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  • How are lists implemented in Haskell (GHC)?

    - by eman
    I was just curious about some exact implementation details of lists in Haskell (GHC-specific answers are fine)--are they naive linked lists, or do they have any special optimizations? More specifically: Do length and (!!) (for instance) have to iterate through the list? If so, are their values cached in any way (i.e., if I call length twice, will it have to iterate both times)? Does access to the back of the list involve iterating through the whole list? Are infinite lists and list comprehensions memoized? (i.e., for fib = 1:1:zipWith (+) fib (tail fib), will each value be computed recursively, or will it rely on the previous computed value?) Any other interesting implementation details would be much appreciated. Thanks in advance!

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  • How can this C and PHP programmer learn Ruby and Rails?

    - by Winston
    I came from a C, php and bash background, it was easy to learn because they all have the same C structure, which I can associate with what I already know. Then 2 years ago I learned Python and I learned it quite well, Python is easier for me to learn than Ruby. Then since last year, I was trying to learn Ruby, then Rails, and I admit, until now I still couldn't get it, the irony is that those are branded as easy to learn, but for a seasoned programmer like me, I just couldn't associate it with what I learned before, I have 2 books on both Ruby and Rails, and when I'm reading it nothing is absorbed into my mind, and I'm close to giving up... In ruby, I'm having a hard time grasping the concepts of blocks, and why there's @variables that can be accessed by other functions, and what does $variable and :variable do? And in Rails, why there's function like this_is_another_function_that_do_this, so thus ruby, is it just a naming convention or it's auto-generated with thisvariable _can_do_this_function. I'm still puzzled that where all those magic concepts and things came from? And now, 1 year of trying and absorbing, but still no progress... Edit: To summarize: How can I learn about blocks, and how can it be related to concepts from PHP/C? Variables, what does does it mean when a variable is prefixed with: @ $ : "Magic concepts", suchs as rails declarations of Records, what happens behind the scenes when I write has_one X OK so, bear with me with my confusion, at least I'm honest with myself, and it's over a year now since I first trying to learn ruby, and I'm not getting younger.. so I learned this in Bash/C/PHP solve_problem($problem) { if [ -e $problem == "trivial" ]; then write_solution(); else breakdown_problem_into_N_subproblems(\; define_relationship_between_subproblems; for i in $( command $each_subproblem ); do solve_problem $i done fi } write_solution(problem) { some_solution=$(command <parameters> "input" | command); command | command $some_solution > output_solved_problem_to_file } breakdown_problem_into_N_subproblems($problems) { for i in $problems; do command $i | command > i_can_output_a_file_right_away done } define_relationship_between_subproblems($problems) { if [ -e $problem == "relationship" ]; then relationship=$(command; command | command; command;) elsif [ -e $problem == "another_relationship" ]; relationship=$(command; command | command; command;) fi } In C/PHP is something like this solve_problem(problem) { if (problem == trivial) write_solution; else { breakdown_problem_into_N_subproblems; define_relationship_between_subproblems; for (each_subproblem) solve_problems(subproblem); } } And now, I just couldn't connect the dots with Ruby, |b|{ blocks }, using @variables, :variables, and variables_with_this_things..

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  • Drawing the call stack in a recursive method

    - by Shaza
    Hey, I want to draw the call stack for any recursive method, so I've created a schema like this, recursiveMethod(){ //Break recursion condition if(){ // Add value here to the return values' list- No drawing return } else{ //Draw stack with the value which will be pushed to the stack here variable <- recursiveMethod() //Clear the drawing which represents the poped value from the stack here return variable }} Notes: This schema can draw recursive methods with n recursive call by making the recursive calls in a separate return statements. returnValues list, is a list which save all the return values, just for viewing issues. What do you think of this? any suggestions are extremely welcomed.

