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  • Why can't my c++ program find the necessary .dll file?

    - by RemiX
    I am trying to use OpenCV (a computer vision library), which appearently uses a few .dll files, located in C:\OpenCV\bin (which has been added to the system PATH variable). However, if I try to run a simple test program, it gives a system error: "The program can't start because highgui.dll is missing from your computer. Try reinstalling the program to fix this problem." If I copy the highgui.dll file into the system32 folder, it works, but I don't want to have to put all the necessary .dll files in the system32 folder. Does anyone know why the .dll file can't be found or what I should do to fix it? (I already checked all paths in the PATH variable for validity.)

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  • Where and why JVM checks that the return type of entry method main(String args[]) is void and not an

    - by akjain
    I will try to answer both, please correct me if I am wrong: Where: If a static method is being called using Classname.method() or using reflection then it doesn’t matter even if you change the return type of the calling method, the same method will still be called. So JVM probably checks this in one of the native methods of jvm.cpp methodHandle m (THREAD, init_klass-find_method(vmSymbols::object_initializer_name(), vmSymbols::void_method_signature())); if (m.is_null()) { ------ THROW_MSG_0 ……….. Why: Although it’s of useless to return a value from main, as java does not do anything with it but if we try to change the return type of main to int for example, JVM throws public static int main(String[] args) { return 1; } java.lang.NoSuchMethodError: main Exception in thread "main" So may be Java mandates the use of same signature for entry method main() to maintain a symmetry in all Java programs written.

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  • why number 9 in kill -9 command in unix?

    - by Alby
    I understand it's off topic, I couldn't find anywhere online and I was thinking maybe programming gurus in the community might know this. I usually use kill -9 pid to kill the job. I always wondered the origin of 9. I looked it up online, and it says "9 Means KILL signal that is not catchable or ignorable. In other words it would signal process (some running application) to quit immediately" (source: http://wiki.answers.com/Q/What_does_kill_-9_do_in_unix_in_its_entirety) But, why 9? and what about the other numbers? is there any historical significance or because of the architecture of Unix? Thanks!

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  • Linux rpm installs but cannot erase. Why?

    - by rmosley
    My Perl code installed several (4) rpm files as root. the next install removes them (rpm -e) before installing a newer version. One does not remove, with rpm -e giving the error that it is not installed. However, later when the updated file is installed, the message is given that it is already installed. Manual attempts to remove give the same results. My questions are how to force removal something from the rpm database, and why does this contradication exist (not installed from rpm -e and already installed from rpm -Uvh and rpm -ivh)?

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  • C: Why does gcc allow char array initialization with string literal larger than array?

    - by Ashwin
    int main() { char a[7] = "Network"; return 0; } A string literal in C is terminated internally with a nul character. So, the above code should give a compilation error since the actual length of the string literal Network is 8 and it cannot fit in a char[7] array. However, gcc (even with -Wall) on Ubuntu compiles this code without any error or warning. Why does gcc allow this and not flag it as compilation error? gcc only gives a warning (still no error!) when the char array size is smaller than the string literal. For example, it warns on: char a[6] = "Network"; [Related] Visual C++ 2012 gives a compilation error for char a[7]: 1>d:\main.cpp(3): error C2117: 'a' : array bounds overflow 1> d:\main.cpp(3) : see declaration of 'a'

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  • Why Does try ... catch Blocks Require Braces?

    - by Bidou
    Hello. While in other statements like if ... else you can avoid braces if there is only one instruction in a block, you cannot do that with try ... catch blocks: the compiler doesn't buy it. For instance: try do_something_risky(); catch (...) std::cerr << "Blast!" << std::endl; With the code above, g++ simply says it expects a '{' before do_something_risky(). Why this difference of behavior between try ... catch and, say, if ... else ? Thanks!

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  • optgroup class gets applied to all sub-options in FF, why?

    - by Camran
    I have an optgroup like this: <optgroup label="Eller välj Län" title="Eller välj Län" style="background-color:#FC9;"> <option value="Blekinge Län">Blekinge</option> <option value="Dalarna Län">Dalarna</option> <option value="Gotlands Län">Gotland</option> </optgroup> Problem is, only in Firefox, the class applies to all options inside the optgroup. I need it to apply only to the optgroup label... Any ideas why? Thanks

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  • Why a revert a file in EGit, but the dirty symbol '<' still exist in the project view?

    - by Happier
    I try EGit revert for several days, It's very confuse that when I revert the file following the user guide, and I still got the file dirty symbol in the related file. http://wiki.eclipse.org/EGit/User_Guide#Reverting_Changes I choose 'Replace with' - 'File in Git Index', it works, the content has been revert, but the symbol stays the same, sometimes, the symbol will disappear after a while, but sometimes, it didn't disappear. I'm using eclipse on windows, I'm not sure it's about the '\r\n' character. But I use 'Compare with ' - 'File in Git Index', two files look the same. Hope someone can tell me why, I think it can be a bug? Thank you in advance.

