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• Keeping WPF grids from getting out of parent bounds

  - by Jonathan Perry

  In my UI, I have a big grid with two columns and one row. in the right column, I have a grid with three rows where in the top row I have a user control, and in the two bottom rows I have two Expander objects, each containing an ItemsControl with a list that gets populated in runtime. Sometimes, that list gets really long and "spills" from the screen towards the bottom. What I want to do is to allow the user to see both expanders, be able to expand or collapse them while keeping them both in sight. I tried wrapping them in WrapPanels or StackPanel but to no avail. Here's some code to help explain my problem: <Grid Grid.Row="1" x:Name="grid1"> <Grid.RowDefinitions> <RowDefinition Height="*" /> <RowDefinition Height="*" /> </Grid.RowDefinitions> <Expander Grid.Row="0" Header="Expander 1" x:Name="expander1" FontSize="14" IsExpanded="True"> <Expander.Background> <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0"> <GradientStop Color="#FFC4C4C4" Offset="0" /> <GradientStop Color="White" Offset="1" /> </LinearGradientBrush> </Expander.Background> <ContentPresenter Content="{Binding ViewModel.OpenAlerts, ElementName=m_viewControl}" ClipToBounds="True"/> </Expander> <Expander Grid.Row="1" x:Name="expander2" Header="Expander 2" FontSize="14" IsExpanded="True"> <Expander.Background> <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0"> <GradientStop Color="#FFC4C4C4" Offset="0" /> <GradientStop Color="White" Offset="1" /> </LinearGradientBrush> </Expander.Background> <ContentPresenter Content="{Binding ViewModel.ClosedAlerts, ElementName=m_viewControl}" ClipToBounds="True"/> </Expander> </Grid> Any assistance or tips will be highly appreciated! Thanks, John.

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• Rails 3.1 text_field form helper and jQuery datepicker date format

  - by DanyW

  I have a form field in my Rails view like this: <%= f.text_field :date, :class => "datepicker" %> A javascript function converts all input fields of that class to a jQueryUI datepicker. $(".datepicker").datepicker({ dateFormat : "dd MM yy", buttonImageOnly : true, buttonImage : "<%= asset_path('iconDatePicker.gif') %>", showOn : "both", changeMonth : true, changeYear : true, yearRange : "c-20:c+5" }) So far so good. I can edit the record and it persists the date correctly all the way to the DB. My problem is when I want to edit the record again. When the form is pre-populated from the record it displays in 'yyyy-mm-dd' format. The javascript only formats dates which are selected in the datepicker control. Is there any way I can format the date retrieved from the database? At which stage can I do this? Thanks, Dany. Some more details following the discussion below, my form is spread across two files, a view and a partial. Here's the view: <%= form_tag("/shows/update_individual", :method => "put") do %> <% for show in @shows %> <%= fields_for "shows[]", show do |f| %> <%= render "fields", :f => f %> <% end %> <% end %> <%= submit_tag "Submit"%> <% end %> And here's the _fields partial view: <p> <%= f.label :name %> <%= f.text_field :name %> </p> <p> <%= f.date %> <%= f.label :date %> <%= f.text_field :date, :class => "datepicker" %> </p> Controller code: def edit_individual @shows = Show.find(params[:show_ids]) end

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• Problem with memory leaks

  - by user191723

  Sorry, having difficulty formattin code to appear correct here??? I am trying to understand the readings I get from running instruments on my app which are telling me I am leaking memory. There are a number, quite a few in fact, that get reported from inside the Foundation, AVFoundation CoreGraphics etc that I assume I have no control over and so should ignore such as: Malloc 32 bytes: 96 bytes, AVFoundation, prepareToRecordQueue or Malloc 128 bytes: 128 bytes, CoreGraphics, open_handle_to_dylib_path Am I correct in assuming these are something the system will resolve? But then there are leaks that are reported that I believe I am responsible for, such as: This call reports against this line leaks 2.31KB [self createAVAudioRecorder:frameAudioFile]; Immediately followed by this: -(NSError*) createAVAudioRecorder: (NSString *)fileName { // flush recorder to start afresh [audioRecorder release]; audioRecorder = nil; // delete existing file to ensure we have clean start [self deleteFile: fileName]; VariableStore *singleton = [VariableStore sharedInstance]; // get full path to target file to create NSString *destinationString = [singleton.docsPath stringByAppendingPathComponent: fileName]; NSURL *destinationURL = [NSURL fileURLWithPath: destinationString]; // configure the recording settings NSMutableDictionary *recordSettings = [[NSMutableDictionary alloc] initWithCapacity:6]; //****** LEAKING 384 BYTES [recordSettings setObject:[NSNumber numberWithInt:kAudioFormatLinearPCM] forKey: AVFormatIDKey]; //***** LEAKING 32 BYTES float sampleRate = 44100.0; [recordSettings setObject:[NSNumber numberWithFloat: sampleRate] forKey: AVSampleRateKey]; //***** LEAKING 48 BYTES [recordSettings setObject:[NSNumber numberWithInt:2] forKey:AVNumberOfChannelsKey]; int bitDepth = 16; [recordSettings setObject: [NSNumber numberWithInt:bitDepth] forKey:AVLinearPCMBitDepthKey]; //***** LEAKING 48 BYTES [recordSettings setObject:[NSNumber numberWithBool:YES] forKey:AVLinearPCMIsBigEndianKey]; [recordSettings setObject:[NSNumber numberWithBool: NO]forKey:AVLinearPCMIsFloatKey]; NSError *recorderSetupError = nil; // create the new recorder with target file audioRecorder = [[AVAudioRecorder alloc] initWithURL: destinationURL settings: recordSettings error: &recorderSetupError]; //***** LEAKING 1.31KB [recordSettings release]; recordSettings = nil; // check for erros if (recorderSetupError) { UIAlertView *alert = [[UIAlertView alloc] initWithTitle: @"Can't record" message: [recorderSetupError localizedDescription] delegate: nil cancelButtonTitle: @"OK" otherButtonTitles: nil]; [alert show]; [alert release]; alert = nil; return recorderSetupError; } [audioRecorder prepareToRecord]; //***** LEAKING 512 BYTES audioRecorder.delegate = self; return recorderSetupError; } I do not understand why there is a leak as I release audioRecorder at the start and set to nil and I release recordSettings and set to nil? Can anyone enlighten me please? Thanks

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• Auto-scaffolding Index views in ASP.NET MVC

