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  • Delay in the implementation of text change in Statusbar control

    - by ehsan zeynali
    I have a function a time consuming operation that is done I want to start and end operations appear to be user (By statusbar control) But when performed function, both text executed at the end of function. (user can not sees "Start Operation ...") What solution do you recommend to me? private void btnUpdateDataBase_Click(object sender, RoutedEventArgs e) { TextBlockStatus.Text = "Start Operation ..."; //Time consuming operation TextBlockStatus.Text = "End Operation ..."; }

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  • Fibonnaci Sequence fast implementation

    - by user2947615
    I have written this function in Scala to calculate the fibonacci number given a particular index n: def fibonacci(n: Long): Long = { if(n <= 1) n else fibonacci(n - 1) + fibonacci(n - 2) } However it is not efficient when calculating with large indexes. Therefore I need to implement a function using a tuple and this function should return two consecutive values as the result. Can somebody give me any hints about this? I have never used Scala before. Thanks!

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  • Memcached getDelayed alternative implementation

    - by iBobo
    I would like to use getDelayed on the PHP Memcached extension but I think it's not implemented in the right way. Right now you ask for some keys and then retrieve all of them with fetch() and fetchAll(). But imagine a scenario where I need to retrieve 15 keys used in different parts of the page which I don't know in advance, but I can ask the various objects to give me the list. What I want is give the Memcached instance this list (each component would give its part) then later when I need them retrieve from the instance, but not all of them at once: each component would take the one it needs. Basically if I were to implement this I would prohibit using getDelayed alone and implement a bookGet($keys) method where you would add the keys to book (which actually calls getDelayed), and redefine get to handle these three cases: key is booked and retrieved - return the value; key is booked but not retrieved - go and force the fetch of the booked keys and return the correct value; key not booked - do a normal lookup. I want to know if this makes sense, your thoughts on the subject and if someone already implemented this or maybe PECL Memcached already works this way and actually the documentation doesn't explain it correctly.

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  • Adapting pseudocode to java implementation for finding the longest word in a trie

    - by user1766888
    Referring to this question I asked: How to find the longest word in a trie? I'm having trouble implementing the pseudocode given in the answer. findLongest(trie): //first do a BFS and find the "last node" queue <- [] queue.add(trie.root) last <- nil map <- empty map while (not queue.empty()): curr <- queue.pop() for each son of curr: queue.add(son) map.put(son,curr) //marking curr as the parent of son last <- curr //in here, last indicate the leaf of the longest word //Now, go up the trie and find the actual path/string curr <- last str = "" while (curr != nil): str = curr + str //we go from end to start curr = map.get(curr) return str This is what I have for my method public static String longestWord (DTN d) { Queue<DTN> holding = new ArrayQueue<DTN>(); holding.add(d); DTN last = null; Map<DTN,DTN> test = new ArrayMap<DTN,DTN>(); DTN curr; while (!holding.isEmpty()) { curr = holding.remove(); for (Map.Entry<String, DTN> e : curr.children.entries()) { holding.add(curr.children.get(e)); test.put(curr.children.get(e), curr); } last = curr; } curr = last; String str = ""; while (curr != null) { str = curr + str; curr = test.get(curr); } return str; } I'm getting a NullPointerException at: for (Map.Entry<String, DTN> e : curr.children.entries()) How can I find and fix the cause of the NullPointerException of the method so that it returns the longest word in a trie?

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  • question about a macro in Linux Kernel List implementation

    - by holydiver
    I generally have ignored using macros while writing in C but I think I know fundamentals about them. While i was reading the source code of list in linux kernel, i saw something like that: #define LIST_HEAD_INIT(name) { &(name), &(name) } #define LIST_HEAD(name) \ struct list_head name = LIST_HEAD_INIT(name) (You can access the remaining part of the code from here.) I didn't understand the function of ampersands(I don't think they are the address of operands here) in LIST_HEAD_INIT and so the use of LIST_HEAD_INIT in the code. I'd appreciate if someone can enlighten me.