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  • HTTP request, strange socket behavoir

    - by hoodoos
    I expirience strange behavior when doing HTTP requests through sockets, here the request: POST https://test.com:443/service/XMLSelect HTTP/1.1 Content-Length: 10926 Host: test.com User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 1.0.3705) Authorization: Basic XXX SOAPAction: http://test.com/SubmitXml Later on there goes body of my request with given content length. After that I recive something like: HTTP/1.1 200 OK Server: Apache-Coyote/1.1 Content-Type: text/xml;charset=utf-8 Transfer-Encoding: chunked Date: Tue, 30 Mar 2010 06:13:52 GMT So everything seem to be fine here. I read all contents from network stream and successfuly recieve response. But my socket which I'm doing polling on switches it's modes like that: write ( i write headers and request here ) read ( after headers sent i begin to recieve response ) write ( STRANGE BEHAVIOUR HERE. WHY? here i send nothing really ) read ( here it switches to read back again ) last two steps can repeat several times. So I want to ask what leads for socket's mode change? And in this case it's not a big problem, but when I use gzip compression in my request ( no idea how it's related ) and ask server to send gzipped response to me like this: POST https://test.com:443/service/XMLSelect HTTP/1.1 Content-Length: 1076 Accept-Encoding: gzip Content-Encoding: gzip Host: test.com User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 1.0.3705) Authorization: Basic XXX SOAPAction: http://test.com/SubmitXml I recieve response like that: HTTP/1.1 200 OK Server: Apache-Coyote/1.1 Content-Encoding: gzip Content-Type: text/xml;charset=utf-8 Transfer-Encoding: chunked Date: Tue, 30 Mar 2010 07:26:33 GMT 2000 ? I recieve a chunk size and GZIP header, it's all okay. And here's what is happening with my poor little socket meanwhile: write ( i write headers and request here ) read ( after headers sent i begin to recieve response ) write ( STRANGE BEHAVIOUR HERE. And it finally sits here forever waiting for me to send something! But if i refer to HTTP I don't have to send anything more! ) What can it be related to? What it wants me to send? Is it remote web server's problem or do I miss something? PS All actual service references and login/passwords replaced with fake ones :)

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  • problem with two .NET threads and hardware access

    - by mack369
    I'm creating an application which communicates with the device via FT2232H USB/RS232 converter. For communication I'm using FTD2XX_NET.dll library from FTDI website. I'm using two threads: first thread continuously reads data from the device the second thread is the main thread of the Windows Form Application I've got a problem when I'm trying to write any data to the device while the receiver's thread is running. The main thread simply hangs up on ftdiDevice.Write function. I tried to synchronize both threads so that only one thread can use Read/Write function at the same time, but it didn't help. Below code responsible for the communication. Note that following functions are methods of FtdiPort class. Receiver's thread private void receiverLoop() { if (this.DataReceivedHandler == null) { throw new BackendException("dataReceived delegate is not set"); } FTDI.FT_STATUS ftStatus = FTDI.FT_STATUS.FT_OK; byte[] readBytes = new byte[this.ReadBufferSize]; while (true) { lock (FtdiPort.threadLocker) { UInt32 numBytesRead = 0; ftStatus = ftdiDevice.Read(readBytes, this.ReadBufferSize, ref numBytesRead); if (ftStatus == FTDI.FT_STATUS.FT_OK) { this.DataReceivedHandler(readBytes, numBytesRead); } else { Trace.WriteLine(String.Format("Couldn't read data from ftdi: status {0}", ftStatus)); Thread.Sleep(10); } } Thread.Sleep(this.RXThreadDelay); } } Write function called from main thread public void Write(byte[] data, int length) { if (this.IsOpened) { uint i = 0; lock (FtdiPort.threadLocker) { this.ftdiDevice.Write(data, length, ref i); } Thread.Sleep(1); if (i != (int)length) { throw new BackendException("Couldnt send all data"); } } else { throw new BackendException("Port is closed"); } } Object used to synchronize two threads static Object threadLocker = new Object(); Method that starts the receiver's thread private void startReceiver() { if (this.DataReceivedHandler == null) { return; } if (this.IsOpened == false) { throw new BackendException("Trying to start listening for raw data while disconnected"); } this.receiverThread = new Thread(this.receiverLoop); //this.receiverThread.Name = "protocolListener"; this.receiverThread.IsBackground = true; this.receiverThread.Start(); } The ftdiDevice.Write function doesn't hang up if I comment following line: ftStatus = ftdiDevice.Read(readBytes, this.ReadBufferSize, ref numBytesRead);

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  • How to download images in playframework jobs?

