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• Is the Windows dev environment worth the cost?

  - by MCS

  I recently made the move from Linux development to Windows development. And as much of a Linux enthusiast that I am, I have to say - C# is a beautiful language, Visual Studio is terrific, and now that I've bought myself a trackball my wrist has stopped hurting from using the mouse so much. But there's one thing I can't get past: the cost. Windows 7, Visual Studio, SQL Server, Expression Blend, ViEmu, Telerik, MSDN - we're talking thousands for each developer on the project! You're definitely getting something for your money - my question is, is it worth it? [Not every developer needs all the aforementioned tools - but have you ever heard of anyone writing C# code without Visual Studio? I've worked on pretty large software projects in Linux without having to pay for any development tool whatsoever.] Now obviously, if you're already a Windows shop, it doesn't pay to retrain all your developers. And if you're looking to develop a Windows desktop app, you just can't do that in Linux. But if you were starting a new web application project and could hire developers who are experts in whatever languages you want, would you still choose Windows as your development platform despite the high cost? And if yes, why?

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• Checked status not updated in CheckBox template

  - by Simon

  Hey there. I'm trying to create an hyperlink that changes its text depending on a boolean value. I thought I could leverage the IsChecked method of a CheckBox. So I wrote this ControlTemplate for a CheckBox: <CheckBox Checked="CheckBox_Checked" IsChecked="{Binding Path=SomeBool, Mode=TwoWay}"> <CheckBox.Template> <ControlTemplate TargetType="{x:Type CheckBox}"> <BulletDecorator> <BulletDecorator.Bullet> <TextBlock> <Hyperlink> <TextBlock x:Name="TextBoxHyperlink">Unchecked</TextBlock> </Hyperlink> </TextBlock> </BulletDecorator.Bullet> <ContentPresenter /> </BulletDecorator> <ControlTemplate.Triggers> <Trigger Property="IsChecked" Value="True"> <Setter TargetName="TextBoxHyperlink" Property="Text" Value="Checked" /> </Trigger> </ControlTemplate.Triggers> </ControlTemplate> </CheckBox.Template> </CheckBox> But when I click on the hyperlink, nothing happens. The checked status is not changed and the Text property of the TextBlock is not updated. Any ideas?

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• Sensible unit test possible?

  - by nkr1pt

  Could a sensible unit test be written for this code which extracts a rar archive by delegating it to a capable tool on the host system if one exists? I can write a test case based on the fact that my machine runs linux and the unrar tool is installed, but if another developer who runs windows would check out the code the test would fail, although there would be nothing wrong with the extractor code. I need to find a way to write a meaningful test which is not binded to the system and unrar tool installed. How would you tackle this? public class Extractor { private EventBus eventBus; private ExtractCommand[] linuxExtractCommands = new ExtractCommand[]{new LinuxUnrarCommand()}; private ExtractCommand[] windowsExtractCommands = new ExtractCommand[]{}; private ExtractCommand[] macExtractCommands = new ExtractCommand[]{}; @Inject public Extractor(EventBus eventBus) { this.eventBus = eventBus; } public boolean extract(DownloadCandidate downloadCandidate) { for (ExtractCommand command : getSystemSpecificExtractCommands()) { if (command.extract(downloadCandidate)) { eventBus.fireEvent(this, new ExtractCompletedEvent()); return true; } } eventBus.fireEvent(this, new ExtractFailedEvent()); return false; } private ExtractCommand[] getSystemSpecificExtractCommands() { String os = System.getProperty("os.name"); if (Pattern.compile("linux", Pattern.CASE_INSENSITIVE).matcher(os).find()) { return linuxExtractCommands; } else if (Pattern.compile("windows", Pattern.CASE_INSENSITIVE).matcher(os).find()) { return windowsExtractCommands; } else if (Pattern.compile("mac os x", Pattern.CASE_INSENSITIVE).matcher(os).find()) { return macExtractCommands; } return null; } }

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• Using C#, can you drag a canvas in WPF?

