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  • Why is the 'this' keyword not a reference type in C++ [closed]

    - by Dave Tapley
    Possible Duplicates: Why ‘this’ is a pointer and not a reference? SAFE Pointer to a pointer (well reference to a reference) in C# The this keyword in C++ gets a pointer to the object I currently am. My question is why is the type of this a pointer type and not a reference type. Are there any conditions under which the this keyword would be NULL? My immediate thought would be in a static function, but Visual C++ at least is smart enough to spot this and report static member functions do not have 'this' pointers. Is this in the standard?

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  • Why is unit testing needed in iPhone / iPad ?

    - by Madhup
    Hi, I am developing an application for iPad application. I need to perform unit testing in the application. But I am not sure why I should do unit testing in this application. The applications in these environments are rather small for unit testing to be written. And since the iPhone sentestingkit is not well documented the implementation and wriiting test cases is so time consuming. So why should we waste time in this? And if we have to what should be the best approach to write test cases? Thanks, Madhup

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  • JavaScript: why `null == 0` is false?

    - by lemonedo
    I had to write a routine that increments the value of a variable by 1 if it is a number, or assigns 0 to the variable if it is not a number. The variable can be incremented by the expression, or be assigned null. No other write access to the variable is allowed. So, the variable can be in three states: it is 0, a positive integer, or null. My first implementation was: v >= 0 ? v += 1 : v = 0 (Yes, I admit that v === null ? v = 0 : v += 1 is the exact solution, but I wanted to be concise then.) It failed since null >= 0 is true. I was confused, since if a value is not a number, an numeric expression involving it must be false always. Then I found that null is like 0, since null + 1 == 1, 1 / null == Infinity, Math.pow(2.718281828, null) == 1, ... Strangely enough, however, null == 0 is evaluated to false. I guess null is the only value that makes the following expression false: (v == 0) === (v >= 0 && v <= 0) So why null is so special in JavaScript?

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  • Why does Firefox + My code Destroys FireFox refresh

    - by acidzombie24
    I am soo angry right now. I lost hours and i dont know why this happens. Its a semi rant but i'll try to keep it short My code would not work, even after refreshing it was broken I fixed my code or so i thought because it stops working without me changing anything (you would think i am imagining this...) I somehow decide to make a new window or tab i run my code and verifies it works. I write more code and see everything is broken again I write test in a new window and see my code does work I see my code doesnt work and firebug DOES NOT HELP I notice when i create a new tab everything works I realize refreshing does not work and i MUST make a new tab for my code to work. Then i knew instantly what the problem was. I modify a display:none textbox but i set the values incorrectly. I cant see it because it is hidden. Now some of you might say its my fault because when doing a refresh all of the data may be cache. But here is the kicker. I was using POST data. I posted in between of the refresh each and everytime. Whats the point of using POST when the same data is cached and use anyways? If theres no chance for a search engine to follow a block user get link then why should i bother making anything post when security or repeat actions are not an issue? POST didnt seem to do anything.

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  • Why this works (Templates, SFINAE). C++

    - by atch
    Hi guys, reffering to yesterday's post, this woke me up this morning. Why this actually works? As long as the fnc test is concerned this fnc has no body so how can perform anything? Why and how this works? I'm REALLY interested to see your answers. template<typename T> class IsClassT { private: typedef char One; typedef struct { char a[2]; } Two; template<typename C> static One test(int C::*); //NO BODY HERE template<typename C> static Two test(…); //NOR HERE public: enum { Yes = sizeof(IsClassT<T>::test<T>(0)) == 1 }; enum { No = !Yes }; }; Thanks in advance with help to understand this very interesting fenomena.

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  • Why DataTable not showing the NULL values?

    - by thevan
    I have one DataTable Which I gets from the BackEnd. But When I fix the BreakPoint and Visualize the DataTable, It does not show the NULL values. Why is it so? In the BackEnd, My Table looks like below: CustID JobID Qty ---------- -------- ------ 1 NULL 100 2 1 200 But in the FrontEnd, My DataTable looks like below: CustID JobID Qty ---------- -------- ------ 1 100 2 1 200 Why it is not showing the NULL Values? Is there any specific reason? How to show the DataTable as it is like in the BackEnd?

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  • Why is my JavaScript function "a" not defined?

    - by 4l3x
    When I call my JavaScript function B, the javascript console in firefox said that function A is not defined, but on chrome browser if defined. And when I call function "A" in body segment: <input type="button" onclick="A()" value=" ..A.. "> , firefox said that function B is not defined? :S <html> <head> <script language="javascript" type="text/javascript"> function B(){ alert(" hi B "); document.write('<br><br><input type="button" onClick="A()" value=" ..A..">'); }; function A(){ alert(" hi A"); document.write('<br><br><input type="button" onclick="B()" value=" ..b..">'); if (window.WebCL == undefined) { alert("Unfortunately your system does not support WebCL. "); return false; } } </script> </head> <body> <input type="button" onclick="B()" value=" ..B.. "> </body> </html>

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  • why Observable snapshot observer vector

    - by han14466
    In Observable's notifyObservers method, why does the coder use arrLocal = obs.toArray();? Why does not coder iterate vector directly? Thanks public void notifyObservers(Object arg) { Object[] arrLocal; synchronized (this) { /* We don't want the Observer doing callbacks into * arbitrary code while holding its own Monitor. * The code where we extract each Observable from * the Vector and store the state of the Observer * needs synchronization, but notifying observers * does not (should not). The worst result of any * potential race-condition here is that: * 1) a newly-added Observer will miss a * notification in progress * 2) a recently unregistered Observer will be * wrongly notified when it doesn't care */ if (!changed) return; arrLocal = obs.toArray(); clearChanged(); } for (int i = arrLocal.length-1; i>=0; i--) ((Observer)arrLocal[i]).update(this, arg); }

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  • Why is forwarding variadic parameters invalid?

