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• Why is it still so hard to write software?

  - by nornagon

  Writing software, I find, is composed of two parts: the Idea, and the Implementation. The Idea is about thinking: "I have this problem; how do I solve it?" and further, "how do I solve it elegantly?" The answers to these questions are obtainable by thinking about algorithms and architecture. The ideas come partially through analysis and partially through insight and intuition. The Idea is usually the easy part. You talk to your friends and co-workers and you nut it out in a meeting or over coffee. It takes an hour or two, plus revisions as you implement and find new problems. The Implementation phase of software development is so difficult that we joke about it. "Oh," we say, "the rest is a Simple Matter of Code." Because it should be simple, but it never is. We used to write our code on punch cards, and that was hard: mistakes were very difficult to spot, so we had to spend extra effort making sure every line was perfect. Then we had serial terminals: we could see all our code at once, search through it, organise it hierarchically and create things abstracted from raw machine code. First we had assemblers, one level up from machine code. Mnemonics freed us from remembering the machine code. Then we had compilers, which freed us from remembering the instructions. We had virtual machines, which let us step away from machine-specific details. And now we have advanced tools like Eclipse and Xcode that perform analysis on our code to help us write code faster and avoid common pitfalls. But writing code is still hard. Writing code is about understanding large, complex systems, and tools we have today simply don't go very far to help us with that. When I click "find all references" in Eclipse, I get a list of them at the bottom of the window. I click on one, and I'm torn away from what I was looking at, forced to context switch. Java architecture is usually several levels deep, so I have to switch and switch and switch until I find what I'm really looking for -- by which time I've forgotten where I came from. And I do that all day until I've understood a system. It's taxing mentally, and Eclipse doesn't do much that couldn't be done in 1985 with grep, except eat hundreds of megs of RAM. Writing code has barely changed since we were staring at amber on black. We have the theoretical groundwork for much more advanced tools, tools that actually work to help us comprehend and extend the complex systems we work with every day. So why is writing code still so hard?

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• Why does Python's math.factorial not play nice with threads?

  - by W1N9Zr0

  Why does math.factorial act so weird in a thread? Here is an example, it creates three threads: thread that just sleeps for a while thread that increments an int for a while thread that does math.factorial on a large number. It calls start on the threads, then join with a timeout The sleep and spin threads work as expected and return from start right away, and then sit in the join for the timeout. The factorial thread on the other hand does not return from start until it runs to the end! import sys from threading import Thread from time import sleep, time from math import factorial # Helper class that stores a start time to compare to class timed_thread(Thread): def __init__(self, time_start): Thread.__init__(self) self.time_start = time_start # Thread that just executes sleep() class sleep_thread(timed_thread): def run(self): sleep(15) print "st DONE:\t%f" % (time() - time_start) # Thread that increments a number for a while class spin_thread(timed_thread): def run(self): x = 1 while x < 120000000: x += 1 print "sp DONE:\t%f" % (time() - time_start) # Thread that calls math.factorial with a large number class factorial_thread(timed_thread): def run(self): factorial(50000) print "ft DONE:\t%f" % (time() - time_start) # the tests print print "sleep_thread test" time_start = time() st = sleep_thread(time_start) st.start() print "st.start:\t%f" % (time() - time_start) st.join(2) print "st.join:\t%f" % (time() - time_start) print "sleep alive:\t%r" % st.isAlive() print print "spin_thread test" time_start = time() sp = spin_thread(time_start) sp.start() print "sp.start:\t%f" % (time() - time_start) sp.join(2) print "sp.join:\t%f" % (time() - time_start) print "sp alive:\t%r" % sp.isAlive() print print "factorial_thread test" time_start = time() ft = factorial_thread(time_start) ft.start() print "ft.start:\t%f" % (time() - time_start) ft.join(2) print "ft.join:\t%f" % (time() - time_start) print "ft alive:\t%r" % ft.isAlive() And here is the output on Python 2.6.5 on CentOS x64: sleep_thread test st.start: 0.000675 st.join: 2.006963 sleep alive: True spin_thread test sp.start: 0.000595 sp.join: 2.010066 sp alive: True factorial_thread test ft DONE: 4.475453 ft.start: 4.475589 ft.join: 4.475615 ft alive: False st DONE: 10.994519 sp DONE: 12.054668 I've tried this on python 2.6.5 on CentOS x64, 2.7.2 on Windows x86 and the factorial thread does not return from start on either of them until the thread is done executing. I've also tried this with PyPy 1.8.0 on Windows x86, and there result is slightly different. The start does return immediately, but then the join doesn't time out! sleep_thread test st.start: 0.001000 st.join: 2.001000 sleep alive: True spin_thread test sp.start: 0.000000 sp DONE: 0.197000 sp.join: 0.236000 sp alive: False factorial_thread test ft.start: 0.032000 ft DONE: 9.011000 ft.join: 9.012000 ft alive: False st DONE: 12.763000

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• Twisted: why is it that passing a deferred callback to a deferred thread makes the thread blocking a

  - by surtyaarthoughts

  I unsuccessfully tried using txredis (the non blocking twisted api for redis) for a persisting message queue I'm trying to set up with a scrapy project I am working on. I found that although the client was not blocking, it became much slower than it could have been because what should have been one event in the reactor loop was split up into thousands of steps. So instead, I tried making use of redis-py (the regular blocking twisted api) and wrapping the call in a deferred thread. It works great, however I want to perform an inner deferred when I make a call to redis as I would like to set up connection pooling in attempts to speed things up further. Below is my interpretation of some sample code taken from the twisted docs for a deferred thread to illustrate my use case: #!/usr/bin/env python from twisted.internet import reactor,threads from twisted.internet.task import LoopingCall import time def main_loop(): print 'doing stuff in main loop.. do not block me!' def aBlockingRedisCall(): print 'doing lookup... this may take a while' time.sleep(10) return 'results from redis' def result(res): print res def main(): lc = LoopingCall(main_loop) lc.start(2) d = threads.deferToThread(aBlockingRedisCall) d.addCallback(result) reactor.run() if __name__=='__main__': main() And here is my alteration for connection pooling that makes the code in the deferred thread blocking : #!/usr/bin/env python from twisted.internet import reactor,defer from twisted.internet.task import LoopingCall import time def main_loop(): print 'doing stuff in main loop.. do not block me!' def aBlockingRedisCall(x): if x<5: #all connections are busy, try later print '%s is less than 5, get a redis client later' % x x+=1 d = defer.Deferred() d.addCallback(aBlockingRedisCall) reactor.callLater(1.0,d.callback,x) return d else: print 'got a redis client; doing lookup.. this may take a while' time.sleep(10) # this is now blocking.. any ideas? d = defer.Deferred() d.addCallback(gotFinalResult) d.callback(x) return d def gotFinalResult(x): return 'final result is %s' % x def result(res): print res def aBlockingMethod(): print 'going to sleep...' time.sleep(10) print 'woke up' def main(): lc = LoopingCall(main_loop) lc.start(2) d = defer.Deferred() d.addCallback(aBlockingRedisCall) d.addCallback(result) reactor.callInThread(d.callback, 1) reactor.run() if __name__=='__main__': main() So my question is, does anyone know why my alteration causes the deferred thread to be blocking and/or can anyone suggest a better solution?

