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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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  • Problem with Classes in Python..

    - by Gui
    Ok guys, I'm really new at python (and programming itself) so sorry for my ignorance, but I really needed to ask this. So im doing a wxPython project where I added several tabs for a notebook (each tab of the notebook = a class) and there is one tab where I added a checkbox (in a tab, lets call it for example Tab1), and what I want is that when someone checks it, a button that exists in other tab (class called for example tab2) gets hidden where previously it was being shown. Well I see that it isn't hard to accomplish this, but my problem is the classes (tab1 and tab2, in this example). I've been trying to figure it out by searching but I guess im not searching hard enough because I just can't get it right. If they were in the same class I wouldn't have a problem, but as they are in different classes, im having a huge struggle with this. Hope someone can help me, and sorry for my ignorance once again.

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  • Events in Classes (VB.NET)

    - by Otaku
    I find that I write a lot of code within my classes to keep properties in sync with each other. I've read about Events in Classes, but have not been able to wrap my head around how to make them work for what I'm looking for. I could use some advice here. For example, in this one I always want to keep myColor up to date with any change whatsoever in any or all of the Red, Green or Blue properties. Class myColors Private Property Red As Byte Private Property Green As Byte Private Property Blue As Byte Private Property myColor As Color Sub New() myColor = Color.FromArgb(0, 0, 0) End Sub Sub ChangeRed(ByVal r As Byte) Red = r myColor = Color.FromArgb(Red, Green, Blue) End Sub Sub ChangeBlue(ByVal b As Byte) Blue = b myColor = Color.FromArgb(Red, Green, Blue) End Sub End Class If one or more of those changes, I want myColor to be updated. Easy enough as above, but is there a way to work with events that would automatically do this so I don't have to put myColor = Color.FromArgb(Red, Green, Blue) in every sub routine?

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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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  • Class Structure w/ LINQ, Partial Classes, and Abstract Classes

    - by Jason
    I am following the Nerd Dinner tutorial as I'm learning ASP.NET MVC, and I am currently on Step 3: Building the Model. One part of this section discusses how to integrate validation and business rule logic with the model classes. All this makes perfect sense. However, in the case of this source code, the author only validates one class: Dinner. What I am wondering is, say I have multiple classes that need validation (Dinner, Guest, etc). It doesn't seem smart to me to repeatedly write these two methods in the partial class: public bool IsValid { get { return (GetRuleViolations().Count() == 0); } } partial void OnValidate(ChangeAction action) { if (!IsValid) { throw new ApplicationException("Rule violations prevent saving."); } } What I'm wondering is, can you create an abstract class (because "GetRuleViolations" needs to be implemented separately) and extend a partial class? I'm thinking something like this (based on his example): public partial class Dinner : Validation { public IEnumerable<RuleViolation> GetRuleViolations() { yield break; } } This doesn't "feel" right, but I wanted to check with SO to get opinions of individuals smarter than me on this. I also tested it out, and it seems that the partial keyword on the OnValidate method is causing problems (understandably so). This doesn't seem possible to fix (but I could very well be wrong). Thanks!

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  • Interface and partial classes

    - by Tomek Tarczynski
    According to rule SA1201 in StyleCop elements in class must appear in correct order. The order is following: Fields Constructors Finalizers (Destructors) Delegates Events Enums Interfaces Properties Indexers Methods Structs Classes Everything is ok, except of Interfaces part, because Interface can contain mehtods, events, properties etc... If we want to be strict about this rule then we won't have all members of Interface in one place which is often very useful. According to StyleCop help this problem can be solved by spliting class into partial classes. Example: /// <summary> /// Represents a customer of the system. /// </summary> public partial class Customer { // Contains the main functionality of the class. } /// <content> /// Implements the ICollection class. /// </content> public partial class Customer : ICollection { public int Count { get { return this.count; } } public bool IsSynchronized { get { return false; } } public object SyncRoot { get { return null; } } public void CopyTo(Array array, int index) { throw new NotImplementedException(); } } Are there any other good solutions to this problem?

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  • Problem with inner classes of the same name in Visual C++

    - by starblue
    I have a problem with Visual C++, where apparently inner classes with the same name but in different outer classes are confused. The problem occurs for two layers, where each layer has a listener interface as an inner class. B is a listener of A, and has its own listener in a third layer above it (not shown). The structure of the code looks like this: A.h class A { class Listener { Listener(); virtual ~Listener() = 0; } [...] } B.h class B : public A::Listener { class Listener { Listener(); virtual ~Listener() = 0; } [...] } B.cpp B::Listener::Listener() {} B::Listener::~Listener() {} I get the error B.cpp(49) : error C2509: '{ctor}' : member function not declared in 'B' The C++ compiler for Renesas sh2a has no problem with this, but then it is more liberal than Visual C++ in some other respects, too. If I rename the listener interfaces to have different names the problem goes away, but I'd like to avoid that (the real class names instead of A or B are rather long). Is what I'm doing correct C++, or is the complaint by Visual C++ justified? Is there a way to work around this problem without renaming the listener interfaces?

