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  • What does the `forall` keyword in Haskell/GHC do?

    - by JUST MY correct OPINION
    I've been banging my head on this one for (quite literally) years now. I'm beginning to kinda/sorta understand how the foreach keyword is used in so-called "existential types" like this: data ShowBox = forall s. Show s => SB s (This despite the confusingly-worded explanations of it in the fragments found all around the web.) This is only a subset, however, of how foreach is used and I simply cannot wrap my mind around its use in things like this: runST :: forall a. (forall s. ST s a) -> a Or explaining why these are different: foo :: (forall a. a -> a) -> (Char,Bool) bar :: forall a. ((a -> a) -> (Char, Bool)) Or the whole RankNTypes stuff that breaks my brain when "explained" in a way that makes me want to do that Samuel L. Jackson thing from Pulp Fiction. (Don't follow that link if you're easily offended by strong language.) The problem, really, is that I'm a dullard. I can't fathom the chicken scratchings (some call them "formulae") of the elite mathematicians that created this language seeing as my university years are over two decades behind me and I never actually had to put what I learnt into use in practice. I also tend to prefer clear, jargon-free English rather than the kinds of language which are normal in academic environments. Most of the explanations I attempt to read on this (the ones I can find through search engines) have these problems: They're incomplete. They explain one part of the use of this keyword (like "existential types") which makes me feel happy until I read code that uses it in a completely different way (like runST, foo and bar above). They're densely packed with assumptions that I've read the latest in whatever branch of discrete math, category theory or abstract algebra is popular this week. (If I never read the words "consult the paper whatever for details of implementation" again, it will be too soon.) They're written in ways that frequently turn even simple concepts into tortuously twisted and fractured grammar and semantics. (I suspect that the last two items are the biggest problem. I wouldn't know, though, since I'm too much a dullard to comprehend them.) It's been asked why Haskell never really caught on in industry. I suspect, in my own humble, unintelligent way, that my experience in figuring out one stupid little keyword -- a keyword that is increasingly ubiquitous in the libraries being written these days -- are also part of the answer to that question. It's hard for a language to catch on when even its individual keywords cause years-long quests to comprehend. Years-long quests which end in failure. So... On to the actual question. Can anybody completely explain the foreach keyword in clear, plain English (or, if it exists somewhere, point to such a clear explanation which I've missed) that doesn't assume I'm a mathematician steeped in the jargon?

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  • Spring MVC working with Web Designers

    - by jboyd
    When working with web-designers in a Spring-MVC and JSP environment, are there any tools or helpful patterns to reduce the pain of going back and forth from HTML to JSP and back? Project requirements dictate that views will change often, and it can be difficult to make changes efficiently because of the amount of Java code that leaks into the view layer. Ideally I'd like to remove almost all Java code from the view, but it does not seem like this works with the Spring/JSP philosophy where often the way to remove Java code is to replace that code with tag libraries, which will still have a similar problem. To provide a little clarity to my question I'm going to include some existing code (inherited by me) to show the kinds of problems I'm likely to face when change the look of our views: <%-- Begin looping through results --%> <% List memberList = memberSearchResults.getResults(); for(int i = start - 1; i < memberList.size() && i < end; i++) { Profile profile = (Profile)memberList.get(i); long profileId = profile.getProfileId(); String nickname = profile.getNickname(); String description = profile.getDescription(); Image image = profile.getAvatarImage(); String avatarImageSrc = null; int avatarImageWidthNum = 0; int avatarImageHeightNum = 0; if(null != image) { avatarImageSrc = image.getSrc(); avatarImageWidthNum = image.getWidth(); avatarImageHeightNum = image.getHeight(); } String bgColor = i % 2 == 1 ? "background-color:#FFF" : ""; %> <div style="float:left;clear:both;padding:5px 0 5px 5px;cursor:pointer;<%= bgColor %>" onclick='window.location="profile.sp?profileId=<%= profileId %>"'> <div style="float:right;clear:right;padding-left:10px;width:515px;font-size:10px;color:#7e7e7e"> <h6><%= nickname %></h6> <%= description %> </div> <img style="float:left;clear:left;" alt="Avatar Image" src="<%= null != avatarImageSrc && avatarImageSrc.trim().length() > 0 ? avatarImageSrc : "images/defaultUserImage.png" %>" <%= avatarImageWidthNum < avatarImageHeightNum ? "height='59'" : "width='92'" %> /> </div> <% } // End loop %> Now, ignoring some of the code smells there, it's obvious that if someone wants to change the look of that DIV it would be neccesary to re-place all the Java/JSP code into the new HTML given (the designers don't work in JSP files, they have their own HTML versions of the website). Which is tedious, and prone to errors.

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  • Opinions on Dual-Salt authentication for low sensitivity user accounts?

    - by Heleon
    EDIT - Might be useful for someone in the future... Looking around the bcrypt class in php a little more, I think I understand what's going on, and why bcrypt is secure. In essence, I create a random blowfish salt, which contains the number of crypt rounds to perform during the encryption step, which is then hashed using the crypt() function in php. There is no need for me to store the salt I used in the database, because it's not directly needed to decrypt, and the only way to gain a password match to an email address (without knowing the salt values or number of rounds) would be to brute force plain text passwords against the hash stored in the database using the crypt() function to verify, which, if you've got a strong password, would just be more effort than it's worth for the user information i'm storing... I am currently working on a web project requiring user accounts. The application is CodeIgniter on the server side, so I am using Ion Auth as the authentication library. I have written an authentication system before, where I used 2 salts to secure the passwords. One was a server-wide salt which sat as an environment variable in the .htaccess file, and the other was a randomly generated salt which was created at user signup. This was the method I used in that authentication system for hashing the password: $chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; //create a random string to be used as the random salt for the password hash $size = strlen($chars); for($i = 0; $i < 22; $i++) { $str .= $chars[rand(0, $size - 1)]; } //create the random salt to be used for the crypt $r_blowfish_salt = "$2a$12$" . $str . "$"; //grab the website salt $salt = getenv('WEBSITE_SALT'); //combine the website salt, and the password $password_to_hash = $pwd . $salt; //crypt the password string using blowfish $password = crypt($password_to_hash, $r_blowfish_salt); I have no idea whether this has holes in it or not, but regardless, I moved over to Ion Auth for a more complete set of functions to use with CI. I noticed that Ion only uses a single salt as part of its hashing mechanism (although does recommend that encryption_key is set in order to secure the database session.) The information that will be stored in my database is things like name, email address, location by country, some notes (which will be recommended that they do not contain sensitive information), and a link to a Facebook, Twitter or Flickr account. Based on this, i'm not convinced it's necessary for me to have an SSL connection on the secure pages of my site. My question is, is there a particular reason why only 1 salt is being used as part as the Ion Auth library? Is it implied that I write my own additional salting in front of the functionality it provides, or am I missing something? Furthermore, is it even worth using 2 salts, or once an attacker has the random salt and the hashed password, are all bets off anyway? (I assume not, but worth checking if i'm worrying about nothing...)

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  • Trouble with datasource not being called from viewWillAppear

    - by user278859
    A little background. I have taken GCCalendar which only works in portrait orientation and extended it to work in landscape similar to how the iPhone's Calendar app works. I did this by duplicating the main view class and modifying it to work in landscape. So when the phone is in portrait orientation the CGCalendar is instantiated from the apps main view controller using the original portrait view class and when in landscape orientation using the new modified landscape view class. Most of the other classes in GCCalendar are shared without modification. A few had to be duplicated as well. I got it all working great except for an issue with the datasource. The datasource is called when the calendar is first loaded and each time the user changes the dates being viewed. Problem is I can't get the datasource call to work on the first call. I am stumped as it works fine in portrait orientation and I cannot find any difference between the 2 versions. Following is some of the code that shows how it gets to the datasource call the first time. Subsequent calls removes all the calendar subviews and instantiates them again with the new dates. The duplicated landscape class names end in LS. Otherwise as you can see they are identical. Does anyone has any idea of where else I might look to resolve this issue? Thanks, John -------------------------------- //App main view controller - (void)showLandscapeCalendar { GCCalendarLandscapeView *calendar = [[[GCCalendarLandscapeView alloc] init] autorelease]; calendar.dataSource = self; calendar.delegate = self; navigationController = [[UINavigationController alloc] initWithRootViewController:calendar]; [self presentModalViewController:navigationController animated:YES]; } - (void)showPortraitCalendar { GCCalendarPortraitView *calendar = [[[GCCalendarPortraitView alloc] init] autorelease]; calendar.dataSource = self; calendar.delegate = self; navigationController = [[UINavigationController alloc] initWithRootViewController:calendar]; [self presentModalViewController:navigationController animated:YES]; } - (NSArray *)calendarEventsForDate:(NSDate *)date{ //build and return the events array //this is the protocol datasource method //It is supposed to run every time the date changes in the calendar } ------------------------------- // GCCalendarLandscapeView... - (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; if (viewDirty) { [self reloadDayAnimated:NO context:NULL]; viewDirty = NO; } viewVisible = YES; } - (void)reloadDayAnimated:(BOOL)animated context:(void *)context { GCCalendarDayViewLS *nextDayView = [[GCCalendarDayViewLS alloc] initWithCalendarView:self]; } ------------------------------- //GCCalendarDayViewLS - (id)initWithCalendarView:(GCCalendarView *)view { if (self = [super init]) { dataSource = view.dataSource; } return self; } - (void)reloadData { //** first time through the dataSource method does not run events = [dataSource calendarEventsForDate:date]; } ------------------------------- // GCCalendarPortraitView... - (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; if (viewDirty) { [self reloadDayAnimated:NO context:NULL]; viewDirty = NO; } viewVisible = YES; } - (void)reloadDayAnimated:(BOOL)animated context:(void *)context { GCCalendarDayView *nextDayView = [[GCCalendarDayView alloc] initWithCalendarView:self]; } ------------------------------- //GCCalendarDayView - (id)initWithCalendarView:(GCCalendarView *)view { if (self = [super init]) { dataSource = view.dataSource; } return self; } - (void)reloadData { **//this one works every time events = [dataSource calendarEventsForDate:date]; }

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  • Why doesn't my QsciLexerCustom subclass work in PyQt4 using QsciScintilla?

