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• PDF Report generation

  - by IniTech

  EDIT : I completed this project using ABCpdf. For anyone interested, I love this product and their support is A+. Everything I listed as a 'Con' for the HTML - PDF solution was easily doable in ABCpdf. I've been charged with creating a data driven pdf report. After reviewing the plethora of options, I have narrowed it down to 2. I need you all to to help me decide, or offer alternatives I haven't considered. Here are the requirements: 100% Data driven Eventually PDF (a stop in HTML is fine, so long as it is converted) Can be run with multiple sets of data (the layout is always the same, the data is variable) Contains normal analysis-style copy (saved in DB with html markup) Contains tables (data for tables is generated at run-time) Header/Page # on each page Table of Contents .NET (VB or C#) Done quickly Now, because of the fact that the report is going to be generated with multiple sets of data, I don't think a stamped pdf template will work since I won't know how long or how many pages a certain piece of the report could require. So, I think my best options are: Programmatic creation using an iText-like solution. Generate in HTML and convert to PDF using a third-party application (ABCPdf is the tool I have played with so far) Both solutions have their pro's and con's. Programmatic solution: Pros: Flexible Easy page numbering/page header/table of contents Free Cons: Time consuming (to write a layer on top of iText to do what I need and keep maintainable) Since the copy is already stored in the db with html markup, I would have to parse through the data before I place it into the pdf, ensuring I don't have to break the paragraph into chunks so I can apply bold, italic, underline, etc. to specific phrases. This seems like a huge PITA, and I hope I am wrong about that assumption. HTML - PDF Pros: Easy to generate from db (no parsing necessary) Many tools for conversion Uses technology I am already familiar with Built-in "Print Preview" - not a req, but nice Cons: (Edited after project completion. All of my assumptions were incorrect and ABCpdf is awesome) 1. Almost impossible to generate page headers - Not True 2. Very difficult to generate page numbers Not True 3. Nearly impossible to generate table of contents Not True 4. (Cross-browser support isn't a con; Since its internal, I can dictate what browser to use) 5. Conversion tool quirks - may not convert exactly as rendered in browser Not True 6. Overall, I think it would be very hard to format the HTML exactly as I would want it to appear/convert to PDF. Not True That's it - I need the communitys help in deciding which way I should go. I might be wrong about some of my Pro/Con assumptions. If I am, please tell me. All thoughts and suggestions are welcome and appreciated. Thanks

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• Memory allocation and release for UIImage in iPhone?

  - by rkbang

  Hello all, I am using following code in iPhone to get smaller cropped image as follows: - (UIImage*) getSmallImage:(UIImage*) img { CGSize size = img.size; CGFloat ratio = 0; if (size.width < size.height) { ratio = 36 / size.width; } else { ratio = 36 / size.height; } CGRect rect = CGRectMake(0.0, 0.0, ratio * size.width, ratio * size.height); UIGraphicsBeginImageContext(rect.size); [img drawInRect:rect]; UIImage *tempImg = [UIGraphicsGetImageFromCurrentImageContext() retain]; UIGraphicsEndImageContext(); return [tempImg autorelease]; } - (UIImage*)imageByCropping:(UIImage *)imageToCrop toRect:(CGRect)rect { //create a context to do our clipping in UIGraphicsBeginImageContext(rect.size); CGContextRef currentContext = UIGraphicsGetCurrentContext(); //create a rect with the size we want to crop the image to //the X and Y here are zero so we start at the beginning of our //newly created context CGFloat X = (imageToCrop.size.width - rect.size.width)/2; CGFloat Y = (imageToCrop.size.height - rect.size.height)/2; CGRect clippedRect = CGRectMake(X, Y, rect.size.width, rect.size.height); //CGContextClipToRect( currentContext, clippedRect); //create a rect equivalent to the full size of the image //offset the rect by the X and Y we want to start the crop //from in order to cut off anything before them CGRect drawRect = CGRectMake(0, 0, imageToCrop.size.width, imageToCrop.size.height); CGContextTranslateCTM(currentContext, 0.0, drawRect.size.height); CGContextScaleCTM(currentContext, 1.0, -1.0); //draw the image to our clipped context using our offset rect //CGContextDrawImage(currentContext, drawRect, imageToCrop.CGImage); CGImageRef tmp = CGImageCreateWithImageInRect(imageToCrop.CGImage, clippedRect); //pull the image from our cropped context UIImage *cropped = [UIImage imageWithCGImage:tmp];//UIGraphicsGetImageFromCurrentImageContext(); CGImageRelease(tmp); //pop the context to get back to the default UIGraphicsEndImageContext(); //Note: this is autoreleased*/ return cropped; } I am using following line of code in cellForRowAtIndexPath to update the image of the cell: cell.img.image = [self imageByCropping:[self getSmallImage:[UIImage imageNamed:@"goal_image.png"]] toRect:CGRectMake(0, 0, 36, 36)]; Now when I add this table view and pop it from navigation controller, I see a memory hike.I see no leaks but memory keeps climbing. Please note that the images changes for each row and I am creating the controller using lazy initialization that is I create or alloc it whenever I need it. I saw on internet many people facing the same issue, but very rare good solutions. I have multiple views using the same way and I see almost memory raised to 4MB within 20-25 view transitions. What is the good solution to resolve this issue. tnx.

