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• C# Calling Methods in Generic Classes

  - by aip.cd.aish

  I am extending the ImageBox control from EmguCV. The control's Image property can be set to anything implementing the IImage interface. All of the following implement this interface: Image<Bgr, Byte> Image<Ycc, Byte> Image<Hsv, Byte> Now I want to call the Draw method on the object of the above type (what ever it may be). The problem is when I access the Image property, the return type is IImage. IImage does not implement the Draw method, but all of the above do. I believe I can cast the object of type IImage to one of the above (the right one) and I can access the Draw method. But how do I know what the right one is? If you have a better way of doing this, please suggest that as well.

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• visual studio intellisense error

  - by rakkarage

  template <typename T> class Test { friend Test<T> & operator * (T lhs, const Test<T> & rhs) { Test<T> r(rhs); // return r *= lhs; } } 4 IntelliSense: identifier "T" is undefined why is T defined on line 3 but not line 4? i mean i guess its not a real error just an intellisense error... it works anyway but is there something wrong? can i fix it? or remove the red squiggles somehow? thanks i am using visual studio 2010... i wonder if this happens in other versions as well?

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• Having an @ inside of a string - PHP

  - by Msencenb

  So I know that you use a backslash to escape most things in php however the @ symbol is an operator that suppresses error messages. I'm trying to put an email string like this inside of an array "[email protected]", however php is throwing an error. How do you escape the @ sign? EDIT: Here is the code example that was throwing the error: $arr = array(3=> "[email protected]",4=> "[email protected]"); However replacing the double quotes with single quotes fixes the error as answered below.... why is that true?

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• Same code... but warning!Any ideas?

  - by FILIaS

  I've a question for a warning message that i get. For this line,using qsort: qsort(catalog, MAX ,sizeof catalog, struct_cmp_by_amount); I get this warning: warning: passing argument 4 of ‘qsort’ makes pointer from integer without a cast struct_cmp_by_amount is another function on the program. BUT,for another program with the same code, with the same exactly struct_cmp_by_amount function, i dont get that warning for the 4th argument! qsort(structs, structs_len, sizeof(struct st_ex), struct_cmp_by_price); I'm wandering about why that;s happening. Have you any idea?

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• When does ref($variable) return 'IO'?

  - by Zaid

  Here's the relevant excerpt from the documentation of the ref function: The value returned depends on the type of thing the reference is a reference to. Builtin types include: SCALAR ARRAY HASH CODE REF GLOB LVALUE FORMAT IO VSTRING Regexp Based on this, I imagined that calling ref on a filehandle would return 'IO'. Surprisingly, it doesn't: use strict; use warnings; open my $fileHandle, '<', 'aValidFile'; close $fileHandle; print ref $fileHandle; # prints 'GLOB', not 'IO' perlref tries to explain why: It isn't possible to create a true reference to an IO handle (filehandle or dirhandle) using the backslash operator. The most you can get is a reference to a typeglob, which is actually a complete symbol table entry [...] However, you can still use type globs and globrefs as though they were IO handles. In what circumstances would ref return 'IO' then?

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• Problem of using cin twice.

  - by gc

  Here is the code: string str; cinstr; cout<<"first input:"<<str<<endl; getline(cin, str); cout<<"line input:"<<str<<endl; The result is that getline never pauses for user input, therefore the second output is always empty. After spending some time on it, I realized after the first call "cinstr", it seems '\n' is still stored in cin (using cin.peek() to check), which ends getline immediately. The solution will be adding one more line between the first usage and the second one: cin.ignore(numeric_limits::max(), '\n'); However, I still don't understand, why is '\n' left there after the first call? What does istream& operator really do?

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• SQL vs MySQL: Rules about aggregate operations and GROUP BY

  - by Phazyck

  In this book I'm currently reading while following a course on databases, the following example of an illegal query using an aggregate operator is given: Find the name and age of the oldest sailor. Consider the following attempt to answer this query: SELECT S.name, S.age FROM Sailors.S The intent is for this query to return not only the maximum age but also the name of the sailors having that age. However, this query is illegal in SQL--if the SELECT clause uses an aggregate operation, then it must use only aggregate operations unless the query contains a GROUP BY clause! Some time later while doing an exercise using MySQL, I faced a similar problem, and made a mistake similar to the one mentioned. However, MySQL didn't complain and just spit out some tables which later turned out not be what I needed. Is the query above really illegal in SQL, but legal in MySQL, and if so, why is that? In what situation would one need to make such a query?

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• How does Hibernate detect dirty state of an entity object?

