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• Most efficient way to check for DBNull and then assign to a variable?

  - by ilitirit

  This question comes up occasionally but I haven't seen a satisfactory answer. A typical pattern is (row is a DataRow): if (row["value"] != DBNull.Value) { someObject.Member = row["value"]; } My first question is which is more efficient (I've flipped the condition): row["value"] == DBNull.Value; // Or row["value"] is DBNull; // Or row["value"].GetType() == typeof(DBNull) // Or... any suggestions? This indicates that .GetType() should be faster, but maybe the compiler knows a few tricks I don't? Second question, is it worth caching the value of row["value"] or does the compiler optimize the indexer away anyway? eg. object valueHolder; if (DBNull.Value == (valueHolder = row["value"])) {} Disclaimers: row["value"] exists. I don't know the column index of the column (hence the column name lookup) I'm asking specifically about checking for DBNull and then assignment (not about premature optimization etc). Edit: I benchmarked a few scenarios (time in seconds, 10000000 trials): row["value"] == DBNull.Value: 00:00:01.5478995 row["value"] is DBNull: 00:00:01.6306578 row["value"].GetType() == typeof(DBNull): 00:00:02.0138757 Object.ReferenceEquals has the same performance as "==" The most interesting result? If you mismatch the name of the column by case (eg. "Value" instead of "value", it takes roughly ten times longer (for a string): row["Value"] == DBNull.Value: 00:00:12.2792374 The moral of the story seems to be that if you can't look up a column by it's index, then ensure that the column name you feed to the indexer matches the DataColumn's name exactly. Caching the value also appears to be nearly twice as fast: No Caching: 00:00:03.0996622 With Caching: 00:00:01.5659920 So the most efficient method seems to be: object temp; string variable; if (DBNull.Value != (temp = row["value"]) { variable = temp.ToString(); } This was a good learning experience.

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• Using Mod-Rewrite in XAMPP

  - by rrrfusco

  I've followed some tutorials on how to use Mod_Rewrite, but it's not working out. I have a php index page that takes a page parameter like so: call: index?page=name1, name2, name3 etc. <?php if (isset($_GET['page'])) { switch($_GET['page']) { case 'front': include "front.php"; break; default: break; } } ? I'd like to run mod-rewrite so that the urls display as site.com/name1. Is this possible with the code i'm using above? Below is what I've been trying in the apache config files to no avail. apache/conf/http.conf line 122: LoadModule rewrite_module modules/mod_rewrite.so line 188: DocumentRoot "G:/xampp/htdocs" line 198: #default <Directory /> Options FollowSymLinks AllowOverride None Order deny,allow Deny from all </Directory> line 215: <Directory "G:/xampp/htdocs"> line 228: Options Indexes FollowSymLinks Includes ExecCGI line 235: AllowOverride All # cgi line 355: <Directory "G:/xampp/cgi-bin"> AllowOverride None Options None Order allow,deny Allow from all </Directory> G:\xampp\apache\conf\extra\http.v-hosts.conf <VirtualHost *:80> DocumentRoot G:/xampp/htdocs/ ServerName localhost ServerAdmin admin@localhost <Directory "G:/xampp/htdocs/localhost/"> Options Indexes FollowSymLinks AllowOverride FileInfo Order allow,deny Allow from all </Directory> </VirtualHost> <VirtualHost *:80> DocumentRoot G:/xampp/htdocs/site2/ ServerName site2.localhost ServerAdmin [email protected] <Directory "G:/xampp/htdocs/site2.localhost/"> Options Indexes FollowSymLinks AllowOverride FileInfo Order allow,deny Allow from all </Directory> </VirtualHost> .htaccess file IndexIgnore * RewriteEngine on RewriteRule ^([^/\.]+)/?$ /index.php?page=$1 [L]

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• Printing a DataTable to textbox/textfile in .NET

  - by neodymium

  Is there a predefined or "easy" method of writing a datatable to a text file or TextBox Control (With monospace font) such as DataTable.Print(): Column1| Column2| --------|--------| v1| v2| v3| v4| v5| v6| Edit Here's an initial version (vb.net) - in case anyone is interested or wants to build their own: Public Function BuildTable(ByVal dt As DataTable) As String Dim result As New StringBuilder Dim widths As New List(Of Integer) Const ColumnSeparator As Char = "|"c Const HeadingUnderline As Char = "-"c ' determine width of each column based on widest of either column heading or values in that column For Each col As DataColumn In dt.Columns Dim colWidth As Integer = Integer.MinValue For Each row As DataRow In dt.Rows Dim len As Integer = row(col.ColumnName).ToString.Length If len > colWidth Then colWidth = len End If Next widths.Add(CInt(IIf(colWidth < col.ColumnName.Length, col.ColumnName.Length + 1, colWidth + 1))) Next ' write column headers For Each col As DataColumn In dt.Columns result.Append(col.ColumnName.PadLeft(widths(col.Ordinal))) result.Append(ColumnSeparator) Next result.AppendLine() ' write heading underline For Each col As DataColumn In dt.Columns Dim horizontal As String = New String(HeadingUnderline, widths(col.Ordinal)) result.Append(horizontal.PadLeft(widths(col.Ordinal))) result.Append(ColumnSeparator) Next result.AppendLine() ' write each row For Each row As DataRow In dt.Rows For Each col As DataColumn In dt.Columns result.Append(row(col.ColumnName).ToString.PadLeft(widths(col.Ordinal))) result.Append(ColumnSeparator) Next result.AppendLine() Next Return result.ToString() End Function

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• Microsoft Solver Foundation constraint

