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  • Good concurrency example of Java vs. Clojure

    - by Michiel Borkent
    Clojure is said to be a language that makes multi-thread programming easier. From the Clojure.org website: Clojure simplifies multi-threaded programming in several ways. Now I'm looking for a non-trivial problem solved in Java and in Clojure so I can compare/contrast their simplicity. Anyone?

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  • EventAggregator, is it thread-safe?

    - by pfaz
    Is this thread-safe? The EventAggregator in Prism is a very simple class with only one method. I was surprised when I noticed that there was no lock around the null check and creation of a new type to add to the private _events collection. If two threads called GetEvent simultaneously for the same type (before it exists in _events) it looks like this would result in two entries in the collection. /// <summary> /// Gets the single instance of the event managed by this EventAggregator. Multiple calls to this method with the same <typeparamref name="TEventType"/> returns the same event instance. /// </summary> /// <typeparam name="TEventType">The type of event to get. This must inherit from <see cref="EventBase"/>.</typeparam> /// <returns>A singleton instance of an event object of type <typeparamref name="TEventType"/>.</returns> public TEventType GetEvent<TEventType>() where TEventType : EventBase { TEventType eventInstance = _events.FirstOrDefault(evt => evt.GetType() == typeof(TEventType)) as TEventType; if (eventInstance == null) { eventInstance = Activator.CreateInstance<TEventType>(); _events.Add(eventInstance); } return eventInstance; }

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  • Does "delegate" mean a type or an object?

    - by Michal Czardybon
    Reading from MSDN: "A delegate is a type that references a method. Once a delegate is assigned a method, it behaves exactly like that method." Does then "delegate" mean a type or an object?! ...It cannot be both. It seems to me that the single word is used in two different meanings: a type containing a reference to a method of some specified signature, an object of that type, which can be actually called like a method. I would prefer a more precise vocabulary and use "delegate type" for the first case. I have been recently reading a lot about events and delegates and that ambiguity was making me confused many times. Some other uses of "delegate" word in MSDN in the first meaning: "Custom event delegates are needed only when an event generates event data" "A delegate declaration defines a class that is derived from the class System.Delegate" Some other uses of "delegate" word in MSDN in the second meaning: "specify a delegate that will be called upon the occurrence of some event" "Delegates are objects that refer to methods. They are sometimes described as type-safe function pointers" What do you think? Why did people from Microsoft introduced this ambiguity? Am I the only person to have conceptual problems with different notions being referenced with the same word.

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  • MySQL query against pseudo-key-value pair data in WordPress custom query

    - by andrevr
    I'm writing a custom WordPress query to use some of the data which the Woothemes Diarise theme creates. Diarise is an event planner theme with calendar blah, blah... and uses custom fields to store the event start and end dates in WP custom fields in the *wp_postmeta* table, which implements a key-value store. So for each post in the "event" category, there are 2 records in *wp_postmeta*, named *event_start_date* and *event_end_date* that I'm interested in. The task is to compare a tourist's arrival and departure dates with the start and end dates of events, yielding a what's on list of events available. We thought we'd killed it with a grand flash of logic, that goes like this: Disregard any event that ends before the tourist arrives, and any that begin after the departure date. I wrote this query: SELECT wposts.* FROM wp_posts wposts LEFT JOIN wp_postmeta wpostmeta ON wposts.ID = wpostmeta.post_id LEFT JOIN wp_term_relationships ON (wposts.ID = wp_term_relationships.object_id) LEFT JOIN wp_term_taxonomy ON (wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id) WHERE wp_term_taxonomy.taxonomy = 'category' AND wp_term_taxonomy.term_id IN(3,4) AND ( wpostmeta.meta_key = 'event_start_date' AND NOT ( concat(subst(wpostmeta.meta_value,7,4),'-',subst(wpostmeta.meta_value,4,2),'-',subst(wpostmeta.meta_value,1,2) > '2010-07-31' ) ) AND ( wpostmeta.meta_key = 'event_end_date' AND NOT ( concat(subst(wpostmeta.meta_value,7,4),'-',subst(wpostmeta.meta_value,4,2),'-',subst(wpostmeta.meta_value,1,2) < '2010-05-01' ) ) ) ORDER BY wpostmeta.meta_value ASC And, of course it returns no records. The problem I believe is in the dual reference to wpostmeta.meta_key, but how to get around that?

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  • Does OOP make sense for small scripts?

    - by Fabian
    I mostly write small scripts in python, about 50 - 250 lines of code. I usually don't use any objects, just straightforward procedural programming. I know OOP basics and I have used object in other programming languages before, but for small scripts I don't see how objects would improve them. But maybe that is just my limited experience with OOP. Am I missing something by not trying harder to use objects, or does OOP just not make a lot of sense for small scripts?