    - by MrROY
    I have a playframework Job class like this: public class ImageDownloader extends Job { private String[] urls; private String dir; public ImageDownloader(){} public ImageDownloader(String[] urls,String dir){ this.urls = urls; this.dir = dir; } @Override public void doJob() throws Exception { if(urls!=null && urls.length > 0){ for (int i = 0; i < urls.length; i++) { String url = urls[i]; //Dowloading } } } } Play(1.2.4) has lots of amazing tools to make things easy. So i wonder whether there's a way to make the downloading easy and beautiful in play ?

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  • To use AES with 256 bits in inbuild java 1.4 api.

    - by sahil garg
    I am able to encrypt with AES 128 but with more key length it fails. code using AES 128 is as below. import java.security.*; import javax.crypto.*; import javax.crypto.spec.*; import java.io.*; /** * This program generates a AES key, retrieves its raw bytes, and * then reinstantiates a AES key from the key bytes. * The reinstantiated key is used to initialize a AES cipher for * encryption and decryption. */ public class AES { /** * Turns array of bytes into string * * @param buf Array of bytes to convert to hex string * @return Generated hex string */ public static String asHex (byte buf[]) { StringBuffer strbuf = new StringBuffer(buf.length * 2); int i; for (i = 0; i < buf.length; i++) { if (((int) buf[i] & 0xff) < 0x10) strbuf.append("0"); strbuf.append(Long.toString((int) buf[i] & 0xff, 16)); } return strbuf.toString(); } public static void main(String[] args) throws Exception { String message="This is just an example"; // Get the KeyGenerator KeyGenerator kgen = KeyGenerator.getInstance("AES"); kgen.init(128); // 192 and 256 bits may not be available // Generate the secret key specs. SecretKey skey = kgen.generateKey(); byte[] raw = skey.getEncoded(); SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES"); // Instantiate the cipher Cipher cipher = Cipher.getInstance("AES"); cipher.init(Cipher.ENCRYPT_MODE, skeySpec); byte[] encrypted =cipher.doFinal("welcome".getBytes()); System.out.println("encrypted string: " + asHex(encrypted)); cipher.init(Cipher.DECRYPT_MODE, skeySpec); byte[] original = cipher.doFinal(encrypted); String originalString = new String(original); System.out.println("Original string: " + originalString + " " + asHex(original)); } }

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  • How to transform phrases and words into MD5 hash?

    - by brilliant
    Can anyone, please, explain to me how to transform a phrase like "I want to buy some milk" into MD5? I read Wikipedia article on MD5, but the explanation given there is beyond my comprehension: "MD5 processes a variable-length message into a fixed-length output of 128 bits. The input message is broken up into chunks of 512-bit blocks (sixteen 32-bit little endian integers)" "sixteen 32-bit little endian integers" is already hard for me. I checked the article on little endians and didn't understand a bit. However, the examples of some phrases and their MD5 hashes are very nice: MD5("The quick brown fox jumps over the lazy dog") = 9e107d9d372bb6826bd81d3542a419d6 MD5("The quick brown fox jumps over the lazy dog.") = e4d909c290d0fb1ca068ffaddf22cbd0 Can anyone, please, explain to me how this MD5 algorithm works on some very simple example? And also, perhaps you know some software or a code that would transform phrases into their MD5. If yes, please, let me know.