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• Estimating the boundary of arbitrarily distributed data

  - by Dave

  I have two dimensional discrete spatial data. I would like to make an approximation of the spatial boundaries of this data so that I can produce a plot with another dataset on top of it. Ideally, this would be an ordered set of (x,y) points that matplotlib can plot with the plt.Polygon() patch. My initial attempt is very inelegant: I place a fine grid over the data, and where data is found in a cell, a square matplotlib patch is created of that cell. The resolution of the boundary thus depends on the sampling frequency of the grid. Here is an example, where the grey region are the cells containing data, black where no data exists. OK, problem solved - why am I still here? Well.... I'd like a more "elegant" solution, or at least one that is faster (ie. I don't want to get on with "real" work, I'd like to have some fun with this!). The best way I can think of is a ray-tracing approach - eg: from xmin to xmax, at y=ymin, check if data boundary crossed in intervals dx y=ymin+dy, do 1 do 1-2, but now sample in y An alternative is defining a centre, and sampling in r-theta space - ie radial spokes in dtheta increments. Both would produce a set of (x,y) points, but then how do I order/link neighbouring points them to create the boundary? A nearest neighbour approach is not appropriate as, for example (to borrow from Geography), an isthmus (think of Panama connecting N&S America) could then close off and isolate regions. This also might not deal very well with the holes seen in the data, which I would like to represent as a different plt.Polygon. The solution perhaps comes from solving an area maximisation problem. For a set of points defining the data limits, what is the maximum contiguous area contained within those points To form the enclosed area, what are the neighbouring points for the nth point? How will the holes be treated in this scheme - is this erring into topology now? Apologies, much of this is me thinking out loud. I'd be grateful for some hints, suggestions or solutions. I suspect this is an oft-studied problem with many solution techniques, but I'm looking for something simple to code and quick to run... I guess everyone is, really! Cheers, David

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• Windows Question: RunOnce/Second Boot Issues [closed]

  - by Greg

  Moved to Super User: Windows Question: RunOnce/Second Boot Issues I am attempting to create a Windows XP SP3 image that will run my application on Second Boot. Here is the intended workflow. 1) Run Image Prep Utility (I wrote) on windows to add my runonce entries and clean a few things up. 2) Reboot to ghost, make image file. 3) Package into my ISO and distribute. 4) System will be imaged by user. 5) On first boot, I have about 5 things that run, one of which includes a driver updater (I wrote) for my own specific devices. 6) One of the entries inside of HKCU/../runonce is a reg file, which adds another key to HKLM/../runonce. This is how second boot is acquired. 7) As a result of the driver updater, user is prompted to reboot. 8) My application is then launched from HKLM/../runonce on second boot. This workflow works perfectly, except for a select few legacy systems that contain devices that cause the add hardware wizard to pop up. When the add hardware wizard pops up is when I begin to see problems. It's important to note, that if I manually inspect the registry after the add hardware wizard pops up, it appears as I would expect, with all the first boot scripts having run, and it's sitting in a state I would correctly expect it to be in for a second boot scenario. The problem comes when I click next on the add hardware wizard, it seems to re-run the single entry I've added, and re-executes the runonce scripts. (only one script now as it's already executed and cleared out the initial entries). This causes my application to open as if it were a second boot, only when next is clicked on the add hardware wizard. If I click cancel, and reboot, then it also works as expected. I don't care as much about other solutions, because I could design a system that doesn't fully rely on Microsoft's registry. I simply can't find any information as to WHY this is happening. I believe this is some type of Microsoft issue that's presenting itself as a result of an overstretched image that's expected to support too many legacy platforms, but any help that can be provided would be appreciated. Thanks,

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• Using Singleton synchronized array with NSThread

  - by hmthur

  I have a books app with a UISearchBar, where the user types any book name and gets search results (from ext API call) below as he types. I am using a singleton variable in my app called retrievedArray which stores all the books. @interface Shared : NSObject { NSMutableArray *books; } @property (nonatomic, retain) NSMutableArray *books; + (id)sharedManager; @end This is accessed in multiple .m files using NSMutableArray *retrievedArray; ...in the header file retrievedArray = [[Shared sharedManager] books]; My question is how do I ensure that the values inside retrievedArray remain synchronized across all the classes. Actually the values inside retrievedArray gets added through an NSXMLParser (i.e. through external web service API). There is a separate XMLParser.m file, where I do all the parsing and fill the array. The parsing is done on a separate thread. - (void) run: (id) param { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; NSXMLParser *parser = [[NSXMLParser alloc] initWithContentsOfURL: [self URL]]; [parser setDelegate: self]; [parser parse]; [parser release]; NSString *tmpURLStr = [[self URL]absoluteString]; NSRange range_srch_book = [tmpURLStr rangeOfString:@"v1/books"]; if (range_srch_book.location != NSNotFound) [delegate performSelectorOnMainThread:@selector(parseDidComplete_srch_book) withObject:nil waitUntilDone:YES]; [pool release]; } - (void) parseXMLFile: (NSURL *) url { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; [self setURL: url]; NSThread* myThread = [[NSThread alloc] initWithTarget:self selector:@selector(run:) object: nil]; [retrievedArray removeAllObjects]; [myThread start]; [pool release]; } There seems to be some synchronization issues if the user types very quickly (It seems to be working fine if the user types slowly)....So there are 2 views in which the content of an object in this shared array item is displayed; List and Detail. If user types fast and clicks on A in List view, he is shown B in detail view...That is the main issue. I have tried literally all the solutions I could think of, but am still unable to fix the issue. Please suggest some suitable fixes.

