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  • Expression Tree with Property Inheritance causes an argument exception

    - by Adam Driscoll
    Following this post: link text I'm trying to create an expression tree that references the property of a property. My code looks like this: public interface IFoo { void X {get;set;} } public interface IBar : IFoo { void Y {get;set;} } public interface IFooBarContainer { IBar Bar {get;set;} } public class Filterer { //Where T = "IFooBarContainer" public IQueryable<T> Filter<T>(IEnumerable<T> collection) { var argument = Expression.Parameter(typeof (T), "item"); //... //where propertyName = "IBar.X"; PropertyOfProperty(argument, propertyName); } private static MemberExpression PropertyOfProperty(Expression expr, string propertyName) { return propertyName.Split('.').Aggregate<string, MemberExpression>(null, (current, property) => Expression.Property(current ?? expr, property)); } } I receive the exception: System.ArgumentException: Instance property 'X' is not defined for type 'IBar' ReSharper turned the code in the link above into the condensed statement in my example. Both forms of the method returned the same error. If I reference IBar.Y the method does not fail.

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  • Inheritance: when implementing an interface which define a base class property why cant the class im

    - by Deepak
    Lets create some interfaces public interface ITimeEventHandler { string Open(); } public interface IJobTimeEventHandler: ITimeEventHandler { string DeleteJob(); } public interface IActivityTimeEventHandler: ITimeEventHandler { string DeleteActivity(); } public interface ITimeEvent { ITimeEventHandler Handler; } Another Interface public interface IJobTimeEvent :ITimeEvent { int JobID; } Create a class public class JobTimeEvent : IJobTimeEvent { public int JobID = 0; public IJobTimeEventHandler Handler = null; } My question is .. when implementing an interface which define a base class property why cant the class implementing interface return a derived class type object ?? For ex in class JobTimeEvent, IJobtimeEvent needs a property of type ITimeEventHandler but why IJobTimeEventHandler type is not allowed which derived from ITimeEventHandler

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  • pointer-to-pointer of derived class in multiple inheritance

    - by Abdul jalil
    i have 3 classes A,B and C. C is derived from A and B. i get pointer to pointer of class C and cast to A** , and B ** , the variable that hold the the B** has the address of A** in my example B ** BdoublePtr hold the address of A** .i am using the following code #include "conio.h" #include "stdio.h" #include "string.h" class A{ public: A() { strA=new char[30]; strcpy(strA,"class A"); } char *strA; }; class B { public: B() { strB=new char[30]; strcpy(strB,"class B"); } char *strB; }; class C :public A, public B { public: C() { strC=new char[30]; strcpy(strC,"class C"); } char *strC; }; int main(void) { C* ptrC=new C(); A * Aptr=(A*)ptrC; printf("\n class A value : %s",Aptr-strA); B * Bptr=(B*)ptrC; printf("\n class B value :%s",Bptr-strB); printf("\n\nnow with double pointer "); A ** AdoublePtr=(A **)&ptrC; Aptr=AdoublePtr; printf("\n class A value : %s",Aptr-strA); B * BdoublePtr=(B **)&ptrC; Bptr=*BdoublePtr; printf("\n class B value : %s",Bptr-strB); getch(); return 0; }

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  • Inheritance issue with ivar on the iPhone

