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  • Why System.String's beahaves like a value type?

    - by Sorush Rabiee
    I want to write a 'Date' class that behaves like a Value Type. for example, Instead of writing a Clone method for setting properties safely, make the Date class to pass by value: public Date Birthday { get { return this.birthday; } set { this.birthday = value.Clone(); } //I want to write this.birthday = value; //without changing external value when this.Birthday changes } I know this is possible because System.String is a class and behaves like a value. for example: String s1 = "Hello"; String s2 = "Hi"; s1 = s2; s2="Hello"; Console.WriteLine(s1); //Prints 'Hi' First I thought writers of this class override '=' operator, but now I know that the '=' operator can not be overridden. so how they write String class?

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  • why are javascript functions like this

    - by Kajal
    I am a starter to javascript. I know to write JS userdefined functions. But recently I came across some thing that I can’t recognize. Can anyone explain to me what this is? (function( window, undefined ) { var jQuery = (function() { }); window.jQuery = window.$ = jQuery; })(window); What is the meaning of this? When I Google javascript functions I am getting only function foo(){ alert("This is an alert"); } I know to use these type of functions

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  • I just don't get why there is a glMatrixMode in OpenGL

    - by René Nyffenegger
    I just don't understand what OpenGL's glMatrixMode is for. As far as I can see, when glMatrixMode(GL_MODELVIEW) is called, it is followed by glVertex, glTranslate, glRotate and the like, that is, OpenGL commands that place some objects somewhere in the space. On the other hand, if glOrtho or glFrustum or gluProjection is called (ie how the placed objects are rendered), it has a preceeding call of glMatrixMode(GL_PROJECTION). I guess what I have written so far is an assumption on which someone will prove me wrong, but is not the point of using different *Matrix Mode*s exactly because there are different kinds of gl-functions: those concerned with placing objects and those with how the objects are rendered? So, if someone could shed some light on this issue, I'd certainly appreciate it.

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  • why can't you use the debug/release version of a lib interchangeably

    - by user205834
    In C++, most of the libs come in Debug/Release versions. Question 1. What are the big difference between Debug and Release versions (e.g. what advantages do you have using one versus the other). Question 2. A lib is just has an implementation of the functions, how does a function implementation change if you are using debug/release versions? Question 3. Can you ever build your app in debug mode and use a release version of a lib? Thanks.

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  • SQL Server: Why use shorter VARCHAR(n) fields?

    - by chryss
    It is frequently advised to choose database field sizes to be as narrow as possible. I am wondering to what degree this applies to SQL Server 2005 VARCHAR columns: Storing 10-letter English words in a VARCHAR(255) field will not take up more storage than in a VARCHAR(10) field. Are there other reasons to restrict the size of VARCHAR fields to stick as closely as possible to the size of the data? I'm thinking of Performance: Is there an advantage to using a smaller n when selecting, filtering and sorting on the data? Memory, including on the application side (C++)? Style/validation: How important do you consider restricting colunm size to force non-sensical data imports to fail (such as 200-character surnames)? Anything else? Background: I help data integrators with the design of data flows into a database-backed system. They have to use an API that restricts their choice of data types. For character data, only VARCHAR(n) with n <= 255 is available; CHAR, NCHAR, NVARCHAR and TEXT are not. We're trying to lay down some "good practices" rules, and the question has come up if there is a real detriment to using VARCHAR(255) even for data where real maximum sizes will never exceed 30 bytes or so. Typical data volumes for one table are 1-10 Mio records with up to 150 attributes. Query performance (SELECT, with frequently extensive WHERE clauses) and application-side retrieval performance are paramount.

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  • Why I cannot call setSomething()?

    - by badgirl
    Hello. I dont know how to acces my method of my class ProjectNode, that is returned from ExplorerManager mgr like this: mgr.getRootContext().setSomething() getRootContext() returns Node object, but I put class ProjectNode (extends AbstractNode, abstractNode extends Node)into rootContext. The compiler does not want to eat that line of code. But it must!

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  • Why does this PHP program not work?

    - by oncode
    I'm new to PHP and was learning about PHP functions from w3schools. It said PHP allows a function call to be made when the function name is in a variable: This program worked <?php $v = "var_dump"; $v('foo'); ?> But this program did not work: <?php $v = "echo"; $v('foo'); ?> But if I do echo('foo'); it works. What am I doing wrong?

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  • why does twitter use the !function syntax in their embed code

    - by samccone
    I was looking at twitters embed code and saw that they are using !function ... while i know that this evaluates to false I was wondering what the point of it was. thoughts? !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs");

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  • Why closed contours are guaranteed here?

