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• Extending abstract classes in c#

  - by ng

  I am a Java developer and I have noticed some differences in extending abstract classes in c# as opposed to Java. I was wondering how a c# developer would achived the following. 1) Covarience public abstract class A { public abstract List<B> List(); } public class BList : List<T> where T : B { } public abstract class C : A { public abstract BList List(); } So in the above hierarchy, there is covarience in C where it returns a type compatible with what A returns. However this gives me an error in Visual Studio. Is there a way to specify a covarient return type in c#? 2) Adding a setter to a property public abstract class A { public abstract String Name { get; } } public abstract class B : A { public abstract String Name { get; set } } Here the compiler complains of hiding. Any suggestions? Please do not suggest using interfaces unless that is the ONLY way to do this.

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• How can I split Excel data from one row into multiple rows

  - by Lenny

  Good afternoon, Is there a way to split data from one row and store to separate rows? I have a large file that contains scheduling information and I'm trying to develop a list that comprises each combination of course, day, term and period per line. For example I have a file similiar to this: Crs:Sn Title Tchr TchrName Room Days Terms Periods 7014:01 English I 678 JUNG 300 M,T,W,R,F 3,4 2,3 1034:02 English II 123 MOORE 352 M,T,W,R,F 3 4 7144:02 Algebra 238 VYSOTSKY 352 M,T,W,R,F 3,4 3,4 0180:06 Pub Speaking 23 ROSEN 228 M,T,W,R,F 3,4 5 7200:03 PE I 244 HARILAOU GYM 4 M,T,W,R,F 1,2,3 3 2101:01 Physics/Lab 441 JONES 348 M,T,W,R,F 1,2,3,4 2,3 Should extract to this in an excel file: Crs:Sn Title Tchr# Tchr Room Days Terms Period 7014:01 English I 678 JUNG 300 M 3 2 7014:01 English I 678 JUNG 300 T 3 2 7014:01 English I 678 JUNG 300 W 3 2 7014:01 English I 678 JUNG 300 R 3 2 7014:01 English I 678 JUNG 300 F 3 2 7014:01 English I 678 JUNG 300 M 4 2 7014:01 English I 678 JUNG 300 T 4 2 7014:01 English I 678 JUNG 300 W 4 2 7014:01 English I 678 JUNG 300 R 4 2 7014:01 English I 678 JUNG 300 F 4 2 7014:01 English I 678 JUNG 300 M 3 3 7014:01 English I 678 JUNG 300 T 3 3 7014:01 English I 678 JUNG 300 W 3 3 7014:01 English I 678 JUNG 300 R 3 3 7014:01 English I 678 JUNG 300 F 3 3 7014:01 English I 678 JUNG 300 M 4 3 7014:01 English I 678 JUNG 300 T 4 3 7014:01 English I 678 JUNG 300 W 4 3 7014:01 English I 678 JUNG 300 R 4 3 7014:01 English I 678 JUNG 300 F 4 3 1034:02 English II 123 MOORE 352 M 3 4 1034:02 English II 123 MOORE 352 T 3 4 1034:02 English II 123 MOORE 352 W 3 4 1034:02 English II 123 MOORE 352 R 3 4 1034:02 English II 123 MOORE 352 F 3 4 7144:02 Algebra 238 VYSOTSKY 352 M 3 3 7144:02 Algebra 238 VYSOTSKY 352 T 3 3 7144:02 Algebra 238 VYSOTSKY 352 W 3 3 7144:02 Algebra 238 VYSOTSKY 352 R 3 3 7144:02 Algebra 238 VYSOTSKY 352 F 3 3 7144:02 Algebra 238 VYSOTSKY 352 M 4 3 7144:02 Algebra 238 VYSOTSKY 352 T 4 3 7144:02 Algebra 238 VYSOTSKY 352 W 4 3 7144:02 Algebra 238 VYSOTSKY 352 R 4 3 7144:02 Algebra 238 VYSOTSKY 