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• In Python, how can I find the index of the first item in a list that is NOT some value?

  - by Ryan B. Lynch

  Python's list type has an index(x) method. It takes a single parameter x, and returns the (integer) index of the first item in the list that has the value x. Basically, I need to invert the index(x) method. I need to get the index of the first value in a list that does NOT have the value x. I would probably be able to even just use a function that returns the index of the first item with a value != None. I can think of a 'for' loop implementation with an incrementing counter variable, but I feel like I'm missing something. Is there an existing method, or a one-line Python construction that can handle this? In my program, the situation comes up when I'm handling lists returned from complex regex matches. All but one item in each list have a value of None. If I just needed the matched string, I could use a list comprehension like '[x for x in [my_list] if x is not None]', but I need the index in order to figure out which capture group in my regex actually caused the match.

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• Accessing ViewController's variables from UIActionSheet delegate

  - by VansFannel

  Hello. I have the following code: @implementation SendMapViewController NSMutableArray *emails; At this method I create emails array and I add some NSStrings: - (BOOL) peoplePickerNavigationController: (ABPeoplePickerNavigationController *)peoplePicker shouldContinueAfterSelectingPerson: (ABRecordRef)person { ABMultiValueRef emailInfo = ABRecordCopyValue(person, kABPersonEmailProperty); NSUInteger emailCount = ABMultiValueGetCount(emailInfo); if (emailCount > 1) { UIActionSheet *emailsAlert = [[UIActionSheet alloc] initWithTitle:@"Select an email" delegate:self cancelButtonTitle:nil destructiveButtonTitle:nil otherButtonTitles:nil]; emails = [NSMutableArray arrayWithCapacity: emailCount]; for (NSUInteger i = 0; i < emailCount; i++) { NSString *emailFromContact = (NSString *)ABMultiValueCopyValueAtIndex(emailInfo, i); [emails addObject: emailFromContact]; [emailsAlert addButtonWithTitle:emailFromContact]; [emailFromContact release]; } [emailsAlert addButtonWithTitle:@"Cancel"]; [emailsAlert showInView:self.view]; [emailsAlert release]; } else { ... } CFRelease(emailInfo); [self dismissModalViewControllerAnimated:YES]; return NO; } As you can see in code, if there are more than one email I show and UIActionSheet. When user clicks on a button representing and email, I want to execute the following code: - (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex { if ([emails count] >= buttonIndex) { NSString *contactEmail = (NSString *)[emails objectAtIndex:buttonIndex]; ... } } But emails array hasn't got any email. What I'm doing wrong? I'm developing for iPhone.

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• How can I optimize retrieving lowest edit distance from a large table in SQL?

  - by Matt

  Hey, I'm having troubles optimizing this Levenshtein Distance calculation I'm doing. I need to do the following: Get the record with the minimum distance for the source string as well as a trimmed version of the source string Pick the record with the minimum distance If the min distances are equal (original vs trimmed), choose the trimmed one with the lowest distance If there are still multiple records that fall under the above two categories, pick the one with the highest frequency Here's my working version: DECLARE @Results TABLE ( ID int, [Name] nvarchar(200), Distance int, Frequency int, Trimmed bit ) INSERT INTO @Results SELECT ID, [Name], (dbo.Levenshtein(@Source, [Name])) As Distance, Frequency, 'False' As Trimmed FROM MyTable INSERT INTO @Results SELECT ID, [Name], (dbo.Levenshtein(@SourceTrimmed, [Name])) As Distance, Frequency, 'True' As Trimmed FROM MyTable SET @ResultID = (SELECT TOP 1 ID FROM @Results ORDER BY Distance, Trimmed, Frequency) SET @Result = (SELECT TOP 1 [Name] FROM @Results ORDER BY Distance, Trimmed, Frequency) SET @ResultDist = (SELECT TOP 1 Distance FROM @Results ORDER BY Distance, Trimmed, Frequency) SET @ResultTrimmed = (SELECT TOP 1 Trimmed FROM @Results ORDER BY Distance, Trimmed, Frequency) I believe what I need to do here is to.. Not dumb the results to a temporary table Do only 1 select from `MyTable` Setting the results right in the select from the initial select statement. (Since select will set variables and you can set multiple variables in one select statement) I know there has to be a good implementation to this but I can't figure it out... this is as far as I got: SELECT top 1 @ResultID = ID, @Result = [Name], (dbo.Levenshtein(@Source, [Name])) As distOrig, (dbo.Levenshtein(@SourceTrimmed, [Name])) As distTrimmed, Frequency FROM MyTable WHERE /* ... yeah I'm lost */ ORDER BY distOrig, distTrimmed, Frequency Any ideas?