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• Very simple jquery ui drag and drop does not work. Why not?

  - by Catfish

  WHy doesn't this work? <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <style type="text/css"> #content { background:#CCCCCC; width:500px; height:500px; } #drop { height:200px; width:200px; background:#00FFFF; float:right; } #drag { background:#009966; width:100px; height:100px; float:left; } .active { background:#FFCC33; } </style> <script type="text/ecmascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script> <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.7.2/jquery-ui.min.js"></script> <script type="text/javascript"> $(document).ready(function() { $('#drag').draggable({ containment: '#content', scrollSensitivity: 60, revert: true, cursor: 'move' }); $('#drop').droppable({ accept: '#drag', drop: function(event, ui) { $(this).addClass('.active'); } }); }); </script> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>Untitled Document</title> </head> <body> <div id="content"> <div id="drag"> </div> <div id="drop"> </div> </div> </body> </html>

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• Why does my ko computed observable not update bound UI elements when its value changes?

  - by Allen

  I'm trying to wrap a cookie in a computed observable (which I'll later turn into a protectedObservable) and I'm having some problems with the computed observable. I was under the opinion that changes to the computed observable would be broadcast to any UI elements that have been bound to it. I've created the following fiddle JavaScript: var viewModel = {}; // simulating a cookie store, this part isnt as important var cookie = function () { // simulating a value stored in cookies var privateZipcode = "12345"; return { 'write' : function (val) { privateZipcode = val; }, 'read': function () { return privateZipcode; } } }(); viewModel.zipcode = ko.computed({ read: function () { return cookie.read(); }, write: function (value) { cookie.write(value); }, owner: viewModel }); ko.applyBindings(viewModel);? HTML: zipcode: <input type='text' data-bind="value: zipcode"> <br /> zipcode: <span data-bind="text: zipcode"></span>? I'm not using an observable to store privateZipcode since that's really just going to be in a cookie. I'm hoping that the ko.computed will provide the notifications and binding functionality that I need, though most of the examples I've seen with ko.computed end up using a ko.observable underneath the covers. Shouldn't the act of writing the value to my computed observable signal the UI elements that are bound to its value? Shouldn't these just update? Workaround I've got a simple workaround where I just use a ko.observable along side of my cookie store and using that will trigger the required updates to my DOM elements but this seems completely unnecessary, unless ko.computed lacks the signaling / dependency type functionality that ko.observable has. My workaround fiddle, you'll notice that the only thing that changes is that I added a seperateObservable that isn't used as a store, its only purpose is to signal to the UI that the underlying data has changed. // simulating a cookie store, this part isnt as important var cookie = function () { // simulating a value stored in cookies var privateZipcode = "12345"; // extra observable that isnt really used as a store, just to trigger updates to the UI var seperateObservable = ko.observable(privateZipcode); return { 'write' : function (val) { privateZipcode = val; seperateObservable(val); }, 'read': function () { seperateObservable(); return privateZipcode; } } }(); This makes sense and works as I'd expect because viewModel.zipcode depends on seperateObservable and updates to that should (and does) signal the UI to update. What I don't understand, is why doesn't a call to the write function on my ko.computed signal the UI to update, since that element is bound to that ko.computed? I suspected that I might have to use something in knockout to manually signal that my ko.computed has been updated, and I'm fine with that, that makes sense. I just haven't been able to find a way to accomplish that.

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• Why is my file being cleared if I don't save it?

  - by Kat

  My program is suppose to maintain a collection of Photos in a PhotoAlbum. It begins by reading a folder of photos and adds them to my PhotoAlbum. It then prints a menu that allows the user to list all the photos, add a photo, find a photo, save, and quit the program. Right now if I run my program it will add the 100 photos to the PhotoAlbum, but if I quit the program without saving, it clears the file I am reading from even if I haven't added a photo or done anything to the PhotoAlbum and I'm not sure why. Here is my method for printing to a file: private static void saveFile(PrintWriter writer) { String result; ArrayList<Photo> temp = album.getPhotoAlbum(); for (int i = 0; i < temp.size(); i++){ result = temp.get(i).toString() + "\n"; writer.println(result); } writer.close(); } And where the PrintWriter is instantiated: File file = new File(args[0] + File.separator + "album.dat"); try { PrintWriter fout = new PrintWriter(new FileWriter(file)); fileWriter = fout; } catch (IOException e){ System.out.println("ReadFromFile: Folder " + args[0] + " is not found."); System.exit(0); } And where it is called in my runMenu Method: private static void runMainMenu(Scanner scan) { String input; do { showMainMenu(); input = scan.nextLine().toLowerCase(); switch (input.charAt(0)) { case 'p': System.out.println(album.toString()); break; case 'a': album.addPhoto(readPhoto(scan, t)); break; case 'f': findMenu(scan); break; case 's': saveFile(fileWriter); System.exit(0); break; case 'q': break; default: System.out.println("Invalid entry: " + input.charAt(0)); break; } } while (!input.equalsIgnoreCase("q")); }

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• Why always fires OnFailure when return View() to Ajax Form ?

