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• Compiler reordering around mutex boundaries?

  - by shojtsy

  Suppose I have my own non-inline functions LockMutex and UnlockMutex, which are using some proper mutex - such as boost - inside. How will the compiler know not to reorder other operations with regard to calls to the LockMutex and UnlockMutex? It can not possibly know how will I implement these functions in some other compilation unit. void SomeClass::store(int i) { LockMutex(_m); _field = i; // could the compiler move this around? UnlockMutex(_m); } ps: One is supposed to use instances of classes for holding locks to guarantee unlocking. I have left this out to simplify the example.

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• How to call a function though Control.BeginInvoke in a signal-slot-like fashion?

  - by Dimitri C.

  I'd like a delegate that calls a function in a different thread when it is invoked. Currently, I'm using the following implementation: delegate void someFunctionDelegate(); //... someFunctionDelegate callBackFunction = someForm.SomeFunction; someForm.Invoke(someFunctionDelegate); However, I'd like a more compact form, combining both the someForm instance and the SomeForm.SomeFunction member function. I'm thinking of something like this: var callBackFunction = new AsynchronousCrossThreadDelegate(someForm, SomeForm.SomeFunction); callBackFunction(); // Should call someForm.BeginInvoke(SomeForm.SomeFunction); Is there a way to do so in C#/.NET? Update I'm looking for a solution that will work for functions with 0 or more parameters.

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• Why does Java return a date in GMT-4.5 when choosing Co-ordinated Universal Time time zone in Window

  - by Simon Nickerson

  We have seen a strange issue on some Windows XP machines involving the "Co-ordinated Universal Time" time zone. Not all Windows XP machines seem to have it, but on those that do, the following simple Java program public class TimeTest { public static void main(String[] args) { System.out.println(java.util.TimeZone.getDefault()); System.out.println(new java.util.Date()); } } on JDK 1.6.0_06 prints: sun.util.calendar.ZoneInfo[id="America/Caracas",offset=-16200000,dstSavings=0,useDaylight=false,transitions=5,lastRule=null] Fri Nov 13 05:34:14 VET 2009 (i.e. 4 and a half hours behind GMT). I should add that I am based in London, and have never been to South America. :-) My questions are: Where does Java get this time zone from? I thought Co-ordinated Universal Time was supposed to be the new name for GMT. Why do some Windows machines have this time zone but not others?

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• delete item from array in java

  - by davit-datuashvili

  hello can anybody tell me what is wrong here? i want delete item from array but it shows me error ArrayIndexOutBound exception public class delete{ public static void main(String[]args){ int i; //delete item from array int k[]=new int[]{77,99,44,11,00,55,66,33,10}; //delete 55 int searchkey=55; int nums=k.length; for ( i=0;i<nums;i++) if (k[i]==searchkey) break; for (int t=i;t<nums;t++) k[t]=k[t+1]; nums--; for (int m=0;m<nums;m++){ System.out.println(k[m]); } } }

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• how to implement a callback in runnable to update other swing class

  - by wizztjh

  I have a thread like this public class SMS { class Read implements Runnable { Read(){ Thread th = new Thread(this); th.start(); } @Override public void run() { // TODO Auto-generated method stub while (true){ Variant SMSAPIReturnValue = SMSAPIJava.invoke("ReadSMS"); if (SMSAPIReturnValue.getBoolean()){ String InNumber = SMSAPIJava.getPropertyAsString("MN"); String InMessage = SMSAPIJava.getPropertyAsString("MSG"); } } } } } How do I update the message to another GUI class in the same package(I understand how to put nested class to another package ....). Should I implement a callback function in SMS class? But how? Or should I pass in the Jlabel into the class?