    - by Buffalo
    I am using the BLIP/MYNetwork library to establish a basic tcp socket connection between the iPhone and my computer. So far, the code builds and runs correctly in simulator but deploying to device yields the following error: error: property 'delegate' attempting to use ivar '_delegate' declared in super class of 'TCPConnection' @interface TCPConnection : TCPEndpoint { @private TCPListener *_server; IPAddress *_address; BOOL _isIncoming, _checkedPeerCert; TCPConnectionStatus _status; TCPReader *_reader; TCPWriter *_writer; NSError *_error; NSTimeInterval _openTimeout; } /** The delegate object that will be called when the connection opens, closes or receives messages. */ @property (assign) id<TCPConnectionDelegate> delegate; /** The delegate messages sent by TCPConnection. All methods are optional. */ @protocol TCPConnectionDelegate <NSObject> @optional /** Called after the connection successfully opens. */ - (void) connectionDidOpen: (TCPConnection*)connection; /** Called after the connection fails to open due to an error. */ - (void) connection: (TCPConnection*)connection failedToOpen: (NSError*)error; /** Called when the identity of the peer is known, if using an SSL connection and the SSL settings say to check the peer's certificate. This happens, if at all, after the -connectionDidOpen: call. */ - (BOOL) connection: (TCPConnection*)connection authorizeSSLPeer: (SecCertificateRef)peerCert; /** Called after the connection closes. You can check the connection's error property to see if it was normal or abnormal. */ - (void) connectionDidClose: (TCPConnection*)connection; @end @interface TCPEndpoint : NSObject { NSMutableDictionary *_sslProperties; id _delegate; } - (void) tellDelegate: (SEL)selector withObject: (id)param; @end Does anyone know how I would fix this? Would I simply declare _delegate as a public property of the base class "TCPEndPoint"? Thanks for the help ya'll!

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  • Public property List needs to Concat 2 types with inheritance

    - by Bernard
    I have 2 lists: one of type A and one of type Aa. type Aa is inherited from type A. So: List<A> listA = new List<A>(); List<Aa> listAa = new List<Aa>(); with class Aa : A I have: public property Lists<A> { get { List<A> newList = new List<A>(); //return concat of both lists foreach(List l in listA) { newList.Add(l); } foreach(List l in listAa) { newList.Add(l); } } Can I somehow use Concat instead of the foreach loop? i.e. get { return listA.Concat(listAa); } // this doesn't work And secondly, how do I do the set part of the property? set { //figure out the type of variable value and put into appropriate list? }

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  • drawing to a JPanel without inheritance

    - by g.rocket
    Right now I'm working on a program that throws up a bunch of separate (generated at runtime) images, each in their own window. To do this i've tried this approach: public void display(){ JFrame window = new JFrame("NetPart"); JPanel canvas = new JPanel(); window.getContentPane().add(canvas); Graphics g = canvas.getGraphics(); Dimension d = getSize(); System.out.println(d); draw(g,new Point(d.minX*50,d.maxY*50), 50); window.setSize(d.size(50)); window.setResizable(false); window.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE); window.setVisible(true); } public void draw(Graphics g, Point startLoc, int scale){ // generate and draw the image } public Dimension getSize(){ //returns my own dimensions class } However, this throws a NullPointerException in draw, claiming that the graphics is null. is there any way to externally draw to a JPanel from outside it (not inherit from JPanel and override PaintComponent)? Any help would be appreciated.

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  • actionscript-3: refactor interface inheritance to get rid of ambiguous reference error

    - by maxmc
    hi! imagine there are two interfaces arranged via composite pattern, one of them has a dispose method among other methods: interface IComponent extends ILeaf { ... function dispose() : void; } interface ILeaf { ... } some implementations have some more things in common (say an id) so there are two more interfaces: interface ICommonLeaf extends ILeaf { function get id() : String; } interface ICommonComponent extends ICommonLeaf, IComponent { } so far so good. but there is another interface which also has a dispose method: interface ISomething { ... function dispose() : void; } and ISomething is inherited by ICommonLeaf: interface ICommonLeaf extends ILeaf, ISomething { function get id() : String; } As soon as the dispose method is invoked on an instance which implements the ICommonComponent interface, the compiler fails with an ambiguous reference error because ISomething has a method called dispose and ILeaf also has a dispose method, both living in different interfaces (IComponent, ISomething) within the inheritace tree of ICommonComponent. I wonder how to deal with the situation if the IComponent, the ILeaf and the ISomething can't change. the composite structure must also work for for the ICommonLeaf & ICommonComponent implementations and the ICommonLeaf & ICommonComponent must conform to the ISomething type. this might be an actionscript-3 specific issue. i haven't tested how other languages (for instance java) handle stuff like this.