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• Is this a bug in plist or Xcode?

  - by Pedro

  G'day All If you create a date item in the plist editor of Xcode or Apple's standalone plist editor you get something of the form <date>2010-05-29T10:30:00Z</date> which is a nice well formed ISO date at UTC (indicated by the "Z"). Because I'm in timezone UTC +10 when that's read into my app & then displayed I get 8:30 PM out, still good. However if that is a time in my timezone it should be <date>2010-05-29T10:30:00+10</date> (replacing "Z" with my timezone offset). All of my attempts at reading such dates into my iPhone app have had the plist rejected as if it is malformed & editing a plist with such a date in Apple's editors changed the "+10" to "Z" without adjusting the time. Do others think I'm correct in thinking this is a bug in either plist or Xcode? My feeling is that the implementation of ISO date & time in plist is incomplete. Cheers, Pedro :)

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• java 6 web services share domain specific classes between server and client

  - by user173446

  Hi all, Context: Considering below defined Engine class being parameter of some webservice method. As we have both server and client in java we may have some benefits (???) in sharing Engine class between server and client ( i.e we may put in a common jar file to be added to both client and server classpath ) Some benefits would be : we keep specific operations like 'brushEngine' in same place build is faster as we do not need in our case to generate java code for client classes but to use them from the server build) if we later change server implementation for 'brushEngine' this is reflected automatically in client . Questions: How to share below detailed Engine class using java 6 tools ( i.e wsimport , wsgen etc )? Is there other tools for java that can achieve this sharing ? Is sharing a case that java 6 web services support is missing ? Can this case be reduced to other web service usage patterns? Thanks. Code: public class Engine { private String engineData; public String getData(){ return data; } public setData(String value){ this.data = value; } public void brushEngine(){ engineData = "BrushedEngine"+engineData; } }

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• How do I mock a method with an open array parameter in PascalMock?

  - by Oliver Giesen

  I'm currently in the process of getting started with unit testing and mocking for good and I stumbled over the following method that I can't seem to fabricate a working mock implementation for: function GetInstance(const AIID: TGUID; out AInstance; const AArgs: array of const; const AContextID: TImplContextID = CID_DEFAULT): Boolean; (TImplContextID is just an alias for Integer) I thought it would have to look something like this: function TImplementationProviderMock.GetInstance( const AIID: TGUID; out AInstance; const AArgs: array of const; const AContextID: TImplContextID): Boolean; begin Result := AddCall('GetInstance') .WithParams([@AIID, AContextID]) .ReturnsOutParams([AInstance]) .ReturnValue; end; But the compiler complains about the .ReturnsOutParams([AInstance]) saying "Bad argument type in variable type array constructor.". Also I haven't found a way to specify the open array parameter AArgs at all. Also, is using the @-notation for the TGUID-typed parameter the right way to go? Is it possible to mock this method with the current version of PascalMock at all? Update: I now realize I got the purpose of ReturnsOutParams completely wrong: It's intended to be used for populating the values to be returned when defining the expectations rather than for mocking the call itself. I now think the correct syntax for mocking the out parameter would probably have to look more like this: function TImplementationProviderMock.GetInstance( const AIID: TGUID; out AInstance; const AArgs: array of const; const AContextID: TImplContextID): Boolean; var lCall: TMockMethod; begin lCall := AddCall('GetInstance').WithParams([@AIID, AContextID]); Pointer(AInstance) := lCall.OutParams[0]; Result := lCall.ReturnValue; end; The questions that remain are how to mock the open array parameter AArgs and whether passing the TGUID argument (i.e. a value type) by address will work out...