352 F 4 3 7144:02 Algebra 238 VYSOTSKY 352 M 3 4 7144:02 Algebra 238 VYSOTSKY 352 T 3 4 7144:02 Algebra 238 VYSOTSKY 352 W 3 4 7144:02 Algebra 238 VYSOTSKY 352 R 3 4 7144:02 Algebra 238 VYSOTSKY 352 F 3 4 7144:02 Algebra 238 VYSOTSKY 352 M 4 4 7144:02 Algebra 238 VYSOTSKY 352 T 4 4 7144:02 Algebra 238 VYSOTSKY 352 W 4 4 7144:02 Algebra 238 VYSOTSKY 352 R 4 4 7144:02 Algebra 238 VYSOTSKY 352 F 4 4 0180:06 Pub Speaking 23 ROSEN 228 M 3 5 0180:06 Pub Speaking 23 ROSEN 228 T 3 5 0180:06 Pub Speaking 23 ROSEN 228 W 3 5 0180:06 Pub Speaking 23 ROSEN 228 R 3 5 0180:06 Pub Speaking 23 ROSEN 228 F 3 5 0180:06 Pub Speaking 23 ROSEN 228 M 4 5 0180:06 Pub Speaking 23 ROSEN 228 T 4 5 0180:06 Pub Speaking 23 ROSEN 228 W 4 5 0180:06 Pub Speaking 23 ROSEN 228 R 4 5 0180:06 Pub Speaking 23 ROSEN 228 F 4 5 7200:03 PE I 244 HARILAOU GYM 4 M 1 3 7200:03 PE I 244 HARILAOU GYM 4 M 2 3 7200:03 PE I 244 HARILAOU GYM 4 M 3 3 7200:03 PE I 244 HARILAOU GYM 4 T 1 3 7200:03 PE I 244 HARILAOU GYM 4 T 2 3 7200:03 PE I 244 HARILAOU GYM 4 T 3 3 7200:03 PE I 244 HARILAOU GYM 4 W 1 3 7200:03 PE I 244 HARILAOU GYM 4 W 2 3 7200:03 PE I 244 HARILAOU GYM 4 W 3 3 7200:03 PE I 244 HARILAOU GYM 4 R 1 3 7200:03 PE I 244 HARILAOU GYM 4 R 2 3 7200:03 PE I 244 HARILAOU GYM 4 R 3 3 7200:03 PE I 244 HARILAOU GYM 4 F 1 3 7200:03 PE I 244 HARILAOU GYM 4 F 2 3 7200:03 PE I 244 HARILAOU GYM 4 F 3 3 2101:01 Physics/Lab 441 JONES 348 M 1 2 2101:01 Physics/Lab 441 JONES 348 M 2 2 2101:01 Physics/Lab 441 JONES 348 M 3 2 2101:01 Physics/Lab 441 JONES 348 M 4 2 2101:01 Physics/Lab 441 JONES 348 T 1 2 2101:01 Physics/Lab 441 JONES 348 T 2 2 2101:01 Physics/Lab 441 JONES 348 T 3 2 2101:01 Physics/Lab 441 JONES 348 T 4 2 2101:01 Physics/Lab 441 JONES 348 W 1 2 2101:01 Physics/Lab 441 JONES 348 W 2 2 2101:01 Physics/Lab 441 JONES 348 W 3 2 2101:01 Physics/Lab 441 JONES 348 W 4 2 2101:01 Physics/Lab 441 JONES 348 R 1 2 2101:01 Physics/Lab 441 JONES 348 R 2 2 2101:01 Physics/Lab 441 JONES 348 R 3 2 2101:01 Physics/Lab 441 JONES 348 R 4 2 2101:01 Physics/Lab 441 JONES 348 F 1 2 2101:01 Physics/Lab 441 JONES 348 F 2 2 2101:01 Physics/Lab 441 JONES 348 F 3 2 2101:01 Physics/Lab 441 JONES 348 F 4 2 2101:01 Physics/Lab 441 JONES 348 M 1 3 2101:01 Physics/Lab 441 JONES 348 M 2 3 2101:01 Physics/Lab 441 JONES 348 M 3 3 2101:01 Physics/Lab 441 JONES 348 M 4 3 2101:01 Physics/Lab 441 JONES 348 T 1 3 2101:01 Physics/Lab 441 JONES 348 T 2 3 2101:01 Physics/Lab 441 JONES 348 T 3 3 2101:01 Physics/Lab 441 JONES 348 T 4 3 2101:01 Physics/Lab 441 JONES 348 W 1 3 2101:01 Physics/Lab 441 JONES 348 W 2 3 2101:01 Physics/Lab 441 JONES 348 W 3 3 2101:01 Physics/Lab 441 JONES 348 W 4 3 2101:01 Physics/Lab 441 JONES 348 R 1 3 2101:01 Physics/Lab 441 JONES 348 R 2 3 2101:01 Physics/Lab 441 JONES 348 R 3 3 2101:01 Physics/Lab 441 JONES 348 R 4 3 2101:01 Physics/Lab 441 JONES 348 F 1 3 2101:01 Physics/Lab 441 JONES 348 F 2 3 2101:01 Physics/Lab 441 JONES 348 F 3 3 2101:01 Physics/Lab 441 JONES 348 F 4 3 I'm trying to avoid going line by line separating the data. I'm not well versed on the VBA functionality of Excel, but would like to get started using it. Any help would be greatly appreciated.