  - by Wahid Bitar

  I'm trying to make a log-in log-off with Ajax supported. I made some logic in my controller to sign the user in and then return simple partial containing welcome message and log-Off ActionLink my Action method looks like this : public ActionResult LogOn(LogOnModel model, string returnUrl) { if (ModelState.IsValid) { if (MembershipService.ValidateUser(model.UserName, model.Password)) { FormsService.SignIn(model.UserName, model.RememberMe); if (Request.IsAjaxRequest()) { //HERE IS THE PROBLEM :( return View("LogedInForm"); } else { if (!String.IsNullOrEmpty(returnUrl)) return Redirect(returnUrl); else return RedirectToAction("Index", "Home"); } } else { ModelState.AddModelError("", "The user name or password provided is incorrect."); if (Request.IsAjaxRequest()) { return Content("There were an error !"); } } } return View(model); } and I'm trying to return this simple partial : Welcome <b><%= Html.Encode(Model.UserName)%></b>! <%= Html.ActionLink("Log Off", "LogOff", "Account") %> and of-course the two partial are strongly-typed to LogOnModel. But if i returned View("PartialName") i always get OnFailure with status code 500. While if i returned Content("My Message") everything is going right. so please tell me why i always get this "StatusCode = 500" ??. where is the big mistake ??. By the way in my Site MasterPage i rendered partial to show long-on simple form this partial looks like this : <script type="text/javascript"> function ShowErrorMessage(ajaxContext) { var response = ajaxContext.get_response(); var statusCode = response.get_statusCode(); alert("Sorry, the request failed with status code " + statusCode); } function ShowSuccessMessage() { alert("Hey everything is OK!"); } </script> <div id="logedInDiv"> </div> <% using (Ajax.BeginForm("LogOn", "Account", new AjaxOptions { UpdateTargetId = "logedInDiv", InsertionMode = InsertionMode.Replace, OnSuccess = "ShowSuccessMessage", OnFailure = "ShowErrorMessage" })) { %> <%= Html.TextBoxFor(m => m.UserName)%> <%= Html.PasswordFor(m => m.Password)%> <%= Html.CheckBoxFor(m => m.RememberMe)%> <input type="submit" value="Log On" /> < <% } %>

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• Why do I get rows of zeros in my 2D fft?

  - by Nicholas Pringle

  I am trying to replicate the results from a paper. "Two-dimensional Fourier Transform (2D-FT) in space and time along sections of constant latitude (east-west) and longitude (north-south) were used to characterize the spectrum of the simulated flux variability south of 40degS." - Lenton et al(2006) The figures published show "the log of the variance of the 2D-FT". I have tried to create an array consisting of the seasonal cycle of similar data as well as the noise. I have defined the noise as the original array minus the signal array. Here is the code that I used to plot the 2D-FT of the signal array averaged in latitude: import numpy as np from numpy import ma from matplotlib import pyplot as plt from Scientific.IO.NetCDF import NetCDFFile ### input directory indir = '/home/nicholas/data/' ### get the flux data which is in ### [time(5day ave for 10 years),latitude,longitude] nc = NetCDFFile(indir + 'CFLX_2000_2009.nc','r') cflux_southern_ocean = nc.variables['Cflx'][:,10:50,:] cflux_southern_ocean = ma.masked_values(cflux_southern_ocean,1e+20) # mask land nc.close() cflux = cflux_southern_ocean*1e08 # change units of data from mmol/m^2/s ### create an array that consists of the seasonal signal fro each pixel year_stack = np.split(cflux, 10, axis=0) year_stack = np.array(year_stack) signal_array = np.tile(np.mean(year_stack, axis=0), (10, 1, 1)) signal_array = ma.masked_where(signal_array > 1e20, signal_array) # need to mask ### average the array over latitude(or longitude) signal_time_lon = ma.mean(signal_array, axis=1) ### do a 2D Fourier Transform of the time/space image ft = np.fft.fft2(signal_time_lon) mgft = np.abs(ft) ps = mgft**2 log_ps = np.log(mgft) log_mgft= np.log(mgft) Every second row of the ft consists completely of zeros. Why is this? Would it be acceptable to add a randomly small number to the signal to avoid this. signal_time_lon = signal_time_lon + np.random.randint(0,9,size=(730, 182))*1e-05 EDIT: Adding images and clarify meaning The output of rfft2 still appears to be a complex array. Using fftshift shifts the edges of the image to the centre; I still have a power spectrum regardless. I expect that the reason that I get rows of zeros is that I have re-created the timeseries for each pixel. The ft[0, 0] pixel contains the mean of the signal. So the ft[1, 0] corresponds to a sinusoid with one cycle over the entire signal in the rows of the starting image. Here are is the starting image using following code: plt.pcolormesh(signal_time_lon); plt.colorbar(); plt.axis('tight') Here is result using following code: ft = np.fft.rfft2(signal_time_lon) mgft = np.abs(ft) ps = mgft**2 log_ps = np.log1p(mgft) plt.pcolormesh(log_ps); plt.colorbar(); plt.axis('tight') It may not be clear in the image but it is only every second row that contains completely zeros. Every tenth pixel (log_ps[10, 0]) is a high value. The other pixels (log_ps[2, 0], log_ps[4, 0] etc) have very low values.

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• Why is my variable uninitialized in a separate if test?

  - by user2932733

  For the first run, I need to use dates that are six months prior to the last MySQL date $row_recent[0]. For all of the runs after 1, I am using a previous variable to store the previous date and then decrease the date by 6 months. I have confirmed that the first if test produces the expected result. (MySQL date - 6 Months). However, the second if test outputs $startdate6m as the PHP default due to $previous_6m being uninitialized. Any idea why it won't recognize $previous_6m = $initial6m? <?php while ($run_number < 15) { $run_number++; if($run_number == 1){ if ($month <= 06){ $year6m = date("Y", strtotime($row_recent[0]))-1; $month6m = str_pad((12-(6-date("m", strtotime($row_recent[0])))), 2, "0", STR_PAD_LEFT); $startdate6m = "'".$year6m."-".$month6m."-01'"; $end_date = $startdate6m; $initial6m = $startdate6m; } else{ $year6m = date("Y", strtotime($row_recent[0])); $month6m = str_pad(date("m", strtotime($row_recent[0]))-6, 2, "0", STR_PAD_LEFT); $startdate6m = "'".$year6m."-".$month6m."-01'"; $end_date = $startdate6m; $initial6m = $startdate6m; } } $previous_6m = $initial6m; if($run_number > 1){ # 6 Month # Decrement date by 6 months $month6m = date("m", strtotime($previous_6m)); if ($month6m <= 06){ $year6m = date("Y", strtotime($previous_6m))-1; $month6m = str_pad((12-(6-date("m", strtotime($previous_6m)))), 2, "0", STR_PAD_LEFT); $startdate6m = "'".$year6m."-".$month6m."-01'"; $end_date = $startdate6m; } else{ $year6m = date("Y", strtotime($previous_6m)); $month6m = str_pad(date("m", strtotime($previous_6m))-6, 2, "0", STR_PAD_LEFT); $startdate6m = "'".$year6m."-".$month6m."-01'"; $end_date = $startdate6m; } } $previous_6m = $startdate6m; } ?>

