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• Which languages and techniques can I use to improve my coding practices?

  - by Danjah

  I've been offered the opportunity upskill through study, while at work which is great. My background I am mostly self-taught, but have worked with many excellent people over the years - both self-taught and fully educated, and on many decent projects. I have mild experience in Actionscript, I'm getting better every day with my Javascript, and my CSS is angled at best practice, but needs a bit of modernising. I'm a traditional interface developer, I'm not stupid and I like a challenge. My goal I need to start seeing ways of applying better logic, optimising code, refactoring, different styles of development (agile, others?), and.. well I need to try and start thinking like.. a more solid programmer. Its hard to describe, I have good solutions and I'm efficient - but I KNOW that there's a bunch I am missing. I am already employed with a solid career, but I feel the need to fill gaps. My question/s Are there a set of guiding principles you can recommend I focus on to improve the points above? Are there particular programming languages which I might focus on to get a broader overview? Do you think I should avoid particular styles of development, or even languages, while solidifying what might end up being part 'the basics' but hopefully 'advanced programming'? -- Sorry if this appears off topic or something but I figure you're probably some of the best people to ask.

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• Work around for MessageNotReadableException in Java

  - by Hari

  Hi, I am building a small api around the JMS API for a project of mine. Essentially, we are building code that will handle the connection logic, and will simplify publishing messages by providing a method like Client.send(String message). One of the ideas being discussed right now is that we provide a means for the users to attach interceptors to this client. We will apply the interceptors after preparing the JMS message and before publishing it. For example, if we want to timestamp a message and wrote an interceptor for that, then this is how we would apply that ...some code ... Message message = session.createMessage() ..do all the current processing on the message and set the body for(interceptor:listOfInterceptors){ interceptor.apply(message) } One of the intrerceptors we though of was to compress the message body. But when we try to read the body of the message in the interceptor, we are getting a MessageNotReadableException. In the past, I normally compressed the content before setting it as the body of the message - so never had to worry about this exception. Is there any way of getting around this exception?

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• Why should I override hashCode() when I override equals() method?

  - by Bragaadeesh

  Ok, I have heard from many places and sources that whenever I override the equals() method, I need to override the hashCode() method as well. But consider the following piece of code package test; public class MyCustomObject { int intVal1; int intVal2; public MyCustomObject(int val1, int val2){ intVal1 = val1; intVal2 = val2; } public boolean equals(Object obj){ return (((MyCustomObject)obj).intVal1 == this.intVal1) && (((MyCustomObject)obj).intVal2 == this.intVal2); } public static void main(String a[]){ MyCustomObject m1 = new MyCustomObject(3,5); MyCustomObject m2 = new MyCustomObject(3,5); MyCustomObject m3 = new MyCustomObject(4,5); System.out.println(m1.equals(m2)); System.out.println(m1.equals(m3)); } } Here the output is true, false exactly the way I want it to be and I dont care of overriding the hashCode() method at all. This means that hashCode() overriding is an option rather being a mandatory one as everyone says. I want a second confirmation.

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• How to find an embedded platform?

  - by gmagana

  I am new to the locating hardware side of embedded programming and so after being completely overwhelmed with all the choices out there (pc104, custom boards, a zillion option for each board, volume discounts, devel kits, ahhh!!) I am asking here for some direction. Basically, I must find a new motherboard and (most likely) re-implement the program logic. Rewriting this in C/C++/Java/C#/Pascal/BASIC is not a problem for me. so my real problem is finding the hardware. This motherboard will have several other devices attached to it. Here is a summary of what I need to do: Required: 2 RS232 serial ports (one used all the time for primary UI, the second one not continuous) 1 modem (9600+ baud ok) [Modem will be in simultaneous use with only one of the serial port devices, so interrupt sharing with one serial port is OK, but not both] Minimum permanent/long term storage: Whatever O/S requires + 1 MB (executable) + 512 KB (Data files) RAM: Minimal, whatever the O/S requires plus maybe 1MB for executable. Nice to have: USB port(s) Ethernet network port Wireless network Implementation languages (any O/S I will adapt to): First choice Java/C# (Mono ok) Second choice is C/Pascal Third is BASIC Ok, given all this, I am having a lot of trouble finding hardware that will support this that is low in cost. Every manufacturer site I visit has a lot of options, and it's difficult to see if their offering will even satisfy my must-have requirements (for example they sometimes list 3 "serial ports", but it appears that only one of the three is RS232, for example, and don't mention what the other two are). The #1 constraint is cost, #2 is size. Can anyone help me with this? This little task has left me thinking I should have gone for EE and not CS :-). EDIT: A bit of background: This is a system currently in production, but the original programmer passed away, and the current hardware manufacturer cannot find hardware to run the (currently) DOS system, so I need to reimplement this in a modern platform. I can only change the programming and the motherboard hardware.

