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  • Rails' page caching vs. HTTP reverse proxy caches

    - by John Topley
    I've been catching up with the Scaling Rails screencasts. In episode 11 which covers advanced HTTP caching (using reverse proxy caches such as Varnish and Squid etc.), they recommend only considering using a reverse proxy cache once you've already exhausted the possibilities of page, action and fragment caching within your Rails application (as well as memcached etc. but that's not relevant to this question). What I can't quite understand is how using an HTTP reverse proxy cache can provide a performance boost for an application that already uses page caching. To simplify matters, let's assume that I'm talking about a single host here. This is my understanding of how both techniques work (maybe I'm wrong): With page caching the Rails process is hit initially and then generates a static HTML file that is served directly by the Web server for subsequent requests, for as long as the cache for that request is valid. If the cache has expired then Rails is hit again and the static file is regenerated with the updated content ready for the next request With an HTTP reverse proxy cache the Rails process is hit when the proxy needs to determine whether the content is stale or not. This is done using various HTTP headers such as ETag, Last-Modified etc. If the content is fresh then Rails responds to the proxy with an HTTP 304 Not Modified and the proxy serves its cached content to the browser, or even better, responds with its own HTTP 304. If the content is stale then Rails serves the updated content to the proxy which caches it and then serves it to the browser If my understanding is correct, then doesn't page caching result in less hits to the Rails process? There isn't all that back and forth to determine if the content is stale, meaning better performance than reverse proxy caching. Why might you use both techniques in conjunction?

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  • Threading Practice with Polling.

    - by Stacey
    I have a C# application that has to constantly read from a program; sometimes there is a chance it will not find what it needs, which will throw an exception. This is a limitation of the program it has to read from. This frequently causes the program to lock up as it tries to poll. So I solved it by spawning the 'polling' off into a separate thread. However watching the debugger, the thread is created and destroyed each time. I am uncertain if this is typical or not; but my question is, is this good practice, or am I using the threading for the wrong purpose? ProgramReader { static Thread oThread; public static void Read( Program program ) { // check to see if the program exists if ( false ) oThread = new ThreadStart(program.Poll); if(oThread != null || !oThread.IsAlive ) oThread.Start(); } } This is my general pseudocode. It runs every 10 seconds or so. Is this a huge hit to performance? The operation it performs is relatively small and lightweight; just repetitive.

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  • Create class instance in assembly from string name

    - by Arcadian
    I'm not sure if this is possible, and I'm quite new to using assemblies in C#.NET. What I would like to do is to create an instance of a class when supplied the string name of that class. Something like this: using MyAssembly; namespace MyNameSpace { Class MyClass { int MyValue1; int MyValue2; public MyClass(string myTypeName) { foreach(Type type in MyAssembly) { if((string)type == myTypeName) { //create a new instance of the type } } AssignInitialValues(//the type created above) } //Here I use an abstract type which the type above inherits from private void AssignInitialValues(AbstractType myClass) { this.value1 = myClass.value1; this.value2 = myClass.value2; } } } Obviously you cannot compare strings to types but it illustrates what I'm trying to do: create a type from a supplied string. Any thoughts? EDIT: After attempting: var myObject = (AbstractType) Activator.CreateInstance(null, myTypeName); AssignInitialValues(myObject); I get a number of errors: Inconsistent accessibility: parameter type 'MyAssembly.AbstractType' is less accessible than method 'MyNameSpace.MyClass.AssignInitialValues(MyAssembly.AstractType)' 'MyAssembly.AstractType' is inaccessible due to it's protection level The type or namespace name 'MyAssembly' could not be found (are you missing a using directive or an assembly reference?) The type or namespace name 'AbstractType' could not be found (are you missing a using directive or an assembly reference?) Not exactly sure why it can't find the assembly; I've added a reference to the assembly and I use a Using Directive for the namespace in the assembly. As for the protection level, it's calling classes (or rather the constructors of classes) which can only be public. Any clues on where the problem is? UPDATE: After looking through several articles on SO I came across this: http://stackoverflow.com/a/1632609/360627 Making the AbstractTypeclass public solved the issue of inconsistent accessibility. The new compiler error is this: Cannot convert type 'System.Runtime.Remoting.ObjectHandle' to 'MyAssembly.AbstractType' The line it references is this one: var myObject = (AbstractType) Activator.CreateInstance(null, myTypeName); Using .Unwrap() get's me past this error and I think it's the right way to do it (uncertain). However, when running the program I then get a TypeLoadException when this code is called. TypeLoadException: Could not load type ‘AbstractType’ from assembly ‘MyNameSpace'... Right away I can spot that the type its looking for is correct but the assembly it's looking in is wrong. Looking up the Activator.CreateInstance(String, String) method revealed that the null as the first argument means that the method will look in the executing assembly. This is contrary to the required behavior as in the original post. I've tried using MyAssembly as the first argument but this produces the error: 'MyAssembly' is a 'namespace' but is used like a 'variable' Any thoughts on how to fix this?

