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  • C# -Closure -Clarification

    - by nettguy
    I am learning C#.Can I mean closure as a construct that can adopt the changes in the environment in which it is defined. Example : List<Person> gurus = new List<Person>() { new Person{id=1,Name="Jon Skeet"}, new Person{id=2,Name="Marc Gravell"}, new Person{id=3,Name="Lasse"} }; void FindPersonByID(int id) { gurus.FindAll(delegate(Person x) { return x.id == id; }); } The variable id is declared in the scope of FindPersonByID() but t we still can access the local variable id inside the anonymous function (i.e) delegate(Person x) { return x.id == id; } (1) Is my understanding of closure is correct ? (2) What are the aditional advantages can we get from closures?

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  • Qooxdoo REST JSON request problem - unexpected token and then timeout

    - by freiksenet
    Hello! I am learning Qooxdoo framework and I am trying to make it work with a small Django web service. Django webservice just returns JSON data like this: { "name": "Football", "description": "The most popular sport." } Then I use the following code to query that url: var req = new qx.io.remote.Request(url, "GET", "application/json"); req.toggleCrossDomain(); req.addListener("completed", function(e) { alert(e.getContent()); }); req.send(); Unfortunately when I execute the code I get unexpected token error and then request timeouts. Uncaught SyntaxError: Unexpected token : Native.js:91013011 qx.io.remote.RequestQueue[246]: Timeout: transport 248 Native.js:91013011 qx.io.remote.RequestQueue[246]: 5036ms > 5000ms Native.js:91013013 qx.io.remote.Exchange[248]: Timeout: implementation 249 JSLint reports that this is a valid JSON, so I wonder why Qooxdoo doesn't parse it correctly.

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  • .NET MVC: How to use .NET controls with MVC?

    - by aximili
    I am very new to MVC. I've been learning to use plain HTML or HtmlHelpers, eg. for textbox, and get the value back in the Controller using Request.Form. But how do I use .NET controls with MVC? (eg. FileUpload) (The reason I ask is I am trying to use a custom control for uploading multiple files - it's Flajaxian File Uploader, if anyone knows about it. It works with webforms, but I have no idea how this thing is gonna work with MVC.) Thanks in advance

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  • improving conversions to binary and back in C#