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• Why is this simple file upload not working? JSF

  - by Nitesh Panchal

  Hello, Why is this code not working? I always get size() = 0, whenever i upload file. xhtml file :- <?xml version='1.0' encoding='UTF-8' ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:h="http://java.sun.com/jsf/html"> <h:head> <title>Abc</title> </h:head> <h:body> <center> <form method="post" enctype="multipart/form-data" id="form" action="/upload/uploadFile"> <input type="file"/> <br/> <input type="Submit" value="upload"/> </form> </center> </h:body> </html> This is my servlet :- package servlets; import java.io.IOException; import java.util.List; import java.util.logging.Level; import java.util.logging.Logger; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.apache.commons.fileupload.FileItem; import org.apache.commons.fileupload.FileUploadException; import org.apache.commons.fileupload.disk.DiskFileItemFactory; import org.apache.commons.fileupload.servlet.ServletFileUpload; @WebServlet(name="uploadFile", urlPatterns={"/uploadFile"}) public class uploadFile extends HttpServlet { protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException, FileUploadException { System.out.println("executed!"); List<FileItem> items = new ServletFileUpload(new DiskFileItemFactory()).parseRequest(request); System.out.println(items.size()); for (FileItem item : items) { if (!item.isFormField()) { System.out.println("Name: " + item.getName()); System.out.println("Size: " + item.getSize()); System.out.println("Type: " + item.getContentType()); } } } @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { try { processRequest(request, response); } catch (FileUploadException ex) { ex.printStackTrace(); } } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { try { processRequest(request, response); } catch (FileUploadException ex) { ex.printStackTrace(); } } @Override public String getServletInfo() { return "Short description"; } }

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• Why does my JSF + Spring web application output JSF source code instead of interpreted HTML page?

  - by Corvus

  I'm new to both JSF and Spring Framework and I'm trying to figure out how to make them work together. My current problem is that application outputs my JSF files without interpreting them. Here are some snippets of my code which I believe might be relevant: dispatcher-servlet.xml <bean id="urlMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping"> <property name="mappings"> <props> <prop key="login.htm">loginController</prop> </props> </property> </bean> <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver" p:prefix="/WEB-INF/pages/" p:suffix=".xhtml" /> <bean name="loginController" class="controller.LoginController" /> loginController public class LoginController extends MultiActionController { public ModelAndView login(HttpServletRequest request, HttpServletResponse response) throws Exception { System.out.println("LOGIN"); return new ModelAndView("login"); } WEB-INF/pages/login.xhtml <?xml version='1.0' encoding='UTF-8' ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:h="http://java.sun.com/jsf/html"> <h:head> <title>#{message.log}</title> </h:head> <h:body> <h:form> <h:outputLabel value="#{message.username}" for="userName"> <h:inputText id="userName" value="#{User.name}" /> </h:outputLabel> <h:commandButton value="#{message.loggin}" action="#{User.login}" /> </h:form> </h:body> </html> Any ideas where the problem might be? Does this code make any sense at all? I'm well aware of fact, that probably completely sucks and I'll be glad to here WHY it sucks and how to make it better. Thanks :)

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• An AuthLogic form is giving me incorrect validation errors -- why?

  - by sscirrus

  Hi everyone, I set up AuthLogic for Rails according to the AuthLogic example: http://github.com/binarylogic/authlogic_example. I can log on successfully to the system, but when accessing users/new.html.erb to register a new user, the form returns the following validation errors: Email is too short (minimum is 6 characters) Email should look like an email address. Login is too short (minimum is 3 characters) Login should use only letters, numbers, spaces, and .-_@ please. Password is too short (minimum is 4 characters) Password confirmation is too short (minimum is 4 characters) None of these errors exist in the data I am entering. # new.html.erb <%= form.label :login, nil, :class => "label" %><br /> <%= form.text_field :login, :class => "inputBox", :name => "login", :type => "text" %><br /> <%= form.label :password, form.object.new_record? ? nil : "Change password", :class => "label" %><br /> <%= form.password_field :password, :class => "inputBox", :name => "password", :type => "text" %><br /> <%= form.label "Confirm password", nil, :class => "label" %><br /> <%= form.password_field :password_confirmation, :class => "inputBox", :name => "password_confirmation", :type => "text" %><br /> <%= form.label :email, nil, :class => "label" %><br /> <%= form.text_field :email, :class => "inputBox", :name => "email", :type => "text" %><br /> # Users controller def new @user = User.new render :layout => "forms" end I think the problem is that the data isn't being transferred somehow and therefore AuthLogic doesn't think the inputs are sufficient. Do you have any idea why AuthLogic is telling me the data doesn't satisfy its validation?

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• Why is javac 1.5 running so slowly compared with the Eclipse compiler?

  - by Simon Nickerson

  I have a Java Maven project with about 800 source files (some generated by javacc/JTB) which is taking a good 25 minutes to compile with javac. When I changed my pom.xml over to use the Eclipse compiler, it takes about 30 seconds to compile. Any suggestions as to why javac (1.5) is running so slowly? (I don't want to switch over to the Eclipse compiler permanently, as the plugin for Maven seems more than a little buggy.) I have a test case which easily reproduces the problem. The following code generates a number of source files in the default package. If you try to compile ImplementingClass.java with javac, it will seem to pause for an inordinately long time. import java.io.File; import java.io.FileNotFoundException; import java.io.PrintStream; public class CodeGenerator { private final static String PATH = System.getProperty("java.io.tmpdir"); private final static int NUM_TYPES = 1000; public static void main(String[] args) throws FileNotFoundException { PrintStream interfacePs = new PrintStream(PATH + File.separator + "Interface.java"); PrintStream abstractClassPs = new PrintStream(PATH + File.separator + "AbstractClass.java"); PrintStream implementingClassPs = new PrintStream(PATH + File.separator + "ImplementingClass.java"); interfacePs.println("public interface Interface<T> {"); abstractClassPs.println("public abstract class AbstractClass<T> implements Interface<T> {"); implementingClassPs.println("public class ImplementingClass extends AbstractClass<Object> {"); for (int i=0; i<NUM_TYPES; i++) { String nodeName = "Node" + i; PrintStream nodePs = new PrintStream(PATH + File.separator + nodeName + ".java"); nodePs.printf("public class %s { }\n", nodeName); nodePs.close(); interfacePs.printf("void visit(%s node, T obj);%n", nodeName); abstractClassPs.printf("public void visit(%s node, T obj) { System.out.println(obj.toString()); }%n", nodeName); } interfacePs.println("}"); abstractClassPs.println("}"); implementingClassPs.println("}"); interfacePs.close(); abstractClassPs.close(); implementingClassPs.close(); } }

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• Why an object declared in method is subject to garbage collection before the method returns?