  - by emaster70

  Hello, I'm trying to use Microsoft Solver Foundation 2 to solve a fairly complicated situation, however I'm stuck with an UnsupportedModelException even when I dumb down the model as much as possible. Does anyone have an idea of what I'm doing wrong? Following is the least example required to reproduce the problematic behavior. var ctx = SolverContext.GetContext(); var model = ctx.CreateModel(); var someConstant = 1337.0; var decisionA = new Decision(Domain.Real, "decisionA"); var decisionB = new Decision(Domain.Real, "decisionB"); var decisionC = new Decision(Domain.Real, "decisionC"); model.AddConstraint("ca", decisionA <= someConstant); model.AddConstraint("cb", decisionB <= someConstant); model.AddConstraint("cc", decisionC <= someConstant); model.AddConstraint("mainConstraint", Model.Equal(Model.Sum(decisionA, decisionB, decisionC), someConstant)) model.AddGoal("myComplicatedGoal", GoalKind.Minimize, decisionC); var solution = ctx.Solve(); solution.GetReport().WriteTo(Console.Out); Console.ReadKey(); Please consider that my actual model should include, once complete, a few constraints in the form of a*a+b*a <= someValue, so if what I'm willing to do ultimately isn't supported, please let me know in advance. If that's the case I'd also appreciate a suggestion of some other solver with a .NET friendly interface that I could use (only well-known commercial packages, please). Thanks in advance

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• using jquery growl with php/mysql

  - by jeansymolanza

  on my database i am planning to create a table storing messages to alert users of anything they need to do. i am looking at using a jQuery growl like notification method but im confused at how i would begin building it. the data would be added into the database using the standard MYSQL insert method from a form but how would i select messages from the database to display using the jQuery growl. would this require the use of ajax? this is the javascript code i have so far, i was wondering how i would implement the php code alongside it so that i can pull out data from my tables to display as notifications: <script type="text/javascript"> // In case you don't have firebug... if (!window.console || !console.firebug) { var names = ["log", "debug", "info", "warn", "error", "assert", "dir", "dirxml", "group", "groupEnd", "time", "timeEnd", "count", "trace", "profile", "profileEnd"]; window.console = {}; for (var i = 0; i < names.length; ++i) window.console[names[i]] = function() {}; } (function($){ $(document).ready(function(){ // This specifies how many messages can be pooled out at any given time. // If there are more notifications raised then the pool, the others are // placed into queue and rendered after the other have disapeared. $.jGrowl.defaults.pool = 5; var i = 1; var y = 1; setInterval( function() { if ( i < 3 ) { $.jGrowl("Message " + i, { sticky: true, log: function() { console.log("Creating message " + i + "..."); }, beforeOpen: function() { console.log("Rendering message " + y + "..."); y++; } }); } i++; } , 1000 ); }); })(jQuery); </script> <p> thanking you in advance and God bless

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• DOJO : How do you reinitiate form elements after ajax call ?

  - by Dural

  I'm trying to do a couple of things using Zend Framework & Dojo Toolkit, and any help would be appreciated. Here's the problem: I have a form that is rendered with the Zend Framework form class, which has an ajax radio button selection. Clicking one of these radio buttons will send an ajax request to another controller, which has no layout, just a rendered form. The ajax request will then populate a div with the new form options. Problem is, when I replace the innerHTML of the div with the ajax response, all the form inputs and elements are not inheriting the same Dojo styling and form validation. I was wondering if there is a way to reinitate form elements after an ajax call? I have tried to use the code attached which I found and modified slightly for this example, however it did not work. If I use the line dojo.parser.parse( div ); nothing changes (rg_adress in the example is the ID of a form element that is placed on the DOM). Here is the console.log of rg_address: <input type="text" dojotype="dijit.form.ValidationTextBox" required="1" invalidmessage="The first name of the recipient" value="" name="rg_address" id="rg_address" class="textbox"/> onClick=' dojo.xhrGet( { url: "/transfer/newrecipient/", handleAs: "text", timeout: 10000, // Time in milliseconds // The LOAD function will be called on a successful response. load: function(response, ioArgs) { $("#newRecipient").html(response); $("#newPayMethod").html(""); $("#newPayDetail").html(""); var div = dojo.byId("rg_address"); console.log( div ); dojo.parser.parse( div ); return response; }, // The ERROR function will be called in an error case. error: function(response, ioArgs) { $("#newRecipient").html("Error loading registration form"); $("#newPayMethod").html(""); $("#newPayDetail").html(""); return response; } });' Thanks, Dural

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• How to get max row from table

  - by Odette

  HI I have the following code and a massive problem: WITH CALC1 AS ( SELECT OTQUOT, OTIT01 AS ITEMS, ROUND(OQCQ01 * OVRC01,2) AS COST FROM @[email protected] WHERE OTIT01 <> '' UNION ALL SELECT OTQUOT, OTIT02 AS ITEMS, ROUND(OQCQ02 * OVRC02,2) AS COST FROM @[email protected] WHERE OTIT02 <> '' UNION ALL SELECT OTQUOT, OTIT03 AS ITEMS, ROUND(OQCQ03 * OVRC03,2) AS COST FROM @[email protected] WHERE OTIT03 <> '' UNION ALL SELECT OTQUOT, OTIT04 AS ITEMS, ROUND(OQCQ04 * OVRC04,2) AS COST FROM @[email protected] WHERE OTIT04 <> '' UNION ALL SELECT OTQUOT, OTIT05 AS ITEMS, ROUND(OQCQ05 * OVRC05,2) AS COST FROM @[email protected] WHERE OTIT05 <> '' ORDER BY OTQUOT ASC ) SELECT OTQUOT, ITEMS, MAX(COST) FROM CALC1 WHERE OTQUOT = '04886471' GROUP BY OTQUOT, ITEMS result: 04886471 FEPO5050WCGA24 13.21 04886471 GFRK1650SGL 36.21 04886471 FRA7500GA 12.6 04886471 CGIFESHAZ 11.02 04886471 CGIFESHPDPR 11.79 04886471 GFRK1350DBL 68.23 04886471 RET1.63825GP 32.55 04886471 FRSA 0.12 04886471 GFRK1350SGL 55.94 04886471 GFRK1650DBL 71.89 04886471 FEPO6565WCGA24 16.6 04886471 PCAP5050GA 0.28 04886471 FEPO6565NCPAG24 0.000000 How can I get the result of the row with the Itemcode that has the highest value? In this case I need the result: 04886471 GFRK1650DBL 71.89 but i dont know how to change my code to get that - can anybody please help me?