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  • Another thread safe queue implementation

    - by jensph
    I have a class, Queue, that I tried to make thread safe. It has these three member variables: std::queue<T> m_queue; pthread_mutex_t m_mutex; pthread_cond_t m_condition; and a push and pop implemented as: template<class T> void Queue<T>::push(T value) { pthread_mutex_lock( &m_mutex ); m_queue.push(value); if( !m_queue.empty() ) { pthread_cond_signal( &m_condition ); } pthread_mutex_unlock( &m_mutex ); } template<class T> bool Queue<T>::pop(T& value, bool block) { bool rtn = false; pthread_mutex_lock( &m_mutex ); if( block ) { while( m_queue.empty() ) { pthread_cond_wait( &m_condition, &m_mutex ); } } if( !m_queue.empty() ) { value = m_queue.front(); m_queue.pop(); rtn = true; } pthread_mutex_unlock( &m_mutex ); return rtn; } Unfortunately there are occasional issues that may be the fault of this code. That is, there are two threads and sometimes thread 1 never comes out of push() and at other times thread 2 never comes out of pop() (the block parameter is true) though the queue isn't empty. I understand there are other implementations available, but I'd like to try to fix this code, if needed. Anyone see any issues? The constructor has the appropriate initializations: Queue() { pthread_mutex_init( &mMutex, NULL ); pthread_cond_init( &mCondition, NULL ); } and the destructor, the corresponding 'destroy' calls.

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  • Password Hash Implementation

    - by oyerli
    I am developing a new application using Symfony. I want to store the passwords hashed, so I overridded the save method in my User model: public function save(Doctrine_Connection $conn = null) { $this->setUserPassword( md5($this->getUserPassword()) ); return parent::save($conn); } This works good when a new user created. However, this causes problems when we edit a user without changing his password. This causes Doctrine to hash the already hashed password. So, I need to check that whether the UserPassword is modified in this DoctrineRecord instance. How can I manage to do that?

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  • TCP/IP Implementation General Questions

    - by user2971023
    I've implemented the concepts shown here; http://wiki.unity3d.com/index.php/Simple_TCP/IP_Client_-_Server outside of unity and it works. (though i had to create the TCPIPServerApp from scratch as i could not find the base project anywhere). I have some general questions on how to use tcp/ip properly however. I've done some research on tcp/ip itself but I'm still a little confused. It seems like using the method above doesn't guarantee that I'll see the message (res). It just checks on every update to see if there is a different message in res. What if multiple messages are sent and the program lags or something, will i miss the earlier packet(s)? Should i instead do an array so it stores the last X messages? How do i know the data was received? Do I need to add a message id and build in my own ack into the data? Should i check to see if the port is in use before setting up a connection? Sorry for all the questions. This is all new to me but I enjoy this very much! ... Below already answered By Anton, Thanks It sounds like tcp uses its own packet numbering to ensure the packets end up in the right order on the other side. What if a packet is missed, are the subsequent packets thrown away? Or is this numbering and packet ordering, only for handling data that is broken out into multiple packets? TCP will automatically break the data into multiple packets if necessary right?

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  • Twisted Matrix and telnet server implementation

    - by ypercube
    I have a project which is essentially a game server where users connect and send text commands via telnet. The code is in C and really old and unmodular and has several bugs and missing features. The main function alone is half the code. I came to the conclusion that rewriting it in TwistedMachine could actually result in faster completement, besides other benefits. So, here is the questions: What packages and modules I should use? I see a "telnet" module inside "protocols" package. I also see "cronch" package with "ssh" and another "telnet" module. I'm a complete novice regarding Python.

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  • Vacancy Tracking Algorithm implementation in C++

    - by Dave
    I'm trying to use the vacancy tracking algorithm to perform transposition of multidimensional arrays in C++. The arrays come as void pointers so I'm using address manipulation to perform the copies. Basically, there is an algorithm that starts with an offset and works its way through the whole 1-d representation of the array like swiss cheese, knocking out other offsets until it gets back to the original one. Then, you have to start at the next, untouched offset and do it again. You repeat until all offsets have been touched. Right now, I'm using a std::set to just fill up all possible offsets (0 up to the multiplicative fold of the dimensions of the array). Then, as I go through the algorithm, I erase from the set. I figure this would be fastest because I need to randomly access offsets in the tree/set and delete them. Then I need to quickly find the next untouched/undeleted offset. First of all, filling up the set is very slow and it seems like there must be a better way. It's individually calling new[] for every insert. So if I have 5 million offsets, there's 5 million news, plus re-balancing the tree constantly which as you know is not fast for a pre-sorted list. Second, deleting is slow as well. Third, assuming 4-byte data types like int and float, I'm using up actually the same amount of memory as the array itself to store this list of untouched offsets. Fourth, determining if there are any untouched offsets and getting one of them is fast -- a good thing. Does anyone have suggestions for any of these issues?

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  • Android Login - Best implementation

    - by perdian
    Hi everybody, I'm planning to implement an Android application that requires a login screen. If the user opens the activity something like this should happen: If user is logged in, goto 3 If user is not logged in open the login screen and perfom login Show my application content So, what's the "correct" way of implementing a login? Implement a StartActivity that perfoms the check if the user is logged in, implement a LoginActivity that implements the logging and an ApplicationActivity that actually implements the application logics? Implement just one Activity and handle the login by using multiple views which I show according to the application state? Are there any examples or tutorials for this scenario?