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  • AS3 Classes - Should I use them?

    - by Eric
    I'm working on a project in Flash CS4/AS3 and I have a document class set up but I am wondering about using that, as opposed to frame-based scripting. Most of what I have seen so far deals with how to create them, but doesn't offer much about why or when to use them. I know I can also pull in other classes beyond the document class but, again, why and when? Could I get some input from you fine people out there on usage/best practice, etc? Thanks

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  • partial classes/partial class file

    - by Ravisha
    In C# .net there is a provision to have two different class files and make them a single class using the keyword partial keyword.this helps it to keep [for ex]UI and logic seperate. of course we can have two classes to achieve this one for UI and other for logic. Can this be achieved in java some how?

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  • PHP Classes Extend

    - by John
    I have two classes that work seperate from another, but they extend the same class. Is it possible to have them work the same instance of the extended class. I'm wanting the constructor of the extended class to run only once. I know this isn't right but something like this: <?php $oApp = new app; class a extends $oApp {} class b extends $oApp {}

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  • Does Javascript have classes?

    - by Glycerine
    A friend and I had an argument last week. He stated there were no such things as classes in Javascript. I said there was as you can say var object = new Object() he says "as there is no word class used. Its not a class. -- Whats your take on it guys? thanks.

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  • How to access java classes in a subfolder.

    - by Jacob
    Hi all. I'm trying to make a program that can load an unknown set of plugins from a sub-folder, "Plugins". All of these plugins implement the same interface. What I need to know is how do I find all of the classes in this folder so that I can instantiate and use them?

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  • penalty for "inlined" classes

    - by 2di
    Hi All Visual studio allow you to create "inlined" classes (if I am not mistaken with the name). So class header and implementation all in one file. H. file contain definitions and declarations of the class and functions, there is no .cpp file at all. So I was wondering if there is any penalty for doing it that way? any disadvantages ? Thanks a lot

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  • Catch requests to non-existent classes (not autoload)

    - by Spot
    Is there a manner in which to catch requests to a class which does not exist. I'm looking for something exactly like __call() and __static(), but for classes as opposed to methods in a class. I am not talking about autoloading. I need to be able to interrupt the request and reroute it. Ideas?

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  • How to deal with static utility classes when designing for testability

    - by Benedikt
    We are trying to design our system to be testable and in most parts developed using TDD. Currently we are trying to solve the following problem: In various places it is necessary for us to use static helper methods like ImageIO and URLEncoder (both standard Java API) and various other libraries that consist mostly of static methods (like the Apache Commons libraries). But it is extremely difficult to test those methods that use such static helper classes. I have several ideas for solving this problem: Use a mock framework that can mock static classes (like PowerMock). This may be the simplest solution but somehow feels like giving up. Create instantiable wrapper classes around all those static utilities so they can be injected into the classes that use them. This sounds like a relatively clean solution but I fear we'll end up creating an awful lot of those wrapper classes. Extract every call to these static helper classes into a function that can be overridden and test a subclass of the class I actually want to test. But I keep thinking that this just has to be a problem that many people have to face when doing TDD - so there must already be solutions for this problem. What is the best strategy to keep classes that use these static helpers testable?

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  • Classes as a compilation unit

    - by Yannbane
    If "compilation unit" is unclear, please refer to this. However, what I mean by it will be clear from the context. Edit: my language allows for multiple inheritance, unlike Java. I've started designing+developing my own programming language for educational, recreational, and potentially useful purposes. At first, I've decided to base it off Java. This implied that I would have all the code be written inside classes, and that code compiles to classes, which are loaded by the VM. However, I've excluded features such as interfaces and abstract classes, because I found no need for them. They seemed to be enforcing a paradigm, and I'd like my language not to do that. I wanted to keep the classes as the compilation unit though, because it seemed convenient to implement, familiar, and I just liked the idea. Then I noticed that I'm basically left with a glorified module system, where classes could be used either as "namespaces", providing constants and functions using the static directive, or as templates for objects that need to be instantiated ("actual" purpose of classes in other languages). Now I'm left wondering: what are the benefits of having classes as compilation units? (Also, any general commentary on my design would be much appreciated.)