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  • Is this a cache problem? (JQUERY)

    - by Scarface
    Hey guys quick question. I have this code that brings in data from a php script and it works fine some of the time. However, once in a while the information will not appear at all in opera if I keep refreshing. About Is every 3 refreshes. It seems to be fine in firefox. Is this a cache problem and can it be fixed? Thanks in advance for any assistance. $.getJSON(files+"comments.php?action=view&load=initial&topic_id="+topic_id+"&t=" + (new Date()), function(json) { if(json.length) { for(i=0; i < json.length; i++) { $('#comment-list').prepend(prepare(json[i])); $('#list-' + count).fadeIn(1500); } } });

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  • C-array to NSData and back

    - by Thor Frølich
    I'm attempting to save a c-style array of Vertex3D structs to an NSData object and get them back when reloading the app: NSData *vert = [NSData dataWithBytes:&vertices length:(sizeof(Vertex3D) * NUM_OF_VERTICES)]; This data is then saved and attempted to be read back into my c-array thusly: vertices = malloc(sizeof(Vertex3D) * NUM_OF_VERTICES); [vert getBytes:&vertices length:(sizeof(Vertex3D) * NUM_OF_VERTICES)]; The above results in “EXC_BAD_ACCESS” followed by: malloc: * error for object 0x48423c0: pointer being freed was not allocated I'm very new to programming so there's probably some fundamental memory management principle I'm unaware of. I have verified that the loaded NSData is identical to the saved one, but it's clear that the transition from c-array to NSData (and back) is not as I intended.

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  • How can I set partial text color in JTextArea

    - by ComputerJy
    I want to set color for specific lines in the text area. What I've found so far, was the following // Declarations private final DefaultStyledDocument document; private final MutableAttributeSet homeAttributeSet; private final MutableAttributeSet awayAttributeSet; // Usage in the form constructor jTextAreaLog.setDocument(document); homeAttributeSet = new SimpleAttributeSet(); StyleConstants.setForeground(homeAttributeSet, Color.blue); StyleConstants.setItalic(homeAttributeSet, true); awayAttributeSet = new SimpleAttributeSet(); StyleConstants.setForeground(awayAttributeSet, Color.red); // Setting the style of the last line final int start = jTextAreaLog.getLineStartOffset(jTextAreaLog.getLineCount() - 2); final int length = jTextAreaLog.getLineEndOffset(jTextAreaLog.getLineCount() - 1) - start; document.setCharacterAttributes(start, length, awayAttributeSet, true); But this is not working. What am I doing wrong?

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  • Debugging stored procedures, without using SSMS 2008 Debugger, or the Visual Studio debugger (output

    - by Albert
    I have a SQL Server 2005 database with some Stored Procedures (SP) that I would like to debug...essentially I would just like to check variable values at certain points throughout the SP execution. I have SSMS 2008, but when I try to use the debugger, I get an error that it can't debug SQL Server 2005 databases. And I can't use the Visual Studio debugger (by stepping into the SP via Server Explorer) because Remote Debugging is blocked by our firewall, and I'm rightfully not allowed to touch the firewall. So my question is how can I check variable values at certain points in the SP execution? Is there some way to output those values somewhere, perhaps along with some text?

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  • Most clever way to parse a Facebook OAuth 2 access token string

    - by RyOnLife
    It's a bit late, but I'm disappointed in myself for not coming up with something more elegant. Anyone have a better way to do this... When you pass an OAuth code to Facebook, it response with a query string containing access_token and expires values. access_token=121843224510409|2.V_ei_d_rbJt5iS9Jfjk8_A__.3600.1273741200-569255561|TxQrqFKhiXm40VXVE1OBUtZc3Ks.&expires=4554 Although if you request permission for offline access, there's no expires and the string looks like this: access_token=121843224510409|2.V_ei_d_rbJt5iS9Jfjk8_A__.3600.1273741200-569255561|TxQrqFKhiXm40VXVE1OBUtZc3Ks. I attempted to write a regex that would suffice for either condition. No dice. So I ended up with some really ugly Ruby: s = s.split("=") @oauth = {} if s.length == 3 @oauth[:access_token] = s[1][0, s[1].length - 8] @oauth[:expires] = s[2] else @oauth[:access_token] = s[1] end I know there must be a better way!