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• Cross-Platform Camera API

  - by Karim

  Hi, I'm now building a video transforming filter that have to transform video frames in real-time. One of the key requirements of the filter is to have high performance to minimize the number of dropped frames during the transform. Another requirement that is of lower priority but also nice to have is to make it cross-platform (both PC's and Mobile devices). The application is built in C++. Now my question is: is there any API that is more portable and has a similar or better performance characteristics than DirectShow? as DirectShow's portability is only limited to Windows-based devices (PCs and Windows Mobile&CE platforms). Also I've notices that for example using HTC's custom camera API has far better performance than what DirectShow offers. If you want to check this, try to build a filter in DirectShow that will multiply each color by 2 and render that in real-time from camera on the screen. Then do the same with HTC's API. There is almost 4-5x performance boost with vendor's specific API. So it'd be very nice if the library used the device-specific implementation of the driver, as performance is critical when doing this transforms on a mobile device (which is about ~500 MHz).

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• Strange inheritance behaviour in Objective-C

  - by Smikey

  Hi all, I've created a class called SelectableObject like so: #define kNumberKey @"Object" #define kNameKey @"Name" #define kThumbStringKey @"Thumb" #define kMainStringKey @"Main" #import <Foundation/Foundation.h> @interface SelectableObject : NSObject <NSCoding> { int number; NSString *name; NSString *thumbString; NSString *mainString; } @property (nonatomic, assign) int number; @property (nonatomic, retain) NSString *name; @property (nonatomic, retain) NSString *thumbString; @property (nonatomic, retain) NSString *mainString; @end So far so good. And the implementation section conforms to the NSCoding protocol as expected. HOWEVER, when I add a new class which inherits from this class, i.e. #import <Foundation/Foundation.h> #import "SelectableObject.h" @interface Pet : SelectableObject <NSCoding> { } @end I suddenly get the following compiler error in the Selectable object class! SelectableObject.h:16: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'interface' This makes no sense to me. Why is the interface declaration for the SelectableObject class suddenly broken? I also import it in a couple of other classes I've written... Any help would be very much appreciated. Thanks! Michael

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• fesetround with MSVC x64

  - by mr grumpy

  I'm porting some code to Windows (sigh) and need to use fesetround. MSVC doesn't support C99, so for x86 I copied an implementation from MinGW and hacked it about: //__asm__ volatile ("fnstcw %0;": "=m" (_cw)); __asm { fnstcw _cw } _cw &= ~(FE_TONEAREST | FE_DOWNWARD | FE_UPWARD | FE_TOWARDZERO); _cw |= mode; //__asm__ volatile ("fldcw %0;" : : "m" (_cw)); __asm { fldcw _cw } if (has_sse) { unsigned int _mxcsr; //__asm__ volatile ("stmxcsr %0" : "=m" (_mxcsr)); __asm { stmxcsr _mxcsr } _mxcsr &= ~ 0x6000; _mxcsr |= (mode << __MXCSR_ROUND_FLAG_SHIFT); //__asm__ volatile ("ldmxcsr %0" : : "m" (_mxcsr)); __asm { ldmxcsr _mxcsr } } The commented lines are the originals for gcc; uncommented for msvc. This appears to work. However the x64 cl.exe doesn't support inline asm, so I'm stuck. Is there some code out there I can "borrow" for this? (I've spent hours with Google). Or will I have to go on a 2 week detour to learn some assembly and figure out how to get/use MASM? Any advice is appreciated. Thank you.

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• WCF code generation for large/complex schema (HR-XML/OAGIS) - is there an alternative?