    - by awesomeyi
    Consider the variadic function parameter: func foo(bar:Int...) -> () { } Here foo can accept multiple arguments, eg foo(5,4). I am curious about the type of Int... and its supported operations. For example, why is this invalid? func foo2(bar2:Int...) -> () { foo(bar2); } Gives a error: Could not find an overload for '_conversion' that accepts the supplied arguments Why is forwarding variadic parameters invalid? What is the "conversion" the compiler is complaining about?

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  • Why does AddMilliseconds round the double paramater?

    - by fearofawhackplanet
    DateTime.Now.AddMilliseconds(1.5); // adds 2 milliseconds What on earth were they thinking here? It strikes me as horrendously bad practice to create a method that takes a double if it doesn't handle fractional values. Why didn't they implement this with a call to AddTicks and handle the fraction properly? Or at least take an int, so it's transparent to callers? I'm guessing there must be a good reason why they implemented it this way, but I can't think of what it could be. Can anyone offer any insight?

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  • Why can I derived from a templated/generic class based on that type in C# / C++

    - by stusmith
    Title probably doesn't make a lot of sense, so I'll start with some code: class Foo : public std::vector<Foo> { }; ... Foo f; f.push_back( Foo() ); Why is this allowed by the compiler? My brain is melting at this stage, so can anyone explain whether there are any reasons you would want to do this? Unfortunately I've just seen a similar pattern in some production C# code and wondered why anyone would use this pattern.

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  • Why are mainframes still around?

    - by ThaDon
    It's a question you've probably asked or been asked several times. What's so great about Mainframes? The answer you've probably been given is "they are fast" "normal computers can't process as many 'transactions' per second as they do". Jeese, I mean it's not like Google is running a bunch of Mainframes and look how many transactions/sec they do! The question here really is "why?". When I ask this question to the mainframe devs I know, they can't answer, they simply restate "It's fast". With the advent of Cloud Computing, I can't imagine mainframes being able to compete both cost-wise and mindshare-wise (aren't all the Cobol devs going to retire at some point, or will offshore just pickup the slack?). And yet, I know a few companies that still pump out net-new Cobol/Mainframe apps, even for things we could do easily in say .NET and Java. Anyone have a real good answer as to why "The Mainframe is faster", or can point me to some good articles relating to the topic?

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  • Why do they initialize pointers this way?

    - by Rob
    In almost all of the books I read and examples I go through I see pointers initialized this way. Say that I have a class variable NSString *myString that I want to initialize. I will almost always see that done this way: -(id)init { if (self = [super init]) { NSString *tempString = [[NSString alloc] init]; myString = tempString; [tempString release]; } return self; } Why can't I just do the following? -(id)init { if (self = [super init]) { myString = [[NSString alloc] init]; } return self; } I don't see why the extra tempString is ever needed in the first place, but I could be missing something here with memory management. Is the way I want to do things acceptable or will it cause some kind of leak? I have read the Memory Management Guide on developer.apple.com and unless I am just missing something, I don't see the difference.

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  • why this with excel sheet reading?

    - by Lalit
    Hi, I am reading the excel sheet from c# interop services cell by cell. where as my excel sheet have Date cells. It generates some double values , I am converting them in date by : double dbl = Convert.ToDouble(((Excel.Range)worksheet.Cells[iRowindex, colIndex_q17]).Value2); string strDate3 = DateTime.FromOADate(dbl).ToShortDateString(); drRow[dtSourceEXLData.Columns[constants.VisualDate]] = strDate3; ok? but some time happening the value of ((Excel.Range)worksheet.Cells[iRowindex,colIndex_q17]).Value2 getting date formate.why this is happeing? plaease guide me. it throws excepion of "input string not in correct format".why it is not generating double value like other cell of same column?

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  • Why call iframe from javascript

    - by sammville
    I want to know why some ad codes or embed codes don't directly give you iframe code to embed on your site instead they give a javascript code which links to another javascript file on their server. The file on their server calls the iframe which serves the content. Why is this done and what are the benefits of this method. Example: this is the code issued by amazon: <script type="text/javascript" src="http://www.assoc-amazon.co.uk/s/ads.js"></script> Which opens another javascript file that calls the iframe.

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  • Why do I have to give an identifier?

    - by Knowing me knowing you
    In code: try { System.out.print(fromClient.readLine()); } catch(IOException )//LINE 1 { System.err.println("Error while trying to read from Client"); } In code line marked as LINE 1 compiler forces me to give an identifier even though I'm not using it. Why this unnatural constrain? And then if I type an identifier I'm getting warning that identifier isn't used. It just doesn't make sense to me, forcing a programmer to do something unnecesarry and surplus. And after me someone will revise this code and will be wondering if I didn't use this variable on purpouse or I just forgot. So in order to avoid that I have to write additional comment explaining why I do not use variable which is unnecessary in my code. Thanks

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  • why is there different syntax same outcome?

    - by Lizard
    Why is there different syntax same outcome? For example # Example 1 if($myCondition == true) : #my code here endif; if($myCondition == true) { #my code here } # Example 2 foreach($films as $film) : #my code here endforeach; foreach($films as $film) { #my code here } Also I have been using <?= for ages now and i now understand that is deprecated and I should be using <?php echo Is this the case and why? Its alot more annoying to have to write that out each time. What are your thoughts?

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