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• Chrome extension: sendMessage doesn't work

  - by user3334776

  I've already read the documentation from Google on 'message passing' a few times and have probably looked at over 10 other questions with the same problem and already tried quiet a few variations of most of their "solutions" and of what I have below... This is black magic, right? Either way, here it goes. Manifest File: { "manifest_version" : 2, "name" : "Message Test", "version" : "1.0", "browser_action": { "default_popup": "popup.html" }, "background": { "scripts": ["background.js"] }, "content_scripts": [ { "matches" : ["<all_urls>"], "js": ["message-test.js"] } ] } I'm aware extensions aren't suppose to use inline JS, but I'm leaving this in so the original question can be left as it was since I still can't get the message to send from the background page, When I switch from the popup to the background, I removed the appropriate lines from the manifest.json popup.html file: <html> <head> <script> chrome.tabs.query({active: true, currentWindow: true}, function(tabs) { chrome.tabs.sendMessage(tabs[0].id, {greeting: "hello", theMessage: "Why isn\'t this working?"}, function(response) { console.log(response.farewell); }); }); </script> </head> <body> </body> </html> OR background.js file: chrome.tabs.query({active: true, currentWindow: true}, function(tabs) { chrome.tabs.sendMessage(tabs[0].id, {greeting: "hello", theMessage: "Why isn\'t this working?"}, function(response) { console.log(response.farewell); }); }); message-test.js file: var Mymessage; chrome.runtime.onMessage.addListener(function(message, sender, sendResponse) { if (message.greeting == "hello"){ Mymessage = message.theMessage; alert(Mymessage); } else{ sendResponse({}); } }); No alert(Mymessage) goes off. I'm also trying to execute this after pressing a button from a popup and having a window at a specified url, but that's a later issue. The other files can be found here except with the background.js content wrapped in an addEventListener("click"....: http://pastebin.com/KhqxLx5y AND http://pastebin.com/JaGcp6tj

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• Setting up Netbeans/Eclipse for Linux Kernel Development

  - by red.october

  Hi: I'm doing some Linux kernel development, and I'm trying to use Netbeans. Despite declared support for Make-based C projects, I cannot create a fully functional Netbeans project. This is despite compiling having Netbeans analyze a kernel binary that was compiled with full debugging information. Problems include: files are wrongly excluded: Some files are incorrectly greyed out in the project, which means Netbeans does not believe they should be included in the project, when in fact they are compiled into the kernel. The main problem is that Netbeans will miss any definitions that exist in these files, such as data structures and functions, but also miss macro definitions. cannot find definitions: Pretty self-explanatory - often times, Netbeans cannot find the definition of something. This is partly a result of the above problem. can't find header files: self-explanatory I'm wondering if anyone has had success with setting up Netbeans for Linux kernel development, and if so, what settings they used. Ultimately, I'm looking for Netbeans to be able to either parse the Makefile (preferred) or extract the debug information from the binary (less desirable, since this can significantly slow down compilation), and automatically determine which files are actually compiled and which macros are actually defined. Then, based on this, I would like to be able to find the definitions of any data structure, variable, function, etc. and have complete auto-completion. Let me preface this question with some points: I'm not interested in solutions involving Vim/Emacs. I know some people like them, but I'm not one of them. As the title suggest, I would be also happy to know how to set-up Eclipse to do what I need While I would prefer perfect coverage, something that only misses one in a million definitions is obviously fine SO's useful "Related Questions" feature has informed me that the following question is related: http://stackoverflow.com/questions/149321/what-ide-would-be-good-for-linux-kernel-driver-development. Upon reading it, the question is more of a comparison between IDE's, whereas I'm looking for how to set-up a particular IDE. Even so, the user Wade Mealing seems to have some expertise in working with Eclipse on this kind of development, so I would certainly appreciate his (and of course all of your) answers. Cheers

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• How to add new object to an IList mapped as a one-to-many with NHibernate?

  - by Jørn Schou-Rode

  My model contains a class Section which has an ordered list of Statics that are part of this section. Leaving all the other properties out, the implementation of the model looks like this: public class Section { public virtual int Id { get; private set; } public virtual IList<Static> Statics { get; private set; } } public class Static { public virtual int Id { get; private set; } } In the database, the relationship is implemented as a one-to-many, where the table Static has a foreign key pointing to Section and an integer column Position to store its index position in the list it is part of. The mapping is done in Fluent NHibernate like this: public SectionMap() { Id(x => x.Id); HasMany(x => x.Statics).Cascade.All().LazyLoad() .AsList(x => x.WithColumn("Position")); } public StaticMap() { Id(x => x.Id); References(x => x.Section); } Now I am able to load existing Statics, and I am also able to update the details of those. However, I cannot seem to find a way to add new Statics to a Section, and have this change persisted to the database. I have tried several combinations of: mySection.Statics.Add(myStatic) session.Update(mySection) session.Save(myStatic) but the closest I have gotten (using the first two statements), is to an SQL exception reading: "Cannot insert the value NULL into column 'Position'". Clearly an INSERT is attempted here, but NHibernate does not seem to automatically append the index position to the SQL statement. What am I doing wrong? Am I missing something in my mappings? Do I need to expose the Position column as a property and assign a value to it myself? EDIT: Apparently everything works as expected, if I remove the NOT NULL constraint on the Static.Position column in the database. I guess NHibernate makes the insert and immediatly after updates the row with a Position value. While this is an anwers to the question, I am not sure if it is the best one. I would prefer the Position column to be not nullable, so I still hope there is some way to make NHibernate provide a value for that column directly in the INSERT statement. Thus, the question is still open. Any other solutions?