  - by Sasha Borodin

  Hello, and thank you for reading. I am implementing a WCF Service based on a predefined specification (HR-XML 3.0). As such, I am starting with the schema, and working my way back to code. There are a number of large Schema documents (which import yet more Schema documents) related to my implementation, provided by this specification. I am able to generate code using xsd.exe, by supplying the "main" and "supporting" xsd files as arguments. But there are several issues, and I am wondering if this is the right approach. there are litterally hundreds of classes - the code file is half a meg in size duplicate classes (ex. Type, Type1 - which both represent the same type) there are classes declared as inheriting from a base class, but that base class is not generated/defined I understand that there are limitations to the types of Schema supported by svcutil.exe/xsd.exe when targeting the DataContractSerializer and even XmlSerializer. My question is two-fold: Are code generation "issues" fairly common when dealing with larger, modular xsd files? Has anyone had success with generating data contracts from OAGIS or HR-XML schema? Given the above issues, are there better approaches to this task, avoiding generating code and working with concrete objects? Does it make better sence to read and compose a SOAP message directly, while still taking advantage of the rest of the WCF framework? I understand that I am loosing the convenience of working with .NET objects, and the framekwork-provided (de)serialization; given these losses, would it still be advantageous to base my Service on WCF? Is there some "middle ground" between working with .NET types and pure XML? Thank you very much! -Sasha Borodin DFWHC.org

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• Is Stream.Write thread-safe?

  - by Mike Spross

  I'm working on a client/server library for a legacy RPC implementation and was running into issues where the client would sometimes hang when waiting to a receive a response message to an RPC request message. It turns out the real problem was in my message framing code (I wasn't handling message boundaries correctly when reading data off the underlying NetworkStream), but it also made me suspicious of the code I was using to send data across the network, specifically in the case where the RPC server sends a large amount of data to a client as the result of a client RPC request. My send code uses a BinaryWriter to write a complete "message" to the underlying NetworkStream. The RPC protocol also implements a heartbeat algorithm, where the RPC server sends out PING messages every 15 seconds. The pings are sent out by a separate thread, so, at least in theory, a ping can be sent while the server is in the middle of streaming a large response back to a client. Suppose I have a Send method as follows, where stream is a NetworkStream: public void Send(Message message) { //Write the message to a temporary stream so we can send it all-at-once MemoryStream tempStream = new MemoryStream(); message.WriteToStream(tempStream); //Write the serialized message to the stream. //The BinaryWriter is a little redundant in this //simplified example, but here because //the production code uses it. byte[] data = tempStream.ToArray(); BinaryWriter bw = new BinaryWriter(stream); bw.Write(data, 0, data.Length); bw.Flush(); } So the question I have is, is the call to bw.Write (and by implication the call to the underlying Stream's Write method) atomic? That is, if a lengthy Write is still in progress on the sending thread, and the heartbeat thread kicks in and sends a PING message, will that thread block until the original Write call finishes, or do I have to add explicit synchronization to the Send method to prevent the two Send calls from clobbering the stream?

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• Values are not returning from MY SQL database to my java class

  - by sam

  Hi, This is my Query DELIMITER $$ DROP PROCEDURE IF EXISTSdiscoverdb.getuser_info$$ # MySQL returned an empty result set (i.e. zero rows). `CREATE PROCEDURE discoverdb.getuser_info ( IN name VARCHAR(100), IN pass VARCHAR(100) ) BEGIN SELECT * FROM ad_user WHERE sLogin = name AND sPassHash=password(pass); END $$ # MySQL returned an empty result set (i.e. zero rows). DELIMITER ; This is my calling method public Authentication getAuthentication (String username,String password) { //TODO write your implementation code here: Authentication ack = new Authentication(); try{ String simpleProc = "{ call getuser_infosam(?,?)}"; java.sql.CallableStatement cs = con.prepareCall(simpleProc); cs.setString(1, username); cs.setString(2, password); java.sql.ResultSet rs = cs.executeQuery(); while (rs.next()) { System.out.println(rs.getString("sLogin")); System.out.println(rs.getString("sPassHash")); System.out.println(rs.getString("sForename")); System.out.println(rs.getString("sName")); System.out.println(rs.getString("company")); System.out.println(rs.getString("sEmail")); rs.close();} }catch ( Exception e) { e.printStackTrace(); System.out.print(e); } return ack; }