  - by TERACytE

  Can you drag a canvas in WPF? How do you set the position of the canvas? Here is what I got so far: /// xaml <Window x:Class="TestApp.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Height="350" Width="525" WindowStyle="None" ResizeMode="NoResize" AllowsTransparency="True" Background="Transparent" Loaded="MainWindow_Loaded"> <Canvas Name="ParentCanvas" Background="#FF6E798D"> </Canvas> </Window> /// code behind public partial class MainWindow : Window { private Boolean isMouseCapture; public MainWindow() { InitializeComponent(); } void MainWindow_Loaded(object sender, RoutedEventArgs e) { this.ParentCanvas.MouseLeftButtonDown += new MouseButtonEventHandler(_MouseLeftButtonDown); this.ParentCanvas.MouseLeftButtonUp += new MouseButtonEventHandler(_MouseLeftButtonUp); this.ParentCanvas.MouseMove += new MouseEventHandler(_MouseMove); } void _MouseLeftButtonUp(object sender, MouseButtonEventArgs e) { this.ParentCanvas.ReleaseMouseCapture(); isMouseCapture = false; } void _MouseLeftButtonDown(object sender, MouseButtonEventArgs e) { this.ParentCanvas.CaptureMouse(); isMouseCapture = true; } void _MouseMove(object sender, MouseEventArgs e) { if (isMouseCapture) { this.ParentCanvas.X= e.GetPosition(this).X; this.ParentCanvas.Y = e.GetPosition(this).Y; } } } 'X' is not a property of Canvas (i.e."this.ParentCanvas.X"). What do I use to set the position?

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• Problems by inserting values from textboxes

  - by simon

  I'm trying to insert the current date to the database and i allways get the message(when i press the button on the form to save to my access database), that the data type is incorect in the conditional expression. the code: string conString = "Provider=Microsoft.Jet.OLEDB.4.0;" + "Data Source=C:\\Users\\Simon\\Desktop\\save.mdb"; OleDbConnection empConnection = new OleDbConnection(conString); string insertStatement = "INSERT INTO obroki_save " + "([ID_uporabnika],[ID_zivila],[skupaj_kalorij]) " + "VALUES (@ID_uporabnika,@ID_zivila,@skupaj_kalorij)"; OleDbCommand insertCommand = new OleDbCommand(insertStatement, empConnection); insertCommand.Parameters.Add("@ID_uporabnika", OleDbType.Char).Value = users.iDTextBox.Text; insertCommand.Parameters.Add("@ID_zivila", OleDbType.Char).Value = iDTextBox.Text; insertCommand.Parameters.Add("@skupaj_kalorij", OleDbType.Char).Value = textBox1.Text; empConnection.Open(); try { int count = insertCommand.ExecuteNonQuery(); } catch (OleDbException ex) { MessageBox.Show(ex.Message); } finally { empConnection.Close(); textBox1.Clear(); textBox2.Clear(); textBox3.Clear(); textBox4.Clear(); textBox5.Clear(); } I have now cut out the date,( i made access paste the date ), still there is the same problem. Is the first line ok? users.idtextbox.text? Please help !

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• Post method in Servlet is not being called again after being executed once

