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  • Synchronized IEnumerator<T>

    - by Dan Bryant
    I'm putting together a custom SynchronizedCollection<T> class so that I can have a synchronized Observable collection for my WPF application. The synchronization is provided via a ReaderWriterLockSlim, which, for the most part, has been easy to apply. The case I'm having trouble with is how to provide thread-safe enumeration of the collection. I've created a custom IEnumerator<T> nested class that looks like this: private class SynchronizedEnumerator : IEnumerator<T> { private SynchronizedCollection<T> _collection; private int _currentIndex; internal SynchronizedEnumerator(SynchronizedCollection<T> collection) { _collection = collection; _collection._lock.EnterReadLock(); _currentIndex = -1; } #region IEnumerator<T> Members public T Current { get; private set;} #endregion #region IDisposable Members public void Dispose() { var collection = _collection; if (collection != null) collection._lock.ExitReadLock(); _collection = null; } #endregion #region IEnumerator Members object System.Collections.IEnumerator.Current { get { return Current; } } public bool MoveNext() { var collection = _collection; if (collection == null) throw new ObjectDisposedException("SynchronizedEnumerator"); _currentIndex++; if (_currentIndex >= collection.Count) { Current = default(T); return false; } Current = collection[_currentIndex]; return true; } public void Reset() { if (_collection == null) throw new ObjectDisposedException("SynchronizedEnumerator"); _currentIndex = -1; Current = default(T); } #endregion } My concern, however, is that if the Enumerator is not Disposed, the lock will never be released. In most use cases, this is not a problem, as foreach should properly call Dispose. It could be a problem, however, if a consumer retrieves an explicit Enumerator instance. Is my only option to document the class with a caveat implementer reminding the consumer to call Dispose if using the Enumerator explicitly or is there a way to safely release the lock during finalization? I'm thinking not, since the finalizer doesn't even run on the same thread, but I was curious if there other ways to improve this. EDIT After thinking about this a bit and reading the responses (particular thanks to Hans), I've decided this is definitely a bad idea. The biggest issue actually isn't forgetting to Dispose, but rather a leisurely consumer creating deadlock while enumerating. I now only read-lock long enough to get a copy and return the enumerator for the copy.

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  • Code Golf: Evaluating Mathematical Expressions

    - by Noldorin
    Challenge Here is the challenge (of my own invention, though I wouldn't be surprised if it has previously appeared elsewhere on the web). Write a function that takes a single argument that is a string representation of a simple mathematical expression and evaluates it as a floating point value. A "simple expression" may include any of the following: positive or negative decimal numbers, +, -, *, /, (, ). Expressions use (normal) infix notation. Operators should be evaluated in the order they appear, i.e. not as in BODMAS, though brackets should be correctly observed, of course. The function should return the correct result for any possible expression of this form. However, the function does not have to handle malformed expressions (i.e. ones with bad syntax). Examples of expressions: 1 + 3 / -8 = -0.5 (No BODMAS) 2*3*4*5+99 = 219 4 * (9 - 4) / (2 * 6 - 2) + 8 = 10 1 + ((123 * 3 - 69) / 100) = 4 2.45/8.5*9.27+(5*0.0023) = 2.68... Rules I anticipate some form of "cheating"/craftiness here, so please let me forewarn against it! By cheating, I refer to the use of the eval or equivalent function in dynamic languages such as JavaScript or PHP, or equally compiling and executing code on the fly. (I think my specification of "no BODMAS" has pretty much guaranteed this however.) Apart from that, there are no restrictions. I anticipate a few Regex solutions here, but it would be nice to see more than just that. Now, I'm mainly interested in a C#/.NET solution here, but any other language would be perfectly acceptable too (in particular, F# and Python for the functional/mixed approaches). I haven't yet decided whether I'm going to accept the shortest or most ingenious solution (at least for the language) as the answer, but I would welcome any form of solution in any language, except what I've just prohibited above! My Solution I've now posted my C# solution here (403 chars). Update: My new solution has beaten the old one significantly at 294 chars, with the help of a bit of lovely regex! I suspected that this will get easily beaten by some of the languages out there with lighter syntax (particularly the funcional/dynamic ones), and have been proved right, but I'd be curious if someone could beat this in C# still. Update I've seen some very crafty solutions already. Thanks to everyone who has posted one. Although I haven't tested any of them yet, I'm going to trust people and assume they at least work with all of the given examples. Just for the note, re-entrancy (i.e. thread-safety) is not a requirement for the function, though it is a bonus. Format Please post all answers in the following format for the purpose of easy comparison: Language Number of characters: ??? Fully obfuscated function: (code here) Clear/semi-obfuscated function: (code here) Any notes on the algorithm/clever shortcuts it takes.

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  • CodeGolf: Brothers

    - by John McClane
    Hi guys, I just finished participating in the 2009 ACM ICPC Programming Conest in the Latinamerican Finals. These questions were for Brazil, Bolivia, Chile, etc. My team and I could only finish two questions out of the eleven (not bad I think for the first try). Here's one we could finish. I'm curious to seeing any variations to the code. The question in full: ps: These questions can also be found on the official ICPC website available to everyone. In the land of ACM ruled a greeat king who became obsessed with order. The kingdom had a rectangular form, and the king divided the territory into a grid of small rectangular counties. Before dying the king distributed the counties among his sons. The king was unaware of the rivalries between his sons: The first heir hated the second but not the rest, the second hated the third but not the rest, and so on...Finally, the last heir hated the first heir, but not the other heirs. As soon as the king died, the strange rivaly among the King's sons sparked off a generalized war in the kingdom. Attacks only took place between pairs of adjacent counties (adjacent counties are those that share one vertical or horizontal border). A county X attacked an adjacent county Y whenever X hated Y. The attacked county was always conquered. All attacks where carried out simultanously and a set of simultanous attacks was called a battle. After a certain number of battles, the surviving sons made a truce and never battled again. For example if the king had three sons, named 0, 1 and 2, the figure below shows what happens in the first battle for a given initial land distribution: INPUT The input contains several test cases. The first line of a test case contains four integers, N, R, C and K. N - The number of heirs (2 <= N <= 100) R and C - The dimensions of the land. (2 <= R,C <= 100) K - Number of battles that are going to take place. (1 <= K <= 100) Heirs are identified by sequential integers starting from zero. Each of the next R lines contains C integers HeirIdentificationNumber (saying what heir owns this land) separated by single spaces. This is to layout the initial land. The last test case is a line separated by four zeroes separated by single spaces. (To exit the program so to speak) Output For each test case your program must print R lines with C integers each, separated by single spaces in the same format as the input, representing the land distribution after all battles. Sample Input: Sample Output: 3 4 4 3 2 2 2 0 0 1 2 0 2 1 0 1 1 0 2 0 2 2 2 0 0 1 2 0 0 2 0 0 0 1 2 2 Another example: Sample Input: Sample Output: 4 2 3 4 1 0 3 1 0 3 2 1 2 2 1 2

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  • Asp.net hosting equivalent of Dreamhost (pricing, features and support)