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• Is there a practical benefit to casting a NULL pointer to an object and calling one of its member fu

  - by zdawg

  Ok, so I know that technically this is undefined behavior, but nonetheless, I've seen this more than once in production code. And please correct me if I'm wrong, but I've also heard that some people use this "feature" as a somewhat legitimate substitute of a lacking aspect of the current C++ standard, namely, the inability to obtain the address (well, offset really) of a member function. For example, this is out of a popular implementation of a PCRE (Perl-compatible Regular Expression) library: #ifndef offsetof #define offsetof(p_type,field) ((size_t)&(((p_type *)0)->field)) #endif One can debate whether the exploitation of such a language subtlety in a case like this is valid or not, or even necessary, but I've also seen it used like this: struct Result { void stat() { if(this) // do something... else // do something else... } }; // ...somewhere else in the code... ((Result*)0)->stat(); This works just fine! It avoids a null pointer dereference by testing for the existence of this, and it does not try to access class members in the else block. So long as these guards are in place, it's legitimate code, right? So the question remains: Is there a practical use case, where one would benefit from using such a construct? I'm especially concerned about the second case, since the first case is more of a workaround for a language limitation. Or is it? PS. Sorry about the C-style casts, unfortunately people still prefer to type less if they can.

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• On Render Callback For G+ Button

  - by Michael Robinson

  How might I go about performing an action only when a G+ button has finished rendering? Facebook allows one to do this using the following: FB.XFBML.parse(document, function() { alert('rendering done'); }); I've perused Google's documentation, but didn't see anything helpful. Currently my workaround is to monitor the G+ element until certain elements have been added, then perform my action: (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; po.onload = function() { var awaitRender = function(element) { if (element.firstChild && element.firstChild.firstChild && element.firstChild.firstChild.tagName.toUpperCase() === 'IFRAME') { alert('rendered!'); } else { window.setTimeout(function() { awaitRender(element) }, 100); } }; var buttons = document.getElementsByClassName('googleplus-button'); for(var i = 0; i < buttons.length; i++) { awaitRender(buttons[i]); } } var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })(); I'd like to know please, if there is either: A correct way one should do this for G+ buttons A better implementation that what I've hacked together above

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• Online file storage similar to Amazon S3

  - by Joel G

  I am looking to code a file storage application in perl similar to amazon s3. I already have a amazon s3 clone that I found online called parkplace but its in ruby and is old also isn't built for high loads. I am not really sure what modules and programs I should use so id like some help picking them out. My requirements are listed below (yes I know there are lots but I could start simple then add more once I get it going): Easy API implementation for client side apps. (maybe RESTful but extras like mkdir and cp (?) Centralized database server for the USERDB (maybe PostgreSQL (?). Logging of all connections, bandwidth used, well pretty much everything to a centralized server (maybe PostgreSQL again (?). Easy server side configuration (config file(s) stored on the servers). Web based control panel for admin(s) and user(s) to show logs. (could work just running queries from the databases) Fast High Uptime Low memory usage Some sort of load distribution/load balancer (maybe a dns based or pound or perlbal or something else (?). Maybe a cache of some sort (memcached or parlbal or something else (?). Thanks in advance

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• WCF REST adding data using POST or PUT 400 Bad Request

  - by user55474

  HI How do i add data using wcf rest architecture. I dont want to use the channelfactory to call my method. Something similar to the webrequest and webresponse used for GET. Something similar to the ajax WebServiceProxy restInvoke Or do i always have to use the Webchannelfactory implementation I am getting a 400 BAD request by using the following Dim url As String = "http://localhost:4475/Service.svc/Entity/Add" Dim req As WebRequest = WebRequest.Create(url) req.Method = "POST" req.ContentType = "application/xml; charset=utf-8" req.Timeout = 30000 req.Headers.Add("SOAPAction", url) Dim xEle As XElement xEle = <Entity xmlns:i="http://www.w3.org/2001/XMLSchema-instance"> <Name>Entity1</Name> </Entity> Dim sXML As String = xEle .Value req.ContentLength = sXML.Length Dim sw As New System.IO.StreamWriter(req.GetRequestStream()) sw.Write(sXML) sw.Close() Dim res as HttpWebResponse = req.GetResponse() Sercice Contract is as follows <OperationContract()> _ <WebInvoke(Method:="PUT", UriTemplate:="Entity/Add")> _ Function AddEntity(ByVal e1 As Entity) DataContract is as follows <Serializable()> _ <DataContract()> _ Public Class Entity private m_Name as String <DataMember()> _ Public Property Name() As String Get Return m_Name End Get Set(ByVal value As String) m_Name = value End Set End Property End Class thanks