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• How should I organize complex SQL views in Rails?

  - by Benjamin Oakes

  I manage a research database with Ruby on Rails. The data that is entered is primarily used by scientists who prefer to have all the relevant information for a study in one single massive table for use in their statistics software of choice. I'm currently presenting it as CSV, as it's very straightforward to do and compatible with the tools people want to use. I've written many views (the SQL kind, not the Rails HTML/ERB kind) to make the output they expect a reality. Some of these views are quite large and have a fair amount of complexity behind them. I wrote them in SQL because there are many calculations and comparisons that are more easily done with SQL. They're currently loaded into the database straight from a file named views.sql. To get the requested data, I do a select * from my_view;. The views.sql file is getting quite large. Part of the problem is that we're still figuring out what the data we collect means, so there's a lot of changes being made to the views all the time -- and a ton of them are being created. Many of them need to be repeatable. I've recently run into issues organizing and testing these views. Rails works great for user interface stuff and business logic, but I'm not aware of much existing structure for handling the reporting we require. Some options I've thought of: Should I move them into the most relevant models somehow? Several of the views interact with each other, which makes this situation more complex than just doing a single find_by_sql, so I don't know if they should only be part of the model. Perhaps they should be treated as a "view" in the MVC sense? (That is, they could be moved into app/views/ and live alongside the HTML, perhaps as files named something like my_view.csv.sql which return CSV.) How would you deal with a complex reporting problem like this?

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• Collision of dot and line in 2D space

  - by Anderiel

  So i'm trying to make my first game on android. The thing is i have a small moving ball and i want it to bounce from a line that i drew. For that i need to find if the x,y of the ball are also coordinates of one dot from the line. I tried to implement these equations about lines x=a1 + t*u1 y=a2 + t*u2 = (x-a1)/u1=(y-a2)/u2 (t=t which has to be if the point is on the line) where x and y are the coordinates im testing, dot[a1,a2] is a dot that is on the line and u(u1,u2) is the vector of the line. heres the code: public boolean Collided() { float u1 =Math.abs(Math.round(begin_X)-Math.round(end_X)); float u2 =Math.abs(Math.round(begin_Y)-Math.round(end_Y)); float t_x =Math.round((elect_X - begin_X)/u1); float t_y =Math.round((elect_Y - begin_Y)/u2); if(t_x==t_y) { return true; } else { return false; } } points [begin_X,end_X] and [begin_Y,end_Y] are the two points from the line and [elect_X,elect_Y] are the coordinates of the ball theoreticaly it should work, but in the reality the ball most of the time just goes straigth through the line or bounces somewhere else where it shouldnt

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• Some languages don't work when using Word 2007 Spellcheck from Interop

  - by Tridus

  I'm using the Word 2007 spellchecker via Interop in a VB.net desktop app. When using the default language (English), it works fine. If I set the language to French via LanguageId, it also works. But if I set it to French (Canadian) (Word.WdLanguageID.wdFrenchCanadian), it doesn't work. There's no error message, it simply runs and says the document contains no errors. I know it does, if I paste the exact same text into Word itself and run it with the French (Canadian) dictionary, it finds errors. Just why that dictionary doesn't work is kind of a mystery to me. Full code below: Public Shared Function SpellCheck(ByVal text As String, ByVal checkGrammar As Boolean) As String ' If there is no data to spell check, then exit sub here. If text.Length = 0 Then Return text End If Dim objWord As Word.Application Dim objTempDoc As Word.Document ' Declare an IDataObject to hold the data returned from the ' clipboard. Dim iData As IDataObject objWord = New Word.Application() objTempDoc = objWord.Documents.Add objWord.Visible = False ' Position Word off the screen...this keeps Word invisible ' throughout. objWord.WindowState = 0 objWord.Top = -3000 ' Copy the contents of the textbox to the clipboard Clipboard.SetDataObject(text) ' With the temporary document, perform either a spell check or a ' complete ' grammar check, based on user selection. With objTempDoc .Content.Paste() .Activate() .Content.LanguageID = Word.WdLanguageID.wdFrenchCanadian If checkGrammar Then .CheckGrammar() Else .CheckSpelling() End If ' After user has made changes, use the clipboard to ' transfer the contents back to the text box .Content.Copy() iData = Clipboard.GetDataObject If iData.GetDataPresent(DataFormats.Text) Then text = CType(iData.GetData(DataFormats.Text), _ String) End If .Saved = True .Close() End With objWord.Quit() Return text End Function