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• How to stream semi-live audio over internet

  - by Thomas Tempelmann

  I want to write something like Skype, i.e. I have a constant audio stream on one computer and then recompress it in a format that's suitable for a latent internet connection, receive it on the other end and play it. Let's also assume that the internet connection is fairly modern and fast, i.e. DSL or alike, no slow connections over phone and such. The involved computers will also be rather modern (Dual Core Intel CPUs at 2GHz or more). I know how to handle the audio on the machines. What I don't know is how to transmit the audio in an efficient way. The challenges are: I'd like get good audio quality across the line. The stream should be received without drops. The stream may, however, be received with a little delay (a second delay is acceptable). I imagine that the transport software could first determine the average (and max) latency, then start the stream and tell the receiver to wait for that max latency before starting to play the audio. With that, if the latency doesn't get any higher, the entire stream will be playable on the other side without stutter or drops. If, due to unexpected IP latencies or blockages, the stream does get cut off, I want to be able to notice this so that I can take actions (e.g. abort the stream) and eventually start a new transmission. What are my options if I want do use ready-made software for the compression and tranmission? I have no intention to write my own audio compression engine, really. OTOH, I plan to sell the solution in a vertical market, meaning I can afford a few dollars of license fees per copy, but not $100s. I guess the simplest solution would be to just open a TCP stream, send a few packets back and forth to determine their running time (or even use UDP for that), then use the results as the guide for my max latency value, then simply fire the audio data in its raw form (uncompressed 16 bit stereo), along with a timing code over the TCP connection. The receiver reads the data and plays it with the pre-determined delay. That might just work with the type of fast connection I expect. I just wonder if there are better solutions to reach this goal, with better performance (lower latency) and less data (compressed). BTW, I first try to implement this on OS X, but might want to do it on Windows, too, if it proves successful.

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• centering a div without setting width

  - by Daniel

  Is there a way to do this? When using navigation that can change the number of items often, it would be nice not having to calculate the with and updating the css, but just having a solution that works. if that's impossible (I'm assuming it is) can anyone point me to a javascript that can do this? edit re: provide code some code basically I'm working with, what I think is, the most typical setup <div class="main"> <div class="nav"> <ul> <li>short title</li> <li>Item 3 Long title</li> <li>Item 4 Long title</li> <li>Item 5 Long title</li> <li>Item 6 Extra Long title</li> </ul> </div> </div> edit .main { width:100%; text-align:center; } .nav { margin:0 auto; } .nav ul li { display:inline; text-align:left; } the issue I've found with this/these solutions is that the content is nudged to the right adding some right padding (of 40px) seems to fix this across the browsers I'm checking on (O FF IE). .nav { margin:0 auto; padding-right:40px; } I don't know where this value is coming from though and why 40px fixes this. Does anyone know where this is coming from? it's not a margin or padding but no matter what I do the first about 40px can not be used for placement. Maybe it's the ul or li that's adding this. I've had a look at the display:table-cell way of doing this, but there's that complication with IE and it still has the same issue as the other solution edit (final) okay I've tried some things in regard to the indent. I've reset all padding to 0 *{padding:0;} that fixed it, and I don't need to offset the padding (I think I'll leave my whole process up so if anyone comes across this, it'll save them some time) thanks for the comments and replies

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• LinearLayout as custom button, OnClickListener never called

  - by ohra

  I've been using the common Android Button with both icon (drawableTop) and text. It works really poorly if you want to have a non-standard size button, so I decided to make a custom button with a LinearLayout having the following layout: <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" style="@style/ButtonHoloDark" android:layout_width="fill_parent" android:layout_height="fill_parent" android:gravity="center" android:clickable="true" android:focusable="true" android:orientation="vertical" > <ImageView android:id="@+id/buttonIcon" android:layout_width="fill_parent" android:layout_height="wrap_content" android:duplicateParentState="true" /> <TextView android:id="@+id/buttonText" android:layout_width="fill_parent" android:layout_height="wrap_content" android:duplicateParentState="true" android:gravity="center" android:textColor="@color/white" /> </LinearLayout> The layout is used by a custom class: public class CustomIconButton extends LinearLayout { public CustomIconButton(Context context, AttributeSet attrs) { super(context, attrs); setAttributes(context, attrs); LayoutInflater.from(context).inflate(R.layout.custom_icon_button, this, true); } ... But when I set an OnClickListener on my button in its parent layout it never gets called. I can only receive clicks if a set the listener to the ImageView and/or TextView. This leads to two possible effects when the button is clicked: The click is inside the ImageView or the TextView. The click is registered ok, but the buttons state drawable doesn't change i.e. it doesn't appear depressed. The click is inside the "empty area" of the button. The click is not registered, but the state drawable works ok. Neither of these is feasible. I've played around with the following attributes on the LinearLayout or its children, but none really seem to have any effect whether true or false: duplicateParentState clickable focusable There doesn't seem to be any reasonable way to get the LinearLayout parent receive clicks instead of its children. I've seen some possible solutions overriding dispatchTouchEvent or onInterceptTouchEvent on the custom component itself, but that really seems like a big mess if I have to start analyzing touch events to identify proper clicks. So OnClickListener on a LinearLayout with children = no go?