    - by Jon Watte
    My end goal is to get Erlang syntax highlighting in QsciScintilla using PyQt4 and Python 2.6. I'm running on Windows 7, but will also need Ubuntu support. PyQt4 is missing the necessary wrapper code for the Erlang lexer/highlighter that "base" scintilla has, so I figured I'd write a lightweight one on top of QsciLexerCustom. It's a little bit problematic, because the Qsci wrapper seems to really want to talk about line+index rather than offset-from-start when getting/setting subranges of text. Meanwhile, the lexer gets arguments as offset-from-start. For now, I get a copy of the entire text, and split that up as appropriate. I have the following lexer, and I apply it with setLexer(). It gets all the appropriate calls when I open a new file and sets this as the lexer, and prints a bunch of appropriate lines based on what it's doing... but there is no styling in the document. I tried making all the defined styles red, and the document is still stubbornly black-on-white, so apparently the styles don't really "take effect" What am I doing wrong? If nobody here knows, what's the appropriate discussion forum where people might actually know these things? (It's an interesting intersection between Python, Qt and Scintilla, so I imagine the set of people who would know is small) Let's assume prefs.declare() just sets up a dict that returns the value for the given key (I've verified this -- it's not the problem). Let's assume scintilla is reasonably properly constructed into its host window QWidget. Specifically, if I apply a bundled lexer (such as QsciLexerPython), it takes effect and does show styled text. prefs.declare('font.name.margin', "MS Dlg") prefs.declare('font.size.margin', 8) prefs.declare('font.name.code', "Courier New") prefs.declare('font.size.code', 10) prefs.declare('color.editline', "#d0e0ff") class LexerErlang(Qsci.QsciLexerCustom): def __init__(self, obj = None): Qsci.QsciLexerCustom.__init__(self, obj) self.sci = None self.plainFont = QtGui.QFont() self.plainFont.setPointSize(int(prefs.get('font.size.code'))) self.plainFont.setFamily(prefs.get('font.name.code')) self.marginFont = QtGui.QFont() self.marginFont.setPointSize(int(prefs.get('font.size.code'))) self.marginFont.setFamily(prefs.get('font.name.margin')) self.boldFont = QtGui.QFont() self.boldFont.setPointSize(int(prefs.get('font.size.code'))) self.boldFont.setFamily(prefs.get('font.name.code')) self.boldFont.setBold(True) self.styles = [ Qsci.QsciStyle(0, QtCore.QString("base"), QtGui.QColor("#000000"), QtGui.QColor("#ffffff"), self.plainFont, True), Qsci.QsciStyle(1, QtCore.QString("comment"), QtGui.QColor("#008000"), QtGui.QColor("#eeffee"), self.marginFont, True), Qsci.QsciStyle(2, QtCore.QString("keyword"), QtGui.QColor("#000080"), QtGui.QColor("#ffffff"), self.boldFont, True), Qsci.QsciStyle(3, QtCore.QString("string"), QtGui.QColor("#800000"), QtGui.QColor("#ffffff"), self.marginFont, True), Qsci.QsciStyle(4, QtCore.QString("atom"), QtGui.QColor("#008080"), QtGui.QColor("#ffffff"), self.plainFont, True), Qsci.QsciStyle(5, QtCore.QString("macro"), QtGui.QColor("#808000"), QtGui.QColor("#ffffff"), self.boldFont, True), Qsci.QsciStyle(6, QtCore.QString("error"), QtGui.QColor("#000000"), QtGui.QColor("#ffd0d0"), self.plainFont, True), ] print("LexerErlang created") def description(self, ix): for i in self.styles: if i.style() == ix: return QtCore.QString(i.description()) return QtCore.QString("") def setEditor(self, sci): self.sci = sci Qsci.QsciLexerCustom.setEditor(self, sci) print("LexerErlang.setEditor()") def styleText(self, start, end): print("LexerErlang.styleText(%d,%d)" % (start, end)) lines = self.getText(start, end) offset = start self.startStyling(offset, 0) print("startStyling()") for i in lines: if i == "": self.setStyling(1, self.styles[0]) print("setStyling(1)") offset += 1 continue if i[0] == '%': self.setStyling(len(i)+1, self.styles[1]) print("setStyling(%)") offset += len(i)+1 continue self.setStyling(len(i)+1, self.styles[0]) print("setStyling(n)") offset += len(i)+1 def getText(self, start, end): data = self.sci.text() print("LexerErlang.getText(): " + str(len(data)) + " chars") return data[start:end].split('\n') Applied to the QsciScintilla widget as follows: _lexers = { 'erl': (Q.SCLEX_ERLANG, LexerErlang), 'hrl': (Q.SCLEX_ERLANG, LexerErlang), 'html': (Q.SCLEX_HTML, Qsci.QsciLexerHTML), 'css': (Q.SCLEX_CSS, Qsci.QsciLexerCSS), 'py': (Q.SCLEX_PYTHON, Qsci.QsciLexerPython), 'php': (Q.SCLEX_PHP, Qsci.QsciLexerHTML), 'inc': (Q.SCLEX_PHP, Qsci.QsciLexerHTML), 'js': (Q.SCLEX_CPP, Qsci.QsciLexerJavaScript), 'cpp': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'h': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'cxx': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'hpp': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'c': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'hxx': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'tpl': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'xml': (Q.SCLEX_XML, Qsci.QsciLexerXML), } ... inside my document window class ... def addContentsDocument(self, contents, title): handler = self.makeScintilla() handler.title = title sci = handler.sci sci.append(contents) self.tabWidget.addTab(sci, title) self.tabWidget.setCurrentWidget(sci) self.applyLexer(sci, title) EventBus.bus.broadcast('command.done', {'text': 'Opened ' + title}) return handler def applyLexer(self, sci, title): (language, lexer) = language_and_lexer_from_title(title) if lexer: l = lexer() print("making lexer: " + str(l)) sci.setLexer(l) else: print("setting lexer by id: " + str(language)) sci.SendScintilla(Qsci.QsciScintillaBase.SCI_SETLEXER, language) linst = sci.lexer() print("lexer: " + str(linst)) def makeScintilla(self): sci = Qsci.QsciScintilla() sci.setUtf8(True) sci.setTabIndents(True) sci.setIndentationsUseTabs(False) sci.setIndentationWidth(4) sci.setMarginsFont(self.smallFont) sci.setMarginWidth(0, self.smallFontMetrics.width('00000')) sci.setFont(self.monoFont) sci.setAutoIndent(True) sci.setBraceMatching(Qsci.QsciScintilla.StrictBraceMatch) handler = SciHandler(sci) self.handlers[sci] = handler sci.setMarginLineNumbers(0, True) sci.setCaretLineVisible(True) sci.setCaretLineBackgroundColor(QtGui.QColor(prefs.get('color.editline'))) return handler Let's assume the rest of the application works, too (because it does :-)

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  • PHP hooks information and help needed