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• creating matrix with probabilities

  - by John Chan

  Hi all, I want to generate a matrix of NxN to test some code that I have where each row contains floats as the elements and has to add up to 1 (i.e. a row with a set of probabilities). Where it gets tricky is that I want to make sure that randomly some of the elements should be 0 (in fact most of the elements should be 0 except for some random ones to be the probabilities). I need the probabilities to be 1/m where m is the number of elements that are not 0 within a single row. I tried to think of ways to output this, but essentially I would need this stored in a C++ array. So even if I output to a file I would still have the issue of not having it in array as I need it. At the end of it all I need that array because I want to generate a Market Matrix file. I found an implementation in C++ to take an array and convert it to the market matrix file, so this is what I am basing my findings on. My input for the rest of the code takes in this market matrix file so I need that to be the primary form of output. The language does not matter, I just want to generate the file at the end (I found a way mmwrite and mmread in python as well) Please help, I am stuck and not really sure how to implement this.

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• Web User Control og Event

  - by Mcoroklo

  I have a web user control, CreateQuestion.ascx, in ASP.NET. I want an event "QuestionAdded" to fire when a specific button is clicked. I don't want to send any data, I just want to know WHEN the button is fired. My implementation: CreateQuestion.ascx: public event EventHandler QuestionAdded; protected virtual void OnQuestionAdded(EventArgs e) { if (QuestionAdded != null) QuestionAdded(this, e); } /// This is the button I want to know when is fired protected void SubmitButton_Click(object sender, EventArgs e) { //question.Save(); this.OnQuestionAdded(new EventArgs()); } On the page AnswerQuestion.aspx, I use this: private void SetupControls(int myId) { CreateQuestionControl.QuestionAdded += new EventHandler(QuestionAdded); } private void QuestionAdded(object sender, EventArgs e) { Response.Write("HEJ KARL?"); } My problem No matter what, the event is never fired. I know that both SetupControls() is being run, and the code behind the button which should fire the event is run. When I debug, I can see the event QuestionAdded always are null. How do I make this work? Thanks a lot

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• java.sql.SQLException: Parameter index out of range (3 > number of parameters, which is 2)

  - by sam

  @WebMethod(operationName = "SearchOR") public SearchOR getSearchOR (@WebParam(name = "comp") String comp, @WebParam(name = "name") String name) { //TODO write your implementation code here: SearchOR ack = null; try{ String simpleProc = "{ call getuser_info_or(?,?)}"; CallableStatement cs = con.prepareCall(simpleProc); cs.setString(1, comp); cs.setString(2, name); ResultSet rs = cs.executeQuery(); System.out.print("2"); /* int i = 0, j = 0; if (rs.last()) { i = rs.getRow(); ack = new SearchOR[i]; rs.beforeFirst(); }*/ while (rs.next()) { // ack[j] = new SearchOR(rs.getString(1), rs.getString(2)); // j++; ve.add(rs.getString(1)); ve.add(rs.getString(2)); }}catch ( Exception e) { e.printStackTrace(); System.out.print(e); } return ack; } I am getting error at portion i have made bold.It is pointing to that location.My Query is here: DELIMITER $$ DROP PROCEDURE IF EXISTS discoverdb.getuser_info_or$$ MySQL returned an empty result set (i.e. zero rows). CREATE PROCEDURE discoverdb.getuser_info_or ( IN comp VARCHAR(100), IN name VARCHAR(100), OUT Login VARCHAR(100), OUT email VARCHAR(100) ) BEGIN SELECT sLogin, sEmail INTO Login, email FROM ad_user WHERE company = comp OR sName=name; END $$ MySQL returned an empty result set (i.e. zero rows). DELIMITER ;