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• Rails 3 - development errors in production mode

  - by skrafi

  Im using Rails, Passenger (both are 3.0.5) and Nginx on my production server. As I heard, Rails should show public/404.html or public/500.html instead of development errors like ActiveRecord::RecordNotFound or Unknown action but that doesn't happen. I've tried to delete config.ru file and set rack_env or rails_env in nginx.conf but nothing helped. Here is my nginx.conf: worker_processes 1; events { worker_connections 1024; } http { passenger_root /home/makk/.rvm/gems/ruby-1.9.2-p0/gems/passenger-3.0.5; passenger_ruby /home/makk/.rvm/bin/passenger_ruby; #passenger_ruby /home/makk/.rvm/wrappers/ruby-1.9.2-p0/ruby; include mime.types; default_type application/octet-stream; sendfile on; keepalive_timeout 65; server { listen 80; server_name localhost; location / { root /home/makk/projects/1server/deploy/current/public; index index.html index.htm; passenger_enabled on; rack_env production; recursive_error_pages on; if (-f /home/makk/projects/1server/maintenance.html) { return 503; } error_page 404 /404.html; error_page 500 502 504 /500.html; error_page 503 @503; } location @503 { error_page 405 = /maintenance.html; # Serve static assets if found. if (-f $request_filename) { break; } rewrite ^(.*)$ /maintenance.html break; } location ~ ^(\/phpmyadmin\/)(.*)$ { fastcgi_pass 127.0.0.1:9000; fastcgi_index index.php; fastcgi_split_path_info ^(\/phpmyadmin\/)(.*)$; fastcgi_param SCRIPT_FILENAME /usr/share/phpmyadmin/$fastcgi_path_info; include fastcgi_params; } } } It seems that this question duplicates this one but there are no working suggestions. UPD: I have both development and production apps on same PC. In production Rails ignores config.consider_all_requests_local = false (in /config/environments/production.rb) due to local_request? method. So one of possible solutions is listed below (taken from here): # config/initializers/local_request_override.rb module CustomRescue def local_request? return false if Rails.env.production? || Rails.env.staging? super end end ActionController::Base.class_eval do include CustomRescue end Or for Rails 3: class ActionDispatch::Request def local? false end end

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• Parallel programming in C#

  - by Alxandr

  I'm interested in learning about parallel programming in C#.NET (not like everything there is to know, but the basics and maybe some good-practices), therefore I've decided to reprogram an old program of mine which is called ImageSyncer. ImageSyncer is a really simple program, all it does is to scan trough a folder and find all files ending with .jpg, then it calculates the new position of the files based on the date they were taken (parsing of xif-data, or whatever it's called). After a location has been generated the program checks for any existing files at that location, and if one exist it looks at the last write-time of both the file to copy, and the file "in its way". If those are equal the file is skipped. If not a md5 checksum of both files is created and matched. If there is no match the file to be copied is given a new location to be copied to (for instance, if it was to be copied to "C:\test.jpg" it's copied to "C:\test(1).jpg" instead). The result of this operation is populated into a queue of a struct-type that contains two strings, the original file and the position to copy it to. Then that queue is iterated over untill it is empty and the files are copied. In other words there are 4 operations: 1. Scan directory for jpegs 2. Parse files for xif and generate copy-location 3. Check for file existence and if needed generate new path 4. Copy files And so I want to rewrite this program to make it paralell and be able to perform several of the operations at the same time, and I was wondering what the best way to achieve that would be. I've came up with two different models I can think of, but neither one of them might be any good at all. The first one is to parallelize the 4 steps of the old program, so that when step one is to be executed it's done on several threads, and when the entire of step 1 is finished step 2 is began. The other one (which I find more interesting because I have no idea of how to do that) is to create a sort of worker and consumer model, so when a thread is finished with step 1 another one takes over and performs step 2 at that object (or something like that). But as said, I don't know if any of these are any good solutions. Also, I don't know much about parallel programming at all. I know how to make a thread, and how to make it perform a function taking in an object as its only parameter, and I've also used the BackgroundWorker-class on one occasion, but I'm not that familiar with any of them. Any input would be appreciated.