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• jQuery AJAX chained calls + Celery in Django

  - by user1029968

  Currently clicking one of the links in my application, triggers AJAX call (GET) that - if succeeds - triggers the second one and this second one - if succeeds - calls the third one. This way user can be informed which part of process started when clicking the link is currently ongoing. So in the template file in Django project, click callback body for link mentioned looks like below: $("#the-link").click(function(item)) { // CALL 1 $.ajax({ url: {% url ajax_call_1 %}, data: { // something } }) .done(function(call1Result) { // CALL 2 $.ajax({ url: {% url ajax_call_1 %}, data: { // call1Result passed here to CALL 2 } }) .done(function(call2Result) { // CALL 3 $.ajax({ url: {%url ajax_call_3 %}, data: { // call2Result passed here to CALL 3 } }) .done(function(call3Result) { // expected result if everything went fine console.log("wow, it worked!"); console.log(call3Result); }) .fail(function(errorObject) { console.log("call3 failed"); console.log(errorObject); } }) .fail(function(errorObject)) { console.log("call2 failed"); console.log(errorObject); } }) .fail(function(errorObject) { console.log("call1 failed"); console.log(errorObject); }); }); This works fine for me. The thing is, I'd like to prevent interrupting the following calls if the user closes the browser and the calls are not finished (as it will take some time to finish all three), as there is some additional logic in Django view functions called in each GET request. For example, if user clicks the link and closes the browser during CALL 1, is it possible to somehow go on with the following CALL 2 and CALL 3? I know that normally I'd be able to use Celery Task to process the function but is it still possible here with the chained calls mentioned? Any help is much appreciated!

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• I want to input JSONObject from jquery.post() to a a simple JS chart(bar chart)?

  - by ann-stack

  HI I am very new to both json and js charts. In the example of bar chart, they are giving a hard coded array like this, var myData = new Array(['U.S.A.', 69.5], ['Canada', 2.8], ['Japan & SE.Asia', 5.6] ); var myChart = new JSChart('graph', 'bar'); myChart.setDataArray(myData); Instead of that I want to use the response of $.post() method which is in json. Here is the piece of code. var myData=[]; $.post("JSONServlet", function(data) { $.each(data.Userdetails, function(i, data) { myData[i] = []; myData[i]['text'] = data['firstname']; myData[i]['id'] = data['ssn']; alert("first name " +myData[i]['text']+ " salary " +myData[i]['id']); // I am getting correct data here, but how to assign this myData to barchart }); }, "json"); is this the logic to use or how else can i get username and salary from the response and pass it to the barchart. Please help. I am stuck with this. thanks in advance.

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• Can I delay the keyup event for jquery?