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• C++ vector<T>::iterator operator +

  - by Tom

  Hi, Im holding an iterator that points to an element of a vector, and I would like to compare it to the next element of the vector. Here is what I have Class Point{ public: float x,y; } //Somewhere in my code I do this vector<Point> points = line.getPoints(); foo (points.begin(),points.end()); where foo is: void foo (Vector<Point>::iterator begin,Vector<Point>::iterator end) { std::Vector<Point>::iterator current = begin; for(;current!=end-1;++current) { std::Vector<Point>::iterator next = current + 1; //Compare between current and next. } } I thought that this would work, but current + 1 is not giving me the next element of the vector. I though operator+ was the way to go, but doesnt seem so. Is there a workaround on this? THanks

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• C# Serial Communications - Received Data Lost

  - by Jim Fell

  Hello. Received data in my C# application is getting lost due to the collector array being over-written, rather than appended. private void serialPort1_DataReceived(object sender, SerialDataReceivedEventArgs e) { try { pUartData_c = serialPort1.ReadExisting().ToCharArray(); bUartDataReady_c = true; } catch ( System.Exception ex ) { MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); } } In this example pUartData_c is over-written every time new data is received. On some systems this is not a problem because the data comes in quickly enough. However, on other systems data in the receive buffer is not complete. How can I append received data to pUartData_c, rather than over-write it. I am using Microsoft Visual C# 2008 Express Edition. Thanks.

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• android accelerometer accuracy is extremely poor

  - by user564594

  Wrote a simple program that prints out accelerometer output. mSensorManager = (SensorManager)getSystemService(SENSOR_SERVICE); mSensorManager.registerListener(this,mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_FASTEST); It turns out that: The accelerometer output is always set to "lowest" as determined by: public void onAccuracyChanged(Sensor sensor, int accuracy) { if (collectingData){ accelPrecision.setText("accelerometer accuracy: " + accuracy); } } The actual accelerometer readings are very inaccurate - about 2%-5% fluctuations even when it's resting on the table as far as I can tell it's the same problem on Nexus S, Nexus One and G1 Any idea how it could be made mode accurate / what sets a

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• Context Menu SourceControl Error

  - by developer

  Hi All, I am trying to use contextmenu in my textbox control and I want to bind the textbox value to the value selected in context menu,below is my code <Window.CommandBindings> <CommandBinding Command="local:MyPanel.ChangeTextboxValue" Executed="ChangeTextboxValue_Executed"/> </Window.CommandBindings> CODE-BEHIND public static RoutedUICommand ChangeTextboxValue = new RoutedUICommand ("ChangeTextboxValue", "ChangeTextboxValue", typeof(MyPanel)); private void ChangeTextboxValue_Executed(object sender, ExecutedRoutedEventArgs e) { string oldvalue = Convert.ToString(e.Parameter); (((sender as MenuItem).Parent as ContextMenu).PlacementTarget as TextBox).Text = oldvalue; } oldvalue is the value I want the textbox controls value to change to. I am trying to use above code but it gives me the error, 'Object reference not set to an instance of object'. I tried to debug the app and I get ContextMenu as null.. .Any ideas why??

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• Should a protected property in a C# child class hide access to a public property on the parent?

  - by Tim

  I have the following code: public class Parent { public string MyField { get; set; } } public class Child : Parent { protected new int MyField { get; set; } } I try and access this with: static void Main(string[] args) { Child child = new Child(); child.MyField = "something"; } Visual studio 2008 compiles this without comment, but under Mono (2.4.2, Ubuntu) I get the error message 'HideTest.Child.MyField' is inaccessible due to its protection level (CS0122) Is one implementation or the other more compliant with the standard here?

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• Retreiving data from grid view cell to a text box

  - by Bader

  Hello , i am trying to retrieve a cell data to a textbox , that will happen when i select any row in the grid view , the textbox will take the new value i already enabled auto post back to the textbox here is my code protected void GridView2_SelectedIndexChanged(object sender, EventArgs e) { TextBox3.Text = GridView2.Rows[GridView2.SelectedIndex].Cells[2].Text; } however , there is not error in the syntax , it doesn't retrieve any thing in the textbox , any suggestions ? i am using using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; using System.Data.SqlClient; using System.Data.Sql; i work in C# , Visual studio 2010 express web developer

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• Is it a good practice to create a reference to application context and use it anywhere?