  - by DanM

  I'm trying to write an auto-scaffolder for Index views. I'd like to be able to pass in a collection of models or view-models (e.g., IQueryable<MyViewModel>) and get back an HTML table that uses the DisplayName attribute for the headings (th elements) and Html.Display(propertyName) for the cells (td elements). Each row should correspond to one item in the collection. Here's what I have so far: <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl" %> <% var items = (IQueryable<TestProj.ViewModels.TestViewModel>)Model; // Should be generic! var properties = items.First().GetMetadata().Properties .Where(pm => pm.ShowForDisplay && !ViewData.TemplateInfo.Visited(pm)); %> <table> <tr> <% foreach(var property in properties) { %> <th> <%= property.DisplayName %> </th> <% } %> </tr> <% foreach(var item in items) { %> <tr> <% foreach(var property in properties) { %> <td> <%= Html.Display(property.DisplayName) %> // This doesn't work! </td> <% } %> </tr> <% } %> </table> Two problems with this: I'd like it to be generic. So, I'd like to replace var items = (IQueryable<TestProj.ViewModels.TestViewModel>)Model; with var items = (IQueryable<T>)Model; or something to that effect. The <td> elements are not working because the Html in <%= Html.Display(property.DisplayName) %> contains the model for the view, which is a collection of items, not the item itself. Somehow, I need to obtain an HtmlHelper object whose Model property is the current item, but I'm not sure how to do that. How do I solve these two problems?

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• How do I add a custom view to iPhone app's UI?

  - by Dr Dork

  I'm diving into iPad development and I'm still learning how everything works together. I understand how to add standard view (i.e. buttons, tableviews, datepicker, etc.) to my UI using both Xcode and Interface Builder, but now I'm trying to add a custom calendar control (TapkuLibrary) to the left window in my UISplitView application. My question is, if I have a custom view (in this case, the TKCalendarMonthView), how do I programmatically add it to one of the views in my UI (in this case, the RootViewController)? Below are some relevant code snippets from my project... RootViewController interface @interface RootViewController : UITableViewController <NSFetchedResultsControllerDelegate> { DetailViewController *detailViewController; NSFetchedResultsController *fetchedResultsController; NSManagedObjectContext *managedObjectContext; } @property (nonatomic, retain) IBOutlet DetailViewController *detailViewController; @property (nonatomic, retain) NSFetchedResultsController *fetchedResultsController; @property (nonatomic, retain) NSManagedObjectContext *managedObjectContext; - (void)insertNewObject:(id)sender; TKCalendarMonthView interface @class TKMonthGridView,TKCalendarDayView; @protocol TKCalendarMonthViewDelegate, TKCalendarMonthViewDataSource; @interface TKCalendarMonthView : UIView { id <TKCalendarMonthViewDelegate> delegate; id <TKCalendarMonthViewDataSource> dataSource; NSDate *currentMonth; NSDate *selectedMonth; NSMutableArray *deck; UIButton *left; NSString *monthYear; UIButton *right; UIImageView *shadow; UIScrollView *scrollView; } @property (readonly,nonatomic) NSString *monthYear; @property (readonly,nonatomic) NSDate *monthDate; @property (assign,nonatomic) id <TKCalendarMonthViewDataSource> dataSource; @property (assign,nonatomic) id <TKCalendarMonthViewDelegate> delegate; - (id) init; - (void) reload; - (void) selectDate:(NSDate *)date; Thanks in advance for all your help! I still have a ton to learn, so I apologize if the question is absurd in any way. I'm going to continue researching this question right now!

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• When using delegates, need better way to do sequential processing

  - by Padawan

  I have a class WebServiceCaller that uses NSURLConnection to make asynchronous calls to a web service. The class provides a delegate property and when the web service call is done, it calls a method webServiceDoneWithXXX on the delegate. There are several web service methods that can be called, two of which are say GetSummary and GetList. The classes that use WebServiceCaller initially need both the summary and list so they are written like this: -(void)getAllData { [webServiceCaller getSummary]; } -(void)webServiceDoneWithGetSummary { [webServiceCaller getList]; } -(void)webServiceDoneWithGetList { ... } This works but there are at least two problems: The calls are split across delegate methods so it's hard to see the sequence at a glance but more important it's hard to control or modify the sequence. Sometimes I want to call just GetSummary and not also GetList so I would then have to use an ugly class-level state variable that tells webServiceDoneWithGetSummary whether to call GetList or not. Assume that GetList cannot be done until GetSummary completes and returns some data which is used as input to GetList. Is there a better way to handle this and still get asynchronous calls? Update based on Matt Long's answer: Using notifications instead of a delegate, it looks like I can solve problem #2 by setting a different selector depending on whether I want the full sequence (GetSummary+GetList) or just GetSummary. Both observers would still use the same notification name when calling GetSummary. I would have to write two separate methods to handle GetSummaryDone instead of using a single delegate method (where I would have needed some class-level variable to tell whether to then call GetList). -(void)getAllData { [[NSNotificationCenter defaultCenter] addObserver:self              selector:@selector(getSummaryDoneAndCallGetList:)                  name:kGetSummaryDidFinish object:nil];     [webServiceCaller getSummary]; } -(void)getSummaryDoneAndCallGetList { [NSNotificationCenter removeObserver] //process summary data [[NSNotificationCenter defaultCenter] addObserver:self              selector:@selector(getListDone:)                  name:kGetListDidFinish object:nil];     [webServiceCaller getList]; } -(void)getListDone { [NSNotificationCenter removeObserver] //process list data } -(void)getJustSummaryData { [[NSNotificationCenter defaultCenter] addObserver:self              selector:@selector(getJustSummaryDone:) //different selector but                  name:kGetSummaryDidFinish object:nil]; //same notification name     [webServiceCaller getSummary]; } -(void)getJustSummaryDone { [NSNotificationCenter removeObserver] //process summary data } I haven't actually tried this yet. It seems better than having state variables and if-then statements but you have to write more methods. I still don't see a solution for problem 1.

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• How to have member variables and public methods in a jQuery plugin?