  - by SaurabhCsIITKgp

  I am implementing a database based web application using servlets. Now, when I input a parameter using a form in the jsp page, it redirects it to a servlet which subsequently adds the value to the database (the servlet creates a new table if the table doesn't already exist). The creation of the table and the addition of value works fine if the table doesn't already exists. Once it is created however and the parameter is inputted again in the form, the submit button no longer redirects it to the servlet. Nor is the value added to the database. Kindly advise me as to where I am going wrong. Following are the snippets of my code: From the JSP page (/showmanager is the urlpattern of the servlet): <form action="showmanager" method="post"> <h3>Enter name of the show: </h3> <input type="text" name="showname" value=""> <input type="hidden" name="task" value="addshow" /> <input type="button" value="Add Show"> </form> From the servlet (POST method): p rotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { if(request.getParameter("task").equals("addshow")){ this.addShow(request.getParameter("showname")); response.sendRedirect("showmanager.jsp"); } } Method to add in database: protected boolean addShow(String showname){ try{ statement =con.prepareStatement("INSERT INTO showdb10(name) VALUES ('"+showname+"')"); if(statement.executeUpdate()>0){ return true; } } catch(Exception e) { try{ statement =con.prepareStatement("create table showdb10 (id int NOT NULL AUTO_INCREMENT, name varchar(255) NOT NULL, date varchar(20),time varchar(20), b_total int, o_total int, b_avbl int, o_avbl int, b_price double(10,2), o_price double(10,2), seat_no varchar(20), transaction_id varchar(255), total_sales double(10,2), paymnt_artists double(10,2), paymnt_othr double(10,2), flag varchar(20), PRIMARY KEY(id))"); statement.executeUpdate(); statement =con.prepareStatement("INSERT INTO showdb10(name) VALUES ('"+showname+"')"); if(statement.executeUpdate()>0){ return true; } }catch(Exception e2){} } return false; }

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• Update mapping table in Linq

  - by Gary McGill

  I have a table Customers with a CustomerId field, and a table of Publications with a PublicationId field. Finally, I have a mapping table CustomersPublications that records which publications a customer can access - it has two fields: CustomerId field PublicationId. For a given customer, I want to update the CustomersPublications table based on a list of publication ids. I want to remove records in CustomersPublications where the PublicationId is not in the list, and add new records where the PublicationId is in the list but not already in the table. This would be easy in SQL, but I can't figure out how to do it in Linq. For the delete part, I tried: var recordsToDelete = dataContext.CustomersPublications.Where ( cp => (cp.CustomerId == customerId) && ! publicationIds.Contains(cp.PublicationId) ); dataContext.CustomersPublications.DeleteAllOnSubmit(recordsToDelete); ... but that didn't work. I got an error: System.NotSupportedException: Method 'Boolean Contains(Int32)' has no supported translation to SQL So, I tried using Any(), as follows: var recordsToDelete = dataContext.CustomersPublications.Where ( cp => (cp.CustomerId == customerId) && ! publicationIds.Any(p => p == cp.PublicationId) ); ... and this just gives me another error: System.NotSupportedException: Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains() operator Any pointers? [I have to say, I find Linq baffling (and frustrating) for all but the simplest queries. Better error messages would help!]

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• Row Source - combo box, filtering what pops up in a combo box by date

  - by primus285

  so I have a combo box that I want to pop up when somebody wants to search by year. It will allow them to see in that combo box only results that happened in a certain year. so far I have something like SELECT DISTINCT Database_New.ASEC FROM Database_New WHERE (((Database_New.Date) >= DateValue('01/01/2001') AND (((Database_New.Date) <= DateValue('12/031/2001'))); or SELECT DISTINCT Database_New.ASEC FROM Database_New WHERE (((Database_New.Date) >= BETWEEN DateValue('01/01/2001') AND DateValue('12/31/2001’))); as you can see, the kicker is that I am already sorting the thing with SELECT DISTINCT under the ASEC field. But I want to filter it one more by year so a whole bunch of ASEC values that didnt happen in that year (and there are quite a few that happen rarely, or would onyl be associeted with one year) do not pop up as avalible. so far I get an error like "Syntax error in query expression '(((Database_New.Date) = DateValue('01/01/2001') AND (((Database_New.Date) <= DateValue('12/031/2001')))' and I am a VBA person, not quite as good at debuggin SQL. Is it something easy? or will it simply not work the way I have it set up.

