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• Cannot find Symbol = new

  - by Nick G.

  Java is complaining! cannot find symbol symbol : constructor Bar() location: class Bar JPanel panel = new Bar(); ^ QUESTION: Why am I getting this error?...everything seems to be correct. this is the coding: public class JFrameWithPanel { public static void main(String[] args) { JPanel panel = new Bar(); } } Bar( ) is public class Bar extends JPanel { public Bar(final JFrame frame) { super(new BorderLayout()); String[] tests = { "A+ Certification", "Network+ Certification", "Security+ Certification", "CIT Full Test Package" }; JComboBox comboBox = new JComboBox(tests); TextArea text = new TextArea(5, 10); add(new JLabel("Welcome to the CIT Test Program ")); add(new JLabel("Please select which Test Package from the list below.")); JMenuBar menuBar = new JMenuBar(); JMenu fileMenu = new JMenu("File"); JMenu editMenu = new JMenu("Edit"); JMenu helpMenu = new JMenu("Help"); menuBar.add(fileMenu); menuBar.add(editMenu); menuBar.add(helpMenu); JMenuItem newMenu = new JMenuItem("New (Ctrl+N)"); JMenuItem openMenu = new JMenuItem("Open (Ctrl+O)"); JMenuItem saveMenu = new JMenuItem("Save (Ctrl+S)"); JMenuItem exitMenu = new JMenuItem("Exit (Ctrl+W)"); JMenuItem cutMenu = new JMenuItem("Cut (Ctrl+X)"); JMenuItem copyMenu = new JMenuItem("Copy (Ctrl+C)"); JMenuItem pasteMenu = new JMenuItem("Paste (Ctrl+V)"); JMenuItem infoMenu = new JMenuItem("Help (Ctrl+H)"); fileMenu.add(newMenu); fileMenu.add(openMenu); fileMenu.add(saveMenu); fileMenu.add(exitMenu); editMenu.add(cutMenu); editMenu.add(copyMenu); editMenu.add(pasteMenu); helpMenu.add(infoMenu); this.add(comboBox, BorderLayout.NORTH); this.add(text, BorderLayout.SOUTH); frame.setJMenuBar(menuBar); add(new JButton("Select") { { addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { frame.dispose(); JOptionPane.showMessageDialog(frame, "IT WORKS!"); } }); } }); } }

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• Passing Data of WebView to Another Activity

  - by meygraph

  I've designed a training program and Html texts and image put into training. I want to address my html file by an activity to sent another activity. This is MainActivity /* * ListView item click listener. So we'll have the do stuff on click of * our ListItem */ listViewArticles.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> parent, View view, int position, long id) { switch (position) { case 0: Intent newActivity0 = new Intent(TrickPage.this,a_Dotted_Lines.class); startActivity(newActivity0); break; case 1: Intent newActivity1 = new Intent(TrickPage.this,TutorialsPage.class); startActivity(newActivity1); break; case 2: Intent newActivity2 = new Intent(TrickPage.this,TutorialsPage.class); startActivity(newActivity2); break; case 3: Intent newActivity3 = new Intent(TrickPage.this,TutorialsPage.class); startActivity(newActivity3); break; default: // Nothing do! } and this SecondActivity (show WebView) public class a_Dotted_Lines extends Activity { private WebView webView; @SuppressLint("SetJavaScriptEnabled") @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.a_dotted_lines); // Button HOME ImageButton ImageButton_home = (ImageButton) findViewById(R.id.ImageButton_home); ImageButton_home.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent intent = new Intent(); intent.setClass(a_Dotted_Lines.this, Main.class); startActivity(intent); overridePendingTransition(R.anim.fadein, R.anim.fadeout); } }); //Button Previous ImageButton ImageButton_previus = (ImageButton) findViewById(R.id.ImageButton_previus); ImageButton_previus.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //Closing SecondScreen Activity finish(); } }); webView = (WebView) findViewById(R.id.webview_compontent); webView.getSettings().setJavaScriptEnabled(true); webView.loadUrl("file:///android_asset/html/article.htm"); } } I want Send "file:///android_asset/html/article.htm" or other addres from MainActivity Is it possible? Sorry My English is not good

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• Problem with tcp server when converting to service

  - by djerry

  Hello lads, I'm working on monitoring some object (cdr-packets). I'm setting up a tcp-server and am listening on port 50043 for the packages. The program as a console application is working just fine, my server is working like it should and i'm receiving the packets. When i try to use it as a service, i cannot seem to get a client connected to my server. Is there something i need to change to deploy this as a service? Code below is from my application: this is my service class where i start protected override void OnStart(string[] args) { server = new TcpServer(); server.StartServer(); } this is the constructor of TcpServer public TcpServer() { try { _server = new TcpListener(IPAddress.Any, 50043); } catch (Exception) { _server = null; } } this is the method i call after initialising the class public void StartServer() { if (_server != null) { // Create a ArrayList for storing SocketListeners before starting the server. _socketListenersList = new ArrayList(); // Start the Server and start the thread to listen client requests. _server.Start(); _serverThread = new Thread(new ThreadStart(ServerThreadStart)); _serverThread.Start(); // Create a low priority thread that checks and deletes client // SocktConnection objcts that are marked for deletion. _purgingThread = new Thread(new ThreadStart(PurgingThreadStart)); _purgingThread.Priority = ThreadPriority.Lowest; _purgingThread.Start(); } } this is the thread that keep checking if any client tries to connect private void ServerThreadStart() { // Client Socket variable; Socket clientSocket = null; TcpSocketListener socketListener = null; while (!_stopServer) { try { // Wait for any client requests and if there is any request from any //client accept it (Wait indefinitely). clientSocket = _server.AcceptSocket(); // Create a SocketListener object for the client. socketListener = new TcpSocketListener(clientSocket); // Add the socket listener to an array list in a thread safe fashon. lock (_socketListenersList) { _socketListenersList.Add(socketListener); } // Start a communicating with the client in a different thread. socketListener.StartSocketListener(); } catch (SocketException se) { _stopServer = true; } } } when for the first time a packet waits to be read, and i get to "clientSocket = _server.AcceptSocket();", it throws an exception (service, not very good debugable) Does anyone recognize this problem or can help me? Thanks in advance

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• Python/Biomolecular Physics- Trying to code a simple stochastic simulation of a system exhibiting co