  - by SiLent SoNG

  Consider an object declared in a method: public void foo() { final Object obj = new Object(); // A long run job that consumes tons of memory and // triggers garbage collection } Will obj be subject to garbage collection before foo() returns? UPDATE: Previously I thought obj is not subject to garbage collection until foo() returns. However, today I find myself wrong. I have spend several hours in fixing a bug and finally found the problem is caused by obj garbage collected! Can anyone explain why this happens? And if I want obj to be pinned how to achieve it? Here is the code that has problem. public class Program { public static void main(String[] args) throws Exception { String connectionString = "jdbc:mysql://<whatever>"; // I find wrap is gc-ed somewhere SqlConnection wrap = new SqlConnection(connectionString); Connection con = wrap.currentConnection(); Statement stmt = con.createStatement(ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY); stmt.setFetchSize(Integer.MIN_VALUE); ResultSet rs = stmt.executeQuery("select instance_id, doc_id from crawler_archive.documents"); while (rs.next()) { int instanceID = rs.getInt(1); int docID = rs.getInt(2); if (docID % 1000 == 0) { System.out.println(docID); } } rs.close(); //wrap.close(); } } After running the Java program, it will print the following message before it crashes: 161000 161000 ******************************** Finalizer CALLED!! ******************************** ******************************** Close CALLED!! ******************************** 162000 Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: And here is the code of class SqlConnection: class SqlConnection { private final String connectionString; private Connection connection; public SqlConnection(String connectionString) { this.connectionString = connectionString; } public synchronized Connection currentConnection() throws SQLException { if (this.connection == null || this.connection.isClosed()) { this.closeConnection(); this.connection = DriverManager.getConnection(connectionString); } return this.connection; } protected void finalize() throws Throwable { try { System.out.println("********************************"); System.out.println("Finalizer CALLED!!"); System.out.println("********************************"); this.close(); } finally { super.finalize(); } } public void close() { System.out.println("********************************"); System.out.println("Close CALLED!!"); System.out.println("********************************"); this.closeConnection(); } protected void closeConnection() { if (this.connection != null) { try { connection.close(); } catch (Throwable e) { } finally { this.connection = null; } } } }

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• Still failing a function, not sure why...ideas on test cases to run?

  - by igor

  I've been trying to get this Sudoku game working, and I am still failing some of the individual functions. All together the game works, but when I run it through an "autograder", some test cases fail.. Currently I am stuck on the following function, placeValue, failing. I do have the output that I get vs. what the correct one should be, but am confused..what is something going on? EDIT: I do not know what input/calls they make to the function. What happens is that "invalid row" is outputted after every placeValue call, and I can't trace why.. Here is the output (mine + correct one) if it's at all helpful: http://pastebin.com/Wd3P3nDA Here is placeValue, and following is getCoords that placeValue calls.. void placeValue(Square board[BOARD_SIZE][BOARD_SIZE]) { int x,y,value; if(getCoords(x,y)) { cin>>value; if(board[x][y].permanent) { cout<< endl << "That location cannot be changed"; } else if(!(value>=1 && value<=9)) { cout << "Invalid number"<< endl; clearInput(); } else if(validMove(board, x, y, value)) { board[x][y].number=value; } } } bool getCoords(int & x, int & y) { char row; y=0; cin>>row>>y; x = static_cast<int>(toupper(row)); if (isalpha(row) && (x >= 'A' && x <= 'I') && y >= 1 && y <= 9) { x = x - 'A'; // converts x from a letter to corresponding index in matrix y = y - 1; // converts y to corresponding index in matrix return (true); } else if (!(x >= 'A' && x <= 'I')) { cout<<"Invalid row"<<endl; clearInput(); return false; } else { cout<<"Invalid column"<<endl; clearInput(); return false; } }

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• Why does this textbox binding example work in WPF but not in Silverlight?

  - by Edward Tanguay

  Why is it in the following silverlight application that when I: change the default text in the first textbox move the cursor to the second text box (i.e. take focus off first textbox) click the button that inside the button handler, it still has the old value "default text"? What do I have to do to get the binding to work in Silverlight? The same code works fine in WPF. XAML: <UserControl x:Class="TestUpdate123.MainPage" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" d:DesignWidth="640" d:DesignHeight="480"> <StackPanel Margin="10" HorizontalAlignment="Left"> <TextBox Text="{Binding InputText}" Height="200" Width="600" Margin="0 0 0 10"/> <StackPanel HorizontalAlignment="Left"> <Button Content="Convert" Click="Button_Convert_Click" Margin="0 0 0 10"/> </StackPanel> <TextBox Height="200" Width="600" Margin="0 0 0 10"/> <TextBlock Text="{Binding OutputText}"/> </StackPanel> </UserControl> Code Behind: using System.Windows; using System.Windows.Controls; using System.ComponentModel; namespace TestUpdate123 { public partial class MainPage : UserControl, INotifyPropertyChanged { #region ViewModelProperty: InputText private string _inputText; public string InputText { get { return _inputText; } set { _inputText = value; OnPropertyChanged("InputText"); } } #endregion #region ViewModelProperty: OutputText private string _outputText; public string OutputText { get { return _outputText; } set { _outputText = value; OnPropertyChanged("OutputText"); } } #endregion public MainPage() { InitializeComponent(); DataContext = this; InputText = "default text"; } private void Button_Convert_Click(object sender, RoutedEventArgs e) { OutputText = InputText; } #region INotifiedProperty Block public event PropertyChangedEventHandler PropertyChanged; protected void OnPropertyChanged(string propertyName) { PropertyChangedEventHandler handler = PropertyChanged; if (handler != null) { handler(this, new PropertyChangedEventArgs(propertyName)); } } #endregion } }

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• Why does firefox round-trip to the server to determine whether my files are modifed?