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• Which plugin framework to use for native C++/Win32

  - by Kerido

  Hi everybody. I have an extensible product that allows 3rd party developers to extend it. The aspects that can be extended are documented and interfaces are provided in the SDK. Currently, I'm using COM and I'm getting pretty comfortable with it. I especially like the ability to provide interface versioning in a unified manner. I consider it to be a requirement because you never know what you're gonna need in the future. Just to be precise, here's an example. Let's suppose I have an interface representing a particular feature: class IFeature { public: virtual void DoFeatureTask() = 0; }; Then after the interface is already documented (and someone may have used it in the plugin code) I'm realizing, I need more from this feature. Maybe, there is an option I need to provide. I just define the second version: class IFeature2 { public: virtual void DoFeatureTask(int theOption) = 0; }; I don't mean I intend to have lots of versions. But it just may happen. In COM, because every interface is associated with a GUID, I can query a preferred implementation, determine its presence, and, finally, fall back to a legacy one. But after glancing through C++/COM-related questions, I noticed many recommendations against COM. So maybe it's not the best choice and I'm just too old-school. Can you advise on an alternative?

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• Safe and polymorphic toEnum

  - by jetxee

  I'd like to write a safe version of toEnum: safeToEnum :: (Enum t, Bounded t) => Int -> Maybe t A naive implementation: safeToEnum :: (Enum t, Bounded t) => Int -> Maybe t safeToEnum i = if (i >= fromEnum (minBound :: t)) && (i <= fromEnum (maxBound :: t)) then Just . toEnum $ i else Nothing main = do print $ (safeToEnum 1 :: Maybe Bool) print $ (safeToEnum 2 :: Maybe Bool) And it doesn't work: safeToEnum.hs:3:21: Could not deduce (Bounded t1) from the context () arising from a use of `minBound' at safeToEnum.hs:3:21-28 Possible fix: add (Bounded t1) to the context of an expression type signature In the first argument of `fromEnum', namely `(minBound :: t)' In the second argument of `(>=)', namely `fromEnum (minBound :: t)' In the first argument of `(&&)', namely `(i >= fromEnum (minBound :: t))' safeToEnum.hs:3:56: Could not deduce (Bounded t1) from the context () arising from a use of `maxBound' at safeToEnum.hs:3:56-63 Possible fix: add (Bounded t1) to the context of an expression type signature In the first argument of `fromEnum', namely `(maxBound :: t)' In the second argument of `(<=)', namely `fromEnum (maxBound :: t)' In the second argument of `(&&)', namely `(i <= fromEnum (maxBound :: t))' As well as I understand the message, the compiler does not recognize that minBound and maxBound should produce exactly the same type as in the result type of safeToEnum inspite of the explicit type declaration (:: t). Any idea how to fix it?

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• C# Fun with Generics - Mutual Dependencies

  - by Kenneth Cochran

  As an experiment I'm trying to write a generic MVP framework. I started with: public interface IPresenter<TView> where TView: IView<IPresenter<... { TView View { get; set;} } public interface IView<TPresenter> where TPresenter:IPresenter<IView<... { TPresenter Presenter { get; set; } } Obviously this can't work because the types of TView and TPresenter can't be resolved. You'd be writing Type<Type<... forever. So my next attempt looked like this: public interface IView<T> where T:IPresenter { ... } public interface IView:IView<IPresenter> { } public interface IPresenter<TView> where TView: IView { ... } public interface IPresenter: IPresenter<IView> { ... } This actually compiles and you can even inherit from these interfaces like so: public class MyView : IView, IView<MyPresenter> { ... } public class MyPresenter : IPresenter, IPresenter<MyView> { ... } The problem is in the class definition you have to define any members declared in the generic type twice. Not ideal but it still compiles. The problem's start creeping up when you actually try to access the members of a Presenter from a View or vice versa. You get an Ambiguous reference when you try to compile. Is there any way to avoid this double implementation of a member when you inherit from both interfaces? Is it even possible to resolve two mutually dependent generic types at compile time?

