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  • Why AutoResetEvent and ManualResetEvent does not support name in the constructor?

    - by Ikaso
    On .NET Framework 2.0 AutoResetEvent and ManualResetEvent inherit from EventWaitHandle. The EventWaitHandle class has 4 different constructors. 3 of the constructors support giving a name to the event. On the other hand both ManualResetEvent and AutoResetEvent do not support naming and provide a single constructor that receives the initialState. I can simply inherit from EventWaitHandle and write my own implementation of those classes that support all the constructor overloads, but I don't like to re-invent the wheel if I do not have to. My questions are: Is there a special problem in naming events? Do you have any idea why Microsoft did not support it? Do you have a proposal better than inheriting from the EventWaitHandle class and calling the appropriate constructor as in the following example? public class MyAutoResetEvent: EventWaitHandle { public MyAutoResetEvent(bool initialState) : base(initialState, EventResetMode.AutoReset) { } public MyAutoResetEvent(bool initialState, string name) : base(initialState, EventResetMode.AutoReset, name) { } public MyAutoResetEvent(bool initialState, string name, out bool createdNew) : base(initialState, EventResetMode.AutoReset, name, out createdNew) { } public MyAutoResetEvent(bool initialState, string name, out bool createdNew, EventWaitHandleSecurity eventSecurity) : base(initialState, EventResetMode.AutoReset, string.Empty, out createdNew, eventSecurity) { } }

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  • Why people are so afraid of using clone() (on collection and JDK classes) ?

    - by Bozho
    A number of times I've argued that using clone() isn't such a bad practice. Yes, I know the arguments. Bloch said it's bad. He indeed did, but he said that implementing clone() is bad. Using clone on the other hand, especially if it is implemented correctly by a trusted library, such as the JDK, is OK. Just yesterday I had a discussion about an answer of mine that merely suggests that using clone() for ArrayList is OK (and got no upvotes for that reason, I guess). If we look at the @author of ArrayList, we can see a familiar name - Josh Bloch. So clone() on ArrayList (and other collections) is perfectly fine. (Just look at the implementation). Same goes for Calendar and perhaps most of the java.lang and java.util classes. So, give me a reason why not to use clone() with JDK classes?

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  • In ASP.NET MVC (3.0/Razor), do you prefer multiple views, or conditionals within views? Why?

    - by Chad
    For my new web app, I'm debating on using multiple views, or conditionals within views. An example scenario would be showing different info to users who are authenticated vs non-authenticated. This could be handled a couple ways. In the controller, check IsAuthenticated and return a view based on that In the view, check IsAuthenticated and show blocks of info based on that Pros of multiple views: Smaller, less complicated view - next to no logic in the view Pros of single views: less view files to maintain The obvious cons are the opposites of the pros: more files to maintain or more complicated view files. Which do you prefer? Why? Any pros/cons I haven't outlined here? Update: Assume each view uses a layout page and partial views to abstract the obviously repetitive code.

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  • Why does RIGHT(@foostr, 0) return NULL when @foostr is varchar(max)?

    - by bob-montgomery
    In SQL Server 2005 If I want to find the right-most one character of a varchar(max) variable, no problem: declare @foostr varchar(max) set @foostr = 'abcd' select right (@foostr, 1) ---- d If I want to find the right-most zero characters of a string literal, no problem: select right ('abcd', 0) ------------------ It returns an empty string. If I want to find the right-most zero characters of a varchar(10), no problem: declare @foostr varchar(10) set @foostr = 'abcd' select right (@foostr, 0) ---- It returns an empty string. If I want to find the right-most zero characters of a varchar(max), well: declare @foostr varchar(max) set @foostr = 'abcd' select right (@foostr, 0) ---- NULL It returns NULL. Why?

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  • Why aren't operator conversions implicitly called for templated functions? (C++)

    - by John Gordon
    I have the following code: template <class T> struct pointer { operator pointer<const T>() const; }; void f(pointer<const float>); template <typename U> void tf(pointer<const float>); void g() { pointer<float> ptr; f(ptr); tf(ptr); } When I compile the code with gcc 4.3.3 I get a message (aaa.cc:17: error: no matching function for call to ‘tf(pointer<float>&)’) indicating that the compiler called 'operator pointer<const T>' for the non-templated function f(), but didn't for the templated function tf(). Why and is there any workaround short of overloading tf() with a const and non-const version? Thanks in advance for any help.