  - by erikkallen

  I have some static content on my web site that I have set up caching for (using Asp.NET MVC). According to Firebug, the first time I open the page, Firefox sends this request: GET /CoreContent/Core.css?asm=0.7.3614.34951 Host: 127.0.0.1:3916 User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5 (.NET CLR 3.5.30729) Accept: text/css,*/*;q=0.1 Accept-Language: en-us,en;q=0.5 Accept-Encoding: gzip,deflate Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7 Keep-Alive: 300 Connection: keep-alive Referer: http://127.0.0.1:3916/Edit/1/101 Cookie: .ASPXAUTH=52312E5A802C1A079E2BA29AA2BFBC5A38058977B84452D62ED52855D4164659B4307661EC73A307BFFB2ED3871C67CB3A9AAFDB3A75A99AC0A21C63A6AADE9A11A7138C672E75125D9FF3EFFBD9BF62 Pragma: no-cache Cache-Control: no-cache Which my server replies to with this: Server: ASP.NET Development Server/9.0.0.0 Date: Mon, 23 Nov 2009 18:44:41 GMT X-AspNet-Version: 2.0.50727 X-AspNetMvc-Version: 1.0 Cache-Control: public, max-age=31535671 Expires: Tue, 23 Nov 2010 18:39:12 GMT Last-Modified: Mon, 23 Nov 2009 18:39:12 GMT Vary: * Content-Type: text/css Content-Length: 15006 Connection: Close So far, so good. However, if I refresh Firefox (not a cache-clearing refresh, just a normal one), during that refresh cycle Firefox will once again go to the server with this request: GET /CoreContent/Core.css?asm=0.7.3614.34951 Host: 127.0.0.1:3916 User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5 (.NET CLR 3.5.30729) Accept: text/css,*/*;q=0.1 Accept-Language: en-us,en;q=0.5 Accept-Encoding: gzip,deflate Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7 Keep-Alive: 300 Connection: keep-alive Referer: http://127.0.0.1:3916/Edit/1/101 Cookie: .ASPXAUTH=52312E5A802C1A079E2BA29AA2BFBC5A38058977B84452D62ED52855D4164659B4307661EC73A307BFFB2ED3871C67CB3A9AAFDB3A75A99AC0A21C63A6AADE9A11A7138C672E75125D9FF3EFFBD9BF62 If-Modified-Since: Mon, 23 Nov 2009 18:39:20 GMT Cache-Control: max-age=0 to which my server responds 304 Not Modified. Why does Firefox issue this second request? In the first response, I said that the cache does not expire for a year (I intend to use query parameters whenever things change). Do I have to add another response header to prevent this extra roundtrip? Edit: It does not matter whether I press refresh, or whether I go to the page again (or a different URL, which references the same external files). Firefox does the same again. Also, I don't claim this to be a bug in FF, I just wonder if there is another header I can set which means "This document will never change, don't bother me again".

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• Why I can't draw in a loop? (Using UIView in iPhone)

  - by Tattat

  I can draw many things using this : NSString *imagePath = [[NSBundle mainBundle] pathForResource:@"dummy2.png" ofType:nil]; UIImage *img = [UIImage imageWithContentsOfFile:imagePath]; image = CGImageRetain(img.CGImage); CGRect imageRect; double x = 0; double y = 0; for (int k=0; k<someValue; k++) { x += k; y += k; imageRect.origin = CGPointMake(x, y); imageRect.size = CGSizeMake(25, 25); CGContextDrawImage(UIGraphicsGetCurrentContext(), imageRect, image); } } CGImageRelease(img.CGImage); So, it works, so, I put it into a command object's execute method. Then, I want to do similar thing, but this time, my execute method only do this: NSString *imagePath = [[NSBundle mainBundle] pathForResource:@"dummy2.png" ofType:nil]; UIImage *img = [UIImage imageWithContentsOfFile:imagePath]; image = CGImageRetain(img.CGImage); CGRect imageRect; double x = inComingX; double y = inComingY; imageRect.origin = CGPointMake(x, y); imageRect.size = CGSizeMake(25, 25); CGContextDrawImage(UIGraphicsGetCurrentContext(), imageRect, image); CGImageRelease(img.CGImage); This time, this is also a Command, and it is the execute method. But I take the for loop away. I will have another method that pass the inComingX , and inComingY into my Command object. My Drawing method is simply execute the Cmd that passed in my drawingEngine: -(void)drawInContext:(CGContextRef)context { [self.cmdToBeExecuted execute]; } I also have the assign method to assign the command,: -(void)assignCmd:(Command* )cmd{ self.cmdToBeExecuted = cmd; } And this is the way I called the drawingEngine for(int k=0; k<5; k++){ [self.drawingEngine assignCmd:[DrawingCmd setDrawingInformation:(10*k):0:@"dummy.png"]]; [self.drawingEngine setNeedsDisplay]; } It can draw, but the sad thing is it only draw the last one. Why? and how to fix it? I can draw all the things in my First code, but after I take the loop outside, and use the loop in last code, it just only draw the last one. Plz help

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• Implicit vs explicit getters/setters in AS3, which to use and why?

  - by James

  Since the advent of AS3 I have been working like this: private var loggy:String; public function getLoggy ():String { return loggy; } public function setLoggy ( loggy:String ):void { // checking to make sure loggy's new value is kosher etc... this.loggy = loggy; } and have avoided working like this: private var _loggy:String; public function get loggy ():String { return loggy; } public function set loggy ( loggy:String ):void { // checking to make sure loggy's new value is kosher etc... this.loggy = loggy; } I have avoided using AS3's implicit getters/setters partly so that I can just start typing "get.." and content assist will give me a list of all my getters, and likewise for my setters. I also dislike underscores in my code which turned me off the implicit route. Another reason is that I prefer the feel of this: whateverObject.setLoggy( "loggy's awesome new value!" ); to this: whateverObject.loggy = "loggy's awesome new value!"; I feel that the former better reflects what is actually happening in the code. I am calling functions, not setting values directly. After installing Flash Builder and the great new plugin SourceMate ( which helps to get some of the useful features that FDT is famous into FB ) I realized that when I use SourceMate's "generate getters and setters" feature it automatically sets my code up using the implicit route: private var _loggy:String; public function get loggy ():String { return loggy; } public function set loggy ( loggy:String ):void { // do whatever is needed to check to make sure loggy is an acceptable value this.loggy = loggy; } I figure that these SourceMate people must know what they are doing or they wouldn't be writing workflow enhancement plugins for coding in AS3, so now I am questioning my ways. So my question to you is: Can anyone give me a good reason why I should give up my explicit g/s ways, start using the implicit technique, and embrace those stinky little _underscores for my private vars? Or back me up in my reasons for doing things the way that I do?