    - by Cherian
    Disclaimer: I have browsed http://stackoverflow.com/questions/tagged/asp.net+hosting and didn’t find anything quite similar in value to Dreamhost. One of the biggest impediments IMHO for developing web applications on asp.net is the cost of deployment. I am not talking about building sites like Stackoverflow.com or plentyoffish.com. This is about sites that are bigger than brochureware and smaller than ones that require dedicated servers. Let me give you an example. xmec.org is an asp.net site I maintain for my college alumni. On an average it’s slated to hit around 1000-1100 views per day. At present it’s hosted on godaddy. The service is so damn pathetic; I am using it only because of the lack of options. The site doesn’t scale (no, it’s not the code) and the web control panels are extremely slow. The money I pay doesn’t justify the service or the performance. Every deployment push is a visit to the infuriating web control panel to set the permissions and the root directories. Had I developed it in python, this would have been deployed on Dreamhost.com with $10/year hosting fees (they have offers running all throughout) 50 GB space 5 MySQL Databases Shell / FTP Users POP / SMTP Access Unlimited Domains hosting Unlimited Sub domains hosting Unlimited Domains Forwarded/Mirrored Custom DNS (These are the only ones I could think of. More at the feature page) With a dream host shell, I even have a svn checked-out version of wordpress for my blog. Now, that’s control! To my question: Is there any asp.net (preferably .net 3.5. Dreamhost keeps on updating versions every fortnight) hosting company providing remotely similar feature-sets and pricing like Dreamhost. My requirements are: Less than $15-25/ year Typical WISP minus PHP .net 3.5 SP1 Full Trust mode(I can live with medium trust, if not for the IL emitting libraries) Isolated Application Pool 5 – 10 MySQL db’s Unlimited domain hosting MsSql 2005 or 2008 FTP support At Least 5 GB space SMTP IIS 7 Log files Accessibility Moderately good control panel Scripting, shell support Nominal bandwidth Another case in point: Recently I’ve been contemplating building a tool-website to find duplicates and weird characters in my Google contacts and fix them. With asp.net, the best part is that I can do this with LINQ to XML in less than 100 lines of code. What’s bad is the hosting part. I don’t think I stand to make any money out of this and therefore can’t afford to host it on GoGrid or DiscountAsp.net. Godaddy is not an option either. If I do this in python, I can push to this my existing $10 Dreamhost account with another domain pointed. No extra cost. Svn exported with scripts (capability) to change the connection string! Looking at the problem holistically, I think I represent a large breed of programmers playing it cheap and experimenting different things on a regular basis, one of which will become the next twitter/digg.

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  • Is the design notion of layers contrived?

    - by Bruce
    Hi all I'm reading through Eric Evans' awesome work, Domain-Driven Design. However, I can't help feeling that the 'layers' model is contrived. To expand on that statement, it seems as if it tries to shoe-horn various concepts into a specific, neat model, that of layers talking to each other. It seems to me that the layers model is too simplified to actually capture the way that (good) software works. To expand further: Evans says: "Partition a complex program into layers. Develop a design within each layer that is cohesive and that depends only on the layers below. Follow standard architectural patterns to provide loose coupling to the layers above." Maybe I'm misunderstanding what 'depends' means, but as far as I can see, it can either mean a) Class X (in the UI for example) has a reference to a concrete class Y (in the main application) or b) Class X has a reference to a class Y-ish object providing class Y-ish services (ie a reference held as an interface). If it means (a), then this is clearly a bad thing, since it defeats re-using the UI as a front-end to some other application that provides Y-ish functionality. But if it means (b), then how is the UI any more dependent on the application, than the application is dependent on the UI? Both are decoupled from each other as much as they can be while still talking to each other. Evans' layer model of dependencies going one way seems too neat. First, isn't it more accurate to say that each area of the design provides a module that is pretty much an island to itself, and that ideally all communication is through interfaces, in a contract-driven/responsibility-driven paradigm? (ie, the 'dependency only on lower layers' is contrived). Likewise with the domain layer talking to the database - the domain layer is as decoupled (through DAO etc) from the database as the database is from the domain layer. Neither is dependent on the other, both can be swapped out. Second, the idea of a conceptual straight line (as in from one layer to the next) is artificial - isn't there more a network of intercommunicating but separate modules, including external services, utility services and so on, branching off at different angles? Thanks all - hoping that your responses can clarify my understanding on this..

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  • Regular exp to validate email in C

    - by Liju Mathew
    Hi, We need to write a email validation program in C. We are planning to use GNU Cregex.h) regular expression. The regular expression we prepared is [a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])? But the below code is failing while compiling the regex. #include <stdio.h> #include <regex.h> int main(const char *argv, int argc) { const char *reg_exp = "[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?"; int status = 1; char email[71]; regex_t preg; int rc; printf("The regex = %s\n", reg_exp); rc = regcomp(&preg, reg_exp, REG_EXTENDED|REG_NOSUB); if (rc != 0) { if (rc == REG_BADPAT || rc == REG_ECOLLATE) fprintf(stderr, "Bad Regex/Collate\n"); if (rc == REG_ECTYPE) fprintf(stderr, "Invalid Char\n"); if (rc == REG_EESCAPE) fprintf(stderr, "Trailing \\\n"); if (rc == REG_ESUBREG || rc == REG_EBRACK) fprintf(stderr, "Invalid number/[] error\n"); if (rc == REG_EPAREN || rc == REG_EBRACE) fprintf(stderr, "Paren/Bracket error\n"); if (rc == REG_BADBR || rc == REG_ERANGE) fprintf(stderr, "{} content invalid/Invalid endpoint\n"); if (rc == REG_ESPACE) fprintf(stderr, "Memory error\n"); if (rc == REG_BADRPT) fprintf(stderr, "Invalid regex\n"); fprintf(stderr, "%s: Failed to compile the regular expression:%d\n", __func__, rc); return 1; } while (status) { fgets(email, sizeof(email), stdin); status = email[0]-48; rc = regexec(&preg, email, (size_t)0, NULL, 0); if (rc == 0) { fprintf(stderr, "%s: The regular expression is a match\n", __func__); } else { fprintf(stderr, "%s: The regular expression is not a match: %d\n", __func__, rc); } } regfree(&preg); return 0; } The regex compilation is failing with the below error. The regex = [a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])? Invalid regex main: Failed to compile the regular expression:13 What is the cause of this error? Whether the regex need to be modified? Thanks, Mathew Liju

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  • Flex+JPA/Hibernate+BlazeDS+MySQL how to debug this monster?!

    - by Zenzen
    Ok so I'm making a "simple" web app using the technologies from the topic, recently I found http://www.adobe.com/devnet/flex/articles/flex_hibernate.html so I'm following it and I try to apply it to my app, the only difference being I'm working on a Mac and I'm using MAMP for the database (so no command line for me). The thing is I'm having some trouble with retrieving/connecting to the database. I have the remoting-config.xml, persistance.xml, a News.java class (my Entity), a NewsService.java class, a News.as class - all just like in the tutorial. I have of course this line in one of my .mxmls: <mx:RemoteObject id="loaderService" destination="newsService" result="handleLoadResult(event)" fault="handleFault(event)" showBusyCursor="true" /> And my remoting-config.xml looks like this (well part of it): <destination id="newsService"> <properties><source>com.gamelist.news.NewsService</source></properties> </destination> NewsService has a method: public List<News> getLatestNews() { EntityManagerFactory emf = Persistence.createEntityManagerFactory(PERSISTENCE_UNIT); EntityManager em = emf.createEntityManager(); Query findLatestQuery = em.createNamedQuery("news.findLatest"); List<News> news = findLatestQuery.getResultList(); return news; } And the named query is in the News class: @Entity @Table(name="GLT_NEWS") @NamedQueries({ @NamedQuery(name="news.findLatest", query="from GLT_NEWS order by new_date_added limit 5 ") }) The handledLoadResult looks like this: private function handleLoadResult(ev:ResultEvent):void { newsList = ev.result as ArrayCollection; newsRecords = newsList.length; } Where: [Bindable] private var newsList:ArrayCollection = new ArrayCollection(); But when I try to trigger: loaderService.getLatestNews(); nothing happens, newsList is empty. Few things I need to point out: 1) as I said I didn't install mysql manually, but I'm using MAMP (yes, the server's running), could this cause some trouble? 2) I already have a "gladm" database and I have a "GLT_NEWS" table with all the fields, is this bad? Basically the question is how am I suppose to debug this thing so I can find the mistake I'm making? I know that loadData() is executed (did a trace()), but I have no idea what happens with loaderService.getLatestNews()... @EDIT: ok so I see I'm getting an error in the "fault handler" which says "Error: Client.Error.MessageSend - Channel.Connect.Failed error NetConnection.Call.Failed: HTTP: Status 404: url: 'http://localhost:8080/WebContent/messagebroker/amf' - "

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  • Conway's Game of Life - C++ and Qt