    - by Saad Imran.
    I'm trying to write a general purpose socket server for a game I'm working on. I know I could very well use already built servers like SmartFox and Photon, but I wan't to go through the pain of creating one myself for learning purposes. I've come up with a BSON inspired protocol to convert the the basic data types, their arrays, and a special GSObject to binary and arrange them in a way so that it can be put back together into object form on the client end. At the core, the conversion methods utilize the .Net BitConverter class to convert the basic data types to binary. Anyways, the problem is performance, if I loop 50,000 times and convert my GSObject to binary each time it takes about 5500ms (the resulting byte[] is just 192 bytes per conversion). I think think this would be way too slow for an MMO that sends 5-10 position updates per second with a 1000 concurrent users. Yes, I know it's unlikely that a game will have a 1000 users on at the same time, but like I said earlier this is supposed to be a learning process for me, I want to go out of my way and build something that scales well and can handle at least a few thousand users. So yea, if anyone's aware of other conversion techniques or sees where I'm loosing performance I would appreciate the help. GSBitConverter.cs This is the main conversion class, it adds extension methods to main datatypes to convert to the binary format. It uses the BitConverter class to convert the base types. I've shown only the code to convert integer and integer arrays, but the rest of the method are pretty much replicas of those two, they just overload the type. public static class GSBitConverter { public static byte[] ToGSBinary(this short value) { return BitConverter.GetBytes(value); } public static byte[] ToGSBinary(this IEnumerable<short> value) { List<byte> bytes = new List<byte>(); short length = (short)value.Count(); bytes.AddRange(length.ToGSBinary()); for (int i = 0; i < length; i++) bytes.AddRange(value.ElementAt(i).ToGSBinary()); return bytes.ToArray(); } public static byte[] ToGSBinary(this bool value); public static byte[] ToGSBinary(this IEnumerable<bool> value); public static byte[] ToGSBinary(this IEnumerable<byte> value); public static byte[] ToGSBinary(this int value); public static byte[] ToGSBinary(this IEnumerable<int> value); public static byte[] ToGSBinary(this long value); public static byte[] ToGSBinary(this IEnumerable<long> value); public static byte[] ToGSBinary(this float value); public static byte[] ToGSBinary(this IEnumerable<float> value); public static byte[] ToGSBinary(this double value); public static byte[] ToGSBinary(this IEnumerable<double> value); public static byte[] ToGSBinary(this string value); public static byte[] ToGSBinary(this IEnumerable<string> value); public static string GetHexDump(this IEnumerable<byte> value); } Program.cs Here's the the object that I'm converting to binary in a loop. class Program { static void Main(string[] args) { GSObject obj = new GSObject(); obj.AttachShort("smallInt", 15); obj.AttachInt("medInt", 120700); obj.AttachLong("bigInt", 10900800700); obj.AttachDouble("doubleVal", Math.PI); obj.AttachStringArray("muppetNames", new string[] { "Kermit", "Fozzy", "Piggy", "Animal", "Gonzo" }); GSObject apple = new GSObject(); apple.AttachString("name", "Apple"); apple.AttachString("color", "red"); apple.AttachBool("inStock", true); apple.AttachFloat("price", (float)1.5); GSObject lemon = new GSObject(); apple.AttachString("name", "Lemon"); apple.AttachString("color", "yellow"); apple.AttachBool("inStock", false); apple.AttachFloat("price", (float)0.8); GSObject apricoat = new GSObject(); apple.AttachString("name", "Apricoat"); apple.AttachString("color", "orange"); apple.AttachBool("inStock", true); apple.AttachFloat("price", (float)1.9); GSObject kiwi = new GSObject(); apple.AttachString("name", "Kiwi"); apple.AttachString("color", "green"); apple.AttachBool("inStock", true); apple.AttachFloat("price", (float)2.3); GSArray fruits = new GSArray(); fruits.AddGSObject(apple); fruits.AddGSObject(lemon); fruits.AddGSObject(apricoat); fruits.AddGSObject(kiwi); obj.AttachGSArray("fruits", fruits); Stopwatch w1 = Stopwatch.StartNew(); for (int i = 0; i < 50000; i++) { byte[] b = obj.ToGSBinary(); } w1.Stop(); Console.WriteLine(BitConverter.IsLittleEndian ? "Little Endian" : "Big Endian"); Console.WriteLine(w1.ElapsedMilliseconds + "ms"); } Here's the code for some of my other classes that are used in the code above. Most of it is repetitive. GSObject GSArray GSWrappedObject

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  • Swing code in sockets

    - by asb
    I am learning swings for making GUI. I was thinking which is the best possible way in case of socket with swings. 1. The whole swing code goes in the server file. All the handlers and logic in on server side. Client only create socket. 2. The server have logic part. The code for the swing to display interface goes on client side. Client Creates stream to send / rec. data from server. Whch is the good way out of 2 ?

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  • JNDI classes needed!!

    - by artaxerxe
    I have instaled in my computer a JDK version 1.6. (I'm learning about JNDI) When i run this: Hashtable env = new Hashtable(); env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.fscontext.RefFSContextFactory"); try { // Create the initial context Context ctx = new InitialContext(env); //... i get an error : Caused by: java.lang.ClassNotFoundException: com.sun.jndi.fscontext.RefFSContextFactory Caused by: java.lang.ClassNotFoundException: com.sun.jndi.fscontext.RefFSContextFactory Does it means that i need some classes to include in my classpath? I read in the tutorial that versions of jdk recently than v 3 doesn't need to download other classes. Thank advance!

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  • Create My own language with "Functional Programming Language"

    - by esehara
    I prefer Haskell. I already know How to create my own language with Procedural Language (for example: C, Java, Python, etc). But, I know How to create my own language with Functional Language (for example Haskell, Clojure and Scala). I've already read: Internet Resources Write Yourself a Scheme in 48 Hours Real World Haskell - Chapter 16.Using Persec Writing A Lisp Interpreter In Haskell Parsec, a fast combinator parser Implementing functional languages: a tutorial Books Introduction Functional Programming Using Haskell 2nd Edition -- Haskell StackOverflow (but with procedural language) Learning to write a compiler create my own programming language Source Libraries and tools/HJS -- Haskell Are there any other good sources? I wants to get more links,or sources.