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  • Bad method names and what it says about code structure.

    - by maxfridbe
    (Apologies in advance if this is a re-post but I didn't find similar posts) What bad method name patterns have you seen in code and what did it tell you about the code. For instance, I keep seeing: public void preform___X___IfNecessary(...); I believe that this is bad because the operation X has an inversion of conditions. Note that this is a public method because classes methods might legitimately require private helpers like this

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  • Security in Iphone?

    - by adusum
    Is There any concept of HTTPS in Iphone.how iphone apps are safe? if we are developing any apps related to some security?how can we provide security to iphone apps. I know that NSURL,NSURLConnection classes contains in Build HTTP but is there any concept of HTTPS? Thanks,

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  • How to inherit constructors with arguments in .NET?

    - by Soumya92
    I have a "MustInherit" .NET class which declares a constructor with an integer parameter. However, Visual Studio gives me an error when I create any derived class stating that there is no constructor that can be called without any arguments. Is it possible to inherit the constructor with arguments? Right now, I have to use Public Sub New(ByVal A As Integer) MyBase.New(A) End Sub in the derived classes. Is there any way to avoid this?

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  • deleted gen folder, eclipse isn't generating it now :(

    - by LuxuryMode
    I accidentally deleted my gen folder and now, predictably, my resources are all messed up. I just created a gen folder myself and tried to project clean - that didn't work. Tried right-clicking project and going to android tools fix project properties - didn't work. Tried unchecking build automatically...didn't work. cleaned, closed project, closed eclipse, restarted, etc, etc. Nothing is working and I keep seeing this error: gen already exists but is not a source folder. Convert to a source folder or rename it. EDIT - OK was able to generate R.java, but now I'm getting crazy stuff in the console: [2011-06-14 17:06:11 - fastapp] Conversion to Dalvik format failed with error 1 [2011-06-14 17:06:42 - fastapp] Dx trouble processing "java/awt/font/NumericShaper.class": Ill-advised or mistaken usage of a core class (java.* or javax.*) when not building a core library. This is often due to inadvertently including a core library file in your application's project, when using an IDE (such as Eclipse). If you are sure you're not intentionally defining a core class, then this is the most likely explanation of what's going on. However, you might actually be trying to define a class in a core namespace, the source of which you may have taken, for example, from a non-Android virtual machine project. This will most assuredly not work. At a minimum, it jeopardizes the compatibility of your app with future versions of the platform. It is also often of questionable legality. If you really intend to build a core library -- which is only appropriate as part of creating a full virtual machine distribution, as opposed to compiling an application -- then use the "--core-library" option to suppress this error message. If you go ahead and use "--core-library" but are in fact building an application, then be forewarned that your application will still fail to build or run, at some point. Please be prepared for angry customers who find, for example, that your application ceases to function once they upgrade their operating system. You will be to blame for this problem. If you are legitimately using some code that happens to be in a core package, then the easiest safe alternative you have is to repackage that code. That is, move the classes in question into your own package namespace. This means that they will never be in conflict with core system classes. JarJar is a tool that may help you in this endeavor. If you find that you cannot do this, then that is an indication that the path you are on will ultimately lead to pain, suffering, grief, and lamentation. [2011-06-14 17:06:42 - fastapp] Dx 1 error; aborting [2011-06-14 17:06:42 - fastapp] Conversion to Dalvik format failed with error 1 And eclipse can't resolve the import of my resources import com.me.fastapp.R;