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• Why does my Spring Controller direct me to the wrong page?

  - by kc2001

  I am writing my first Spring 3.0.5 MVC app and am confused about why my controller mappings aren't doing what I expect. I have a VerifyPasswordController that is called after a user tries to log in by entering his name and password. // Called upon clicking "submit" from /login @RequestMapping(value = "/verifyPassword", method = RequestMethod.POST) @ModelAttribute("user") public String verifyPassword(User user, BindingResult result) { String email = user.getEmail(); String nextPage = CHOOSE_OPERATION_PAGE; // success case if (result.hasErrors()) { nextPage = LOGIN_PAGE; } else if (!passwordMatches(email, user.getPassword())) { nextPage = LOGIN_FAILURE_PAGE; } else { // success } return nextPage; } I can verify in the debugger that this method is being called, but afterwards, the verifyPassword page is displayed rather than the chooseOperation page. The console output of WebLogic seems to show that my mapping are correct: INFO : org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping - Mapped URL path [/chooseOperation] onto handler 'chooseOperationController' INFO : org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping - Mapped URL path [/chooseOperation.*] onto handler 'chooseOperationController' INFO : org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping - Mapped URL path [/chooseOperation/] onto handler 'chooseOperationController' Here is the ChooseOperationController: @Controller @SessionAttributes("leaveRequestForm") public class ChooseOperationController implements PageIfc, AttributeIfc { @RequestMapping(value = "/chooseOperation") @ModelAttribute("leaveRequestForm") public LeaveRequest setUpLeaveRequestForm( @RequestParam(NAME_ATTRIBUTE) String name) { LeaveRequest form = populateFormFromDatabase(name); return form; } // helper methods omited } I welcome any advice, particularly "generic" techniques for debugging such mapping problems. BTW, I've also tried to "redirect" to the desired page, but got the same result. servlet-context.xml: <?xml version="1.0" encoding="UTF-8"?> <beans:beans xmlns="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:beans="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation=" http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd"> <!-- DispatcherServlet Context: defines this servlet's request-processing infrastructure --> <!-- Enables the Spring MVC @Controller programming model --> <annotation-driven /> <!-- Handles HTTP GET requests for /resources/** by efficiently serving up static resources in the ${webappRoot}/resources directory --> <resources mapping="/resources/**" location="/resources/" /> <!-- Resolves views selected for rendering by @Controllers to .jsp resources in the /WEB-INF/views directory --> <beans:bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <beans:property name="prefix" value="/WEB-INF/views/" /> <beans:property name="suffix" value=".jsp" /> </beans:bean> <context:component-scan base-package="com.engilitycorp.leavetracker" /> <beans:bean id="leaveRequestForm" class="com.engilitycorp.leavetracker.model.LeaveRequest" /> </beans:beans> The constants: String LOGIN_FAILURE_PAGE = "loginFailure"; String LOGIN_PAGE = "login"; String CHOOSE_OPERATION_PAGE = "chooseOperation";

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• maven-ear-plugin works if jboss version is 4.2, but not 5. Why ?

  - by NSINGH

  I am using maven to configure maven-ear-plugin. I am getting following exception when I say jboss version is 5 (See below code, under tag). It works if I replace version to 4.2 <build> <finalName>tactical</finalName> <plugins> <plugin> <artifactId>maven-ear-plugin</artifactId> <configuration> <version>5</version> <defaultJavaBundleDir>lib</defaultJavaBundleDir> <jboss> <version>5</version> <loader-repository>seam.jboss.org:loader=tactical</loader-repository> </jboss> <modules> <ejbModule> <groupId>${project.groupId}</groupId> <artifactId>tactical-jar</artifactId> </ejbModule> </modules> </configuration> </plugin> </plugins> </build> Why it works fine for jboss 4.2 but not for 5. What ?? I get the following exception: [INFO] Failed to initialize JBoss configuration Embedded error: Invalid JBoss configuration, version[5] is not supported. [INFO] ------------------------------------------------------------------------ [INFO] Trace org.apache.maven.lifecycle.LifecycleExecutionException: Failed to initialize JBoss configuration at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:583) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalWithLifecycle(DefaultLifecycleExecutor.java:49 9) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoal(DefaultLifecycleExecutor.java:478) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalAndHandleFailures(DefaultLifecycleExecutor.jav a:330) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeTaskSegments(DefaultLifecycleExecutor.java:291) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:142) at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:336) at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:129) at org.apache.maven.cli.MavenCli.main(MavenCli.java:287) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:315) at org.codehaus.classworlds.Launcher.launch(Launcher.java:255) at org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:430) at org.codehaus.classworlds.Launcher.main(Launcher.java:375) Caused by: org.apache.maven.plugin.MojoExecutionException: Failed to initialize JBoss configuration at org.apache.maven.plugin.ear.AbstractEarMojo.execute(AbstractEarMojo.java:159) at org.apache.maven.plugin.ear.GenerateApplicationXmlMojo.execute(GenerateApplicationXmlMojo.java:96) at org.apache.maven.plugin.DefaultPluginManager.executeMojo(DefaultPluginManager.java:451) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:558) ... 16 more Caused by: org.apache.maven.plugin.ear.EarPluginException: Invalid JBoss configuration, version[5] is not supported. at org.apache.maven.plugin.ear.JbossConfiguration.(JbossConfiguration.java:95) at org.apache.maven.plugin.ear.AbstractEarMojo.initializeJbossConfiguration(AbstractEarMojo.java:296) at org.apache.maven.plugin.ear.AbstractEarMojo.execute(AbstractEarMojo.java:155) ... 19 more [INFO] ------------------------------------------------------------------------ [INFO] Total time: 2 seconds Any idea. Thanks

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• Is "for(;;)" faster than "while (TRUE)"? If not, why do people use it?