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  • How invoke live method with arguments

    - by dorelal
    I am learning how to write jQuery plugin. So why I am doing what I am doing does not matter. I writing a plugin called live2 which does nothing else but internally calls live method. (function($) { $.fn.live2 = function() { /* if there are no elements then just return */ if (!this.length) return this; return this.each(function() { var $this = $(this); jQuery.fn.live.apply(this, arguments); }); // end of return this.each(function()) }; // end of plugin })(jQuery); Above code should be invoked just live any live method. Instead of live use live2. $('#container').live2('click',function(){ return false; }) But the plugin is not working. Any idea what the fix should be.

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  • Python Pari Library?

    - by silinter
    Pari/GP is an excellent library for functions relating to number theory. The problem is that there doesn't seem to be an up to date wrapper for python anywhere around, (pari-python uses an old version of pari) and I'm wondering if anyone knows of some other library/wrapper that is similar to pari or one that uses pari. I'm aware of SAGE, but it's far too large for my needs. GMPY is excellent as well, but there are some intrinsic pari functions that I miss, and I'd much rather use python than the provided GP environment. NZMATH, mpmath, scipy and sympy were all taken into consideration as well. On a related note, does anyone have any suggestions on loading the pari dll itself and using the functions contained in it? I've tried to very little success, other than loading it and learning about function pointers.

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  • Python Bitstream implementations

    - by Danielb
    I am writing a huffman implementation in Python as a learning exercise. I have got to the point of writing out my variable length huffman codes to a buffer (or file). Only to find there does not seem to be a bitstream class implemented by Python! I have had a look at the array and struct modules but they do not seem to do what I need without extra work. A bit of goggling turned up this bitstream implementation, which is more like what I am wanting. Is there really no comparable bitstream class in the Python standard library?

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  • Kohana 3 simple relations..

    - by matiit
    I'm trying to write a very simple cms (for learning purposes) in kohana 3 web framework. I have my db schemas and i want to map it to ORM but i have problems with relations. Schemas:articles and categories One article has one category. One category might has many articles of course. I think it is has_one relationship in article table.(?) Now php code. I need to create application/classes/models/article.php first, yes? class Model_Article extends ORM { protected // and i am not sure what i suppose to write here }

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  • Naming convention for the primary key in a Table

    - by kwokwai
    Hi all, I am learning the Model relationship types in cakephp. I have built twotables and in one of the Table A, I got these fields in it: Table A {postID, topic, content} Table B {replyID, content, postID} And when I ran the web page, a bunch of error related to SQL popped up saying that cakephp couldn't find post_id. It is weird that I have already declared the $primaryKey to be using postID in the tableA.php under Models folder, but cakephp seemed want me to change the ID field to post_id instead of postID, because the error disappeared after I have changed the primaryKey to post_id. ANy ideas?

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  • I wanted to be a programmer

    - by Henrik P. Hessel
    Hello, let me ask your opinion. I'm 25 now, living in Germany. I started with QBASIC, did some Java in Highschool, and after School I created some Websites in PHP. Now, because my Company is Microsoft Gold Partner, I've to use Microsoft all the time. C#, MSSQL, ASPX and Sharepoint <- I really hate it! So, in my spare I concentrate to gain more knowledge (C++, Java, Silverlight or WPF), because it feels that I'm so far behind, in comparison for example to you guys, or other older employees in my company. Do think that my behaviour is useful? Should I focus my time to become i.e. a pure C# Programmer? I did C# even before I started to learn some C++. Should I learn what do with pointers, memcpy and stuff like that, even if managed code brings us so much benefits? Or is it a waste of time, better invested in learning the latest technologies? rAyt

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  • Foreign keys in MySQL?