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• SQL query in JSP file pulling variable from VXML file

  - by s1066

  Hi I'm trying to get an SQL query to work within a JSP file. The JSP file is pulled by a VXML file here is my JSP file code: <?xml version="1.0"?> <%@ page import="java.util.*" %> <%@ page import="java.sql.*" %> <% boolean success = true; // Always optimistic String info = ""; String schoolname = request.getParameter("schoolname"); String informationtype = request.getParameter("informationtype"); try { Class.forName("org.postgresql.Driver"); String connectString = "jdbc:postgresql://localhost:5435/N0176359"; String user = "****"; String password = "*****"; Connection conn = DriverManager.getConnection(connectString, user, password); Statement st = conn.createStatement(); ResultSet rsvp = st.executeQuery("SELECT * FROM lincolnshire_school_information_new WHERE school_name=\'"+schoolname+"\'"); rsvp.next(); info = rsvp.getString(2); }catch (ClassNotFoundException e) { success = false; // something went wrong } %> As you can see I'm trying to insert the value of the variable declared as "schooname" into the end of the SQL query. However when I come to run the jsp file it doesn't work and I get an error "ResultSet not positioned properly". When I put a standard query in (without trying to make it value of the variable it works fine) Hope that makes sense, and thank you for any help!

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• What's wrong with this code

  - by javacode

  I am getting the compiler error. Can anybody debug this? import javax.mail.*; import javax.mail.internet.*; import java.util.*; public class SendMail { public static void main(String [] args) { SendMail sm=new SendMail(); sm.postMail("[email protected]","hi","hello","[email protected]"); } public void postMail( String recipients[ ], String subject, String message , String from) throws MessagingException { boolean debug = false; //Set the host smtp address Properties props = new Properties(); props.put("mail.smtp.host", "webmail.emailmyname.com"); // create some properties and get the default Session Session session = Session.getDefaultInstance(props, null); session.setDebug(debug); // create a message Message msg = new MimeMessage(session); // set the from and to address InternetAddress addressFrom = new InternetAddress(from); msg.setFrom(addressFrom); InternetAddress[] addressTo = new InternetAddress[recipients.length]; for (int i = 0; i < recipients.length; i++) { addressTo[i] = new InternetAddress(recipients[i]); } msg.setRecipients(Message.RecipientType.TO, addressTo); // Optional : You can also set your custom headers in the Email if you Want msg.addHeader("MyHeaderName", "myHeaderValue"); // Setting the Subject and Content Type msg.setSubject(subject); msg.setContent(message, "text/plain"); Transport.send(msg); } }

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• If the address of a function can not be resolved during deduction, is it SFINAE or a compiler error?

  - by Faisal Vali

  In C++0x SFINAE rules have been simplified such that any invalid expression or type that occurs in the "immediate context" of deduction does not result in a compiler error but rather in deduction failure (SFINAE). My question is this: If I take the address of an overloaded function and it can not be resolved, is that failure in the immediate-context of deduction? (i.e is it a hard error or SFINAE if it can not be resolved)? Here is some sample code: struct X { // template T* foo(T,T); // lets not over-complicate things for now void foo(char); void foo(int); }; template struct S { template struct size_map { typedef int type; }; // here is where we take the address of a possibly overloaded function template void f(T, typename size_map::type* = 0); void f(...); }; int main() { S s; // should this cause a compiler error because 'auto T = &X::foo' is invalid? s.f(3); } Gcc 4.5 states that this is a compiler error, and clang spits out an assertion violation. Here are some more related questions of interest: Does the FCD-C++0x clearly specify what should happen here? Are the compilers wrong in rejecting this code? Does the "immediate-context" of deduction need to be defined a little better? Thanks!

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• Can I print an HTMLLoader (pdf) in Adobe Air?

  - by Stephano

  I'm using AlivePDF to create a PDF file, then save it to the desktop. I can then use an HTMLLoader to display my lovely PDF file. Now, the print button in Adobe Reader works fine. However, there will be young children using the app, so I'd like to have a big "Print" button right above it. I figured I could just start up a print job and feed it my HTMLLoader. Am I doing something wrong here, cause I can't seem to get any output? note: variable "stuff" below is my HTMLLoader. I also have access to the PDF file if that comes in handy. private function print():void { var myPrintJob:PrintJob=new PrintJob(); var result:Boolean=myPrintJob.start(); if (result && stuff != null) { var rect:Rectangle=new Rectangle(0, 0, 2550, 3300); var opt:PrintJobOptions=new PrintJobOptions(true); myPrintJob.addPage(stuff, rect, opt); myPrintJob.send(); } else { //User does not have printer or user canceled print action } }

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• Can I print an HTMLLoader (pdf) in Adobe Air?

