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  • In ParallelPython, a method of an object ( object.func() ) fails to manipulate a variable of an object ( object.value )

    - by mehmet.ali.anil
    With parallelpython, I am trying to convert my old serial code to parallel, which heavily relies on objects that have methods that change that object's variables. A stripped example in which I omit the syntax in favor of simplicity: class Network: self.adjacency_matrix = [ ... ] self.state = [ ... ] self.equilibria = [ ... ] ... def populate_equilibria(self): # this function takes every possible value that self.state can be in # runs the boolean dynamical system # and writes an integer within self.equilibria for each self.state # doesn't return anything I call this method as: Code: j1 = jobserver.submit(net2.populate_equilibria,(),(),("numpy as num")) The job is sumbitted, and I know that a long computation takes place, so I speculate that my code is ran. The problem is, i am new to parallelpython , I was expecting that, when the method is called, the variable net2.equilibria would be written accordingly, and I would get a revised object (net2) . That is how my code works, independent objects with methods that act upon the object's variables. Rather, though the computation is apparent, and reasonably timed, the variable net2.equilibria remains unchanged. As if PP only takes the function and the object, computes it elsewhere, but never returns the object, so I am left with the old one. What do I miss? Thanks in advance.

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  • What is the exact problem with multiple inheritance?

    - by Totophil
    I can see people asking all the time whether multiple inheritance should be included into the next version of C# or Java and C++ folks, who are fortunate enough to have this ability, say that this is like giving someone a rope to eventually hang themselves. What’s the matter with the multiple inheritance? Are there any concrete samples?

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  • Can the Diamond Problem be really solved?

    - by Mecki
    A typical problem in OO programming is the diamond problem. I have parent class A with two sub-classes B and C. A has an abstract method, B and C implement it. Now I have a sub-class D, that inherits of B and C. The diamond problem is now, what implementation shall D use, the one of B or the one of C? People claim Java knows no diamond problem. I can only have multiple inheritance with interfaces and since they have no implementation, I have no diamond problem. Is this really true? I don't think so. See below: [removed vehicle example] Is a diamond problem always the cause of bad class design and something neither programmer nor compiler needs to solve, because it shouldn't exist in the first place? Update: Maybe my example was poorly chosen. See this image Of course you can make Person virtual in C++ and thus you will only have one instance of person in memory, but the real problem persists IMHO. How would you implement getDepartment() for GradTeachingFellow? Consider, he might be student in one department and teach in another one. So you can either return one department or the other one; there is no perfect solution to the problem and the fact that no implementation might be inherited (e.g. Student and Teacher could both be interfaces) doesn't seem to solve the problem to me.

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  • How can i call method from class but this method implemented from any interface?

    - by Phsika
    i try to call base.Alan(); in HacimBul. But base. dont give intellisense alan method public double HacimBul() { throw new Exception(); //return base..... -- how can i see base.Alan(); } namespace interfaceClass { class Program { static void Main(string[] args) { } } interface Ikenar { double kenar { get; set; } } interface Iyukseklik { double yuksekli {get; set;} } interface IAlan { double Alan(); } interface IHacim { double Hacim(); } class Alan : Ikenar, IAlan { public double kenar { get; set; } double IAlan.Alan() { return kenar * kenar; } } class Hacim : Alan, Iyukseklik { public double kenar { get; set; } public double yuksekli { get; set; } public double HacimBul() { throw new Exception(); //return base..... -- how can i see base.Alan(); } } }

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  • Socket server with multiple clients, sending messages to many clients without hurting liveliness

    - by Karl Johanson
    I have a small socket server, and I need to distribute various messages from client-to-client depending on different conditionals. However I think I have a small problem with livelyness in my current code, and is there anything wrong in my approach: public class CuClient extends Thread { Socket socket = null; ObjectOutputStream out; ObjectInputStream in; CuGroup group; public CuClient(Socket s, CuGroup g) { this.socket = s; this.group = g; out = new ObjectOutputStream(this.socket.getOutputStream()); out.flush(); in = new ObjectInputStream(this.socket.getInputStream()); } @Override public void run() { String cmd = ""; try { while (!cmd.equals("client shutdown")) { cmd = (String) in.readObject(); this.group.broadcastToGroup(this, cmd); } out.close(); in.close(); socket.close(); } catch (Exception e) { System.out.println(this.getName()); e.printStackTrace(); } } public void sendToClient(String msg) { try { this.out.writeObject(msg); this.out.flush(); } catch (IOException ex) { } } And my CuGroup: public class CuGroup { private Vector<CuClient> clients = new Vector<CuClient>(); public void addClient(CuClient c) { this.clients.add(c); } void broadcastToGroup(CuClient clientName, String cmd) { Iterator it = this.clients.iterator(); while (it.hasNext()) { CuClient cu = (CuClient)it.next(); cu.sendToClient(cmd); } } } And my main-class: public class SmallServer { public static final Vector<CuClient> clients = new Vector<CuClient>(10); public static boolean serverRunning = true; private ServerSocket serverSocket; private CuGroup group = new CuGroup(); public void body() { try { this.serverSocket = new ServerSocket(1337, 20); System.out.println("Waiting for clients\n"); do { Socket s = this.serverSocket.accept(); CuClient t = new CuClient(s,group); System.out.println("SERVER: " + s.getInetAddress() + " is connected!\n"); t.start(); } while (this.serverRunning); } catch (IOException ex) { ex.printStackTrace(); } } public static void main(String[] args) { System.out.println("Server"); SmallServer server = new SmallServer(); server.body(); } } Consider the example with many more groups, maybe a Collection of groups. If they all synchronize on a single Object, I don't think my server will be very fast. I there a pattern or something that can help my liveliness?