  - by user359597

  *edited 6/17/10 I'm trying to understand how to improve my code (make it more pythonic). Also, I'm interested in writing more intuitive 'conditionals' that would describe scenarios that are commonplace in biochemistry. The conditional criteria in the below program is explained in Answer #2, but I am not satisfied with it- it is correct, but isn't obvious and isn't easy to implement for more complicated conditional scenarios. Ideas welcome. Comments/criticisms welcome. First posting experience @ stackoverflow- please comment on etiquette if needed. The code generates a list of values that are the solution to the following exercise: "In a programming language of your choice, implement Gillespie’s First Reaction Algorithm to study the temporal behaviour of the reaction A---B in which the transition from A to B can only take place if another compound, C, is present, and where C dynamically interconverts with D, as modelled in the Petri-net below. Assume that there are 100 molecules of A, 1 of C, and no B or D present at the start of the reaction. Set kAB to 0.1 s-1 and both kCD and kDC to 1.0 s-1. Simulate the behaviour of the system over 100 s." def sim(): # Set the rate constants for all transitions kAB = 0.1 kCD = 1.0 kDC = 1.0 # Set up the initial state A = 100 B = 0 C = 1 D = 0 # Set the start and end times t = 0.0 tEnd = 100.0 print "Time\t", "Transition\t", "A\t", "B\t", "C\t", "D" # Compute the first interval transition, interval = transitionData(A, B, C, D, kAB, kCD, kDC) # Loop until the end time is exceded or no transition can fire any more while t <= tEnd and transition >= 0: print t, '\t', transition, '\t', A, '\t', B, '\t', C, '\t', D t += interval if transition == 0: A -= 1 B += 1 if transition == 1: C -= 1 D += 1 if transition == 2: C += 1 D -= 1 transition, interval = transitionData(A, B, C, D, kAB, kCD, kDC) def transitionData(A, B, C, D, kAB, kCD, kDC): """ Returns nTransition, the number of the firing transition (0: A->B, 1: C->D, 2: D->C), and interval, the interval between the time of the previous transition and that of the current one. """ RAB = kAB * A * C RCD = kCD * C RDC = kDC * D dt = [-1.0, -1.0, -1.0] if RAB > 0.0: dt[0] = -math.log(1.0 - random.random())/RAB if RCD > 0.0: dt[1] = -math.log(1.0 - random.random())/RCD if RDC > 0.0: dt[2] = -math.log(1.0 - random.random())/RDC interval = 1e36 transition = -1 for n in range(len(dt)): if dt[n] > 0.0 and dt[n] < interval: interval = dt[n] transition = n return transition, interval if __name__ == '__main__': sim()

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• Reducer getting fewer records than expected

  - by sathishs

  We have a scenario of generating unique key for every single row in a file. we have a timestamp column but the are multiple rows available for a same timestamp in few scenarios. We decided unique values to be timestamp appended with their respective count as mentioned in the below program. Mapper will just emit the timestamp as key and the entire row as its value, and in reducer the key is generated. Problem is Map outputs about 236 rows, of which only 230 records are fed as an input for reducer which outputs the same 230 records. public class UniqueKeyGenerator extends Configured implements Tool { private static final String SEPERATOR = "\t"; private static final int TIME_INDEX = 10; private static final String COUNT_FORMAT_DIGITS = "%010d"; public static class Map extends Mapper<LongWritable, Text, Text, Text> { @Override protected void map(LongWritable key, Text row, Context context) throws IOException, InterruptedException { String input = row.toString(); String[] vals = input.split(SEPERATOR); if (vals != null && vals.length >= TIME_INDEX) { context.write(new Text(vals[TIME_INDEX - 1]), row); } } } public static class Reduce extends Reducer<Text, Text, NullWritable, Text> { @Override protected void reduce(Text eventTimeKey, Iterable<Text> timeGroupedRows, Context context) throws IOException, InterruptedException { int cnt = 1; final String eventTime = eventTimeKey.toString(); for (Text val : timeGroupedRows) { final String res = SEPERATOR.concat(getDate( Long.valueOf(eventTime)).concat( String.format(COUNT_FORMAT_DIGITS, cnt))); val.append(res.getBytes(), 0, res.length()); cnt++; context.write(NullWritable.get(), val); } } } public static String getDate(long time) { SimpleDateFormat utcSdf = new SimpleDateFormat("yyyyMMddhhmmss"); utcSdf.setTimeZone(TimeZone.getTimeZone("America/Los_Angeles")); return utcSdf.format(new Date(time)); } public int run(String[] args) throws Exception { conf(args); return 0; } public static void main(String[] args) throws Exception { conf(args); } private static void conf(String[] args) throws IOException, InterruptedException, ClassNotFoundException { Configuration conf = new Configuration(); Job job = new Job(conf, "uniquekeygen"); job.setJarByClass(UniqueKeyGenerator.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(Text.class); job.setMapperClass(Map.class); job.setReducerClass(Reduce.class); job.setInputFormatClass(TextInputFormat.class); job.setOutputFormatClass(TextOutputFormat.class); // job.setNumReduceTasks(400); FileInputFormat.addInputPath(job, new Path(args[0])); FileOutputFormat.setOutputPath(job, new Path(args[1])); job.waitForCompletion(true); } } It is consistent for higher no of lines and the difference is as huge as 208969 records for an input of 20855982 lines. what might be the reason for reduced inputs to reducer?

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• How to learn proper C++?

  - by Chris

  While reading a long series of really, really interesting threads, I've come to a realization: I don't think I really know C++. I know C, I know classes, I know inheritance, I know templates (& the STL) and I know exceptions. Not C++. To clarify, I've been writing "C++" for more than 5 years now. I know C, and I know that C and C++ share a common subset. What I've begun to realize, though, is that more times than not, I wind up treating C++ something vaguely like "C with classes," although I do practice RAII. I've never used Boost, and have only read up on TR1 and C++0x - I haven't used any of these features in practice. I don't use namespaces. I see a list of #defines, and I think - "Gracious, that's horrible! Very un-C++-like," only to go and mindlessly write class wrappers for the sake of it, and I wind up with large numbers (maybe a few per class) of static methods, and for some reason, that just doesn't seem right lately. The professional in me yells "just get the job done," the academic yells "you should write proper C++ when writing C++" and I feel like the point of balance is somewhere in between. I'd like to note that I don't want to program "pure" C++ just for the sake of it. I know several languages. I have a good feel for what "Pythonic" is. I know what clean and clear PHP is. Good C code I can read and write better than English. The issue is that I learned C by example, and picked up C++ as a "series of modifications" to C. And a lot of my early C++ work was creating class wrappers for C libraries. I feel like my own personal C-heavy background while learning C++ has sort of... clouded my acceptance of C++ in it's own right, as it's own language. Do the weathered C++ lags here have any advice for me? Good examples of clean, sharp C++ to learn from? What habits of C does my inner-C++ really need to break from? My goal here is not to go forth and trumpet "good" C++ paradigm from rooftops for the sake of it. C and C++ are two different languages, and I want to start treating them that way. How? Where to start? Thanks in advance! Cheers, -Chris