    - by Jeff Bridge
    I've done all of the layouts and have most of the code written even. But, I'm stuck in two places. 1) I'm not quite sure how to set up the timer. Am I using it correctly in the gridwindow class? And, am I used the timer functions/signals/slots correctly with the other gridwindow functions. 2) In GridWindow's timerFired() function, I'm having trouble checking/creating the vector-vectors. I wrote out in the comments in that function exactly what I am trying to do. Any help would be much appreciated. main.cpp // Main file for running the grid window application. #include <QApplication> #include "gridwindow.h" //#include "timerwindow.h" #include <stdexcept> #include <string> #include <fstream> #include <sstream> #include <iostream> void Welcome(); // Welcome Function - Prints upon running program; outputs program name, student name/id, class section. void Rules(); // Rules Function: Prints the rules for Conway's Game of Life. using namespace std; // A simple main method to create the window class and then pop it up on the screen. int main(int argc, char *argv[]) { Welcome(); // Calls Welcome function to print student/assignment info. Rules(); // Prints Conway's Game Rules. QApplication app(argc, argv); // Creates the overall windowed application. int rows = 25, cols = 35; //The number of rows & columns in the game grid. GridWindow widget(NULL,rows,cols); // Creates the actual window (for the grid). widget.show(); // Shows the window on the screen. return app.exec(); // Goes into visual loop; starts executing GUI. } // Welcome Function: Prints my name/id, my class number, the assignment, and the program name. void Welcome() { cout << endl; cout << "-------------------------------------------------------------------------------------------------" << endl; cout << "Name/ID - Gabe Audick #7681539807" << endl; cout << "Class/Assignment - CSCI-102 Disccusion 29915: Homework Assignment #4" << endl; cout << "-------------------------------------------------------------------------------------------------" << endl << endl; } // Rules Function: Prints the rules for Conway's Game of Life. void Rules() { cout << "Welcome to Conway's Game of Life." << endl; cout << "Game Rules:" << endl; cout << "\t 1) Any living cell with fewer than two living neighbours dies, as if caused by underpopulation." << endl; cout << "\t 2) Any live cell with more than three live neighbours dies, as if by overcrowding." << endl; cout << "\t 3) Any live cell with two or three live neighbours lives on to the next generation." << endl; cout << "\t 4) Any dead cell with exactly three live neighbours becomes a live cell." << endl << endl; cout << "Enjoy." << endl << endl; } gridcell.h // A header file for a class representing a single cell in a grid of cells. #ifndef GRIDCELL_H_ #define GRIDCELL_H_ #include <QPalette> #include <QColor> #include <QPushButton> #include <Qt> #include <QWidget> #include <QFrame> #include <QHBoxLayout> #include <iostream> // An enum representing the two different states a cell can have. enum CellType { DEAD, // DEAD = Dead Cell. --> Color = White. LIVE // LIVE = Living Cell. ---> Color = White. }; /* Class: GridCell. A class representing a single cell in a grid. Each cell is implemented as a QT QFrame that contains a single QPushButton. The button is sized so that it takes up the entire frame. Each cell also keeps track of what type of cell it is based on the CellType enum. */ class GridCell : public QFrame { Q_OBJECT // Macro allowing us to have signals & slots on this object. private: QPushButton* button; // The button inside the cell that gives its clickability. CellType type; // The type of cell (DEAD or LIVE.) public slots: void handleClick(); // Callback for handling a click on the current cell. void setType(CellType type); // Cell type mutator. Calls the "redrawCell" function. signals: void typeChanged(CellType type); // Signal to notify listeners when the cell type has changed. public: GridCell(QWidget *parent = NULL); // Constructor for creating a cell. Takes parent widget or default parent to NULL. virtual ~GridCell(); // Destructor. void redrawCell(); // Redraws cell: Sets new type/color. CellType getType() const; //Simple getter for the cell type. private: Qt::GlobalColor getColorForCellType(); // Helper method. Returns color that cell should be based from its value. }; #endif gridcell.cpp #include <iostream> #include "gridcell.h" #include "utility.h" using namespace std; // Constructor: Creates a grid cell. GridCell::GridCell(QWidget *parent) : QFrame(parent) { this->type = DEAD; // Default: Cell is DEAD (white). setFrameStyle(QFrame::Box); // Set the frame style. This is what gives each box its black border. this->button = new QPushButton(this); //Creates button that fills entirety of each grid cell. this->button->setSizePolicy(QSizePolicy::Expanding,QSizePolicy::Expanding); // Expands button to fill space. this->button->setMinimumSize(19,19); //width,height // Min height and width of button. QHBoxLayout *layout = new QHBoxLayout(); //Creates a simple layout to hold our button and add the button to it. layout->addWidget(this->button); setLayout(layout); layout->setStretchFactor(this->button,1); // Lets the buttons expand all the way to the edges of the current frame with no space leftover layout->setContentsMargins(0,0,0,0); layout->setSpacing(0); connect(this->button,SIGNAL(clicked()),this,SLOT(handleClick())); // Connects clicked signal with handleClick slot. redrawCell(); // Calls function to redraw (set new type for) the cell. } // Basic destructor. GridCell::~GridCell() { delete this->button; } // Accessor for the cell type. CellType GridCell::getType() const { return(this->type); } // Mutator for the cell type. Also has the side effect of causing the cell to be redrawn on the GUI. void GridCell::setType(CellType type) { this->type = type; redrawCell(); } // Handler slot for button clicks. This method is called whenever the user clicks on this cell in the grid. void GridCell::handleClick() { // When clicked on... if(this->type == DEAD) // If type is DEAD (white), change to LIVE (black). type = LIVE; else type = DEAD; // If type is LIVE (black), change to DEAD (white). setType(type); // Sets new type (color). setType Calls redrawCell() to recolor. } // Method to check cell type and return the color of that type. Qt::GlobalColor GridCell::getColorForCellType() { switch(this->type) { default: case DEAD: return Qt::white; case LIVE: return Qt::black; } } // Helper method. Forces current cell to be redrawn on the GUI. Called whenever the setType method is invoked. void GridCell::redrawCell() { Qt::GlobalColor gc = getColorForCellType(); //Find out what color this cell should be. this->button->setPalette(QPalette(gc,gc)); //Force the button in the cell to be the proper color. this->button->setAutoFillBackground(true); this->button->setFlat(true); //Force QT to NOT draw the borders on the button } gridwindow.h // A header file for a QT window that holds a grid of cells. #ifndef GRIDWINDOW_H_ #define GRIDWINDOW_H_ #include <vector> #include <QWidget> #include <QTimer> #include <QGridLayout> #include <QLabel> #include <QApplication> #include "gridcell.h" /* class GridWindow: This is the class representing the whole window that comes up when this program runs. It contains a header section with a title, a middle section of MxN cells and a bottom section with buttons. */ class GridWindow : public QWidget { Q_OBJECT // Macro to allow this object to have signals & slots. private: std::vector<std::vector<GridCell*> > cells; // A 2D vector containing pointers to all the cells in the grid. QLabel *title; // A pointer to the Title text on the window. QTimer *timer; // Creates timer object. public slots: void handleClear(); // Handler function for clicking the Clear button. void handleStart(); // Handler function for clicking the Start button. void handlePause(); // Handler function for clicking the Pause button. void timerFired(); // Method called whenever timer fires. public: GridWindow(QWidget *parent = NULL,int rows=3,int cols=3); // Constructor. virtual ~GridWindow(); // Destructor. std::vector<std::vector<GridCell*> >& getCells(); // Accessor for the array of grid cells. private: QHBoxLayout* setupHeader(); // Helper function to construct the GUI header. QGridLayout* setupGrid(int rows,int cols); // Helper function to constructor the GUI's grid. QHBoxLayout* setupButtonRow(); // Helper function to setup the row of buttons at the bottom. }; #endif gridwindow.cpp #include <iostream> #include "gridwindow.h" using namespace std; // Constructor for window. It constructs the three portions of the GUI and lays them out vertically. GridWindow::GridWindow(QWidget *parent,int rows,int cols) : QWidget(parent) { QHBoxLayout *header = setupHeader(); // Setup the title at the top. QGridLayout *grid = setupGrid(rows,cols); // Setup the grid of colored cells in the middle. QHBoxLayout *buttonRow = setupButtonRow(); // Setup the row of buttons across the bottom. QVBoxLayout *layout = new QVBoxLayout(); // Puts everything together. layout->addLayout(header); layout->addLayout(grid); layout->addLayout(buttonRow); setLayout(layout); } // Destructor. GridWindow::~GridWindow() { delete title; } // Builds header section of the GUI. QHBoxLayout* GridWindow::setupHeader() { QHBoxLayout *header = new QHBoxLayout(); // Creates horizontal box. header->setAlignment(Qt::AlignHCenter); this->title = new QLabel("CONWAY'S GAME OF LIFE",this); // Creates big, bold, centered label (title): "Conway's Game of Life." this->title->setAlignment(Qt::AlignHCenter); this->title->setFont(QFont("Arial", 32, QFont::Bold)); header->addWidget(this->title); // Adds widget to layout. return header; // Returns header to grid window. } // Builds the grid of cells. This method populates the grid's 2D array of GridCells with MxN cells. QGridLayout* GridWindow::setupGrid(int rows,int cols) { QGridLayout *grid = new QGridLayout(); // Creates grid layout. grid->setHorizontalSpacing(0); // No empty spaces. Cells should be contiguous. grid->setVerticalSpacing(0); grid->setSpacing(0); grid->setAlignment(Qt::AlignHCenter); for(int i=0; i < rows; i++) //Each row is a vector of grid cells. { std::vector<GridCell*> row; // Creates new vector for current row. cells.push_back(row); for(int j=0; j < cols; j++) { GridCell *cell = new GridCell(); // Creates and adds new cell to row. cells.at(i).push_back(cell); grid->addWidget(cell,i,j); // Adds to cell to grid layout. Column expands vertically. grid->setColumnStretch(j,1); } grid->setRowStretch(i,1); // Sets row expansion horizontally. } return grid; // Returns grid. } // Builds footer section of the GUI. QHBoxLayout* GridWindow::setupButtonRow() { QHBoxLayout *buttonRow = new QHBoxLayout(); // Creates horizontal box for buttons. buttonRow->setAlignment(Qt::AlignHCenter); // Clear Button - Clears cell; sets them all to DEAD/white. QPushButton *clearButton = new QPushButton("CLEAR"); clearButton->setFixedSize(100,25); connect(clearButton, SIGNAL(clicked()), this, SLOT(handleClear())); buttonRow->addWidget(clearButton); // Start Button - Starts game when user clicks. Or, resumes game after being paused. QPushButton *startButton = new QPushButton("START/RESUME"); startButton->setFixedSize(100,25); connect(startButton, SIGNAL(clicked()), this, SLOT(handleStart())); buttonRow->addWidget(startButton); // Pause Button - Pauses simulation of game. QPushButton *pauseButton = new QPushButton("PAUSE"); pauseButton->setFixedSize(100,25); connect(pauseButton, SIGNAL(clicked()), this, SLOT(handlePause())); buttonRow->addWidget(pauseButton); // Quit Button - Exits program. QPushButton *quitButton = new QPushButton("EXIT"); quitButton->setFixedSize(100,25); connect(quitButton, SIGNAL(clicked()), qApp, SLOT(quit())); buttonRow->addWidget(quitButton); return buttonRow; // Returns bottom of layout. } /* SLOT method for handling clicks on the "clear" button. Receives "clicked" signals on the "Clear" button and sets all cells to DEAD. */ void GridWindow::handleClear() { for(unsigned int row=0; row < cells.size(); row++) // Loops through current rows' cells. { for(unsigned int col=0; col < cells[row].size(); col++) { GridCell *cell = cells[row][col]; // Grab the current cell & set its value to dead. cell->setType(DEAD); } } } /* SLOT method for handling clicks on the "start" button. Receives "clicked" signals on the "start" button and begins game simulation. */ void GridWindow::handleStart() { this->timer = new QTimer(this); // Creates new timer. connect(this->timer, SIGNAL(timeout()), this, SLOT(timerFired())); // Connect "timerFired" method class to the "timeout" signal fired by the timer. this->timer->start(500); // Timer to fire every 500 milliseconds. } /* SLOT method for handling clicks on the "pause" button. Receives "clicked" signals on the "pause" button and stops the game simulation. */ void GridWindow::handlePause() { this->timer->stop(); // Stops the timer. delete this->timer; // Deletes timer. } // Accessor method - Gets the 2D vector of grid cells. std::vector<std::vector<GridCell*> >& GridWindow::getCells() { return this->cells; } void GridWindow::timerFired() { // I'm not sure how to write this code. // I want to take the original vector-vector, and also make a new, empty vector-vector of the same size. // I would then go through the code below with the original vector, and apply the rules to the new vector-vector. // Finally, I would make the new vector-vecotr the original vector-vector. (That would be one step in the simulation.) cout << cells[1][2]; /* for (unsigned int m = 0; m < original.size(); m++) { for (unsigned int n = 0; n < original.at(m).size(); n++) { unsigned int neighbors = 0; //Begin counting number of neighbors. if (original[m-1][n-1].getType() == LIVE) // If a cell next to [i][j] is LIVE, add one to the neighbor count. neighbors += 1; if (original[m-1][n].getType() == LIVE) neighbors += 1; if (original[m-1][n+1].getType() == LIVE) neighbors += 1; if (original[m][n-1].getType() == LIVE) neighbors += 1; if (original[m][n+1].getType() == LIVE) neighbors += 1; if (original[m+1][n-1].getType() == LIVE) neighbors += 1; if (original[m+1][n].getType() == LIVE) neighbors += 1; if (original[m+1][n+1].getType() == LIVE) neighbors += 1; if (original[m][n].getType() == LIVE && neighbors < 2) // Apply game rules to cells: Create new, updated grid with the roundtwo vector. roundtwo[m][n].setType(LIVE); else if (original[m][n].getType() == LIVE && neighbors > 3) roundtwo[m][n].setType(DEAD); else if (original[m][n].getType() == LIVE && (neighbors == 2 || neighbors == 3)) roundtwo[m][n].setType(LIVE); else if (original[m][n].getType() == DEAD && neighbors == 3) roundtwo[m][n].setType(LIVE); } }*/ }