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  • Listing subdirectories 3 levels deep using LINQ C#

    - by paradox
    I'd like to know if there is a better alternative to my following code (preferably using LINQ) #region List and filter directories to only 3 levels deep // List all subdirectories within main directory string[] folders = Directory.GetDirectories(@"C:\pdftest\", "*" ,SearchOption.AllDirectories); List<string> subdirectories = new List<string>(); //Filter away all main directories, now we are left with subdirectories 3 levels deep for (int i = 0; i<folders.Length; i++) { int occurences = folders[i].Split('\\').Length-1; if (occurences==4) subdirectories.Add(folders[i]); } #endregion

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  • Allocate constant memory

    - by Vlad
    I'm trying to set my simulation params in constant memory but without luck (CUDA.NET). cudaMemcpyToSymbol function returns cudaErrorInvalidSymbol. The first parameter in cudaMemcpyToSymbol is string... Is it symbol name? actualy I don't understand how it could be resolved. Any help appreciated. //init, load .cubin float[] arr = new float[1]; arr[0] = 0.0f; int size = Marshal.SizeOf(arr[0]) * arr.Length; IntPtr ptr = Marshal.AllocHGlobal(size); Marshal.Copy(arr, 0, ptr, arr.Length); var error = CUDARuntime.cudaMemcpyToSymbol("param", ptr, 4, 0, cudaMemcpyKind.cudaMemcpyHostToDevice); my .cu file contain __constant__ float param;

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  • How to make and use first object in Objective C to store sender tag

    - by dbonneville
    I started with a sample program that simply sets up a UIView with some buttons on it. Works great. I want to access the sender tag from each button and save it. My first thought was to save it to a global variable but I couldn't get it to work right. I thought the best way would be to create an object with one property and synthesize it so I can get or set it as needed. First, I created GlobalGem.h: #import <Foundation/Foundation.h> @interface GlobalGem : NSObject { int gemTag; } @property int gemTag; -(void) print; @end Then I created GlobalGem.m: #import "GlobalGem.h" @implementation GlobalGem @synthesize gemTag; -(void) print { NSLog(@"gemTag value is %i", gemTag); } @end The sample code I worked from doesn't do anything I can see in "main" where the program initializes. They just have their methods and are set up to handle IBOutlet actions. I want to use this object in the IBOutlet methods. But I don't know where to create the object. In the viewDidLoad, I tried this: GlobalGem *aGem = [[GlobalGem alloc]init]; [aGem print]; I added reference to the .h file of course. The print method works. In the nslog I get "gemTag value is 0". But now I want to use the instance aGem in some of the IBOutlet actions. For instance, if I put this same method in one of the outlet actions like this: - (IBAction)touchButton:(id)sender { [aGem print]; } ...I get a build error saying that "aGem is undeclared". Yes, I'm new to objective c and am very confused. Is the instance I created, aGem, in the viewDidLoad not accessible outside of that method? How would I create an instance of a Class that I can store a variable value that any of the IBOutlet methods can access? All the buttons need to be able to store their sender tag in the instance aGem and I'm stuck. As I mentioned earlier, I was able to write the sender tag to a global variable I declared in the UIView .h file that came with the program, but I ran into issues using it. Where am I off?

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  • Hiding privates from Javascript Intellisense

    - by Robert Koritnik
    Is it possible to hide certain functions/fields from displaying in javascript intellisense drop down list in Visual Studio 2008? Either by javascript documentaion XML of by naming privates in a certain way? I've seen <private /> in jquery vsdoc file that implies exactly this behaviour, but doesn't meet my expectations { __hiddenField: 0, /// <private /> increment: function(){ /// <summary>Increments a private variable</summary> __hiddenField++; } } But since fields can't contain documentation (because they have no body) they have to be documented at the top. But still doesn't work: { /// <field name="__hiddenField" type="Number" private="true">PRIVATE USE</field> __hiddenField: 0, increment: function(){ /// <summary>Increments a private variable</summary> __hiddenField++; } } Impossible is a perfectly possible answer and will be accepted if you have the knowledge that it's actually not possible.