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• Linear Algebra Library For Android

  - by James

  Does anyone know what will be a good library for computing linear algebra in Android (SVD, QR, LU, least-squares, inverse, etc) ?

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• How to avoid general names for abstract classes?

  - by djechlin

  In general it's good to avoid words like "handle" or "process" as part of routine names and class names, unless you are dealing with (e.g.) file handles or (e.g.) unix processes. However abstract classes often don't really know what they're going to do with something besides, say, process it. In my current situation I have an "EmailProcessor" that logs into a user's inbox and processes messages from it. It's not really clear to me how to give this a more precise name, although I've noticed the following style matter arises: better to treat derived classes as clients and named the base class by the part of the functionality it implements? Gives it more meaning but will violate is-a. E.g. EmailAcquirer would be a reasonable name since it's acquiring for the derived class, but the derived class won't be acquiring for anyone. Or just really vague name since who knows what the derived classes will do. However "Processor" is still too general since it's doing many relevant operations, like logging in and using IMAP. Any way out of this dilemma? Problem is more evident for abstract methods, in which you can't really answer the question "what does this do?" because the answer is simply "whatever the client wants."

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• Getting link to abstract indexed in Google Scholar

  - by JordanReiter

  We have a large digital library with thousands of papers indexed in Google Scholar. We allow Google Scholar to index our PDFs but they're blocked unless you have a subscription. So Google has full-text indexing/searching of our PDFs (great!) but then the links point just to those PDFs (boo!) instead of the more helpful abstract pages. Does anyone know what could cause an issue like this? I am, to the best of my knowledge, following all of the guidelines laid out in their Inclusion Guidelines. Here's some example meta data: <meta name="citation_title" content="Sample Title"/> <meta name="citation_author" content="LastName, FirstName"/> <meta name="citation_publication_date" content="2012/06/26"/> <meta name="citation_volume" content="1"/> <meta name="citation_issue" content="1"/> <meta name="citation_firstpage" content="10"/> <meta name="citation_lastpage" content="20"/> <meta name="citation_conference_title" content="Name of the Conference"/> <meta name="citation_isbn" content="1-234567-89-X"/> <meta name="citation_pdf_url" content="http://www.example.org/p/1234/proceeding_1234.pdf"/> <meta name="citation_fulltext_html_url" content="http://www.example.org/f/1234/"/> <meta name="citation_abstract_html_url" content="http://www.example.org/p/1234/"/> <link rel="canonical" href="http://www.example.org/p/1234/" /> example.org/p/1234 is the abstract page for the article; example.org/f/1234 is the fulltext link accessible to subscribers only (and to Google Scholar). example.org/p/1234/proceeding_1234.pdf is the fulltext PDF link.

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• What am I not getting about this abstract class implementation?