    - by sea_1987
    Background I am realtively new to hooks, and I have been asked to use a hook to populate a view with some data, currently the view gathers it data from a function that is in the model, and becuase the whole object is being passed to the view I can access the function. The function looks like this, public function numCVInSector($k) { $this->load->model('SYSector'); $sectorModel = new SYSector(); $cvs = $sectorModel->fetchRelatedCV($k); $cvs = $cvs[0]['count']; if($cvs == "0") { return false; } else { return $cvs; } } it call's a query in the model that looks like this, public function fetchRelatedCV($k) { $sql = "SELECT sector_id, COUNT(sector_id) as count FROM sy_user_sectors WHERE sector_id = $k"; //print_r($sql); $query = $this->db->query($sql); return $query->result_array(); } $k is the id of element that is in the view. The Problem I have been asked to use a hook that is in the parent of the model the hook is called post populate, now I have very little idea of what a hook is or how to use one to implement my function. Could some one give me some advice, the code where the hook is original made looks like this, public function populate($where = array()) { $results = array( "success" => false, "is_error" => false, "error_code" => "", "error_message" => "" ); if(empty($where) && empty($this->aliases['id'])){ $results['is_error'] = true; $results['error_message'] = 'No criteria.'; return $results; } // [hook] $this->prePopulate(); $where = count($where) > 0 ? $where : array('id' => $this->aliases['id']); $query = $this->db->get_where($this->tableName, $where, 1); if($query->num_rows() < 1){ $results['error_message'] = 'Empty results.'; return $results; } foreach($query->result_array() as $row){ foreach($this->aliases as $key => $val){ $this->aliases[$key] = $row[$key]; } } // [hook] $this->postPopulate(); // Presume success $results['success'] = true; return $results; } I have been asked to use the postPopulate hook. public function postPopulate() { $args = $this->getHookArgs('post_populate'); if(!is_array($args)){ // $this->fb->log($args, 'bad args'); return false; } // code here... // Convert dates to front end formats. foreach($this->frontEndDateFields as $fieldName => $dateFormat){ $dateRes = mlib_du_getFormattedMySQLDate($this->aliases[$fieldName], $dateFormat); if($dateRes != false){ $this->aliases[$fieldName] = $dateRes; } } return true; }

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  • ASP.NET MVC - Form Post always redirect when I just want to bind json result to a div

    - by Saxman
    Hi all, I'm having a little problem with json result. I'm submitting a contact form, and after the submission, I just want to return some json data (indicating either a success or failed and displays a message) back to the view, without causing a redirect, but it kept redirecting me to the action, here are the codes: HTML <div id="contactForm2" class="grid_6"> <div id="contactFormContainer"> @using (Html.BeginForm(MVC.Home.ActionNames.ContactForm, MVC.Home.Name, FormMethod.Post, new { id = "contactForm" })) { <p> <input type="text" tabindex="1" size="22" value="" id="contactName" class="text_input required" name="contactName" /> <label for="contactName"> <strong class="leftSpace">Your Name (required)</strong></label></p> <p> <input type="text" tabindex="2" size="22" value="" id="contactEmail" class="text_input required" name="contactEmail" /> <label for="contactEmail"> <strong class="leftSpace">Email (required)</strong></label></p> <p> <input type="text" tabindex="2" size="22" value="" id="contactPhone" class="text_input" name="contactPhone" /> <label for="contactPhone"> <strong class="leftSpace">Phone</strong></label></p> <p> <label> <strong class="leftSpace n">Message (required)</strong></label> <textarea tabindex="4" rows="4" cols="56" id="contactMessage" class="text_area required" name="contactMessage"></textarea></p> <p> <input type="submit" value="Send" tabindex="5" id="contactSubmit" class="button submit" name="contactSubmit" /></p> } </div> <div id="contactFormStatus"> </div> </div> Controller [HttpPost] public virtual JsonResult ContactForm(FormCollection formCollection) { var name = formCollection["contactName"]; var email = formCollection["contactEmail"]; var phone = formCollection["contactPhone"]; var message = formCollection["contactMessage"]; if (string.IsNullOrEmpty(name) || string.IsNullOrEmpty(email) || string.IsNullOrEmpty(message)) { return Json(new { success = false, message = "Please complete all the required fields so that I can get back to you. Thanks." }); } // Insert contact form data here... return Json(new { success = true, message = "Your inquery has been sent. Thank you." }); } javascript $(document).ready(function () { $('#contactSubmit').live('click', function () { var form = $('#contactForm'); var formData = form.serialize(); $.post('/Home/ContactForm', formData, function (result) { var status = $('#contactFormStatus'); if (result.success) { $('#contactForm')[0].reset; } status.append(result.message); }, 'json' ); return false; }); }); I've also tried this javascript, but also got a redirect $(document).ready(function () { $('#contactSubmit').live('click', function () { var form = $('#contactForm'); var formData = form.serialize(); $.ajax({ type: 'POST', url: '/Home/ContactForm', data: formData, success: function (result) { SubmitContactResult(result); }, cache: false }); }); function SubmitContactResult(result) { var status = $('#contactFormStatus'); if (result.success) { $('#contactForm')[0].reset; } status.append(result.message); } }); Any idea what's going on with my code? Thank you very much.

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  • Modern alternatives to Java

    - by Ralph
    I have been a Java developer for 14 years and have written an enterprise-level (~500 kloc) Swing application that uses most of the standard library APIs. Recently, I have become disappointed with the progress that the language has made to "modernize" itself, and am looking for an alternative for ongoing development. I have considered moving to the .NET platform, but I have issues with using something the only runs well in Windows (I know about Mono, but that is still far behind Microsoft). I also plan on buying a new Macbook Pro as soon as Apple releases their new rumored Arrandale-based machines and want to develop in an environment that will feel "at home" in Unix/Linux. I have considered using Python or Ruby, but the standard Java library is arguably the largest of any modern language. In JVM-based languages, I looked at Groovy, but am disappointed with its performance. Rumor has it that with the soon-to-be released JDK7, with its InvokeDynamic instruction, this will improve, but I don't know how much. Groovy is also not truly a functional language, although it provides closures and some of the "functional" features on collections. It does not embrace immutability. I have narrowed my search down to two JVM-based alternatives: Scala and Clojure. Each has its strengths and weaknesses. I am looking for opinions. I am not an expert at either of these languages; I have read 2 1/2 books on Scala and am currently reading Stu Halloway's book on Clojure. Scala is strongly statically typed. I know the dynamic language folks claim that static typing is a crutch for not doing unit testing, but it does provide a mechanism for compile-time location of a whole class of errors. Scala is more concise than Java, but not as much as Clojure. Scala's inter-operation with Java seems to be better than Clojure's, in that most Java operations are easier to do in Scala than in Clojure. For example, I can find no way in Clojure to create a non-static initialization block in a class derived from a Java superclass. For example, I like the Apache commons CLI library for command line argument parsing. In Java and Scala, I can create a new Options object and add Option items to it in an initialization block as follows (Java code): final Options options = new Options() { { addOption(new Option("?", "help", false, "Show this usage information"); // other options } }; I can't figure out how to the same thing in Clojure (except by using (doit...)), although that may reflect my lack of knowledge of the language. Clojure's collections are optimized for immutability. They rarely require copy-on-write semantics. I don't know if Scala's immutable collections are implemented using similar algorithms, but Rich Hickey (Clojure's inventor) goes out of his way to explain how that language's data structures are efficient. Clojure was designed from the beginning for concurrency (as was Scala) and with modern multi-core processors, concurrency takes on more importance, but I occasionally need to write simple non-concurrent utilities, and Scala code probably runs a little faster for these applications since it discourages, but does not prohibit, "simple" mutability. One could argue that one-off utilities do not have to be super-fast, but sometimes they do tasks that take hours or days to complete. I know that there is no right answer to this "question", but I thought I would open it up for discussion. Are there other JVM-based languages that can be used for enterprise level development?

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  • Populating a GridView with ImageViews dynamically/programmatically using a ImageAdapter

    - by Julian Vogels
    Hi folks, this is my first question at stackoverflow, but it's a little tricky already... I try to develop an Android App which allows the user to fetch data from flickr and show it in a gridview (with some nice 3D-Animation). After some adventures i got it almost running, but now I'm stuck. Here's the problem: I got a UI Thread "LoadPhotosTask" which gets the pictures from flickr, just like the open source application photostream. In the method onProgressUpdate(LoadedPhoto... value) of that subclass I call addPhoto(). Until now everythings fine - I got some nice Bitmap and Flickr.photo data with all the information I need. @Override public void onProgressUpdate(LoadedPhoto... value) { addPhoto(value); } On the other hand I have got a GridView. Now I want to fill it with the Photos. It has got an adapter called ImageAdapter (which extends BaseAdapter, see this tutorial). If I use an array inside the ImageAdapter class I can populate the GridView with some sample images. But if I want to populate it at runtime, I don't know what to do. How do I have to set up the getView method in the ImageAdapter? I was trying to fill the array inside the ImageAdapter class with my values in addPhoto, but it doesn't display anything. So first of all I was setting up the array with the amount of Photos i wanted to display in the grid like that (code is inside the ImageAdapter class): // class variable private ImageView[] mThumbIds; [...] public void setupArray(int count) { this.mThumbIds = new ImageView[count]; } Then I call this method with the lenght of my photolist: final Flickr.PhotoList list = params[0]; final int count = list.getCount(); int helper = 0; imagead.setupArray(count); Afterwards I call the getView method manually inside the addPhoto method: private void addPhoto(LoadedPhoto... value) { ImageView image = (ImageView) mInflater.inflate( R.layout.grid_item_photo, null); image.setImageBitmap(value[0].mBitmap); image.setTag(value[0].mPhoto); imagead.setmThumbIds(image, value[0].mPosition); imagead.getView(value[0].mPosition, null, mpicturesGrid); } That is the getView method inside ImageAdapter: public View getView(int position, View convertView, ViewGroup parent) { if (convertView == null) { // if it's not recycled, initialize some // attributes imageView = new ImageView(mContext); imageView.setLayoutParams(new GridView.LayoutParams(EDGE_LENGTH, EDGE_LENGTH)); imageView.setScaleType(ImageView.ScaleType.CENTER_CROP); imageView.setPadding(0, 0, 0, 0); imageView.setVisibility(View.VISIBLE); } else { imageView = (ImageView) convertView; } imageView.setImageDrawable(mThumbIds[position].getDrawable()); imageView.setTag(mThumbIds[position].getTag()); return imageView; } Ok, finally I apologize for my poor english and I hope you can give me some help with the information I provided. Greetings, Julian

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  • Mysql optimization question - How to apply AND logic in search and limit on results in one query?