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  • casting raw strings python

    - by dave
    in python, given a variable which holds a string is there a quick way to cast that into another raw string variable? the following code should illustrate what im after... def checkEqual(x, y): print True if x==y else False line1 = "hurr..\n..durr" line2 = r"hurr..\n..durr" line3 = "%r"%line1 print "%s \n\n%s \n\n%s \n" % (line1, line2, line3) checkEqual(line2, line3) #outputs False checkEqual(line2, line3[1:-1]) #outputs True The closest I have found so far is the %r formatting flag which seems to return a raw string albeit within single quote marks. Is there any easier way to do this like a line3 = raw(line1) kind of thing?

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  • Java: initialization problem with private-final-int-value and empty constructor

    - by HH
    $ javac InitInt.java InitInt.java:7: variable right might not have been initialized InitInt(){} ^ 1 error $ cat InitInt.java import java.util.*; import java.io.*; public class InitInt { private final int right; InitInt(){} public static void main(String[] args) { // I don't want to assign any value. // just initialize it, how? InitInt test = new InitInt(); System.out.println(test.getRight()); // later assiging a value } public int getRight(){return right;} } Initialization problem with Constructor InitInt{ // Still the error, "may not be initialized" // How to initialise it? if(snippetBuilder.length()>(charwisePos+25)){ right=charwisePos+25; }else{ right=snippetBuilder.length()-1; } }

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  • Iterate over framesets with XPath expression in JavaScript?

    - by Derek Mahar
    Why does the following JavaScript, when run in Firefox 3.6.3, delete all FRAMESET elements in a document, but the similar script that instead uses an XPath expression to select the FRAMESET elements, does not? Is document.evaluate() simply unable to match FRAMESET elements? Is there an error in the XPath expression? Is there some other error? Select all FRAMESET elements using method document.getElementsByTagName() (succeeds): var framesets = document.getElementsByTagName('frameset'); for (var i = 0; i < framesets.length; i++) { framesets[i].parentNode.removeChild(framesets[i]); } Select all FRAMESET elements using an XPath expression (fails): var framesets = document.evaluate("//frameset", document, null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null); for (var i = 0; i < framesets.length; i++) { framesets[i].parentNode.removeChild(framesets[i]); }

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  • FileUtils.mv adding linebreaks in Windows

    - by Lowgain
    I am streaming wav data from a flash application. If I get the data and do the following: f = File.open('c:/test.wav') f << wav_data.pack('c'*wav_data.length) f.close The wav file works perfectly. If I do this: f = Tempfile.new('test.wav') f << wav_data.pack('c'*wav_data.length) f.close FileUtils.mv(f.path, 'c:/') The file is there, but sounds all garbled. Checking in a hex editor shows that everywhere the working file had an 0A (or \n), the garbled version had 0D0A (or \r\n) I am using this in conjuction with rails+paperclip, and am going to be using a combination of Heroku and S3 for the live app, so I am hoping this problem will solve itself, but I'd like to get this working on my local machine for the time being. Does anybody know of any reason FileUtils.mv would be doing this, and if there is a way to change its behaviour?

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  • Add UITabBar Control!