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  • Ruby class instance variables and inheritance

    - by rlandster
    I have a Ruby class called LibraryItem. I want to associate with every instance of this class an array of attributes. This array is long and looks something like ['title', 'authors', 'location', ...] Note that these attributes are not really supposed to be methods, just a list of attributes that a LibraryItem has. Next, I want to make a subclass of LibraryItem called LibraryBook that has an array of attributes that includes all the attributes of LibraryItem but will also include many more. Eventually I will want several subclasses of LibraryItem each with their own version of the array @attributes but each adding on to LibraryItem's @attributes (e.g., LibraryBook, LibraryDVD, LibraryMap, etc.). So, here is my attempt: class LibraryItem < Object class << self; attr_accessor :attributes; end @attributes = ['title', 'authors', 'location',] end class LibraryBook < LibraryItem @attributes.push('ISBN', 'pages'] end This does not work. I get the error undefined method `push' for nil:NilClass

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  • abstract method signature, inheritance, and "Do" naming convention

    - by T. Webster
    I'm learning about design patterns and in examples of code I've seen a convention where the abstract class declares a method, for example: public abstract class ServiceBase { ... public virtual object GetSomething(); and then protected abstract object DoGetSomething(); My question is on why these two methods exist, since they appear to serve the same purpose. Is this so that the base class GetSomething() method logic cannot be overridden by inherited classes? But then again, the method is marked virtual, so it can be overridden anyway. What is the usefulness here in requiring derived class implementers to implement the abstract method when the virtual method can be called anyway?

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  • cake php AppController and inheritance

    - by RSK
    hello folks........ In many tutorial of Acl component in cakephp i got instruction that add component either in AppController or in all the other controllers which inherits AppController....... but problem is var $components=array('Auth',Acl); when i use the above line in AppConroller i cant use the Auth or Acl component... but when i use the same code in all the child classes it works fine........ what will be the problem thanks in advance any help will be appreciated.

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  • Inheritance domain classes in Grails

    - by Tomáš
    Hi gurus how can I get Collection of specific Class? I use inheriance: On Planet live Human. Humans are dividing to Men and Women. class Planet{ String name static hasMany = [ humans : Human ] } class Human{ String name static belongsTo = [Planet] } class Man extends Human{ int countOfCar } class Woman extends Human{ int coutOfChildren } now a neet to get only Collection of Man or Collection of Woman: get all humans on planet is simple all = Planet.get(1).humans but what can I get only woman or men? womenLivedOnMars = Planet.get(1).getOnlyWoman menLivedOnJupiter = Planet.get(2).getOnlyMan Thanks for your help Tom

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  • OO - inheritance vs. decoration problem

    - by Karel J
    Hi all, I have an OOP-related question. I have an interface, say: class MyInterface { public int getValue(); } In my project, this interface is implemented by 7 implementations: class MyImplementation1 implements MyInterface { ... } ... class MyImplementation7 implements MyInterface { ... } These implementations are used by several different modules. For some modules, the behaviour of the MyInterface must be adjusted slightly. Let's that it must return the value of the implementator + 1 (for the sake of example). I solved this by creating a little decorator: class MyDifferentInterface implements MyInterface { private MyInterface i; public MyDifferentInterface(MyInterface i) { this.i = i; } public int getValue() { return i.getValue() + 1; } } This does the job. Here is my problem: one of the modules doesn't accept an MyInterface parameter, but MyImplementation4 directly. The reason for this is that this module needs specific behaviour of MyImplementation4, which are not covered by the interface MyInterface on itself. But, and here comes the difficulty, this module must also work on the modified version of MyImplementation4. That is, getValue() must return +1; What is the best way to solve this? I fail to come up with a solution which does not include lots of code duplicates. Please note that although the example above is pretty small and simple, the interface and the decorator is quite large and complicated. Thanks a lot all.

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  • Rails Multiple Table Inheritance question

    - by Tony
    I am starting to implement an MTI solution and have a basic question. I have 3 physical models - SMSNotifications, EmailNotifications, TwitterNotifications and they are subclasses of notification. At times in my code, I want to say Notifications.find(:all)so that I can get a set of results sorted by their creation time. Then I want to do things based on their subclass. What is the way to write Notifications.find(:all) and have Rails look through the subclass tables and combine the results? Right now Rails still thinks I have a physical Notifications table which goes against my MTI design. I am also considering the possibility that I should be using STI instead. I would probably have 10 empty columns per row but if getting all notifications requires a query for each type of notification, then I feel like this could be a big issue. Thanks!