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  • Why not speed up testing by using function dependency graph?

    - by Maltrap
    It seems logical to me that if you have a dependency graph of your source code (tree showing call stack of all functions in your code base) you should be able to save a tremendous amount of time doing functional and integration tests after each release. Essentially you will be able to tell the testers exactly what functionality to test as the rest of the features remain unchanged from a source code point of view. If for instance you change a spelling mistake in once piece of the code, there is no reason to run through your whole test script again "just in case" you introduced a critical bug. My question, why are dependency trees not used in software engineering and if you use them, how do you maintain them? What tools are available that generate these trees for C# .NET, C++ and C source code?

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  • Why do I get a "warning: no newline at end of file" ?

    - by user198729
    The file is a helloworld.cpp: #include <iostream> using namespace std; int main() { if(true) cout << "!!!Hello World!!!" << endl; // prints !!!Hello World!!! return 0; } But when I build it,get a warning: g++ -Wall -O2 -c -o hw.o hw.cpp hw.cpp:8:2: warning: no newline at end of file g++ -o myprog hw.o If I add a newline at the end,the warning will go. Why is that newline at end of file recommended in a cpp source file?

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  • Why is this postgres function failing only on one specifc database?

    - by Ollie Edwards
    I'm trying to fix an issue with a legacy database. The quote_literal function is not working for a specific database on an 8.4 install of postgres. Here's my results on a fresh test database: select quote_literal(42); quote_literal --------------- '42' (1 row) And now the same on the target db select quote_literal(42); ERROR: function quote_literal(integer) is not unique LINE 1: select quote_literal(42); ^ HINT: Could not choose a best candidate function. You might need to add explicit type casts. AIUI, the quote_literal(anyvalue) function should handle integer values ok, and this seems to be upheld by the first test. So I figured the quote_literal function must have been overridden in this db but no this doesn't seem to be the case. I could override it with a specific quote_literal(integer) function but I don't see why I should have to. The question is what is could be causing the failure of this function in this specific database whilst not affecting the fresh db?

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  • Why does my array initialization code cause a StackOverflowException to be thrown?

    - by MCS
    The following line of code in my class constructor is throwing a StackOverflowException: myList = new string[]{}; // myList is a property of type string[] Why is that happening? And what's the proper way to initialize an empty array? UPDATE: The cause was in the set method, in which I was attempting to trim all values. What's wrong with this code: set { for (int i = 0; i < myList.Length; i++) { if (myList[i] != null) myList[i] = myList[i].Trim(); } }

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  • Why should I use an N-Tier Approach When using an SqlDatasource is ALOT EASIER ?

    - by The_AlienCoder
    When it comes to web development I have always tried to work SMART not HARD. So for along time My Aproach to interacting with databases in my AspNet projects has been this : 1) Create my stored procedures 2) Drag an SQLDatasource control on my aspx page 3) Bind a DataList Control to my SQLDatasource 4) Insert, Update & Delete by using my Datalist or programmatically using built in SQLDatasource methods e.g MySqlDataSource.InsertParameters["author"].DefaultValue = TextBox1.Text; MySqlDataSource.Insert(); Recently however I got a relatively easy web project. So I decided to employ a 3-tier Model...But I got exhausted halfway and just didnt seem worth it ! It seemed like I was working too HARD for a project that could have been easily accomplished by a couple of SqlDataSource Controls. So Why Is the N-Tier Model better than my Approach? Has it anything to do with performance? What are the advantages of the ObjectDataSource control over the SqlDataSource Control?

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  • Why is doing a top(1) on an indexed column in mssql slow?

    - by reinier
    I'm puzzled by the following. I have a DB with around 10 million rows, and (among other indices) on 1 column is an index. Now I have 700k rows where the campaignid is indeed 3835 For all these rows, the connectionid is the same. I just want to find out this connectionid. use messaging_db; SELECT TOP (1) connectionid FROM outgoing_messages WITH (NOLOCK) WHERE (campaignid_int = 3835) Now this query takes approx 30 seconds to perform! I (with my small db knowledge) would expect that it would take any of the rows, and return me that connectionid If I test this same query for a campaign which only has 1 entry, it goes really fast. So the index works. How would I tackle this and why does this not work?

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  • Why can't I expose an interface in a .NET asmx web service?