  - by Chris Cooper

  for (;;) { //Something to be done repeatedly } I have seen this sort of thing used a lot, but I think it is rather strange... Wouldn't it be much clearer to say while (TRUE), or something along those lines? I'm guessing that (as is the reason for many-a-programmer to resort to cryptic code) this is a tiny margin faster? Why, and is it REALLY worth it? If so, why not just define it this way: #DEFINE while(TRUE) for(;;)

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• Why doesen't the number 2 work in this for-loop?

  - by Emil

  Hello. I have a function that runs trough each element in an array. It's hard to explain, so I'll just paste in the code here: NSLog(@"%@", arraySub); for (NSString *string in arrayFav){ int favoriteLoop = [string intValue] + favCount; NSLog(@"%d", favoriteLoop); id arrayFavObject = [array objectAtIndex:favoriteLoop]; [arrayFavObject retain]; [array removeObjectAtIndex:favoriteLoop]; [array insertObject:arrayFavObject atIndex:0]; [arrayFavObject release]; id arraySubFavObject = [arraySub objectAtIndex:favoriteLoop]; [arraySubFavObject retain]; [arraySub removeObjectAtIndex:favoriteLoop]; [arraySub insertObject:arraySubFavObject atIndex:0]; [arraySubFavObject release]; id arrayLengthFavObject = [arrayLength objectAtIndex:favoriteLoop]; [arrayLengthFavObject retain]; [arrayLength removeObjectAtIndex:favoriteLoop]; [arrayLength insertObject:arrayLengthFavObject atIndex:0]; [arrayLengthFavObject release]; } NSLog(@"%@", arraySub); The array arrayFav contains these strings: "3", "8", "2", "10", "40". Array array contains 92 strings with a name. Array arraySub contains numbers 0 to 91, representing a filename with a title from the array array. Array arrayLength contains 92 strings representing the size of each file from array arraySub. Now, the first NSLog shows, as expected, the numbers 0 to 91. The NSLog-s in the loop shows the numbers 3, 8, 2, 10, 40, also as expected. But here's the odd part: the last NSLog shows these numbers: 40, 10, 0, 8, 3, 1, 2, 4, 5, 6, 7, 9, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91 that is 40, 10, 0, 8, 3, and so on. It was not supposed to be a zero in there, it was supposed to be a 2.. Do you have any idea at why this is happening or a way to fix it? Thank you.

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• Why are static classes considered “classes” and “reference types”?

  - by Timwi

  I’ve been pondering about the C# and CIL type system today and I’ve started to wonder why static classes are considered classes. There are many ways in which they are not really classes: A “normal” class can contain non-static members, a static class can’t. In this respect, a class is more similar to a struct than it is to a static class, and yet structs have a separate name. You can have a reference to an instance of a “normal” class, but not a static class (despite it being considered a “reference type”). In this respect, a class is more similar to an interface than it is to a static class, and yet interfaces have a separate name. The name of a static class can never be used in any place where a type name would normally fit: you can’t declare a variable of this type, you can’t use it as a base type, and you can’t use it as a generic type parameter. In this respect, static classes are somewhat more like namespaces. A “normal” class can implement interfaces. Once again, that makes classes more similar to structs than to static classes. A “normal” class can inherit from another class. It is also bizarre that static classes are considered to derive from System.Object. Although this allows them to “inherit” the static methods Equals and ReferenceEquals, the purpose of that inheritance is questionable as you would call those methods on object anyway. C# even allows you to specify that useless inheritance explicitly on static classes, but not on interfaces or structs, where the implicit derivation from object and System.ValueType, respectively, actually has a purpose. Regarding the subset-of-features argument: Static classes have a subset of the features of classes, but they also have a subset of the features of structs. All of the things that make a class distinct from the other kinds of type, do not seem to apply to static classes. Regarding the typeof argument: Making a static class into a new and different kind of type does not preclude it from being used in typeof. Given the sheer oddity of static classes, and the scarcity of similarities between them and “normal” classes, shouldn’t they have been made into a separate kind of type instead of a special kind of class?

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• Why doesn't the .click() not work in this instance?

  - by Deshiknaves

  Basically what this does is fadeIn pre-existing divs and then loads an image. When the image is loaded it then appends that into one of the pre-existing divs. Then it appends a new div with an id of xButton. Then later it $('#xButton').click() should hide the 3 divs. However it just doesn't work. If I change the click() to either #modalImage or #overlay, it works but just not for the #xButton. I would really like to figure out why its not working and how I should be doing this instead. Thanks. $(function(){ $('#container a').click(function(e){ e.preventDefault(); var id = $(this).attr('href'), img = new Image(); $('#overlay').fadeIn(function(){ $('#modalImage').fadeIn(); }); $(img).load(function(){ $(this).hide(); $('#modalImage').removeClass('loader').append(this); $(this).fadeIn(function(){ var ih = $(this).outerHeight(), iw = $(this).outerWidth(), newH = ($(window).height()/10)*7, newW = ($(window).width()/10)*7; if (ih >= iw && ih >= newH) { $(this).css('height',newH + 'px'); $(this).css('width', 'auto'); } else if (ih >= iw && newH > ih) { $(this).css('height', ih + 'px'); $(this).css('width', 'auto'); } else if (iw > ih && iw >= newW) { if ((newW / (iw / ih)) > newH) { $(this).css('width', 'auto'); $(this).css('height', newH + 'px'); } else { $(this).css('width', newW + 'px'); $(this).css('height', 'auto'); } } else { $(this).css('width', iw + 'px'); $(this).css('height', 'auto'); } var padW = ($(window).width() - $(this).outerWidth()) / 2, padH = ($(window).height() - $(this).outerHeight()) / 2; console.log (padH + ' ' + padW); $(this).css('top', padH); $(this).css('left', padW); if($('#overlay').is(":visible") == true) { ih = ih + 4; $('<div id="xButton">x</div>').appendTo('#modalImage'); if (padH >= 0) { $('#xButton').css('top', padH - 4).css('right', padW - 65); } else { $('#xButton').css('top', '20px').css('right', padW - 65); } } }); }).attr('src', id); }); $('#xButton').click(function(){ $(this).hide(); $('#overlay').fadeOut(function(){ $('#modalImage img').css('top', '-9999px').remove(); $('#xButton').remove(); $('#modalImage').addClass('loader'); }); }); });

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