    - by user198729
    Quoted from here: BW = edge(I,'zerocross',thresh,h) specifies the zero-cross method, using the filter h. thresh is the sensitivity threshold; if the argument is empty ([]), edge chooses the sensitivity threshold automatically. If you specify a threshold of 0, the output image has closed contours, because it includes all the zero crossings in the input image. I don't understand it,can someone elaborate?

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  • Why my reputation goes down.

    - by Incognito
    I know there was a recalculation and I know how to track the reputation, but seems it not helps. My reputation was about 495 just several hours ago and now it goes down to 295. I have checked there were no down votes. What can be the issue?

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  • Why isn't this button firing the anchor tag?

    - by Noor
    My idea is to press a button that takes me to a web page. I've created a thing that dynamically creates a button and an anchor tag. When the button is clicked, I want it to "click"/fire up the anchor tag.. I've uploaded a demo to my site, when you try it out just leave everything as it is. Click the first button then the add button right away.. then try to click the dynamically created button. Nothing happens, but if you watch the source you can find an anchor tag with the ID FL1000, I've set it up so that the anchor tag gets the ID from the value of the created button + 1000 just incase I need to use that ID.. Thanks guys... edit: this is optimized for google chrome, haven't tried it out with other browser.

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  • [GCC, linking] How to link app with static library + why this is not working

    - by user278799
    I have a problem. I wrote example code and I want to build it without the error: main.cpp.text+0x5): undefined reference to `test()' Library test1.c #include <stdlib.h> void test() { puts("Dziala"); } test1.h #ifndef TEST1_H #define TEST1_H extern void test(); #endif makefile all: gcc -c ./src/test1.c -o ./lib/test1.o ar rcs ./lib/libtest1.a ./lib/test1.o Program main.cpp #include <test1.h> int main() { test(); return 0; } makefile all: g++ -static -I../test1/include -L../test1/lib ./src/main.cpp -o ./build/MyApp -ltest1 What am I doing wrong?

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  • Why isn't div centering?

    - by user2898276
    I'm trying to centre a logo in the middle of the browser. I have this so far... <script type="text/javascript"> $(document).ready(function(){ $(window).resize(function(){ $('#theLogo').css({ position:'absolute', left: ($(window).width() - $('#theLogo').outerWidth())/2, top: ($(window).height() - $('#theLogo').outerHeight())/2 }); }); $(window).resize(); }); HTML <div id="theLogo"> <section id="responsiveLogo" class="logo">September</section> </div> I'm trying to centre this bit: <section id="responsiveLogo" class="logo">September</section> Live version here

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  • why won't background change in firefox but it will in ie

    - by rod
    <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server"> <title></title> <link id="csslink" href="Handler.ashx" rel="stylesheet" type="text/css" /> </head> <body> <form id="form1" runat="server"> <div> <input id="Button1" type="button" value="Blue" /> <input id="Button2" type="button" value="Red" /> </div> </form> <script type="text/javascript"> var pageDefault = { btn1: document.getElementById('Button1'), btn2: document.getElementById('Button2'), csslink: document.getElementById('csslink'), init: function() { this.btn1.onclick = function() { pageDefault.csslink.href = "Handler.ashx?id=1"; } this.btn2.onclick = function() { pageDefault.csslink.href = "Handler.ashx?id=2"; } } } pageDefault.init(); </script> </body> </html> Here's the ashx ProcessRequest public void ProcessRequest(HttpContext context) { context.Response.ContentType = "text/plain"; var id = context.Request.QueryString["id"]; if (id == "1") { context.Response.Write(@" body { background: Blue; } "); } else if (id == "2") { context.Response.Write(@" body { background: Red; } "); } else { } }

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  • There's @interface in my @implementation — why is that?

    - by Mark McDonald
    This is a pretty noobish question – I'm looking at some Cocoa sample code and there's @interface blocks in the .m files as well as the headers. For instance, in the AppDelegate class header, a UIWindow and UI navigation are defined as instance variables, but the @property declarations are actually made in the implementation file. Is there a functional reason for this, is it a stylistic choice, or… ?

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  • Why doesn't this work?