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  • Python class design - Splitting up big classes into multiple ones to group functionality

    - by Ivo Wetzel
    OK I've got 2 really big classes 1k lines each that I currently have split up into multiple ones. They then get recombined using multiple inheritance. Now I'm wondering, if there is any cleaner/better more pythonic way of doing this. Completely factoring them out would result in endless amounts of self.otherself.do_something calls, which I don't think is the way it should be done. To make things clear here's what it currently looks like: from gui_events import GUIEvents # event handlers from gui_helpers import GUIHelpers # helper methods that don't directly modify the GUI # GUI.py class GUI(gtk.Window, GUIEvents, GUIHelpers): # general stuff here stuff here One problem that is result of this is Pylint complaining giving me trillions of "init not called" / "undefined attribute" / "attribute accessed before definition" warnings.

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  • How to import classes into other classes within the same file in Python

    - by Chris
    I have the file below and it is part of a django project called projectmanager, this file is projectmanager/projects/models.py . Whenever I use the python interpreter to import a Project just to test the functionality i get a name error for line 8 that FileRepo() cannot be found. How Can I import these classes correctly? Ideally what I am looking for is each Project to contain multiple FileRepos which each contain and unknown number of files. Thanks for any assistance in advance. #imports from django.db import models from django.contrib import admin #Project is responsible for ensuring that each project contains all of the folders and file storage #mechanisms a project needs, as well as a unique CCL# class Project(models.Model): ccl = models.CharField(max_length=30) Techpacks = FileRepo() COAS = FileRepo() Shippingdocs = FileRepo() POchemspecs = FileRepo() Internalpos = FileRepo() Finalreports = FileRepo() Batchrecords = FileRepo() RFPS = FileRepo() Businessdev = FileRepo() QA = FileRepo() Updates = FileRepo() def __unicode__(self): return self.ccl #ProjectFile is the file object used by each FileRepo component class ProjectFile(models.Model): file = models.FileField(uploadto='ProjectFiles') def __unicode__(self): return self.file #FileRepo is the model for the "folders" to be used in a Project class FileRepo(models.Model): typeOf = models.CharField(max_length=30) files = models.ManyToManyField(ProjectFile) def __unicode__(self): return self.typeOf

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  • Why does forward declaration not work with classes?

    - by eSKay
    int main() { B bb; //does not compile (neither does class B bb;) C cc; //does not compile struct t tt; //compiles class B {}; struct s { struct t * pt; }; //compiles struct t { struct s * ps; }; return 0; } class C {}; I just modified the example given here. Why is that the struct forward declarations work but not the class forward declarations? Does it have something to do with the namespaces - tag namespace and typedef namespace? I know that the structure definitions without typedefs go to tag namespace. Structures are just classes with all public members. So, I expect them to behave similarly.

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  • Problem using in GWT project classes from other project/source folders

    - by voipsecuritydigest.com
    My project contains 2 source folder, one is generic J2EE application another is smartCleintGWT, I want to use some already existing DTO classes from first source folder (src) Note that class used on client side and on server side of GWT project! When I do that I getting error [ERROR] Errors in 'file:/C:/..Projects/Admin/DMX/src_console/com/ho/nod/client/AdminRPC.java' [ERROR] Line 7: No source code is available for type com.dmx.synch.server.descriptors.DMXLicense; did you forget to inherit a required module? Source is available obviously; is there any way to import all that into GWT? PS In the future 2 source folder will be separated into 2 projects...I hope it wont be that complicated as well.

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  • Can you select an element with two classes in jQuery

    - by Petras
    I have an element that has two classes but can't seem to select it with jQuery. Is it possible. Here's the code: <html> <head runat="server"> <script type="text/javascript" src="abc/scripts/jquery-1.4.2.min.js"></script> <script type="text/javascript"> $(document).ready(function() { alert($(".x.y").html()); //shows null, I want it to show "456" }); </script> </head> <body> <div class="x" class"y">456</div> </body> </html>

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  • C++ Template Classes Circular Dependency Problem

    - by TomWij
    We have two classes: template<typename T, typename Size, typename Stack, typename Sparse> class Matrix and template<typename T, typename Size> class Iterator Matrix should be able to return begin and end iterators and Iterator will keep a referrence to the Matrix to access the elements via it's interface. We don't want Iterator to depend on the internal storage of the Matrix to prevent coupling. How can we solve this cyclic dependency problem? (The internal Storage class has the same template parameters as the Matrix class and the same access procedures as the Matrix itself)

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