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  • Performance of SHA-1 Checksum from Android 2.2 to 2.3 and Higher

    - by sbrichards
    In testing the performance of: package com.srichards.sha; import android.app.Activity; import android.os.Bundle; import android.widget.TextView; import java.io.IOException; import java.io.InputStream; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import java.util.zip.ZipEntry; import java.util.zip.ZipFile; import com.srichards.sha.R; public class SHAHashActivity extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); TextView tv = new TextView(this); String shaVal = this.getString(R.string.sha); long systimeBefore = System.currentTimeMillis(); String result = shaCheck(shaVal); long systimeResult = System.currentTimeMillis() - systimeBefore; tv.setText("\nRunTime: " + systimeResult + "\nHas been modified? | Hash Value: " + result); setContentView(tv); } public String shaCheck(String shaVal){ try{ String resultant = "null"; MessageDigest digest = MessageDigest.getInstance("SHA1"); ZipFile zf = null; try { zf = new ZipFile("/data/app/com.blah.android-1.apk"); // /data/app/com.blah.android-2.apk } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } ZipEntry ze = zf.getEntry("classes.dex"); InputStream file = zf.getInputStream(ze); byte[] dataBytes = new byte[32768]; //65536 32768 int nread = 0; while ((nread = file.read(dataBytes)) != -1) { digest.update(dataBytes, 0, nread); } byte [] rbytes = digest.digest(); StringBuffer sb = new StringBuffer(""); for (int i = 0; i< rbytes.length; i++) { sb.append(Integer.toString((rbytes[i] & 0xff) + 0x100, 16).substring(1)); } if (shaVal.equals(sb.toString())) { resultant = ("\nFalse : " + "\nFound:\n" + sb.toString() + "|" + "\nHave:\n" + shaVal); } else { resultant = ("\nTrue : " + "\nFound:\n" + sb.toString() + "|" + "\nHave:\n" + shaVal); } return resultant; } catch (IOException e) { e.printStackTrace(); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } return null; } } On a 2.2 Device I get average runtime of ~350ms, while on newer devices I get runtimes of 26-50ms which is substantially lower. I'm keeping in mind these devices are newer and have better hardware but am also wondering if the platform and the implementation affect performance much and if there is anything that could reduce runtimes on 2.2 devices. Note, the classes.dex of the .apk being accessed is roughly 4MB. Thanks!

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  • getting around circular references in Delphi

    - by Tom
    Is there a way of getting around circular unit references in Delphi? Maybe a newer version of delphi or some magic hack or something? My delphi project has 100 000+ lines of code mostly based on singleton classes. I need to refactor this, but that would mean several months of "circular reference" hell :)

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  • Using RhinoMocks, how do you mock or stub a concrete class without an empty constructor?

    - by Mark Rogers
    Mocking a concrete class with Rhino Mocks seems to work pretty easy when you have an empty constructor on a class: public class MyClass{ public MyClass() {} } But if I add a constructor that takes parameters and remove the one that doesn't take parameters: public class MyClass{ public MyClass(MyOtherClass instance) {} } I tend to get an exception: System.MissingMethodException : Can't find a constructor with matching arguments I've tried putting in nulls in my call to Mock or Stub, but it doesn't work. Can I create mocks or stubs of concrete classes with Rhino Mocks, or must I always supply (implicitly or explicitly) a parameter-less constructor?

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  • Do I really need bindParam?

