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• Java - how to tell class of an object?

  - by lkm

  Given a method that accepts as a parameter a certain supertype. Is there any way, within that method, to determine the actual class of the object that was passed to it? I.e. if a subtype of the allowable parameter was actually passed, is there a way to find out which type it is? If this isn't possible can someone explain why not (from a language design perspective)? Thanks Update: just to make sure I was clear void doSomething(MyType myType) { //determine if myType is MyType OR one of its subclasses } Since the method signature specifies the parameter as being MyType, then how can one tell if the object is actually a subtype of MyType (and which one).

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• Php/ODBC encoding problem

  - by JohnM2

  I use ODBC to connect to SQL Server from PHP. In PHP I read some string (nvarchar column) data from SQL Server and then want to insert it to mysql database. When I try to insert such value to mysql database table I get this mysql error: Incorrect string value: '\xB3\xB9ow...' for column 'name' at row 1 For string with all ASCII characters everything is fine, the problem occurs when non-ASCII characters (from some European languages) exist. So, in more general terms: there is a Unicode string in MS SQL Server database, which is retrieved by PHP trough ODBC. Then it is put in sql insert query (as value for utf-8 varchar column) which is executed for mysql database. Can someone explain to me what is happening in this situation in terms of encoding? At which step what character encoding convertions may take place? I use: PHP 5.2.5, MySQL5.0.45-community-nt, MS Sql Server 2005.

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• Assigning a variable of a struct that contains an instance of a class to another variable

  - by xport

  In my understanding, assigning a variable of a struct to another variable of the same type will make a copy. But this rule seems broken as shown on the following figure. Could you explain why this happened? using System; namespace ReferenceInValue { class Inner { public int data; public Inner(int data) { this.data = data; } } struct Outer { public Inner inner; public Outer(int data) { this.inner = new Inner(data); } } class Program { static void Main(string[] args) { Outer p1 = new Outer(1); Outer p2 = p1; Console.WriteLine("p1:{0}, p2:{1}", p1.inner.data, p2.inner.data); p1.inner.data = 2; Console.WriteLine("p1:{0}, p2:{1}", p1.inner.data, p2.inner.data); p2.inner.data = 3; Console.WriteLine("p1:{0}, p2:{1}", p1.inner.data, p2.inner.data); Console.ReadKey(); } } }

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• Jquery draggable with zoom problem

  - by Manuel

  I am working on a page in witch all its contents are scaled by using zoom. The problem is that when I drag something in the page the dragging item gets a bad position that seems relative to the zoom amount. To solve this I tried to do some math on the position of the draggable component, but seems that even tho visually its corrected, the "true" position its not recalculated. here is some code to explain better: var zoom = Math.round((parseFloat($("body").css("zoom")) / 100)*10)/10; var x = $(this).data('draggable').position; $(this).data('draggable').position.left = Math.round(x.left/zoom); $(this).data('draggable').position.top = Math.round(x.top/zoom); Any help would be greatly appreciated

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• Question About Abstract Classes?

  - by IbrarMumtaz

  URL: Link (1) According to this wesbite .. you cannot implement Abstract classes but derive from them. This makes sense and I have read this many times. Like an interface, you cannot implement an instance of an abstract class, however you can implement methods, fields, and properties in the abstract class that can be used by the child class. But on MSDN URL: TextWriter CLass on MSDN TextWriter is an abstract class but it has two constructors defined ... and according to the MS 70-536 book, the following statement is valid: TextWriter tw = new File.CreateText("myFile.Txt") The static file class and it's CreateText method is fine by me as I have studied it on MSDN but can somebody explain this little contradiction I have found? Surely I am not the first? Why is instantaion of base abstract classes possible????

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• Kernel thread exit in linux

  - by Raffo

  Hi guys, I'm here to ask you the difference between a process and a thread in linux. I know that a thread for linux is just a "task", which shares with the father process things that they need to have in common (the address space and other important informations). I also know that the two are creating calling the same function ('clone()'), but there's still something that I'm missing: what really happens when a thread exit? What function is called inside the linux kernel? I know that when a process exits calls the do_exit function, but here or somewhere else there should be a way to understand if it is just a thread exiting or a whole process. Can you explain me this thing or redirect to some textbook?? I tried 'Understanding the linux kernel' but I was not satisfied with it. I'm asking this thing because a need to add things to the task_struct struct, but I need to discriminate how to manage those informations for a process and its children. Thank you.