  - by Paul

  I'm using the rottentomatoes movie API in conjunction with twitter's typeahead plugin using bootstrap 2.0. I've been able to integerate the API but the issue I'm having is that after every keyup event the API gets called. This is all fine and dandy but I would rather make the call after a small pause allowing the user to type in several characters first. Here is my current code that calls the API after a keyup event: var autocomplete = $('#searchinput').typeahead() .on('keyup', function(ev){ ev.stopPropagation(); ev.preventDefault(); //filter out up/down, tab, enter, and escape keys if( $.inArray(ev.keyCode,[40,38,9,13,27]) === -1 ){ var self = $(this); //set typeahead source to empty self.data('typeahead').source = []; //active used so we aren't triggering duplicate keyup events if( !self.data('active') && self.val().length > 0){ self.data('active', true); //Do data request. Insert your own API logic here. $.getJSON("http://api.rottentomatoes.com/api/public/v1.0/movies.json?callback=?&apikey=MY_API_KEY&page_limit=5",{ q: encodeURI($(this).val()) }, function(data) { //set this to true when your callback executes self.data('active',true); //Filter out your own parameters. Populate them into an array, since this is what typeahead's source requires var arr = [], i=0; var movies = data.movies; $.each(movies, function(index, movie) { arr[i] = movie.title i++; }); //set your results into the typehead's source self.data('typeahead').source = arr; //trigger keyup on the typeahead to make it search self.trigger('keyup'); //All done, set to false to prepare for the next remote query. self.data('active', false); }); } } }); Is it possible to set a small delay and avoid calling the API after every keyup?

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• movieClip in Array displays null, and aren't showing up on stage.addChild(Array[i])

  - by jtdino

  i am new to Actionscript3, i need to know why i keep getting Parameter child must be non-null. And my code won't display 5 enemyBlock objects onto the stage but only just one. any tips and help will be much appreciated. thanks in advance. returns: TypeError: Error #2007: Parameter child must be non-null. at flash.display::DisplayObjectContainer/addChild() at flash.display::Stage/addChild() at BlockDrop_fla::MainTimeline/EnemyBlockPos() at BlockDrop_fla::MainTimeline/frame2() // declare varibles var isEnemyMoving:Boolean = false; var enemyArray:Array; var enemyBlock:MovieClip = new EnemyBlock(); // assign EnemyBlock class to enemyBlock var enemyBlockMC:MovieClip; var count:int = 5; var mapWidth:Number = 800; var mapHeight:Number = 600; function EnemyBlockPos() :void { // assign new MovieClip not null enemyBlockMC = new MovieClip; enemyArray = new Array(); for(var i=1; i<= count; i++){ // add class to MC enemyBlockMC.addChild(enemyBlock); // randomize position enemyBlock.x = Math.round(Math.random()*mapWidth); enemyBlock.y = Math.round(Math.random()*mapHeight); // set motion enemyBlock.movement = 5; // add MC to array enemyArray.push(enemyBlockMC); } for (var w = 1; w <= enemyArray.length; w++) { addChild(enemyArray[w]); } } // endOf EnemyBlockPos

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• Adding <tr> from repeater's ItemDataBound Event

  - by nemiss

  My repeater's templates generate a table, where each item is a table row. When a very very specific condition is met (itemdata), I want to add an additional row to the table from this event. How can I do that? protected void rptData_ItemDataBound(object sender, RepeaterItemEventArgs e) { if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem) { bool tmp = bool.Parse(DataBinder.Eval(e.Item.DataItem, "somedata").ToString()); if (!tmp && e.Item.ItemIndex != 0) { //Add row after this item } } } I can use e.Item.Controls.Add() and add TableRow but for that I need to locate a table right? How can I solve that? UPDATE I will explain now why I need this: I am creating a sort of message board, where data entries are displayed in a tabled style. The first items in the table are "important" items after those items, i want to add this row. I could solved it using 2 repeaters, where the first repeater will be bounded to pinned items, and the second repeater will be bounded to refular items. But I don't want to have to repeaters nor I want to complex the business logic for separating the fetched data to pinned and not-pinned collection. I think the best opton is to do it "onfly", using one repeater and one datasource.

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• List local printers

  - by vladimir

  hi all, i am using this routine to list the local printers installed on on a machine... var p: pointer; hpi: _PRINTER_INFO_2A; hGlobal: cardinal; dwNeeded, dwReturned: DWORD; bFlag: boolean; i: dword; begin p := nil; EnumPrinters(PRINTER_ENUM_LOCAL, nil, 2, p, 0, dwNeeded, dwReturned); if (dwNeeded = 0) then exit; GetMem(p,dwNeeded); if (p = nil) then exit; bFlag := EnumPrinters(PRINTER_ENUM_LOCAL, nil, 2, p, dwneeded, dwNeeded, dwReturned); if (not bFlag) then exit; CbLblPrinterPath.Properties.Items.Clear; for i := 0 to dwReturned - 1 do begin CbLblPrinterPath.Properties.Items.Add(TPrinterInfos(p^)[i].pPrinterName); end; FreeMem(p); TPrinterInfos(p^)[i].pPrinterName returns a 'P' for printer name. i have a PdfCreator installed as a printer. TPrinterInfos is an array of _PRINTER_INFO_2A. how can i fix this?