  - by user169867

  I'm trying to create a jQuery plugin that will create something like an autoCompleteBox but with custom features. How do I store member variables for each matching jQuery element? For example I'll need to store a timerID for each. I'd also like to store references to some of the DOM elements that make up the control. I'd like to be able to make a public method that works something like: $("#myCtrl").autoCompleteEx.addItem("1"); But in the implementation of addItem() how can I access the member variables for that particular object like its timerID or whatever? Below is what I have so far... Thanks for any help or suggestions! (function($) { //Attach this new method to jQuery $.fn.autoCompleteEx = function(options) { //Merge Given Options W/ Defaults, But Don't Alter Either var opts = $.extend({}, $.fn.autoCompleteEx.defaults, options); //Iterate over the current set of matched elements return this.each(function() { var acx = $(this); //Get JQuery Version Of Element (Should Be Div) //Give Div Correct Class & Add <ul> w/ input item to it acx.addClass("autoCompleteEx"); acx.html("<ul><li class=\"input\"><input type=\"text\"/></li></ul>"); //Grab Input As JQ Object var input = $("input", acx); //Wireup Div acx.click(function() { input.focus().val( input.val() ); }); //Wireup Input input.keydown(function(e) { var kc = e.keyCode; if(kc == 13) //Enter { } else if(kc == 27) //Esc { } else { //Resize TextArea To Input var width = 50 + (_txtArea.val().length*10); _txtArea.css("width", width+"px"); } }); }); //End Each JQ Element }; //End autoCompleteEx() //Private Functions function junk() { }; //Public Functions $.fn.autoCompleteEx.addItem = function(id,txt) { var x = this; var y = 0; }; //Default Settings $.fn.autoCompleteEx.defaults = { minChars: 2, delay: 300, maxItems: 1 }; //End Of Closure })(jQuery);

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• Job queue manager with RPC interface

  - by admr

  I need a job queue manager that I can control over the Internet. It should be able to execute and stop processes, check on their status (ideally notice and execute some code when a process exits), respond to commands and also be able to report back to a server. Background: I have a GWT application that allows to create jobs to execute on a cloud instance (currently EC2). I want to push a "job packet" (data for a process to operate on etc) to S3, start a Linux EC2 instance (or use one that's already running), and tell a job manager on the instance to execute that job (possibly parallel to other jobs). It should then pull the "job packet" from S3, run a process that operates on that data and report back to the server that is running the server part of my GWT application with some information (e.g. exit code, stdout, stderr). If I have to write e.g. stdour/err to a file from the process and read that file, that's OK too. I would really like the manager to be "close" to the processes it runs, meaning I want to avoid using something like Runtime.exec from the JDK. It seems like I would have to do that if I used Quartz for example. I'm fine with the calls in both directions being asynchronous. I'm fine with any reasonable technology for the calls as long as I can easily build an interface for that in my GWT server side (e.g. HTTP requests to a servlet over SSL would be nice and trivial). The job manager does not need to have a very sophisticated queueing system. Running several processes either sequentially or in parallel should be fine. Determining how much compute time a process received during its lifetime would be nice (AFAIK, this might be challenging). I did not yet find any existing software that does this, including http://java-source.net/open-source/job-schedulers. I suspect I might have to build an RPC interface (with authentication etc, of course) around a job manager; maybe use something like Apache Commons Exec. In that case, I would prefer Java or Python for the job manager part. I would be happy to hear suggestions for either the former or latter scenario!

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• Managing multiple AJAX calls to PHP scripts

  - by relativelycoded

  I have a set of 5 HTML dropdowns that act as filters for narrowing results returned from a mySQL database. The three pertinent filters are for "Province", "Region", and "City" selection, respectively. I have three functions: findSchools(), which runs when any of the filters (marked with CSS class .filter) are changed, and fetches the results via AJAX from a PHP script. Once that is done, two other functions are called... changeRegionOptions(), which, upon changing the "Province" filter, and updates the available options using the same method as the first function, but posting to a different script. changeCityOptions(), which runs if the "Region" filter was changed, and updates options, again using the same method. The problem is that since I want these AJAX functions to run simultaneously, and they by nature run asynchronously, I've tried using $.when to control the execution of the functions, but it doesn't fix the problem. The functions run, but the Region and City filters return blank (no options); the FireBug report shows absolutely no output, even though the POST request went through. The posted parameter for filter_province gets sent normally, but the one for region gets cut off at the end -- it sends as filter_region=, with no value passed. So I'm presuming my logic is wrong somewhere. The code is below: // When any of the filters are changed, let's query the database... $("select.filter").change(function() { findSchools(); }); // First, we see if there are any results... function findSchools() { var sch_province = document.filterform.filter_province.value; var sch_region = document.filterform.filter_region.value; var sch_city = document.filterform.filter_city.value; var sch_cat = document.filterform.filter_category.value; var sch_type = document.filterform.filter_type.value; $.post("fetch_results.php", { filter_province : sch_province, filter_region : sch_region, filter_city : sch_city, filter_category : sch_cat, filter_type : sch_type }, function(data) { $("#results").html(""); $("#results").hide(); $("#results").html(data); $("#results").fadeIn(600); } ); // Once the results are fetched, we want to see if the filter they changed was the one for Province, and if so, update the Region and City options to match that selection... $("#filter_province").change(function() { $.when(findSchools()) .done(changeRegionOptions()); $.when(changeRegionOptions()) .done(changeCityOptions()); }); }; This is just one of the ways I've tried to solve it; I've tried using an IF statement, and tried calling the functions directly inside the general select.filter.change() function (after findSchools(); ), but they all return the same result. Any help with this would be great!

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• Accidental Complexity in OpenSSL HMAC functions