  - by Schnapple

  PREFACE: I'm relatively inexperienced in C++ so this very well could be a Day 1 n00b question. I'm working on something whose long term goal is to be portable across multiple operating systems. I have the following files: Utilities.h #include <string> class Utilities { public: Utilities() { }; virtual ~Utilities() { }; virtual std::string ParseString(std::string const& RawString) = 0; }; UtilitiesWin.h (for the Windows class/implementation) #include <string> #include "Utilities.h" class UtilitiesWin : public Utilities { public: UtilitiesWin() { }; virtual ~UtilitiesWin() { }; virtual std::string ParseString(std::string const& RawString); }; UtilitiesWin.cpp #include <string> #include "UtilitiesWin.h" std::string UtilitiesWin::ParseString(std::string const& RawString) { // Magic happens here! // I'll put in a line of code to make it seem valid return ""; } So then elsewhere in my code I have this #include <string> #include "Utilities.h" void SomeProgram::SomeMethod() { Utilities *u = new Utilities(); StringData = u->ParseString(StringData); // StringData defined elsewhere } The compiler (Visual Studio 2008) is dying on the instance declaration c:\somepath\somecode.cpp(3) : error C2259: 'Utilities' : cannot instantiate abstract class due to following members: 'std::string Utilities::ParseString(const std::string &)' : is abstract c:\somepath\utilities.h(9) : see declaration of 'Utilities::ParseString' So in this case what I'm wanting to do is use the abstract class (Utilities) like an interface and have it know to go to the implemented version (UtilitiesWin). Obviously I'm doing something wrong but I'm not sure what. It occurs to me as I'm writing this that there's probably a crucial connection between the UtilitiesWin implementation of the Utilities abstract class that I've missed, but I'm not sure where. I mean, the following works #include <string> #include "UtilitiesWin.h" void SomeProgram::SomeMethod() { Utilities *u = new UtilitiesWin(); StringData = u->ParseString(StringData); // StringData defined elsewhere } but it means I'd have to conditionally go through the different versions later (i.e., UtilitiesMac(), UtilitiesLinux(), etc.) What have I missed here?

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• Can I use an abstract class instead of a private __construct() when creating a singleton in PHP?

  - by Pheter

  When creating a Singleton in PHP, I ensure that it cannot be instantiated by doing the following: class Singleton { private function __construct() {} private function __clone() {} public static function getInstance() {} } However, I realised that defining a class as 'abstract' means that it cannot be instantiated. So is there anything wrong with doing the following instead: abstract class Singleton { public static function getInstance() {} } The second scenario allows me to write fewer lines of code which would be nice. (Not that it actually makes much of a difference.)

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• Is it possible for an abstract class to force it's children to have a constructor in PHP?

  - by Logan Serman

  I would like to do something like this: abstract class Foo { public function __construct() { echo 'This is the parent constructor'; } abstract function __construct(); } class Bar extends Foo { // constructor is required as this class extends Foo public function __construct() { //call parent::__construct() if necessary echo 'This is the child constructor'; } } But I get a fatal error when doing this: Fatal error: Cannot redeclare Foo::__construct() in Foo.php on line 8 Is there another way to ensure child classes have a constructor?

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• How to determine which inheriting class is using an abstract class' methods.

  - by Kin

  In my console application have an abstract Factory class "Listener" which contains code for listening and accepting connections, and spawning client classes. This class is inherited by two more classes (WorldListener, and MasterListener) that contain more protocol specific overrides and functions. I also have a helper class (ConsoleWrapper) which encapsulates and extends System.Console, containing methods for writing to console info on what is happening to instances of the WorldListener and MasterListener. I need a way to determine in the abstract ListenerClass which Inheriting class is calling its methods. Any help with this problem would be greatly appreciated! I am stumped :X Simplified example of what I am trying to do. abstract class Listener { public void DoSomething() { if(inheriting class == WorldListener) ConsoleWrapper.WorldWrite("Did something!"); if(inheriting class == MasterListener) ConsoleWrapper.MasterWrite("Did something!"); } } public static ConsoleWrapper { public void WorldWrite(string input) { System.Console.WriteLine("[World] {0}", input); } } public class WorldListener : Listener { public void DoSomethingSpecific() { ConsoleWrapper.WorldWrite("I did something specific!"); } } public void Main() { new WorldListener(); new MasterListener(); } Expected output [World] Did something! [World] I did something specific! [Master] Did something! [World] I did something specific!

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• How to determine which inheriting class is using an abstract class's methods.