  - by Stephano

  I'm using AlivePDF to create a PDF file, then save it to the desktop. I can then use an HTMLLoader to display my lovely PDF file. Now, the print button in Adobe Reader works fine. However, there will be young children using the app, so I'd like to have a big "Print" button right above it. I figured I could just start up a print job and feed it my HTMLLoader. Am I doing something wrong here, cause I can't seem to get any output? note: variable "stuff" below is my HTMLLoader. I also have access to the PDF file if that comes in handy. private function print():void { var myPrintJob:PrintJob=new PrintJob(); var result:Boolean=myPrintJob.start(); if (result && stuff != null) { var rect:Rectangle=new Rectangle(0, 0, 2550, 3300); var opt:PrintJobOptions=new PrintJobOptions(true); myPrintJob.addPage(stuff, rect, opt); myPrintJob.send(); } else { //User does not have printer or user canceled print action } }

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• Set fields with instrospection - Problem with String.valueOf(String)

  - by fabb

  Hey there! I'm setting public fields of the Object 'this' via reflection. Both the field name and the value are given as String. I use several various field types: Boolean, Integer, Float, Double, an own enum, and a String. It works with all of them except with a String. The exception that gets thrown is that no method with the Signature String.valueOf(String) exists... Now I use a dirty instanceof workaround to detect if each field is a String and in that case just copy the value to the field. private void setField(String field, String value) throws Exception { Field wField = this.getClass().getField(field); if(wField.get(this) instanceof String){ //TODO dirrrrty hack //stupid workaround as java.lang.String.valueOf(java.lang.String) fails... wField.set(this, value); }else{ Method parseMethod = wField.getType().getMethod("valueOf", new Class[]{String.class}); wField.set(this, parseMethod.invoke(wField, value)); } } Any ideas how to avoid that workaround? Do you think java.lang.String should support the method valueOf(String)? thanks, fabb

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• How to remove a status message added by the seam security module?

  - by Joshua

  I would like to show a different status message, when a suspended user tries to login. If the user is active we return true from the authenticate method, if not we add a custom StatusMessage message mentioning that the "User X has been suspended". The underlying Identity authentication also fails and adds a StatusMessage. I tried removing the seam generated statusMessage with the following methods, but it doesn't seem to work and shows me 2 different status messages (my custom message, seam generated). What would be the issue here? StatusMessages statusMessages; statusMessages.clear() statusMessages.clearGlobalMessages() statusMessages.clearKeyedMessages(id) EDIT1: public boolean authenticate() { log.info("Authenticating {0}", identity.getCredentials().getUsername()); String username = identity.getCredentials().getUsername(); String password = identity.getCredentials().getPassword(); // return true if the authentication was // successful, false otherwise try { Query query = entityManager.createNamedQuery("user.by.login.id"); query.setParameter("loginId", username); // only active users can log in query.setParameter("status", "ACTIVE"); currentUser = (User)query.getSingleResult(); } catch (PersistenceException ignore) { // Provide a status message for the locked account statusMessages.clearGlobalMessages(); statusMessages.addFromResourceBundle( "login.account.locked", new Object[] { username }); return false; } IdentityManager identityManager = IdentityManager.instance(); if (!identityManager.authenticate(username, "password")) { return false; } else { log.info("Authenticated user {0} successfully", username); } }

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• SubSonic generated code and always filtering records

  - by cmroanirgo

  Hi, I have a table called "Users" that has a column called "deleted", a boolean indicating that the user is "Deleted" from the system (without actually deleting it, of course). I also have a lot of tables that have a FK to the Users.user_id column. Subsonic generates (very nicely) the code for all the foreign keys in a similar manner: public IQueryable<person> user { get { var repo=user.GetRepo(); return from items in repo.GetAll() where items.user_id == _user_id select items; } } Whilst this is good and all, is there a way to generate the code in such a way to always filter out the "Deleted" users too? In the office here, the only suggestion we can think of is to use a partial class and extend it. This is obviously a pain when there are lots and lots of classes using the User table, not to mention the fact that it's easy to inadvertently use the wrong property (User vs ActiveUser in this example): public IQueryable<User> ActiveUser { get { var repo=User.GetRepo(); return from items in repo.GetAll() where items.user_id == _user_id and items.deleted == 0 select items; } } Any ideas?