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• NSOperations or NSThread for bursts of smaller tasks that continuously cancel each other?

  - by RickiG

  Hi I would like to see if I can make a "search as you type" implementation, against a web service, that is optimized enough for it to run on an iPhone. The idea is that the user starts typing a word; "Foo", after each new letter I wait XXX ms. to see if they type another letter, if they don't, I call the web service using the word as a parameter. The web service call and the subsequent parsing of the result I would like to move to a different thread. I have written a simple SearchWebService class, it has only one public method: - (void) searchFor:(NSString*) str; This method tests if a search is already in progress (the user has had a XXX ms. delay in their typing) and subsequently stops that search and starts a new one. When a result is ready a delegate method is called: - (NSArray*) resultsReady; I can't figure out how to get this functionality 'threaded'. If I keep spawning new threads each time a user has a XXX ms. delay in the typing I end up in a bad spot with many threads, especially because I don't need any other search, but the last one. Instead of spawning threads continuously, I have tried keeping one thread running in the background all the time by: - (void) keepRunning { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; SearchWebService *searchObj = [[SearchWebService alloc] init]; [[NSRunLoop currentRunLoop] run]; //keeps it alive [searchObj release]; [pool release]; } But I can't figure out how to access the "searchFor" method in the "searchObj" object, so the above code works and keeps running. I just can't message the searchObj or retrieve the resultReady objects? Hope someone could point me in the right direction, threading is giving me grief:) Thank you.

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• Rtti data manipulation and consistency in Delphi 2010

  - by Coco

  Has anyone an idea, how I can make TValue using a reference to the original data? In my serialization project, I use (as suggested in XML-Serialization) a generic serializer which stores TValues in an internal tree-structure (similar to the MemberMap in the example). This member-tree should also be used to create a dynamic setup form and manipulate the data. My idea was to define a property for the Data: TDataModel <T> = class {...} private FData : TValue; function GetData : T; procedure SetData (Value : T); public property Data : T read GetData write SetData; end; The implementation of the GetData, SetData Methods: procedure TDataModel <T>.SetData (Value : T); begin FData := TValue.From <T> (Value); end; procedure TDataModel <T>.GetData : T; begin Result := FData.AsType <T>; end; Unfortunately, the TValue.From method always makes a copy of the original data. So whenever the application makes changes to the data, the DataModel is not updated and vice versa if I change my DataModel in a dynamic form, the original data is not affected. Sure I could always use the Data property before and after changing anything, but as I use lot of Rtti inside my DataModel, I do not realy want to do this anytime. Perhaps someone has a better suggestion?

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• Animation is slow on iPhone

  - by Anthony Chan

  I'm developing an app that would display images and change them according to the user's action. I've created a subclass of UIView to contain an image, an index number and an array of image names. The code is like this: @interface CustomPic : UIView { UIImageView *pic; NSInteger index; NSMutableArray *picNames; //<-- an array of NSString } And in the implementation part, it has a method to change the image using a dissolve effect. - (void)nextPic { index++; if (index >= [picNames count]) { index = 0; } UIImageView *temp = pic; pic.image = [UIImage imageNamed:[picNames objectAtIndex:index]]; temp.alpha = 0; [UIView beginAnimations:nil context:nil]; [UIView setAnimationCurve:UIViewAnimationCurveEaseOut]; [UIView setAnimationDuration:0.25]; pic.alpha = 0; temp.alpha = 1; [UIView commitAnimations]; } In the viewController, there are several CustomPic which would change the images depends on users' choice. The images would change as expected with the fade in/out effect, but the animation performance is really bad. I've tested it on an iPhone 3G, the Instruments shows that the animation is only 2-3FPS! I tried many methods to simplify and modify the codes but with no hope. Is there something wrong in my code or in my concept? Thanks for any help. P.S. all the images are 320*480 PNGs with a max size of 15KB.

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