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• Technically why is processes in Erlang more efficient than OS threads?

  - by Jonas

  Spawning processes seam to be much more efficient in Erlang than starting new threads using the OS (i.e. by using Java or C). Erlang spawns thousands and millions of processes in a short period of time. I know that they are different since Erlang do per process GC and processes in Erlang are implemented the same way on all platforms which isn't the case with OS threads. But I don't fully understand technically why Erlang processes are so much more efficient and has much smaller memory footprint per process. Both the OS and Erlang VM has to do scheduling, context switches and keep track of the values in the registers and so on... Simply why isn't OS threads implemented in the same way as processes in Erlang? Does it have to support something more? and why does it need a bigger memory footprint? Technically why is processes in Erlang more efficient than OS threads? And why can't threads in the OS be implemented and managed in the same efficient way?

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• Wanted to know in detail about how shared libraries work vis-a-vis static library.

  - by goldenmean

  Hello, I am working on creating and linking shared library (.so). While working with them, many questions popped up which i could not find satisying answers when i searched for them, hence putting them here. The questions about shared libraries i have are: 1.) How is shared library different than static library? What are the Key differences in way they are created, they execute? 2.) In case of a shared library at what point are the addresses where a particular function in shared library will be loaded and run from, given? Who gives those functions is load/run addresses? 3.) Will an application linked against shared library be slower in execution as compared to that which is linked with a static library? 4.) Will application executable size differ in these two cases? 5.) Can one do source level debugging of by stepping into functions defined inside a shared library? Is any thing extra needed to make these functions visible to the application? 6.) What are pros and cons in using either kind of library? Thanks. -AD

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• How to add a Web Part Zone to a SharePoint wiki page?

  - by Hitesh

  Hi, I have a team site. I understand that the default home page of a team site is a wiki page. I want to add a web part zone to this page. How can I do that? By default it already has Web Part Zone -. You can use SharePoint designer to add a web part to this zone and it works fine. But you are not able to add a web part to this zone using SharePoint web UI? Ususally when you have a web part zone in a page, using SharePoint web UI, it allows to you add/remove a web part. But it is not the case with the web part zone on the default home page of a team site. Also is there any way I can add a web part zone to this page? I do know that you can easily add web parts into wiki page content. But I want to add a new web part zone where users can add/remove web parts. Thanks, Hitesh

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• Load external pages using jquery

  - by user1688011

  I'm trying to use jquery to load external pages into the current without reloading. Apparently everything works fine except of one little issue, I hope I'll be clear as much as possible. When I call the page 'info.php' it is loaded into the #content div. That's what the script supposed to do, the problem is that in the main page, which contains the script and the #content div, I already have some code that I want it to be executed when someone visit the page and not to be called from external page. That is actually the case but when I click on one of the links in the menu, I can't go back to the initial content.. <script> $(function() { $('#nav a').click(function() { var page = $(this).attr('href'); $('#content').load(page + '.php'); return false; }); }); </script> <ul id="nav"> <li><a href="#">Page1</a></li> <li><a href="about">About</a></li> <li><a href="contact">Contact</a></li> <li><a href="info">Info</a></li> </ul> <div id="content"> Here I have some code that I wanted to be attributed to the "Page1" </div> Do you have any suggestions how to fix this issue? Thanks

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• WPF - binding ElementName problem...

  - by zvi

  Hello First Sorry for my English. I wanted to ask why ElementName does not work the first case, and work in the second. I give the two sections of code . the firts not work <Button Name="button1" Width="100" > <Button.LayoutTransform> <ScaleTransform x:Name="ttt" ScaleX="3" ScaleY="6"/> </Button.LayoutTransform> <Button.Triggers> <EventTrigger RoutedEvent="Path.Loaded"> <EventTrigger.Actions> <BeginStoryboard> <Storyboard RepeatBehavior="Forever"> <DoubleAnimation Storyboard.Target="{Binding ElementName=ttt}" Storyboard.TargetProperty="ScaleX" From="10" To="5" Duration="0:0:1" /> </Storyboard> </BeginStoryboard> </EventTrigger.Actions> </EventTrigger> </Button.Triggers> Button </Button> But it does work <Button Name="button1" Width="100" > <Button.LayoutTransform> <ScaleTransform x:Name="ttt" ScaleX="3" ScaleY="6"/> </Button.LayoutTransform> <Button.Triggers> <EventTrigger RoutedEvent="Path.Loaded"> <EventTrigger.Actions> <BeginStoryboard> <Storyboard RepeatBehavior="Forever"> <DoubleAnimation Storyboard.Target="{Binding ElementName=button1}" Storyboard.TargetProperty="Width" From="100" To="50" Duration="0:0:1" /> </Storyboard> </BeginStoryboard> </EventTrigger.Actions> </EventTrigger> </Button.Triggers> Button </Button> I know I can use Storyboard.TargetName .