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• File Output using Gforth

  - by sheepez

  As a first project I have been writing a short program to render the Mandelbrot fractal. I have got to the point of trying to output my results to a file ( e.g. .bmp or .ppm ) and got stuck. I have not really found any examples of exactly what I am trying to do, but I have found two examples of code to copy from one file to another. The examples in the Gforth documentation ( Section 3.27 ) did not work for me ( winXP ) in fact they seemed to open and create files but not write to files properly. This is the Gforth documentation example that copies the contents of one file to another: 0 Value fd-in 0 Value fd-out : open-input ( addr u -- ) r/o open-file throw to fd-in ; : open-output ( addr u -- ) w/o create-file throw to fd-out ; s" foo.in" open-input s" foo.out" open-output : copy-file ( -- ) begin line-buffer max-line fd-in read-line throw while line-buffer swap fd-out write-line throw repeat ; I found this example ( http://rosettacode.org/wiki/File_IO#Forth ) which does work. The main problem is that I can't isolate the part that writes to a file and have it still work. The main confusion is that r doesn't seem to consume TOS as I might expect. : copy-file2 ( a1 n1 a2 n2 -- ) r/o open-file throw >r w/o create-file throw r> begin pad maxstring 2 pick read-file throw ?dup while pad swap 3 pick write-file throw repeat close-file throw close-file throw ; \ Invoke it like this: s" output.txt" s" input.txt" copy-file I would be very grateful if someone could explain exactly how the open, create read and write -file words actually work, as my investigation keeps resulting in somewhat bizarre stacks. Any clues as to why the Gforth examples do not work might help too. In summary, I want to output from Gforth to a file and so far have been thwarted. Can anyone offer any help? Thank you Vijay, I think that I understand the example that you gave. However when I try to use something like this ( which I think is similar ): 0 value test-file : write-test s" testfile.out" w/o create-file throw to test-file s" test text" test-file write-line ; I get ok but nothing is put into the file, have I made a mistake? It seems that the problem was due to not flushing the relevant buffers or explicitly closing the file. Adding something like test-file flush-file throw or test-file close-file throw between write-line and ; makes it work. Thanks again Vijay for helping.

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• Initialization of components with interdependencies - possible antipattern?

  - by Rosarch

  I'm writing a game that has many components. Many of these are dependent upon one another. When creating them, I often get into catch-22 situations like "WorldState's constructor requires a PathPlanner, but PathPlanner's constructor requires WorldState." Originally, this was less of a problem, because references to everything needed were kept around in GameEngine, and GameEngine was passed around to everything. But I didn't like the feel of that, because it felt like we were giving too much access to different components, making it harder to enforce boundaries. Here is the problematic code: /// <summary> /// Constructor to create a new instance of our game. /// </summary> public GameEngine() { graphics = new GraphicsDeviceManager(this); Components.Add(new GamerServicesComponent(this)); //Sets dimensions of the game window graphics.PreferredBackBufferWidth = 800; graphics.PreferredBackBufferHeight = 600; graphics.ApplyChanges(); IsMouseVisible = true; screenManager = new ScreenManager(this); //Adds ScreenManager as a component, making all of its calls done automatically Components.Add(screenManager); // Tell the program to load all files relative to the "Content" directory. Assets = new CachedContentLoader(this, "Content"); inputReader = new UserInputReader(Constants.DEFAULT_KEY_MAPPING); collisionRecorder = new CollisionRecorder(); WorldState = new WorldState(new ReadWriteXML(), Constants.CONFIG_URI, this, contactReporter); worldQueryUtils = new WorldQueryUtils(worldQuery, WorldState.PhysicsWorld); ContactReporter contactReporter = new ContactReporter(collisionRecorder, worldQuery, worldQueryUtils); gameObjectManager = new GameObjectManager(WorldState, assets, inputReader, pathPlanner); worldQuery = new DefaultWorldQueryEngine(collisionRecorder, gameObjectManager.Controllers); gameObjectManager.WorldQueryEngine = worldQuery; pathPlanner = new PathPlanner(this, worldQueryUtils, WorldQuery); gameObjectManager.PathPlanner = pathPlanner; combatEngine = new CombatEngine(worldQuery, new Random()); } Here is an excerpt of the above that's problematic: gameObjectManager = new GameObjectManager(WorldState, assets, inputReader, pathPlanner); worldQuery = new DefaultWorldQueryEngine(collisionRecorder, gameObjectManager.Controllers); gameObjectManager.WorldQueryEngine = worldQuery; I hope that no one ever forgets that setting of gameObjectManager.WorldQueryEngine, or else it will fail. Here is the problem: gameObjectManager needs a WorldQuery, and WorldQuery needs a property of gameObjectManager. What can I do about this? Have I found an anti-pattern?

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• Joda Time cannot subtract one hour

  - by Leoa

  In my android program, I have a spinner that allows the user to select different times. Each selection is processed with Joda time to subtract the minutes. It works fine for minutes 0 to 59 and 61 and greater. However, when 60 minutes is subtracted, the time is not updated, and the original time is shown. How do I get Joda time to subtract 60 minutes? Spinner: public class MyOnItemSelectedListener implements OnItemSelectedListener { public void onItemSelected(AdapterView<?> parent, View view, int pos, long id1) { String mins = parent.getItemAtPosition(pos).toString(); int intmins=0; // process user's selection of alert time if(mins.equals("5 minutes")){intmins = 5;} if(mins.equals("10 minutes")){intmins = 10;} if(mins.equals("20 minutes")){intmins = 20;} if(mins.equals("30 minutes")){intmins = 30;} if(mins.equals("40 minutes")){intmins = 40;} if(mins.equals("50 minutes")){intmins = 50;} if(mins.equals("60 minutes")){intmins = 60;} if(mins.equals("120 minutes")){intmins = 120;} String stringMinutes=""+intmins; setAlarm(intmins, stringMinutes); } else { } public void onNothingSelected(AdapterView parent) { mLocationDisplay.setText(" " + location); } } public void setAlarm(int intmins, String mins) { // based alarm time on start time of event. TODO get info from database. String currentDate; SimpleDateFormat myFormat = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss"); Date date1 = null; DateTime dt; currentDate = eventdate + " " + startTimeMilitary;// startTimeMilitary; try { date1 = myFormat.parse(currentDate); } catch (ParseException e) { // TODO Auto-generated catch block e.printStackTrace(); } dt = new DateTime(date1); long dateInMillis = dt.getMillis(); String sDateInMillis = Long.toString(dateInMillis); // subtract the selected time from the event's start time String newAlertTime = subtractTime(dt, intmins); newAlertTime = subtractTime(dt, intmins); //......}