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  • Extending DOMDocument and DOMNode: problem with return object

    - by Glauber Rocha
    I'm trying to extend the DOMDocument class so as to make XPath selections easier. I wrote this piece of code: class myDOMDocument extends DOMDocument { function selectNodes($xpath){ $oxpath = new DOMXPath($this); return $oxpath->query($xpath); } function selectSingleNode($xpath){ return $this->selectNodes($xpath)->item(0); } } These methods return a DOMNodeList and a DOMNode object, respectively. What I'd like to do now is to implement similar methods to the DOMNode objects. But obviously if I write a class (myDOMNode) that extends DOMNode, I won't be able to use these two extra methods on the nodes returned by myDOMDocument because they're DOMNode (and not myDOMNode) objects. I'm rather a beginner in object programming, I've tried various ideas but they all lead to a dead-end. Any hints? Thanks a lot in advance.

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  • Keyword 'this'(Me) is not available calling the base constructor

    - by serhio
    In the inherited class I use the base constructor, but can't use class's members calling this base constructor. In this example I have a PicturedLabel that knows it's own color and has a image. A TypedLabel : PictureLabel knows it's type but uses the base color. The (base)image that uses TypedLabel should be colored with the (base)color, however, I can't obtain this color: Error: Keyword 'this' is not available in the current context A workaround? /// base class public class PicturedLabel : Label { PictureBox pb = new PictureBox(); public Color LabelColor; public PicturedLabel() { // initialised here in a specific way LabelColor = Color.Red; } public PicturedLabel(Image img) : base() { pb.Image = img; this.Controls.Add(pb); } } public enum LabelType { A, B } /// derived class public class TypedLabel : PicturedLabel { public TypedLabel(LabelType type) : base(GetImageFromType(type, this.LabelColor)) //Error: Keyword 'this' is not available in the current context { } public static Image GetImageFromType(LabelType type, Color c) { Image result = new Bitmap(10, 10); Rectangle rec = new Rectangle(0, 0, 10, 10); Pen pen = new Pen(c); Graphics g = Graphics.FromImage(result); switch (type) { case LabelType.A: g.DrawRectangle(pen, rec); break; case LabelType.B: g.DrawEllipse(pen, rec); break; } return result; } }

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  • class composition instead of object composition?

    - by fayer
    I want a class property to be reference to another class, not its object and then use this property to call the class's static methods. class Database { private static $log; public static function addLog($LogClass) { self::$log = $LogClass; } public static function log() { self::$log::write(); // seems not possible to write it like this } } any suggestions how i can accomplish this? cause i have no reason making them objects, i want to use the classes for it.

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  • PHP: Array of objects is empty when I come to retrieve one from the array

    - by Tom
    Good morning, I am trying to load rows from a database and then create objects from them and add these objects to a private array. Here are my classes: <?php include("databaseconnect.php"); class stationItem { private $code = ''; private $description = ''; public function setCode($code ){ $this->code = $code; } public function getCode(){ return $this->code; } public function setDescription($description){ $this->description = $description; } public function getDescription(){ return $this->description; } } class stationList { private $stationListing; function __construct() { connect(); $stationListing = array(); $result = mysql_query('SELECT * FROM stations'); while ($row = mysql_fetch_assoc($result)) { $station = new stationItem(); $station->setCode($row['code']); $station->setDescription($row['description']); array_push($stationListing, $station); } mysql_free_result($result); } public function getStation($index){ return $stationListing[$index]; } } ?> As you can see I am creating a stationItem object per database row (which for now has a code and description) and I then push these on to the end of my array which is held as a private variable in stationList. This is code which creates this classes and attempts to access the properties on them: $stations = new stationList(); $station = $stations->getStation(0); echo $station->getCode(); I am finding that the sizeof($stationList) at the end of the constructor is 1 but then it is zero when we come to try to get an object from the array using the index. Therefore the error that I get is: Fatal error: Call to a member function getCode() on a non-object Please can someone explain to me why this is happening? I guess I am misunderstanding how object references work in PHP5.

