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• WebClient error when using a thread in .NET 4

  - by Kiranu

  I'm having a very weird error using the WebClient class in .NET 4. The app simply downloads some files off the internet and provides output on a textbox (the GUI is WPF). The method that does this is the following: void DownloadFiles(object files) { fileL = (List<string>) files; foreach (string url in fileL) { byte[] data; using (System.Net.WebClient k = new WebClient()) { data = k.DownloadData(url); } //Bunch of irrelevant code goes here... } } (I added the using while trying to divine [yes I'm that desperate/ignorant] a solution, the problem happens even if the webclient is declared and initialized outside the foreach loop) Now the problem appears only when I'm executing this method on a thread separate from the WPF UI main thread. If it is executed on the UI thread then it works perfectly. When a new thread is created with: Thread t = new Thread(DownloadFiles); t.Start(files); The first time the code goes into the loop it will work, but when its the second pass inside the loop, I will always receive a TargetParameterCountException. I can't make any sense of this error. Any help is very much appreciated. EDIT Here are the Exception Details: Exception.Message = "Parameter count mismatch." Exception.InnerException = null Exception.Source = " mscorlib" The StackTrace follows: at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks) at System.Delegate.DynamicInvokeImpl(Object[] args) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler) at System.Windows.Threading.DispatcherOperation.InvokeImpl() at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object state) at System.Threading.ExecutionContext.runTryCode(Object userData) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Windows.Threading.DispatcherOperation.Invoke() at System.Windows.Threading.Dispatcher.ProcessQueue() at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler) at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs) at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam) at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg) at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame) at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame) at System.Windows.Threading.Dispatcher.Run() at System.Windows.Application.RunDispatcher(Object ignore) at System.Windows.Application.RunInternal(Window window) at System.Windows.Application.Run(Window window) at System.Windows.Application.Run() at FileDownloader.App.Main() in d:\mis documentos\visual studio 2010\Projects\OneMangaDownloader\FileDownloader\obj\x86\Debug\App.g.cs:line 0 at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args) at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart()

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• Converting cv::Mat to IplImage*

  - by amr

  The documentation on this seems incredibly spotty. I've basically got an empty array of IplImage*s (IplImage** imageArray) and I'm calling a function to import an array of cv::Mats - I want to convert my cv::Mat into an IplImage* so I can copy it into the array. Currently I'm trying this: while(loop over cv::Mat array) { IplImage* xyz = &(IplImage(array[i])); cvCopy(iplimagearray[i], xyz); } Which generates a segfault. Also trying: while(loop over cv::Mat array) { IplImage* xyz; xyz = &array[i]; cvCopy(iplimagearray[i], xyz); } Which gives me a compile time error of: error: cannot convert ‘cv::Mat*’ to ‘IplImage*’ in assignment Stuck as to how I can go further and would appreciate some advice :)

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• Replace with wildcard, in SQL

  - by Jay

  I know MS T-SQL does not support regular expression, but I need similar functionality. Here's what I'm trying to do: I have a varchar table field which stores a breadcrumb, like this: /ID1:Category1/ID2:Category2/ID3:Category3/ Each Category name is preceded by its Category ID, separated by a colon. I'd like to select and display these breadcrumbs but I want to remove the Category IDs and colons, like this: /Category1/Category2/Category3/ Everything between the leading slash (/) up to and including the colon (:) should be stripped out. I don't have the option of extracting the data, manipulating it externally, and re-inserting back into the table; so I'm trying to accomplish this in a SELECT statement. I also can't resort to using a cursor to loop through each row and clean each field with a nested loop, due to the number of rows returned in the SELECT. Can this be done? Thanks all - Jay

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• building median for each string in IList<IDictionary<string, double>>