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  • How to create a compiler in vb.net

    - by Cyclone
    Before answering this question, understand that I am not asking how to create my own programming language, I am asking how, using vb.net code, I can create a compiler for a language like vb.net itself. Essentially, the user inputs code, they get a .exe. By NO MEANS do I want to write my own language, as it seems other compiler related questions on here have asked. I also do not want to use the vb.net compiler itself, nor do I wish to duplicate the IDE. The exact purpose of what I wish to do is rather hard to explain, but all I need is a nudge in the right direction for writing a compiler (from scratch if possible) which can simply take input and create a .exe. I have opened .exe files as plain text before (my own programs) to see if I could derive some meaning from what I assumed would be human readable text, yet I was obviously sorely disappointed to see the random ascii, though it is understandable why this is all I found. I know that a .exe file is simply lines of code, being parsed by the computer it is on, but my question here really boils down to this: What code makes up a .exe? How could I go about making one in a plain text editor if I wanted to? (No, I do not want to do that, but if I understand the process my goals will be much easier to achieve.) What makes an executable file an executable file? Where does the logic of the code fit in? This is intended to be a programming question as opposed to a computer question, which is why I did not post it on SuperUser. I know plenty of information about the System.IO namespace, so I know how to create a file and write to it, I simply do not know what exactly I would be placing inside this file to get it to work as an executable file. I am sorry if this question is "confusing", "dumb", or "obvious", but I have not been able to find any information regarding the actual contents of an executable file anywhere. One of my google searches Something that looked promising EDIT: The second link here, while it looked good, was an utter fail. I am not going to waste hours of my time hitting keys and recording the results. "Use the "Alt" and the 3-digit combinations to create symbols that do not appear on the keyboard but that you need in the program." (step 4) How the heck do I know what symbols I need??? Thank you very much for your help, and my apologies if this question is a nooby or "bad" one. To sum this up simply: I want to create a program in vb.net that can compile code in a particular language to a single executable file. What methods exist that can allow me to do this, and if there are none, how can I go about writing my own from scratch?