  - by kknight

  I have to use context in many places of my code such as database operations, preference operations, etc. I don't want to pass in context for every method. Is it a good practice to create a reference to application context at the main Activity and use it anywhere such as database operations? So, I don't need some many context in method parameters, and the code can avoid position memory leak due to use of Activity Context. public class MainActivity extends Activity { public static Context s_appContext; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); s_appContext = this.getApplicationContext();

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• Getting class Type information for Elements on a collection

  - by DutrowLLC

  I would like to get gain access to the type of Object held in a Collection. Below is a simplified example of when and why I might want to do this. Is this even possible? List<Address> addressList = new LinkedList<Address>(); Main.addElement(addressList); Class Main{ public void addElement(Object inArgument){ List<Object> argument = (List<Object>)inArgument; argument.add( /* WOULD LIKE TO CREATE A NEW OBJECT OF THE APPROPRIATE TYPE HERE, IN THIS CASE, IT WOULD BE OF TYPE: "Address" */ ); } }

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• How to convert value of Generic Type Argument to a concrete type?

  - by Aleksey Bieneman

  I am trying to convert the value of the generic type parameter T value into integer after making sure that T is in fact integer: public class Test { void DoSomething<T>(T value) { var type = typeof(T); if (type == typeof(int)) { int x = (int)value; // Error 167 Cannot convert type 'T' to 'int' int y = (int)(object)value; // works though boxing and unboxing } } } Although it works through boxing and unboxing, this is an additional performance overhead and i was wandering if there's a way to do it directly. Thank you!

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• TextBox loses text when InvokeRequired == false

  - by Tom

  This is modified code I found on this site. When appending text to a TextBox and InvoveRequired is false the text will display in the box but the next time the function is called and InvokeRequired is true the text string placed by the first call is lost (""). Multiple calls when InvokeRequired is true work as expected. comBox is a type TextBox with multline = true. Any help would be appreciated. public void LogComText(string comText, bool newline) { if (comBox.InvokeRequired) { comBox.BeginInvoke(new Action(delegate { LogComText(comText, newline); })); return; } comBox.AppendText(comText); if (newline) comBox.AppendText(Environment.NewLine); }

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• Simple prime number program - Weird issue with threads C#

  - by Para

  Hi! This is my code: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading; namespace FirePrime { class Program { static bool[] ThreadsFinished; static bool[] nums; static bool AllThreadsFinished() { bool allThreadsFinished = false; foreach (var threadFinished in ThreadsFinished) { allThreadsFinished &= threadFinished; } return allThreadsFinished; } static bool isPrime(int n) { if (n < 2) { return false; } if (n == 2) { return true; } if (n % 2 == 0) { return false; } int d = 3; while (d * d <= n) { if (n % d == 0) { return false; } d += 2; } return true; } static void MarkPrimes(int startNumber,int stopNumber,int ThreadNr) { for (int j = startNumber; j < stopNumber; j++) nums[j] = isPrime(j); lock (typeof(Program)) { ThreadsFinished[ThreadNr] = true; } } static void Main(string[] args) { int nrNums = 100; int nrThreads = 10; //var threadStartNums = new List<int>(); ThreadsFinished = new bool[nrThreads]; nums = new bool[nrNums]; //var nums = new List<bool>(); nums[0] = false; nums[1] = false; for(int i=2;i<nrNums;i++) nums[i] = true; int interval = (int)(nrNums / nrThreads); //threadStartNums.Add(2); //int aux = firstStartNum; //int i = 2; //while (aux < interval) //{ // aux = interval*i; // i=i+1; // threadStartNums.Add(aux); //} int startNum = 0; for (int i = 0; i < nrThreads; i++) { var _thread = new System.Threading.Thread(() => MarkPrimes(startNum, Math.Min(startNum + interval, nrNums), i)); startNum = startNum + interval; //set the thread to run in the background _thread.IsBackground = true; //start our thread _thread.Start(); } while (!AllThreadsFinished()) { Thread.Sleep(1); } for (int i = 0; i < nrNums; i++) if(nums[i]) Console.WriteLine(i); } } } This should be a pretty simple program that is supposed to find and output the first nrNums prime numbers using nrThreads threads working in parallel. So, I just split nrNums into nrThreads equal chunks (well, the last one won't be equal; if nrThreads doesn't divide by nrNums, it will also contain the remainder, of course). I start nrThreads threads. They all test each number in their respective chunk and see if it is prime or not; they mark everything out in a bool array that keeps a tab on all the primes. The threads all turn a specific element in another boolean array ThreadsFinished to true when they finish. Now the weird part begins: The threads never all end. If I debug, I find that ThreadNr is not what I assign to it in the loop but another value. I guess this is normal since the threads execute afterwards and the counter (the variable i) is already increased by then but I cannot understand how to make the code be right. Can anyone help? Thank you in advance. P.S.: I know the algorithm is not very efficient; I am aiming at a solution using the sieve of Eratosthenes also with x given threads. But for now I can't even get this one to work and I haven't found any examples of any implementations of that algorithm anywhere in a language that I can understand.