  - by Oliver

  Actually i have a little brain bender and and just can't find the right direction to get it to work: Given is an IList<IDictionary<string, double>> and it is filled as followed: Name|Value ----+----- "x" | 3.8 "y" | 4.2 "z" | 1.5 ----+----- "x" | 7.2 "y" | 2.9 "z" | 1.3 ----+----- ... | ... To fill this up with some random data i used the following methods: var list = CreateRandomPoints(new string[] { "x", "y", "z" }, 20); This will work as followed: private IList<IDictionary<string, double>> CreateRandomPoints(string[] variableNames, int count) { var list = new List<IDictionary<string, double>>(count); list.AddRange(CreateRandomPoints(variableNames).Take(count)); return list; } private IEnumerable<IDictionary<string, double>> CreateRandomPoints(string[] variableNames) { while (true) yield return CreateRandomLine(variableNames); } private IDictionary<string, double> CreateRandomLine(string[] variableNames) { var dict = new Dictionary<string, double>(variableNames.Length); foreach (var variable in variableNames) { dict.Add(variable, _Rand.NextDouble() * 10); } return dict; } Also i can say that it is already ensured that every Dictionary within the list contains the same keys (but from list to list the names and count of the keys can change). So that's what i got. Now to the things i need: I'd like to get the median (or any other math aggregate operation) of each Key within all the dictionaries, so that my function to call would look something like: IDictionary<string, double> GetMedianOfRows(this IList<IDictionary<string, double>> list) The best would be to give some kind of aggregate operation as a parameter to the function to make it more generic (don't know if the func has the correct parameters, but should imagine what i'd like to do): private IDictionary<string, double> Aggregate(this IList<IDictionary<string, double>> list, Func<IEnumerable<double>, double> aggregator) Also my actual biggest problem is to do the job with a single iteration over the list, cause if within the list are 20 variables with 1000 values i don't like to iterate 20 times over the list. Instead i would go one time over the list and compute all twenty variables at once (The biggest advantage of doing it that way would be to use this also as IEnumerable<T> on any part of the list in a later step). So here is the code i already got: public static IDictionary<string, double> GetMedianOfRows(this IList<IDictionary<string, double>> list) { //Check of parameters is left out! //Get first item for initialization of result dictionary var firstItem = list[0]; //Create result dictionary and fill in variable names var dict = new Dictionary<string, double>(firstItem.Count); //Iterate over the whole list foreach (IDictionary<string, double> row in list) { //Iterate over each key/value pair within the list foreach (var kvp in row) { //How to determine median of all values? } } return dict; } Just to be sure here is a little explanation about the Median.

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• Recognize objects in image

  - by DoomStone

  Hello I am in the process of doing a school project, where we have a robot driving on the ground in between Flamingo plates. We need to create an algorithm that can identify the locations of these plates, so we can create paths around them (We are using A Star for that). So far have we worked with AForged Library and we have created the following class, the only problem with this is that when it create the rectangles dose it not take in account that the plates are not always parallel with the camera border, and it that case will it just create a rectangle that cover the whole plate. So we need to some way find the rotation on the object, or another way to identify this. I have create an image that might help explain this Image the describe the problem: http://img683.imageshack.us/img683/9835/imagerectangle.png Any help on how I can do this would be greatly appreciated. Any other information or ideers are always welcome. public class PasteMap { private Bitmap image; private Bitmap processedImage; private Rectangle[] rectangels; public void initialize(Bitmap image) { this.image = image; } public void process() { processedImage = image; processedImage = applyFilters(processedImage); processedImage = filterWhite(processedImage); rectangels = extractRectangles(processedImage); //rectangels = filterRectangles(rectangels); processedImage = drawRectangelsToImage(processedImage, rectangels); } public Bitmap getProcessedImage { get { return processedImage; } } public Rectangle[] getRectangles { get { return rectangels; } } private Bitmap applyFilters(Bitmap image) { image = new ContrastCorrection(2).Apply(image); image = new GaussianBlur(10, 10).Apply(image); return image; } private Bitmap filterWhite(Bitmap image) { Bitmap test = new Bitmap(image.Width, image.Height); for (int width = 0; width < image.Width; width++) { for (int height = 0; height < image.Height; height++) { if (image.GetPixel(width, height).R > 200 && image.GetPixel(width, height).G > 200 && image.GetPixel(width, height).B > 200) { test.SetPixel(width, height, Color.White); } else test.SetPixel(width, height, Color.Black); } } return test; } private Rectangle[] extractRectangles(Bitmap image) { BlobCounter bc = new BlobCounter(); bc.FilterBlobs = true; bc.MinWidth = 5; bc.MinHeight = 5; // process binary image bc.ProcessImage( image ); Blob[] blobs = bc.GetObjects(image, false); // process blobs List<Rectangle> rects = new List<Rectangle>(); foreach (Blob blob in blobs) { if (blob.Area > 1000) { rects.Add(blob.Rectangle); } } return rects.ToArray(); } private Rectangle[] filterRectangles(Rectangle[] rects) { List<Rectangle> Rectangles = new List<Rectangle>(); foreach (Rectangle rect in rects) { if (rect.Width > 75 && rect.Height > 75) Rectangles.Add(rect); } return Rectangles.ToArray(); } private Bitmap drawRectangelsToImage(Bitmap image, Rectangle[] rects) { BitmapData data = image.LockBits(new Rectangle(0, 0, image.Width, image.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); foreach (Rectangle rect in rects) Drawing.FillRectangle(data, rect, Color.Red); image.UnlockBits(data); return image; } }