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• Persistent (purely functional) Red-Black trees on disk performance

  - by Waneck

  I'm studying the best data structures to implement a simple open-source object temporal database, and currently I'm very fond of using Persistent Red-Black trees to do it. My main reasons for using persistent data structures is first of all to minimize the use of locks, so the database can be as parallel as possible. Also it will be easier to implement ACID transactions and even being able to abstract the database to work in parallel on a cluster of some kind. The great thing of this approach is that it makes possible implementing temporal databases almost for free. And this is something quite nice to have, specially for web and for data analysis (e.g. trends). All of this is very cool, but I'm a little suspicious about the overall performance of using a persistent data structure on disk. Even though there are some very fast disks available today, and all writes can be done asynchronously, so a response is always immediate, I don't want to build all application under a false premise, only to realize it isn't really a good way to do it. Here's my line of thought: - Since all writes are done asynchronously, and using a persistent data structure will enable not to invalidate the previous - and currently valid - structure, the write time isn't really a bottleneck. - There are some literature on structures like this that are exactly for disk usage. But it seems to me that these techniques will add more read overhead to achieve faster writes. But I think that exactly the opposite is preferable. Also many of these techniques really do end up with a multi-versioned trees, but they aren't strictly immutable, which is something very crucial to justify the persistent overhead. - I know there still will have to be some kind of locking when appending values to the database, and I also know there should be a good garbage collecting logic if not all versions are to be maintained (otherwise the file size will surely rise dramatically). Also a delta compression system could be thought about. - Of all search trees structures, I really think Red-Blacks are the most close to what I need, since they offer the least number of rotations. But there are some possible pitfalls along the way: - Asynchronous writes -could- affect applications that need the data in real time. But I don't think that is the case with web applications, most of the time. Also when real-time data is needed, another solutions could be devised, like a check-in/check-out system of specific data that will need to be worked on a more real-time manner. - Also they could lead to some commit conflicts, though I fail to think of a good example of when it could happen. Also commit conflicts can occur in normal RDBMS, if two threads are working with the same data, right? - The overhead of having an immutable interface like this will grow exponentially and everything is doomed to fail soon, so this all is a bad idea. Any thoughts? Thanks! edit: There seems to be a misunderstanding of what a persistent data structure is: http://en.wikipedia.org/wiki/Persistent_data_structure

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• How can I send multiple types of objects across Protobuf?

  - by cyclotis04

  I'm implementing a client-server application, and am looking into various ways to serialize and transmit data. I began working with Xml Serializers, which worked rather well, but generate data slowly, and make large objects, especially when they need to be sent over the net. So I started looking into Protobuf, and protobuf-net. My problem lies in the fact that protobuf doesn't sent type information with it. With Xml Serializers, I was able to build a wrapper which would send and receive any various (serializable) object over the same stream, since object serialized into Xml contain the type name of the object. ObjectSocket socket = new ObjectSocket(); socket.AddTypeHandler(typeof(string)); // Tells the socket the types socket.AddTypeHandler(typeof(int)); // of objects we will want socket.AddTypeHandler(typeof(bool)); // to send and receive. socket.AddTypeHandler(typeof(Person)); // When it gets data, it looks for socket.AddTypeHandler(typeof(Address)); // these types in the Xml, then uses // the appropriate serializer. socket.Connect(_host, _port); socket.Send(new Person() { ... }); socket.Send(new Address() { ... }); ... Object o = socket.Read(); Type oType = o.GetType(); if (oType == typeof(Person)) HandlePerson(o as Person); else if (oType == typeof(Address)) HandleAddress(o as Address); ... I've considered a few solutions to this, including creating a master "state" type class, which is the only type of object sent over my socket. This moves away from the functionality I've worked out with Xml Serializers, though, so I'd like to avoid that direction. The second option would be to wrap protobuf objects in some type of wrapper, which defines the type of object. (This wrapper would also include information such as packet ID, and destination.) It seems silly to use protobuf-net to serialize an object, then stick that stream between Xml tags, but I've considered it. Is there an easy way to get this functionality out of protobuf or protobuf-net? I've come up with a third solution, and posted it below, but if you have a better one, please post it too!

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• Nested Transaction issues within custom Windows Service

  - by pdwetz

  I have a custom Windows Service I recently upgraded to use TransactionScope for nested transactions. It worked fine locally on my old dev machine (XP sp3) and on a test server (Server 2003). However, it fails on my new Windows 7 machine as well as on 2008 Server. It was targeting 2.0 framework; I tried targeting 3.5 instead, but it still fails. The strange part is really in how it fails; no exception is thrown. The service itself merely times out. I added tracing code, and it fails when opening the connection for Database lookup #2 below. I also enabled tracing for System.Transactions; it literally cuts out partway while writing the block for the failed connection. We ran a SQL trace, but only the first lookup shows up. I put in code traces, and it gets to the trace the line before the second lookup, but nothing after. I've had the same experience hitting two different SQL servers (both are SQL 2005 running on Server 2003). The connection string is utilizing a SQL account (not Windows integration). All connections are against the same database in this case, but given the nature of the code it is being escalated to MSDTC. Here's the basic code structure: TransactionOptions options = new TransactionOptions(); options.IsolationLevel = System.Transactions.IsolationLevel.ReadCommitted; using (TransactionScope scope = new TransactionScope(TransactionScopeOption.RequiresNew, options)) { // Database lookup #1 TransactionOptions options = new TransactionOptions(); options.IsolationLevel = Transaction.Current != null ? Transaction.Current.IsolationLevel : System.Transactions.IsolationLevel.ReadCommitted; using (TransactionScope scope = new TransactionScope(TransactionScopeOption.Required, options)) { // Database lookup #2; fails on connection.Open() // Database save (never reached) scope.Complete();<br/> } scope.Complete();<br/> } My local firewall is disabled. The service normally runs using Network Service, but I also tried my user account (same results). The short of it is that I use the same general technique widely in my web applications and haven't had any issues. I pulled out the code and ran it fine within a local Windows Form application. If anyone has any additional debugging ideas (or, even better, solutions) I'd love to hear them.