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• Javascript array length incorrect on array of objects

  - by Serenti

  Could someone explain this (strange) behavior? Why is the length in the first example 3 and not 2, and most importantly, why is the length in the second example 0? As long as the keys are numerical, length works. When they are not, length is 0. How can I get the correct length from the second example? Thank you. a = []; a["1"] = {"string1":"string","string2":"string"}; a["2"] = {"string1":"string","string2":"string"}; alert(a.length); // returns 3 b = []; b["key1"] = {"string1":"string","string2":"string"}; b["key2"] = {"string1":"string","string2":"string"}; alert(b.length); // returns 0

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• Installing XAMPP in Amazon EC2

  - by Woho87

  Hi! Can someone explain to me(not a rocket scientist) all the steps for installing XAMPP for a EC2 instance running Linux? And yes I have look the entire web and found nothing, except this "Deploying a lamp stack" and this "Starting Amazon EC2 with Mac OS X". I found the latter one more useful, but as a said I'm not a rocket scientist. I got stuck in to the latter link where I should edit the file .bash_profile with a text editor. I tried the "vi" in SSH, but why can't I open it on textEditor included in all Macs? Is there any easier way to setting up a XAMPP server for a linux server in EC2?

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• access models and forms within modules

  - by sims

  Hi Stackers, What is the best way to access my models and forms from a controller of a module? Let's explain with "pictures": /application/module/storage/controllers/IndexController.php needs to call readAction in the class called storage_Model_Files in /application/module/storage/models/Files.php I've made this app's dir structure and these forms and models with zf.sh (Zend_Tool). I've read about all sorts of ways of manually including these files. I want to lazy load them much like everything is done automatically with the default module. I can't seem to find how in the docs. Does that make sense? I have: resources.frontController.moduleDirectory = APPLICATION_PATH "/modules" in my application.ini file. So I can access my controllers fine. Thanks for your help!

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• Confused by this PHP Exception try..catch nesting

  - by Domenic

  Hello. I'm confused by the following code: class MyException extends Exception {} class AnotherException extends MyException {} class Foo { public function something() { print "throwing AnotherException\n"; throw new AnotherException(); } public function somethingElse() { print "throwing MyException\n"; throw new MyException(); } } $a = new Foo(); try { try { $a->something(); } catch(AnotherException $e) { print "caught AnotherException\n"; $a->somethingElse(); } catch(MyException $e) { print "caught MyException\n"; } } catch(Exception $e) { print "caught Exception\n"; } I would expect this to output: throwing AnotherException caught AnotherException throwing MyException caught MyException But instead it outputs: throwing AnotherException caught AnotherException throwing MyException caught Exception Could anyone explain why it "skips over" catch(MyException $e) ? Thanks.

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• How Does Differential Execution Work?

  - by Brian

  I've seen a few mentions of this on SO, but staring at Wikipedia and at an MFC dynamic dialog demo did nothing to enlighten me. Can someone please explain this? Learning a fundamentally different concept sounds nice. Edit: I think I'm getting a better feel for it. I guess I just didn't look at the source code carefully enough the first time. I have mixed feelings about DE at this point. On the one hand, it can make certain tasks considerably easier. On the other hand, getting it up and running (i.e. setting it up in your language of choice) is not easy (I'm sure it would be if I understood it better)...though I guess the toolbox for it need only be made once, then expanded as necessary. I think in order to really understand it, I'll probably need to try implimenting it in another language.

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• Difference between static const char* and const char*.

  - by Will MacDonagh

  Could someone please explain the difference in how the 2 snippets of code are handled below? They definitely compile to different assembly code, but I'm trying to understand how the code might act differently. I understand that string literals are thrown into read only memory and are effectively static, but how does that differ from the explicit static below? struct Obj1 { void Foo() { const char* str( "hello" ); } }; and struct Obj2 { void Bar() { static const char* str( "hello" ); } };

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• socket programming: How do I handle out of band data

  - by soulmerge

  I just looked into wikipedia's entry on out-of-band data and as far as I understand, OOB data is somehow flagged more important and treated as ordinary data, but transmitted in a seperate stream, which profoundly confuses me. The actual question would be (besides "Could someone explain what OOB data is?"): I'm writing a unix application that uses sockets and need to make use of select() and was wondering what to do with the exceptfds parameter? Do I need to put all my sockets into this parameter and react to such events? Or do I just ignore them?