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  • Looking for early paper about compiling object-oriented code

    - by Robert Kosara
    I remember reading a paper a long time ago that talked about object-oriented programming. I believe that this was from the early 1980s or perhaps even before then. This was at the time when object-oriented programming was still done through pre-processors, and one thing that stuck with me is this: it argued that you could write code in either procedural or object-oriented fashion, and after preprocessing/compiling, you would end up with the exact same machine code. Does anybody know which paper I'm talking about?

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  • How to set font Bold, Italic, and Underlined in Qt?

    - by Hanny
    I want to make a program that's like a simple text editor using Qt 4.6.2. When the user block any text in a TextEdit and click on a button, the text will be bold/italic/underlined depend on the button.. I'm a beginner in Qt Programming, so if Possible, can you insert the programming code in Qt to do that? Please answer this ASAP,, thank you very much!! :)

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  • Linux library that handles both GUI/textual mode user interfaces

    Hello, I am looking for some Linux library/programming language that can be used on a variety of Linux platforms and can operate in both textual and GUI mode interfaces. For example YCP (the Yast programming language) will display in GUI if in Gnome/KDE environment and run in text/ncurses mode when display is not available. The problem is that YCP is SUSE specific. Any ideas will be appreciated!

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  • call back function set by JS settimeout doesn't work in IE8....

    - by NAG
    <html <head <script function addEvent( obj, type, fn ) { if ( obj.attachEvent ) { obj['e'+type+fn] = fn; obj[type+fn] = function(){obj['e'+type+fn]( window.event );} obj.attachEvent( 'on'+type, obj[type+fn] ); } else obj.addEventListener( type, fn, false ); } </script </head <body <!-- HTML for example event goes here -- <div id="mydiv" style="border: 1px solid black; width: 100px; height: 100px; margin-top: 10px;"</div <script // Script for example event goes here addEvent(document.getElementById('mydiv'), 'contextmenu', function(event) { display_short('right-clicked (contextmenu)'); }); function display_short(str) { clearTimeout(); document.getElementById('mydiv').innerHTML = str; if (str != '') alert("hello"); setTimeout("display_short('abcd')", 1000); } </script </body </html Behaves diffrently in IE and FF when you right click on the div area. In ff display_short will be called for evry 1 sec eventhough you dont release right click but in IE it will not call display_short if you dont release right click. But i expect in IE it should call display_short for every 1 sec if you dont release also. Is there any solution for this?

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  • Actionscript Enterframe Movement

    - by David
    I am trying to make accelerated movement, but I am running into a problem that, for the life of me, I cannot understand. My class definition: public class Player extends MovieClip { private var stageRef:Stage; private var key:KeyObject; private var acceleration:int = .5; private var curSpeed:int = 0; public function Player(stageRef:Stage) { this.stageRef = stageRef; addEventListener(Event.ENTER_FRAME, enterFrame); key = new KeyObject(stageRef); } public function enterFrame(e:Event) : void { if(key.isDown(key.RIGHT)) { x += 5; } } } This works to move my position in the x direction at a constant rate. However, if I change enterFrame to public function enterFrame(e:Event) : void { if(key.isDown(key.RIGHT)) { x += acceleration; } } No movement occurs. Is there something going on in the event I do not understand? Why is it that I can have x increased by a constant value but not a constant value as defined in a variable in the class? Is it a scope issue?

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  • Actionscript: How Can I Know When The Source Property Of An Image Is Completely Updated

    - by Joshua
    var I:Image=new Image(); I.source='C:\\Abc.png'; var H:int=I.height; H is always Zero! I am presuming this is because the image hasn't finished reading the png file off the disk yet. What event can I monitor to know when it's width and height will have the right values? The 'Complete' event only seems to work for DOWNLOADED images. The 'Render' event happens EVERY FRAME. The (undocumented?) 'sourceChanged', happens as soon as source changes, and has the same problem! What event do I watch that will let me know when the image's width and height properties will have valid values? Or is there some Synchronous version of I.source='xxx.png', that I don't know about? P.S. Yes, I know I shouldn't use "C:\" in an Air Program. This was just for illustrative purposes, so that you won't suggest I use "Complete", which never even seems to fire when the file indicated by source is local.