    - by icco
    I have been slowly learning SQL the last few weeks. I've picked up all of the relational algebra and the basics of how relational databases work. What I'm trying to do now is learn how it's implemented. A stumbling block I've come across in this, is foreign keys in MySQL. I can't seem to find much about the other than that they exist in the InnoDB storage schema that MySQL has. What is a simple example of foreign keys implemented in MySQL? Here's part of a schema I wrote that doesn't seem to be working if you would rather point out my flaw than show me a working example. CREATE TABLE `posts` ( `pID` bigint(20) NOT NULL auto_increment, `content` text NOT NULL, `time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP, `uID` bigint(20) NOT NULL, `wikiptr` bigint(20) default NULL, `cID` bigint(20) NOT NULL, PRIMARY KEY (`pID`), Foreign Key(`cID`) references categories, Foreign Key(`uID`) references users ) ENGINE=InnoDB;

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  • New to Rails. Doubt in Big URL Routing

    - by Gautam
    Hi, I have just started learning ruby on rails. I have a doubt wrt routing. Default Routing in Rails is :controller/:action/:id It works really fine for the example lets say example.com/publisher/author/book_name Could you tell me how do you work with something very big like this site http://www.telegraph.co.uk/sport/football/leagues/premierleague/chelsea/ Could you let me understand about the various controllers, actions, ids for the above mentioned url and how to code controller, models so as to achieve this. Could you suggest me some good tutorials when dealing with this big urls. Looking forward for your help Thanks in advance Gautam

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  • Graph Databases' Implementation

    - by user1478153
    I am having trouble visualizing a Graph Database. Visualizing an RDBMS is really very simple and I was able to understand from the first tutorial itself when I started learning it some 4-5 years ago. But I am not able to understand Graph Databases. I am also unable to get any good links on this topic, hence posting this question here. Specifically, I am looking for the following: Some really simple book/link on Graph Dbs Atleast some knowledge on the implementation details of a Graph DB (I hope all Graph DBs would be having atleast a few basic things in common). Thanks a lot in advance guys,

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  • Writing a Compiler for .net - IL or Bytecode?

    - by Michael Stum
    I'm currently diving into the inner workings of .net, which means IL. As an exercise, I want to build a brainf..k compiler for .net (yes, they already exist, but as said it's for learning purposes). For the moment I'm just writing some text files that contain .il and compile them with ilasm, which works. But I wonder if I could/should go one level deeper and write bytecode directly? My "concern" is the Windows PE Stuff when compiling an EXE - instead of ilasm I would need some sort of Bytecode linker that would take my MSIL/CIL bytecode and generate the PE Stuff for it? Or do compilers "only" compile their language to IL and execute ilasm? Is there a managed version of it that I can call/embed from my compiler?

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  • Why can't I set the Image Source in WPF app?

    - by elmonty
    I'm just learning WPF. I'm using VS 2008. I've added an Image control to my XAML, and I added a GIF file to the project. If I use the XAML Designer's property panel to set the image's Source property, the drop-down list for the Source property contains the following: C:\Sample Project;component/pinHorizontal.gif There are several problems with this: My project, named "Sample Project," is not in the root of my drive. Why is ";component" in there? If I select this value as given, I get the error "Property value is not valid" (yeah, no kidding). If I go into the XAML source and set the Source property manually, like so: The XAML Designer gives me this error: "The file pinHorizontal.gif is not part of the project or its 'Build Action' property is not set to 'Resource'." Why is this task so difficult? How do I assign an image source?

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  • concurrency in Java

    - by p1
    1]What is Non-blocking Concurrency and how is it different. 2] I have heard that this is available in Java. Are there any particular scenarios we should use this feature 3] Is there a difference/advantage of using one of these methods for a collection. What are the trade offs class List { private final ArrayList<String> list = new ArrayList<String>(); void add(String newValue) { synchronized (list) { list.add(newValue); } } } OR private final ArrayList<String> list = Collections.synchronizedMap(); The questions are more from a learning/understanding point of view. Thanks for attention.

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  • How to prevent Windows XP from stealing my input Ctrl-Space which is meant for Emacs

    - by Dean
    I am learning and using Emacs. What I found annoying is that Ctrl-Space input will be stolen by Windows XP to switch the language bar instead of setting the mark in Emacs. The "language bar" is the native input languages selection such as Chinese keyboard other than English keyboard. Is there a way to temporarily prevent XP from stealing it? I have disabled the language bar from "Regional and language options" from Control Panel but the problem still exists. It doesn't happen on my Windows 2000 desktop at office but it happens on my work Windows XP laptop. Thank you very much.

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  • How do I specify the block object / predicate required by NSDictionary's keysOfEntriesPassingTest ?