    - by sandeepan-nath
    This is a little long but I have provided all the database structures and queries so that you can run it immediately and help me. Run the following queries:- CREATE TABLE IF NOT EXISTS `Tutor_Details` ( `id_tutor` int(10) NOT NULL auto_increment, `firstname` varchar(100) NOT NULL default '', `surname` varchar(155) NOT NULL default '', PRIMARY KEY (`id_tutor`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=41 ; INSERT INTO `Tutor_Details` (`id_tutor`,`firstname`, `surname`) VALUES (1, 'Sandeepan', 'Nath'), (2, 'Bob', 'Cratchit'); CREATE TABLE IF NOT EXISTS `Classes` ( `id_class` int(10) unsigned NOT NULL auto_increment, `id_tutor` int(10) unsigned NOT NULL default '0', `class_name` varchar(255) default NULL, PRIMARY KEY (`id_class`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=229 ; INSERT INTO `Classes` (`id_class`,`class_name`, `id_tutor`) VALUES (1, 'My Class', 1), (2, 'Sandeepan Class', 2); CREATE TABLE IF NOT EXISTS `Tags` ( `id_tag` int(10) unsigned NOT NULL auto_increment, `tag` varchar(255) default NULL, PRIMARY KEY (`id_tag`), UNIQUE KEY `tag` (`tag`), KEY `id_tag` (`id_tag`), KEY `tag_2` (`tag`), KEY `tag_3` (`tag`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=18 ; INSERT INTO `Tags` (`id_tag`, `tag`) VALUES (1, 'Bob'), (6, 'Class'), (2, 'Cratchit'), (4, 'Nath'), (3, 'Sandeepan'), (5, 'My'); CREATE TABLE IF NOT EXISTS `Tutors_Tag_Relations` ( `id_tag` int(10) unsigned NOT NULL default '0', `id_tutor` int(10) default NULL, KEY `Tutors_Tag_Relations` (`id_tag`), KEY `id_tutor` (`id_tutor`), KEY `id_tag` (`id_tag`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; INSERT INTO `Tutors_Tag_Relations` (`id_tag`, `id_tutor`) VALUES (3, 1), (4, 1), (1, 2), (2, 2); CREATE TABLE IF NOT EXISTS `Class_Tag_Relations` ( `id_tag` int(10) unsigned NOT NULL default '0', `id_class` int(10) default NULL, `id_tutor` int(10) NOT NULL, KEY `Class_Tag_Relations` (`id_tag`), KEY `id_class` (`id_class`), KEY `id_tag` (`id_tag`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; INSERT INTO `Class_Tag_Relations` (`id_tag`, `id_class`, `id_tutor`) VALUES (5, 1, 1), (6, 1, 1), (3, 2, 2), (6, 2, 2); Following is about the tables:- There are tutors who create classes. Tutor_Details - Stores tutors Classes - Stores classes created by tutors And for searching we are using a tags based approach. All the keywords are stored in tags table (while classes/tutors are created) and tag relations are entered in Tutor_Tag_Relations and Class_Tag_Relations tables (for tutors and classes respectively)like this:- Tags - id_tag tag (this is a a unique field) Tutors_Tag_Relations - Stores tag relations while the tutors are created. Class_Tag_Relations - Stores tag relations while any tutor creates a class In the present data in database, tutor "Sandeepan Nath" has has created class "My Class" and "Bob Cratchit" has created "Sandeepan Class". 3.Requirement The requirement is to return tutor records from Tutor_Details table such that all the search terms (AND logic) are present in the union of these two sets - 1. Tutor_Details table 2. classes created by a tutor in Classes table) Example search and expected results:- Search Term Result "Sandeepan Class" Tutor Sandeepan Nath's record from Tutor Details table "Class" Both the tutors from ... Most importantly, there should be only one mysql query and a LIMIT applicable on the number of results. Following is a working query which I have so far written (It just applies OR logic of search key words instead of the desired AND logic). SELECT td . * FROM Tutor_Details AS td LEFT JOIN Tutors_Tag_Relations AS ttagrels ON td.id_tutor = ttagrels.id_tutor LEFT JOIN Classes AS wc ON td.id_tutor = wc.id_tutor INNER JOIN Class_Tag_Relations AS wtagrels ON td.id_tutor = wtagrels.id_tutor LEFT JOIN Tags AS t ON t.id_tag = ttagrels.id_tag OR t.id_tag = wtagrels.id_tag WHERE t.tag LIKE '%Sandeepan%' OR t.tag LIKE '%Nath%' GROUP BY td.id_tutor LIMIT 20 Please help me with anything you can. Thanks

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  • Apache/PHP serving file multiple times

    - by easement
    I have a system with a download.php page. The page takes and id and loads a file based on from the DB Record and then serves it up. I've noticed a couple instances where files are requested multiple times in short time spans (20ms). Times that are too quick for human input. There are plenty of instances where the downloader functions fine. However, in taking a closer look at the downloader’s usage, I did see some interesting behavior. For instance, the IP address xxx.xxx.xxx.xxx (which is one in a range owned by xxxxxx.de in Germany) came to the site through Google. They browsed around and then came to the page http://site.com/xxxx/press+125.php There they issued a request for /download.php?id=/ZZ/n+aH55Y= (a PDF) at 9:04:23AM. That alone is not a big deal. However, what is interesting is that the server seems to have been quite preoccupied with serving that request. In the logs the request first completes between 9:09:48 and 9:10:00. It looks like the user must have gotten tired of waiting during that time and requested the document two more times. Between 09:14:47 and 09:15:00 the same request appears again, except it is from 9:04:43AM, 20ms later than the first request. Then it pops up a third time, with a request that started at 09:05:06 completing between 09:19:55 and 09:19:58! I’m suspicious of that document. In looking through the logs I see other instances where it takes the server a little while to handle that specific file. Check out this list of requests from zzz.zzz.zzz.zzz[different than above] for the file /download.php?id=/ZZ/n+aH55Y= (the same docuemnt as before): Request time Complete Time 04:32:43 04:33:36 04:32:50 04:33:36 04:32:51 04:33:38 04:33:05 04:33:38 04:33:34 04:33:42 04:33:05 04:33:42 So something is definitely going on. Whether it has to do with this specific document tripping up the server, the download.php page’s code, or if we’re just seeing the evidence of some server level overload as it plays out in real time I’m not yet sure. In fairness, there are other instances of people downloading /download.php?id=/ZZ/n+aH55Y= (the same PDF) without error. However, it is interesting that the multiple processes only seem to happen with this one file, and then only when it is accessed through the page http://site.com/press+125.php . It bears further investigation if there’s something amiss inside the code that causes the system to fire off multiple download requests that occupy the server. I don't know if this press+125.php is a rabbit hole, but there is weird consicence. Any ideas? I'm totally out of ideas. Apache maxed out? Things like that. ///DOWNLOAD.php $file = new files(); $file->comparison_filter("id", "=", $id); //sql to load if ($file->load()) { $file->serve(); } //FILES function serve() { if ($this->is_loaded) { if (file_exists($this->get_value("filename"))) { if ($this->get_value("content_type") != "") { header("Content-Type: " . $this->get_value("content_type")); } header("Content-Length: " . filesize($this->get_value("filename"))); if ($this->get_value("flag_image") == 0 || $this->get_value("flag_image") == false) { header("Cache-Control: private"); header("Content-Disposition: attachment; filename=" . urlencode($this->get_value("original_filename"))); } set_time_limit(0); @readfile($this->get_value("filename")); exit; } } }

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  • log-back and thirdparty writing to stdout. How to stop them getting interleaved.