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  • get the javascript variable value to Code Behind Asp.net

    - by Siddiq Baig
    i am trying to pass the javascript variable value to hidden feild from code behind by onclientclick event.. i have button that have both client and server side onclick event <asp:Button ID="btnSave" runat="server" Text="Save" class="buttonstyle" onclick="btnSave_Click" OnClientClick="otherdata()" /> i want to get the javascript value in codebehind from OnClientClick event and then want to insert that value to database table from Onclick event function otherdata() { var hv = $('input[id$=hdnOthers]').val(); var $arrT = $('#<%=gv_Others.ClientID %>').find('input:text[id$="txtEmp"]'); var count = []; for (var i = 0; i < 10; i++) { var $txt = $arrT[i]; count[i] = $($txt).val(); } hv = count; alert(hv); } i am getting the value in alert and assigning the value to hidden field but problem is that i am not getting the value in hidden field from code behind.. although i have already pass the value to hidden field from javascript so why i am not getting that value from code behind.. protected void Insert_OtherServices() { dsJobCardTableAdapters.Select_OtherServiceTableAdapter dsother = new dsJobCardTableAdapters.Select_OtherServiceTableAdapter(); string hdn = hdnOthers.Value; dsother.Insert_OtherService(hdn); }

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  • i integer does not +1 the 1st time

    - by Hwang
    I have a gallery where it will load an image after a previous image is loaded, so every time 'i' will +1 so that it could move to the next image. This code works fine on my other files, but I dunno why it doesn't work for the current file. Normally if I trace 'i' the correct will be 0,1,2,3,4,5,6... etc adding on till the limit, but this files its 'i' repeat the 1st number twice, only it continues to add 0,0,1,2,3,4,5,6...etc The code is completely the same with the other file I'm using, but I don't know why it just doesn't work here. The code does not seems to have any problem. Anyway i can work around this situation? private var i:uint=0; private function loadItem():void { if (i<myXMLList.length()) { loadedPic=myXMLList[i].thumbnails; galleryLoader = new Loader(); galleryLoader.load(new URLRequest(loadedPic)); galleryLoader.contentLoaderInfo.addEventListener(Event.COMPLETE,picLoaded); } else { adjustImage(); } } private function picLoaded(event:Event):void { var bmp=new Bitmap(event.target.content.bitmapData); bmp.smoothing=true; bmpArray.push(bmp); imagesArray[i].addChild(bmp); i++; loadItem(); }

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  • How would you program Pascal's triangle in R?

    - by Peter Flom
    I am reading, on my own (not for HW) about programming, and one exercise involved programming Pascal's triangle in R. My first idea was to make a list and then append things to it, but that didn't work too well. Then I thought of starting with a vector, and making a list out of that, at the end. Then I thought of making a matrix, and making a list out of that at the end. Not sure which way to even approach this. Any hints? thanks

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  • validation before ajax form submission

    - by ZX12R
    How do i introduce validation before remote_form_for submits? I have javascript function called validateForm(). I am able to call it before the AJAX request process. I tried to use return false and event.preventDefault. But there seems to be no effect. Here is what my code looks like <% remote_form_for :customer, :update =>"uxScreenLoaderDiv", :url => {:action => "login", :controller => "site"}, :html => {:id => "uxLoginForm"}, :onsubmit => "validateForm(event)" do |f| %> User name : <%= f.text_field "uxUserName", :class => "TextBox", :style => "width:100px;" %>&nbsp;* &nbsp;Password : <%= f.password_field "uxPassword", :class => "TextBox", :style => "width:100px;" %>&nbsp;* <%= f.submit "Go!", :class => "Button-Simple", :id => "uxSubmitButton" %> <% end %> the javascript function is simple as follows function validateForm(event){ return false; //event.preventDefault(); }

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  • Issue with WatchService in java 7

    - by user972590
    I'm using jdk7's WatchService API for monitoring the folder on file system.I'm sending a new file through email to that folder, when the file comes into that folder i m triggering the ENTRY_CRATE option. its working fine. But the issue is its generating two events of ENTRY_CREATE instead of one event which i'm invoking. BELOW IS THE CODE: Path dir = Paths.get(/var/mail); WatchService watcher = dir.getFileSystem().newWatchService(); dir.register(watcher, StandardWatchEventKinds.ENTRY_CREATE); System.out.println("waiting for new file"); WatchKey watckKey = watcher.take(); List<WatchEvent<?>> events = watckKey.pollEvents(); System.out.println(events.size()); for(WatchEvent<?> event : events){ if(event.kind() == StandardWatchEventKinds.ENTRY_CREATE){ String fileCreated=event.context().toString().trim(); } } In the above code I'm gettng the events size as 2. Can any one please help me in finding out the reason why i'm getting two events.

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  • Is there any way to notify IE about changes done in registry via code?