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• Stop image from tiling

  - by Glen Morse

  I have a procedure: procedure DrawSolidHexImage(Target: TCanvas; { Canvas to draw hex on } Fillstyle : TBrushStyle; { How to fill the hex } Fillcolor : TColor; { Color to fill it } fillimage : Tbitmap; { Image to show} Linestyle : TPenStyle; { What kind of lines } LineColor : Tcolor; { What color for lines } x,y,radius: integer; { Position and size of Hex } button : boolean); { Make hexes look like buttons? } When I use this, the image is tiled to fill the area. Is there something I can add or must remove to make it not tile? Thus not repeating the image. Maybe make it center? The Code in which I use DrawSolidHexImage looks like: procedure THexMap.ImageAHex(ImageWanted : TBitmap; HexPatternWanted: TBrushStyle; MapLocation:TPoint); var p0:TPoint; begin if FHexMapOn and FDrawSolidMap and (not UseSavedMap) then begin with TempMap.canvas do p0 := ConvertCoords(Point(MapLocation.x,MapLocation.y),ptROWCOL); DrawSolidHexImage(TempMap.Canvas,HexPatternWanted,clGray, Imagewanted,psSolid,LineColor,p0.x,p0.y,hexradius,hex3d); Refresh; end; end;

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• Maven: Repository no longer exists! Now what?

  - by pek

  I have just begun my journey in Maven2 and found the dependency repositories logic a little weird... As far as I understand, I need to point Maven to a repository from which it can fetch the various POMs found in my dependencies. In other words, instead of downloading all the dependencies in my lib folder, as I did in the Ant era, I now have to look into various Maven repositories and, hopefully, find what I need. OK, thanks to MVNBrowser things get a little easier. But! What if the Maven repository no longer exists? For example, I use Slick in my project. Among the other dependencies, slick uses JNLP (for some reason). The artifact for jnlp is: <dependency> <groupId>javax.jnlp</groupId> <artifactId>jnlp</artifactId> <version>1.2</version> </dependency> According to MVNBrowser, javax.jnlp can only be found in one repository, Freehep. Which is no longer available. So now what?

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• JDBC call not executing

  - by dbyrne

  I am working on one of the DAOs for a medium sized web application. Unfortunately, it contains very convoluted logic, and makes hundreds of JDBC stored proc calls in loops. This is out of my control. I am working on a method inside the DAO which makes a single JDBC call. The simplified version of what this method looks like is this: DriverManager.registerDriver(new com.sybase.jdbc2.jdbc.SybDriver()); Connection con = DriverManager.getConnection((String)connectionDetails.get("DATABASE_URL") (String)connectionDetails.get("USERID"), (String)connectionDetails.get("PASSWORD")); String sqlToExecute = "{call " + STORED_PROC + "(?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)}"; CallableStatement stmt = con.prepareCall(sqlToExecute); //Maybe I should try calling clearParameters here? stmt.setString(1,someData); //....Set of parameters.... if (!stmt.execute()) { //execute method never returns false } stmt.close(); Its pretty much a textbook JDBC call. All this stored proc does is insert a single row. Here is where things get crazy: This code works when you run it through a debugger line by line, but fails when you run it "full speed". Not only does it fail, but it doesn't throw any exception! The execute method always returns true. It just breezes right through the JDBC call without inserting a row to the database. If you go through the log files, copy the stored proc call and run it manually, it works (just like it does in debug mode). Whats strange is that the rest of the DAO, with all its hundreds of looped stored proc calls, works fine. My thinking is that Connection or CallableStatement is caching some value behind the scenes that is screwing things up. Has anyone ever seen anything like this before? A JDBC call failing with no exceptions? I know it will be impossible to provide a complete solution to this without seeing the whole application, I am just looking for suggestions on possible issues to investigate.

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• How to do HABTM management with auto completion in Rails?