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• Loading 2 Singletons With Dependencies when an app is opened (appDelegate / appDidBecomeActive) iPhone SDK

  - by taber

  I'm trying to load two standard-issue style singletons: http://cocoawithlove.com/2008/11/singletons-appdelegates-and-top-level.html when my iPhone app is loaded. Here's my code: - (void) applicationDidFinishLaunching:(UIApplication *)application { // first, restore user prefs [AppState loadState]; // then, initialize the camera [[CameraModule sharedCameraModule] initCamera]; } My "camera module" has code that checks a property of the AppState singleton. But I think what's happening is a race condition where the camera module singleton is trying to access the AppState property while it's in the middle of being initialized (so the property is nil, and it's re-initializing AppState). I'd really like to keep these separate, instead of just throwing one (or both) into the App Delegate. Has anyone else seen something like this? What kind of workaround did you use, or what would you suggest? Thanks in advance! Here's the loadState method: + (void)loadState { @synchronized([AppState class]) { NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; NSString *file = [documentsDirectory stringByAppendingPathComponent:@"prefs.archive"]; Boolean saveFileExists = [[NSFileManager defaultManager] fileExistsAtPath:file]; if(saveFileExists) { sharedAppState = [[NSKeyedUnarchiver unarchiveObjectWithFile:file] retain]; } else { [AppState sharedAppState]; } } }

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• PHP regex - find and replace

  - by jay

  Hi, I am trying to do this regex match and replace but not able to do it. Example <SPAN class="one">first content here</SPAN> <SPAN class="two">second content here </SPAN> <SPAN class="three">one; two; three; and more.</span> <SPAN class="four">more content here.</span> I want to find each set of the span tags and replace with something like this Find <SPAN class="one">first content here</SPAN> Change to <one>first content here</one> same way the the rest of the span tags. class="one", class="two" and so on are the only key identifier which I use in the regex match expression. So if I find a span tag with these class then I want to do the replace. My main issue is that I am not able to find the occurrence of first closing tag so what it does is it finds from the start to end which is of no use. So far I have been trying to do this using notepad++ but just found that it has its limitations so any php help would be appreciated. regards

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• Return an Oracle Associative Array from a function

  - by Paul Johnson

  Does anybody know if it is possible to return an associative array as the result of an Oracle function, if so do you have any examples? I have an Oracle package which contains an associative array declaration as defined below: TYPE EVENTPARAM IS TABLE OF NUMBER INDEX BY BINARY_INTEGER; This is then used in a stored procedure outside the package as follows: v_CompParams areva_interface.eventparam; The intention is to store an associative array of strings in the variable v_CompParams, returned from a Parse function in another package. The definition for which is as follows: PACKAGE STRING_MANIP IS TYPE a_array IS TABLE OF NUMBER INDEX BY BINARY_INTEGER; FUNCTION Parse (v_string VARCHAR2, v_delim VARCHAR2) RETURN a_array; FUNCTION RowCount(colln IN a_array) RETURN NUMBER; END; The code which implements this is: v_CompParams := STRING_MANIP.PARSE(v_CompID,v_Delim); Unfortunately it doesn't work, I get the error 'PLS-00382: expression is of wrong type'. I foolishly assumed, that since a_array derives from the same source Oracle type as the variable v_CompParams, that there would be no problem casting between them. Any help much appreciated. Kind Regards Paul J.

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• Authorization and Jquery dialog problem.