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• help implementing All Nearest Smaller Values algorithm

  - by davit-datuashvili

  http://en.wikipedia.org/wiki/All_nearest_smaller_values this is site of the problem and here is my code but i have some trouble to implement it import java.util.*; public class stack{ public static void main(String[]args){ int x[]=new int[]{ 0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15 }; Stack<Integer> st=new Stack<Integer>(); for (int a:x){ while (!st.empty() && st.pop()>=a){ System.out.println( st.pop()); if (st.empty()){ break; } else{ st.push(a); } } } } } and here is pseudo code from site S = new empty stack data structure for x in the input sequence: while S is nonempty and the top element of S is greater than or equal to x: pop S if S is empty: x has no preceding smaller value else: the nearest smaller value to x is the top element of S push x onto S

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• How to create a zip file and keep entries for directories?

  - by NathanZ

  I would like to create a zip archive from a folder and keep entries for (non-empty) directories. In the code below, FileInputStream throws a FileNotFoundException when a directory is passed to AddToZip. I have tried to put a condition around the actual writing of bytes but it makes the whole archive invalid. How can I add directory entries to the archive? public static void addToZip(File directoryToZip, File file, ZipOutputStream zos) throws FileNotFoundException, IOException { String zipFilePath = file.getCanonicalPath().substring(directoryToZip.getCanonicalPath().length() + 1,file.getCanonicalPath().length()); System.out.println("Writing '" + zipFilePath + "' to zip file"); ZipEntry zipEntry = new ZipEntry(zipFilePath); zos.putNextEntry(zipEntry); FileInputStream fis = new FileInputStream(file); // Throws a FileNotFoundException when directory byte[] bytes = new byte[1024]; int length; while ((length = fis.read(bytes)) >= 0) { zos.write(bytes, 0, length); } zos.closeEntry(); fis.close(); }

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• Help me understand the code snippet in c#

  - by Benny

  I am reading this blog: Pipes and filters pattern I am confused by this code snippet: public class Pipeline<T> { private readonly List<IOperation<T>> operations = new List<IOperation<T>>(); public Pipeline<T> Register(IOperation<T> operation) { operations.Add(operation); return this; } public void Execute() { IEnumerable<T> current = new List<T>(); foreach (IOperation<T> operation in operations) { current = operation.Execute(current); } IEnumerator<T> enumerator = current.GetEnumerator(); while (enumerator.MoveNext()); } } what is the purpose of this statement: while (enumerator.MoveNext());? seems this code is a noop.

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• C# Creating thumbnail (low quality and big size problem)

  - by ile

  public void CreateThumbnail(Image img1, Photo photo, string targetDirectoryThumbs) { int newWidth = 700; int newHeight = 700; double ratio = 0; if (img1.Width > img1.Height) { ratio = img1.Width / (double)img1.Height; newHeight = (int)(newHeight / ratio); } else { ratio = img1.Height / (double)img1.Width; newWidth = (int)(newWidth / ratio); } Image bmp1 = img1.GetThumbnailImage(newWidth, newHeight, null, IntPtr.Zero); bmp1.Save(targetDirectoryThumbs + photo.PhotoID + ".jpg"); img1.Dispose(); bmp1.Dispose(); } I've put 700px so that you can have better insight of the problem. Here is original image and resized one. Any good recommendation? Thanks, Ile