  - by Andrei

  I am looking for a good solution for a probably typical problem of managing models with HABTM association in Rails. Let's assume that we have two models -- products and categories: Products has_many :categorizations has_many :categories, :through => :categorizations Categories has_many :categorizations has_many :products, :through => :categorizations Categorization belongs_to :product belongs_to :category Pat Shaughnessy is developing modified auto_complete plugin which can allow to manage one-to-many (and many-to-many) association: For someone that would be enough, but I don't really like so many text fields. I guess it is possible to combine the Ryan Bates' screencasts used by Pat in a slightly different way, namely, using one text field with autocomplete: Also it would be better to remove from the list of suggested tasks (one-to-many), or products|categories (many-to-many) those which have been already added. In the case of products-categories relationship, such auto completion would be used both in the form for product, and in the form for category. I hope that there is an existing plugin for that. I am not very experienced in Ruby, and don't really know how to implement such logic by myself. Any help is appreciated!

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• Scala newbie vproducer/consumer attempt running out of memory

  - by Nick

  I am trying to create a producer/consumer type Scala app. The LoopControl just sends a message to the MessageReceiver continually. The MessageReceiver then delegates work to the MessageCreatorActor (whose work is to check a map for an object, and if not found create one and start it up). Each MessageActor created by this MessageCreatorActor is associated with an Id. Eventually this is where I want to do business logic. But I run out of memory after 15 minutes. Its finding the cached actors,but quickly runs out of memory. Any help is appreciated. Or any one has any good code on producers consumers doing real stuff (not just adding numbers), please post. import scala.actors.Actor import java.util.HashMap import scala.actors.Actor._ case object LoopControl case object MessageReceiver case object MessageActor case object MessageActorCreator class MessageReceiver(msg: String) extends Actor { var messageActorMap = new HashMap[String, MessageActor] val messageCreatorActor = new MessageActorCreator(null, null) def act() { messageCreatorActor.start loop { react { case MessageActor(messageId) => if (msg.length() > 0) { var messageActor = messageActorMap.get(messageId); if(messageActor == null) { messageCreatorActor ! MessageActorCreator(messageId, messageActorMap) }else { messageActor ! MessageActor } } } } } } case class MessageActorCreator(msg:String, messageActorMap: HashMap[String, MessageActor]) extends Actor { def act() { loop { react { case MessageActorCreator(messageId, messageActorMap) => if(messageId != null ) { var messageActor = new MessageActor(messageId); messageActorMap.put(messageId, messageActor) println(messageActorMap) messageActor.start messageActor ! MessageActor } } } } } class LoopControl(messageReceiver:MessageReceiver) extends Actor { var count : Int = 0; def act() { while (true) { messageReceiver ! MessageActor ("00-122-0X95-FEC0" + count) //Thread.sleep(100) count = count +1; if(count > 5) { count = 0; } } } } case class MessageActor(msg: String) extends Actor { def act() { loop { react { case MessageActor => println() println("MessageActor: Got something-> " + msg) } } } } object messages extends Application { val messageReceiver = new MessageReceiver("bootstrap") val loopControl = new LoopControl(messageReceiver) messageReceiver.start loopControl.start }

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• need to change TextBox.Text inside TextChanged, something forces form close

  - by Istrebitel

  I am making a TextBox behave like if it could store a null value. In order to do that, i have a variable NullMode that indicates wether the value is stored is Null, and in TextChanged i set that to false, and on specific user action i set it to true and Text to a value that indicates that there is null inside the textbox. Then, based on NullMode, textbox is drawn differently. Now, i have a semaphore-like approach in order to prevent event handle from firing when i dont need it. Here is how it looks: private void input_TextChanged(object sender, EventArgs e) { if (_preventTextBoxEvents) return; _preventTextBoxEvents = true; //if (NullMode) // Text = ""; NullMode = false; ValidateInput(); _preventTextBoxEvents = false; } Now, if i need to set a textbox text to something that should show while in nullmode, i just set _preventTextBoxEvents before i do to true and it works all right. BUT! I need to also remove the text when user tries to input something into the textbox! So i need to set Text to "". Problem is, if i uncomment that, form is closed after the event handler exits. I cannot prevent it (e.Cancel = true in FormClosing doesnt help!) and do not understand what can be causing it. There is no error message too (and i'm not doing try-catch). My logic, when i do Text="". OnTextChanged should fire, it should call my TextChanged and it will see _preventTextBoxEvents is true and exit, so there would be no stack overflow / infinite recursion. What is going on?