  - by ???'Lenik

  Is it using some kind of byte codes modification to the original classes? Or, maybe Hibernate get the dirty state by compare the given object with previously persisted version? I'm having a problem with hashCode() and equals() methods for complicated objects. I feel it would be very slow to compute hash code if the object has collection members, and cyclic references are also a problem. If Hibernate won't use hashCode()/equals() to check the dirty state, I guess I should not use equals()/hashCode() for the entity object (not value object), but I'm also afraid if the same operator (==) is not enough. So, the questions are: How does Hibernate know if a property of an object is changed? Do you suggest to override the hashCode()/equals() methods for complicated objects? What if they contains cyclic references? And, also, Would hashCode()/equals() with only the id field be enough?

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• How to put/get INT to/from a WCHAR array ?

  - by nimo

  how can I put a INT type variable to a wchar array ? Thanks EDIT: Sorry for the short question. Yes we can cast INT to a WCHAR array using WCHAR*, but when we are retrieving back the result (WCHAR[] to INT), I just realize that we need to read size of 2 from WCHAR array since INT is 4 BYTEs which is equal to 2 WCHARs. WCHAR arData[20]; INT iVal = 0; wmemcpy((WCHAR*)&iVal, arData, (sizeof(INT))/2); Is this the safest way to retrieve back INT value from WCHAR array

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• Typed DefaultListModel to avoid casting

  - by Thomas R.

  Is there a way in java to have a ListModel that only accepts a certain type? What I'm looking for is something like DefaultListModel<String> oder TypedListModel<String>, because the DefaultListModel only implements addElement(Object obj) and get(int index) which returns Object of course. That way I always have to cast from Object to e.g. String and there is no guarantee that there are only strings in my model, even though I'd like to enforce that. Is this a flaw or am I using list models the wrong way?

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• Consing lists with user-defined type in Haskell

  - by user1319603

  I have this type I defined myself: data Item = Book String String String Int -- Title, Author, Year, Qty | Movie String String String Int -- Title, Director, Year, Qty | CD String String String Int deriving Show -- Title, Artist, Year, Qty I've created an empty list all_Items = [] With the following function I am trying to insert a new book of type Item (Book) into the all_Items addBook all_Items = do putStrLn "Enter the title of the book" tit <- getLine putStrLn "Enter the author of the book" aut <- getLine putStrLn "Enter the year this book was published" yr <- getLine putStrLn "Enter quantity of copies for this item in the inventory" qty <- getLine Book tit aut yr (read qty::Int):all_Items return(all_Items) I however am receiving this error: Couldn't match expected type `IO a0' with actual type `[a1]' The error points to the line where I am using the consing operator to add the new book to the list. I can gather that it is a type error but I can't figure out what it is that I am doing wrong and how to fix it. Thanks in Advance!

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• Within a Visual Studio 2008 Add-In, how can I tell which interfaces a class' property implements?

  - by Tim Stewart

  In a Visual Studio Add-In, I'm enumerating over the members of a class in the current source file. When I encounter a property (e.g. CodeElement.Kind == vsCMElement.vsCMElementProperty) I cast that CodeElement to a CodeProperty and I can see the property's name and type. What I'm having a problem with is getting a list of the property's implemented interfaces. I'm wondering if this is because the implemented interfaces might be in assemblies that Visual Studio doesn't "know" about. Is there a way to get the list of interfaces that a property implements? Thanks.

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• Copying a 14bit grayscale image (saved in long[]) to a pictureBox

  - by Itsik

  My camera gives me 14bit grayscale images, but the API's function returns a long* to the image data. (so i'm assuming 4 bytes for each pixel) My application is written in C++/CLI, and the pictureBox is of .NET type. I am currently using the BitmapData.LockBits() mechanism to gain pointer access to the image data, and using memcpy(bmpData.Scan0.ToPointer(), imageData, sizeof(long)*height*width) to copy the image data to the Bitmap. For now, the only PixelFormat that is working is 32bit RGB, and the image appears in shades of blue with contours. Trying to initialize the Bitmap as 16bppGrayscale isn't working. I would ideally want to cast the array from long to word and using a 16bit format (hoping the the 14bit data will be displayed properly) but I'm not sure if this works. Also, I don't want to iterate over the image data, so finding the min/max and then histogram stretching to [0..255] isnt an option for me (the display must be as efficient as possible) Thanks

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• Can't return a String value and append it...why?