  - by Hassan Syed

  SSL Documentation Analaysis This question is pertaining the usage of the HMAC routines in OpenSSL. Since Openssl documentation is a tad on the weak side in certain areas, profiling has revealed that using the: unsigned char *HMAC(const EVP_MD *evp_md, const void *key, int key_len, const unsigned char *d, int n, unsigned char *md, unsigned int *md_len); From here, shows 40% of my library runtime is devoted to creating and taking down **HMAC_CTX's behind the scenes. There are also two additional function to create and destroy a HMAC_CTX explicetly: HMAC_CTX_init() initialises a HMAC_CTX before first use. It must be called. HMAC_CTX_cleanup() erases the key and other data from the HMAC_CTX and releases any associated resources. It must be called when an HMAC_CTX is no longer required. These two function calls are prefixed with: The following functions may be used if the message is not completely stored in memory My data fits entirely in memory, so I choose the HMAC function -- the one whose signature is shown above. The context, as described by the man page, is made use of by using the following two functions: HMAC_Update() can be called repeatedly with chunks of the message to be authenticated (len bytes at data). HMAC_Final() places the message authentication code in md, which must have space for the hash function output. The Scope of the Application My application generates a authentic (HMAC, which is also used a nonce), CBC-BF encrypted protocol buffer string. The code will be interfaced with various web-servers and frameworks Windows / Linux as OS, nginx, Apache and IIS as webservers and Python / .NET and C++ web-server filters. The description above should clarify that the library needs to be thread safe, and potentially have resumeable processing state -- i.e., lightweight threads sharing a OS thread (which might leave thread local memory out of the picture). The Question How do I get rid of the 40% overhead on each invocation in a (1) thread-safe / (2) resume-able state way ? (2) is optional since I have all of the source-data present in one go, and can make sure a digest is created in place without relinquishing control of the thread mid-digest-creation. So, (1) can probably be done using thread local memory -- but how do I resuse the CTX's ? does the HMAC_final() call make the CTX reusable ?. (2) optional: in this case I would have to create a pool of CTX's. (3) how does the HMAC function do this ? does it create a CTX in the scope of the function call and destroy it ? Psuedocode and commentary will be useful.

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• Error in facebook.dll facebooksdk

  - by Surendar Radhakrishnan

  I got the web application working with facebooksdk and when i deployed it...it is running fine for sometime and it is throwing the error like this... Server Error in '/' Application. Could not load file or assembly 'Facebook, Version=4.1.1.0, Culture=neutral, PublicKeyToken=58cb4f2111d1e6de' or one of its dependencies. Access is denied. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.IO.FileLoadException: Could not load file or assembly 'Facebook, Version=4.1.1.0, Culture=neutral, PublicKeyToken=58cb4f2111d1e6de' or one of its dependencies. Access is denied. Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Assembly Load Trace: The following information can be helpful to determine why the assembly 'Facebook, Version=4.1.1.0, Culture=neutral, PublicKeyToken=58cb4f2111d1e6de' could not be loaded. WRN: Assembly binding logging is turned OFF. To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1. Note: There is some performance penalty associated with assembly bind failure logging. To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog]. Stack Trace: [FileLoadException: Could not load file or assembly 'Facebook, Version=4.1.1.0, Culture=neutral, PublicKeyToken=58cb4f2111d1e6de' or one of its dependencies. Access is denied.] Secured_Login.FacebookVerification() +0 System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +25 System.Web.UI.Control.LoadRecursive() +71 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3048 Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.1 i got this method in pageload protected void Page_Load(object sender, EventArgs e) { FacebookVerification(); } protected void FacebookVerification() { try { FacebookApp fbApp = new FacebookApp(); if (fbApp.Session != null) { dynamic myinfo = fbApp.Get("me"); String firstname = myinfo.first_name; String lastname = myinfo.last_name; lblFBStatus.Text = "you signed in as " + firstname + " " + lastname ; } else { lblFBStatus.Text = "Please sign in with facebook"; } } catch (Exception) { throw; } }

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• Would someone mind giving suggestions for this new assembly language?

  - by Noctis Skytower

  Greetings! Last semester in college, my teacher in the Computer Languages class taught us the esoteric language named Whitespace. In the interest of learning the language better with a very busy schedule (midterms), I wrote an interpreter and assembler in Python. An assembly language was designed to facilitate writing programs easily, and a sample program was written with the given assembly mnemonics. Now that it is summer, a new project has begun with the objective being to rewrite the interpreter and assembler for Whitespace 0.3, with further developments coming afterwards. Since there is so much extra time than before to work on its design, you are presented here with an outline that provides a revised set of mnemonics for the assembly language. This post is marked as a wiki for their discussion. Have you ever had any experience with assembly languages in the past? Were there some instructions that you thought should have been renamed to something different? Did you find yourself thinking outside the box and with a different paradigm than in which the mnemonics were named? If you can answer yes to any of those questions, you are most welcome here. Subjective answers are appreciated! hold N Push the number onto the stack copy Duplicate the top item on the stack copy N Copy the nth item on the stack (given by the argument) onto the top of the stack swap Swap the top two items on the stack drop Discard the top item on the stack drop N Slide n items off the stack, keeping the top item add Addition sub Subtraction mul Multiplication div Integer Division mod Modulo save Store load Retrieve L: Mark a location in the program call L Call a subroutine goto L Jump unconditionally to a label if=0 L Jump to a label if the top of the stack is zero if<0 L Jump to a label if the top of the stack is negative return End a subroutine and transfer control back to the caller exit End the program print chr Output the character at the top of the stack print int Output the number at the top of the stack input chr Read a character and place it in the location given by the top of the stack input int Read a number and place it in the location given by the top of the stack Question: How would you redesign, rewrite, or rename the previous mnemonics and for what reasons?

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• Hard crash when drawing content for CALayer using quartz

  - by Lukasz

  I am trying to figure out why iOS crash my application in the harsh way (no crash logs, immediate shudown with black screen of death with spinner shown for a while). It happens when I render content for CALayer using Quartz. I suspected the memory issue (happens only when testing on the device), but memory logs, as well as instruments allocation logs looks quite OK. Let me past in the fatal function: - (void)renderTiles{ if (rendering) { //NSLog(@"====== RENDERING TILES SKIP ======="); return; } rendering = YES; CGRect b = tileLayer.bounds; CGSize s = b.size; CGFloat imageScale = [[UIScreen mainScreen] scale]; s.height *= imageScale; s.width *= imageScale; dispatch_async(queue, ^{ NSLog(@""); NSLog(@"====== RENDERING TILES START ======="); NSLog(@"1. Before creating context"); report_memory(); CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); NSLog(@"2. After creating color space"); report_memory(); NSLog(@"3. About to create context with size: %@", NSStringFromCGSize(s)); CGContextRef ctx = CGBitmapContextCreate(NULL, s.width, s.height, 8, 0, colorSpace, kCGImageAlphaPremultipliedLast); NSLog(@"4. After creating context"); report_memory(); CGAffineTransform flipTransform = CGAffineTransformMake(1.0, 0.0, 0.0, -1.0, 0.0, s.height); CGContextConcatCTM(ctx, flipTransform); CGRect tileRect = CGRectMake(0, 0, tileImageScaledSize.width, tileImageScaledSize.height); CGContextDrawTiledImage(ctx, tileRect, tileCGImageScaled); NSLog(@"5. Before creating cgimage from context"); report_memory(); CGImageRef cgImage = CGBitmapContextCreateImage(ctx); NSLog(@"6. After creating cgimage from context"); report_memory(); dispatch_sync(dispatch_get_main_queue(), ^{ tileLayer.contents = (id)cgImage; }); NSLog(@"7. After asgning tile layer contents = cgimage"); report_memory(); CGColorSpaceRelease(colorSpace); CGContextRelease(ctx); CGImageRelease(cgImage); NSLog(@"8. After releasing image and context context"); report_memory(); NSLog(@"====== RENDERING TILES END ======="); NSLog(@""); rendering = NO; }); } Here are the logs: ====== RENDERING TILES START ======= 1. Before creating context Memory in use (in bytes): 28340224 / 519442432 (5.5%) 2. After creating color space Memory in use (in bytes): 28340224 / 519442432 (5.5%) 3. About to create context with size: {6324, 5208} 4. After creating context Memory in use (in bytes): 28344320 / 651268096 (4.4%) 5. Before creating cgimage from context Memory in use (in bytes): 153649152 / 651333632 (23.6%) 6. After creating cgimage from context Memory in use (in bytes): 153649152 / 783159296 (19.6%) 7. After asgning tile layer contents = cgimage Memory in use (in bytes): 153653248 / 783253504 (19.6%) 8. After releasing image and context context Memory in use (in bytes): 21688320 / 651288576 (3.3%) ====== RENDERING TILES END ======= Application crashes in random places. Sometimes when reaching en of the function and sometime in random step. Which direction should I look for a solution? Is is possible that GDC is causing the problem? Or maybe the context size or some Core Animation underlying references?