    - by Kyle W
    take = raw_input('Please enter the string of numbers that compose code\n\n\t') y = str(take) l = [] for i in xrange(0, len(y), 3):         l.append(str(y[i:i+3])) b = len(l) a = 0 while(a!=b):         c = l[a].replace('444', ' ')         c = l[a].replace('111', 'a')         c = l[a].replace('112', 'b')         c = l[a].replace('113', 'c')         c = l[a].replace('114', 'd')         c = l[a].replace('115', 'e')         etc...         a = a + 1 filename = 'decmes.txt' file = open(filename, 'w') file.write(c) file.close() I can enter anything, just 111 for example and it gives me back the same thing I put in. Maybe it's something dumb, but I can't figure it out.

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  • Why do I have to use the "origin" for the pull to be successfull

    - by yan bellavance
    when I do : git pull BranchName it tells me everything is up to date but I know that is not true. When I do: git pull origin BranchName then I get the files I was expecting. Is there an easy way to answer this or do I need to provide more details. PS One thing I did do just to understant themechanics of git is give the branch name in my cloned repo a different name than on the remote repo. I did however put the right name in the config file like so: [branch "myUDPspinoff"] remote = origin merge = refs/heads/UDPspinoff this worked before on another repo but not this one. And when I put everything in the same name thenI did not need to use origin anymore.

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  • Why do I get a Null Pointer Exception?

    - by Roman
    I have this code: Manager manager = new Manager("Name"); MyWindowListener windowListener = new MyWindowListener(); manager.addWindowListener(windowListener); Eclipse writes that I have a NullPointerException in the last line. What can be the reason for that. I do have constructors in the Manager and MyWindowListener. If it's important MyWindowListener implements WindowListener.

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  • why this condition not work

    - by migo
    *strong text*I noticed that the first condition does not work if (empty($ss)) { echo "please write your search words"; } but the second work else if ($num < 1 ) { echo "not found any like "; full code if (empty($ss)) { echo "please write your search words"; } else if ($num < 1 ) { echo "not found any like "; }else { $sql=("SELECT * FROM student WHERE snum = $ss "); $rs = mysql_query($sql) or die(mysql_error()); while($data=mysql_fetch_array($rs)){ ? ??????? ????? ????? ???? ???? ?????? 100 100 100 100 100 ?????? ???????? ????? ?????? ????? ??????? ?????? ??????? } }; ?

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  • Why are my thread being terminated ?

    - by Sephy
    Hi, I'm trying to repeat calls to methods through 3 differents threads. But after I start my threads, during the next iteration of my loop, they are all terminated so nothing is executed... The code is as follows : public static void main(String[] args) { main = new Main(); pollingThread.start(); } static Thread pollingThread = new Thread() { @Override public void run() { while (isRunning) { main.poll(); // test the state of the threads try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } } }; }; public void poll() { if (clientThread == null) { clientThread = new Thread(new Runnable() { @Override public void run() { //create some objects } }); clientThread.start(); } else if (clientThread.isAlive()) { // do some treatment } if (gestionnaireThread == null) { gestionnaireThread = new Thread(new Runnable() { @Override public void run() { //create some objects }; }); gestionnaireThread.start(); } else if (gestionnaireThread.isAlive()) { // do some treatment } if (marchandThread == null) { marchandThread = new Thread(new Runnable() { @Override public void run() { // create some objects }; }); marchandThread.start(); } else if (marchandThread.isAlive()) { // do some treatment } } And for some reason, when I test the state of my different threads, they appear as runnable and then a the 2nd iteration, they are all terminated... What am I doing wrong? I actually have no error, but the threads are terminated and so my loop keeps looping and telling me the threads are terminated.... Thanks for any help.

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  • Why does java.util.concurrent.ArrayBlockingQueue use 'while' loops instead of 'if' around calls to

    - by theFunkyEngineer
    I have been playing with my own version of this, using 'if', and all seems to be working fine. Of course this will break down horribly if signalAll() is used instead of signal(), but if only one thread at a time is notified, how can this go wrong? Their code here - check out the put() and take() methods; a simpler and more-to-the-point implementation can be seen at the top of the JavaDoc for Condition. Relevant portion of my implementation below. public Object get() { lock.lock(); try { if( items.size() < 1 ) hasItems.await(); Object poppedValue = items.getLast(); items.removeLast(); hasSpace.signal(); return poppedValue; } catch (InterruptedException e) { e.printStackTrace(); return null; } finally { lock.unlock(); } } public void put(Object item) { lock.lock(); try { if( items.size() >= capacity ) hasSpace.await(); items.addFirst(item); hasItems.signal(); return; } catch (InterruptedException e) { e.printStackTrace(); } finally { lock.unlock(); } } P.S. I know that generally, particularly in lib classes like this, one should let the exceptions percolate up.

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