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• Why This Maintainability Index Increase?

  - by Timothy

  I would be appreciative if someone could explain to me the difference between the following two pieces of code in terms of Visual Studio's Code Metrics rules. Why does the Maintainability Index increase slightly if I don't encapsulate everything within using ( )? Sample 1 (MI score of 71) public static String Sha1(String plainText) { using (SHA1Managed sha1 = new SHA1Managed()) { Byte[] text = Encoding.Unicode.GetBytes(plainText); Byte[] hashBytes = sha1.ComputeHash(text); return Convert.ToBase64String(hashBytes); } } Sample 2 (MI score of 73) public static String Sha1(String plainText) { Byte[] text, hashBytes; using (SHA1Managed sha1 = new SHA1Managed()) { text = Encoding.Unicode.GetBytes(plainText); hashBytes = sha1.ComputeHash(text); } return Convert.ToBase64String(hashBytes); } I understand metrics are meaningless outside of a broader context and understanding, and programmers should exercise discretion. While I could boost the score up to 76 with return Convert.ToBase64String(sha1.ComputeHash(Encoding.Unicode.GetBytes(plainText))), I shouldn't. I would clearly be just playing with numbers and it isn't truly any more readable or maintainable at that point. I am curious though as to what the logic might be behind the increase in this case. It's obviously not line-count.

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• WPF: Once I set a property in code, it ignores XAML binding forever more... how do I prevent that?

  - by Timothy Khouri

  I have a button that has a datatrigger that is used to disable the button if a certain property is not set to true: <Button Name="ExtendButton" Click="ExtendButton_Click" Margin="0,0,0,8"> <Button.Style> <Style> <Style.Triggers> <DataTrigger Binding="{Binding IsConnected}" Value="False"> <Setter Property="Button.IsEnabled" Value="False" /> </DataTrigger> </Style.Triggers> </Style> </Button.Style> That's some very simple binding, and it works perfectly. I can set "IsConnected" true and false and true and false and true and false, and I love to see my button just auto-magically become disabled, then enabled, etc. etc. However, in my Button_Click event... I want to: Disable the button (by using ExtendButton.IsEnabled = false;) Run some asynchronous code (that hits a server... takes about 1 second). Re-enable the button (by using ExtendButton.IsEnabled = true;) The problem is, the very instant that I manually set IsEnabled to either true or false... my XAML binding will never fire again. This makes me very sad :( I wish that IsEnabled was tri-state... and that true meant true, false meant false and null meant inherit. But that is not the case, so what do I do?

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• JScrollPanel without scrollbars

  - by Erik Itland

  I'm trying to use a JScrollPanel to display a JPanel that might be too big for the containing Jpanel. I don't want to show the scrollbars (yes, this is questionable UI design, but it is my best guess of what the customer wants. We use the same idea other places in the application, and I feel this case have given me enough time to ponder if I can do it in a better way, but if you have a better idea I might accept it an answer.) First attempt: set verticalScrollBarPolicy to NEVER. Result: Scrolling using mouse wheel doesn't work. Second attempt: set the scrollbars to null. Result: Scrolling using mouse wheel doesn't work. Third attempt: set scrollbars visible property to false. Result: It is immidiately set visible by Swing. Fourth attempt: inject a scrollbar where setVisible is overridden to do nothing when called with true. Result: Can't remember exactly, but I think it just didn't work. Fifth attempt: inject a scrollbar where setBounds are overridden. Result: Just didn't look nice. (I might have missed something here, though.) Sixth attempt: ask stackoverflow. Result: Pending. Scrolling works once scrollbars are back.

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• 'SImple' 2 class Java calculator doesn't accept inputs or do calculations