  - by Kin

  In my console application have an abstract Factory class "Listener" which contains code for listening and accepting connections, and spawning client classes. This class is inherited by two more classes (WorldListener, and MasterListener) that contain more protocol specific overrides and functions. I also have a helper class (ConsoleWrapper) which encapsulates and extends System.Console, containing methods for writing to console info on what is happening to instances of the WorldListener and MasterListener. I need a way to determine in the abstract ListenerClass which Inheriting class is calling its methods. Any help with this problem would be greatly appreciated! I am stumped :X Simplified example of what I am trying to do. abstract class Listener { public void DoSomething() { if(inheriting class == WorldListener) ConsoleWrapper.WorldWrite("Did something!"); if(inheriting class == MasterListener) ConsoleWrapper.MasterWrite("Did something!"); } } public static ConsoleWrapper { public void WorldWrite(string input) { System.Console.WriteLine("[World] {0}", input); } } public class WorldListener : Listener { public void DoSomethingSpecific() { ConsoleWrapper.WorldWrite("I did something specific!"); } } public void Main() { new WorldListener(); new MasterListener(); } Expected output [World] Did something! [World] I did something specific! [Master] Did something! [World] I did something specific!

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• Is there a case for parameterising using Abstract classes rather than Interfaces?

  - by Chris

  I'm currently developing a component based API that is heavily stateful. The top level components implement around a dozen interfaces each. The stock top-level components therefore sit ontop of a stack of Abstract implementations which in turn contain multiple mixin implementations and implement multiple mixin interfaces. So far, so good (I hope). The problem is that the base functionality is extremely complex to implement (1,000s of lines in 5 layers of base classes) and therefore I do not wish for component writers to implement the interfaces themselves but rather to extend my base classes (where all the boiler plate code is already written). If the API therefore accepts interfaces rather than references to the Abstract implementation that I wish for component writers to extends, then I have a risk that the implementer will not perform the validation that is both required and assumed by other areas of code. Therefore, my question is, is it sometimes valid to paramerise API methods using an abstract implementation reference rather than a reference to the interface(s) that it implements? Do you have an example of a well-designed API that uses this technique or am I trying to talk myself into bad-practice?

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• Which of these design patterns is superior?

  - by durron597

  I find I tend to design class structures where several subclasses have nearly identical functionality, but one piece of it is different. So I write nearly all the code in the abstract class, and then create several subclasses to do the one different thing. Does this pattern have a name? Is this the best way for this sort of scenario? Option 1: public interface TaxCalc { String calcTaxes(); } public abstract class AbstractTaxCalc implements TaxCalc { // most constructors and fields are here public double calcTaxes(UserFinancials data) { // code double diffNumber = getNumber(data); // more code } abstract protected double getNumber(UserFinancials data); protected double initialTaxes(double grossIncome) { // code return initialNumber; } } public class SimpleTaxCalc extends AbstractCalc { protected double getNumber(UserFinancials data) { double temp = intialCalc(data.getGrossIncome()); // do other stuff return temp; } } public class FancyTaxCalc extends AbstractTaxCalc { protected double getNumber(UserFinancials data) { int temp = initialCalc(data.getGrossIncome()); // Do fancier math return temp; } } Option 2: This version is more like the Strategy pattern, and should be able to do essentially the same sorts of tasks. public class TaxCalcImpl implements TaxCalc { private final TaxMath worker; public DummyImpl(TaxMath worker) { this.worker = worker; } public double calcTaxes(UserFinancials data) { // code double analyzedDouble = initialNumber; int diffNumber = worker.getNumber(data, initialNumber); // more code } protected int initialTaxes(double grossIncome) { // code return initialNumber; } } public interface TaxMath { double getNumber(UserFinancials data, double initial); } Then I could do: TaxCalc dum = new TaxCalcImpl(new TaxMath() { @Override public double getNumber(UserFinancials data, double initial) { double temp = data.getGrossIncome(); // do math return temp; }); And I could make specific implementations of TaxMath for things I use a lot, or I could make a stateless singleton for certain kinds of workers I use a lot. So the question I'm asking is: Which of these patterns is superior, when, and why? Or, alternately, is there an even better third option?

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• How can I make an "abstract" enum in a .NET class library?