  - by squeezemylime

  I am writing an app and am having problems returning a simple string value, and I'm not sure why. The function I am using (within a file called APIManager.m) is: - (NSString*) returnVenueUrl { NSString *venueUrl = [devEnvironment stringByAppendingString:@"venue/id/"]; return venueUrl; } I can return this properly by doing this in another .m file: APIManager *apiManager = [APIManager apiManager]; NSLog(@"view venue URL is here: %@", [apiManager returnVenueUrl]); But when I go to append a variable cast as a String onto it, I get nothing.. venueURL = [apiManager returnVenueUrl]; venueURL = [venueURL stringByAppendingString:venueId]; NSLog(@"the Full Venue URL is: %", venueURL); If anyone has any advice on how to fix this, it would be much appreciated!

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• JAVA Inheritance Generics and Casting.

  - by James Moore

  Hello, I have two classes which both extends Example. public class ClassA extends Example { public ClassA() { super("a", "class"); } .... } public class ClassB extends Example { public ClassB() { super("b", "class"); } .... } public class Example () { public String get(String x, String y) { return "Hello"; } } So thats all very well. So suppose we have another class called ExampleManager. With example manager I want to use a generic type and consequently return that generic type. e.g. public class ExampleManager<T extends Example> { public T getExample() { return new T("example","example"); // So what exactly goes here? } } So where I am returning my generic type how do i get this to actually work correctly and cast Example as either classA or classB? Many Thanks

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• File::GlobMapper doesnt seem to be exporting globmap

  - by justintime

  The following is pretty well copied from the documentation. use File::GlobMapper qw( globmap ); for my $pair (globmap '<*.tar.gz>' => '<#1.tgz>' ) { } And it gives String found where operator expected at globmapper_test1.pl line 4, near "globmap '<*.tar.gz>'" (Do you need to predeclare globmap?) (Using ActivePerl 5.10.0 on Windows) Side questions - if GlobMapper only exports one function, why is it set so you have to export it explicitly?

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• Programming issue while applying text to the third party control.

  - by srivatsa

  Hello I have used some third party controls in my windows application. There is a snippet which is being used in our code which re-initializes all the .text property of all the controls on the form. Everything works fine except for a control. This control is similar to the Windows Panel except for it has a dropdown appearance. This control has .Caption property instead of .Text property associated to it. This causes the problem whenever i use such codes foreach (Control oControl in this.Controls) { if (oControl is DropDownPanel) { { oControl.Text = rm_ResourceManager.GetString(oControl.Name + ".Text"); } } } The text is not set here for the DropDownPanel control in the above method. Since .Text is not available for DropDownPanel control. I cannot do the following either .. ((DropDownPanel)oControl).Caption = rm_ResourceManager.GetString(oControl.Name + ".Text"); Cos it shall throw exception if i try to cast oControl with that of DropDownPanel Any ideas how can i overcome such a condition. Regards

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• doubt in sizeof implementation

  - by aks

  Below is the program to find the size of a structure without using sizeof operator: struct MyStruct { int i; int j; }; int main() { struct MyStruct *p=0; int size = ((char*)(p+1))-((char*)p); printf("\nSIZE : [%d]\nSIZE : [%d]\n", size); return 0; } My doubt is: Why is typecasting to char * required? If I don't use the char* pointer, the output is 1 - WHY?

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• How to get a reference to IDuplexChannel, IDuplexSessionChannel or IOutputChannel in Wcf

  - by wizlb

  I have a duplex Wcf service and I'd like to get a reference to IDuplexChannel, IDuplexSessionChannel or IOutputChannel so that I can use the non-blocking BeginSend method. On my server, inside of the handler for the initiating method I have the following (I have tried every interface that I listed in place of IOutputChannel. None of them seem to exist.) _clientCb = OperationContext.Current.GetCallbackChannel<IDxClientCb>(); _channel = OperationContext.Current.Channel; _duplexChannel = _channel as IOutputChannel; Debug.Print("Service IOutputChannel null: {0}", _duplexChannel == null); Similarly, in the client I have tried to cast the return value of DuplexChannelFactory.CreateChannel() to any of these interfaces and I always get back a null. How do I get a reference to one of these?

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• PHP float bug: PHP Hangs On Numeric Value

  - by jeroen

  I just read an interesting article about php hanging on certain float numbers, see The Register and Exploring Binary. I never explicitly use floats, I use number_format() to clean my input and display for example prices. Also, as far as I am aware, all input from for example forms are strings until I tell them otherwise so I am supposing that this problem does not affect me. Am I right, or do I need to check for example Wordpress and Squirrelmail installations on my server to see if they cast anything to float? Or better, grep all php files on my servers for float?