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• Simple C# CSV Excel export class

  - by Chris

  Thought this might be handy for someone, this is an extremely simple CSV export class that I needed. Features: Extremely simple to use Escapes commas and quotes so excel handles them fine Exports date and datetimes in timezone-proof format Without further ado: using System; using System.Data.SqlTypes; using System.IO; using System.Text; using System.Collections.Generic; /// <summary> /// Simple CSV export /// Example: /// CsvExport myExport = new CsvExport(); /// /// myExport.AddRow(); /// myExport["Region"] = "New York, USA"; /// myExport["Sales"] = 100000; /// myExport["Date Opened"] = new DateTime(2003, 12, 31); /// /// myExport.AddRow(); /// myExport["Region"] = "Sydney \"in\" Australia"; /// myExport["Sales"] = 50000; /// myExport["Date Opened"] = new DateTime(2005, 1, 1, 9, 30, 0); /// /// Then you can do any of the following three output options: /// string myCsv = myExport.Export(); /// myExport.ExportToFile("Somefile.csv"); /// byte[] myCsvData = myExport.ExportToBytes(); /// </summary> public class CsvExport { /// <summary> /// To keep the ordered list of column names /// </summary> List<string> fields = new List<string>(); /// <summary> /// The list of rows /// </summary> List<Dictionary<string, object>> rows = new List<Dictionary<string, object>>(); /// <summary> /// The current row /// </summary> Dictionary<string, object> currentRow { get { return rows[rows.Count - 1]; } } /// <summary> /// Set a value on this column /// </summary> public object this[string field] { set { // Keep track of the field names, because the dictionary loses the ordering if (!fields.Contains(field)) fields.Add(field); currentRow[field] = value; } } /// <summary> /// Call this before setting any fields on a row /// </summary> public void AddRow() { rows.Add(new Dictionary<string, object>()); } /// <summary> /// Converts a value to how it should output in a csv file /// If it has a comma, it needs surrounding with double quotes /// Eg Sydney, Australia -> "Sydney, Australia" /// Also if it contains any double quotes ("), then they need to be replaced with quad quotes[sic] ("") /// Eg "Dangerous Dan" McGrew -> """Dangerous Dan"" McGrew" /// </summary> string MakeValueCsvFriendly(object value) { if (value == null) return ""; if (value is INullable && ((INullable)value).IsNull) return ""; if (value is DateTime) { if (((DateTime)value).TimeOfDay.TotalSeconds==0) return ((DateTime)value).ToString("yyyy-MM-dd"); return ((DateTime)value).ToString("yyyy-MM-dd HH:mm:ss"); } string output = value.ToString(); if (output.Contains(",") || output.Contains("\"")) output = '"' + output.Replace("\"", "\"\"") + '"'; return output; } /// <summary> /// Output all rows as a CSV returning a string /// </summary> public string Export() { StringBuilder sb = new StringBuilder(); // The header foreach (string field in fields) sb.Append(field).Append(","); sb.AppendLine(); // The rows foreach (Dictionary<string, object> row in rows) { foreach (string field in fields) sb.Append(MakeValueCsvFriendly(row[field])).Append(","); sb.AppendLine(); } return sb.ToString(); } /// <summary> /// Exports to a file /// </summary> public void ExportToFile(string path) { File.WriteAllText(path, Export()); } /// <summary> /// Exports as raw UTF8 bytes /// </summary> public byte[] ExportToBytes() { return Encoding.UTF8.GetBytes(Export()); } }

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• UIScrollview setContentOffset immediate animation?

  - by Jess

  Is there anyway to get the setContentOffset animation to happen immediately instead of waiting until the app returns to the main run loop? I tried setting the animation property to NO and nesting inside of an animation block but it still waits until returning to the main run loop. I've also tried using a sub method to perform the animation. My problem is I perform some heavy work after setting the contentOffset so the scroll view waits until this work is complete to animate the setting of the content offset so it appears to lag for a second.