    - by David Roussel
    First some background. I have a batch-type java process run from a DOS batch script. All the java logging goes to stdout, and the batch script redirects the stdout to a file. (This is good for me because I can ECHO from the script and it gets into the log file, so I can see all the java JVM command line args, which is great for debugging.) I may not I use slf4j API, and for the backend I used to use log4j, but recently switched to logback-classic. Although all my application code uses slf4j, I have a third party library that does it's own logging (not using a standard API) which also gets written to stdout. The problem is that sometimes log lines get mixed up and don't cleanly appear on separate lines. Here is an example of some messed up output: 2010-05-28 18:00:44.783 [thread-1 ] INFO CreditCorrelationElementBuilderImpl - Bump parameters exist for scenario, now attempting bumping. [indexDisplayName=STANDARD_S1_v300] 2010-05-28 18:01:43.517 [thread-1 ] INFO CreditCorrelationElementBuilderImpl - Found adjusted point in data, now applying bump. [point=0.144040000000000] 2010-05-28 18:01:58.642 [thread-1 ] DEBUG com.company.request.Request - Generated request for [dealName=XXX_20050225_01[5],dealType=GENERIC_XXX,correlationType=2,copulaType=1] in 73.8 s, Simon Stopwatch: [sys1.batchpricer.reqgen.gen INHERIT] total 1049 s, counter 24, max 74.1 s, min 212 ms 2010-05-28 18:05/28/10 18:02:20.236 INFO: [ServiceEvent] SubmittedTask:BC-STRESS_04_FZBC-2010-05-21-545024448189310126-23 01:58.658 [req-writer-2b ] INFO .c.g.r.o.OptionalFileDocumentOutput - Writing request XML to \\filserver\dir\file1.xml - write time: 21.4 ms - Simon Stopwatch: [sys1.batchpricer.reqgen.writeinputfile INHERIT] total 905 ms, counter 24, max 109 ms, min 10.8 ms 2010-05-28 18:02:33.626 [ResponseCallbacks-1: DriverJobSpace$TakeJobRunner$1] ERROR c.c.s.s.D.CalculatorCallback - Id:23 no deal found !! 2010-0505/28/10 18:02:50.267 INFO: [ServiceEvent] CompletedTask:BC-STRESS_04_FZBC-2010-05-21-545024448189310126-23:Total:24 Now comparing back to older log files, it seems the problem didn't occur when using log4j as the logging backend. So logback must be doing something different. The problem seems to be that although PrintStream.write(byte buf[], int off, int len) is synchronized, however I can see in ch.qos.logback.core.joran.spi.ConsoleTarget that System.out.write(int b) is the only write method called. So inbetween logback outputting each byte, the thirdparty library is managing to write a whole string to the stdout. (Not only is this cause me a problem, but it must also be a little inefficient?) Is there any other fix to this interleaving problem than patching the code to ConsoleTarget so it implments the other write methods? Any nice work arounds. Or should I just file a bug report? Here is my logback.xml: <configuration> <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender"> <encoder> <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%-16thread] %-5level %-35.35logger{30} - %msg%n</pattern> </encoder> </appender> <root level="DEBUG"> <appender-ref ref="STDOUT" /> </root> </configuration> I'm using logback 0.9.20 with java 1.6.0_07.

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  • Form loop db insertion + javascript altering

    - by MrStatic
    I basically need to check if there is an easier way to do this before I rewrite all the code. I have a fairly large form that I have each input named with []'s on the end so I can loop through via php for easy insertion. <input type="hidden" name="currentdate[]" value="<?php echo date('mdY'); ?>"> <td><input style="width: 50px" type="text" name="jackname[]" /></td> <td><input style="width: 20px" type="text" name="jackkey[]" /></td> <td><input style="width: 50px" type="text" name="jackbeg[]" /></td> <td><input style="width: 50px" type="text" name="jackend[]" /></td> <td><input style="width: 50px" type="text" name="jackbegveh" /></td> <td><input style="width: 50px" type="text" name="jackbegmon[]" /></td> <td><input style="width: 50px" type="text" name="jackendveh" /></td> <td><input style="width: 50px" type="text" name="jackendmon[]" /></td> <td><input style="width: 50px" type="text" name="jacktx" disabled /></td> There are quite a few more fields but you get the idea. I then use foreach ($_POST['jackname'] as $row=>$name) { $jackname = $name; $date = $_POST['currentdate'][$row]; $jackkey = $_POST['jackkey'][$row]; $jackbeg = $_POST['jackbeg'][$row]; $jackend = $_POST['jackend'][$row]; $jackbegveh = $_POST['jackbegveh'][$row]; $jackbegmon = $_POST['jackbegmon'][$row]; $jackendveh = $_POST['jackendveh'][$row]; $jackendmon = $_POST['jackendmon'][$row]; $jacktx = $_POST['jacktx'][$row]; if ($jacktx == '') { $jacktx = '0'; } if (empty($jackkey)) { echo 'Skipped empty! <br />'; } else { mysql_query("INSERT INTO `ticket_counts_jackson` VALUES('', '" . $date . "', '" . $jackname . "', '" . $jackkey . "', '" . $jackbeg . "', '" . $jackend . "', '" . $jackbegveh . "', '" . $jackbegmon . "', '" . $jackendveh . "', '" . $jackendmon . "', '" . $jacktx . "')", $mysql_link) or die(mysql_error()); echo 'Added the info the db! <br />'; } } I use the above to loop through the form and add it to the database. Now for my main question. I also want to add in some javascript to do a little math. Basically ($jackendveh - $jackbegveh) - ($jackendmon - $jackbegmon) and have that displayed in jacktx. Currently the only way I know of adding in the math calculations is to rename each input to a unique name and then rewrite my insert from 1 insert to 8 inserts.

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  • Matrix Multiplication with Threads: Why is it not faster?

    - by prelic
    Hey all, So I've been playing around with pthreads, specifically trying to calculate the product of two matrices. My code is extremely messy because it was just supposed to be a quick little fun project for myself, but the thread theory I used was very similar to: #include <pthread.h> #include <stdio.h> #include <stdlib.h> #define M 3 #define K 2 #define N 3 #define NUM_THREADS 10 int A [M][K] = { {1,4}, {2,5}, {3,6} }; int B [K][N] = { {8,7,6}, {5,4,3} }; int C [M][N]; struct v { int i; /* row */ int j; /* column */ }; void *runner(void *param); /* the thread */ int main(int argc, char *argv[]) { int i,j, count = 0; for(i = 0; i < M; i++) { for(j = 0; j < N; j++) { //Assign a row and column for each thread struct v *data = (struct v *) malloc(sizeof(struct v)); data->i = i; data->j = j; /* Now create the thread passing it data as a parameter */ pthread_t tid; //Thread ID pthread_attr_t attr; //Set of thread attributes //Get the default attributes pthread_attr_init(&attr); //Create the thread pthread_create(&tid,&attr,runner,data); //Make sure the parent waits for all thread to complete pthread_join(tid, NULL); count++; } } //Print out the resulting matrix for(i = 0; i < M; i++) { for(j = 0; j < N; j++) { printf("%d ", C[i][j]); } printf("\n"); } } //The thread will begin control in this function void *runner(void *param) { struct v *data = param; // the structure that holds our data int n, sum = 0; //the counter and sum //Row multiplied by column for(n = 0; n< K; n++){ sum += A[data->i][n] * B[n][data->j]; } //assign the sum to its coordinate C[data->i][data->j] = sum; //Exit the thread pthread_exit(0); } source: http://macboypro.com/blog/2009/06/29/matrix-multiplication-in-c-using-pthreads-on-linux/ For the non-threaded version, I used the same setup (3 2-d matrices, dynamically allocated structs to hold r/c), and added a timer. First trials indicated that the non-threaded version was faster. My first thought was that the dimensions were too small to notice a difference, and it was taking longer to create the threads. So I upped the dimensions to about 50x50, randomly filled, and ran it, and I'm still not seeing any performance upgrade with the threaded version. What am I missing here?

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  • reloading page while an ajax request in progress gives empty response and status as zero

    - by Jayapal Chandran
    Hi, Browser is firefox 3.0.10 I am requesting a page using ajax. The response is in progress may be in readyState less than 4. In this mean time i am trying to reload the page. What happens is the request ends giving an empty response. I used alert to find what string has been given as response text. I assume that by this time the ready state 4 is reached. why it is empty string. when i alert the xmlhttpobject.status it displayed 0. when i alert the xmlhttpobject.statusText an exception occurs stating that NOT AVAILABLE. when i read in the document http://www.devx.com/webdev/Article/33024/0/page/2 it said for 3 and 4 status and statusText are available but when i tested only status is available but not satausText Here is a sample code. consider that i have requested a page and my callback function is as follows function cb(rt) { if(rt.readyState==4) { alert(rt.status); alert(rt.statusText); // which throws an exception } } and my server side script is as follows sleep(30); //flushing little drop down code besides these i noticed the following... assume again i am requesting the above script using ajax. now there will be an idle time till 30 seconds is over before that 30 seconds i press refresh. i got xmlhttpobject.status as 0 but still the browser did not reload the page untill that 30 seconds. WHY? so what is happening when i refresh a page before an ajax request is complete is the status value is set to zero and the ready state is set to 4 but the page still waits for the response from the server to end... what is happening... THE REASON FOR ME TO FACE SOME THING LIKE THIS IS AS FOLLOWS. when ever i do an ajax request ... if the process succeeded like inserting some thing or deleting something i popup a div stating that updated successfully and i will reload the page. but if there is any error then i do not reload the page instead i just alert that unable to process this request. what happens if the user reloads the page before any of this request is complete is i get an empty response which in my calculation is there is a server error. so i was debugging the ajax response to filter out that the connection has been interrupted because the user had pressed reload. so in this time i don't want to display unable to process this request when the user reloads the page before the request has been complete. oh... a long story. IT IS A LONG DESCRIPTION SO THAT I CAN MAKE EXPERTS UNDERSTAND MY DOUBT. so what i want form the above. any type of answer would clear my mind. or i would like to say all type of answers. EDIT: 19 dec. If i did not get any correct answer then i would delete this question and will rewrite with examples. else i will accept after experimenting.