  - by Tony O'Keeffe

  Hi, I'm trying to get a two class java calculator working (new to java) to work but so far i'm having no success. the two classes are outlined below, calcFrame is for the interface and calEngine should do the actual calculations but i can't get them to talk to one another. i'd really appreciate any assistance on same. Thanks. CalcFrame Code - import java.awt.; import javax.swing.; import javax.swing.border.; import java.awt.event.; /** *A Class that operates as the framework for a calculator. *No calculations are performed in this section */ public class CalcFrame implements ActionListener { private CalcEngine calc; private JFrame frame; private JTextField display; private JLabel status; /** * Constructor for objects of class GridLayoutExample */ public CalcFrame() { makeFrame(); //calc = engine; } /** * This allows you to quit the calculator. */ // Alows the class to quit. private void quit() { System.exit(0); } // Calls the dialog frame with the information about the project. private void showAbout() { JOptionPane.showMessageDialog(frame, "Group Project", "About Calculator Group Project", JOptionPane.INFORMATION_MESSAGE); } private void makeFrame() { frame = new JFrame("Group Project Calculator"); makeMenuBar(frame); JPanel contentPane = (JPanel)frame.getContentPane(); contentPane.setLayout(new BorderLayout(8, 8)); contentPane.setBorder(new EmptyBorder( 10, 10, 10, 10)); /** * Insert a text field */ display = new JTextField(); contentPane.add(display, BorderLayout.NORTH); //Container contentPane = frame.getContentPane(); contentPane.setLayout(new GridLayout(4, 4)); JPanel buttonPanel = new JPanel(new GridLayout(4, 4)); contentPane.add(new JButton("1")); contentPane.add(new JButton("2")); contentPane.add(new JButton("3")); contentPane.add(new JButton("4")); contentPane.add(new JButton("5")); contentPane.add(new JButton("6")); contentPane.add(new JButton("7")); contentPane.add(new JButton("8")); contentPane.add(new JButton("9")); contentPane.add(new JButton("0")); contentPane.add(new JButton("+")); contentPane.add(new JButton("-")); contentPane.add(new JButton("/")); contentPane.add(new JButton("*")); contentPane.add(new JButton("=")); contentPane.add(new JButton("C")); contentPane.add(buttonPanel, BorderLayout.CENTER); //status = new JLabel(calc.getAuthor()); //contentPane.add(status, BorderLayout.SOUTH); frame.pack(); frame.setVisible(true); } /** * Create the main frame's menu bar. * The frame that the menu bar should be added to. */ private void makeMenuBar(JFrame frame) { final int SHORTCUT_MASK = Toolkit.getDefaultToolkit().getMenuShortcutKeyMask(); JMenuBar menubar = new JMenuBar(); frame.setJMenuBar(menubar); JMenu menu; JMenuItem item; // create the File menu menu = new JMenu("File"); menubar.add(menu); // create the Quit menu with a shortcut "Q" key. item = new JMenuItem("Quit"); item.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_Q, SHORTCUT_MASK)); item.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { quit(); } }); menu.add(item); // Adds an about menu. menu = new JMenu("About"); menubar.add(menu); // Displays item = new JMenuItem("Calculator Project"); item.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { showAbout(); } }); menu.add(item); } /** * An interface action has been performed. * Find out what it was and handle it. * @param event The event that has occured. */ public void actionPerformed(ActionEvent event) { String command = event.getActionCommand(); if(command.equals("0") || command.equals("1") || command.equals("2") || command.equals("3") || command.equals("4") || command.equals("5") || command.equals("6") || command.equals("7") || command.equals("8") || command.equals("9")) { int number = Integer.parseInt(command); calc.numberPressed(number); } else if(command.equals("+")) { calc.plus(); } else if(command.equals("-")) { calc.minus(); } else if(command.equals("=")) { calc.equals(); } else if(command.equals("C")) { calc.clear(); } else if(command.equals("?")) { } // else unknown command. redisplay(); } /** * Update the interface display to show the current value of the * calculator. */ private void redisplay() { display.setText("" + calc.getDisplayValue()); } /** * Toggle the info display in the calculator's status area between the * author and version information. */ } CalcEngine - public class CalcEngine { // The calculator's state is maintained in three fields: // buildingDisplayValue, haveLeftOperand, and lastOperator. // The current value (to be) shown in the display. private int displayValue; // The value of an existing left operand. private int leftOperand; /** * Create a CalcEngine. */ public CalcEngine() { clear(); } public int getDisplayValue() { return displayValue; } /** * A number button was pressed. * Either start a new operand, or incorporate this number as * the least significant digit of an existing one. * @param number The number pressed on the calculator. */ public void numberPressed(int number) { if(buildingDisplayValue) { // Incorporate this digit. displayValue = displayValue*10 + number; } else { // Start building a new number. displayValue = number; buildingDisplayValue = true; } } /** * The 'plus' button was pressed. */ public void plus() { applyOperator('+'); } /** * The 'minus' button was pressed. */ public void minus() { applyOperator('-'); } /** * The '=' button was pressed. */ public void equals() { // This should completes the building of a second operand, // so ensure that we really have a left operand, an operator // and a right operand. if(haveLeftOperand && lastOperator != '?' && buildingDisplayValue) { calculateResult(); lastOperator = '?'; buildingDisplayValue = false; } else { keySequenceError(); } } /** * The 'C' (clear) button was pressed. * Reset everything to a starting state. */ public void clear() { lastOperator = '?'; haveLeftOperand = false; buildingDisplayValue = false; displayValue = 0; } /** * @return The title of this calculation engine. */ public String getTitle() { return "Java Calculator"; } /** * @return The author of this engine. */ public String getAuthor() { return "David J. Barnes and Michael Kolling"; } /** * @return The version number of this engine. */ public String getVersion() { return "Version 1.0"; } /** * Combine leftOperand, lastOperator, and the * current display value. * The result becomes both the leftOperand and * the new display value. */ private void calculateResult() { switch(lastOperator) { case '+': displayValue = leftOperand + displayValue; haveLeftOperand = true; leftOperand = displayValue; break; case '-': displayValue = leftOperand - displayValue; haveLeftOperand = true; leftOperand = displayValue; break; default: keySequenceError(); break; } } /** * Apply an operator. * @param operator The operator to apply. */ private void applyOperator(char operator) { // If we are not in the process of building a new operand // then it is an error, unless we have just calculated a // result using '='. if(!buildingDisplayValue && !(haveLeftOperand && lastOperator == '?')) { keySequenceError(); return; } if(lastOperator != '?') { // First apply the previous operator. calculateResult(); } else { // The displayValue now becomes the left operand of this // new operator. haveLeftOperand = true; leftOperand = displayValue; } lastOperator = operator; buildingDisplayValue = false; } /** * Report an error in the sequence of keys that was pressed. */ private void keySequenceError() { System.out.println("A key sequence error has occurred."); // Reset everything. clear(); } }

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• How does the last integer promotion rule ever get applied in C?

  - by SiegeX

  6.3.1.8p1: Otherwise, the integer promotions are performed on both operands. Then the following rules are applied to the promoted operands: If both operands have the same type, then no further conversion is needed. Otherwise, if both operands have signed integer types or both have unsigned integer types, the operand with the type of lesser integer conversion rank is converted to the type of the operand with greater rank. Otherwise, if the operand that has unsigned integer type has rank greater or equal to the rank of the type of the other operand, then the operand with signed integer type is converted to the type of the operand with unsigned integer type. Otherwise, if the type of the operand with signed integer type can represent all of the values of the type of the operand with unsigned integer type, then the operand with unsigned integer type is converted to the type of the operand with signed integer type. Otherwise, both operands are converted to the unsigned integer type corresponding to the type of the operand with signed integer type. For the bolded rule to be applied it would seem to imply you need to have have an unsigned interger type who's rank is less than the signed integer type and the signed integer type cannot hold all the values of the unsigned integer type. Is there a real world example of such a case or is this statement serving as a catch-all to cover all possible permutations?