    - by Mayur M
    Hi, I have done changes in registry (proxy settings) via Windows programming code. I have to restart (reopen) Internet Explorer each time I run the code to make those changes take effect. Is there any API in Windows programming through which I can notify Internet Explorer or Windows that changes are made to the registry and there will not be any need to reopen Internet Explorer to make those changes take effect? Thanks.

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  • Progressive enhancement of anchor tags to avoid onclick="return false;"

    - by Chris Beck
    Unobtrusive JS suggests that we don't have any onclick attributes in our HTML templates. <a href="/controller/foo/1">View Foo 1</a> A most basic progressive enhancement is to convert an that anchor tag to use XHR to retrieve a DOM fragment. So, I write JS to add an event listener for a."click" then make an XHR to a.href. Alas, the browser still wants to navigate to "/controller/foo". So, I write JS to dynamically inject a.onclick = "return false;". Still unobtrusive (I guess), but now I'm paying the the cost of an extra event handler. To avoid the cost of 2 event listeners, I could shove my function call into the onclick attribute <a href="/controller/foo/1" onclick="myXHRFcn(); return false;"> But that's grodo for all sorts of reasons. To make it more interesting, I might have 100 anchor tags that I want to enhance. A better pattern is a single listener on a parent node that relies on event bubbling. That's cool, but how do I short circuit the browser from navigating to the URL without this on every anchor node? onclick="return false;" Manipulating the href is not an option. It must stay intact so the context menu options to copy or open in new page work as expected.

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  • jQuery ajax only works first time

    - by Michael Itzoe
    I have a table of data that on a button click certain values are saved to the database, while other values are retrieved. I need the process to be continuous, but I can only get it to work the first time. At first I was using .ajax() and .replaceWith() to rewrite the entire table, but because this overwrites the DOM it was losing events associated with the table. I cannot use .live() because I'm using stopPropagation() and .live() doesn't support it due to event bubbling. I was able to essentially re-bind the click event onto the table within the .ajax() callback, but a second call to the button click event did nothing. I changed the code to use .get() for the ajax and .html() to put the results in the table (the server-side code now returns the complete table sans the <table> tags). I no longer have to rebind the click event to the table, but subsequent clicks to the button still do nothing. Finally, I changed it to .load(), but with the same (non-) results. By "do nothing" I mean while the ajax call is returning the new HTML as expected, it's not being applied to the table. I'm sure it has something to do with altering the DOM, but I thought since I'm only overwriting the table contents and not the table object itself, it should work. Obviously I'm missing something; what is it? Edit: HTML: <table id="table1" class="mytable"> <tr> <td><span id="item1" class="myitem"></span> <td><span id="item2" class="myitem"></span> </tr> </table> <input id="Button1" type="button" value="Submit" /> jQuery: $( "Button1" ).click( function() { $( "table1" ).load( "data.aspx", function( data ) { //... } ); } );

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  • How to store multiple variables from a File Input of unknown size in Java?

    - by AlphaOmegaStrife
    I'm a total beginner with my first programming assignment in Java. For our programming assignment, we will be given a .txt file of students like so: 3 345 Lisa Miller 890238 Y 2 <-(Number of classes) Mathematics MTH345 4 A Physics PHY357 3 B Bill Wilton 798324 N 2 English ENG378 3 B Philosophy PHL534 3 A Dandy Goat 746333 Y 1 History HIS101 3 A" The teacher will give us a .txt file on the day of turning it in with a list of unknown students. My problem is: I have a specific class for turning the data from the file into variables to be used for a different class in printing it to the screen. However, I do not know of a good way to get the variables from the input file for the course numbers, since that number is not predetermined. The only way I can think of to iterate over that unknown amount is using a loop, but that would just overwrite my variables every time. Also, the teacher has requested that we not use any JCL classes (I don't really know what this means.) Sorry if I have done a poor job of explaining this, but I can't think of a better way to conceptualize it. Let me know if I can clarify. Edit: public static void analyzeData() { Scanner inputStream = null; try { inputStream = new Scanner(new FileInputStream("Programming Assignment 1 Data.txt")); } catch (FileNotFoundException e) { System.out.println("File Programming Assignment 1 Data.txt could not be found or opened."); System.exit(0); } int numberOfStudents = inputStream.nextInt(); int tuitionPerHour = inputStream.nextInt(); String firstName = inputStream.next(); String lastname = inputStream.next(); String isTuitionPaid = inputStream.next(); int numberOfCourses = inputStream.nextInt(); String courseName = inputStream.next(); String courseNumber = inputStream.next(); int creditHours = inputStream.nextInt(); String grade = inputStream.next(); To show the methods I am using now, I am just using a Scanner to read from the file and for Scanner inputStream, I am using nextInt() or next() to get variables from the file. Obviously this will not work when I do not know exactly how many classes each student will have.