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  • Test whether pixel is inside the blobs for ofxOpenCV

    - by mia
    I am doing an application of the concept of the dodgeball and need to test of the pixel of the ball is in the blobs capture(which is the image of the player) I am stucked and ran out of idea of how to implement it. I manage to do a little progress which have the blobs but I not sure how to test it. Please help. I am a newbie who in a desperate condition. Thank you. This is some of my code. void testApp::setup(){ #ifdef _USE_LIVE_VIDEO vidGrabber.setVerbose(true); vidGrabber.initGrabber(widthS,heightS); #else vidPlayer.loadMovie("fingers.mov"); vidPlayer.play(); #endif widthS = 320; heightS = 240; colorImg.allocate(widthS,heightS); grayImage.allocate(widthS,heightS); grayBg.allocate(widthS,heightS); grayDiff.allocate(widthS,heightS); ////<---what I want bLearnBakground = true; threshold = 80; //////////circle////////////// counter = 0; radius = 0; circlePosX = 100; circlePosY=200; } void testApp::update(){ ofBackground(100,100,100); bool bNewFrame = false; #ifdef _USE_LIVE_VIDEO vidGrabber.grabFrame(); bNewFrame = vidGrabber.isFrameNew(); #else vidPlayer.idleMovie(); bNewFrame = vidPlayer.isFrameNew(); #endif if (bNewFrame){ if (bLearnBakground == true){ grayBg = grayImage; // the = sign copys the pixels from grayImage into grayBg (operator overloading) bLearnBakground = false; } #ifdef _USE_LIVE_VIDEO colorImg.setFromPixels(vidGrabber.getPixels(),widthS,heightS); #else colorImg.setFromPixels(vidPlayer.getPixels(),widthS,heightS); #endif grayImage = colorImg; grayDiff.absDiff(grayBg, grayImage); grayDiff.threshold(threshold); contourFinder.findContours(grayDiff, 20, (340*240)/3, 10, true); // find holes } ////////////circle//////////////////// counter = counter + 0.05f; if(radius>=50){ circlePosX = ofRandom(10,300); circlePosY = ofRandom(10,230); } radius = 5 + 3*(counter); } void testApp::draw(){ // draw the incoming, the grayscale, the bg and the thresholded difference ofSetColor(0xffffff); //white colour grayDiff.draw(10,10);// draw start from point (0,0); // we could draw the whole contour finder // or, instead we can draw each blob individually, // this is how to get access to them: for (int i = 0; i < contourFinder.nBlobs; i++){ contourFinder.blobs[i].draw(10,10); } ///////////////circle////////////////////////// //let's draw a circle: ofSetColor(0,0,255); char buffer[255]; float a = radius; sprintf(buffer,"radius = %i",a); ofDrawBitmapString(buffer, 120, 300); if(radius>=50) { ofSetColor(255,255,255); counter = 0; } else{ ofSetColor(255,0,0); } ofFill(); ofCircle(circlePosX,circlePosY,radius); }

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  • Array not showing in Jlist but filled in console

    - by OVERTONE
    Hey there. been a busy debugger today. ill give ths short version. ive made an array list that takes names from a database. then i put the contents of the arraylist into an array of strings. now i want too display the arrays contents in a JList. the weird thing is it was working earlier. and ive two methods. ones just a little practice too make sure i was adding to the Jlist correctly. so heres the key codes. this is the layout of my code. variables constructor methods in my variables i have these 3 defined String[] contactListNames = new String[5]; ArrayList<String> rowNames = new ArrayList<String>(); JList contactList = new JList(contactListNames); simple enough. in my constructor i have them again. contactListNames = new String[5]; contactList = new JList(contactListNames); //i dont have the array list defined though. printSqlDetails(); // the prinSqldetails was too make sure that the connectionw as alright. and its working fine. fillContactList(); // this is the one thats causing me grief. its where all the work happens. // fillContactListTest(); // this was the tester that makes sure its adding to the list alright. heres the code for fillContactListTest() public void fillContactListTest() { for(int i = 0;i<3;i++) { try { String contact; System.out.println(" please fill the list at index "+ i); Scanner in = new Scanner(System.in); contact = in.next(); contactListNames[i] = contact; in.nextLine(); } catch(Exception e) { e.printStackTrace(); } } } heres the main one thats supposed too work. public void fillContactList() { int i =0; createConnection(); ArrayList<String> rowNames = new ArrayList<String>(); try { Statement stmt = conn.createStatement(); ResultSet namesList = stmt.executeQuery("SELECT name FROM Users"); try { while (namesList.next()) { rowNames.add(namesList.getString(1)); contactListNames =(String[])rowNames.toArray(new String[rowNames.size()]); // this used to print out contents of array list // System.out.println("" + rowNames); while(i<contactListNames.length) { System.out.println(" " + contactListNames[i]); i++; } } } catch(SQLException q) { q.printStackTrace(); } conn.commit(); stmt.close(); conn.close(); } catch(SQLException e) { e.printStackTrace(); } } i really need help here. im at my wits end. i just cant see why the first method would add to the JList no problem. but the second one wont. both the contactListNames array and array list can print fine and have the names in them. but i must be transfering them too the jlist wrong. please help p.s im aware this is long. but trust me its the short version.

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  • XDocument + IEnumerable is causing out of memory exception in System.Xml.Linq.dll

    - by Manatherin
    Basically I have a program which, when it starts loads a list of files (as FileInfo) and for each file in the list it loads a XML document (as XDocument). The program then reads data out of it into a container class (storing as IEnumerables), at which point the XDocument goes out of scope. The program then exports the data from the container class to a database. After the export the container class goes out of scope, however, the garbage collector isn't clearing up the container class which, because its storing as IEnumerable, seems to lead to the XDocument staying in memory (Not sure if this is the reason but the task manager is showing the memory from the XDocument isn't being freed). As the program is looping through multiple files eventually the program is throwing a out of memory exception. To mitigate this ive ended up using System.GC.Collect(); to force the garbage collector to run after the container goes out of scope. this is working but my questions are: Is this the right thing to do? (Forcing the garbage collector to run seems a bit odd) Is there a better way to make sure the XDocument memory is being disposed? Could there be a different reason, other than the IEnumerable, that the document memory isnt being freed? Thanks. Edit: Code Samples: Container Class: public IEnumerable<CustomClassOne> CustomClassOne { get; set; } public IEnumerable<CustomClassTwo> CustomClassTwo { get; set; } public IEnumerable<CustomClassThree> CustomClassThree { get; set; } ... public IEnumerable<CustomClassNine> CustomClassNine { get; set; }</code></pre> Custom Class: public long VariableOne { get; set; } public int VariableTwo { get; set; } public DateTime VariableThree { get; set; } ... Anyway that's the basic structures really. The Custom Classes are populated through the container class from the XML document. The filled structures themselves use very little memory. A container class is filled from one XML document, goes out of scope, the next document is then loaded e.g. public static void ExportAll(IEnumerable<FileInfo> files) { foreach (FileInfo file in files) { ExportFile(file); //Temporary to clear memory System.GC.Collect(); } } private static void ExportFile(FileInfo file) { ContainerClass containerClass = Reader.ReadXMLDocument(file); ExportContainerClass(containerClass); //Export simply dumps the data from the container class into a database //Container Class (and any passed container classes) goes out of scope at end of export } public static ContainerClass ReadXMLDocument(FileInfo fileToRead) { XDocument document = GetXDocument(fileToRead); var containerClass = new ContainerClass(); //ForEach customClass in containerClass //Read all data for customClass from XDocument return containerClass; } Forgot to mention this bit (not sure if its relevent), the files can be compressed as .gz so I have the GetXDocument() method to load it private static XDocument GetXDocument(FileInfo fileToRead) { XDocument document; using (FileStream fileStream = new FileStream(fileToRead.FullName, FileMode.Open, FileAccess.Read, FileShare.Read)) { if (String.Compare(fileToRead.Extension, ".gz", true) == 0) { using (GZipStream zipStream = new GZipStream(fileStream, CompressionMode.Decompress)) { document = XDocument.Load(zipStream); } } else { document = XDocument.Load(fileStream); } return document; } } Hope this is enough information. Thanks Edit: The System.GC.Collect() is not working 100% of the time, sometimes the program seems to retain the XDocument, anyone have any idea why this might be?