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• How to use JarOutputStream to create a JAR file?

  - by Gili

  How does one create a JAR file programmatically using java.util.jar.JarOutputStream? The JAR file produced by my program looks correct (it extracts fine) but when I try loading a library from it Java complains that it cannot find files which are clearly stored inside it. If I extract the JAR file and use Sun's jar command-line tool to re-compress it the resulting library works fine. In short, something is wrong with my JAR file. Please explain how to create a JAR file programmatically, complete with a manifest file.

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• Converting ASP.NET MVC to n-Tiered Architecture

  - by Jeff

  I just built an application using ASP.NET MVC. The programmers at my company want to build all future modules using n-Tiered (Presentation Layer, Business Logic Layer, Data Access Layer) architecture. I am not the programmer and need to know why this makes sense? Do I have to completely rewrite the entire code or can it be converted? We are building an HRIS system with Business Intelligence. Somebody please explain why or why not this approach does or does not make sense.

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• asp.net mvc default model binding problem

  - by csetzkorn

  I have some problems with ASP.NET MVC’s default model binder. The View contains HTML like this: <input name="SubDTO[0].Id" value="1" type="checkbox"> <input name="SubDTO[1].Id" value="2" type="checkbox"> This is my simplified ‘model’: public class SubDTO { public virtual string Id { get; set; } } public class DTO { public List<SubDTO> SubDTOs { get; set; } public DTO() { SubDTOs = new List< SubDTO>(); } } All this works fine if the user selects at least the first checkbox (SubDTO[0].Id). The controller ‘receives’ a nicely initialised/bound DTO. However, if the first check box is not selected but only, for example, SubDTO[1].Id the object SubDTOs is null. Can someone please explain this ‘strange’ behaviour and how to overcome it? Thanks. Best wishes, Christian

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• SQL SELECT with time range

  - by nLL

  Hi, I have below click_log table logging hits for some urls site ip ua direction hit_time ----------------------------------------------------- 1 127.0.0.1 1 20010/01/01 00:00:00 2 127.0.0.1 1 20010/01/01 00:01:00 3 127.0.0.1 0 20010/01/01 00:10:00 .... ......... I want to select incoming hits (direction:1) and group by sites that are: from same ip and browser logged within 10 minutes of each other occured more than 4 times in 10 minutes. I'm not sure if above was clear enough. English is not my first language. Let me try to explain with an example. If site 1 gets 5 hits from same ip and browser with in 10 minutes after getting first unique hit from that ip and browser i want it to be included in the selection. Basically I am trying to find abusers.

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• Create DataGridView columns from Table values

  - by fireBand

  Hi, I am using data grid view to display items as excel spread sheet in VB.NET. I got a table named CostTypes with column names [CostTypeID, CostType] and values [1,External] and [2,Internal] (These are constant but more values can be added to table). I want to create columns with names of the values[External , Internal] in DataGridView. If I use databiding directly I get columns [CostTypeID,CostType] which is not what I am looking for. If some one could explain how to create columns at runtime in datagridview or how to retrieve data from data base using LINQ so that [External , Internal] turn out to be columns that would be great. Thanks in advance.

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• Integers in JavaScript

  - by muntoo

  I'm a beginner to Javascript so forgive me if I sound dumb because I learned some Javascript from W3Fools (which are really difficult tutorials - they don't explain anything I want to know, but everything I probably can guess from my experience with C++). I may be switching over to MDN, but if you can recommend any other tutorials, that be great. Anyways, so here's my question: I just read a few lines of this, and apparently: Numbers in JavaScript are "double-precision 64-bit format IEEE 754 values", according to the spec. This has some interesting consequences. There's no such thing as an integer in JavaScript, so you have to be a little careful with your arithmetic if you're used to math in C or Java. I've already seen that there are few of the data types (for variables) I'm used to from C++. But I didn't expect all numbers to automatically be floats. Isn't there any way to use integers, not float? Will a future version of JavaScript support ints?

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• How do i create a nice looking image fadein onload with mootools?