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• Workflow Foundation 4 WorkflowServiceHost Message Correlation

  - by Lygpt

  I have 2 methods on a workflow service hosted in WorkflowServiceHost. The first method is called and starts the regular workflow sequence - talking to other web services, database work etc but on some occassions will pause and persist to db (as-in the delay activity) and wait for some human action to take place before continuing. I need my second method to be able to hook into this persisted workflow, change a local variable and then continuing processing. I have looked at message based correlation in workflow but can only seem to find examples where some kind of infinite while loop keeps the workflow instance active so that the second service method call can arrive whilst it's still running. Because my workflow instance will be delayed/persisted, the second service call doesn't seem to get anywhere (I can't have an infinite while loop keeping the workflow instance active). I hope this makes sense - cheers!

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• realtime logging

  - by Ion Todirel

  I have an application which has a loop, part of a "Scheduler", which runs at all time and is the heart of the application. Pretty much like a game loop, just that my application is a WPF application and it's not a game. Naturally the application does logging at many points, but the Scheduler does some sensitive monitoring, and sometimes it's impossible just from the logs to tell what may have gotten wrong (and by wrong I don't mean exceptions) or the current status. Because Scheduler's inner loop runs at short intervals, you can't do file I/O-based logging (or using the Event Viewer) in there. First, you need to watch it in real-time, and secondly the log file would grow in size very fast. So I was thinking of ways to show this data to the user in the realtime, some things I considered: Display the data in realtime in the UI Use AllocConsole/WriteConsole to display this information in a console Use a different console application which would display this information, communicate between the Scheduler and the console app using pipes or other IPC techniques Use Windows' Performance Monitor and somehow feed it with this information ETW Displaying in the UI would have its issues. First it doesn't integrate with the UI I had in mind for my application, and I don't want to complicate the UI just for this. This diagnostics would only happen rarely. Secondly, there is going to be some non-trivial data protection, as the Scheduler has it's own thread. A separate console window would work probably, but I'm still worried if it's not too much threshold. Allocating my own console, as this is a windows app, would probably be better than a different console application (3), as I don't need to worry about IPC communication, and non-blocking communication. However a user could close the console I allocated, and it would be problematic in that case. With a separate process you don't have to worry about it. Assuming there is an API for Performance Monitor, it wouldn't be integrated too well with my app or apparent to the users. Using ETW also doesn't solve anything, just a random idea, I still need to display this information somehow. What others think, would there be other ways I missed?

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• Trapping Error Status in MSBuild

  - by Ruben Bartelink

  As part of some build automation of running xUnit.net tests with MSBuild, I'm running into a case where I need to loop over a batch of items. Inside the loop, I need to detect whether an iteration failed, but I want to continue executing regardless. Then after the batched bit, I need to know whether one or more errors have occurred in order to report the outcome to TeamBuild. IOW, in pseudocode: Task Name=RunTests CreateItems ForEach item CallTarget Target=RunTest ContinueOnError=true CombineNUnitResults Report success/failure Task Name=RunTest XUnit item I'm hoping this can be achieved without a custom task (or hacking the xunit.net MSBuild task as Jonne did). (But willing to use MSBuild Community or Sdc tasks) And @BradWilson: I this is isnt possible to do cleanly, I'll be looking for Jonne's change a la the NUnit task to also make it into the xunit task See also: http://stackoverflow.com/questions/517560/how-do-i-get-team-build-to-show-test-results-and-coverage-for-xunit-net-test-suit

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• Jquery - $(this) in in nested loops

  - by Smickie

  Hi, I can't figure out how to do something in Jquery. Let's say I have a form with many select drop-downs and do this... $('#a_form select').each(function(index) { }); When inside this loop I want to loop over each of the options, but I can't figure out how to do this, is it something like this....? $('#a_form select').each(function(index) { $(this + 'option').each(function(index) { //do things }); }); I can't quite get it to work, and advice? Cheers.

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• XML Socket and Regular Socket in Flash/Flex does not send message immediately.