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  • Raw XML Push from input stream captures only the first line of XML

    - by pqsk
    I'm trying to read XML that is being pushed to my java app. I originally had this in my glassfish server working. The working code in glassfish is as follows: public class XMLPush implements Serializable { public void processXML() { StringBuilder sb = new StringBuilder(); BufferedReader br = null; try { br = ((HttpServletRequest)FacesContext.getCurrentInstance().getExternalContext().getRequest()).getReader (); String s = null; while((s = br.readLine ()) != null) { sb.append ( s ); } //other code to process xml ........... ............................. }catch(Exception ex) { XMLCreator.exceptionOutput ( "processXML","Exception",ex); } .... ..... }//processXML }//class It works perfect, but my client is unable to have glassfish on their server. I tried grabbing the raw xml from php, but I couldn't get it to work. I decided to open up a socket and listen for the xml push manually. Here is my code for receiving the push: public class ListenerService extends Thread { private BufferedReader reader = null; private String line; public ListenerService ( Socket connection )thows Exception { this.reader = new BufferedReader ( new InputStreamReader ( connection.getInputStream () ) ); this.line = null; }//ListenerService @Override public void run () { try { while ( (this.line = this.reader.readLine ()) != null) { System.out.println ( this.line ); ........ }//while } System.out.println ( ex.toString () ); } } catch ( Exception ex ) { ... }//catch }//run I haven't done much socket programing, but from what I read for the past week is that passing the xml into a string is bad. What am I doing wrong and why is it that in glassfish server it works, and when I just open a socket myself it doesn't? this is all that I receive from the push: PUT /?XML_EXPORT_REASON=ResponseLoop&TIMESTAMP=1292559547 HTTP/1.1 Host: ************************ Accept: */* Content-Length: 470346 Expect: 100-continue <?xml version="1.0" encoding="UTF-8" ?> Where did the xml go? Is it because I am placing it in a string? I just need to grab the xml and save it into a file and then process it. Everything else works, but this.Any help would be greatly appreciated.

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  • SSIS DTS Package flat file error - "The file name specified in the connection was not valid"

    - by MisterZimbu
    I have a pretty basic SSIS package that is attempting to read a file hosted on a share, and import its contents to a database table. The package runs fine when I run it manually within SSIS. However, when I set up a SQL Agent job and attempt to execute it, I get the following error: Executed as user: DOMAIN\UserName. Microsoft (R) SQL Server Execute Package Utility Version 9.00.3042.00 for 64-bit Copyright (C) Microsoft Corp 1984-2005. All rights reserved. Started: 10:14:17 AM Error: 2010-05-03 10:14:17.75 Code: 0xC001401E Source: DataImport Connection manager "Data File Local" Description: The file name "\10.1.1.159\llpf\datafile.dat" specified in the connection was not valid. End Error Error: 2010-05-03 10:14:17.75 Code: 0xC001401D Source: DataAnimalImport Description: Connection "Data File Local" failed validation. End Error DTExec: The package execution returned DTSER_FAILURE (1). Started: 10:14:17 AM Finished: 10:14:17 AM Elapsed: 0.594 seconds. The package execution failed. The step failed. This leads me to believe it's a permissions issue, but every attempt I've made to fix it has failed. What I've tried so far: Run as the SQL Agent account (DOMAIN\SqlAgent) - yields same error. DOMAIN\SqlAgent has "Full Control" permissions on both the share and the uploaded file. Set up a proxy account with a different account's credentials (DOMAIN\Account) - yields same error. Like above, "Full Control" permissions were given over the share to that account. Gave "Everyone" full control permissions over the share (temporarily!). Yielded same error. Manually copied the file to a local path and tested with the SQL Agent account. Worked properly. Added an ActiveX script task that would first copy the remotely hosted file to a local path, and then have the DTS package reference the local file. Gave a completely nondescriptive (even by SSIS standards) error when trying to run the script. Set up a proxy account, using my own personal account's credentials - worked correctly. However, this is not an acceptable solution as there are password policies in place on my account, as well as being a bad practice to set things up this way in general. Any ideas? I'm still convinced it's a permissions issue. However, what I've read from various searches more or less says giving the executing account permissions on the share should work. However, this is not the case here (unless I'm missing something obscure when I'm setting up permissions on the share).

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  • Why does one loop take longer to detect a shared memory update than another loop?

    - by Joseph Garvin
    I've written a 'server' program that writes to shared memory, and a client program that reads from the memory. The server has different 'channels' that it can be writing to, which are just different linked lists that it's appending items too. The client is interested in some of the linked lists, and wants to read every node that's added to those lists as it comes in, with the minimum latency possible. I have 2 approaches for the client: For each linked list, the client keeps a 'bookmark' pointer to keep its place within the linked list. It round robins the linked lists, iterating through all of them over and over (it loops forever), moving each bookmark one node forward each time if it can. Whether it can is determined by the value of a 'next' member of the node. If it's non-null, then jumping to the next node is safe (the server switches it from null to non-null atomically). This approach works OK, but if there are a lot of lists to iterate over, and only a few of them are receiving updates, the latency gets bad. The server gives each list a unique ID. Each time the server appends an item to a list, it also appends the ID number of the list to a master 'update list'. The client only keeps one bookmark, a bookmark into the update list. It endlessly checks if the bookmark's next pointer is non-null ( while(node->next_ == NULL) {} ), if so moves ahead, reads the ID given, and then processes the new node on the linked list that has that ID. This, in theory, should handle large numbers of lists much better, because the client doesn't have to iterate over all of them each time. When I benchmarked the latency of both approaches (using gettimeofday), to my surprise #2 was terrible. The first approach, for a small number of linked lists, would often be under 20us of latency. The second approach would have small spats of low latencies but often be between 4,000-7,000us! Through inserting gettimeofday's here and there, I've determined that all of the added latency in approach #2 is spent in the loop repeatedly checking if the next pointer is non-null. This is puzzling to me; it's as if the change in one process is taking longer to 'publish' to the second process with the second approach. I assume there's some sort of cache interaction going on I don't understand. What's going on?

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  • Potential issues using member's "from" address and the "sender" header

    - by Paul Burney
    Hi all, A major component of our application sends email to members on behalf of other members. Currently we set the "From" address to our system address and use a "Reply-to" header with the member's address. The issue is that replies from some email clients (and auto-replies/bounces) don't respect the "Reply-to" header so get sent to our system address, effectively sending them to a black hole. We're considering setting the "From" address to our member's address, and the "Sender" address to our system address. It appears this way would pass SPF and Sender-ID checks. Are there any reasons not to switch to this method? Are there any other potential issues? Thanks in advance, -Paul Here are way more details than you probably need: When the application was first developed, we just changed the "from" address to be that of the sending member as that was the common practice at the time (this was many years ago). We later changed that to have the "from" address be the member's name and our address, i.e., From: "Mary Smith" <[email protected]> With a "reply-to" header set to the member's address: Reply-To: "Mary Smith" <[email protected]> This helped with messages being mis-categorized as spam. As SPF became more popular, we added an additional header that would work in conjunction with our SPF records: Sender: <[email protected]> Things work OK, but it turns out that, in practice, some email clients and most MTA's don't respect the "Reply-To" header. Because of this, many members send messages to [email protected] instead of the desired member. So, I started envisioning various schemes to add data about the sender to the email headers or encode it in the "from" email address so that we could process the response and redirect appropriately. For example, From: "Mary Smith" <[email protected]> where the string after "messages" is a hash representing Mary Smith's member in our system. Of course, that path could lead to a lot of pain as we need to develop MTA functionality for our system address. I was looking again at the SPF documentation and found this page interesting: http://www.openspf.org/Best_Practices/Webgenerated They show two examples, that of evite.com and that of egreetings.com. Basically, evite.com is doing it the way we're doing it. The egreetings.com example uses the member's from address with an added "Sender" header. So the question is, are there any potential issues with using the egreetings method of the member's from address with a sender header? That would eliminate the replies that bad clients send to the system address. I don't believe that it solves the bounce/vacation/whitelist issue since those often send to the MAIL FROM even if Return Path is specified.