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• Hide public method used to help test a .NET assembly

  - by ChrisW

  I have a .NET assembly, to be released. Its release build includes: A public, documented API of methods which people are supposed to use A public but undocumented API of other methods, which exist only in order to help test the assembly, and which people are not supposed to use The assembly to be released is a custom control, not an application. To regression-test it, I run it in a testing framework/application, which uses (in addition to the public/documented API) some advanced/undocumented methods which are exported from the control. For the public methods which I don't want people to use, I excluded them from the documentation using the <exclude> tag (supported by the Sandcastle Help File Builder), and the [EditorBrowsable] attribute, for example like this: /// <summary> /// Gets a <see cref="IEditorTransaction"/> instance, which helps /// to combine several DOM edits into a single transaction, which /// can be undone and redone as if they were a single, atomic operation. /// </summary> /// <returns>A <see cref="IEditorTransaction"/> instance.</returns> IEditorTransaction createEditorTransaction(); /// <exclude/> [EditorBrowsable(EditorBrowsableState.Never)] void debugDumpBlocks(TextWriter output); This successfully removes the method from the API documentation, and from Intellisense. However, if in a sample application program I right-click on an instance of the interface to see its definition in the metadata, I can still see the method, and the [EditorBrowsable] attribute as well, for example: // Summary: // Gets a ModelText.ModelDom.Nodes.IEditorTransaction instance, which helps // to combine several DOM edits into a single transaction, which can be undone // and redone as if they were a single, atomic operation. // // Returns: // A ModelText.ModelDom.Nodes.IEditorTransaction instance. IEditorTransaction createEditorTransaction(); // [EditorBrowsable(EditorBrowsableState.Never)] void debugDumpBlocks(TextWriter output); Questions: Is there a way to hide a public method, even from the meta data? If not then instead, for this scenario, would you recommend making the methods internal and using the InternalsVisibleTo attribute? Or would you recommend some other way, and if so what and why? Thank you.

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• Is this a valid pattern for raising events in C#?

  - by Will Vousden

  Update: For the benefit of anyone reading this, since .NET 4, the lock is unnecessary due to changes in synchronization of auto-generated events, so I just use this now: public static void Raise<T>(this EventHandler<T> handler, object sender, T e) where T : EventArgs { if (handler != null) { handlerCopy(sender, e); } } And to raise it: SomeEvent.Raise(this, new FooEventArgs()); Having been reading one of Jon Skeet's articles on multithreading, I've tried to encapsulate the approach he advocates to raising an event in an extension method like so (with a similar generic version): public static void Raise(this EventHandler handler, object @lock, object sender, EventArgs e) { EventHandler handlerCopy; lock (@lock) { handlerCopy = handler; } if (handlerCopy != null) { handlerCopy(sender, e); } } This can then be called like so: protected virtual void OnSomeEvent(EventArgs e) { this.someEvent.Raise(this.eventLock, this, e); } Are there any problems with doing this? Also, I'm a little confused about the necessity of the lock in the first place. As I understand it, the delegate is copied in the example in the article to avoid the possibility of it changing (and becoming null) between the null check and the delegate call. However, I was under the impression that access/assignment of this kind is atomic, so why is the lock necessary? Update: With regards to Mark Simpson's comment below, I threw together a test: static class Program { private static Action foo; private static Action bar; private static Action test; static void Main(string[] args) { foo = () => Console.WriteLine("Foo"); bar = () => Console.WriteLine("Bar"); test += foo; test += bar; test.Test(); Console.ReadKey(true); } public static void Test(this Action action) { action(); test -= foo; Console.WriteLine(); action(); } } This outputs: Foo Bar Foo Bar This illustrates that the delegate parameter to the method (action) does not mirror the argument that was passed into it (test), which is kind of expected, I guess. My question is will this affect the validity of the lock in the context of my Raise extension method? Update: Here is the code I'm now using. It's not quite as elegant as I'd have liked, but it seems to work: public static void Raise<T>(this object sender, ref EventHandler<T> handler, object eventLock, T e) where T : EventArgs { EventHandler<T> copy; lock (eventLock) { copy = handler; } if (copy != null) { copy(sender, e); } }

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• Multi-Threading Question Concerning WPF

  - by Andrew

  Hello, I'm a newbie to threading, and I don't really know how to code a particular task. I would like to handle a mouse click event on a window that will kick off a while loop in a seperate thread. This thread, which is distinct from the UI thread, should call a function in the while loop which updates a label on the window being serviced by the UI thread. The while loop should stop running when the left mouse button is no longer being pressed. All the loop does is increment a counter, and then repeatedly call the function which displays the updated value in the window. The code for the window and all of the threading is given below (I keep getting some error about STA threading, but don't know where to put the attribute). Also, I'm hoping to use this solution, if it ever works, in another project that makes asynchronous calls elsewhere to a service via wcf, so I was hoping not to make any application-wide special configurations, since I'm really new to multi-threading and am quite worried about breaking other code in a larger program... Here's what I have: <Window x:Class="WpfApplication2.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:WpfApplication2" Name="MyMainWindow" Title="MainWindow" Width="200" Height="150" PreviewMouseLeftButtonDown="MyMainWindow_PreviewMouseLeftButtonDown"> <Label Height="28" Name="CounterLbl" /> </Window> And here's the code-behind: using System.Windows; using System.Windows.Input; using System.Threading; namespace WpfApplication2 { /// <summary> /// Interaction logic for MainWindow.xaml /// </summary> public partial class MainWindow : Window { private int counter = 0; public MainWindow() { InitializeComponent(); } private delegate void EmptyDelegate(); private void MyMainWindow_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e) { Thread counterThread = new Thread(new ThreadStart(MyThread)); counterThread.Start(); } private void MyThread() { while (Mouse.LeftButton == MouseButtonState.Pressed) { counter++; Dispatcher.Invoke(new EmptyDelegate(UpdateLabelContents), null); } } private void UpdateLabelContents() { CounterLbl.Content = counter.ToString(); } } } Anyways, multi-threading is really new to me, and I don't have any experience implementing it, so any thoughts or suggestions are welcome! Thanks, Andrew

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• Gradual memory leak in loop over contents of QTMovie