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• jQuery carousel in a div with display:none

  - by Fred Kafka

  I have to use on my site a jQuery responsive carousel with 4 displayed items that slide one at a time, etc etc. The point is: this carousel is placed in a div with display:none and it appears clicking on a button with a slideToggle script (jQuery). Well, when the div appears the carousel is not displayed. Nothing! Notice that if I remove the display:none the carousel shows perfectly. I've tried a bunch of carousel plugin (bxslider, caroufredsel, elastislide, flexslider) and this issue happens for all of them. And then... I'm going crazy!! Excuse meSorry friends, here is the code: HTML (here is the case of FlexSlider but the code is similar for the other plugins) <div id="hiddenDiv"> <div id="hiddenDivInner"> <div class="flexslider"> <ul class="slides"> <li>...</li> <li>...</li> <li>...</li> </ul> </div> </div> </div> CSS #hiddenDiv{ display:none; padding-bottom:10px; background: url("../img/xxx.gif") repeat left bottom #FFFFFF; } SCRIPT (copy-paste from the site. This script is between $(document).ready together with other scripts. Alredy tried to remove the load function) $(window).load(function() { $('.flexslider').flexslider({ animation: "slide", animationLoop: false, itemWidth: 300, itemMargin: 5, minItems: 1, maxItems: 4 }); }); $("#trigger").click(function () { $("#hiddenDiv").slideToggle(400, "easeInOutExpo"); }); I remind you that with this code and no display:none every carousels work, also if I slide up and then down the div using the slideToggle button (#trigger).

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• Why is curl in Ruby slower than command-line curl?

  - by Stiivi

  I am trying to download more than 1m pages (URLs ending by a sequence ID). I have implemented kind of multi-purpose download manager with configurable number of download threads and one processing thread. The downloader downloads files in batches: curl = Curl::Easy.new batch_urls.each { |url_info| curl.url = url_info[:url] curl.perform file = File.new(url_info[:file], "wb") file << curl.body_str file.close # ... some other stuff } I have tried to download 8000 pages sample. When using the code above, I get 1000 in 2 minutes. When I write all URLs into a file and do in shell: cat list | xargs curl I gen all 8000 pages in two minutes. Thing is, I need it to have it in ruby code, because there is other monitoring and processing code. I have tried: Curl::Multi - it is somehow faster, but misses 50-90% of files (does not download them and gives no reason/code) multiple threads with Curl::Easy - around the same speed as single threaded Why is reused Curl::Easy slower than subsequent command line curl calls and how can I make it faster? Or what I am doing wrong? I would prefer to fix my download manager code than to make downloading for this case in a different way. Before this, I was calling command-line wget which I provided with a file with list of URLs. Howerver, not all errors were handled, also it was not possible to specify output file for each URL separately when using URL list. Now it seems to me that the best way would be to use multiple threads with system call to 'curl' command. But why when I can use directly Curl in Ruby? Code for the download manager is here, if it might help: Download Manager (I have played with timeouts, from not-setting it to various values, it did not seem help) Any hints appreciated.

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• Display a input type=file over another input type=file

  - by Kevin Sedgley

  WARNING: Lengthy description coming up! I have written an uploader based upon APC progress uploader for PHP. This works fine and dandy, but the script as a whole (apc etc) is intended to be used only for those with Javascript. To achieve this, I have searched for any input type=file, and replaced these with an absolutely positioned form that appears over the original area where the old file input area was. The reasons for this are so the new uploader can submit to a hidden in page IFrame has to be in a seperate <form> in order to submit to the APC reciever to display the progress upload bar. allows it to be used within any form with an input type=file throughout the site I have used JQuery to do this, with the following code: Original HTML form code: <div><input type="file" name="media" id="media" /></div> Find position of div block code: // get the parent div, and properties thereof parentDiv = $(this).closest('div'); w = $(parentDiv).width(); h = $(parentDiv).height(); loc = $(parentDiv).offset(); Locate new block over old block: $('#_sender').appendTo('body').css({left:loc.left,top:loc.top,position:'absolute',zIndex:400,height:h,width:w}).show(); This works fine, and shows over the old block OK. The problem: When other elements in the DOM before or above it change (in this case a "tree view" selector is pushing the old block down) the new upload form gets moved over other elements. Is there a JQuery (or JS) method for changing this upon DOM change? Some kind of .onchange for the page?! Or an .onmove for the original block? Thanks in advance you lovely people Before DOM change: . After: .

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• Just messed up a server misusing chown, how to execute it correctly?