    - by sandelius
    Hi there! I'm trying to do a little PDO CRUD to learn some PDO. I have a question about bindParam. Here's my update method right now: public static function update($conditions = array(), $data = array(), $table = '') { self::instance(); // Late static bindings (PHP 5.3) $table = ($table === '') ? self::table() : $table; // Check which data array we want to use $values = (empty($data)) ? self::$_fields : $data; $sql = "UPDATE $table SET "; foreach ($values as $f => $v) { $sql .= "$f = ?, "; } // let's build the conditions self::build_conditions($conditions); // fix our WHERE, AND, OR, LIKE conditions $extra = self::$condition_string; // querystring $sql = rtrim($sql, ', ') . $extra; // let's merge the arrays into on $v_val = array_values($values); $c_val = array_values($conditions); $array = array_merge($v_val, self::$condition_array); $stmt = self::$db->prepare($sql); return $stmt->execute($array); } in my "self::$condition_array" I get all the right values from the ?. SO the query looks like this: UPDATE table SET this = ?, another = ? WHERE title = ? AND time = ? as you can see I dont use bindParams instead I pass the right values in the right order ($array) directly into the execute($array) method. This works like a charm BUT is it safe not use use bindParam here? If not then how can I do it? Thanks from Sweden Tobias

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  • A monkey could do this better - Access to and availability of private member functions in C++

    - by David
    I am wandering the desert of my brain. I'm trying to write something like the following: class MyClass { // Peripherally Related Stuff public: void TakeAnAction(int oneThing, int anotherThing) { switch(oneThing){ case THING_A: TakeThisActionWith(anotherThing); break; //cases THINGS_NOT_A: }; private: void TakeThisActionWith(int thing) { string outcome = new string; outcome = LookUpOutcome(thing); // Do some stuff based on outcome return; } string LookUpOutcome(int key) { string oc = new string; oc = MyPrivateMap[key]; return oc; } map<int, string> MyPrivateMap; Then in the .cc file where I am actually using these things, while compiling the TakeAnAction section, it [CC, the solaris compiler] throws an an error: 'The function LookUpOutcome must have a prototype' and bombs out. In my header file, I have declared 'string LookUpOutcome(int key);' in the private section of the class. I have tried all sorts of variations. I tried to use 'this' for a little while, and it gave me 'Can only use this in non-static member function.' Sadly, I haven't declared anything static and these are all, putatively, member functions. I tried it [on TakeAnAction and LookUp] when I got the error, but I got something like, 'Can't access MyPrivateMap from LookUp'. MyPrivateMap could be made public and I could refer to it directly, I guess, but my sensibility says that is not the right way to go about this [that means that namespace scoped helper functions are out, I think]. I also guess I could just inline the lookup and subsequent other stuff, but my line-o-meter goes on tilt. I'm trying desperately not to kludge it.

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  • Is it possible to use ASP.NET Dynamic Data and SubSonic 3?

    - by James
    Is it possible to use ASP.NET Dynamic Data with SubSonic 3 in-place of Linq to SQL classes or the Entity Framework? MetaModel.RegisterContext() throws an exception if you use the context class that SubSonic generates. I thought I remembered coming across a SubSonic/Dynamic Data example back before SubSonic 3 was released but I can't find it now. Has anyone been able to get this to work?

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  • JTextArea - Highlight Text While Scrolling Up or Down