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  • How can i use complextype class or multi type class is it generic collection?

    - by programmerist
    i need a complex returning type. i have 4 class returning types COMPLEXTYPE must include Company, Muayene, Radyoloji, Satis because i must return data switch case situation how can i do? Maybe i need generic collections How can i do that? public class GenoTipController { public COMPLEXTYPE Generate(DataModelType modeltype) { _Company company = null; _Muayene muayene = null; _Radyoloji radyoloji = null; _Satis satis = null; switch (modeltype) { case DataModelType.Radyoloji: radyoloji = new Radyoloji(); return radyoloji; break; case DataModelType.Satis: satis = new Satis(); return satis; break; case DataModelType.Muayene: muayene = new Muayene(); return muayene; break; case DataModelType.Company: company = new Company(); return company; break; default: break; } } } public class CompanyView { public static List GetPersonel() { GenoTipController controller = new GenoTipController(); _Company company = controller.Generate(DataModelType.Company); return company.GetPersonel(); } } public enum DataModelType { Radyoloji, Satis, Muayene, Company }

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  • How to write Composition and Aggregation in java

    - by Mifas
    I want to know how to identify composition and aggregation code in java. I have C++ Code, But I don't understand how to write in java. Composition class A {}; class B { A composited_A; }; Aggregation via Pointer class A {}; class B { A* pointer_to_A; B(A anA){ pointer_to_A = &anA; } Can anyone please tell me how both are working in JAVA. (I know what is meant by Composition and aggregation ) };

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  • Personal project in Java

    - by Chuck
    My first project in java is going to be a program (eventually I have to create a GUI interface but for now CLI would do) to keep track of my books (something similar to what libraries have only a simpler). I need to be able to insert, update, remove, show all books, update, search(by name or author or date). For the design I was thinking one main class Library which will have all of the above as methods that connect to the db and retrieve the data. Is this approach ok? I realize it's simple but it's my first real project and I would appreciate a little feedback. Also, is it too soon to consider reading up on design patterns and database design ?

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  • use of assertions for type checking in php?

    - by user151841
    I do some checking of arguments in my classes in php using exception-throwing functions. I have functions that do a basic check ( ===, in_array etc ) and throw an exception on false. So I can do assertNumeric($argument, "\$argument is not numeric."); instead of if ( ! is_numeric($argument) ) { throw new Exception("\$argument is not numeric."); } Saves some typing I was reading in the comments of the php manual page on assert() that As noted on Wikipedia - "assertions are primarily a development tool, they are often disabled when a program is released to the public." and "Assertions should be used to document logically impossible situations and discover programming errors— if the 'impossible' occurs, then something fundamental is clearly wrong. This is distinct from error handling: most error conditions are possible, although some may be extremely unlikely to occur in practice. Using assertions as a general-purpose error handling mechanism is usually unwise: assertions do not allow for graceful recovery from errors, and an assertion failure will often halt the program's execution abruptly. Assertions also do not display a user-friendly error message." This means that the advice given by "gk at proliberty dot com" to force assertions to be enabled, even when they have been disabled manually, goes against best practices of only using them as a development tool So, am I 'doing it wrong'? What other/better ways of doing this are there?

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  • Create a Python User() class that both creates new users and modifies existing users

    - by ensnare
    I'm trying to figure out the best way to create a class that can modify and create new users all in one. This is what I'm thinking: class User(object): def __init__(self,user_id): if user_id == -1 self.new_user = True else: self.new_user = False #fetch all records from db about user_id self._populateUser() def commit(self): if self.new_user: #Do INSERTs else: #Do UPDATEs def delete(self): if self.new_user == False: return False #Delete user code here def _populate(self): #Query self.user_id from database and #set all instance variables, e.g. #self.name = row['name'] def getFullName(self): return self.name #Create a new user >>u = User() >>u.name = 'Jason Martinez' >>u.password = 'linebreak' >>u.commit() >>print u.getFullName() >>Jason Martinez #Update existing user >>u = User(43) >>u.name = 'New Name Here' >>u.commit() >>print u.getFullName() >>New Name Here Is this a logical and clean way to do this? Is there a better way? Thanks.

