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• Just how much do I want to make virtual?

  - by Alex

  I am writing an abstract superclass where literally every method is going to be overridden. There is some default functionality I could implement, but most of the time it's enough to leave the implementation to the subclass writer. Since just about every method is going to be overwritten, how much should I make virtual and how much should I just leave as regular methods? In the current incarnation, everything is virtual, but I still haven't let this loose to anyone to use, so the design is flexible. What advantages/disadvantages are there to virtual functions? Links to good reading material about this would be appreciated.

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• Java: Can't implement runnable on a test case: void run() collides

  - by Zombies

  So I have a test case that I want to make into a thread. I cannot extend Thread nor can I implement runnable since TestCase already has a method void run(). The compilation error I am getting is Error(62,17): method run() in class com.util.SeleneseTestCase cannot override method run() in class junit.framework.TestCase with different return type, was class junit.framework.TestResult. What I am trying to do is to scale a Selenium testcase up to perform stress testing. I am not able to use selenium grid/pushtotest.com/amazon cloud at this time (installation issues/install time/resource issues). So this really is more of a Java language issue for me.

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• python challenge, but for C++

  - by davidthepsycho

  Does anyone know any site or book that presents problems like python challenge, but for C++? When I think python challenge, I do not mean only a set of problems to be solved with C++ (for that I could probably use the same problems of python challenge), but rather problems that will probably be best solved using C++ STL, special features of the language, etc. For example, there is one python challenge that is specifically designed to teach you how to use pickle, a serializing library for python. Until now, I only know programming contests problems, but they could also be solved with C, java or other languages.

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• In Django, using __init__() method of non-abstract parent model to record class name of child model

  - by k-g-f

  In my Django project, I have a non-abstract parent model defined as follows: class Parent(models.Model): classType = models.CharField(editable=False,max_length=50) and, say, two children models defined as follows: class ChildA(Parent): parent = models.OneToOneField(Parent,parent_link=True) class ChildB(Parent): parent = models.OneToOneField(Parent,parent_link=True) Each time I create an instance of ChildA or of ChildB, I'd like the classType attribute to be set to the strings "ChildA" or "ChildB" respectively. What I have done is added an _ _ init_ _() method to Parent as follows: class Parent(models.Model): classType = models.CharField(editable=False,max_length=50) def __init__(self,*args,**kwargs): super(Parent,self).__init__(*args,**kwargs) self.classType = self.__class__.__name__ Is there a better way to implement and achieve my desired result? One downside of this implementation is that when I have an instance of the Parent, say "parent", and I want to get the type of the child object linked with "parent", calling "parent.classType" gives me "Parent". In order to get the appropriate "ChildA" or "ChildB" value, I need to write a "_getClassType()" method to wrap a custom sql query.

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• control.focus() after selectedIndexChanged

  - by kyle

  I need to focus on a textbox after an item has been selected from a dropdownlist. I've tried control.focus() and setfocus(). The last thing I've tried was Set_Focus(dtbEffectiveDate.ClientID) inside the SelectedIndexChanged method with the folowing method. Protected Sub Set_Focus(ByVal ControlName As String) Dim strScript As String strScript = "<script language=javascript> window.setTimeout(""" + ControlName + ".focus();"",0); </script>" RegisterStartupScript("focus", strScript) End Sub I'm out of answers so any help would be awesome.

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• Getting changes in one column of an historical table

  - by Javi

  Hello, I have a table which stores historical data. It's mapped to an Entity with the following fields (I use JPA with Hibernate implementation): @Entity @Table(name="items_historical") public class ItemHistory{ private Integer id; private Date date; @Enumerated(EnumType.ORDINAL) private StatusEnum status @ManyToOne(optional=false) private User user; @ManyToOne(optional=false) private Item item; } public enum StatusEnum { OK, BAD,...//my status } In every row I store historical data of another table. I need to get the list of the changes on "status" column: the status, the date and the previous status on a specified item (It would be good as well getting the status and date when status was changed). I don't know if this is possible by using HQL. Thanks.

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• Windows Form Components Access

  - by rxm0203

  What is the best way to access components (e.g. imagelist, timer) from a form instance? I am working on multi form windows forms application on .NET Compact Framework version 3.5 SP1 with C#. I have a Controller class associated with each form for MVC implementation. Here is my sample Controller class. public class Controller { public void Init(Form f) { //f.Controls will allow access to all controls //How shall I access imagelist, timer on form f. } } My question is how can I access non visual components without taking a performance hit of reflection? Any code snippets are welcome. If reflection is only way, then can you provide me optimal way for components access please? Thanks,

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• Why does Generic class signature requires specifying new() if type T needs instantiation ?

  - by this. __curious_geek

  I'm writing a Generic class as following. public class Foo<T> : where T : Bar, new() { public void MethodInFoo() { T _t = new T(); } } As you can see the object(_t) of type T is instantiated at run-time. To support instantiation of generic type T, language forces me to put new() in the class signature. I'd agree to this if Bar is an abstract class but why does it need to be so if Bar standard non-abstract class with public parameter-less constructor. compiler prompts following message if new() is not found. Cannot create an instance of the variable type 'T' because it does not have the new() constraint

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• How do I "step over" jQuery code while debugging?