  - by Benji XVI

  I have a simple foundation tool that exports every frame of a movie as a .tiff file. Here is the relevant code: NSString* movieLoc = [NSString stringWithCString:argv[1]]; QTMovie *sourceMovie = [QTMovie movieWithFile:movieLoc error:nil]; int i=0; while (QTTimeCompare([sourceMovie currentTime], [sourceMovie duration]) != NSOrderedSame) { // save image of movie to disk NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSString *filePath = [NSString stringWithFormat:@"/somelocation_%d.tiff", i++]; NSData *currentImageData = [[sourceMovie currentFrameImage] TIFFRepresentation]; [currentImageData writeToFile:filePath atomically:NO]; NSLog(@"%@", filePath); [sourceMovie stepForward]; [arp release]; } [pool drain]; return 0; As you can see, in order to prevent very large memory buildups with the various transparently-autoreleased variables in the loop, we create, and flush, an autoreleasepool with every run through the loop. However, over the course of stepping through a movie, the amount of memory used by the program still gradually increases. Instruments is not detecting any memory leaks per se, but the object trace shows certain General Data blocks to be increasing in size. [Edited out reference to slowdown as it doesn't seem to be as much of a problem as I thought.] Edit: let's knock out some parts of the code inside the loop & see what we find out... Test 1 while (banana) { NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSString *filePath = [NSString stringWithFormat:@"/somelocation_%d.tiff", i++]; NSLog(@"%@", filePath); [sourceMovie stepForward]; [arp release]; } Here we simply loop over the whole movie, creating the filename and logging it. Memory characteristics: remains at 15MB usage for the duration. Test 2 while (banana) { NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSImage *image = [sourceMovie currentFrameImage]; [sourceMovie stepForward]; [arp release]; } Here we add back in the creation of the NSImage from the current frame. Memory characteristics: gradually increasing memory usage. RSIZE is at 60MB by frame 200; 75MB by f300. Test 3 while (banana) { NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSImage *image = [sourceMovie currentFrameImage]; NSData *imageData = [image TIFFRepresentation]; [sourceMovie stepForward]; [arp release]; } We've added back in the creation of an NSData object from the NSImage. Memory characteristics: Memory usage is again increasing: 62MB at f200; 75MB at f300. In other words, largely identical. It looks like a memory leak in the underlying system QTMovie uses to do currentFrameImage, to me.

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• Implementing Skip List in C++

  - by trikker

  [SOLVED] So I decided to try and create a sorted doubly linked skip list... I'm pretty sure I have a good grasp of how it works. When you insert x the program searches the base list for the appropriate place to put x (since it is sorted), (conceptually) flips a coin, and if the "coin" lands on a then that element is added to the list above it(or a new list is created with element in it), linked to the element below it, and the coin is flipped again, etc. If the "coin" lands on b at anytime then the insertion is over. You must also have a -infinite stored in every list as the starting point so that it isn't possible to insert a value that is less than the starting point (meaning that it could never be found.) To search for x, you start at the "top-left" (highest list lowest value) and "move right" to the next element. If the value is less than x than you continue to the next element, etc. until you have "gone too far" and the value is greater than x. In this case you go back to the last element and move down a level, continuing this chain until you either find x or x is never found. To delete x you simply search x and delete it every time it comes up in the lists. For now, I'm simply going to make a skip list that stores numbers. I don't think there is anything in the STL that can assist me, so I will need to create a class List that holds an integer value and has member functions, search, delete, and insert. The problem I'm having is dealing with links. I'm pretty sure I could create a class to handle the "horizontal" links with a pointer to the previous element and the element in front, but I'm not sure how to deal with the "vertical" links (point to corresponding element in other list?) If any of my logic is flawed please tell me, but my main questions are: How to deal with vertical links and whether my link idea is correct Now that I read my class List idea I'm thinking that a List should hold a vector of integers rather than a single integer. In fact I'm pretty positive, but would just like some validation. I'm assuming the coin flip would simply call int function where rand()%2 returns a value of 0 or 1 and if it's 0 then a the value "levels up" and if it's 0 then the insert is over. Is this incorrect? How to store a value similar to -infinite? Edit: I've started writing some code and am considering how to handle the List constructor....I'm guessing that on its construction, the "-infinite" value should be stored in the vectorname[0] element and I can just call insert on it after its creation to put the x in the appropriate place.

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• How to obtain the first cluster of the directory's data in FAT using C# (or at least C++) and Win32A

  - by DarkWalker

  So I have a FAT drive, lets say H: and a directory 'work' (full path 'H:\work'). I need to get the NUMBER of the first cluster of that directory. The number of the first cluster is 2-bytes value, that is stored in the 26th and 27th bytes of the folder enty (wich is 32 bytes). Lets say I am doing it with file, NOT a directory. I can use code like this: static public string GetDirectoryPtr(string dir) { IntPtr ptr = CreateFile(@"H:\Work\dover.docx", GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, IntPtr.Zero, OPEN_EXISTING, 0,//FILE_FLAG_BACKUP_SEMANTICS, IntPtr.Zero); try { const uint bytesToRead = 2; byte[] readbuffer = new byte[bytesToRead]; if (ptr.ToInt32() == -1) return String.Format("Error: cannot open direcotory {0}", dir); if (SetFilePointer(ptr, 26, 0, 0) == -1) return String.Format("Error: unable to set file pointer on file {0}", ptr); uint read = 0; // real count of read bytes if (!ReadFile(ptr, readbuffer, bytesToRead, out read, 0)) return String.Format("cant read from file {0}. Error #{1}", ptr, Marshal.GetLastWin32Error()); int result = readbuffer[0] + 16 * 16 * readbuffer[1]; return result.ToString();//ASCIIEncoding.ASCII.GetString(readbuffer); } finally { CloseHandle(ptr); } } And it will return some number, like 19 (quite real to me, this is the only file on the disk). But I DONT need a file, I need a folder. So I am puttin FILE_FLAG_BACKUP_SEMANTICS param for CreateFile call... and dont know what to do next =) msdn is very clear on this issue http://msdn.microsoft.com/en-us/library/aa365258(v=VS.85).aspx It sounds to me like: "There is no way you can get a number of the folder's first cluster". The most desperate thing is that my tutor said smth like "You are going to obtain this or you wont pass this course". The true reason why he is so sure this is possible is because for 10 years (or may be more) he recieved the folder's first cluster number as a HASH of the folder's addres (and I was stupid enough to point this to him, so now I cant do it the same way) PS: This is the most spupid task I have ever had!!! This value is not really used anythere in program, it is only fcking pointless integer.