    - by Todd
    For learning (not practical -- yet) purposes, I'd like to use the following method on an NSDictionary to give me back a set of keys that have values using a test I've defined. Unfortunately have no idea how to specify the predicate. NSDictionary keysOfEntriesPassingTest: - (NSSet *)keysOfEntriesPassingTest:(BOOL (^)(id key, id obj, BOOL *stop))predicate Let's say for example all my values are NSURLs, and I'd like to get back all the URLs that are on port 8080. Here's my stab at coding that -- though it doesn't really make sense to me that it'd be correct: NSSet * mySet = [myDict keysOfEntriesPassingTest:^(id key, id obj, BOOL *stop) { if( [[obj port] isEqual: [NSNumber numberWithInt: 8080]]) { return key; }] And that's because I get back the following compiler error: incompatible block pointer types initializing 'void (^)(struct objc_object *, struct objc_object *, BOOL *)', expected 'BOOL (^)(struct objc_object *, struct objc_object *, BOOL *)' What am I missing? I'd appreciate a pointer at some docs that go into more detail about the "Block object" that the predicate is supposed to be. Thanks!

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  • (iPhone SDK) How to link instance variables to a specific UILabel

    - by Timbo
    I'm using the iPhone SDK to build a simple application. I've created a brand new class which has a single variable. I need to make 5 instances of that class, which I have no trouble doing. I can create those instances and also set the variables without issue. What i do need to know is this: How do I link each of the 5 different instances of the variable to different and specific UILabels? Would I be better to create a method that dynamically creates and positions the labels? Thanks for your help in advance, I'm now to this iphone programming thing. I'm serious about learning fast though so I have posted a bounty on this question here : http://www.askearn.com/Responses.aspx?QuestionID=6542613f-7be8-4bb3-a950-aac218d47711

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  • Kohana or CodeIgniter?

    - by Thinker
    I'm looking for a PHP framework. I did a research here and found CodeIgniter would be best for me. But then I discovered that there is Kohana based on CodeIgniter. And I'm annoyed, because since Kohana is based on CodeIgniter, it should work similar, but it is optimized for PHP 5, so it should be faster in a PHP 5 environment. I was going to choose Kohana and then I found benchmarks that points CodeIgniter as the faster one. I don't understand it. If Kohana is updated more frequently and optimized for PHP 5, shouldn't it be better then? I'm experienced PHP programmer, but Smarty is the only framework I know, and I don't want to waste next few month for learning a bad framework. Thanks for your reply, I will give Kohana a try.

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  • Qt Graphics Scene mouse event propagation

    - by Olorin
    hello i'm learning qt and i'm doing the folowing to add some widgets to a graphics scene void MainWindow::addWidgets(QList<QWidget *> &list, int code) { if(code == CODE_INFO) { QWidget *layoutWidget = new QWidget(); QVBoxLayout *layout = new QVBoxLayout(); foreach(QWidget *w, list) { layout->addWidget(w); this->connect(((ProductInfo*)w), SIGNAL(productClicked()), this, SLOT(getProductDetails())); } layoutWidget->setLayout(layout); this->scene->addWidget(layoutWidget); } } my ProductInfo class processes mouse release and emits a signal void ProductInfo::mouseReleaseEvent(QMouseEvent *e) { QWidget::mouseReleaseEvent(e); emit productClicked(); } the problem is after adding the widgets to the scene they no longer get the mouse release event and don't emit productClicked signal but if i add them to the main window(not to the scene) they work as expected. What am i doing wrong?

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  • Groovy 1.7 changes "final"?

    - by Aaron L. Carlow
    Just started learning Groovy, got the PragProg book "Programming Groovy" and had a problem compiling one of the sample scripts: class GCar2 { final miles = 0 def getMiles() { println "getMiles called" miles } def drive(dist) { if (dist > 0) { miles += dist } } } def car = new GCar2() println "Miles: $car.miles" println 'Driving' car.drive(10) println "Miles: $car.miles" try { print 'Can I see the miles? ' car.miles = 12 } catch (groovy.lang.ReadOnlyPropertyException ex) { println ex.message GroovyCar2.groovy: 20: cannnot access final field or property outside of constructor. @ line 20, column 35. def drive(dist) { if (dist > 0) miles += dist } ^ Groovy versions prior to 1.7 do not give an error. I looked through whatever documentation I could find and did not see the issue discussed. What is going on here? Aaron

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