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  • Data munging and data import scripting

    - by morpheous
    I need to write some scripts to carry out some tasks on my server (running Ubuntu server 8.04 TLS). The tasks are to be run periodically, so I will be running the scripts as cron jobs. I have divided the tasks into "group A" and "group B" - because (in my mind at least), they are a bit different. Task Group A import data from a file and possibly reformat it - by reformatting, I mean doing things like santizing the data, possibly normalizing it and or running calculations on 'columns' of the data Import the munged data into a database. For now, I am mostly using mySQL for the vast majority of imports - although some files will be imported into a sqlLite database. Note: The files will be mostly text files, although some of the files are in a binary format (my own proprietary format, written by a C++ application I developed). Task Group B Extract data from the database Perform calculations on the data and either insert or update tables in the database. My coding experience is is primarily as a C/C++ developer, although I have been using PHP as well for the last 2 years or so. I am from a windows background so I am still finding my feet in the linux environment. My question is this - I need to write scripts to perform the tasks I described above. Although I suppose I could write a few C++ applications to be used in the shell scripts, I think it may be better to write them in a scripting language (maybe this is a flawed assumption?). My thinking is that it would be easier to modify thins in a script - no need to rebuild etc for changes to functionality. Additionally, C++ data munging in C++ tends to involve more lines of code than "natural" scripting languages such as Perl, Python etc. Assuming that the majority of people on here agree that scripting is the way to go, herein lies my dilema. Which scripting language to use to perform the tasks above (giving my background). My gut instinct tells me that Perl (shudder) would be the most obvious choice for performing all of the above tasks. BUT (and that is a big BUT). The mere mention of Perl makes my toes curl, as I had a very, very bag experience with it a while back. The syntax seems quite unnatural to me - despite how many times I have tried to learn it - so if possible, I would really like to give it a miss. PHP (which I already know), also am not sure is a good candidate for scripting on the CLI (I have not seen many examples on how to do this etc - so I may be wrong). The last thing I must mention is that IF I have to learn a new language in order to do this, I cannot afford (time constraint) to spend more than a day, in learning the key commands/features required in order to do this (I can always learn the details of the language later, once I have actually deployed the scripts). So, which scripting language would you recommend (PHP, Python, Perl, [insert your favorite here]) - and most importantly WHY?. Or, should I just stick to writing little C++ applications that I call in a shell script?. Lastly, if you have suggested a scripting language, can you please show with a FEW lines (Perl mongers - I'm looking in your direction [nothing to cryptic!] ;) ) how I can use the language you suggested to do what I want to do. Hopefully, the lines you present will convince me that it can be done easily and elegantly in the language you suggested.

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  • How to make a jQuery plugin (the right way)?

    - by macek
    I know there are jQuery cookie plugins out there, but I wanted to write one for the sake of better learning the jQuery plugin pattern. I like the separation of "work" in small, manageable functions, but I feel like I'm passing name, value, and options arguments around too much. Is there a way this can be refactored? I'm looking for snippets of code to help illustrate examples provided with in answers. Any help is appreciated. Thanks :) example usage $.cookie('foo', 'bar', {expires:7}); $.cookie('foo'); //=> bar $.cookie('foo', null); $.cookie('foo'); //=> undefined Edit: I did a little bit of work on this. You can view the revision history to see where this has come from. It still feels like more refactoring can be done to optimize the flow a bit. Any ideas? the plugin (function($){ $.cookie = function(name, value, options) { if (typeof value == 'undefined') { return get(name); } else { options = $.extend({}, $.cookie.defaults, options || {}); return (value != null) ? set(name, value, options) : unset(name, options); } }; $.cookie.defaults = { expires: null, path: '/', domain: null, secure: false }; var set = function(name, value, options){ console.log(options); return document.cookie = options_string(name, value, options); }; var get = function(name){ var cookies = {}; $.map(document.cookie.split(';'), function(pair){ var c = $.trim(pair).split('='); cookies[c[0]] = c[1]; }); return decodeURIComponent(cookies[name]); }; var unset = function(name, options){ value = ''; options.expires = -1; set(name, value, options); }; var options_string = function(name, value, options){ var pairs = [param.name(name, value)]; $.each(options, function(k,v){ pairs.push(param[k](v)); }); return $.map(pairs, function(p){ return p === null ? null : p; }).join(';'); }; var param = { name: function(name, value){ return name + "=" + encodeURIComponent(value); }, expires: function(value){ // no expiry if(value === null){ return null; } // number of days else if(typeof value == "number"){ d = new Date(); d.setTime(d.getTime() + (value * 24 * 60 * 60 * 1000)); } // date object else if(typeof value == "object" && value instanceof "Date") { d = value; } return "expires=" + d.toUTCString(); }, path: function(value){ return "path="+value; }, domain: function(value){ return value === null ? null : "domain=" + value; }, secure: function(bool){ return bool ? "secure" : null; } }; })(jQuery);

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  • Geolocation through Android's GPS Provider on a website?

    - by Corey Ogburn
    I'm trying to get the geolocation of the mobile device in a regular website, not a webview of an application or anything native like that. I'm getting a location, but it's highly inaccurate, the accuracy comes back as 3230 or some other outrageous number. I'm assuming that's in meters, either way it's not nearly accurate enough. By comparison, the same webpage on a laptop gets an accuracy of 30-40. My first thought was that it was using the Network Provider instead of the GPS Provider, telling me where I am based on tower location and reach. A little research later I found enableHighAccuracy and set it true in the options that I pass. After including that, I still notice no difference. Here's the test page's HTML/javascript: <html> <head> <script type="text/javascript" src="http://ecn.dev.virtualearth.net/mapcontrol/mapcontrol.ashx?v=7.0"></script> <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.3/jquery.min.js"></script> <script type="text/javascript"> function OnLoad() { $("#Status").text("Init"); if (navigator.geolocation) { $("#Status").text("Supports Geolocation"); navigator.geolocation.getCurrentPosition(HandleLocation, LocationError, { enableHighAccuracy: true }); $("#Status").text("Sent position request..."); } else { $("#Status").text("Doesn't support geolocation"); } } function HandleLocation(position) { $("#Status").text("Received response:"); $("#Position").text("(" + position.coords.latitude + ", " + position.coords.longitude + ") accuracy: " + position.coords.accuracy); var loc = new Microsoft.Maps.Location(position.coords.latitude, position.coords.longitude); GetMap(loc); } function LocationError(error) { switch(error.code) { case error.PERMISSION_DENIED: alert("Location not provided"); break; case error.POSITION_UNAVAILABLE: alert("Current location not available"); break; case error.TIMEOUT: alert("Timeout"); break; default: alert("unknown error"); break; } } function GetMap(loc) { var map = new Microsoft.Maps.Map(document.getElementById("mapDiv"), {credentials: "Aj59meaCR1e7rNgkfQy7j08Pd3mzfP1r04hGesGmLe2a3ZwZ3iGecwPX2SNPWq5a", center: loc, mapTypeId: Microsoft.Maps.MapTypeId.road, zoom: 15}); } </script> </head> <body onload="javascript:OnLoad()"> <div id="Status"></div> <div id="Position"></div><br/> <div id='mapDiv' style="position:relative; width:600px; height:400px;"></div> </body> </html> I'm testing this on a rooted MyTouch 3G running Cyanogen 6.1 stable, Android 2.2 and GPS is enabled. In case rooting was a problem, I have also had various friends and coworkers try the webpage on their non-rooted 2.0+ Android devices. Each phone had various effects on the accuracy, but none were better than 1000, I attribute this to the different carriers. I have not (but eventually will) tested with iPhone or other location-aware cell phones.

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  • Dynamically loading modules in Python (+ multi processing question)

    - by morpheous
    I am writing a Python package which reads the list of modules (along with ancillary data) from a configuration file. I then want to iterate through each of the dynamically loaded modules and invoke a do_work() function in it which will spawn a new process, so that the code runs ASYNCHRONOUSLY in a separate process. At the moment, I am importing the list of all known modules at the beginning of my main script - this is a nasty hack I feel, and is not very flexible, as well as being a maintenance pain. This is the function that spawns the processes. I will like to modify it to dynamically load the module when it is encountered. The key in the dictionary is the name of the module containing the code: def do_work(work_info): for (worker, dataset) in work_info.items(): #import the module defined by variable worker here... # [Edit] NOT using threads anymore, want to spawn processes asynchronously here... #t = threading.Thread(target=worker.do_work, args=[dataset]) # I'll NOT dameonize since spawned children need to clean up on shutdown # Since the threads will be holding resources #t.daemon = True #t.start() Question 1 When I call the function in my script (as written above), I get the following error: AttributeError: 'str' object has no attribute 'do_work' Which makes sense, since the dictionary key is a string (name of the module to be imported). When I add the statement: import worker before spawning the thread, I get the error: ImportError: No module named worker This is strange, since the variable name rather than the value it holds are being used - when I print the variable, I get the value (as I expect) whats going on? Question 2 As I mentioned in the comments section, I realize that the do_work() function written in the spawned children needs to cleanup after itself. My understanding is to write a clean_up function that is called when do_work() has completed successfully, or an unhandled exception is caught - is there anything more I need to do to ensure resources don't leak or leave the OS in an unstable state? Question 3 If I comment out the t.daemon flag statement, will the code stil run ASYNCHRONOUSLY?. The work carried out by the spawned children are pretty intensive, and I don't want to have to be waiting for one child to finish before spawning another child. BTW, I am aware that threading in Python is in reality, a kind of time sharing/slicing - thats ok Lastly is there a better (more Pythonic) way of doing what I'm trying to do? [Edit] After reading a little more about Pythons GIL and the threading (ahem - hack) in Python, I think its best to use separate processes instead (at least IIUC, the script can take advantage of multiple processes if they are available), so I will be spawning new processes instead of threads. I have some sample code for spawning processes, but it is a bit trivial (using lambad functions). I would like to know how to expand it, so that it can deal with running functions in a loaded module (like I am doing above). This is a snippet of what I have: def do_mp_bench(): q = mp.Queue() # Not only thread safe, but "process safe" p1 = mp.Process(target=lambda: q.put(sum(range(10000000)))) p2 = mp.Process(target=lambda: q.put(sum(range(10000000)))) p1.start() p2.start() r1 = q.get() r2 = q.get() return r1 + r2 How may I modify this to process a dictionary of modules and run a do_work() function in each loaded module in a new process?