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  • C++ interface inheritance problem

    - by james t
    Hey, i'm trying to create a c++ stomp client, my client constructor is : Client(std::string &server, short port, std::string &login, std::string &pass, Listener &listener); it gets a listener object which when Listener is the following interface : class Listener { virtual void message(StmpMessage message) =0; }; now i attempt to instantiate a client in a test class : class test : public virtual Listener { public: void message(StmpMessage message) { message.prettyPrint(); } int main(int argc, char* argv[]) { Client client("127.0.0.1", 61613, *this); return 0; } }; i'm sending this to the client because this is a listener object, i get the following error : /Users/mzruya/Documents/STOMPCPP/main.cpp:18: error: no matching function for call to 'Client::Client(const char [10], int, test&)' /Users/mzruya/Documents/STOMPCPP/Client.h:43: note: candidates are: Client::Client(std::string&, short int, std::string&, std::string&, Listener&) /Users/mzruya/Documents/STOMPCPP/Client.h:37: note: Client::Client(const Client&)

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  • A "Trig" Calculating Class

    - by Clinton Scott
    I have been trying to create a gui that calculates trigonometric functions based off of the user's input. I have had success in the GUI part, but my class that I wrote to hold information using inheritance seems to be messed up, because when I run it gives an error saying: Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - constructor ArcTrigCalcCon in class TrigCalc.ArcTrigCalcCon cannot be applied to given types; required: double,double,double,double,double,double found: java.lang.Double,java.lang.Double,java.lang.Double reason: actual and formal argument lists differ in length at TrigCalc.TrigCalcGUI.(TrigCalcGUI.java:31) at TrigCalc.TrigCalcGUI.main(TrigCalcGUI.java:87) Java Result: 1 and says it is the object causing the problem. Below Will be my code. First I will put up my inheritance class with cosecant secant and cotangent and then my original class with the original 3 trig functions: { public ArcTrigCalcCon(double s, double cs, double t, double csc, double sc, double ct) { // Inherit from the Trig Calc class super(s, cs, t); cosecant = 1/s; secant = 1/cs; cotangent = 1/t; } public void setCsc(double csc) { cosecant = csc; } public void setSec(double sc) { secant = sc; } public void setCot(double ct) { cotangent = ct; } } Here is the first Trigonometric class: public class TrigCalcCon { public double sine; public double cosine; public double tangent; public TrigCalcCon(double s, double cs, double t) { sine = s; cosine = cs; tangent = t; } public void setSin(double s) { sine = s; } public void setCos(double cs) { cosine = cs; } public void setTan(double t) { tangent = t; } public void set(double s, double cs, double t) { sine = s; cosine = cs; tangent = t; } public double getSin() { return Math.sin(sine); } public double getCos() { return Math.cos(cosine); } public double getTan() { return Math.tan(tangent); } } and here is the demo class to run the gui: public class TrigCalcGUI extends JFrame implements ActionListener { // Instance Variables private String input; private Double s, cs, t, csc, sc, ct; private JPanel mainPanel, sinPanel, cosPanel, tanPanel, cscPanel, secPanel, cotPanel, buttonPanel, inputPanel, displayPanel; // Panel Display private JLabel sinLabel, cosLabel, tanLabel, secLabel, cscLabel, cotLabel, inputLabel; private JTextField sinTF, cosTF, tanTF, secTF, cscTF, cotTF, inputTF; //Text Fields for sin, cos, and tan, and inverse private JButton calcButton, clearButton; // Calculate and Exit Buttons // Object ArcTrigCalcCon trC = new ArcTrigCalcCon(s, cs, t); public TrigCalcGUI() { // title bar text. super("Trig Calculator"); // Corner exit button action. setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // Create main panel to add each panel to mainPanel = new JPanel(); mainPanel.setLayout(new GridLayout(3,2)); displayPanel = new JPanel(); displayPanel.setLayout(new GridLayout(3,2)); // Assign Panel to each variable inputPanel = new JPanel(); sinPanel = new JPanel(); cosPanel = new JPanel(); tanPanel = new JPanel(); cscPanel = new JPanel(); secPanel = new JPanel(); cotPanel = new