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  • c# wpf command pattern

    - by evan
    I have a wpf gui which displays a list of information in separate window and in a separate thread from the main application. As the user performs actions in the main window the side window is updated. (For example if you clicked page down in the main window a listbox in the side window would page down). Right now the architecture for this application feels very messy and I'm sure there is a cleaner way to do it. It looks like this: Main Window contains a singleton SideWindowControl which communicates with an instance of the SideWindowDisplay using events - so, for example, the pagedown button would work like: 1) the event handler of the button on the main window calls SideWindowControl.PageDown() 2) in the PageDown() function a event is created and thrown. 3) finally the gui, ShowSideWindowDisplay is subscribing to the SideWindowControl.Actions event handles the event and actually scrolls the listbox down - note because it is in a different thread it has to do that by running the command via Dispatcher.Invoke() This just seems like a very messy way to this and there must be a clearer way (The only part that can't change is that the main window and the side window must be on different threads). Perhaps using WPF commands? I'd really appreciate any suggestions!! Thanks

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  • Flex Tree Properties, Null Reference?

    - by mvrak
    I am pulling down a large XML file and I have no control over it's structure. I used a custom function to use the tag name to view the tree structure as a flex tree, but then it breaks. I am guessing it has something to do with my other function, one that calls attribute values from the selected node. See code. <mx:Tree x="254" y="21" width="498" height="579" id="xmllisttree" labelFunction="namer" dataProvider="{treeData}" showRoot="false" change="treeChanged(event)" /> //and the Cdata import mx.rpc.events.ResultEvent; [Bindable] private var fullXML:XMLList; private function contentHandler(evt:ResultEvent):void{ fullXML = evt.result.page; } [Bindable] public var selectedNode:Object; public function treeChanged(event:Event):void { selectedNode=Tree(event.target).selectedItem; } public function namer(item:Object):String { var node:XML = XML(item); var nodeName:QName = node.name(); var stringtest:String ="bunny"; return nodeName.localName; } The error is TypeError: Error #1009: Cannot access a property or method of a null object reference. Where is the null reference?

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  • What's beyond c,c++ and data structure?

    - by sagacious
    I have learnt c and c++ programming languages.i have learnt data structure too. Now i'm confused what to do next?my aim is to be a good programmer. i want to go deeper into the field of programming and making the practical applications of what i have learnt. So,the question takes the form-what to do next?Or is there any site where i can see advantage of every language with it's features? sorry,if there's any language error and thanks in advance.

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  • jquery focusin() and preventing bubbling.

    - by DA
    I'm showing a div via an onclick event. If you click outside the div, I want to hide it. To do so, I'm binding a one time click event on the body: $('body').one('click.myDivPopup', function(e) { ...close my div... }); Within the div itself, I tell it to not propogate events so that actually clicking within the div won't trigger a click on the body: $myDiv.click(function(e){e.stopPropagation()}); This works fine as intended. I also want to hide the div if one tabs out of the div. My thinking was that in that scenario, I could use a focusin event on the body: $('body').one('focusin.myDivPopup', function(e) { ...close my div... }); Again, I don't want the events to bubble out of the div itself, so added this: $myDiv.focusin(function(e){e.preventDefault()}); This does NOT work. Changing focus within elements within myDiv triggers the focusin event on the body. Is this maybe a bug in jQuery? If so is there a better way to accomplish this?

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  • How do I force all Tree itemrenderers to refresh?

    - by Richard Haven
    I have item renderers in an mx.controls.Tree that I need to refresh on demand. I have code in the updateDisplayList that fires for only some of the visible nodes no matter what I do. I've tried triggering a change that they should all be listening for; I have tried clearing and resetting the dataProvider and the itemRenderer properties. private function forceCategoryTreeRefresh(event : Event = null) : void { trace("forceCategoryTreeRefresh"); var prevDataProvider : Object = CategoryTree.dataProvider; CategoryTree.dataProvider = null; CategoryTree.validateNow(); CategoryTree.dataProvider = prevDataProvider; var prevItemRenderer : IFactory = CategoryTree.itemRenderer; CategoryTree.itemRenderer = null; CategoryTree.itemRenderer = prevItemRenderer as IFactory; _categoriesChangeDispatcher.dispatchEvent(new Event(Event.CHANGE)); } The nodes refresh properly when I scroll them into view (e.g. the .data gets set), but I cannot force the ones that already exist to refresh or reset themselves. Any ideas?

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