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  • DDD and MVC: Difference between 'Model' and 'Entity'

    - by Nathan Loding
    I'm seriously confused about the concept of the 'Model' in MVC. Most frameworks that exist today put the Model between the Controller and the database, and the Model almost acts like a database abstraction layer. The concept of 'Fat Model Skinny Controller' is lost as the Controller starts doing more and more logic. In DDD, there is also the concept of a Domain Entity, which has a unique identity to it. As I understand it, a user is a good example of an Entity (unique userid, for instance). The Entity has a life-cycle -- it's values can change throughout the course of the action -- and then it's saved or discarded. The Entity I describe above is what I thought Model was supposed to be in MVC? How off-base am I? To clutter things more, you throw in other patterns, such as the Repository pattern (maybe putting a Service in there). It's pretty clear how the Repository would interact with an Entity -- how does it with a Model? Controllers can have multiple Models, which makes it seem like a Model is less a "database table" than it is a unique Entity. So, in very rough terms, which is better? No "Model" really ... class MyController { public function index() { $repo = new PostRepository(); $posts = $repo->findAllByDateRange('within 30 days'); foreach($posts as $post) { echo $post->Author; } } } Or this, which has a Model as the DAO? class MyController { public function index() { $model = new PostModel(); // maybe this returns a PostRepository? $posts = $model->findAllByDateRange('within 30 days'); while($posts->getNext()) { echo $posts->Post->Author; } } } Both those examples didn't even do what I was describing above. I'm clearly lost. Any input?

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  • Polymorphic call

    - by harigm
    I am new to java, I have seen in the code at many places where my seniors have declared as List myList = new ArrayList(); (option1) Instead of ArrayList myList = new ArrayList(); (option2) Can you please tell me why people use Option1, is there any advantages? If we use option2, do we miss out any advantages or features?

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  • How to handle the pylint message: Warning: Method could be a function

    - by biffabacon
    Being new to Python, I decided to get some feedback on a class I'd written ASAP so I ran it against pylint. Is the message it gave "Warning: Method could be a function" telling me that it would be better to move this method out of the class because it doesn't use any instance variables? In c# I would make this a static method. What's the most pythonic thing to do here?

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  • PHP: How to cast object to inherited class?

    - by andreyvlru
    I'd like to inherit PDOStatement class and use it in my website scripts. But I am frustrated how to get required object. PDO::query returns only direct PDOStatement object and looks like there are no other method to create PDOStatement object or inherited class. Initially i thought to move PDOStatement object to constructor of inherit class Something like that: $stmt = PDO -> query("select * from messages"); $messageCollection = new Messaging_Collection($stmt); But how to make instance of PDOStatement to inherited object (Messaging_Collection). It is a big question for me. class Messaging_Collection extends PDOStatement { public function __construct(PDOStatement $stmt) { //there i should to transform $stmt to $this // direct $this = $stmt is not possible // is there other right way? }

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  • MVC pattern and State Machine

    - by topright
    I think of a game as a state machine. Game States separate I/O processing, game logic and rendering into different classes: while (game_loop) { game->state->io_events(this); game->state->logic(this); game->state->rendering(); } You can easily change a game state in this approach. MVC separation works in more complex way: while (game_loop) { game->cotroller->io_events(this); game->model->logic(this); game->view->rendering(); } So changing Game States becomes error prone task (switch 3 MVC objects, not 1). What are practical ways of combining these 2 concepts?

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  • Magento - Show Custom Attributes in Grouped Product table.

    - by greencoconut
    I need to find a way to show the value of a custom attribute in place of the "Product Name" shown in the image below. I'm working with /app/design/frontend/default/defaultx/template/catalog/product/view/type/grouped.php The code below doesn't work(the custom attribute is yearmade): <?php if (count($_associatedProducts)): ?> <?php foreach ($_associatedProducts as $_item): ?> <tr> <td><?php echo $this->htmlEscape($_item->getYearmade()) ?></td> Any help would be appreciated. EDIT: So the answer turned out to be quite simple. You see what I failed to mention above was that there was indeed output... but that it was just a number (eg: 52). Turns out this was the ID for that custom attribute value (It was a Dropdown type of custom attribute). So in summary This works for custom attributes of type text: echo $this->htmlEscape($_item->getYearmade()) But for all other types of custom attribute (I think), the following should be used: echo $this->htmlEscape($_item->getAttributeText('yearmade')) I would not have discovered this without the most excellent answer provided by Alan Storm, below. Thank you sir.

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  • Generics and Constrained Polymorphism versus Subtyping

    - by Rahul G
    Hullo all. In this (Warning: PDF) presentation on Haskell Type Classes, on slide #54, there's this question: Open Question: In a language with generics and constrained polymorphism, do you need subtyping too? My questions are: How do generics and constrained polymorphism make subtyping unnecessary? If generics and constrained polymorphism make subtyping unnecessary, why does Scala have subtyping?

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