    - by Taimur Hamza
    hi, I m stuck in a really simple problem. And i m afraid my question might annoy some people. The problem i am facing in short is that i want to add UITabBar Control to my iphone application other than the main screen. Let me explain, I have done everything successfully Added UItabbar control from IB in the main window's xib, added a variable at the back end , associated it by dragging the line. Also added a UIWindow variable and wrote these lines . [window addSubview:tabBarController.view]; [window makeKeyAndVisible]; when i launch the application a blank window appears and tab bar shows on its bottom. But the problem i dont want to add it to a particular window which is inside my app. Its no the first screen of my app. Its actually the 3rd screen of my app. Can anybody help ? thanks Taimur

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  • Java variadic function parameters

    - by Amir Rachum
    Hi, I have a function that accepts a variable number of parameters: foo (Class... types); In which I get a certain number of class types. Next, I want to have a function bar( ?? ) That will accepts a variable number of parameters as well, and be able to verify that the variables are the same number (that's easy) and of the same types (the hard part) as was specified in foo. How can I do that? Edit: to clarify, a call could be: foo (String.class, Int.class); bar ("aaa", 32); // OK! bar (3); // ERROR! bar ("aa" , "bb"); //ERROR! Also, foo and bar are methods of the same class.

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  • Faster Matrix Multiplication in C#

    - by Kyle Lahnakoski
    I have as small c# project that involves matrices. I am processing large amounts of data by splitting it into n-length chunks, treating the chucks as vectors, and multiplying by a Vandermonde** matrix. The problem is, depending on the conditions, the size of the chucks and corresponding Vandermonde** matrix can vary. I have a general solution which is easy to read, but way too slow: public byte[] addBlockRedundancy(byte[] data) { if (data.Length!=numGood) D.error("Expecting data to be just "+numGood+" bytes long"); aMatrix d=aMatrix.newColumnMatrix(this.mod, data); var r=vandermonde.multiplyBy(d); return r.ToByteArray(); }//method This can process about 1/4 megabytes per second on my i5 U470 @ 1.33GHz. I can make this faster by manually inlining the matrix multiplication: int o=0; int d=0; for (d=0; d<data.Length-numGood; d+=numGood) { for (int r=0; r<numGood+numRedundant; r++) { Byte value=0; for (int c=0; c<numGood; c++) { value=mod.Add(value, mod.Multiply(vandermonde.get(r, c), data[d+c])); }//for output[r][o]=value; }//for o++; }//for This can process about 1 meg a second. (Please note the "mod" is performing operations over GF(2^8) modulo my favorite irreducible polynomial.) I know this can get a lot faster: After all, the Vandermonde** matrix is mostly zeros. I should be able to make a routine, or find a routine, that can take my matrix and return a optimized method which will effectively multiply vectors by the given matrix, but faster. Then, when I give this routine a 5x5 Vandermonde matrix (the identity matrix), there is simply no arithmetic to perform, and the original data is just copied. ** Please note: What I use the term "Vandermonde", I actually mean an Identity matrix with some number of rows from the Vandermonde matrix appended (see comments). This matrix is wonderful because of all the zeros, and because if you remove enough rows (of your choosing) to make it square, it is an invertible matrix. And, of course, I would like to use this same routine to convert any one of those inverted matrices into an optimized series of instructions. How can I make this matrix multiplication faster? Thanks! (edited to correct my mistake with Vandermonde matrix)

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  • how to show attached files on a TMS WebGrid ???

    - by ahmed
    hi, i have a TMS WebGrid , I would like to attach some files ad show them on a Tms WebGrid. How can I do that in vb.net ? For now I am simply attaching like this on a attach file button ?? If Len(FileUpload1.PostedFile.FileName) > 5 Then length = FileUpload1.PostedFile.InputStream.Length() My_Img_Path = "Attachments/" k_upload_dir = "~/Attachments/" virtualPath = k_upload_dir + my_img_srno.ToString + Path.GetFileName(FileUpload1.PostedFile.FileName) My_Img_Path = My_Img_Path + my_img_srno.ToString + Path.GetFileName(FileUpload1.PostedFile.FileName) phyiscalPath = Server.MapPath(virtualPath) FileUpload1.PostedFile.SaveAs(phyiscalPath) my_html_code = "" lbl_AttahcmnetStatus.Text = "Sucessfully file attached..." end if

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