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• Determining polygon intersection and containment

  - by Victor Liu

  I have a set of simple (no holes, no self-intersections) polygons, and I need to check that they don't intersect each other (one can be entirely contained in another; that is okay). I can check this by simply checking the per-vertex inside-ness of one polygon versus other polygons. I also need to determine the containment tree, which is the set of relationships that say which polygon contains any given polygon. Since no polygon can intersect any other, then any contained polygon has a unique container; the "next-bigger" one. In other words, if A contains B contains C, then A is the parent of B, and B is the parent of C, and we don't consider A the parent of C. The question: How do I efficiently determine the containment relationships and check the non-intersection criterion? I ask this as one question because maybe a combined algorithm is more efficient than solving each problem separately. The algorithm should take as input a list of polygons, given by a list of their vertices. It should produce a boolean B indicating if none of the polygons intersect any other polygon, and also if B = true, a list of pairs (P, C) where polygon P is the parent of child C. This is not homework. This is for a hobby project I am working on.

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• MVVM: where is the best place to integrate an id counter, in ViewModel or Repository or... ?

  - by msfanboy

  Hello, I am using http://loungerepo.codeplex.com/ this library needs a unique id when I persist my entities to the repository. I decided for integer not Guid. The question is now where do I retrieve a new integer and how do I do it? This is my current approach in the SchoolclassAdministrationViewModel.cs: public SchoolclassAdministrationViewModel() { _schoolclassRepo = new SchoolclassRepository(); _pupilRepo = new PupilRepository(); _subjectRepo = new SubjectRepository(); _currentSchoolclass = new SchoolclassModel(); _currentPupil = new PupilModel(); _currentSubject = new SubjectModel(); ... } private void AddSchoolclass() { // get the last free id for a schoolclass entity _currentSchoolclass.SchoolclassID = _schoolclassRepo.LastID; // add the new schoolclass entity to the repository _schoolclassRepo.Add(SchoolclassModel.SchoolclassModelToSchoolclass(_currentSchoolclass)); // add the new schoolclass entity to the ObservableCollection bound to the View Schoolclasses.Add(_currentSchoolclass); // Create a new schoolclass entity and the bound UI controls content gets cleaned CurrentSchoolclass = new SchoolclassModel(); } public class SchoolclassRepository : IRepository<Schoolclass> { private int _lastID; public SchoolclassRepository() { _lastID = FetchLastId(); } public void Add(Schoolclass entity) { //repo.Store(entity); } private int FetchLastId() { return // repo.GetIDOfLastEntryAndDoInc++ } public int LastID { get { return _lastID; } } } Explanation: Every time the user switches to the SchoolclassAdministrationViewModel which is datatemplated with a UserControl the saVM Ctor is called and the schoolclass repository is created wherein the FetchLastId() is called and I am up to date with the last ID doing a inc++ on it to get the free one... Do you have any better ideas? What I do not like about my current apporach: -Having a private method in repositry class because a repositry is to fetch data only not "entity logic" like the counter - Having to access from the ViewModel a public property - located in the repository -, actually its not the ViewModel concern to get a entity id and assign it. Actually the ViewModel should ask for a schoolclass POCO and get a SchoolclassModel to bind to the UI. But then I have again to re-read the Schoolclass properties into the SchoolclassModel properties what I want to avoid.

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• I need a fast runtime expression parser

  - by Chris Lively

  I need to locate a fast, lightweight expression parser. Ideally I want to pass it a list of name/value pairs (e.g. variables) and a string containing the expression to evaluate. All I need back from it is a true/false value. The types of expressions should be along the lines of: varA == "xyz" and varB==123 Basically, just a simple logic engine whose expression is provided at runtime. UPDATE At minimum it needs to support ==, !=, , =, <, <= Regarding speed, I expect roughly 5 expressions to be executed per request. We'll see somewhere in the vicinity of 100/requests a second. Our current pages tend to execute in under 50ms. Usually there will only be 2 or 3 variables involved in any expression. However, I'll need to load approximately 30 into the parser prior to execution. UPDATE 2012/11/5 Update about performance. We implemented nCalc nearly 2 years ago. Since then we've expanded it's use such that we average 40+ expressions covering 300+ variables on post backs. There are now thousands of post backs occurring per second with absolutely zero performance degradation. We've also extended it to include a handful of additional functions, again with no performance loss. In short, nCalc met all of our needs and exceeded our expectations.