    - by mcliedtk
    I have a .NET web service (using asmx...have not upgraded to WCF yet) that exposes the following: public class WidgetVersion1 : IWidget {} public class WidgetVersion2 : IWidget {} When I attempt to bind to the web service, I get the following serialization error: Cannot serialize member WidgetVersion1 of type IWidget because it is an interface. I have tried adding various attributes to the IWidget interface (XmlIgnore, SoapIgnore, NonSerialized), but they are not valid on an interface. Does anyone know why I am unable to expose the interface? I assume WSDL does not support interfaces, but couldn't .NET get around this by simply not serializing the interface? Are there any ways around this apart from removing the IWidget interface from the WidgetVersion1 and WidgetVersion2 class definitions?

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  • Why is passing a string literal into a char* arguament only sometimes a compiler error?

    - by Brian Postow
    I'm working in a C, and C++ program. We used to be compiling without the make-strings-writable option. But that was getting a bunch of warnings, so I turned it off. Then I got a whole bunch of errors of the form "Cannot convert const char* to char* in argmuent 3 of function foo". So, I went through and made a whole lot of changes to fix those. However, today, the program CRASHED because the literal "" was getting passed into a function that was expecting a char*, and was setting the 0th character to 0. It wasn't doing anything bad, just trying to edit a constant, and crashing. My question is, why wasn't that a compiler error? In case it matters, this was on a mac compiled with gcc-4.0.

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  • Different results coming out of an init method than those expected. Why does this happen and how can

    - by Mark Reid
    When I run this method the two properties I have are set to (NULL) when I try and access them outside of the if statement. But they are set to 0 and NO if I check them inside the for loop. -(id) init { NSLog(@"Jumping into the init method!"); if (self = [super init]) { NSLog(@"Running the init method extras"); accumulator = 0; NSLog(@"self.accumulator is %g", accumulator); decimal = NO; } NSLog(@"Calc after init is: %@ and %@", self.accumulator, self.decimal); return self; } Any suggestions as to why what comes out is different from what's done in the for loop?

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  • Why is my substitution control suddenly not working in ASP.NET 4.0?

    - by Steve Wortham
    I just upgraded my site from ASP.NET 3.5 to 4.0. I've been working through some breaking changes (there were more than I expected). One I can't figure out, however, is why my <asp:Substitution /> control suddenly stopped working like it should. It's supposed to ignore the output cache settings of the parent page and update upon every request. For some reason that isn't happening. It's caching for the full 10 minutes (the OutputCache setting for my home page). Any ideas?

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  • Why is conversion from UTF-8 to ISO-8859-1 not the same in Windows and Linux?

    - by user1895307
    I have the following in code to convert from UTF-8 to ISO-8859-1 in a jar file and when I execute this jar in Windows I get one result and in CentOS I get another. Might anyone know why? public static void main(String[] args) { try { String x = "Ä, ä, É, é, Ö, ö, Ãœ, ü, ß, «, »"; Charset utf8charset = Charset.forName("UTF-8"); Charset iso88591charset = Charset.forName("ISO-8859-1"); ByteBuffer inputBuffer = ByteBuffer.wrap(x.getBytes()); CharBuffer data = utf8charset.decode(inputBuffer); ByteBuffer outputBuffer = iso88591charset.encode(data); byte[] outputData = outputBuffer.array(); String z = new String(outputData); System.out.println(z); } catch(Exception e) { System.out.println(e.getMessage()); } } In Windows, java -jar test.jar test.txt creates a file containing: Ä, ä, É, é, Ö, ö, Ü, ü, ß, «, » but in CentOS I get: ??, ä, ??, é, ??, ö, ??, ü, ??, «, » Help please!

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  • Why's a simple change to rt.jar causing the Java Runtime Environment to crash silently?

    - by Tom
    This is what I'm doing: extract contents of my JRE's rt.jar extract src.zip of my JDK (same version) Now, if I copy Runtime.java from the extracted src folder and compile it using javac.exe without any modifications and then put it in the extracted rt folder to finally put everything back in a jar file using jar.exe, everything works as expected. The JRE runs fine. However, if I make the slightest change to Runtime.java and compile it and put it in rt.jar, the JRE crashes whenever I attempt to start it. This is an example of a slight change that causes the silent crash: /** Don't let anyone else instantiate this class */ private Runtime() { System.out.println("This is a test."); } Instead of: /** Don't let anyone else instantiate this class */ private Runtime() {} Could anyone tell me why this is causing my JRE to crash? Thanks in advance.