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  • Why does var evaluate to System.Object in "foreach (var row in table.Rows)"?

    - by DanM
    When I enter this foreach statement... foreach (var row in table.Rows) ...the tooltip for var says class System.Object I'm confused why it's not class System.Data.DataRow. (In case you're wondering, yes, I have using System.Data at the top of my code file.) If I declare the type explicitly, as in... foreach (DataRow row in table.Rows) ...it works fine with no errors. Also if I do... var numbers = new int[] { 1, 2, 3 }; foreach (var number in numbers) ...var evaluates to struct System.Int32. So, the problem is not that var doesn't work in a foreach clause. So, there's something strange about DataRowCollection where the items don't automatically evaluate to DataRow. But I can't figure out what it is. Does anyone have an explanation?

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  • Why does my WCF service return and ARRAY instead of a List <T> ?

    - by user193189
    In the web servce I say public List<Customer> GetCustomers() { PR1Entities dc = new PR1Entities(); var q = (from x in dc.Customers select x).ToList(); return q; } (customer is a entity object) Then I generate the proxy when I add the service.. and in the reference.cd it say public wcf1.ServiceReference1.Customer[] GetCustomers() { return base.Channel.GetCustomers(); } WHY IS IT AN ARRAY? I asked for a List. help.

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  • Why don't hardware failures show up at the programming language level?

    - by Julian Cienfuegos
    I am wondering if anyone can give my a good answer, or at least point me in the direction of a good reference to the following question: How come I have never heard of a computer breaking in a very fundamental way? How come when I declare x to be a double it stays as a double? How come there is never a short circuit that robs it of some bytes and makes it an integer? Why do we have faith that when we initialize x to 10, there will never be a power surge that will cause it to become 11, or something similar? I think I need a better understanding of memory. Thanks, and please don't bash me over the head for such a simple/abstract question.

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  • Why is it inserting 0's instead of blank spaces into my DB using php?

    - by zeckdude
    I have an insert: $sql = 'INSERT into orders SET fax_int_prefix = "'.$_SESSION['fax_int_prefix'].'", fax_prefix = "'.$_SESSION['fax_prefix'].'", fax_first = "'.$_SESSION['fax_first'].'", fax_last = "'.$_SESSION['fax_last']; The value of all of these fields is that they are blank right before the insert. Here is an example of one of them I echo'd out just before the insert: $_SESSION[fax_prefix] = For some reason it inserts the integer 0, instead of a blank value or null, as it should. Why is it inserting 0's instead of blank spaces into my DB?

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  • Why Do try ... catch Blocks Require Braces?

    - by Bidou
    Hello. While in other statements like if ... else you can avoid braces if there is only one instruction in a block, you cannot do that with try ... catch blocks: the compiler doesn't buy it. For instance: try do_something_risky(); catch (...) std::cerr << "Blast!" << std::endl; With the code above, g++ simply says it expects a '{' before do_something_risky(). Why this difference of behavior between try ... catch and, say, if ... else ? Thanks!

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  • Why in C++ do we use DWORD rather than unsigned int?

    - by byte
    I'm not afraid to admit that I'm somewhat of a C++ newbie, so this might seem like a silly question but.... I see DWORD used all over the place in code examples. When I look up what a DWORD truly means, its apparently just an unsigned int (0 to 4,294,967,295). So my question then is, why do we have DWORD? What does it give us that the integral type 'unsigned int' does not? Does it have something to do with portability and machine differences?

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  • why does it use the movl instead of push ?!

    - by user554403
    hi all. pay attention to this code : #include <stdio.h> void a(int a, int b, int c) { char buffer1[5]; char buffer2[10]; } int main() { a(1,2,3); } after that : gcc -S a.c that command shows our source code in assembly. now we can see in the main function, we never use "push" command to push the arguments of the a function into the stack. and it used "movel" instead of that main: pushl %ebp movl %esp, %ebp andl $-16, %esp subl $16, %esp movl $3, 8(%esp) movl $2, 4(%esp) movl $1, (%esp) call a leave why does it happen? what's difference between them?

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  • Why is [date] + [time] non-deterministic in SQL Server 2008?

    - by John Gietzen
    I'm trying to do the following for my IIS logs table: ALTER TABLE [W3CLog] ADD [LogTime] AS [date] + ([time] - '1900-01-01') PERSISTED However, SQL Server 2008 tells me: Computed column 'LogTime' in table 'W3CLog' cannot be persisted because the column is non-deterministic. The table has this definition: CREATE TABLE [dbo].[W3CLog]( [Id] [bigint] IDENTITY(1,1) NOT NULL, ... [date] [datetime] NULL, [time] [datetime] NULL, ... ) Why is that non-deterministic? I really need to index that field. The table currently has 1598170 rows, and it is a pain to query if we can't do an index seek on the full time. Since this is being UNION'd with some other log formats, we can't very easily just use the two columns separately.