  - by Scott Rippey

  While stepping through a script that uses jQuery, I just want to test the code I wrote. I don't want to step into the jQuery file -- I'm not debugging jQuery, just my own file. Are there any ways to tell a debugger to not step into the jQuery file? I use Visual Studio + Internet Explorer, as well as Firefox + Firebug for stepping through code ... and both seem to love to step through dozens of jQuery statements. For example, say I have a script like this: $("div").each(function() { $(this).hide(); }); I would like to press "step into" and not see the implementation of ".each()" etc... In C#, this is possible by using the [DebuggerStepThrough()] attribute on a class. But that doesn't help with JavaScript.

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• Mapview on tablet: How can I center the map with an offset?

  - by Waza_Be

  Hint: Here is a similar post with HTML. In the current tablet implementation of my app, I have a fullscreen MapView with some informations displayed in a RelativeLayout on a left panel, like this: (My layout is quite trivial, and I guess there is no need to post it for readability) The problem comes when I want to center the map on a specific point... If I use this code: mapController.setCenter(point); I will of course get the point in the center of the screen and not in the center of the empty area. I have really no idea where I could start to turn the offset of the left panel into map coordinates... Thanks a lot for any help or suggestion

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• Can a parser tell the lexer to ignore a newline?

  - by chollida

  I'm writing a preprocessor for my language. In the preprocessor I've output a line that wasn't in the source file. This causes any error messages that Anltr creates to be incremented by one line. The Lexer handles the line count so I'm wondering if there is a way for the parser to tell the lexer to decrement the line count, or to ignore a specific newline. I'm also open to other suggestions on how to work around this. The only constraint I have is putting the extra line inline with the existing code. I'd prefer to keep it on it's own line to keep my parsing sane.

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• What is a good way for a custom accessory view in a UITableViewCell to message the table view contro

  - by Alex Gosselin

  Hi Everyone, I am working on adding a custom accessory view, (a button) to a UITableViewCell, and I need it to tell the table view when it is touched, but I can't figure out how to communicate to the table view what button was pressed. Ideally I'd like to somehow call a function like this: [controller tableView:view didSelectCustomButtonAtIndexPath:indexPath usingCell:self]; when my custom view button is pressed. Sorry if this is a bit vague, I'm not really sure how to explain this well. I am basically looking for how to mimic the implementation for tableView:didSelectRowAtIndexPath: without having to subclass UITableViewCell. Thanks for any help.

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• Creating methods with infinite overloads ? (.NET)

  - by MarceloRamires

  In C# you can do this: foo = string.Format("{0} {1} {2} {3} ...", "aa", "bb", "cc" ...); This method Format() accepts infinite parameters, being the first one how the string should be formatted and the rest are values to be put in the string. Today I've come to a situation where I had to get a set of strings and test them, then I remembered this language functionality, but I had no clue. After a few unsuccessful web searches, I've realised it would be more prudent to just get an array, which didn't make me quite satisfied. Q: How do I make a function that accepts infinite parameters? And how do I use it ?

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• Commonly use Utility methods in projects

  - by Newbie

  In many projects, we come across various utility methods, e.g. Email validation Convert from dd/mm/yyyy to mm/dd/yyyy or other date formats I would like to know as what are the varoius common utility method that we genrally use? I know that some methods are project specific but many will be common. I searched in net to get a list of as much as possible but none I found to be very informative. Could you please help? Well I am more interested in the method behaviour and not in their implementation. If I can get the method names and what it does e.g. ConvertMMDDYYYY to ConvertDDMMYYYY it will server my purpose. Thanks

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• Is the FoldLeft function available in R?

  - by JSmaga

  Hi, I would like to know if there is an implementation of the foldLeft function (and foldRight?) in R. The language is supposed to be "rather" functional oriented and hence I think there should be something like this, but I could not find it in the documentation. To me, foldLeft function applies on a list and has the following signature: foldLeft[B](z : B)(f : (B, A) => B) : B It is supposed to return the following result: f(... (f(f(z, a0), a1) ...), an) if the list is [a0, a1, ..., an]. (I use the definition of the Scala List API) Does anybody know if such a function exists in R?

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• Designing operation (a,b) -> (c,d)

  - by golergka

  I have an operation that I need to design. That operation takes two objects of a certain class X, and returns two new objects of the same class (I may need the originals later). The logic that dictates the selection of this object is contained in class Y. On one hand, I don't want class Y to know details about class X implementation; on the other, I don't want class X to know details about selecting the different objects to perform this operation on. If that was all the problem, I'd just create a static method on class A. However, the methods in language I'm working on return only one object. Also, the operation needs to be robust, and calling operation two times to get C and D respectively isn't possible, as both C & D both rely on a single random number. How should I design such operation? Update: I'm using Obejctive C.

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• How to edit files on the users file system from my web server?