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  • best practice for Jquery plugin implementation and resource locations

    - by ptutt
    This is probably a very basic question, but I seem to have issues plugging in jquery plug-ins. The issue seems to be around the location of the script, css and images and ensuring the css has the correct url to the images. The standard plug-in has the following folder structure (eg : JPicker) js css images My project is asp.net mvc so I have the default: scripts images content So, I try to split the jquery plugin to the appropriate folders (not sure if this is the best way?). Then I try to correct the references to images (background urls) in the css. I believe the url is relative to the page that is implementing the css file, not the location of the css file itself. Anyway, when I try the above, the plugins don't seem to work. I believe the issue lies with the images not being found. The jquery code runs without errors, so I assume that's not the problem. Any help/advice much appreciated

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  • Abstract Design Pattern implementation

    - by Pathachiever11
    I started learning design patterns a while ago (only covered facade and abstract so far, but am enjoying it). I'm looking to apply the Abstract pattern to a problem I have. The problem is: Supporting various Database systems using one abstract class and a set of methods and properties, which then the underlying concrete classes (inheriting from abstract class) would be implementing. I have created a DatabaseWrapper abstract class and have create SqlClientData and MSAccessData concrete class that inherit from the DatabaseWrapper. However, I'm still a bit confused about how the pattern goes as far as implementing these classes on the Client. Would I do the following?: DatabaseWrapper sqlClient = new SqlClientData(connectionString); This is what I saw in an example, but that is not what I'm looking for because I want to encapsulate the concrete classes; I only want the Client to use the abstract class. This is so I can support for more database systems in the future with minimal changes to the Client, and creating a new concrete class for the implementations. I'm still learning, so there might be a lot of things wrong here. Please tell me how I can encapsulate all the concrete classes, and if there is anything wrong with my approach. Many Thanks! PS: I'm very excited to get into software architecture, but still am a beginner, so take it easy on me. :)

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  • C# Client-Server implementation error on client's socket

    - by Ksice
    I'm trying to launch my client. Server already runned on the same computer. So I'm using "localhost" with GetHostEntry: IPHostEntry ipHostInfo = System.Net.Dns.GetHostEntry("localhost"); IPAddress ipAddress = ipHostInfo.AddressList[0]; IPEndPoint remoteEP = new IPEndPoint(ipAddress, Port); But I have this "no connection could be made because the target machine actively refused it" error. What is the reason? Could it be because ipHostInfo.AddressList[0] is an IPv6? How then I can accept Ipv4 address?

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  • HashMap "WriteOnce" Implementation .. need help

    - by JavaNewbie
    import java.util.*; public class HashMapExample { public static class WriteOnceMap<K, V> extends HashMap<K, V> { public V put(K key, V value) { /* WriteOnceMap is a map that does not allow changing value for a particular key. It means that put() method should throw IllegalArgumentException if the key is already assosiated with some value in the map. Please implement this method to conform to the above description of WriteOnceMap. */ } public void putAll(Map<? extends K, ? extends V> m) { /* Pleaase implement this method to conform to the description of WriteOnceMap above. It should either (1) copy all of the mappings from the specified map to this map or (2) throw IllegalArgumentException and leave this map intact if the parameter already contains some keys from this map. */ } } }

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  • perforce implementation of clearcase like "views"

    - by Pradyot
    I have read through the documentation on perforce and the "branching strategy" advice as well. One thing thats left me baffled, is how a simple concern is does not seem to adequtely adressed. When I am working on a project that touches many parts of our code base , I cannot checkin my code at the end of the day without checking into the trunk. So do I need to branch in this situation? I want to be able to have the ability to have a history of my changes in a long and hard project, so I can go back when I I make a wrong turn.. The problem with branching I see is that I will be creating copies of almost the entire codebase .. Am I missing an obvious solution here? thanks

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  • .NET List Thread-Safe Implementation Suggestion needed

    - by Bamboo
    .Net List class isn't thread safe. I hope to achieve the minimal lock needed and yet still fulfilling the requirement such that as for reading, phantom record is allowed, and for writing, they must be thread-safe so there won't be any lost updates. So I have something like public static List<string> list = new List<string>(); In Methods that have **List.Add**/**List.Remove** , I always lock to assure thread safety lock (lockHelper) { list.Add(obj); or list.Remove(obj); } In Methods that requires **List Reading** I don't care about phantom record so I go ahead to read without any locking. In this case. Return a bool by checking whether a string had been added. if (list.Count() != 0) { return list.Contains("some string") } All I did was locking write accesses, and allow read accesses to go through without any locking. Is my thread safety idea valid? I understand there is List size expansion. Will it be ok? My guess is that when a List is expanding, it may uses a temp. list. This is ok becasue the temp list size will always have a boundary, and .Net class is well implemented, ie. there shouldn't be any indexOutOfBound or circular reference problems when reading was caught in updates.