  - by Lazlo

  I'm making a server library in which the packet association is done by enum. public enum ServerOperationCode : byte { LoginResponse = 0x00, SelectionResponse = 0x01, BlahBlahResponse = 0x02 } public enum ClientOperationCode : byte { LoginRequest = 0x00, SelectionRequest = 0x01, BlahBlahRequest = 0x02 } That works fine when you're working in your own project - you can compare which enum member is returned (i.e. if (packet.OperationCode == ClientOperationCode.LoginRequest)). However, since this is a class library, the user will have to define its own enum. Therefore, I have two enums to add as "abstract" - ServerOperationCode and ClientOperationCode. I know it's not possible to implement abstract enums in C#. How would I go doing this?

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• How do I ensure my abstract class's function can only operate on extenders of the same type as the c

  - by incrediman

  For example, let's say this is my abstract class: abstract class A{ int x; int y; void foo(A fooMe); } ...and B and C are two classes which extend A. What I want is for B to only be able to call foo() on other Bs, and for C to only be able to call foo() on other Cs. But I want this to be out of the hands of the programmer who's extending my A class - that is, I want a way to ensure this functionality within As code alone. What can I do? (If possible) I'd like to avoid any hack or generics solution that's too messy - I still want foo to be able to be called like this, for example: B b=new B(); B bb=new B(); bb.foo(b);

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• Using Lazy<T> and abstract wrapper class to lazy-load complex system parameters

  - by DigiMortal

  .NET Framework 4.0 introduced new class called Lazy<T> and I wrote blog post about it: .Net Framework 4.0: Using System.Lazy<T>. One thing is annoying for me – we have to keep lazy loaded value and its value loader as separate things. In this posting I will introduce you my Lazy<T> wrapper for complex to get system parameters that uses template method to keep lazy value loader in parameter class. Problem with original implementation Here’s the sample code that shows you how Lazy<T> is usually used. This is just sample code, don’t focus on the fact that this is dummy console application. class Program {     static void Main(string[] args)     {         var temperature = new Lazy<int>(LoadMinimalTemperature);           Console.WriteLine("Minimal room temperature: " + temperature.Value);         Console.ReadLine();     }       protected static int LoadMinimalTemperature()     {         var returnValue = 0;           // Do complex stuff here           return true;     } } The problem is that our class with many lazy loaded properties will grow messy if it has all value loading code inside it. This code may be complex for more than one parameter and in this case it is better to use separate class for this parameter. Defining base class for parameters As a first step I will define base class for all lazy-loaded parameters. This class is wrapper around Lazy<T> and it also offers one template method that parameter classes have to override to provide loaded data. public abstract class LazyParameter<T> {     private Lazy<T> _lazyParam;       public LazyParameter()     {         _lazyParam = new Lazy<T>(Load);     }       protected abstract T Load();       public T Value     {         get { return _lazyParam.Value; }     } } It is also possible to extend Lazy<T> but I don’t prefer to do it as Lazy<T> has six constructors we have to take care of. Also I don’t like to expose Lazy<T> public interface to users of my parameter classes. Creating parameter class Now it’s time to create our first parameter class. Notice how few stuff we have in this class besides overridden Load() method. public class MinimalRoomTemperature : LazyParameter<int> {     protected override int Load()     {         var returnValue = 0;           // Do complex stuff here           return returnValue;     } } Using parameter class is simple. Here’s my test code. class Program {     static void Main(string[] args)     {         var parameter = new MinimalRoomTemperature();         Console.WriteLine("Minimal room temperature: " + parameter.Value);         Console.ReadLine();     } } Conclusion Lazy<T> is useful class that you usually don’t want to use outside from API-s. I like this class but I don’t like when people are using this class directly in application code. In this posting I showed you how to use Lazy<T> with wrapper class to get complex parameter loading code out from classes that use this parameter. We ended up with generic base class for parameters that you can also use as base for other similar classes (you have to find better name to base class in this case).

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• Pure virtual or abstract, what's in a name?