  - by Abs

  Hello all, I am really looking for implementation advice as I have entered a new realm that I am not familiar with. At the simplest level, I would like to find a way that I can read/write to a users machine from my web server. For this to work, I think I will have to install some sort of "plugin" on the users machine which can receive (or poll?) the server for instructions. The above is the line of thought that I currently have, maybe using JAVA to do this. This needs to work on Linux, Mac and Windows OS. I am really looking for advice on the above, is it a good idea? Is there a better way of doing this? Is there something out there already that I can build on top of? I really appreciate all input and advice as this is something I have not done before. Thanks all

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• Multiplying numbers on horizontal, vertial, and diagonal lines

  - by untwisted

  I'm currently working on a project Euler problem (www.projecteuler.net) for fun but have hit a stumbling block. One of the problem provides a 20x20 grid of numbers and asks for the greatest product of 4 numbers on a straight line. This line can be either horizontal, vertical, or diagonal. Using a procedural language I'd have no problem solving this, but part of my motivation for doing these problems in the first place is to gain more experience and learn more Haskell. As of right now I'm reading in the grid and converting it to a list of list of ints, eg -- [[Int]]. This makes the horizontal multiplication trivial, and by transposing this grid the vertical also becomes trivial. The diagonal is what is giving me trouble. I've thought of a few ways where I could use explicit array slicing or indexing, to get a solution, but it seems overly complicated and hackey. I believe there is probably an elegant, functional solution here, and I'd love to hear what others can come up with.

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• How does OfType<T>() Work?

  - by TheCloudlessSky

  How does OfType() Work? I read this link about what's going on but how exactly does the LINQ provider know how to get all objects matching the specified type. I know the IQueryable<T> "chains" up requests and then evaluates when GetEnumerator() is called (right?). Specifically I want to know how does the framework quickly do type comparison? I wrote a method in a .NET 2.0 project that went like this (since 2.0 doesn't support these kind of features): public IEnumerable<TResult> OfType<TResult>() where TResult : class { foreach (TItem item in this.InnerList) { TResult matchItem = item as TResult; if (matchItem != null) { yield return matchItem; } } } Is this the best implementation?

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• How do i sort by: most viewed, most commented, most popular, best rating, etc?

  - by MrRioku

  Pretty basic question.. I kno.., I just don't know how its done. I see it everywhere. I want to be able to sort out my content in my websites by most viewed, most commented, most popular, best rating, etc...with a drop down list, check box, etc... but I don't know how "sort by" works? Which scripting language should it be written in? Javascript? PHP? Can it be done with XML? Do I have to have a database set up like MySQL? Is there a good tutorial anywhere that explains it? I need to be explained the exact process of how it works. As you can see I really need direction.. Your help is much appreciated :D

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• Calling R Script from within C-Code

  - by tiny81

  Hi, Is there a way to call an R-Script within C-Code? I did find the R Api for C (chaper 6. of the 'Writing R Extensions' manual), but as far as I understood this does "only" allow to call the C-Implementation of R. Of cause I could call the R-Script via shell, but that's no solution for me, since this does not allow proper passing of data (at least no if I don't what to write the data into a Csv-File or something like this). Is there a easy way of using the R to C parser beforehand? Any hints you can give me? regards, Tiny

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• Is void *p = 0L valid?

  - by Artefacto

  In this answer, sassman initializes a pointer with: zend_class_entry* ce = 0L; My question is – is this valid? I would say it isn't, to initialize the variable with a null pointer either an unadorned (and possibly casted to void *) 0 constant, or some macro that evaluates to that such as NULL should be used. However, I can't find definitive language in the standard that supports this interpretation. All it says is: An integer constant expression with the value 0, or such an expression cast to type void *, is called a null pointer constant.

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• Mapping C structure to an XML element

  - by EFraim

  Suppose I have a structure in C or C++, such as: struct ConfigurableElement { int ID; char* strName; long prop1; long prop2; ... }; I would like to load/save it to/from the following XML element: <ConfigurableElement ID="1" strName="namedElem" prop1="2" prop2="3" ... /> Such a mapping can be trivially done in Java/C# or any other language with run-time reflection for the matter. Can it be done in any non-tedious way in C++ with macros/template trickery? Bonus points for handling nested structures/unions.

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• Why people define class, trait, object inside another object in Scala?

  - by Zwcat

  Ok, I'll explain why I ask this question. I begin to read Lift 2.2 source code these days. In Lift, I found that, define inner class and inner trait are very heavily used. object Menu has 2 inner traits and 4 inner classes. object Loc has 18 inner classes, 5 inner traits, 7 inner objects. There're tons of codes write like this. I wanna to know why the author write it like this. Is it because it's the author's personal taste or a powerful use of language feature?

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• Change Modul popup every 30 sec Javascript

  - by SoftwareDeveloper

  I have a div id called modalpage and have css. I need a javascript function which can dynamically shows popup for 20 mins and change in every 30 secs right now i have the following javascript function. Can anybody help me please <script language="javascript" type="text/javascript"> function revealModal(divID) { window.onscroll = function () { document.getElementById(divID).style.top = document.body.scrollTop; }; document.getElementById(divID).style.display = "block"; document.getElementById(divID).style.top = document.body.scrollTop; } which is called by a input id button. <input id="Button1" type="button" value="Click here" onclick="revealModal('modalPage')" /> Thanks

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