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• Blackberry - application settings save/load

  - by Max Gontar

  Hi! I know two ways to save/load application settings: use PersistentStore use filesystem (store, since SDCard is optional) I'd like to know what are you're practicies of working with application settings? Using PersistentStore to save/load application settings The persistent store provides a means for objects to persist across device resets. A persistent object consists of a key-value pair. When a persistent object is committed to the persistent store, that object's value is stored in flash memory via a deep copy. The value can then be retrieved at a later point in time via the key. Example of helper class for storing and retrieving settings: class PSOptions { private PersistentObject mStore; private LongHashtableCollection mSettings; private long KEY_URL = 0; private long KEY_ENCRYPT = 1; private long KEY_REFRESH_PERIOD = 2; public PSOptions() { // "AppSettings" = 0x71f1f00b95850cfeL mStore = PersistentStore.getPersistentObject(0x71f1f00b95850cfeL); } public String getUrl() { Object result = get(KEY_URL); return (null != result) ? (String) result : null; } public void setUrl(String url) { set(KEY_URL, url); } public boolean getEncrypt() { Object result = get(KEY_ENCRYPT); return (null != result) ? ((Boolean) result).booleanValue() : false; } public void setEncrypt(boolean encrypt) { set(KEY_ENCRYPT, new Boolean(encrypt)); } public int getRefreshPeriod() { Object result = get(KEY_REFRESH_PERIOD); return (null != result) ? ((Integer) result).intValue() : -1; } public void setRefreshRate(int refreshRate) { set(KEY_REFRESH_PERIOD, new Integer(refreshRate)); } private void set(long key, Object value) { synchronized (mStore) { mSettings = (LongHashtableCollection) mStore.getContents(); if (null == mSettings) { mSettings = new LongHashtableCollection(); } mSettings.put(key, value); mStore.setContents(mSettings); mStore.commit(); } } private Object get(long key) { synchronized (mStore) { mSettings = (LongHashtableCollection) mStore.getContents(); if (null != mSettings && mSettings.size() != 0) { return mSettings.get(key); } else { return null; } } } } Example of use: class Scr extends MainScreen implements FieldChangeListener { PSOptions mOptions = new PSOptions(); BasicEditField mUrl = new BasicEditField("Url:", "http://stackoverflow.com/"); CheckboxField mEncrypt = new CheckboxField("Enable encrypt", false); GaugeField mRefresh = new GaugeField("Refresh period", 1, 60 * 10, 10, GaugeField.EDITABLE|FOCUSABLE); ButtonField mLoad = new ButtonField("Load settings", ButtonField.CONSUME_CLICK); ButtonField mSave = new ButtonField("Save settings", ButtonField.CONSUME_CLICK); public Scr() { add(mUrl); mUrl.setChangeListener(this); add(mEncrypt); mEncrypt.setChangeListener(this); add(mRefresh); mRefresh.setChangeListener(this); HorizontalFieldManager hfm = new HorizontalFieldManager(USE_ALL_WIDTH); add(hfm); hfm.add(mLoad); mLoad.setChangeListener(this); hfm.add(mSave); mSave.setChangeListener(this); loadSettings(); } public void fieldChanged(Field field, int context) { if (field == mLoad) { loadSettings(); } else if (field == mSave) { saveSettings(); } } private void saveSettings() { mOptions.setUrl(mUrl.getText()); mOptions.setEncrypt(mEncrypt.getChecked()); mOptions.setRefreshRate(mRefresh.getValue()); } private void loadSettings() { mUrl.setText(mOptions.getUrl()); mEncrypt.setChecked(mOptions.getEncrypt()); mRefresh.setValue(mOptions.getRefreshPeriod()); } }

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• Function-Local Static Const variable Initialization semantics.

  - by Hassan Syed

  The questions are in bold, for those that cannot be bothered reading a question in depth. This is a followup to this question. It is to do with the initialization semantics of static variables in functions. Static variables should be initialized once, and their internal state might be altered later - as I (currently) do in the linked question. However, the code in question does not require the feature to change the state of the variable later. Let me clarrify my position, since I don't require the string object's internal state to change. The code is for a trait class for meta programming, and as such would would benifit from a const char * const ptr -- thus Ideally a local cost static const variable is needed. My educated guess is that in this case the string in question will be optimally placed in memory by the link-loader, and that the code is more secure and maps to the intended semantics. This leads to the semantics of such a variable "The C++ Programming language Third Edition -- Stroustrup" does not have anything (that I could find) to say about this matter. All that is said is that the variable is initialized once when the flow of control of the thread first reaches the code. This leads me to ponder if the following code would be sensible, and if not what are the intended semantics ?. #include <iostream> const char * const GetString(const char * x_in) { static const char * const x = x_in; return x; } int main() { const char * const temp = GetString("yahoo"); std::cout << temp << std::endl; const char * const temp2 = GetString("yahoo2"); std::cout << temp2 << std::endl; } The following compiles on GCC and prints "yahoo" twice. Which is what I want -- However it might not be standards compliant (which is why I post this question). It might be more elegant to have two functions, "SetString" and "String" where the latter forwards to the first. If it is standards compliant does someone know of a templates implementation in boost (or elsewhere) ?