  - by kramer

  I am trying to build a basic RIA where my Flex application client opens an XML socket, sends the xml message "people_list" to server, and prints out the response. I have ruby at the server side and I have successfully set up the security policy stuff. The ruby xml server, successfully accepts the connections from Flex, successfully detects when they are closed and can also send messages to client. But; there is a problem... It cannot receive messages from flex client. The messages sent from flex client are queued and sent as one package when the socket is closed. Therefore, the whole wait-for-request-then-reply thing is not working... This is also -kinda- mentioned in the XMLSocket.send() document, where it is stated that the messages are sent async so; they may be delivered at any time in future. But; I need them to be synced, flushed or whatever. This is the server side code: require 'socket' require 'observer' class Network_Reader_Ops include Observable @@reader_listener_socket = UDPSocket.new @@reader_broadcast_socket = UDPSocket.new @@thread_id def initialize @@reader_broadcast_socket.setsockopt(Socket::SOL_SOCKET, Socket::SO_BROADCAST, 1) @@reader_broadcast_socket.setsockopt(Socket::SOL_SOCKET, Socket::SO_REUSEADDR, 1) @@reader_listener_socket.setsockopt(Socket::SOL_SOCKET, Socket::SO_REUSEADDR, 1) @@reader_broadcast_socket.bind('', 50050) @@reader_listener_socket.bind('', 50051) @@thread_id = Thread.start do loop do begin text, sender = @@reader_listener_socket.recvfrom_nonblock 1024 print("Knock response recived: ", text) notify_observers text rescue Errno::EAGAIN retry rescue Errno::EWOULDBLOCK retry end end end end def query @@reader_broadcast_socket.send("KNOCK KNOCK", 0, "255.255.255.255", 50050) end def stop Thread.kill @@thread_id end end class XMLSocket_Connection attr_accessor :connection_id def update (data) connection_id.write(data+"\0") end end begin # Set EOL for Flash $/ = '\x00' xml_socket = TCPServer.open('', '4444') security_policy_socket = TCPServer.open('', '843') xml_socket.setsockopt(Socket::SOL_SOCKET, Socket::SO_REUSEADDR, 1) security_policy_socket.setsockopt(Socket::SOL_SOCKET, Socket::SO_REUSEADDR, 1) a = Thread.start do network_ops = nil loop { accepted_connection = xml_socket.accept print(accepted_connection.peeraddr, " is accepted\n") while accepted_connection.gets incoming = $_.dump print("Received: ", incoming) if incoming == "<request>readers on network</request>" then network_ops = Network_Reader_Ops.new this_con = XMLSocket_Connection.new this_con.connection_id = accepted_connection network_ops.add_observer this_con network_ops.query end end if not network_ops.nil? then network_ops.delete_observer this_con network_ops.stop network_ops = nil end print(accepted_connection, " is gone\n") accepted_connection.close } end b = Thread.start do loop { accepted_connection = security_policy_socket.accept Thread.start do current_connection = accepted_connection while current_connection.gets if $_ =~ /.*policy\-file.*/i then current_connection.write("<cross-domain-policy><allow-access-from domain="*" to-ports="*" /></cross-domain-policy>\0") end end current_connection.close end } end a.join b.join rescue puts "FAILED" retry end And this is the flex/flash client side code: UPDATE: I have also tried using regular socket and calling flush() method but; the result was same. private var socket:XMLSocket = new XMLSocket(); protected function stopXMLSocket():void { socket.close(); } protected function startXMLSocket():void { socket.addEventListener(DataEvent.DATA, dataHandler); socket.connect(xmlSocketServer_address, xmlSocketServer_port); socket.send("<request>readers on network</request>"); } protected function dataHandler(event:DataEvent):void { mx.controls.Alert.show(event.data); } How do I achieve the described behaviour?

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• How to do early binding for event handler in JavaScript? (example with jQuery)

  - by Sven Larson

  JavaScript's late binding is great. But how do I early bind when I want to? I am using jQuery to add links with event handlers in a loop to a div. The variable 'aTag ' changes in the loop. When I click the links later, all links alert the same message, which is the last value of 'aTag'. How do I bind a different alert message to all links? All links should alert with the value that aTag had when the event handler was added, not when it was clicked. for (aTag in tagList) { if (tagList.hasOwnProperty(aTag)) { nextTag = $('<a href="#"></a>'); nextTag.text(aTag); nextTag.click(function() { alert(aTag); }); $('#mydiv').append(nextTag); $('#mydiv').append(' '); } }

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• How to count each digit in a range of integers?