  - by Steven Jeuris

  While discussing a question about virtual functions on Stack Overflow, I wondered whether there was any official naming for pure (abstract) and non-pure virtual functions. I always relied on wikipedia for my information, which states that pure and non-pure virtual functions are the general term. Unfortunately, the article doesn't back it up with a origin or references. To quote Jon Skeet's answer to my reply that pure and non-pure are the general term used: @Steven: Hmm... possibly, but I've only ever seen it in the context of C++ before. I suspect anyone talking about them is likely to have a C++ background :) Did the terms originate from C++, or were they first defined or implemented in a earlier language, and are they the 'official' scientific terms?

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• Absent Code attribute in method that is not native or abstract

  - by kerry

  I got the following, quite puzzling error today when running a unit test: java.lang.ClassFormatError: Absent Code attribute in method that is not native or abstract in class file javax/servlet/http/Cookie A google search found this post, which explains that it is caused by having an interface in the classpath, and not an actual implementation. In this case it’s the java-ee interface. To fix this I added the jetty servlet api implementation to my pom: jetty javax.servlet test Piece of cake. I have run in to this before, so I figured I would capture the fix here in case I run in to it again.

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• Abstract Data Type and Data Structure

  - by mark075

  It's quite difficult for me to understand these terms. I searched on google and read a little on Wikipedia but I'm still not sure. I've determined so far that: Abstract Data Type is a definition of new type, describes its properties and operations. Data Structure is an implementation of ADT. Many ADT can be implemented as the same Data Structure. If I think right, array as ADT means a collection of elements and as Data Structure, how it's stored in a memory. Stack is ADT with push, pop operations, but can we say about stack data structure if I mean I used stack implemented as an array in my algorithm? And why heap isn't ADT? It can be implemented as tree or an array.

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• How abstract should you get with BDD

  - by Newton

  I was writing some tests in Gherkin (using Cucumber/Specflow). I was wondering how abstract should I get with my tests. In order to not make this open-ended, which of the following statements is better for BDD: Given I am logged in with email [email protected] and password 12345 When I do something Then something happens as opposed to Given I am logged in as the Administrator When I do something Then something happens The reason I am confused is because 1 is more based on the behaviour (filing in email and password) and 2 is easier to process and write the tests.

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• Who should map physical keys to abstract keys?

  - by Paul Manta

  How do you bridge the gap between the library's low-level event system and your engine's high-level event system? (I'm not necessarily talking about key events, but also about quit events.) At the top level of my event system, I send out KeyPressedEvents, KeyRelesedEvents and others of this kind. These high-level events only contain the abstract values of the keys (they don't say that Space way pressed, but that the JumpKey was pressed, for example). Whose responsibility should it be to map the "JumpKey" to an actual key on the keyboard?

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• Upcoming EBS Webcasts for June, July, August 2012

  - by user793553

  See the following upcoming webcasts for June, July and August 2012. Flag Doc ID 740966.1 as a favourite, to keep up to date with latest advisor schedule. Additionally, see Doc ID 740964.1 for access to all archived advisor webcasts Oracle E-Business Suite Oracle E-Business Suite Title Date Summary None at this time.     EBS Agile Title Date Summary None at this time.     EBS Applications Technologies Group (ATG) Title Date Summary EBS – OAM Tuning and Monitoring EMEA July 10, 2012 Abstract EBS – OAM Tuning and Monitoring US July 11, 2012 Abstract Workflow Analyzer Followup EMEA July 24, 2012 Abstract Workflow Analyzer Followup US July 25, 2012 Abstract EBS CRM & Industries Title Date Summary None at this time.     EBS Financials Title Date Summary EBS Fixed Assets: Achieve Success Using Proactive Tools For Fixed Assets Support July 10, 2012 Abstract Overview and Flow of Oracle Project Resource Management July 17, 2012 Abstract Leveraging My Oracle Support To Increase Knowledge July 30, 2012 Abstract EBS HCM (HRMS) Title Date Summary Oracle Time and Labor (OTL) Rollback Functionality Session 1 July 25, 2012 Abstract Oracle Time and Labor (OTL) Rollback Functionality Session 2 July 25, 2012 Abstract EBS Manufacturing Title Date Summary Using Personalization in Oracle eAM June 21, 2012 Abstract OM Guided Resolutions - Finding Known Resolutions Easily July 17, 2012 Abstract Material Move Orders Flow July 25, 2012 Abstract Diagnosing Signal 11 Issues In ASCP Planning August 9, 2012 Abstract Interface Trip Stop - Best Practices and Debugging August 21, 2012 Abstract EBS Procurement Title Date Summary Punchout in iProcurement June 26, 2012 Abstract