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• Why is cell phone software still so primitive?

  - by Tomislav Nakic-Alfirevic

  I don't do mobile development, but it strikes me as odd that features like this aren't available by default on most phones: full text search: searches all address book contents, messages, anything else being a plus better call management: e.g. a rotating audio call log, meaning you always have the last N calls recorded for your listening pleasure later (your little girl just said her first "da-da" while you were on a business trip, you had a telephone job interview, you received complex instructions to do something etc.) bluetooth remote control (like e.g. anyRemote, but available by default on a bluetooth phone) no multitasking capabilities worth mentioning and in general no e.g. weekly software updates, making the phone much more usable (even if it had to be done over USB, rather than over the network). I'm sure I was dumbfounded by the lack or design of other features as well, but they don't come to mind right now. To clarify, I'm not talking about smartphones here: my plain, 2-year old phone has a CPU an order of magnitude faster than my first PC, about as much storage space and it's ridiculous how bad (slow, unwieldy) the software is and it's not one phone or one manufacturer. What keeps the (to me) obvious software functionality vacuum on a capable hardware platform from being filled up? Edit: I believe a clarification on the multitasking point might be beneficial. I'll use my phone as an example, although the point is much more general. The phone can multitask and in fact does: you can listen to music and do something else at the same time. On the other hand, the way the software has been designed makes multitasking next to useless. (Ditto with the external touch screen: it can take touch commands, but only one application makes use of it, and only with 3 commands.) To take the multitasking example to the extreme, if I plug my phone into my laptop and it registers as an external disk, it doesn't allow any kind of operation: messages, calling, calendar, everything out of reach, although I can receive a call. No "battery life" issue there: it's charging while connected. BTW, another example of design below the current state of the art: I don't see a phone on the horizon which will remember where in an audio or video file you were when you stopped listening/watching it last time (podcasts are a good use case). Simplistic rewind/fast forward functionality only aggravates the problem.

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• How to designing a generic databse whos layout may change over time?

  - by mawg

  Here's a tricky one - how do I programatically create and interrogate a database who's contents I can't really foresee? I am implementing a generic input form system. The user can create PHP forms with a WYSIWYG layout and use them for any purpose he wishes. He can also query the input. So, we have three stages: a form is designed and generated. This is a one-off procedure, although the form can be edited later. This designs the database. someone or several people make use of the form - say for daily sales reports, stock keeping, payroll, etc. Their input to the forms is written to the database. others, maybe management, can query the database and generate reports. Since these forms are generic, I can't predict the database structure - other than to say that it will reflect HTML form fields and consist of a the data input from collection of edit boxes, memos, radio buttons and the like. Questions and remarks: A) how can I best structure the database, in terms of tables and columns? What about primary keys? My first thought was to use the control name to identify each column, then I realized that the user can edit the form and rename, so that maybe "name" becomes "employee" or "wages" becomes ":salary". I am leaning towards a unique number for each. B) how best to key the rows? I was thinking of a timestamp to allow me to query and a column for the row Id from A) C) I have to handle column rename/insert/delete. Foe deletion, I am unsure whether to delete the data from the database. Even if the user is not inputting it from the form any more he may wish to query what was previously entered. Or there may be some legal requirements to retain the data. Any gotchas in column rename/insert/delete? D) For the querying, I can have my PHP interrogate the database to get column names and generate a form with a list where each entry has a database column name, a checkbox to say if it should be used in the query and, based on column type, some selection criteria. That ought to be enough to build searches like "position = 'senior salesman' and salary 50k". E) I probably have to generate some fancy charts - graphs, histograms, pie charts, etc for query results of numerical data over time. I need to find some good FOSS PHP for this. F) What else have I forgotten? This all seems very tricky to me, but I am database n00b - maybe it is simple to you gurus?

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• Share a "deep link" from a Windows 8/WinRT application

  - by Dave Parker

  I have searched using many different terms and phrases, and waded through many pages of results, but I have (remarkably) not seen anyone else addressing, even asking, about, this issue. So here goes... Ultimate Goal: Allow a user viewing a content-based page (may contain both text and images) within a Windows Store app to share that content with someone else. Description I am working on taking a fair amount of content and making it available for browsing/navigating as a Windows 8/WinRT/Windows Store (we need a consistent name here) application. One of the desired features is to take advantage of the Share Charm, such that someone viewing a page could share that page with someone else. The ideal behavior is for the application to implement the Share Source contract which would share an email message that contained some explanatory text, a link to get the app from the Windows Store, and a "deep link" into the shared page in the application. Solutions Considered We had originally looked at just generating a PDF representation of the page, but there are very few external libraries that would work under WinRT, and having to include externally licensed code would be problematic as well. Writing our own PDF generation code would out of scope. We have also considered generating a Word document or PowerPoint slide using OpenXML, but again, we run up against the limitaions of WinRT. In this case, it is highly unlikely the OpenXML SDK is useable in a WinRT application. Another thought was to pre-generate all of the pages as .pdf files, store them as resources, and when the Share Charm is invoked, share the .pdf file associated with the current page. The problem here is the application will have at least 150 content pages, and depending on how we break the content down, up to over 600. This would likely cause serious bloat. Where We Are At Thus we have come to sharing URIs. From what I can tell, though, the "deep linking" feature is only intended for use on Secondary Tiles tied to your application. Another avenue I considered was registering a protocol like, "my-special-app:" with the OS and having it fire up the application but that would require HKCR registry access, which is outside the WinRT sandbox. If it matters, we are leaning towards an HTML/JS application, rather than XAML/C#, because the converted content will all be in HTML and the WebView control in WinRT is fairly limited. This decision is not yet final, though. Conclusion So, is this possible, and if so, how would it be done or where can I find documentation on it? Thanks, Dave Parker

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• Cocoa NSOutputStream send to a connection