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  • Is the below thread pool implementation correct(C#3.0)

    - by Newbie
    Hi Experts, For the first time ever I have implemented thread pooling and I found it to be working. But I am not very sure about the way I have done is the appropriate way it is supposed to be. Would you people mind in spending some valuable time to check and let me know if my approach is correct or not? If you people find that the approach is incorrect , could you please help me out in writing the correct version. I have basicaly read How to use thread pool and based on what ever I have understood I have developed the below program as per my need public class Calculation { #region Private variable declaration ManualResetEvent[] factorManualResetEvent = null; #endregion public void Compute() { factorManualResetEvent = new ManualResetEvent[2]; for (int i = 0; i < 2; i++){ factorManualResetEvent[i] = new ManualResetEvent(false); ThreadPool.QueueUserWorkItem(ThreadPoolCallback, i);} //Wait for all the threads to complete WaitHandle.WaitAll(factorManualResetEvent); //Proceed with the next task(s) NEXT_TASK_TO_BE_EXECUTED(); } #region Private Methods // Wrapper method for use with thread pool. public void ThreadPoolCallback(Object threadContext) { int threadIndex = (int)threadContext; Method1(); Method2(); factorManualResetEvent[threadIndex].Set(); } private void Method1 () { //Code of method 1} private void Method2 () { //Code of method 2 } #endregion }

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  • priority queue implementation

    - by davit-datuashvili
    i have implemented priority queue and i am interested if it is correct public class priqueue { private int n,maxsize; int x[]; void swap(int i,int j){ int t=x[i]; x[i]=x[j]; x[j]=t; } public priqueue(int m){ maxsize=m; x=new int [maxsize+1]; n=0; } void insert(int t){ int i,p; x[++n]=t; for (i=n;i>1 && x[p=i/2] >x[i];i=p) swap(p,i); } public int extramin(){ int i,c; int t=x[1]; x[1]=x[n--]; for (i=1;(c=2*i)<=n;i=c){ if (c+1<=n && x[c+1]<x[c]) c++; if (x[i]<=x[c]) break; swap(c,i); } return t; } public void display(){ for (int j=0;j<x.length;j++){ System.out.println(x[j]); } } } public class priorityqueue { public static void main(String[] args) { priqueue pr=new priqueue(12); pr.insert(20); pr.insert(12); pr.insert(22); pr.insert(15); pr.insert(35); pr.insert(17); pr.insert(40); pr.insert(51); pr.insert(26); pr.insert(19); pr.insert(29); pr.insert(23); pr.extramin(); pr.display(); } } //result: 0 12 15 17 20 19 22 40 51 26 35 29 23

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  • Force the use of interface instead of concrete implementation in declaration (.NET)

    - by gammelgul
    In C++, you can do the following: class base_class { public: virtual void do_something() = 0; }; class derived_class : public base_class { private: virtual void do_something() { std::cout << "do_something() called"; } }; The derived_class overrides the method do_something() and makes it private. The effect is, that the only way to call this method is like this: base_class *object = new derived_class(); object->do_something(); If you declare the object as of type derived_class, you can't call the method because it's private: derived_class *object = new derived_class(); object->do_something(); // --> error C2248: '::derived_class::do_something' : cannot access private member declared in class '::derived_class' I think this is quite nice, because if you create an abstract class that is used as an interface, you can make sure that nobody accidentally declares a field as the concrete type, but always uses the interface class. Since in C# / .NET in general, you aren't allowed to narrow the access from public to private when overriding a method, is there a way to achieve a similar effect here?

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  • Efficient implementation of exclusive execution

    - by n0weak
    I have an ObjectManager class that is used to process payments. It is wrapped over the Order entities, so new instance has to be created when processing is required. I need to prevent the situation when several ObjectManager instances are dealing with the same order simultaneously (it happend once because of some errors on the remote payment processing center, somehow they called our callback urls twice). I'd love to get an advice how to implement it more efficiently. For now, I am thinking about something like that: public class OrderManager{ private static final CopyOnWriteArrayList<Integer> LOCKER = new CopyOnWriteArrayList<Integer>(); private static synchronized boolean tryLock(Integer key) { return LOCKER.addIfAbsent(key); } private static void releaseLock(Integer key) { LOCKER.remove(key); } public void processPayment(Integer orderId) throws Exception{ if (!tryLock(orderId)) { return; } try { //operate } finally { releaseLock(orderId); } } //remainder omitted }

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