    - by Sujay
    I'm trying to work with a non-editable JTextArea added to a JScrollPane. I want a line to be highlighted when the user clicks on that specific line. I could implement this part using the following code: public static void initHighlightOption(final JTextArea textArea){ textArea.setFont(new Font("Courier New", Font.PLAIN, 12)); textArea.setEditable(false); final Action selectLine = getAction(textArea, DefaultEditorKit.selectLineAction); textArea.addMouseListener(new MouseAdapter() { @Override public void mouseClicked(MouseEvent e) { if (SwingUtilities.isLeftMouseButton(e) && e.getClickCount() == 1) { selectLine.actionPerformed(null); } }); textArea.setSelectionStart(0); textArea.setSelectionEnd(0); } public static Action getAction(JTextArea textArea, String name) { Action action = null; Action[] actions = textArea.getActions(); for (int i = 0; i < actions.length; i++) { if (name.equals(actions[i].getValue(Action.NAME).toString())) { action = actions[i]; break; } } return action; } What I want to add is that once a line is highlighted and user scrolls up/down using keyboard up/down key, i want the current line to be highlighted. Is this possible by adding a keyListener? I'm stuck on how highlight data while scrolling up. The text area contains data like this: Line1 Line2 Line3 Line4 Line5 (i.e. there might be new lines between two particular lines of data)

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  • Newb Question: passing objects in java?

    - by Adam Outler
    Hello, I am new at java. I am doing the following: Read from file, then put data into a variable. checkToken = lineToken.nextToken(); processlinetoken() } But then when I try to process it... public static void readFile(String fromFile) throws IOException { BufferedReader reader = new BufferedReader(new FileReader(fromFile)); String line = null; while ((line=reader.readLine()) != null ) { if (line.length() >= 2) { StringTokenizer lineToken = new StringTokenizer (line); checkToken = lineToken.nextToken(); processlinetoken() ...... But here's where I come into a problem. public static void processlinetoken() checkToken=lineToken.nextToken(); } it fails out. Exception in thread "main" java.lang.Error: Unresolved compilation problem: The method nextToken() is undefined for the type String at testread.getEngineLoad(testread.java:243) at testread.readFile(testread.java:149) at testread.main(testread.java:119) so how do I get this to work? It seems to pass the variable, but nothing after the . works.

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  • Can GPU capabilities impact virtual machine performance?

    - by Dave White
    While this many not seem like a programming question directly, it impacts my development activities and so it seems like it belongs here. It seems that more and more developers are turning to virtual environments for development activities on their computers, SharePoint development being a prime example. Also, as a trainer, I have virtual training environments for all of the classes that I teach. I recently purchased a new Dell E6510 to travel around with. It has the i7 620M (Dual core, HyperThreaded cpu running at 2.66GHz) and 8 GB of memory. Reading the spec sheet, it sounded like it would be a great laptop to carry around and run virtual machines on. Getting the laptop though, I've been pretty disappointed with the user experience of developing in a virtual machine. Giving the Virtual Machine 4 GB of memory, it was slow and I could type complete sentences and watch the VM "catchup". My company has training laptops that we provide for our classes. They are Dell Precision M6400 Intel Core 2 Duo P8700 running at 2.54Ghz with 8 GB of memory and the experience on this laptops is night and day compared to the E6510. They are crisp and you barely aware that you are running in a virtual environment. Since the E6510 should be faster in all categories than the M6400, I couldn't understand why the new laptop was slower, so I did a component by component comparison and the only place where the E6510 is less performant than the M6400 is the graphics department. The M6400 is running a nVidia FX 2700m GPU and the E6510 is running a nVidia 3100M GPU. Looking at benchmarks of the two GPUs suggest that the FX 2700M is twice as fast as the 3100M. http://www.notebookcheck.net/Mobile-Graphics-Cards-Benchmark-List.844.0.html 3100M = 111th (E6510) FX 2700m = 47th (Precision M6400) Radeon HD 5870 = 8th (Alienware) The host OS is Windows 7 64bit as is the guest OS, running in Virtual Box 3.1.8 with Guest Additions installed on the guest. The IDE being used in the virtual environment is VS 2010 Premium. So after that long setup, my question is: Is the GPU significantly impacting the virtual machine's performance or are there other factors that I'm not looking at that I can use to boost the vm's performance? Do we now have to consider GPU performance when purchasing laptops where we expect to use virtualized development environments? Thanks in advance. Cheers, Dave

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  • Why do I get this error when trying to set up a class variable

    - by Jennifer
    I'm new to PHP so maybe I am overlooking something here but the following: class someClass { var $id = $_GET['id']; function sayHello() { echo "Hello"; } } gives the following error: Parse error: syntax error, unexpected T_VARIABLE in C:\xampp\htdocs\files\classes.php on line 13 If instead of $_GET['id'] I set the variable $id to a string, everything is fine though.