  - by Carlos Gutiérrez

  Imagine you sell those metallic digits used to number houses, locker doors, hotel rooms, etc. You need to find how many of each digit to ship when your customer needs to number doors/houses: 1 to 100 51 to 300 1 to 2,000 with zeros to the left The obvious solution is to do a loop from the first to the last number, convert the counter to a string with or without zeros to the left, extract each digit and use it as an index to increment an array of 10 integers. I wonder if there is a better way to solve this, without having to loop through the entire integers range. Solutions in any language or pseudocode are welcome. Edit: Answers review John at CashCommons and Wayne Conrad comment that my current approach is good and fast enough. Let me use a silly analogy: If you were given the task of counting the squares in a chess board in less than 1 minute, you could finish the task by counting the squares one by one, but a better solution is to count the sides and do a multiplication, because you later may be asked to count the tiles in a building. Alex Reisner points to a very interesting mathematical law that, unfortunately, doesn’t seem to be relevant to this problem. Andres suggests the same algorithm I’m using, but extracting digits with %10 operations instead of substrings. John at CashCommons and phord propose pre-calculating the digits required and storing them in a lookup table or, for raw speed, an array. This could be a good solution if we had an absolute, unmovable, set in stone, maximum integer value. I’ve never seen one of those. High-Performance Mark and strainer computed the needed digits for various ranges. The result for one millon seems to indicate there is a proportion, but the results for other number show different proportions. strainer found some formulas that may be used to count digit for number which are a power of ten. Robert Harvey had a very interesting experience posting the question at MathOverflow. One of the math guys wrote a solution using mathematical notation. Aaronaught developed and tested a solution using mathematics. After posting it he reviewed the formulas originated from Math Overflow and found a flaw in it (point to Stackoverflow :). noahlavine developed an algorithm and presented it in pseudocode. A new solution After reading all the answers, and doing some experiments, I found that for a range of integer from 1 to 10n-1: For digits 1 to 9, n*10(n-1) pieces are needed For digit 0, if not using leading zeros, n*10n-1 - ((10n-1) / 9) are needed For digit 0, if using leading zeros, n*10n-1 - n are needed The first formula was found by strainer (and probably by others), and I found the other two by trial and error (but they may be included in other answers). For example, if n = 6, range is 1 to 999,999: For digits 1 to 9 we need 6*105 = 600,000 of each one For digit 0, without leading zeros, we need 6*105 – (106-1)/9 = 600,000 - 111,111 = 488,889 For digit 0, with leading zeros, we need 6*105 – 6 = 599,994 These numbers can be checked using High-Performance Mark results. Using these formulas, I improved the original algorithm. It still loops from the first to the last number in the range of integers, but, if it finds a number which is a power of ten, it uses the formulas to add to the digits count the quantity for a full range of 1 to 9 or 1 to 99 or 1 to 999 etc. Here's the algorithm in pseudocode: integer First,Last //First and last number in the range integer Number //Current number in the loop integer Power //Power is the n in 10^n in the formulas integer Nines //Nines is the resut of 10^n - 1, 10^5 - 1 = 99999 integer Prefix //First digits in a number. For 14,200, prefix is 142 array 0..9 Digits //Will hold the count for all the digits FOR Number = First TO Last CALL TallyDigitsForOneNumber WITH Number,1 //Tally the count of each digit //in the number, increment by 1 //Start of optimization. Comments are for Number = 1,000 and Last = 8,000. Power = Zeros at the end of number //For 1,000, Power = 3 IF Power 0 //The number ends in 0 00 000 etc Nines = 10^Power-1 //Nines = 10^3 - 1 = 1000 - 1 = 999 IF Number+Nines <= Last //If 1,000+999 < 8,000, add a full set Digits[0-9] += Power*10^(Power-1) //Add 3*10^(3-1) = 300 to digits 0 to 9 Digits[0] -= -Power //Adjust digit 0 (leading zeros formula) Prefix = First digits of Number //For 1000, prefix is 1 CALL TallyDigitsForOneNumber WITH Prefix,Nines //Tally the count of each //digit in prefix, //increment by 999 Number += Nines //Increment the loop counter 999 cycles ENDIF ENDIF //End of optimization ENDFOR SUBROUTINE TallyDigitsForOneNumber PARAMS Number,Count REPEAT Digits [ Number % 10 ] += Count Number = Number / 10 UNTIL Number = 0 For example, for range 786 to 3,021, the counter will be incremented: By 1 from 786 to 790 (5 cycles) By 9 from 790 to 799 (1 cycle) By 1 from 799 to 800 By 99 from 800 to 899 By 1 from 899 to 900 By 99 from 900 to 999 By 1 from 999 to 1000 By 999 from 1000 to 1999 By 1 from 1999 to 2000 By 999 from 2000 to 2999 By 1 from 2999 to 3000 By 1 from 3000 to 3010 (10 cycles) By 9 from 3010 to 3019 (1 cycle) By 1 from 3019 to 3021 (2 cycles) Total: 28 cycles Without optimization: 2,235 cycles Note that this algorithm solves the problem without leading zeros. To use it with leading zeros, I used a hack: If range 700 to 1,000 with leading zeros is needed, use the algorithm for 10,700 to 11,000 and then substract 1,000 - 700 = 300 from the count of digit 1. Benchmark and Source code I tested the original approach, the same approach using %10 and the new solution for some large ranges, with these results: Original 104.78 seconds With %10 83.66 With Powers of Ten 0.07 A screenshot of the benchmark application: If you would like to see the full source code or run the benchmark, use these links: Complete Source code (in Clarion): http://sca.mx/ftp/countdigits.txt Compilable project and win32 exe: http://sca.mx/ftp/countdigits.zip Accepted answer noahlavine solution may be correct, but l just couldn’t follow the pseudo code, I think there are some details missing or not completely explained. Aaronaught solution seems to be correct, but the code is just too complex for my taste. I accepted strainer’s answer, because his line of thought guided me to develop this new solution.