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• Java multidimensional array and scanner novice Q

  - by Max

  I'm new to Java and trying to in essence implement a grid with a character, and if the user inputs 'w' 'a' 's' or 'd' the character moves up/down/left/right within the plane. I created a multidimensional array sized 10x10 public static String[][] grid = new String[10][10]; And then just used a for loop to print "*"s in a 10x10 grid, except for grid[a][b] which is equal to character "A" i.e. my thing to be moved around. That seemed to work alright, then I needed to detect the 'wasd' input from the user so I set up a: Scanner in = new Scanner (System.in); while (in.hasNext()) And I had then: String s = in.next(); char ch = s.charAt(0); switch (ch) but I couldn't make this work, and it wasn't because I didn't complete the "switch" statement, I did, I just see it void copying and pasting the entire thing. I'm sure its incredibly easy slight thing I am missing, can you please point it out for me?

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• Vim: replacing start and end of a visual char, line or block

  - by gattu marrudu

  I am trying to find a shortcut to place a custom comment sequence on my code, e.g.: /* start of comment blah end of comment /**/ (it is easier to void the comment by just adding a / to the beginning) I would like to do this in Vim by selecting a visual line, block or char and adding '/' characters at the beginning of the block and '/*/' at the end, plus newlines. After selecting some lines (Shift-V) I tried this: '<,'>s/\(.*\)/\/*\r\1\r\/**\// But it adds the comment chars at EACH newline. How can I only apply the substitution at the beginning and end of the selected range? Thanks gm

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• Passing an array argument from C# to a C++/CLI method

  - by jco

  I know only very little about C++/CLI, but I have a simple problem that needs a solution. I have a C++/CLI class method that takes a byte-array as a parameter. The array is of a pre-determined length, and can be allocated in C# beforehand. The array is supposed to be filled with data by the C++/CLI method. How do I declare the method and then call it from C#? I tried something like having the following in my C++/CLI class: public ref class C { public: void FillBytes(array<BYTE^>^ bytes); }; And then, in C#: o = new C(); var bytes = new byte[3]; o.FillBytes(bytes); But that didn't work at all :).

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• iPhone SDK - How to display a photo taken with the camera inside a UINavigationController?

  - by dan

  This is my code so far: /* class: myViewController @interface myViewController: UIViewController <UIImagePickerControllerDelegate, UINavigationControllerDelegate> */ - (IBAction) getPicture { UIImagePickerController * picker = [[UIImagePickerController alloc] init]; picker.delegate = self; picker.sourceType = UIImagePickerControllerSourceTypeCamera; [self presentModalViewController:picker animated:YES]; } - (void) imagePickerController:(UIImagePickerController *)thePicker didFinishPickingMediaWithInfo:(NSDictionary *)imageInfo { [[thePicker parentViewController] dismissModalViewControllerAnimated:YES]; UIImage *img = [imageInfo objectForKey:@"UIImagePickerControllerOriginalImage"]; self.myImageView.image = img; } So basically I'm trying to get a photo from the iPhone camera and display it in a UIImageView. This works perfectly fine as long the class myViewController is displayed as a standalone view. If I'm putting the View inside a UINavigationController the UIImageView won't display the image after taking one with the camera. But if I choose a picture from the library everything is fine again. So why does the UIImageView won't display a image taken with the camera inside a UINavigationController?

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• Lifetime of implicitly casted temporaries

  - by Answeror

  I have seen this question. It seems that regardless of the cast, the temporary object(s) will "survive" until the fullexpression evaluated. But in the following scenario: void foo(boost::tuple<const double&> n) { printf("%lf\n", n.get<0>()); } int main() { foo(boost::tuple<const double&>(2));//#1 foo(boost::make_tuple(2));//#2 return 0; } 1 run well, but 2 do not. And MSVC gave me a warning about 2: "reference member is initialized to a temporary that doesn't persist after the constructor exits" Now I am wondering why they both make a temporary "double" object and pass it to boost::tuple<const double&> and only 2 failed.

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