  - by bbrepols

  Hi, I have a little problem with a Jquery dialog for an action that requires a role. In my example, the user can click on a delete button and must confirm the action. In my controller, the Delete action requires a role, if the user is in the required role, the object is deleted. The problem: How to alert the user if * the element was deleted (redirect to the Index view) * there was an error (alert with the message) * he doesn't have the rights to delete (alert with the message) Before using the authorize filter, the delete action returned a JSON with a Boolean that indicates if there was an error, an URL to redirect on success and a message to alert on error. As I can't return a JSON from my filter, I created an other method with the authorize filter that returns a partial view with the confirm content. If the user doesn't have the rights, the filter returns a partial view with an unauthorized exception content. The problem: How to distinct which partial view was returned. When I create the dialog, I need to know for the buttons function. Thanks!

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• Subqueries on Java GAE Datastore

  - by Dmitry

  I am trying to create a database of users with connection between users (friends list). There are 2 main tables: UserEntity (main field id) and FriendEntity with fields: - initiatorId - id of user who initiated the friendship - friendId - id of user who has been invited. Now I am trying to fetch all friends of one particular user and encountered some problems with using subqueries in JDO here. Logically the query should be something like this: SQL: SELECT * FROM UserEntity WHERE EXISTS (SELECT * FORM FriendEntity WHERE (initiatorId == UserEntity.id && friendId == userId) || (friendId == UserEntity.id && initiatorId == userId)) or SELECT * FROM UserEntity WHERE userId IN (SELECT * FROM FriendEntity WHERE initiatorId == UserEntity.id) OR userId IN (SELECT * FROM FriendEntity WHERE friendId == UserEntity.id) So to replicate the last query in JDOQL, I tried to do the following: Query friendQuery = pm.newQuery(FriendEntity.class); friendQuery.setFilter("initiatorId == uidParam"); friendQuery.setResult("friendId"); Query initiatorQuery = pm.newQuery(FriendEntity.class); initiatorQuery.setFilter("friendId == uidParam"); initiatorQuery.setResult("initiatorId"); Query query = pm.newQuery(UserEntity.class); query.setFilter("initiatorQuery.contains(id) || friendQuery.contains(id)"); query.addSubquery(initiatorQuery, "List initiatorQuery", null, "String uidParam"); query.addSubquery(friendQuery, "List friendQuery", null, "String uidParam"); query.declareParameters("String uidParam"); List<UserEntity> friends = (List<UserEntity>) query.execute(userId); In result I get the following error: Unsupported method while parsing expression. Could anyone help with this query please?

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• Can parser combinators be made efficient?

  - by Jon Harrop

  Around 6 years ago, I benchmarked my own parser combinators in OCaml and found that they were ~5× slower than the parser generators on offer at the time. I recently revisited this subject and benchmarked Haskell's Parsec vs a simple hand-rolled precedence climbing parser written in F# and was surprised to find the F# to be 25× faster than the Haskell. Here's the Haskell code I used to read a large mathematical expression from file, parse and evaluate it: import Control.Applicative import Text.Parsec hiding ((<|>)) expr = chainl1 term ((+) <$ char '+' <|> (-) <$ char '-') term = chainl1 fact ((*) <$ char '*' <|> div <$ char '/') fact = read <$> many1 digit <|> char '(' *> expr <* char ')' eval :: String -> Int eval = either (error . show) id . parse expr "" . filter (/= ' ') main :: IO () main = do file <- readFile "expr" putStr $ show $ eval file putStr "\n" and here's my self-contained precedence climbing parser in F#: let rec (|Expr|) (P(f, xs)) = Expr(loop (' ', f, xs)) and loop = function | ' ' as oop, f, ('+' | '-' as op)::P(g, xs) | (' ' | '+' | '-' as oop), f, ('*' | '/' as op)::P(g, xs) -> let h, xs = loop (op, g, xs) let op = match op with | '+' -> (+) | '-' -> (-) | '*' -> (*) | '/' -> (/) loop (oop, op f h, xs) | _, f, xs -> f, xs and (|P|) = function | '('::Expr(f, ')'::xs) -> P(f, xs) | c::xs when '0' <= c && c <= '9' -> P(int(string c), xs) My impression is that even state-of-the-art parser combinators waste a lot of time back tracking. Is that correct? If so, is it possible to write parser combinators that generate state machines to obtain competitive performance or is it necessary to use code generation?