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  • Connecting client (on VirtualBox) and server (on localhost) using CORBA - org.omg.CORBA.BAD_PARAM:

    - by yak
    Im working now on simple gui appllication in Java/C++ and CORBA. I want my client on VirtualBox connect to server on localhost. When I have a simple app, like a calc I wrote about earlier its just fine. But when it comes to run client which needs some args witch javas -cp option, Im getting errors. (Theres no such problem when I have both client and server in localhost!) My errors: WARNING: "IOP00100007: (BAD_PARAM) string_to_object conversion failed due to bad scheme name" org.omg.CORBA.BAD_PARAM: vmcid: OMG minor code: 7 completed: No at com.sun.corba.se.impl.logging.OMGSystemException.soBadSchemeName(Unkn own Source) at com.sun.corba.se.impl.logging.OMGSystemException.soBadSchemeName(Unkn own Source) at com.sun.corba.se.impl.resolver.INSURLOperationImpl.operate(Unknown So urce) at com.sun.corba.se.impl.resolver.ORBInitRefResolverImpl.resolve(Unknown Source) at com.sun.corba.se.impl.resolver.CompositeResolverImpl.resolve(Unknown Source) at com.sun.corba.se.impl.resolver.CompositeResolverImpl.resolve(Unknown Source) at com.sun.corba.se.impl.orb.ORBImpl.resolve_initial_references(Unknown Source) at ClientConnection.connect(ClientConnection.java:57) at Client.main(Client.java:295) Exception in thread "main" org.omg.CORBA.BAD_PARAM: vmcid: OMG minor code: 7 completed: No at com.sun.corba.se.impl.logging.OMGSystemException.soBadSchemeName(Unkn own Source) at com.sun.corba.se.impl.logging.OMGSystemException.soBadSchemeName(Unkn own Source) at com.sun.corba.se.impl.resolver.INSURLOperationImpl.operate(Unknown So urce) at com.sun.corba.se.impl.resolver.ORBInitRefResolverImpl.resolve(Unknown Source) at com.sun.corba.se.impl.resolver.CompositeResolverImpl.resolve(Unknown Source) at com.sun.corba.se.impl.resolver.CompositeResolverImpl.resolve(Unknown Source) at com.sun.corba.se.impl.orb.ORBImpl.resolve_initial_references(Unknown Source) at ClientConnection.connect(ClientConnection.java:57) at Client.main(Client.java:295) make[1]: *** [run] Error 1 ClientConnection.java:57 is a line objRef = clientORB.resolve_initial_references("NameService"); Client.java:295 is a line: ClientConnection.connect(args); A connect method is just an ordinary client-connection corba code. I ran my example: 1) C:\Temp\Client>java -cp .:../Dir1:../Dir2 Client -ORBInitRef NameService =corbaloc::192.168.56.1:2809/NameService Error: Could not find or load main class Client so its even didnt run at all .. 2) with the help of a Makefile: HOST = 192.168.56.1 PORT = 2809 NAMESERVICE = NameService run: java -cp .:../Dir1:../Dir2 Client -ORBInitRef NameService=corbaloc::$(HOST):$(PORT)/$(NAMESERVICE) by typing make run and then I got those error I posted earlier. Whats wrong? I mean, a simple code works fine but gui version doesnt want to ... is there a problem with -cp option? I cant change my apps' dir tree.

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  • Subclassing a window from a thread in c#

    - by user258651
    I'm creating a thread that looks for a window. When it finds the window, it overrides its windowproc, and handles WM_COMMAND and WM_CLOSE. Here's the code that looks for the window and subclasses it: public void DetectFileDialogProc() { Window fileDialog = null; // try to find the dialog twice, with a delay of 500 ms each time for (int attempts = 0; fileDialog == null && attempts < 2; attempts++) { // FindDialogs enumerates all windows of class #32770 via an EnumWindowProc foreach (Window wnd in FindDialogs(500)) { IntPtr parent = NativeMethods.User32.GetParent(wnd.Handle); if (parent != IntPtr.Zero) { // we're looking for a dialog whose parent is a dialog as well Window parentWindow = new Window(parent); if (parentWindow.ClassName == NativeMethods.SystemWindowClasses.Dialog) { fileDialog = wnd; break; } } } } // if we found the dialog if (fileDialog != null) { OldWinProc = NativeMethods.User32.GetWindowLong(fileDialog.Handle, NativeMethods.GWL_WNDPROC); NativeMethods.User32.SetWindowLong(fileDialog.Handle, NativeMethods.GWL_WNDPROC, Marshal.GetFunctionPointerForDelegate(new WindowProc(WndProc)).ToInt32()); } } And the windowproc: public IntPtr WndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam) { lock (this) { if (!handled) { if (msg == NativeMethods.WM_COMMAND || msg == NativeMethods.WM_CLOSE) { // adding to a list. i never access the window via the hwnd from this list, i just treat it as a number _addDescriptor(hWnd); handled = true; } } } return NativeMethods.User32.CallWindowProc(OldWinProc, hWnd, msg, wParam, lParam); } This all works well under normal conditions. But I am seeing two instances of bad behavior in order of badness: If I do not close the dialog within a minute or so, the app crashes. Is this because the thread is getting garbage collected? This would kind of make sense, as far as GC can tell the thread is done? If this is the case, (and I don't know that it is), how can I make the thread stay around as long as the dialog is around? If I immediately close the dialog with the 'X' button (WM_CLOSE) the app crashes. I believe its crashing in the windowproc, but I can't get a breakpoint in there. I'm getting an AccessViolationException, The exception says "Attempted to read or write protected memory. This is often an indication that other memory is corrupt." Its a race condition, but of what I don't know. FYI, I had been reseting the old windowproc once I processed the commands, but that was crashing even more often! Any ideas on how I can solve these issues?

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  • What could cause this difference in behaviour from iphone OS3.0 to iOS4.0?

    - by frankodwyer
    I am getting a strange EXC_BAD_ACCESS error when running my app on iOS4. The app has been pretty solid on OS3.x for some time - not even seeing crash logs in this area of the code (or many at all) in the wild. I've tracked the error down to this code: main class: - (void) sendPost:(PostRequest*)request { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; NSURLResponse* response; NSError* error; NSData *serverReply = [NSURLConnection sendSynchronousRequest:request.request returningResponse:&response error:&error]; ServerResponse* serverResponse=[[ServerResponse alloc] initWithResponse:response error:error data:serverReply]; [request.objectToNotifyWhenDone performSelectorOnMainThread:request.targetToNotifyWhenDone withObject:serverResponse waitUntilDone:YES]; [pool drain]; } (Note: sendPost is run on a separate thread for each invocation of it. PostRequest is just a class to encapsulate a request and a selector to notify when complete) ServerResponse.m: @synthesize response; @synthesize replyString; @synthesize error; @synthesize plist; - (ServerResponse*) initWithResponse:(NSURLResponse*)resp error:(NSError*)err data:(NSData*)serverReply { self.response=resp; self.error=err; self.plist=nil; self.replyString=nil; if (serverReply) { self.replyString = [[[NSString alloc] initWithBytes:[serverReply bytes] length:[serverReply length] encoding: NSASCIIStringEncoding] autorelease]; NSPropertyListFormat format; NSString *errorStr; plist = [NSPropertyListSerialization propertyListFromData:serverReply mutabilityOption:NSPropertyListImmutable format:&format errorDescription:&errorStr]; } return self; } ServerResponse.h: @property (nonatomic, retain) NSURLResponse* response; @property (nonatomic, retain) NSString* replyString; @property (nonatomic, retain) NSError* error; @property (nonatomic, retain) NSDictionary* plist; - (ServerResponse*) initWithResponse:(NSURLResponse*)response error:(NSError*)error data:(NSData*)serverReply; This reliably crashes with a bad access in the line: self.error=err; ...i.e. in the synthesized property setter! I'm stumped as to why this should be, given the code worked on the previous OS and hasn't changed since (even the binary compiled with the previous SDK crashes the same way, but not on OS3.0) - and given it is a simple property method. Any ideas? Could the NSError implementation have changed between releases or am I missing something obvious?