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• Perfectly reproducable select statement default ordering issue....

  - by Dave

  Hi, I've recently been chasing an issue with a client's db... solution found, but impossible to recreate. Essentially, we're doing a Select * from mytable where ArbitraryColumn = 75 Where MyTable has an Identity column, called 'MyIndentityColumn' - incremented by one in each insert. Naturally, and normally I would assume that the order returned would be the order in which they are inserted (bad assumption, but one which was forced onto me, through an inherited application - which has been patched). Essentially, I would like suggestions as to why the database, when restored to my local machine (same OS, same SQL server version - 200 sp3) same collation, and same backup instance restored on it, as a test DB on the client site. When I perform the above select, I get them in order of insert (i.e. identity column ordered ascending). On the client, it seems random (but the same 'random' order each time)... A few other points: I have the same collation on my test server as client Same DB backup restored to a test only I can access Same SQL server version and service pack Same OS Test DB is a new DB - new log and MDF... I have the problem 'solved' by adding an explicit order by clause but I want to undertand the cause of the issue, given the exact nature of my attempts to recreate it beuing futile, and perfectly recreatable on the client server... Thanks in advance, Dave

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• How can I join on a CSV varchar?

  - by mgroves

  I have a varchar field that contains a string like "10,11,12,13". How can I use that CSV string to join to another table with those IDs? Here's the approach I'm taking now: select * from SomeTable a WHERE (',' + @csvString + ',') LIKE '%,' + CONVERT(varchar(25), a.ID) + ',%' Where @csvString is "10,11,12,...". I intend to use this method as a join condition as well. That method works, but it's rather slow (using CAST doesn't improve the speed). I understand that having CSVs in the database like that is usually a very silly idea in most cases, but there's nothing I can do about that.

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• Postgres pgpass windows - not working

  - by Scott

  DB: Postgres 9.0 Client: Windows 7 Server Windows 2008, 64bit I'm trying to connect remotely to a postgres instance for purposes of performing a pg_dump to my local machine. Everything works from my client machine, except that I need to provide a password at the password prompt, and I'd ultimately like to batch this with a script. I've followed the instructions here: http://www.postgresql.org/docs/current/static/libpq-pgpass.html but it's not working. To recap, I've created a file on the client (and tried the server as well): C:/Users/postgres/AppData/postgresql/pgpass.conf, where postgresql is the db user. The file has one line with the following data: *:5432:*postgres:[mypassword] (also tried explicit ip/dbname values, all asterisks, and every combination in between. (I've also tried replacing each '*' with [localhost|myip] and [mydatabasename] respectively. From my client machine, I connect using: pg_dump -h [myip] -U postgres -w [mydbname] [mylocaldumpfile] I'm presuming that I need to provide the '-w' switch in order to ignore password prompt, at which point it should look in the AppData directory on the server. It just comes back with "connection to database failed: fe_sendauth: no password supplied. Any insights are appreciated. As a hack workaround, if there was a way I could tell the windows batch file on my client machine to inject the password at the postgres prompt, that would work as well. Thanks.

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• NASM shift operators

  - by Hudson Worden

  How would you go about doing a bit shift in NASM on a register? I read the manual and it only seems to mention these operators , <<. When I try to use them NASM complains about the shift operator working on scalar values. Can you explain what a scalar value is and give an example of how to use and <<. Also, I thought there were a shr or shl operators. If they do exist can you give an example of how to use them? Thank you for your time.

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• SQL Server Read Locking behavior

  - by Charles Bretana

  When SQL Server Books online says that "Shared (S) locks on a resource are released as soon as the read operation completes, unless the transaction isolation level is set to repeatable read or higher, or a locking hint is used to retain the shared (S) locks for the duration of the transaction." Assuming we're talking about a row-level lock, with no explicit transaction, at default isolation level (Read Committed), what does "read operation" refer to? The reading of a single row of data? The reading of a single 8k IO Page ? or until the the complete Select statement in which the lock was created has finished executing, no matter how many other rows are involved? NOTE: The reason I need to know this is we have a several second read-only select statement generated by a data layer web service, which creates page-level shared read locks, generating a deadlock due to conflicting with row-level exclusive update locks from a replication prcoess that keeps the server updated. The select statement is fairly large, with many sub-selects, and one DBA is proposing that we rewrite it to break it up into multiple smaller statements (shorter running pieces), "to cut down on how long the locks are held". As this assumes that the shared read locks are held till the complete select statement has finished, if that is wrong (if locks are released when the row, or the page is read) then that approach would have no effect whatsoever....

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