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  • Why do these seemingly similar queries have such drastically different run times?

    - by Jherico
    I'm working with an oracle DB trying to tune some queries and I'm having trouble understanding why working a particular clause in a particular way has such a drastic impact on the query performance. Here is a performant version of the query I'm doing select * from ( select a.*, rownum rn from ( select * from table_foo ) a where rownum < 3 ) where rn >= 2 The same query by replacing the last two lines with this ) a where rownum >=2 rownum < 3 ) performs horribly. Several orders of magnitude worse ) a where rownum between 2 and 3 ) also performs horribly. I don't understand the magic from the first query and how to apply it to further similar queries.

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  • Why are namespaces acting up in Visual Studio 2010?

    - by duluca
    I've just converted a project to VS 2010 and something really weird is going on with namespaces. Let me give an example, the following code used to work in VS2008: MySystem.Core.Object { using MySystem.Core.OtherObject; ... } But now it doesn't, it either wants the whole thing to be put outside of the namespace like this: using MySystem.Core.OtherObject; MySystem.Core.Object { ... } or be rewritten it like: MySystem.Core.Object { using OtherObject; ... } I understand why this works and maybe is the correct way of handling this, but now we'd have to change thousands of lines of code! Which is not cool. Any idea to circumvent this requirement?

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  • different brainpoolP521r1 parameters for flexiProvider. Why?

    - by user182846
    I am trying to generate ECC public private key pairs using flexiProvider. I have noticed that values for parameters like p and q are different in brainpoolP521r1 of flexiProvider than those which are specified in many sites. Values specified are Q= AADD.... but what I get is Q=8948... Any idea why flexiProvider does not use specified values and whether having different values is affectes security. I am new to ECC. Any help will be greatly appreciated.

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  • why can not create instance from any class out side of constructor?

    - by Phsika
    why i generate instance outside of class. i give inheritance snifC to sinifD i need to create instance sinifC sinifc= new sinifC() in SinifD out side of constructor? public class sinifC { public void method3() { Console.WriteLine("Deneme3"); } } public class sinifD : sinifC { void method4() { Console.WriteLine("Deneme4"); } public sinifD() { sinifC sinifc = new sinifC(); sinifc.method3(); } } i want to make it below: public class sinifC { public void method3() { Console.WriteLine("Deneme3"); } } public class sinifD : sinifC { void method4() { Console.WriteLine("Deneme4"); } sinifC sinifc = new sinifC(); sinifc.method3(); } Error: Invalid token '(' in class, struct, or interface member declaration

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  • Why do we need to estimate the true position in Kalman filters?

    - by Kalla
    I am following a probably well-known tutorial about Kalman filter here From these lines of code: figure; plot(t,pos, t,posmeas, t,poshat); grid; xlabel('Time (sec)'); ylabel('Position (feet)'); title('Figure 1 - Vehicle Position (True, Measured, and Estimated)') I understand that x is the true position, y is measured position, xhat is estimated position. Then, if we can compute x (this code: x = a * x + b * u + ProcessNoise;), why do we need to estimated x anymore?

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  • C# Why does calling an interface member from a class generate an error?

    - by Jack
    So I have an interface: interface IFoo { int Bar(); int this[int i] {get; set;} } And a class that derives from it class Foo : IFoo { public int IFoo.Bar() { //Implementation { public int IFoo.this[int i] { //Implementation } } Now, I try to do this: var fooey = new Foo(); int i = Fooey.Bar(); or this: int i = Fooey[4]; I would expect these to work properly. However, the compiler generates an error as if such members don't exist. Why is that? I am aware I can cast Foo as IFoo, but I am also aware that casting is costly to performance, which is often the reason to use interfaces in the first place. EDIT 1: These are the errors generated 'Foo' does not contain a definition for 'Bar' and no extension method 'Bar' accepting a first argument of type 'Foo' could be found (are you missing a using directive or an assembly reference?) "Cannot apply indexing to an expression of type 'Foo'"

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  • Why does php's file_get_contents incorrectly retrieve json files from xkcd?

    - by hally
    In writing a PHP script to download xkcd comics, i incurred errors when trying to get specific comics (as opposed to the latest one). Specifically, pointing file_get_contents at the following url: xkcd.com/$COMIC_NUM/info.0.json inexplicably retrieved the xhtml version of the comic's page on xkcd.com, and not a JSON file. However, if i request the exact same url in my browser, the correct JSON file is downloaded. I'm not sure why this is happening, but i suspect it has something to do with the request headers being sent. Please help! :S

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