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  • Login Script for PostGreSQL and PHP not working =[

    - by MrEnder
    Ok I'm quite new at logins what not so bare with me here lol but I gota learn so don't discourage me. I tried this so far <?php $error = ""; $conn = pg_connect("host=localhost dbname=brittains_db user=brittains password=XXXX" ); $sql = "SELECT * FROM logins"; $result = pg_query($conn, $sql); if($_SERVER["REQUEST_METHOD"] == "GET") { $userName=""; $password=""; } else if($_SERVER["REQUEST_METHOD"] == "POST") { $userName=trim($_POST["userNameLogin"]); $password=trim($_POST["passwordLogin"]); if(pg_fetch_result($results, $userName, "userName")==true && pg_fetch_result($results, $password, "userName")==true) { setcookie("userIDforDV", $userName, time()+43200); } else { $error = "Your username and or password is incorrect"; } } $userName = $_COOKIE['userIDforDV']; if(isset($userName) && $userName!="") { echo "Welcome " . $userName; } echo $error; ?> <form> <table> <tr> <td class="signupTd"> User Name:&nbsp; </td> <td> <input type="text" name="userNameLogin" value="" size="20" /> </td> </tr> <tr> <td class="signupTd"> Password:&nbsp; </td> <td> <input type="password" name="passwordLogin" value="" size="20" /> </td> </tr> <tr> <td class="signupTd" colspan="2"> <input type="submit" name="submit" value="Submit"/> </td> </tr> </table> </form> that was the idea I came up with... but its prolly a really bad idea and it doesn't work... how might I go about this properly? I need really detailed descriptions please. Thanks a tun Shelby

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  • Is the Scala 2.8 collections library a case of "the longest suicide note in history" ?

    - by oxbow_lakes
    First note the inflammatory subject title is a quotation made about the manifesto of a UK political party in the early 1980s. This question is subjective but it is a genuine question, I've made it CW and I'd like some opinions on the matter. Despite whatever my wife and coworkers keep telling me, I don't think I'm an idiot: I have a good degree in mathematics from the University of Oxford and I've been programming commercially for almost 12 years and in Scala for about a year (also commercially). I have just started to look at the Scala collections library re-implementation which is coming in the imminent 2.8 release. Those familiar with the library from 2.7 will notice that the library, from a usage perspective, has changed little. For example... > List("Paris", "London").map(_.length) res0: List[Int] List(5, 6) ...would work in either versions. The library is eminently useable: in fact it's fantastic. However, those previously unfamiliar with Scala and poking around to get a feel for the language now have to make sense of method signatures like: def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That For such simple functionality, this is a daunting signature and one which I find myself struggling to understand. Not that I think Scala was ever likely to be the next Java (or /C/C++/C#) - I don't believe its creators were aiming it at that market - but I think it is/was certainly feasible for Scala to become the next Ruby or Python (i.e. to gain a significant commercial user-base) Is this going to put people off coming to Scala? Is this going to give Scala a bad name in the commercial world as an academic plaything that only dedicated PhD students can understand? Are CTOs and heads of software going to get scared off? Was the library re-design a sensible idea? If you're using Scala commercially, are you worried about this? Are you planning to adopt 2.8 immediately or wait to see what happens? Steve Yegge once attacked Scala (mistakenly in my opinion) for what he saw as its overcomplicated type-system. I worry that someone is going to have a field day spreading fud with this API (similarly to how Josh Bloch scared the JCP out of adding closures to Java). Note - I should be clear that, whilst I believe that Josh Bloch was influential in the rejection of the BGGA closures proposal, I don't ascribe this to anything other than his honestly-held beliefs that the proposal represented a mistake.

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  • What is the best workaround for the WCF client `using` block issue?

    - by Eric King
    I like instantiating my WCF service clients within a using block as it's pretty much the standard way to use resources that implement IDisposable: using (var client = new SomeWCFServiceClient()) { //Do something with the client } But, as noted in this MSDN article, wrapping a WCF client in a using block could mask any errors that result in the client being left in a faulted state (like a timeout or communication problem). Long story short, when Dispose() is called, the client's Close() method fires, but throws and error because it's in a faulted state. The original exception is then masked by the second exception. Not good. The suggested workaround in the MSDN article is to completely avoid using a using block, and to instead instantiate your clients and use them something like this: try { ... client.Close(); } catch (CommunicationException e) { ... client.Abort(); } catch (TimeoutException e) { ... client.Abort(); } catch (Exception e) { ... client.Abort(); throw; } Compared to the using block, I think that's ugly. And a lot of code to write each time you need a client. Luckily, I found a few other workarounds, such as this one on IServiceOriented. You start with: public delegate void UseServiceDelegate<T>(T proxy); public static class Service<T> { public static ChannelFactory<T> _channelFactory = new ChannelFactory<T>(""); public static void Use(UseServiceDelegate<T> codeBlock) { IClientChannel proxy = (IClientChannel)_channelFactory.CreateChannel(); bool success = false; try { codeBlock((T)proxy); proxy.Close(); success = true; } finally { if (!success) { proxy.Abort(); } } } } Which then allows: Service<IOrderService>.Use(orderService => { orderService.PlaceOrder(request); } That's not bad, but I don't think it's as expressive and easily understandable as the using block. The workaround I'm currently trying to use I first read about on blog.davidbarret.net. Basically you override the client's Dispose() method wherever you use it. Something like: public partial class SomeWCFServiceClient : IDisposable { void IDisposable.Dispose() { if (this.State == CommunicationState.Faulted) { this.Abort(); } else { this.Close(); } } } This appears to be able to allow the using block again without the danger of masking a faulted state exception. So, are there any other gotchas I have to look out for using these workarounds? Has anybody come up with anything better?

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  • In GWT I'd like to load the main page on www.domain.com and a dynamic page on www.domain.com/xyz - I

    - by Mike Brecht
    Hi, I have a question for which I'm sure there must a simple solution. I'm writing a small GWT application where I want to achieve this: www.domain.com : should serve the welcome page www.domain.com/xyz : should serve page xyz, where xyz is just a key for an item in a database. If there is an item associated with key xyz, I'll load that and show a page, otherwise I'll show a 404 error page. I was trying to modify the web.xml file accordingly but I just couldn't make it work. I could make it work with an url-pattern if the key in question is after another /, for example: www.domain.com/search/xyz. However, I'd like to have the key xyz directly following the root / (http://www.domain.com/xyz). Something like <servlet-mapping> <servlet-name>main</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> doesn't seem to work as I don't know how to address the main page index.html (as it's not an actual servlet) which will then load my main GWT module. I could make it work with a bad work around (see below): Redirecting a 404 exception to index.html and then doing the look up in the main entry point, but I'm sure that's not the best practice, also for SEO purposes. Can anyone give me a hint on how to configure the web.xml with GWT for my purpose? Thanks a lot. Mike Work-around via 404: Web.xml: <web-app> <error-page> <exception-type>404</exception-type> <location>/index.html</location> </error-page> <welcome-file-list> <welcome-file>index.html</welcome-file> </welcome-file-list> </web-app> index.html -- Main Entry point -- onModuleLoad(): String path = Window.Location.getPath(); if (path == null || path.length() == 0 || path.equalsIgnoreCase("/") || path.equalsIgnoreCase("/index.html")) { ... // load main page } else { lookup(path.substring(1)); // that's key xyz

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  • [Struts2+tiles] How can I make title dynamically?

    - by Lee Domin
    I'm developing BBS in struts2 and tiles(2) framework. I want to push a value in ActionSupport class and pop the value in layout.jsp of tiles. but i just keep failing to access to the value. I will explain my works step by step. 1) Users click a link to view an article at list page. And BoardView class will be called as defined in struts.xml --list.jsp-- <a href="view_board?num=${num}"> ${ subject } </a> --struts.xml-- <action name="View_board" class="board.BoardView"> <result type="tiles">board.view</result> </action> 2)Action class will put title into the value stack... right? --BoardView class-- public class BoardView extends ActionSupport private String title; public void Execute() throws Exception { ... setTitle(board.getSubject()); return SUCCESS; } ... (setter and getter of title) 3) As ActionClass returns SUCCESS, it will go to tiles definition named board.view --struts.xml-- <action name="View_board" class="board.BoardView"> <result type="tiles">board.view</result> </action> 4)Here's the tiles-def.xml and the problem. I think the value of 'title' can't be popped from value stack. ==tiles-def.xml== <definition name="board.view" extends="layout"> <put-attribute name="title" value="%title" /> <put-attribute name="body" value="/board/view.jsp" /> </definition> (I can't indent with tags... sorry) Here's the layout.jsp ==layout.jsp== ... <title><tiles:getAsString name="title" /></title> ... I tried to replace the value attribute to %{title}, $title and ${title}. But nothings worked out. Web Browser just shows the string itself($title). I don't know what to do... please help me. I hope you all understand my works despite of my bad explanation.