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• Abstract skill/talent system implementation

  - by kiliki

  I've been making small 2D games for about 3 years now (XNA and more recently LWJGL/Slick2D). My latest idea would involve some form of "talent tree" system in a real time game. I've been wracking my brain but can't think of a structure to hold a talent. Something like "Your melee attack is an instant kill if behind the target" I'd like to come up with an abstract object rather than putting random conditionals into other methods. I've solved some relatively complex problems before but I don't even know where to begin with this one. Any help would be appreciated - Java, pseudocode or general concepts are all great.

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• How to work with PHP abstract?

  - by YumYumYum

  Why would you use such abstract? Does it speed up work or what exactly its for? // file1.php abstract class Search_Adapter_Abstract { private $ch = null; abstract private function __construct() { } abstract public funciton __destruct() { curl_close($this->ch); } abstract public function search($searchString,$offset,$count); } // file2.php include("file1.php"); class abc extends Search_Adapter_Abstract { // Will the curl_close now automatically be closed? } What is the reason of extending abstract here? Makes me confused. What can i get from it now?

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• Java abstract visitor - guarantueed to succeed? If so, why?

  - by disown

  I was dealing with hibernate, trying to figure out the run-time class behind proxied instances by using the visitor pattern. I then came up with an AbstractVisitable approach, but I wonder if it will always produce correct results. Consider the following code: interface Visitable { public void accept(Visitor v); } interface Visitor { public void visit(Visitable visitorHost); } abstract class AbstractVisitable implements Visitable { @Override public void accept(Visitor v) { v.visit(this); } } class ConcreteVisitable extends AbstractVisitable { public static void main(String[] args) { final Visitable visitable = new ConcreteVisitable(); final Visitable proxyVisitable = (Visitable) Proxy.newProxyInstance( Thread.currentThread().getContextClassLoader(), new Class<?>[] { Visitable.class }, new InvocationHandler() { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { return method.invoke(visitable, args); } }); proxyVisitable.accept(new Visitor() { @Override public void visit(Visitable visitorHost) { System.out.println(visitorHost.getClass()); } }); } } This makes a ConcreteVisitable which inherits the accept method from AbstractVisitable. In c++, I would consider this risky, since this in AbstractVisitable could be referencing to AbstractVisitable::this, and not ConcreteVisitable::this. I was worried that the code under certain circumstances would print class AbstractVisible. Yet the code above outputs class ConcreteVisitable, even though I hid the real type behind a dynamic proxy (the most difficult case I could come up with). Is the abstract visitor approach above guaranteed to work, or are there some pitfalls with this approach? What guarantees are given in Java with respect to the this pointer?

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• (Abstract) Game engine design

  - by lukeluke

  I am writing a simple 2D game (for mobile platforms) for the first time. From an abstract point of view, i have the main player controlled by the human, the enemies, elments that will interact with the main player, other living elements that will be controlled by a simple AI (both enemies and non-enemies). The human player will be totally controlled by the player, the other actors will be controlled by AI. So i have a class CActor and a class CActorLogic to start with. I would define a CActor subclass CHero (the main player controlled with some input device). This class will probably implement some type of listener, in order to capture input events. The other players controlled by the AI will be probably a specific subclass of CActor (a subclass per-type, obviously). This seems to be reasonable. The CActor class should have a reference to a method of CActorLogic, that we will call something like CActorLogic::Advance() or similar. Actors should have a visual representation. I would introduce a CActorRepresentation class, with a method like Render() that will draw the actor (that is, the right frame of the right animation). Where to change the animation? Well, the actor logic method Advance() should take care of checking collisions and other things. I would like to discuss the design of a game engine (actors, entities, objects, messages, input handling, visualization of object states (that is, rendering, sound output and so on)) but not from a low level point of view, but from an high level point of view, like i have described above. My question is: is there any book/on line resource that will help me organize things (using an object oriented approach)? Thanks

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