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• Implementing events to communicate between two processes - C

  - by Jamie Keeling

  Hello all! I have an application consisting of two windows, one communicates to the other and sends it a struct constaining two integers (In this case two rolls of a dice). I will be using events for the following circumstances: Process a sends data to process b, process b displays data Process a closes, in turn closing process b Process b closes a, in turn closing process a I have noticed that if the second process is constantly waiting for the first process to send data then the program will be just sat waiting, which is where the idea of implementing threads on each process occurred and I have started to implement this already. The problem i'm having is that I don't exactly have a lot of experience with threads and events so I'm not sure of the best way to actually implement what I want to do. Following is a small snippet of what I have so far in the producer application; Create thread: case IDM_FILE_ROLLDICE: { hDiceRoll = CreateThread( NULL, // lpThreadAttributes (default) 0, // dwStackSize (default) ThreadFunc(hMainWindow), // lpStartAddress NULL, // lpParameter 0, // dwCreationFlags &hDiceID // lpThreadId (returned by function) ); } break; The data being sent to the other process: DWORD WINAPI ThreadFunc(LPVOID passedHandle) { HANDLE hMainHandle = *((HANDLE*)passedHandle); WCHAR buffer[256]; LPCTSTR pBuf; LPVOID lpMsgBuf; LPVOID lpDisplayBuf; struct diceData storage; HANDLE hMapFile; DWORD dw; //Roll dice and store results in variable storage = RollDice(); hMapFile = CreateFileMapping( (HANDLE)0xFFFFFFFF, // use paging file NULL, // default security PAGE_READWRITE, // read/write access 0, // maximum object size (high-order DWORD) BUF_SIZE, // maximum object size (low-order DWORD) szName); // name of mapping object if (hMapFile == NULL) { dw = GetLastError(); MessageBox(hMainHandle,L"Could not create file mapping object",L"Error",MB_OK); return 1; } pBuf = (LPTSTR) MapViewOfFile(hMapFile, // handle to map object FILE_MAP_ALL_ACCESS, // read/write permission 0, 0, BUF_SIZE); if (pBuf == NULL) { MessageBox(hMainHandle,L"Could not map view of file",L"Error",MB_OK); CloseHandle(hMapFile); return 1; } CopyMemory((PVOID)pBuf, &storage, (_tcslen(szMsg) * sizeof(TCHAR))); //_getch(); MessageBox(hMainHandle,L"Completed!",L"Success",MB_OK); UnmapViewOfFile(pBuf); return 0; } I'm trying to find out how I would integrate an event with the threaded code to signify to the other process that something has happened, I've seen an MSDN article on using events but it's just confused me if anything, I'm coming up on empty whilst searching on the internet too. Thanks for any help Edit: I can only use the Create/Set/Open methods for events, sorry for not mentioning it earlier.

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• printf anomaly after "fork()"

  - by pechenie

  OS: Linux, Language: pure C I'm moving forward in learning C progpramming in general, and C programming under UNIX in a special case :D So, I detected a strange (as for me) behaviour of the printf() function after using a fork() call. Let's take a look at simple test program: #include <stdio.h> #include <system.h> int main() { int pid; printf( "Hello, my pid is %d", getpid() ); pid = fork(); if( pid == 0 ) { printf( "\nI was forked! :D" ); sleep( 3 ); } else { waitpid( pid, NULL, 0 ); printf( "\n%d was forked!", pid ); } return 0; } In this case the output looks like: Hello, my pid is 1111 I was forked! :DHello, my pid is 1111 2222 was forked! Why the second "Hello" string occured in the child's output? Yes, it is exactly what the parent printed on it's start, with the parent's pid. But! If we place '\n' character in the end of each string we got the expected output: #include <stdio.h> #include <system.h> int main() { int pid; printf( "Hello, my pid is %d\n", getpid() ); // SIC!! pid = fork(); if( pid == 0 ) { printf( "I was forked! :D" ); //removed the '\n', no matter sleep( 3 ); } else { waitpid( pid, NULL, 0 ); printf( "\n%d was forked!", pid ); } return 0; } And the output looks like: Hello, my pid is 1111 I was forked! :D 2222 was forked! Why does it happen? Is it ... ummm ... correct behaviour? Or it's a kind of the 'bug'?

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• Deserialization error in a new environment

  - by cerhart

  I have a web application that calls a third-party web service. When I run it locally, I have no problems, but when I move it to my production environment, I get the following error: There is an error in XML document (2, 428). Stack: at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle, XmlDeserializationEvents events) at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle) at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall) at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters) at RMXClasses.RMXContactService.ContactService.getActiveSessions(String user, String pass) in C:\Users\hp\Documents\Visual Studio 2008\Projects\ReklamStore\RMXClasses\Web References\RMXContactService\Reference.cs:line 257 at I have used the same web config file from the production environment but it still works locally. My local machine is a running vista home edition and the production environment is windows server 2003. The application is written in asp.net 3.5, wierdly under the asp.net config tab in iis, 3.5 doesn't show up in the drop down list, although that version of the framework is installed. The error is not being thrown in my code, it happens during serialization. I called the method on the proxy, I have checked the arguments and they are OK. I have also logged the SOAP request and response, and they both look OK as well. I am really at a loss here. Any ideas? SOAP log: This is the soap response that the program seems to have trouble parsing only on server 2003. On my machine the soap is identical, and yet it parses with no problems. SoapResponse BeforeDeserialize; <?xml version="1.0" encoding="UTF-8"?> <SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns1="urn:ContactService" xmlns:ns2="http://api.yieldmanager.com/types" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"><SOAP-ENV:Body><ns1:getActiveSessionsResponse> <sessions SOAP-ENC:arrayType="ns2:session[1]" xsi:type="ns2:array_of_session"> <item xsi:type="ns2:session"> <token xsi:type="xsd:string">xxxxxxxxxxxxxxxxxxxx1ae12517584b</token> <creation_time xsi:type="xsd:dateTime">2009-09-25T05:51:19Z</creation_time> <modification_time xsi:type="xsd:dateTime">2009-09-25T05:51:19Z</modification_time> <ip_address xsi:type="xsd:string">xxxxxxxxxx</ip_address> <contact_id xsi:type="xsd:long">xxxxxx</contact_id></item></sessions> </ns1:getActiveSessionsResponse></SOAP-ENV:Body></SOAP-ENV:Envelope>

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• Reading column header and column values of a data table using LAMBDA(C#3.0)

