning and then design the test cases. What about checking two lines intersection: Y=MX+C. (two inputs) 1) The lines are paraller. M1=M1 but C1 must be different from C2. 2) Lines are intersecting. M1 must be different from M2. 3) Coincident. The are the same. How can I use partitioning here? THis is actually taken from a book and it says that these sets are eq.classes.

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• Testing C++ program with Testing classes over normally used classes

  - by paultop6

  Hi Guys, This will probably be a bot of a waffly question but ill try my best. I have a simple c++ program that i need to build testing for. I have 2 Classes i use besides the one i actually am using, these are called WebServer and BusinessLogicLayer. To test my own code i have made my own versions of these classes that feed dummy data to my class to test it functionality. I need to know a way of somehow, via a makefile for instance, how to tell the source code to use the test classes over the normally used classes. The test classes are in a different "tester" c++ file, and the tester c++ file also has its own header file. Regards Paul P.S. This is probably a badly worded question, but i dont know any better way to put my question.

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• Extending mysqli and using multiple classes

  - by Mikk

  Hi, I'm new to PHP oop stuff. I'm trying to create class database and call other classes from it. Am I doing it the right way? class database: class database extends mysqli { private $classes = array(); public function __construct() { parent::__construct('localhost', 'root', 'password', 'database'); if (mysqli_connect_error()) { $this->error(mysqli_connect_errno(), mysqli_connect_error()); } } public function __call($class, $args) { if (!isset($this->classes[$class])) { $class = 'db_'.$class; $this->classes[$class] = new $class(); } return $this->classes[$class]; } private function error($eNo, $eMsg) { die ('MySQL error: ('.$eNo.': '.$eMsg); } } class db_users: class db_users extends database { public function test() { echo 'foo'; } } and how I'm using it $db = new database(); $db->users()->test(); Is it the right way or should it be done another way? Thank you.

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• Type classes or implicit parameters? What do you prefer and why? [closed]

  - by Petr Pudlák

  I was playing a bit with Scalaz and I realized that Haskell's type classes are very similar to Scala's implicit parameters. While Haskell passes the methods defined by a type class using hidden dictionaries, Scala allows a similar thing using implicit parameters. For example, in Haskell, one could write: incInside :: (Functor f) => f Int -> f Int incInside = fmap (+ 1) and the same function using Scalaz: import scalaz._; import Scalaz._; def incInside[F[_]](x: F[Int])(implicit fn: Functor[F]): F[Int] = fn.fmap(x, (_:Int) + 1); I wonder: If you could choose (i.e. your favorite language would offer both), what would you pick - implicits or type classes? And what are your pros/cons?

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• Using CSS Classes for individual effects - opinions?

  - by Cool Hand Luke UK

  Hey, Just trying to canvas some opinions here. I was wondering how people go about adding individual effects to html elements. Take this example: you have three types of h1 titles all the same size but some are black some are gold and some are white. Some have a text-shadow etc. Would you create separate CSS classes and add them do the h1 tag or would you create a new single class for each different h1 title type (with grouped CSS elements)? With singular class for each effect you can build up combos of classes in html class="gold shadow" but also how would you name them. For example its bad practice to give classes and id names associated to colours, because it doesn't define what it does well. However is this ok with textual CSS classes? Just wondering what others do, I know there are no hard and fast rules. Cheers.

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• Using CSS Classes for indivdual effects - opinions?

  - by Cool Hand Luke UK

  Hey, Just trying to canvas some opinions here. I was wondering how people go about adding individual effects to html elements. Take this example: you have three types of h1 titles all the same size but some are black some are gold and some are white. Some have a text-shadow etc. Would you create separate CSS classes and add them do the h1 tag or would you create a new single class for each different h1 title type (with grouped CSS elements)? With singular class for each effect you can build up combos of classes in html class="gold shadow" but also how would you name them. For example its bad practice to give classes and id names associated to colours, because it doesn't define what it does well. However is this ok with textual CSS classes? Just wondering what others do, I know there are no hard and fast rules. Cheers.

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• C# Sharp: Partial Classes

  - by dcolumbus

  This is quick confirmation question: In order to make partial classes work, I initially thought that there would be a main Class public class ManageDates and then you would create partial classes like public partial class ManageDates to extend the ManageDates class. But from some experiementing, I've come to find out that if you're going to use partial classes, each individual class must be declared public partial class [ClassName] ... Am I correct in this conclusion?

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• What are all the types of classes?

  - by Tom Brito

  I mean, there are Utility classes, Entity classes, GUI/View classes, what more? Is there a list?

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• Does C# support inner classes? [closed]

  - by Amy

  Possible Duplicates: Using Inner classes in C# Inner classes in C# Class declared inside of another class in C# Does C# support the concept of inner classes? If so, what are the benefits? Could someone please explain this to me?

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