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• How can I listen to multiple Serial Ports asynchronously in C#

  - by Kamiel Wanrooij

  I have an application that listens to a piece of hardware on a USB to Serial converter. My application should monitor more than one serial port at the same time. I loop the serial ports I need to listen to, and create a thread for each port. In the thread I have my data handing routine. When I assign one port, it runs flawlessly. When I listen to the other one, it also works. When I open both ports however, the second port always throws an UnauthorizedAccessException when calling serialPort.Open(). It does not matter in what order I open the ports, the second one always fails. I listen to the ports using serialPort.ReadLine() in a while loop. Can .NET open more than one port at the same time? Can I listen to both? Or should I use another (thread safe?) way to access my serial port events?

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• c - convert a mixed-case string to all lower case

  - by hatorade

  is the best/cleanest way to just do a for loop iterating through each position and call tolower() on it?

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• plpgsql function to generate random readable strings

  - by Peter

  Hi I have written the following function but it's isn't returning anything when I run it. Can somebody help identify the issue? CREATE OR REPLACE FUNCTION GenerateReadableRandomString ( len INT ) RETURNS varchar AS $$ DECLARE validchars VARCHAR; randomstr VARCHAR; randint INT; i INT; BEGIN validchars := 'ABCEFHJKLMNPRTWXY3478'; i := 0; LOOP randint := ceil(random() * char_length(validchars)); randomstr := randomstr || substring(validchars from randint for 1); i := i + 1; EXIT WHEN i = len; END LOOP; RETURN randomstr; END; $$ LANGUAGE plpgsql;

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• Equivalents to Z80 DJNZ instruction on other architectures?

  - by Justin Ethier

  First a little background. The z80 CPU has an instruction called DJNZ which can be used in a similar manner as a for loop. Basically DJNZ decrements the B register and jumps to a label if not zero. For example: ld b,96 ; erase all of the line disp_version_erase_loop: call _vputblank ; erase pixels at cursor (uses b reg) djnz disp_version_erase_loop ; loop Of course you can do the same thing using regular comparison and jump instructions, but often it is handy to use the single instruction. With that out of the way, my question is, do other CPU architectures include a similar control instruction?

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• A question about "empty" lists in Python

  - by bitrex

  I've started teaching myself Python, and as an exercise I've set myself the task of generating lookup tables I need for another project. I need to generate a list of 256 elements in which each element is the value of math.sin(2pi/256). The problem is I don't know how to generate a list initialized to "dummy" values that I can then use a for loop to step through and assign the values of the sin function. Using list[] seems to create an "empty" list, but with no elements so I get a "list assignment index out of range" error in the loop. Is there a way to this other than explicitly creating a list declaration containing 256 elements all with "0" as a value? Thanks!