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  • Experienced developer trying to get outsourcing contract with current client.

    - by Mike
    I work for a major bank as a contract software developer. I've been there a few months, and without exception this place has the worst software practices I've ever seen. The software my team makes has no formal testing, terrible code (not reusable, hard to read, etc), minimal documentation, no defined development process and an absolutely sickening amount of waste due to bureaucratic overhead. Part of my contract is to maintain a group of thousands of very poorly written batch jobs. When one of the jobs fails (read: crashes), it's a developers job to look at the source, figure out what's wrong, fix it, and check it in. There is no quality assurance process or auditing of the results whatsoever. Once the developer says "it works" a manager signs off and it goes into production. What's disturbing is that these jobs essentially grab market data and put it into a third-party risk management system, which provides the bank with critical intelligence. I've discovered the disturbing truth that this has been happening since the 90s and nobody really has evidence the system is getting the correct data! Without going into details, an issue arose on Friday that was so horrible I actually stormed out of the place. I was ready to quit, but I decided to just get out to calm my nerves and possibly go back Monday. I've been reflecting today on how to handle this. I have realized that, in probably less than 6 months, I could (with 2 other developers) remake a large component of this system. The new system would provide them with, as primary benefits, a maintainable codebase less prone to error and a solid QA framework. To do it properly I would have to be outside the bank, the internal bureaucracy is just too much. And moreover, I think a bank is fundamentally not a place that can make good software. This is my plan. Write a report explaining in depth all the problems with their current system Explain why their software practices fail and generate a tremendous amount of error and waste. Use this as the basis for claiming the project must be developed externally. Write a high level development plan, including what resources I will require Hand 1,2,3 to my manager, hopefully he passes it up the chain. Worst case he fires me, but this isn't so bad. Convinced Executive decides to award my company a contract for the new system I have 8 years experience as a software contractor and have delivered my share of successful software products, but all working in-house for small/medium sized companies. When I read this over, I think I have a dynamite plan. But since this is the first time doing something this bold so I have my doubts. My question is, is this a good idea? If you think not, please spare no detail.

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  • Alternatives to requiring users to register for an account?

    - by jamieb
    I'm working on a side project to build a new web app idea of mine. For the sake of discussion, let's say this app displays a random photograph of a famous work of art. On a scale of 1 to 5, users are asked to rate how well they like each piece of art, and then are shown the next photo. Eventually, the app is able to get an sense of the person's style and is able to recommend artwork that he/she may find pleasing. The whole concept is similar to Netflix. I understand how to do all the preference matching logic (although not as sophisticated as Netflix). But I'd like to find a way to do this without requiring that users create an account first. This is a novelty website that a typical user might use only a handful of times. Requiring registration is overkill and will likely drastically reduce it's utility. I'd like to allow people to begin rating artwork within five seconds of their initial pageview, yet maintain the integrity of the voting (since recommendations are predicated on how other people have rated the various pieces of artwork). Can it be done? Some ideas: OpenID. The perfect solution except for the fact that it's not wildly used and my target audience isn't the most technically adept demographic. Text message. User inputs phone number and is texted a four digit code to key into the web app. Quick, easy, and great way to limit abuse. However, privacy concerns abound... people are probably even less likely to give me their phone number than their email address. Facebook login. I personally don't have a Facebook account due to privacy concerns. And I'd really hate to support such a proprietary platform. Hash code/Bookmark. Vistor's initial pageview generates a 5 or 6 digit alphanumeric code that is embedded in each subsequent URL. They can bookmark any page to save their state. Good: Very simple system that doesn't require any user action. Bad: Very easy to stuff the ballot box, might be difficult to account for users sharing the link containing their ID code via email or social networking sites.

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  • Putting update logic in your migrations

    - by Daniel Abrahamsson
    A couple of times I've been in the situation where I've wanted to refactor the design of some model and have ended up putting update logic in migrations. However, as far as I've understood, this is not good practice (especially since you are encouraged to use your schema file for deployment, and not your migrations). How do you deal with these kind of problems? To clearify what I mean, say I have a User model. Since I thought there would only be two kinds of users, namely a "normal" user and an administrator, I chose to use a simple boolean field telling whether the user was an adminstrator or not. However, after I while I figured I needed some third kind of user, perhaps a moderator or something similar. In this case I add a UserType model (and the corresponding migration), and a second migration for removing the "admin" flag from the user table. And here comes the problem. In the "add_user_type_to_users" migration I have to map the admin flag value to a user type. Additionally, in order to do this, the user types have to exist, meaning I can not use the seeds file, but rather create the user types in the migration (also considered bad practice). Here comes some fictional code representing the situation: class CreateUserTypes < ActiveRecord::Migration def self.up create_table :user_types do |t| t.string :name, :nil => false, :unique => true end #Create basic types (can not put in seed, because of future migration dependency) UserType.create!(:name => "BASIC") UserType.create!(:name => "MODERATOR") UserType.create!(:name => "ADMINISTRATOR") end def self.down drop_table :user_types end end class AddTypeIdToUsers < ActiveRecord::Migration def self.up add_column :users, :type_id, :integer #Determine type via the admin flag basic = UserType.find_by_name("BASIC") admin = UserType.find_by_name("ADMINISTRATOR") User.all.each {|u| u.update_attribute(:type_id, (u.admin?) ? admin.id : basic.id)} #Remove the admin flag remove_column :users, :admin #Add foreign key execute "alter table users add constraint fk_user_type_id foreign key (type_id) references user_types (id)" end def self.down #Re-add the admin flag add_column :users, :admin, :boolean, :default => false #Reset the admin flag (this is the problematic update code) admin = UserType.find_by_name("ADMINISTRATOR") execute "update users set admin=true where type_id=#{admin.id}" #Remove foreign key constraint execute "alter table users drop foreign key fk_user_type_id" #Drop the type_id column remove_column :users, :type_id end end As you can see there are two problematic parts. First the row creation part in the first model, which is necessary if I would like to run all migrations in a row, then the "update" part in the second migration that maps the "admin" column to the "type_id" column. Any advice?

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  • How to fine tune a Membership Provider?

    - by Venemo
    After all the answers to my last question about fine-tuning turned out to be more useful than I expected, I thought that I would ask another similar Question about the MembershipProviders as well. Okay, so firstly, to clarify: I know what a Membership, Role, and Profile provider is, how to implement my own, and how to configure them, and most of the things about them. Implementing a role and profile provider is pretty straightforward, because they only require simple CRUD most of the time. (A single line of LINQ is enough for about half of the RoleProvider's methods.) However, the Membership provider is a differend beast. Many of you may realize that it violates the SR (Single Responsibility) principle, because it has to do EVERYTHING related to user management. While this leaves a lot of room for customizations, it has its downsides as well. There is no information on the Internet about what their EXACT expected behaviour is, such as when should they throw exceptions or simply return null, and stuff like that. I use this sample implementation for reference, but it also contains several contradictions. For example, it uses its own ValidateUser method for checking for credentials in the ChangePassword method. But the ValidateUser also updates the user's LastLoginDate to the current date. So, does the framework expect that I set it in my own provider as well, or is it simply a mistake in the sample? The other is: the ChangePassword method throws an exception every time when validating the new password, but CreateUser doesn't ever throw an exception, it simply returns false. And last, but not least: it counts the invalid password attempts of the user and locks them if it passes a threshold. While this is good, but it requires manual action to unlock the users. Is it a problem if my provider automatically unlocks the user after a certain amount of time? (EDIT) I almost forgot: the CreateUser method in the sample inserts the ID from the method parameter. I actually think this is bad practice, because I use inters with auto incement as IDs, so inserting them from some method parameter is not an option. Should I just ignore the parameter, or require that its value is null and throw an exception if it isn't? All in all, does ASP.NET have any assumptions about the behaviour of a MembershipProvider? Is there any documentation which describes when should I throw an exception or just return null? I also tried to find a set of generic unit tests which would provide some guidance about the expected behaviour, but no luck, I found plenty of articles about "Unit testing is good", and "How to unit test a MembershipProvider", but not one where there would be any actual tests. Thanks in advance for everyone!

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