  - by Chuck

  Hi, I am new to Cocoa, but managed to get a connection (to a FTP) up and running, and I've set up an eventhandler for the NSInputStream iStream to alert every response (which also works). What I manage to get is simply the hello message and a connection timeout 60 sec, closing control connection. After searching stackoverflow and finding a lot of NSOutputStream write problems (e.g. http://stackoverflow.com/questions/703729/how-to-use-nsoutputstreams-write-message) and a lot of confusion in my google hits, I figured I'd try to ask my own question: I've tried reading the developer.apple.com doc on OutputStream, but it seems almost impossible for me to send some data (in this case just a string) to the "connection" via the NSOutputStream oStream. - (IBAction) send_something: sender { const char *send_command_char = [@"USER foo" UTF8String]; send_command_buffer = [NSMutableData dataWithBytes:send_command_char length:strlen(send_command_char) + 1]; uint8_t *readBytes = (uint8_t *)[send_command_buffer mutableBytes]; NSInteger byteIndex = 0; readBytes += byteIndex; int data_len = [send_command_buffer length]; unsigned int len = ((data_len - byteIndex >= 1024) ? 1024 : (data_len-byteIndex)); uint8_t buf[len]; (void)memcpy(buf, readBytes, len); len = [oStream write:(const uint8_t *)buf maxLength:len]; byteIndex += len; } the above seems not to result in any useable events. typing it under NSStreamEventHasSpaceAvailable sometimes give a response if I spam the ftp by keep creating new connection instances and keep sending some command whenever oStream has free space. In other words, nothing "right" and so I'm still unclear how to properly send a command to the connection. Should I open - write - close every time i want to write to oStream (and thus to the ftp) and can I then expect a reply (hasBytesAvailable event on iStream)? For some reason I find it very difficult to find any clear tutorials on this matter. Seems like there are more than a few in the same position as me: unclear how to use oStream write? Any little bit that can help clear this up is greatly appreciated! If needed I can write the rest of the code. Chuck

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• Lazy loading the addthis script? (or lazy loading external js content dependent on already fired eve

  - by Keith Bentrup

  I want to have the addthis widget available for my users, but I want to lazy load it so that my page loads as quickly as possible. However, after trying it via a script tag and then via my lazy loading method, it appears to only work via the script tag. In the obfuscated code, I see something that looks like it's dependent on the DOMContentLoaded event (at least for firefox). Since the DOMContentLoaded event has already fired, the widget doesn't render properly. What to do? I could just use a script tag (slower)... or could I fire (in a cross browser way) the DOMContentLoaded (or equivalent) event? I have a feeling this may not be possible b/c I believe that (like jQuery) there are multiple tests of the content ready event, and so multiple simulated events would have to occur. Nonetheless, this is an interesting problem b/c I have seen a couple widgets now assume that you are including their stuff via static script tags. It would be nice if they wrote code that was more useful to developers concerned about speed, but until then, is there a work around?? And/or are any of my assumptions wrong? Edit: Because the 1st answer to the question seemed to miss the point of my problem, I wanted to clarify the situation. This is about a specific problem. I'm not looking for yet another lazy load script or check if some dependencies are loaded script. Specifically this problem deals with external widgets that you do not have control over and may or may not be obfuscated delaying the load of the external widgets until they are needed or at least, til substantially after everything else has been loaded including other deferred elements b/c of the how the widget was written, precludes existing, typical lazy loading paradigms While it's esoteric, I have seen it happen with a couple widgets - where the widget developers assume that you're just willing to throw in another script tag at the bottom of the page. I'm looking to save those 500-1000 ms** though as numerous studies by yahoo, google, and amazon show it to be important to your user's experience. **My testing with hammerhead and personal experience indicates that this will be my savings in this case.

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• How to display part of an image for the specific width and height?

  - by Brady Chu

  Recently I participated in a web project which has a huge large of images to handle and display on web page, we know that the width and height of images end users uploaded cannot be control easily and then they are hard to display. At first, I attempted to zoom in/out the images to rearch an appropriate presentation, and I made it, but my boss is still not satisfied with my solution, the following is my way: var autoResizeImage = function(maxWidth, maxHeight, objImg) { var img = new Image(); img.src = objImg.src; img.onload = function() { var hRatio; var wRatio; var Ratio = 1; var w = img.width; var h = img.height; wRatio = maxWidth / w; hRatio = maxHeight / h; if (maxWidth == 0 && maxHeight == 0) { Ratio = 1; } else if (maxWidth == 0) { if (hRatio < 1) { Ratio = hRatio; } } else if (maxHeight == 0) { if (wRatio < 1) { Ratio = wRatio; } } else if (wRatio < 1 || hRatio < 1) { Ratio = (wRatio <= hRatio ? wRatio : hRatio); } if (Ratio < 1) { w = w * Ratio; h = h * Ratio; } w = w <= 0 ? 250 : w; h = h <= 0 ? 370 : h; objImg.height = h; objImg.width = w; }; }; This way is only intended to limit the max width and height for the image so that every image in album still has different width and height which are still very urgly. And right at this minute, I know we can create a DIV and use the image as its background image, this way is too complicated and not direct I don't want to take. So I's wondering whether there is a better way to display images with the fixed width and height without presentation distortion? Thanks.

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• average velocity, as3

  - by VideoDnd

  Hello, I need something accurate I can plug equations in to if you can help. How would you apply the equation bellow? Thanks guys. AVERAGE VELOCITY AND DISPLACEMENT average velocity V=X/T displacement x=v*T more info example I have 30 seconds and a field that is 170 yards. What average velocity would I need my horse to travel at to reach the end of the field in 30 seconds. I moved the decimal places around and got this. Here's what I tried 'the return value is close, but not close enough' FLA here var TIMER:int = 10; var T:int = 0; var V:int = 5.6; var X:int = 0; var Xf:int = 17000/10*2; var timer:Timer = new Timer(TIMER,Xf); timer.addEventListener(TimerEvent.TIMER, incrementCounter); timer.start(); function formatCount(i:int):String { var fraction:int = Math.abs(i % 100); var whole:int = Math.abs(i / 100); return ("0000000" + whole).substr(-7, 7) + "." + (fraction < 10 ? "0" + fraction : fraction); } function incrementCounter(event:TimerEvent) { T++; X = Math.abs(V*T); text.text = formatCount(X); } tests TARGET 5.6yards * 30seconds = 168yards INTEGERS 135.00 in 30 seconds MATH.ROUND 135.00 in 30 seconds NUMBERS 140.00 in 30 seconds control timer 'I tested with this and the clock on my desk' var timetest:Timer = new Timer(1000,30); var Dplus:int = 17000; timetest.addEventListener(TimerEvent.TIMER, cow); timetest.start(); function cow(evt:TimerEvent):void { tx.text = String("30 SECONDS: " + timetest.currentCount); if(timetest.currentCount> Dplus){ timetest.stop(); } } //far as I got...couldn't get delta to work... T = (V*timer.currentCount); X += Math.round(T);

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• Visual Studio soft-crashing when encountering XAML Errors in initialize.