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• Regarding UNIX Shell Script

  - by arav

  When there is no files inside the folder the below script goes inside the for loop. Not sure what i can modify so that it doesn't go inside the for loop. Also when there is no files inside the directory exit status should be success. Wrapper script checks the exit status of the below script FILESRAW ="/exp/test1/folder" . for fspec in "$FILESRAW"/* ; do echo "$fspec" if [[ -f ${fspec} ]] ; then ..... processing logic else ... processing logic fi done

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• wxWidgets: How to initialize wxApp without using macros and without entering the main application l

  - by m_pGladiator

  We need to write unit tests for a wxWidgets application using Google Test Framework. The problem is that wxWidgets uses the macro IMPLEMENT_APP(MyApp) to initialize and enter the application main loop. This macro creates several functions including int main(). The google test framework also uses macro definitions for each test. One of the problems is that it is not possible to call the wxWidgets macro from within the test macro, because the first one creates functions.. So, we found that we could replace the macro with the following code: wxApp* pApp = new MyApp(); wxApp::SetInstance(pApp); wxEntry(argc, argv); That's a good replacement, but wxEntry() call enters the original application loop. If we don't call wxEntry() there are still some parts of the application not initialized. The question is how to initialize everything required for a wxApp to run, without actually running it, so we are able to unit test portions of it?

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• jQuery animate() - multiple selectors and variables, a unique animate() call

  - by ozke

  Hi guys, I am resizing several divs in a loop with animate() in jQuery. At the same time I am moving (left property, no resizing at all) the div where they are contained. Problem is, despite they have same duration the resize animate calls finish before the move call. They are out of sync. Is there any way of creating a list of selectors and its properties and then run a unique animate() call? Or, is there any alternative to make multiple animations happen at the same time? I've seen there's a property called step that happens every time animate loop happens but, again, each animate() call has it's own step call. Thanks in advance :)

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• In SQL Server can I insert multiple nodes into XML from a table?

  - by tpower

  I want to generate some XML in a stored procedure based on data in a table. The following insert allows me to add many nodes but they have to be hard-coded or use variables (sql:variable): SET @MyXml.modify(' insert <myNode> {sql:variable("@MyVariable")} </myNode> into (/root[1]) ') So I could loop through each record in my table, put the values I need into variables and execute the above statement. But is there a way I can do this by just combining with a select statement and avoiding the loop? Edit I have used SELECT FOR XML to do similar stuff before but I always find it hard to read when working with a hierarchy of data from multiple tables. I was hoping there would be something using the modify where the XML generated is more explicit and more controllable.

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• Is there built-in method to tell if specific URL belongs to this SPWeb or other SPWeb?

  - by Janis Veinbergs

  Hello. I have a list of urls (content type usage url's). Now, content types are deployed across web's. I need to loop those content types and do some actions in each list, but opening new SPWeb instance every loop is too resource intensive. Is there built-in method to tell me if this URL belongs to certain SPWeb object? Example: SPWeb's may be http://server/web1 http://server/web2 http://server/web2/subweb1 http://server/web2/subweb2 With content type usage links like: /web2/Pages /web2/Lists/Tasks /web2/Lists/Documents /web2/subweb1/Lists/Tasks ... As you can see, for first 3 usages i don't need to open up new SPWeb

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• How do i create a table dynamically with dynamic datatype from a PL/SQL procedure

  - by Swapna

  CREATE OR REPLACE PROCEDURE p_create_dynamic_table IS v_qry_str VARCHAR2 (100); v_data_type VARCHAR2 (30); BEGIN SELECT data_type || '(' || data_length || ')' INTO v_data_type FROM all_tab_columns WHERE table_name = 'TEST1' AND column_name = 'ZIP'; FOR sql_stmt IN (SELECT * FROM test1 WHERE zip IS NOT NULL) LOOP IF v_qry_str IS NOT NULL THEN v_qry_str := v_qry_str || ',' || 'zip_' || sql_stmt.zip || ' ' || v_data_type; ELSE v_qry_str := 'zip_' || sql_stmt.zip || ' ' || v_data_type; END IF; END LOOP; IF v_qry_str IS NOT NULL THEN v_qry_str := 'create table test2 ( ' || v_qry_str || ' )'; END IF; EXECUTE IMMEDIATE v_qry_str; COMMIT; END p_create_dynamic_table; Is there any better way of doing this ?

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