  - by woobione

  Hi everyone! I´m creating a website for a photographer who would like a fine fadein on his images. I have excluded flash as a solution and would like to use those fine-looking effects of mootools fx. But the problem is that I'm really lousy when it comes to javascript. So if anyone could give me an easy solution for fading in one single image onload and when the image is loaded I would be really happy. I know there is a lot of different people out there who have this. But the problem is that i don't know how the code works even if it is a complete solution. So most important. If anyone has got the time to explain what every single line of code does i would be more than grateful. Thanks!

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• reinitialize an object with self.__init__(...)

  - by Kara Jevo

  Could anybody explain whether it is safe to reinitialize an object by calling "self.init(". as shown in the following simplified example? The reason i'm asking is that i couldn't find this method neither in several python books nor in internet. There are some who suggest to list all attributes and set them to initial value one by one. Basically i want to set my object to initial state after it has finished some tasks. class Book(object): def __init__(self,name,author): self.name = name self.author = author self.copies = 5 def reset(self): self.__init__(self.name,self.author) def incrementCopy(self): self.copies += 1 Kite = Book('kite runner','khaled hosseini') print 'initial number of copies:', Kite.copies Kite.incrementCopy() Kite.incrementCopy() Kite.incrementCopy() print '3 copies are added:', Kite.copies Kite.reset() print 'number of copies are reinitialized', Kite.copies initial number of copies: 5 3 copies are added: 8 number of copies are reinitialized 5

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• Multi-Threaded Application - Help with some pseudo code!!

  - by HonorGod

  I am working on a multi-threaded application and need help with some pseudo-code. To make it simpler for implementation I will try to explain that in simple terms / test case. Here is the scenario - I have an array list of strings (say 100 strings) I have a Reader Class that reads the strings and passes them to a Writer Class that prints the strings to the console. Right now this runs in a Single Thread Model. I wanted to make this multi-threaded but with the following features - Ability to set MAX_READERS Ability to set MAX_WRITERS Ability to set BATCH_SIZE So basically the code should instantiate those many Readers and Writers and do the work in parallel. Any pseudo code will really be helpful to keep me going!

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• Buttons, hover, text and transitions on pure css3

  - by Mascote Ricardo

  I bought a responsive html5 template to create a website for my band. But I miss a page of tour dates, and would create a unique content, simple and quick to load on any device. I have the idea ready, something like buttons (months) to change on hover and when clicked, shows the dates and cities, all with transitions and fadein / fadeout. (pure css3) to better explain and make me understand, follows an image I created in photoshop. http://img51.imageshack.us/img51/1542/l17u.jpg can someone give me a help, idea or tag to search the web, I thank you too!

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• Why are difference lists more efficient than regular concatenation?

  - by Craig Innes

  I am currently working my way through the Learn you a haskell book online, and have come to a chapter where the author is explaining that some list concatenations can be ineffiecient: For example ((((a ++ b) ++ c) ++ d) ++ e) ++ f Is supposedly inefficient. The solution the author comes up with is to use 'difference lists' defined as newtype DiffList a = DiffList {getDiffList :: [a] -> [a] } instance Monoid (DiffList a) where mempty = DiffList (\xs -> [] ++ xs) (DiffList f) `mappend` (DiffList g) = DiffList (\xs -> f (g xs)) I am struggling to understand why DiffList is more computationally efficient than a simple concatenation in some cases. Could someone explain to me in simple terms why the above example is so inefficient, and in what way the DiffList solves this problem?

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• Extracting rightmost N bits of an integer

  - by srandpersonia

  In the yester Code Jam Qualification round http://code.google.com/codejam/contest/dashboard?c=433101#s=a&a=0 , there was a problem called Snapper Chain. From the contest analysis I came to know the problem requires bit twiddling stuff like extracting the rightmost N bits of an integer and checking if they all are 1. I saw a contestant's(Eireksten) code which performed the said operation like below: (((K&(1<<N)-1))==(1<<N)-1) I couldn't understand how this works. What is the use of -1 there in the comparison?. If somebody can explain this, it would be very much useful for us rookies. Also, Any tips on identifying this sort of problems would be much appreciated. I used a naive algorithm to solve this problem and ended up solving only the smaller data set.(It took heck of a time to compile the larger data set which is required to be submitted within 8 minutes.). Thanks in advance.

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