JPanel(); buttonPanel = new JPanel(); // Call each constructor buildInputPanel(); buildSinCosTanPanels(); buildCscSecCotPanels(); buildButtonPanel(); // Add each panel to content pane displayPanel.add(sinPanel); displayPanel.add(cscPanel); displayPanel.add(cosPanel); displayPanel.add(secPanel); displayPanel.add(tanPanel); displayPanel.add(cotPanel); // Add three content panes to GUI mainPanel.add(inputPanel, BorderLayout.NORTH); mainPanel.add(displayPanel, BorderLayout.CENTER); mainPanel.add(buttonPanel, BorderLayout.SOUTH); //add mainPanel this.add(mainPanel); // size of window to content this.pack(); // display window setVisible(true); } public static void main(String[] args) { new TrigCalcGUI(); } private void buildInputPanel() { inputLabel = new JLabel("Enter a Value: "); inputTF = new JTextField(5); inputPanel.add(inputLabel); inputPanel.add(inputTF); } // Building Constructor for sinPanel cosPanel, and tanPanel private void buildSinCosTanPanels() { // Set layout and border for sinPanel sinPanel.setLayout(new GridLayout(2,2)); sinPanel.setBorder(BorderFactory.createTitledBorder("Sine")); // sinTF = new JTextField(5); sinTF.setEditable(false); sinPanel.add(sinTF); // Set layout and border for cosPanel cosPanel.setLayout(new GridLayout(2,2)); cosPanel.setBorder(BorderFactory.createTitledBorder("Cosine")); cosTF = new JTextField(5); cosTF.setEditable(false); cosPanel.add(cosTF); // Set layout and border for tanPanel tanPanel.setLayout(new GridLayout(2,2)); tanPanel.setBorder(BorderFactory.createTitledBorder("Tangent")); tanTF = new JTextField(5); tanTF.setEditable(false); tanPanel.add(tanTF); } // Building Constructor for cscPanel secPanel, and cotPanel private void buildCscSecCotPanels() { // Set layout and border for cscPanel cscPanel.setLayout(new GridLayout(2,2)); cscPanel.setBorder(BorderFactory.createTitledBorder("Cosecant")); // cscTF = new JTextField(5); cscTF.setEditable(false); cscPanel.add(cscTF); // Set layout and border for secPanel secPanel.setLayout(new GridLayout(2,2)); secPanel.setBorder(BorderFactory.createTitledBorder("Secant")); secTF = new JTextField(5); secTF.setEditable(false); secPanel.add(secTF); // Set layout and border for cotPanel cotPanel.setLayout(new GridLayout(2,2)); cotPanel.setBorder(BorderFactory.createTitledBorder("Cotangent")); cotTF = new JTextField(5); cotTF.setEditable(false); cotPanel.add(cotTF); } private void buildButtonPanel() { // Create buttons and add events calcButton = new JButton("Calculate"); calcButton.addActionListener(new CalcButtonListener()); clearButton = new JButton("Clear"); clearButton.addActionListener(new ClearButtonListener()); buttonPanel.add(calcButton); buttonPanel.add(clearButton); } @Override public void actionPerformed(ActionEvent e) { } private class CalcButtonListener implements ActionListener { public void actionPerformed(ActionEvent ae) { // Declare boolean variable boolean incorrect = true; // Set input variable to input text field text input = inputTF.getText(); ImageIcon newIcon; ImageIcon frowny = new ImageIcon(TrigCalcGUI.class.getResource("/Sad_Face.png")); Image gm = frowny.getImage(); Image newFrowny = gm.getScaledInstance(100, 100, java.awt.Image.SCALE_FAST); newIcon = new ImageIcon(newFrowny); // If boolean is true, throw exception if(incorrect) { try{Double.parseDouble(input); incorrect = false;} catch(NumberFormatException nfe) { String s = "Invalid Input " + "/n Input Must Be a Numerical value." + "/nPlease Press Ok and Try Again"; JOptionPane.showMessageDialog(null, s, "Invalid", JOptionPane.ERROR_MESSAGE, newIcon); inputTF.setText(""); inputTF.requestFocus(); } } // If boolean is not true, proceed with output if (incorrect != true) { /* Set each text field's output to the String double value * of inputTF */ sinTF.setText(input); cosTF.setText(input); tanTF.setText(input); cscTF.setText(input); secTF.setText(input); cotTF.setText(input); } } } /** * Private inner class that handles the event when * the user clicks the Exit button. */ private class ClearButtonListener implements ActionListener { public void actionPerformed(ActionEvent ae) { // Clear field sinTF.setText(""); cosTF.setText(""); tanTF.setText(""); cscTF.setText(""); secTF.setText(""); cotTF.setText(""); // Clear textfield and set cursor focus to field inputTF.setText(""); inputTF.requestFocus(); } } }