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• Scalable Database Tagging Schema

  - by Longpoke

  EDIT: To people building tagging systems. Don't read this. It is not what you are looking for. I asked this when I wasn't aware that RDBMS all have their own optimization methods, just use a simple many to many scheme. I have a posting system that has millions of posts. Each post can have an infinite number of tags associated with it. Users can create tags which have notes, date created, owner, etc. A tag is almost like a post itself, because people can post notes about the tag. Each tag association has an owner and date, so we can see who added the tag and when. My question is how can I implement this? It has to be fast searching posts by tag, or tags by post. Also, users can add tags to posts by typing the name into a field, kind of like the google search bar, it has to fill in the rest of the tag name for you. I have 3 solutions at the moment, but not sure which is the best, or if there is a better way. Note that I'm not showing the layout of notes since it will be trivial once I get a proper solution for tags. Method 1. Linked list tagId in post points to a linked list in tag_assoc, the application must traverse the list until flink=0 post: id, content, ownerId, date, tagId, notesId tag_assoc: id, tagId, ownerId, flink tag: id, name, notesId Method 2. Denormalization tags is simply a VARCHAR or TEXT field containing a tab delimited array of tagId:ownerId. It cannot be a fixed size. post: id, content, ownerId, date, tags, notesId tag: id, name, notesId Method 3. Toxi (from: http://www.pui.ch/phred/archives/2005/04/tags-database-schemas.html, also same thing here: http://stackoverflow.com/questions/20856/how-do-you-recommend-implementing-tags-or-tagging) post: id, content, ownerId, date, notesId tag_assoc: ownerId, tagId, postId tag: id, name, notesId Method 3 raises the question, how fast will it be to iterate through every single row in tag_assoc? Methods 1 and 2 should be fast for returning tags by post, but for posts by tag, another lookup table must be made. The last thing I have to worry about is optimizing searching tags by name, I have not worked that out yet. I made an ASCII diagram here: http://pastebin.com/f1c4e0e53

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• ASP.Net MVC Ajax form with jQuery validation

  - by Tomas Lycken

  I have an MVC view with a form built with the Ajax.BeginForm() helper method, and I'm trying to validate user input with the jQuery Validation plugin. I get the plugin to highlight the inputs with invalid input data, but despite the invalid input the form is posted to the server. How do I stop this, and make sure that the data is only posted when the form validates? My code The form: <fieldset> <legend>leave a message</legend> <% using (Ajax.BeginForm("Post", new AjaxOptions { UpdateTargetId = "GBPostList", InsertionMode = InsertionMode.InsertBefore, OnSuccess = "getGbPostSuccess", OnFailure = "showFaliure" })) { %> <div class="column" style="width: 230px;"> <p> <label for="Post.Header"> Rubrik</label> <%= Html.TextBox("Post.Header", null, new { @style = "width: 200px;", @class="text required" }) %></p> <p> <label for="Post.Post"> Meddelande</label> <%= Html.TextArea("Post.Post", new { @style = "width: 230px; height: 120px;" }) %></p> </div> <p> <input type="submit" value="OK!" /></p> </fieldset> The JavaScript validation: $(document).ready(function() { // for highlight var elements = $("input[type!='submit'], textarea, select"); elements.focus(function() { $(this).parents('p').addClass('highlight'); }); elements.blur(function() { $(this).parents('p').removeClass('highlight'); }); // for validation $("form").validate(); }); EDIT: As I was getting downvotes for publishing follow-up problems and their solutions in answers, here is also the working validate method... function ajaxValidate() { return $('form').validate({ rules: { "Post.Header": { required: true }, "Post.Post": { required: true, minlength: 3 } }, messages: { "Post.Header": "Please enter a header", "Post.Post": { required: "Please enter a message", minlength: "Your message must be 3 characters long" } } }).form(); }

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• What classes should I map against with NHibernate?