  - by Newbie

  Consider the folowing where I am reading the data table values and writing to a text file using (StreamWriter sw = new StreamWriter(@"C:\testwrite.txt",true)) { DataPreparation().AsEnumerable().ToList().ForEach(i => { string col1 = i[0].ToString(); string col2 = i[1].ToString(); string col3 = i[2].ToString(); string col4 = i[3].ToString(); sw.WriteLine( col1 + "\t" + col2 + "\t" + col3 + "\t" + col4 + Environment.NewLine ); }); } The data preparation function is as under private static DataTable DataPreparation() { DataTable dt = new DataTable(); dt.Columns.Add("Col1", typeof(string)); dt.Columns.Add("Col2", typeof(int)); dt.Columns.Add("Col3", typeof(DateTime)); dt.Columns.Add("Col4", typeof(bool)); for (int i = 0; i < 10; i++) { dt.Rows.Add("String" + i.ToString(), i, DateTime.Now.Date, (i % 2 == 0) ? true : false); } return dt; } It is working fine. Now in the above described program, it is known to me the Number of columns and the column headers. How to achieve the same in case when the column headers and number of columns are not known at compile time using the lambda expression? I have already done that which is as under public static void WriteToTxt(string directory, string FileName, DataTable outData, string delimiter) { FileStream fs = null; StreamWriter streamWriter = null; using (fs = new FileStream(directory + "\\" + FileName + ".txt", FileMode.Append, FileAccess.Write)) { try { streamWriter = new StreamWriter(fs); streamWriter.BaseStream.Seek(0, SeekOrigin.End); streamWriter.WriteLine(); DataTableReader datatableReader = outData.CreateDataReader(); for (int header = 0; header < datatableReader.FieldCount; header++) { streamWriter.Write(outData.Columns[header].ToString() + delimiter); } streamWriter.WriteLine(); int row = 0; while (datatableReader.Read()) { for (int field = 0; field < datatableReader.FieldCount; field++) { streamWriter.Write(outData.Rows[row][field].ToString() + delimiter); } streamWriter.WriteLine(); row++; } } catch (Exception ex) { throw ex; } } } I am using C#3.0 and framework 3.5 Thanks in advance

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• Basic Custom String Class for C++

  - by wdow88

  Hey all, I'm working on building my own string class with very basic functionality. I am having difficulty understand what is going on with the basic class that I have define, and believe there is some sort of error dealing with the scope occurring. When I try to view the objects I created, all the fields are described as (obviously bad pointer). Also, if I make the data fields public or build an accessor method, the program crashes. For some reason the pointer for the object is 0xccccccccc which points to no where. How can a I fix this? Any help/comments are much appreciated. //This is a custom string class, so far the only functions are //constructing and appending #include<iostream> using namespace std; class MyString1 { public: MyString1() { //no arg constructor char *string; string = new char[0]; string[0] ='\0'; std::cout << string; size = 1; } //constructor receives pointer to character array MyString1(char* chars) { int index = 0; //Determine the length of the array while (chars[index] != NULL) index++; //Allocate dynamic memory on the heap char *string; string = new char[index+1]; //Copy the contents of the array pointed by chars into string, the char array of the object for (int ii = 0; ii < index; ii++) string[ii] = chars[ii]; string[index+1] = '\0'; size = index+1; } MyString1 append(MyString1 s) { //determine new size of the appended array and allocate memory int newsize = s.size + size; MyString1 MyString2; char *newstring; newstring = new char[newsize+1]; int index = 0; //load the first string into the array while (string[index] != NULL) { newstring[index] = string[index]; index++; } //load the second string while (s.string[index] != NULL) { newstring[index] = s.string[index]; index++; } //null terminate newstring[newsize+1] = '\0'; delete string; //generate the object for return MyString2.string=newstring; MyString2.size=newsize; return MyString2; } private: char *string; int size; }; int main() { MyString1 string1; MyString1 string2("Hello There"); MyString1 string3("Buddy"); string2.append(string3); return 0; }

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• What would you suggest as a high school first language?

  - by ldigas

  Edit by OA: After reading some answers I'll just update the question a little. At first I put it a little bluntly, but some of those gave me some good arguments which have to be taken into consideration while making a stand on this one. (these are mostly picked up from comments and answers below). A few things to take into account: to many pupils this is a first programming language - at this stage most of them have trouble grasping a difference between data types, variable passing, ... and whatnot, less alone pointers and similar 'low level stuff' :) they will all have to pass this to get into next grade (well, big majority of them anyway) not all of them have computers at home, not all of them are willing to learn this, less alone interested in - so the concepts have to be taught on a finite time scale in school hours (as well as practice on computers) free literature is a bonus - the teacher will make some scripts and handaways, but still ... I wouldn't like to bear the parents with the burden of buying expensive literature (also, english is not a native language here ... and although they are all learning it, their ability to read it fluently is somewhat questionable) somebody gave an argument - "a language which does not get in the way of ideas" - good one accessibility on different platforms in not expecially important at this point - although most of the suggested ones are available on win as well as linux - not many macs in this part of europe (their prices are sky high for anything but specialised usage) I will check what are the licencing issues on ms express editions about using it massively in high schools for purposes like this - if someone has any info about this, please, do not be shy with it :) A friend of mine, informatics teacher - in EU it comes as something as junior cs teacher, in a local high school asked me what I thought about what should be the first language pupils should be taught? It is a technical school (a little more oriented towards mathematics than the gymnasium, but not computer oriented totally). So I'm asking you - what do you think should be the first language pupils are exposed to in highschool? They have been teaching Pascal so far, but she's not sure that's a good course. She thought about switching to C (which I resented; considering not all pupils have interests in programming, to start with, and should be taught something higher level since they are just gripping the idea of a loop and such ... for a start), I suggested python or ruby (preferably py since it handles all paradigms). What is your opinion on this one? I looked, but didn't find a similar question on SO, so if there is one, please just point me towards it. Edit: The assumption is that none of the pupils have been exposed to any programming in junior school. See also: What is the best way to teach young kids some basic programming concepts? Best ways to teach a beginner to program How and when do you teach a kid to code What is the easiest language to start with? High School Programming

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• Initialize a Variable Again.