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• Midiplayer stops playing sounds after 16 notes.

  - by user349673

  Hi. I am currently programming a Piano Keyboard editor, much like the one you can find in Cubase, Logic, Reason etc.. I have this big grid, double array new int [13][9], which makes it 13 rows, 9 columns. The first column [0-12][0] is the Keyboard, at the top there's "high C" (midi note 72) and at the bottom there's "low C" (midi note 60). That column is an array of JButtons and when you press for example "low C", note 60 is being played by the Synthesizer. I've gotten this to work pretty OK as for now, but one problem I have is that I can only play 16 notes in a row, then it's like the Synthesizer shuts down or something. Do you guys have ANY idea of what the problem is? A bit of the code: import java.awt.*; import javax.swing.*; import java.awt.event.*; import java.util.*; import javax.sound.midi.*; actionPerformed(ActionEvent ae){ for(int i = 0; i<13; i++){ if(o== instr[i]){//instr is the button array SpelaTangent(i); } } } public void SpelaTangent(int tangent){ int [] klaviatur = new int[13]; for(int i = 0; i<13; i++){ klaviatur[i] = (72-i); } try { Synthesizer synth = MidiSystem.getSynthesizer(); synth.open(); final MidiChannel[] mc = synth.getChannels(); Instrument[] instrument = synth.getDefaultSoundbank().getInstruments(); synth.loadInstrument(instrument[1]); mc[0].noteOn(klaviatur[tangent],350); mc[0].noteOff(klaviatur[tangent],350); } catch (MidiUnavailableException e) {} } Help is very much appreciated!

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• Disable validation in an object in Ruby on Rails

  - by J. Pablo Fernández

  I have an object which whether validation happens or not should depend on a boolean, or in another way, validation is optional. I haven't found a clean way to do it. What I'm currently doing is this (disclaimer: you cannot unsee, leave this page if you are too sensitive): def valid? if perform_validation super else super # Call valid? so that callbacks get called and things like encrypting passwords and generating salt in before_validation actually happen errors.clear # but then clear the errors true # and claim ourselves to be valid. This is super hacky! end end Any better ways? Before you point to the :if argument of many validations, this is for a user model which is using authlogic so it has a lot of validation rules. You can stop reading here if you belive me. If you don't, authlogic already sets some :ifs like: :if => :email_changed? which I have to turn into :if => Proc.new {|user| user.email_changed? and user.perform_validation} and in some other cases, since I'm also using authlogic-oid (OpenID) I just don't have control over the :if, authlogic-oid sets it in a way I cannot change it (in time) without further monkey patching. So I have to override seemingly unrelated functions, catch exceptions if a method doesn't exist, etc. The previous hacky solution if the best of my two attempts.

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• ASP.NET MVC editor template for property

  - by Idsa

  Usually I render my forms by @Html.RenderModel, but this time I have a complex rendering logic and I render it manually. I decided to create a editor template for one property. Here is the code (copy pasted from default object editor template implementation): <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl" %> <% var modelMetadata = ViewData.ModelMetadata; %> <% if (modelMetadata.HideSurroundingHtml) { %> <%= Html.Editor(modelMetadata.PropertyName) %> <% } else { %> <% if (!String.IsNullOrEmpty(Html.Label(modelMetadata.PropertyName).ToHtmlString())) { %> <div class="editor-label"><%= Html.Label(modelMetadata.PropertyName) %></div> <% } %> <div class="editor-field"> <%= Html.Editor(modelMetadata.PropertyName) %> <%= Html.ValidationMessage(modelMetadata.PropertyName) %> </div> <% } %> And here is how I use it: @Html.EditorFor(x => x.SomeProperty, "Property") //"Property" is template above But it didn't work: labels are rendered regardless of DisplayName and editors are not rendered at all (in Watches Html.Editor(modelMetadata.PropertyName shows empty string). What am I doing wrong?

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