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  • edmx - The operation could not be completed - When adding Inheritance

    - by vdh_ant
    Hey guys I have an edmx model which I have draged 2 tables onto - One called 'File' and the other 'ApplicaitonFile'. These two tables have a 1 to 1 relationship in the database. If I stop here everything works fine. But in my model, I want 'ApplicaitonFile' to inherit from 'File'. So I delete the 1 to 1 relationship then configure 'ApplicaitonFile' from 'File' and then remove the FileId from 'ApplicaitonFile' which was the primary key. (Note I am following the instructions from here). If I leave the model open at this point everything is fine, but as soon as I close it, if I try and reopen it again I get the following error "The operation could not be completed". I have been searching for a solution and found this - http://stackoverflow.com/questions/944050/entity-model-does-not-load but as far as I can tell I don't have a duplicate InheritanceConnectors (although I don't know exactly what I'm looking for but I can't see anything out of the ordinary - like 2 connectors with the same name) and the relationship I originally have is a 1 to 1 not a 1 to 0..1 Any ideas??? this is driving me crazy...

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  • Dependency issue in inheritance chain

    - by Razer
    I have a class in coffeescript a class layout like the following. class @A foo: -> console.log('foo') class @B extends A fooB: -> @foo() class @C extends B fooC: -> @foo() I tried this in interpreters, it works. However it raises errors, when executing this in the browser (all of them are in separate coffee files, and are used in a global context. Therefore the @ before the class): Uncaught ReferenceError: B is not defined application.js It seems that B is defined after the definition of C. How can this happen?

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  • Rails STI validation inheritance

    - by KARASZI István
    Dear Rails users! I have STI models in my Rails application. The ancestor model has validations with the validates_... methods which are working fine. But I have custom validations as well, and I would like to add more different custom validations in the descendants. These custom validations would depend on the class. If I write class DescendantA < Ancestor protected def validate # ... end end It simply overwrites the original validations. Is there a convention to do this in Rails?

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  • Inheritance and type parameters of Traversable

    - by Jesper
    I'm studying the source code of the Scala 2.8 collection classes. I have questions about the hierarchy of scala.collection.Traversable. Look at the following declarations: package scala.collection trait Traversable[+A] extends TraversableLike[A, Traversable[A]] with GenericTraversableTemplate[A, Traversable] trait TraversableLike[+A, +Repr] extends HasNewBuilder[A, Repr] with TraversableOnce[A] package scala.collection.generic trait HasNewBuilder[+A, +Repr] trait GenericTraversableTemplate[+A, +CC[X] <: Traversable[X]] extends HasNewBuilder[A, CC[A] @uncheckedVariance] Question: Why does Traversable extend GenericTraversableTemplate with type parameters [A, Traversable] - why not [A, Traversable[A]]? I tried some experimenting with a small program with the same structure and got a strange error message when I tried to change it to Traversable[A]: error: Traversable[A] takes no type parameters, expected: one I guess that the use of the @uncheckedVariance annotation in GenericTraversableTemplate also has to do with this? (That seems like a kind of potentially unsafe hack to force things to work...). Question: When you look at the hierarchy, you see that Traversable inherits HasNewBuilder twice (once via TraversableLike and once via GenericTraversableTemplate), but with slightly different type parameters. How does this work exactly? Why don't the different type parameters cause an error?

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