  - by SoulBeaver

  That may sound a little confusing. Basically, I have a function CCard newCard() { /* Used to store the string variables intermittantly */ std::stringstream ssPIN, ssBN; int picker1, picker2; int pin, bankNum; /* Choose 5 random variables, store them in stream */ for( int loop = 0; loop < 5; ++loop ) { picker1 = rand() % 8 + 1; picker2 = rand() % 8 + 1; ssPIN << picker1; ssBN << picker2; } /* Convert them */ ssPIN >> pin; ssBN >> bankNum; CCard card( pin, bankNum ); return card; } that creates a new CCard variable and returns it to the caller CCard card = newCard(); My teacher advised me that doing this is a violation of OOP principles and has to be put in the class. He told me to use this method as a constructor. Which I did: CCard::CCard() { m_Sperre = false; m_Guthaben = rand() % 1000; /* Work */ /* Convert them */ ssPIN >> m_Geheimzahl; ssBN >> m_Nummer; } All variables with m_ are member variables. However, the constructor works when I initialize the card normally CCard card(); at the start of the program. However, I also have a function, that is supposed to create a new card and return it to the user, this function is now broken. The original command: card = newCard(); isn't available anymore, and card = new CCard(); doesn't work. What other options do I have? I have a feeling using the constructor won't work, and that I probably should just create a class method newCard, but I want to see if it is somehow at all possible to do it the way the teacher wanted. This is creating a lot of headaches for me. I told the teacher that this is a stupid idea and not everything has to be classed in OOP. He has since told me that Java or C# don't allow code outside of classes, which sounds a little incredible. Not sure that you can do this in C++, especially when templated functions exist, or generic algorithms. Is it true that this would be bad code for OOP in C++ if I didn't force it into a class?

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• help Implementing Object Oriented ansi-C approach??

  - by No Money

  Hey there, I am an Intermediate programmer in Java and know some of the basics in C++. I recently started to scam over "C language" [please note that i emphasized on C language and want to stick with C as i found it to be a perfect tool, so no need for suggestions focusing on why should i move back to C++ or Java]. Moving on, I code an Object Oriented approach in C but kindda scramble with the pointers part. Please understand that I am just a noob trying to extend my knowledge beyond what i learned in High School. Here is my code..... #include <stdio.h> typedef struct per{ int privateint; char *privateString; struct per (*New) (); void (*deleteperOBJ) (struct t_person *); void (*setperNumber) ((struct*) t_person,int); void (*setperString) ((struct*) t_person,char *); void (*dumpperState) ((struct*) t_person); }t_person; void setperNumber(t_person *const per,int num){ if(per==NULL) return; per->privateint=num; } void setperString(t_person *const per,char *string){ if(per==NULL) return; per->privateString=string; } void dumpperState(t_person *const per){ if(per==NULL) return; printf("value of private int==%d\n", per->privateint); printf("value of private string==%s\n", per->privateString); } void deleteperOBJ(struct t_person *const per){ free((void*)t_person->per); t_person ->per = NULL; } main(){ t_person *const per = (struct*) malloc(sizeof(t_person)); per = t_person -> struct per -> New(); per -> setperNumber (t_person *per, 123); per -> setperString(t_person *per, "No money"); dumpperState(t_person *per); deleteperOBJ(t_person *per); } Just to warn you, this program has several errors and since I am a beginner I couldn't help except to post this thread as a question. I am looking forward for assistance. Thanks in advance.

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• How to efficently build an interpreter (lexer+parser) in C?

  - by Rizo

  I'm trying to make a meta-language for writing markup code (such as xml and html) wich can be directly embedded into C/C++ code. Here is a simple sample written in this language, I call it WDI (Web Development Interface): /* * Simple wdi/html sample source code */ #include <mySite> string name = "myName"; string toCapital(string str); html { head { title { mySiteTitle; } link(rel="stylesheet", href="style.css"); } body(id="default") { // Page content wrapper div(id="wrapper", class="some_class") { h1 { "Hello, " + toCapital(name) + "!"; } // Lists post ul(id="post_list") { for(post in posts) { li { a(href=post.getID()) { post.tilte; } } } } } } } Basically it is a C source with a user-friendly interface for html. As you can see the traditional tag-based style is substituted by C-like, with blocks delimited by curly braces. I need to build an interpreter to translate this code to html and posteriorly insert it into C, so that it can be compiled. The C part stays intact. Inside the wdi source it is not necessary to use prints, every return statement will be used for output (in printf function). The program's output will be clean html code. So, for example a heading 1 tag would be transformed like this: h1 { "Hello, " + toCapital(name) + "!"; } // would become: printf("<h1>Hello, %s!</h1>", toCapital(name)); My main goal is to create an interpreter to translate wdi source to html like this: tag(attributes) {content} = <tag attributes>content</tag> Secondly, html code returned by the interpreter has to be inserted into C code with printfs. Variables and functions that occur inside wdi should also be sorted in order to use them as printf parameters (the case of toCapital(name) in sample source). I am searching for efficient (I want to create a fast parser) way to create a lexer and parser for wdi. Already tried flex and bison, but as I am not sure if they are the best tools. Are there any good alternatives? What is the best way to create such an interpreter? Can you advise some brief literature on this issue?

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• infix operation to postfix using stacks

  - by Chris De La O

  We are writing a program that needs to convert an infix operation (4 5/3) to postfix (4 5 3 / ) using stacks. however my convert to postfix does not work as it doesnt not output the postFix array that is supposed to store the conversion from infix notation to postfix notation. here is the code for the convertToPostix fuction. //converts infix expression to postfix expression void ArithmeticExpression::convertToPostfix(char *const inFix, char *const postFix) { //create a stack2 object named cow Stack2<char> cow; cout<<postFix; char thing = '('; //push a left parenthesis onto the stack cow.push(thing); //append a right parenthesis to the end of inFix array strcat(inFix, ")"); int i = 0;//declare an int that will control posFix position //if the stack is not empty if (!cow.isEmpty()) { //loop to run until the last character in inFix array for (int x = 0; inFix[x]!= '\0'; x++ ) { //if the inFix element is a digit if (isdigit(inFix[x])) { postFix[i]=inFix[x];//it is assigned to the next element in postFix array i++;//move on to next element in postFix } //if the inFix element is a left parenthesis else if (inFix[x]=='(') { cow.push(inFix[x]);//push it unto the stack } //if the inFix element is an operator else if (isOperator(inFix[x])) { char oper2 = inFix[x];//char variable holds inFix operator if (isOperator(cow.stackTop()))//if the top node in the stack is an operator { while (isOperator(cow.stackTop()))//and while the top node in the stack is an operator { char oper1 = cow.stackTop();//char variable holds node operator if(precedence( oper1, oper2))//if the node operator has higher presedence than node operator { postFix[i] = cow.pop();//we pop such operator and insert it in postFix array's next element cow.push(inFix[x]);//and push inFix operator unto the stack i++;//move to the next element in posFix } } } //if the top node is not an operator //we push the current inFix operator unto the top of the stack else cow.push(inFix[x]); } //if the inFix element is a right parenthesis else if (inFix[x]==')') { //we pop everything in the stack and insert it in postFix //until we arrive at a left paranthesis while (cow.stackTop()!='(') { postFix[i] = cow.pop(); i++; } //we then pop and discard left parenthesis cow.pop(); } } postFix[i]='\0'; //print !!postFix array!! (not stack) print();//code for this is just cout<<postFix; }

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