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  • Why does jQuery do this in its constructor function implementation?

    - by mattcodes
    If we look at the latest jQuery source at http://code.jquery.com/jquery-latest.js we see the following: var jQuery = function( selector, context ) { // The jQuery object is actually just the init constructor 'enhanced' return new jQuery.fn.init( selector, context ); } My understanding of the new keyword in Javascript is essentially JavaScript passes the function an empty object {} and the function sets stuff on it via this.blah. Also from my understanding new differs from .call/.apply etc.. in that the return object also has the prototype set to that of the function. So the return value should have a prototype that the same as jQuery.prototype.init.prototype (or jQuery.fn.init.prototype). However from what I see its prototype is set to jQuery.prototype thus all the commands available to work on the set. Why is this? What am I missing in my understanding?

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  • Why does $('#id') return true if id doesn't exist?

    - by David
    I always wondered why jQuery returns true if I'm trying to find elements by id selector that doesnt exist in the DOM structure. Like this: <div id="one">one</div> <script> console.log( !!$('#one') ) // prints true console.log( !!$('#two') ) // is also true! (empty jQuery object) console.log( !!document.getElementById('two') ) // prints false </script> I know I can use !!$('#two').length since length === 0 if the object is empty, but it seems logical to me that a selector would return the element if found, otherwise null (like the native document.getElementById does). F.ex, this logic can't be done in jQuery: var div = $('#two') || $('<div id="two"></div>'); Wouldnt it be more logical if the ID selector returned null if not found? anyone?

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  • why this assembly program is loaded from the address 0B3D:0000?

    - by viperchaos
    I have seen a assembly program written from a book about assemble: assume cs:code code segment dw 0123h,0456h,0789h,0abch,0defh,0fedh,0cbah,0987h mov bx,0 mov ax,0 mov cx,8 s: add ax,cs:[bx] add bx,2 loop s mov ax,4c00h int 21h code ends end This program's function is to add eight numbers. The author compiled this program in the DOS and use the DEBUG to see how this program be loaded. The author use the R command and got that DS = 0B2DH ES = 0B2D SS = 0B3D CS = 0B3D IP = 0000 And then the author said that this program is loaded from the address 0B3D:0000. I'm a confused that why this program is loaded from the address 0B3D:0000? Is this because the existence of the Program Segment Prefix(PSP)? If the answer is the existence of the PSP, what is in the PSP?

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  • Why do C++ streams use char instead of unsigned char?

    - by Johannes Schaub - litb
    I've always wondered why the C++ Standard library has instantiated basic_[io]stream and all its variants using the char type instead of the unsigned char type. char means (depending on whether it is signed or not) you can have overflow and underflow for operations like get(), which will lead to implementation-defined value of the variables involved. Another example is when you want to output a byte, unformatted, to an ostream using its put function. Any ideas? Note: I'm still not really convinced. So if you know the definitive answer, you can still post it indeed.

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  • Why do I get CA1811 when I call a private method from a public method in C++/CLI?

    - by brickner
    I've recently upgraded my project from Visual Studio 2008 to Visual Studio 2010. By enabling Code Analysis and building on Release, I'm getting warning CA1811: Avoid uncalled private code. I've managed to reduce the code to this: .h file: public ref class Foo { public: virtual System::String^ ToString() override; private: static System::String^ Bar(); }; .cpp file: String^ Foo::ToString() { return Bar(); } String^ Foo::Bar() { return "abc"; } The warning I get: CA1811 : Microsoft.Performance : 'Foo::Bar(void)' appears to have no upstream public or protected callers. It doesn't matter if Bar() is static or not. I've tried to reproduce it in C# but I can't. I can only reproduce it in C++/CLI. Why do I get this warning? Is this a Visual Studio 2010 bug?

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  • An Inaccessible JavaScript Object property - Why is Firebug showing this?

    - by Matty
    So, I'm attempting to access the content of an object and for the life of me can't figure out why I can't. I'm starting to believe that the object doesn't have the properties that Firebug indicates that it does. More likely than that I'm just not using the right syntax to access them. Give the following function: function(userData) { console.log(userData); // statement 1 console.log(userData.t_nodecontent); // statement 2 } Which generates the following FireBug output for statement 1 and unknown for statement 2. Is there something obvious that I'm overlooking in the way I'm attempting to reference the value of t_nodecontent? I'm at a loss :(

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