  - by Jack Webb-Heller

  Hi! I'm moving from an old shared host to a dedicated server at MediaTemple. The server is running Plesk CP, but, as far as I can tell, there's no way via the Interface to do what I want to do. On the old shared host, running cPanel, I creative a .zip archive of all the website's files. I downloaded this to my computer, then uploaded it with FTP to the new host account I'd set up. Finally, I logged in via SSH, navigated to the directory the zip was stored in (something like var/www/vhosts/mysite.com/httpdocs/ and ran the unzip command on the file sitearchive.zip. This extracted everything just the fine. The site appeared to work just fine. The problem: When I tried to edit a file through FTP, I got Error - 160: Permission Denied. When I Get Info for the file I'm trying to edit, it says the owner and group is swimwir1. I attemped to use chown at this point to change owner - and yes, as you may be able to tell, I'm a little inexperienced in SSH ;) luckily the server was new, since the command I ran - chown -R newuser / appeared to mess a load of stuff up. The reason I used / on the end rather than /var/www/vhosts/mysite.com/httpdocs/ was because I'd already cded into their, so I presumed the / was relative to where I was working. This may be the case, I have no idea, either way - Plesk was no longer accessible, although Apache and things continued to work. I realised my mistake, and deciding it wasn't worth the hassle of 1) being an amateur and 2) trying to fix it, I just reprovisioned the server to start afresh. So - what do I do to change the owner of these files correctly? Thanks for helping out a confused beginner! Jack

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• HTTP crawler in Erlang

  - by ctp

  I'm coding on a simple HTTP crawler but I have an issue running the code at the bottom. I'm requesting 50 URLs and get the content of 20+ back. I've generated few files with 150kB size each to test the crawler. So I think the 20+ responses are limited by the bandwidth? BUT: how to tell the Erlang snippet not to quit until the last file is not fetched? The test data server is online, so plz try the code out and any hints are welcome :) -module(crawler). -define(BASE_URL, "http://46.4.117.69/"). -export([start/0, send_reqs/0, do_send_req/1]). start() -> ibrowse:start(), proc_lib:spawn(?MODULE, send_reqs, []). to_url(Id) -> ?BASE_URL ++ integer_to_list(Id). fetch_ids() -> lists:seq(1, 50). send_reqs() -> spawn_workers(fetch_ids()). spawn_workers(Ids) -> lists:foreach(fun do_spawn/1, Ids). do_spawn(Id) -> proc_lib:spawn_link(?MODULE, do_send_req, [Id]). do_send_req(Id) -> io:format("Requesting ID ~p ... ~n", [Id]), Result = (catch ibrowse:send_req(to_url(Id), [], get, [], [], 10000)), case Result of {ok, Status, _H, B} -> io:format("OK -- ID: ~2..0w -- Status: ~p -- Content length: ~p~n", [Id, Status, length(B)]); Err -> io:format("ERROR -- ID: ~p -- Error: ~p~n", [Id, Err]) end. That's the output: Requesting ID 1 ... Requesting ID 2 ... Requesting ID 3 ... Requesting ID 4 ... Requesting ID 5 ... Requesting ID 6 ... Requesting ID 7 ... Requesting ID 8 ... Requesting ID 9 ... Requesting ID 10 ... Requesting ID 11 ... Requesting ID 12 ... Requesting ID 13 ... Requesting ID 14 ... Requesting ID 15 ... Requesting ID 16 ... Requesting ID 17 ... Requesting ID 18 ... Requesting ID 19 ... Requesting ID 20 ... Requesting ID 21 ... Requesting ID 22 ... Requesting ID 23 ... Requesting ID 24 ... Requesting ID 25 ... Requesting ID 26 ... Requesting ID 27 ... Requesting ID 28 ... Requesting ID 29 ... Requesting ID 30 ... Requesting ID 31 ... Requesting ID 32 ... Requesting ID 33 ... Requesting ID 34 ... Requesting ID 35 ... Requesting ID 36 ... Requesting ID 37 ... Requesting ID 38 ... Requesting ID 39 ... Requesting ID 40 ... Requesting ID 41 ... Requesting ID 42 ... Requesting ID 43 ... Requesting ID 44 ... Requesting ID 45 ... Requesting ID 46 ... Requesting ID 47 ... Requesting ID 48 ... Requesting ID 49 ... Requesting ID 50 ... OK -- ID: 49 -- Status: "200" -- Content length: 150000 OK -- ID: 47 -- Status: "200" -- Content length: 150000 OK -- ID: 50 -- Status: "200" -- Content length: 150000 OK -- ID: 17 -- Status: "200" -- Content length: 150000 OK -- ID: 48 -- Status: "200" -- Content length: 150000 OK -- ID: 45 -- Status: "200" -- Content length: 150000 OK -- ID: 46 -- Status: "200" -- Content length: 150000 OK -- ID: 10 -- Status: "200" -- Content length: 150000 OK -- ID: 09 -- Status: "200" -- Content length: 150000 OK -- ID: 19 -- Status: "200" -- Content length: 150000 OK -- ID: 13 -- Status: "200" -- Content length: 150000 OK -- ID: 21 -- Status: "200" -- Content length: 150000 OK -- ID: 16 -- Status: "200" -- Content length: 150000 OK -- ID: 27 -- Status: "200" -- Content length: 150000 OK -- ID: 03 -- Status: "200" -- Content length: 150000 OK -- ID: 23 -- Status: "200" -- Content length: 150000 OK -- ID: 29 -- Status: "200" -- Content length: 150000 OK -- ID: 14 -- Status: "200" -- Content length: 150000 OK -- ID: 18 -- Status: "200" -- Content length: 150000 OK -- ID: 01 -- Status: "200" -- Content length: 150000 OK -- ID: 30 -- Status: "200" -- Content length: 150000 OK -- ID: 40 -- Status: "200" -- Content length: 150000 OK -- ID: 05 -- Status: "200" -- Content length: 150000 Update: thanks stemm for the hint with the wait_workers. I've combined your and mine code but same behaviour :( -module(crawler). -define(BASE_URL, "http://46.4.117.69/"). -export([start/0, send_reqs/0, do_send_req/2]). start() -> ibrowse:start(), proc_lib:spawn(?MODULE, send_reqs, []). to_url(Id) -> ?BASE_URL ++ integer_to_list(Id). fetch_ids() -> lists:seq(1, 50). send_reqs() -> spawn_workers(fetch_ids()). spawn_workers(Ids) -> %% collect reference to each worker Refs = [ do_spawn(Id) || Id <- Ids ], %% wait for response from each worker wait_workers(Refs). wait_workers(Refs) -> lists:foreach(fun receive_by_ref/1, Refs). receive_by_ref(Ref) -> %% receive message only from worker with specific reference receive {Ref, done} -> done end. do_spawn(Id) -> Ref = make_ref(), proc_lib:spawn_link(?MODULE, do_send_req, [Id, {self(), Ref}]), Ref. do_send_req(Id, {Pid, Ref}) -> io:format("Requesting ID ~p ... ~n", [Id]), Result = (catch ibrowse:send_req(to_url(Id), [], get, [], [], 10000)), case Result of {ok, Status, _H, B} -> io:format("OK -- ID: ~2..0w -- Status: ~p -- Content length: ~p~n", [Id, Status, length(B)]), %% send message that work is done Pid ! {Ref, done}; Err -> io:format("ERROR -- ID: ~p -- Error: ~p~n", [Id, Err]), %% repeat request if there was error while fetching a page, do_send_req(Id, {Pid, Ref}) %% or - if you don't want to repeat request, put there: %% Pid ! {Ref, done} end. Running the crawler forks fine for a handful of files, but then the code even doesnt fetch the entire files (file size each 150000 bytes) - he crawler fetches some files partially, see the following web server log :( 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /10 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /1 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /3 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /8 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /39 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /7 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /6 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /2 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /5 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /50 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /9 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /44 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /38 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /47 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /49 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /43 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /37 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /46 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /48 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /36 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /42 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /41 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /45 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /17 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /35 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /16 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /15 HTTP/1.1" 200 17020 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /21 HTTP/1.1" 200 120360 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /40 HTTP/1.1" 200 117600 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /34 HTTP/1.1" 200 60660 "-" "-" Any hints are welcome. I have no clue what's going wrong there :(