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• Webpage data scraping using Java

  - by Gemma

  I am now trying to implement a simple HTML webpage scraper using Java.Now I have a small problem. Suppose I have the following HTML fragment. <div id="sr-h-left" class="sr-comp"> <a class="link-gray-underline" id="compare_header" rel="nofollow" href="javascript:i18nCompareProd('/serv/main/buyer/ProductCompare.jsp?nxtg=41980a1c051f-0942A6ADCF43B802');"> <span style="cursor: pointer;" class="sr-h-o">Compare</span> </a> </div> <div id="sr-h-right" class="sr-summary"> <div id="sr-num-results"> <div class="sr-h-o-r">Showing 1 - 30 of 1,439 matches, The data I am interested is the integer 1.439 shown at the bottom.I am just wondering how can I get that integer out of the HTML. I am now considering using a regular expression,and then use the java.util.Pattern to help get the data out,but still not very clear about the process. I would be grateful if you guys could give me some hint or idea on this data scraping. Thanks a lot.

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• Abstracting boxed array structures in J

  - by estanford

  I've been working on a J function for a while, that's supposed to scan a list and put consecutive copies of an element into separate, concatenated boxes. My efforts have taken me as far as the function (<;. 2) ((2&(~:/\)),1:) which tests successive list entries for inequality, returns a list of boolean values, and cuts the list into boxes that end each time the number 1 appears. Here's an example application: (<;. 2) ((2&(~:/\)),1:) 1 2 3 3 3 4 1 1 1 +-+-+-----+-+-----+ |1|1|0 0 1|1|0 0 1| +-+-+-----+-+-----+ The task would be finished if I could then replace all those booleans with their corresponding values in the input argument. I've been looking for some kind of mystery function that would let me do something like final =: mysteryfunction @ (<;. 2) ((2&(~:/\)),1:) final 1 2 3 3 3 4 1 1 1 +-+-+-----+-+-----+ |1|2|3 3 3|4|1 1 1| +-+-+-----+-+-----+ In an ideal situation, there would be some way to abstractly represent the nesting pattern generated by (<;. 2) ((2&(~:/\)),1:) to the original input list. (i.e. "This boxed array over here has the first element boxed at depth one, the second element boxed at depth one, the third, fourth, and fifth elements boxed together at depth one,..., so take that unboxed list over there and box it up the same way.") I tried fooling around with ;. , S: , L:, L. and &. to produce that behavior, but I haven't had much luck. Is there some kind of operator or principle I'm missing that could make this happen? It wouldn't surprise me if I were overthinking the whole issue, but I'm running out of ideas.

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• Search and replace hundreds of strings in tens of thousands of files?

  - by C Johnson

  I am looking into changing the file name of hundreds of files in a (C/C++) project that I work on. The problem is our software has tens of thousands of files that including (i.e. #include) these hundreds of files that will get changed. This looks like a maintenance nightmare. If I do this I will be stuck in Ultra-Edit for weeks, rolling hundreds of regex's by hand like so: ^\#include.*["<\\/]stupid_name.*$ with #include <dir/new_name.h> Such drudgery would be worse than peeling hundreds of potatoes in a sunken submarine in the antarctic with a spoon. I think it would rather be ideal to put the inputs and outputs into a table like so: stupid_name.h <-> <dir/new_name.h> stupid_nameb.h <-> <dir/new_nameb.h> stupid_namec.h <-> <dir/new_namec.h> and feed this into a regular expression engine / tool / app / etc... My Ultimate Question: Is there a tool that will do that? Bonus Question: Is it multi-threaded? I looked at quite a few search and replace topics here on this website, and found lots of standard queries that asked a variant of the following question: standard question: Replace one term in N files. as opposed to: my question: Replace N terms in N files. Thanks in advance for any replies.

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