  - by Aren

  I've been having some serious issues with Visual Studio 2010 as of late. It's been crashing in a peculiar way when I encounter certain types of XAML errors during the InitializeComponent() of a control/window. The program breaks and visual studio gears up like it's catching an exception (because it is) and then stops midway displaying a broken highlight in my XAML file with no details as to what is wrong. Example: There is not pop outs, or details Anywhere about what is wrong, only a callstack that points to my InitializeComponent() call. Now normally I'd just do some trial and error to fix this problem, and find out where i messed up, but the real problem isn't my code. Visual Studio is rendered completely useless at this point. It reports my application still in "Running" mode. The Stop/Break/Restart buttons on the toolbar or in the menus don't do anything (but grey out). Closing the application does not stop this behaviour, closing visual studio gets it stuck in a massive loop where it yells at me complaining every file open is not in the debug project, then repeats this process when i have exausted every open file. I have to force-close devenv.exe, and after this happening 3-4 times in a row it's a lot of wasted time (as my projects are usually pretty big and studio can be quite slow @ loading). To the point Has anyone else experienced this? How can I stop studio from locking up. Can I at LEAST get information out of this beast another way so i can fix my XAML error sooner rather than after 3-4 trial-and-error compiles yielding the same crash? Any & All help would be appreciated. Visual Studio 2010 version: 10.0.30319.1RTM Edit & Update FWIW, mostly the errors that cause this are XamlParseExceptions (I figured this out after i found what was wrong with my XAML). I think I need to be clearer though, Im not looking for the solution to my code problem, as these are usually typos / small things, I'm looking for a solution to VStudio getting all buggered up as a result. The particular error in the above image that 100% for sure caused this was a XamlParseException caused by forgetting a Value attribute on a data trigger. I've fixed that part but it still doesn't tell my why my studio becomes a lump of neutered program when a perfectly normal exception is thrown in the parsing of the XAML. Code that will cause this issue (at least for me) This is the base template WPF Application, with the following Window.xaml code. The problem is a missing Value="True" on the <DataTrigger ...> in the template. It generates a XamlParseException and Visual Studio Crashes as described above when debugging it. Final Notes The following solutions did not help me: Restarting Visual Studio Rebooting Reinstalling Visual Studio

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• CSS precedence order? My lecture slides are correct or not?

  - by Michael Mao

  Hi all: I've noticed that there are a couple of similar questions and answers at SO already, but let me clarify my specific question here first: I've got lecture slides which states like this: To be frank, I haven't heard of this rule of css precedence myself, and I googled to find something with similar topic but not quite like that : here To have a test myself, I've made a test page on my own server here After running it on FireFox 3.6.3, I am sure it does not show the way as it should be, according to the statement in lecture slides: imported stylesheet ? am I doing it wrong? I cannot see its effect using FireBug it says that embedded stylesheet has a higher precedence over linked/imported stylesheets, however, it doesn't work, if I put the linked/imported tag AFTER that. inline style vs html attributes ? I've got an image where I firstly set its inline style to control the width and height, then use direct html attributes width/height to try modifying that, but failed... Below is the source code : <html> <head> <style type="text/css"> #target { border : 2px solid green; color : green; } </style> <link rel="stylesheet" href="./linked.css" type="text/css" media="screen" /> </head> <body> <div id="target">A targeted div tag on page.</div> <img src="cat.jpg" alt="" style="width : 102px; height : 110px;" width="204px" height="220px" /> </body> </html> Can any experienced CSS guys help me figure out if the slide is correct or not? Frankly speaking, I am puzzled myself, as I can clearly see some other "incorrect" statements here and there amongst the slides, such as JavaScript is on client-side (how about server-side JavaScript?) and "Embedded styles are in the head section of a web page "(what the heck? I am not allowed to put it inside the body tag?) Sorry about this silly question, the exam is on TOMORROW, and I now see a lot of things to think about :)

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• Can parser combination be made efficient?

  - by Jon Harrop

  Around 6 years ago, I benchmarked my own parser combinators in OCaml and found that they were ~5× slower than the parser generators on offer at the time. I recently revisited this subject and benchmarked Haskell's Parsec vs a simple hand-rolled precedence climbing parser written in F# and was surprised to find the F# to be 25× faster than the Haskell. Here's the Haskell code I used to read a large mathematical expression from file, parse and evaluate it: import Control.Applicative import Text.Parsec hiding ((<|>)) expr = chainl1 term ((+) <$ char '+' <|> (-) <$ char '-') term = chainl1 fact ((*) <$ char '*' <|> div <$ char '/') fact = read <$> many1 digit <|> char '(' *> expr <* char ')' eval :: String -> Int eval = either (error . show) id . parse expr "" . filter (/= ' ') main :: IO () main = do file <- readFile "expr" putStr $ show $ eval file putStr "\n" and here's my self-contained precedence climbing parser in F#: let rec (|Expr|) (P(f, xs)) = Expr(loop (' ', f, xs)) and shift oop f op (P(g, xs)) = let h, xs = loop (op, g, xs) loop (oop, f h, xs) and loop = function | ' ' as oop, f, ('+' | '-' as op)::P(g, xs) | (' ' | '+' | '-' as oop), f, ('*' | '/' as op)::P(g, xs) | oop, f, ('^' as op)::P(g, xs) -> let h, xs = loop (op, g, xs) let op = match op with | '+' -> (+) | '-' -> (-) | '*' -> (*) | '/' -> (/) | '^' -> pown loop (oop, op f h, xs) | _, f, xs -> f, xs and (|P|) = function | '-'::P(f, xs) -> let f, xs = loop ('~', f, xs) P(-f, xs) | '('::Expr(f, ')'::xs) -> P(f, xs) | c::xs when '0' <= c && c <= '9' -> P(int(string c), xs) My impression is that even state-of-the-art parser combinators waste a lot of time back tracking. Is that correct? If so, is it possible to write parser combinators that generate state machines to obtain competitive performance or is it necessary to use code generation?

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