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  • Why don't I just build the whole web app in Javascript and Javascript HTML Templates?

    - by viatropos
    I'm getting to the point on an app where I need to start caching things, and it got me thinking... In some parts of the app, I render table rows (jqGrid, slickgrid, etc.) or fancy div rows (like in the New Twitter) by grabbing pure JSON and running it through something like Mustache, jquery.tmpl, etc. In other parts of the app, I just render the info in pure HTML (server-side HAML templates), and if there's searching/paginating, I just go to a new URL and load a new HTML page. Now the problem is in caching and maintainability. On one hand I'm thinking, if everything was built using Javascript HTML Templates, then my app would serve just an HTML layout/shell, and a bunch of JSON. If you look at the Facebook and Twitter HTML source, that's basically what they're doing (95% json/javascript, 5% html). This would make it so my app only needed to cache JSON (pages, actions, and/or records). Which means you'd hit the cache no matter if you were some remote api developer accessing a JSON api, or the strait web app. That is, I don't need 2 caches, one for the JSON, one for the HTML. That seems like it'd cut my cache store down in half, and streamline things a little bit. On the other hand, I'm thinking, from what I've seen/experienced, generating static HTML server-side, and caching that, seems to be much better performance wise cross-browser; you get the graphics instantly and don't have to wait that split-second for javascript to render it. StackOverflow seems to do everything in plain HTML, and you can tell... everything appears at once. Notice how though on twitter.com, the page is blank for .5-1 seconds, and the page chunks in: the javascript has to render the json. The downside with this is that, for anything dynamic (like endless scrolling, or grids), I'd have to create javascript templates anyway... so now I have server-side HAML templates, client-side javascript templates, and a lot more to cache. My question is, is there any consensus on how to approach this? What are the benefits and drawbacks from your experience of mixing the two versus going 100% with one over the other? Update: Some reasons that factor into why I haven't yet made the decision to go with 100% javascript templating are: Performance. Haven't formally tested, but from what I've seen, raw html renders faster and more fluidly than javascript-generated html cross-browser. Plus, I'm not sure how mobile devices handle dynamic html performance-wise. Testing. I have a lot of integration tests that work well with static HTML, so switching to javascript-only would require 1) more focused pure-javascript testing (jasmine), and 2) integrating javascript into capybara integration tests. This is just a matter of time and work, but it's probably significant. Maintenance. Getting rid of HAML. I love HAML, it's so easy to write, it prints pretty HTML... It makes code clean, it makes maintenance easy. Going with javascript, there's nothing as concise. SEO. I know google handles the ajax /#!/path, but haven't grasped how this will affect other search engines and how older browsers handle it. Seems like it'd require a significant setup.

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  • Custom Online Backup Solution Advice

    - by Martín Marconcini
    I have to implement a way so our customers can backup their SQL 2000/5/8 databasase online. The application they use is a C#/.NET35 Winforms application that connects to a SQL Server (can be 2000/2005/2008, sometimes express editions). The SQL Server is on the same LAN. Our application has a very specific UI and we must code each form following those guidelines. There’s lots of GDI+ to give it the look and feel we want. For that reason, using a 3rd party application is not a very good idea. We need to charge the customer on a monthly/annual basis for the service. Preferably, the customer doesn’t need to care about bandwidth and storage space. It must be transparent. Given the above reqs., my first thoughts are: Solution 1: Code some sort of FTP basic functionality with behind the scenes SQL Backup mechanism, then hire a Hosting service and compress-transfer the .BAK to the Hosting. Maintain a series of Folders (for each customer). They won’t see what’s happening. They will just see a list of their files and a big “Backup now” button that will perform the SQL backup, compress it and upload it (and update the file list) ;) Pros: Not very complicated to implement, simple to use, fairly simple to configure (could have a dedicated ftp user/pass) Cons: Finding a “ftp” only hosting plan is not probably going to be easy, they usually come with a bunch of stuff. FTP is not always the best protocol. more? Solution 2: Similar to 1, but instead of FTP, find a cloud computing service like Amazon S3, Mosso or similar. Pros: Cloud Storage is fast, reliable, etc. It’s kind of easy to implement (specially if there are APIs like AWS or Mosso). Cons: I have been unable to come up with a service optimized for resellers where I can give multiple sub-accounts (one for each customer). Billing is going to be a nightmare cuz these services bill per/GB and with One account it’s impossible to differentiate each customer. Solution 3: Similar to 2, but letting the user create their own account on Amazon S3 (for example). Pros: You forget about billing and such. Cons: A mess for the customer who has to open the Amazon (or whatever) account, will be charged for that and not from you. You can’t really charge the customer (since you’re just not doing anything). Solution 4: Use one of the many backup online solutions that use the tech in cloud storage. Pros: many of these include SQL Server backup, and a lot of features that we’d have to implement. Plus web access and stuff like that will come included. Cons: Still have the billing problem described in number 2. Little of these companies (if any) offers “reseller” accounts. You have to eventually use their software (some offer certain branding). Any better approach? Summary: You have a software (.NET Winapp). You want your users to be able to backup their SQL Server databases online (and be able to retrieve the backups if needed). You ideally would like to charge the customer for this service (i.e. XX € a year).

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  • QuickBox2D poly behaviour vs box or circle

    - by Ben Kanizay
    Hi I've played a little with Box2D before and have just started using QuickBox2D which makes things heaps easier. I am however getting different behaviour with a specific poly shape than I am with a box. All other properties are the same. I've included 3 simple examples and their source below. What I really want to work is Example 1 with both objects as poly. As you can see, it seems like the 'paddle' poly is the one that's failing - the 'ball' (whether it's a poly or circle) just falls straight through it instead of bouncing off as it does with a box 'paddle' object. Would appreciate some help or insight. As I can only post one line at this stage, the swf previews of the 3 examples can be seen here Example 1 source: package { import com.actionsnippet.qbox.QuickBox2D; import com.actionsnippet.qbox.QuickObject; import flash.display.MovieClip; public class Eg1 extends MovieClip { private var sim:QuickBox2D; private var paddle:QuickObject; private var ball:QuickObject; public function Eg1() { this.sim = new QuickBox2D(this); this.paddle = this.sim.addPoly({ x:13, y:19, angle:0, density:0, draggable:false, isBullet:true, verts:[[-3.84,-0.67,-2.84,-1,-2.17,-0.33,2.17,-0.33,2.84,-1,3.84,-0.67,2.84,1,-2.51,1]] }); this.ball = this.sim.addPoly({ x:13, y:1, restitution:1, friction:1, draggable:false, isBullet:true, verts:[[-0.34,-1,0.34,-1,0.67,-0.33,0.67,0.33,0.34,1,-0.34,1,-0.67,0.33,-0.67,-0.33]] }); this.sim.start(); } }} Example 2 source: package { import com.actionsnippet.qbox.QuickBox2D; import com.actionsnippet.qbox.QuickObject; import flash.display.MovieClip; public class Eg2 extends MovieClip { private var sim:QuickBox2D; private var paddle:QuickObject; private var ball:QuickObject; public function Eg2() { this.sim = new QuickBox2D(this); this.paddle = this.sim.addBox({ x:13, y:19, angle:0, density:0, draggable:false, isBullet:true, width:8 }); this.ball = this.sim.addPoly({ x:13, y:1, restitution:1, friction:1, draggable:false, isBullet:true, verts:[[-0.34,-1,0.34,-1,0.67,-0.33,0.67,0.33,0.34,1,-0.34,1,-0.67,0.33,-0.67,-0.33]] }); this.sim.start(); } }} Example 3 source: package { import com.actionsnippet.qbox.QuickBox2D; import com.actionsnippet.qbox.QuickObject; import flash.display.MovieClip; public class Eg3 extends MovieClip { private var sim:QuickBox2D; private var paddle:QuickObject; private var ball:QuickObject; public function Eg3() { this.sim = new QuickBox2D(this); this.paddle = this.sim.addPoly({ x:13, y:19, angle:0, density:0, draggable:false, isBullet:true, verts:[[-3.84,-0.67,-2.84,-1,-2.17,-0.33,2.17,-0.33,2.84,-1,3.84,-0.67,2.84,1,-2.51,1]] }); this.ball = this.sim.addCircle({ x:13, y:1, restitution:1, friction:1, draggable:false, isBullet:true, radius:1 }); this.sim.start(); } }}

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