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  • Getting input and output from a jar file run from java class?

    - by Jack L.
    Hi, I have a jar file that runs this code: public class InputOutput { /** * @param args * @throws IOException */ public static void main(String[] args) throws IOException { boolean cont = true; BufferedReader in = new BufferedReader(new InputStreamReader(System.in)); while (cont) { System.out.print("Input something: "); String temp = in.readLine(); if (temp.equals("end")) { cont = false; System.out.println("Terminated."); } else System.out.println(temp); } } } I want to program another java class that executes this jar file and can get the input and send output to it. Is it possible? The current code I have is this but it is not working: public class JarTest { /** * Test input and output of jar files * @author Jack */ public static void main(String[] args) { try { Process io = Runtime.getRuntime().exec("java -jar InputOutput.jar"); BufferedReader in = new BufferedReader(new InputStreamReader(io.getInputStream())); OutputStreamWriter out = new OutputStreamWriter(io.getOutputStream()); boolean cont = true; BufferedReader consolein = new BufferedReader(new InputStreamReader(System.in)); while (cont) { String temp = consolein.readLine(); out.write(temp); System.out.println(in.readLine()); } } catch (IOException e) { e.printStackTrace(); } } } Thanks for your help

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  • Should ActionResult perform other tasks too

    - by Ori
    In Asp.net MVC one is encouraged to derive custom ActionResults, however should these classes handle other tasks unrelated to views, perhaps a EmailActionResult would render a view then send an email. What is best practice for the class ActionResult, is it only view specific? I want to keep things DRY too. Should the sending of the email be factored into a service class? perhaps using a filter would work. what are your thoughts?

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  • How to Serialize to XML containing attributes in .NET?

    - by user292815
    I have that code: ... request data = new request(); data.username = formNick; xml = data.Serialize(); ... [System.Serializable] public class request { public string username; public string password; static XmlSerializer serializer = new XmlSerializer(typeof(request)); public string Serialize() { StringBuilder builder = new StringBuilder(); XmlWriterSettings settings = new XmlWriterSettings(); settings.OmitXmlDeclaration = true; settings.Encoding = Encoding.UTF8; serializer.Serialize( System.Xml.XmlWriter.Create(builder, settings ), this); return builder.ToString(); } public static request Deserialize(string serializedData) { return serializer.Deserialize(new StringReader(serializedData)) as request; } } I want to add attributes to some nodes and create some sub-nodes. Also how to parse xml like that: <answer> <player id="2"> <coordinate axis="x"></coordinate> <coordinate axis="y"></coordinate> <coordinate axis="z"></coordinate> <action name="nothing"></action> </player> <player id="3"> <coordinate axis="x"></coordinate> <coordinate axis="y"></coordinate> <coordinate axis="z"></coordinate> <action name="boom"> <1>1</1> <2>2</2> </action> </player> </answer> p.s. it is not a xml file, it's answer from http server.

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  • InternalsVisibleTo attribute ain't workin'!

    - by skb
    I am trying to use the InternalsVisibleTo assembly attribute to make my internal classes in a .NET class library visible to my unit test project. For some reason, I keep getting an error message that says: 'MyClassName' is inaccessible due to its protection level Both assemblies are signed and I have the correct key listed in the attribute declaration. Any ideas?

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  • Are you a self taught programmer or did you take a programming course?

    - by workinprogress
    Lots of developers I know were self taught programmers including me. I was wondering how much of the developer community learned programming by taking a course in school or by experimenting, asking questions on forums, reading online articles, and just making it up as you go along? Post whether you were self taught or took classes, what language you program in, and anything else that may be interesting. P.S. Books count as self taught.

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