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• Why use INCLUDE in a SQL index

  - by StarLite

  I recently encountered an index in a database I maintain that was of the form: CREATE INDEX [IX_Foo] ON [Foo] ( Id ASC ) INCLUDE ( SubId ) In this particular case, the performance problem that I was encountering (a slow SELECT filtering on both Id and SubId) could be fixed by simply moving the SubId column into the index proper rather than as an included column. This got me thinking however that I don't understand the reasoning behind included columns at all, when generally, they could simply be a part of the index itself. Even if I don't particularly care about the items being in the index itself is there any downside to having column in the index rather than simply being included. After some research, I am aware that there are a number of restrictions on what can go into an indexed column (maximum width of the index, and some column types that can't be indexed like 'image'). In these cases I can see that you would be forced to include the column in the index page data. The only thing I can think of is that if there are updates on SubId, the row will not need to be relocated if the column is included (though the value in the index would need to be changed). Is there something else that I'm missing? I'm considering going through the other indexes in the database and shifting included columns in the index proper where possible. Would this be a mistake? I'm primarily interested in MS SQL Server, but information on other DB engines is welcome also.

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• Design suggestion for expression tree evaluation with time-series data

  - by Lirik

  I have a (C#) genetic program that uses financial time-series data and it's currently working but I want to re-design the architecture to be more robust. My main goals are: sequentially present the time-series data to the expression trees. allow expression trees to access previous data rows when needed. to optimize performance of the data access while evaluating the expression trees. keep a common interface so various types of data can be used. Here are the possible approaches I've thought about: I can evaluate the expression tree by passing in a data row into the root node and let each child node use the same data row. I can evaluate the expression tree by passing in the data row index and letting each node get the data row from a shared DataSet (currently I'm passing the row index and going to multiple synchronized arrays to get the data). Hybrid: an immutable data set is accessible by all of the expression trees and each expression tree is evaluated by passing in a data row. The benefit of the first approach is that the data row is being passed into the expression tree and there is no further query done on the data set (which should increase performance in a multithreaded environment). The drawback is that the expression tree does not have access to the rest of the data (in case some of the functions need to do calculations using previous data rows). The benefit of the second approach is that the expression trees can access any data up to the latest data row, but unless I specify what that row is, I'll have to iterate through the rows and figure out which one is the last one. The benefit of the hybrid is that it should generally perform better and still provide access to the earlier data. It supports two basic "views" of data: the latest row and the previous rows. Do you guys know of any design patterns or do you have any tips that can help me build this type of system? Should I use a DataSet to hold and present the data, or are there more efficient ways to present rows of data while maintaining a simple interface? FYI: All of my code is written in C#.

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• Best way for launching html/jsp to communicate with GWT module

  - by h2g2java

  I asked this at the GWT forum but I'm impatient for the answer and I seem to get rather good responses here. A html or jsp file is used to launch the xxx.nocache.js, which then decides which browser "permutation" to use. <head> <meta http-equiv="content-type" content="text/html;charset=UTF-8"> <title>xxx</title> <script type="text/javascript" language="javascript" src="xxx.nocache.js"></script> </head> In my case, I am using a jsp. When the JSP is executed, it discovers some conditions. I wish to pass these conditions as values to the GWT module being launched. The "elegant" GWT way to pass these values would be to persist them as request/memcache attributes and then have the GWT module perform RPC to retrieve those values. For example, the JSP discovers that the current user is Whoopy. Shouldn't I simply have the JSP generate javascript to store user = "Whoopy" as a top or namedframe level javascript variable and use JSNI within the module to retrieve the value for user? I have not tried it yet, but I would like to know how anyone might have done it without having to use RPC.

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