  - by apollodude217

  Currently, we use NHibernate to map business objects to database tables. Said business objects enforce business rules: The set accessors will throw an exception on the spot if the contract for that property is violated. Also, the properties enforce relationships with other objects (sometimes bidirectional!). Well, whenever NHibernate loads an object from the database (e.g. when ISession.Get(id) is called), the set accessors of the mapped properties are used to put the data into the object. What's good is that the middle tier of the application enforces business logic. What's bad is that the database does not. Sometimes crap finds its way into the database. If crap is loaded into the application, it bails (throws an exception). Sometimes it clearly should bail because it cannot do anything, but what if it can continue working? E.g., an admin tool that gathers real-time reports runs a high risk of failing unnecessarily instead of allowing an admin to even fix a (potential) problem. I don't have an example on me right now, but in some instances, letting NHibernate use the "front door" properties that also enforce relationships (especially bidi) leads to bugs. What are the best solutions? Currently, I will, on a per-property basis, create a "back door" just for NHibernate: public virtual int Blah {get {return _Blah;} set {/*enforces BR's*/}} protected virtual int _Blah {get {return blah;} set {blah = value;}} private int blah; I showed the above in C# 2 (no default properties) to demonstrate how this gets us basically 3 layers of, or views, to blah!!! While this certainly works, it does not seem ideal as it requires the BL to provide one (public) interface for the app-at-large, and another (protected) interface for the data access layer. There is an additional problem: To my knowledge, NHibernate does not give you a way to distinguish between the name of the property in the BL and the name of the property in the entity model (i.e. the name you use when you query, e.g. via HQL--whenever you give NHibernate the name (string) of a property). This becomes a problem when, at first, the BR's for some property Blah are no problem, so you refer to it in your O/R mapping... but then later, you have to add some BR's that do become a problem, so then you have to change your O/R mapping to use a new _Blah property, which breaks all existing queries using "Blah" (common problem with programming against strings). Has anyone solved these problems?!

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• How to download file into string with progress callback?

  - by Kaminari

  I would like to use the WebClient (or there is another better option?) but there is a problem. I understand that opening up the stream takes some time and this can not be avoided. However, reading it takes a strangely much more amount of time compared to read it entirely immediately. Is there a best way to do this? I mean two ways, to string and to file. Progress is my own delegate and it's working good. FIFTH UPDATE: Finally, I managed to do it. In the meantime I checked out some solutions what made me realize that the problem lies elsewhere. I've tested custom WebResponse and WebRequest objects, library libCURL.NET and even Sockets. The difference in time was gzip compression. Compressed stream lenght was simply half the normal stream lenght and thus download time was less than 3 seconds with the browser. I put some code if someone will want to know how i solved this: (some headers are not needed) public static string DownloadString(string URL) { WebClient client = new WebClient(); client.Headers["User-Agent"] = "Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/532.5 (KHTML, like Gecko) Chrome/4.1.249.1045 Safari/532.5"; client.Headers["Accept"] = "application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5"; client.Headers["Accept-Encoding"] = "gzip,deflate,sdch"; client.Headers["Accept-Charset"] = "ISO-8859-2,utf-8;q=0.7,*;q=0.3"; Stream inputStream = client.OpenRead(new Uri(URL)); MemoryStream memoryStream = new MemoryStream(); const int size = 32 * 4096; byte[] buffer = new byte[size]; if (client.ResponseHeaders["Content-Encoding"] == "gzip") { inputStream = new GZipStream(inputStream, CompressionMode.Decompress); } int count = 0; do { count = inputStream.Read(buffer, 0, size); if (count > 0) { memoryStream.Write(buffer, 0, count); } } while (count > 0); string result = Encoding.Default.GetString(memoryStream.ToArray()); memoryStream.Close(); inputStream.Close(); return result; } I think that asyncro functions will be almost the same. But i will simply use another thread to fire this function. I dont need percise progress indication.

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• Loading the last related record instantly for multiple parent records using Entity framework

  - by Guillaume Schuermans

  Does anyone know a good approach using Entity Framework for the problem described below? I am trying for our next release to come up with a performant way to show the placed orders for the logged on customer. Of course paging is always a good technique to use when a lot of data is available I would like to see an answer without any paging techniques. Here's the story: a customer places an order which gets an orderstatus = PENDING. Depending on some strategy we move that order up the chain in order to get it APPROVED. Every change of status is logged so we can see a trace for statusses and maybe even an extra line of comment per status which can provide some extra valuable information to whoever sees this order in an interface. So an Order is linked to a Customer. One order can have multiple orderstatusses stored in OrderStatusHistory. In my testscenario I am using a customer which has 100+ Orders each with about 5 records in the OrderStatusHistory-table. I would for now like to see all orders in one page not using paging where for each Order I show the last relevant Status and the extra comment (if there is any for this last status; both fields coming from OrderStatusHistory; the record with the highest Id for the given OrderId). There are multiple scenarios I have tried, but I would like to see any potential other solutions or comments on the things I have already tried. Trying to do Include() when getting Orders but this still results in multiple queries launched on the database. Each order triggers an extra query to the database to get all orderstatusses in the history table. So all statusses are queried here instead of just returning the last relevant one, plus 100 extra queries are launched for 100 orders. You can imagine the problem when there are 100000+ orders in the database. Having 2 computed columns on the database: LastStatus, LastStatusInformation and a regular Linq-Query which gets those columns which are available through the Entity-model. The problem with this approach is the fact that those computed columns are determined using a scalar function which can not be changed without removing the formula from the computed column, etc... In the end I am very familiar with SQL and Stored procedures, but since the rest of the data-layer uses Entity Framework I would like to stick to it as long as possible, even though I have my doubts about performance. Using the SQL approach I would write something like this: WITH cte (RN, OrderId, [Status], Information) AS ( SELECT ROW_NUMBER() OVER (PARTITION BY OrderId ORDER BY Id DESC), OrderId, [Status], Information FROM OrderStatus ) SELECT o.Id, cte.[Status], cte.Information AS StatusInformation, o.* FROM [Order] o INNER JOIN cte ON o.Id = cte.OrderId AND cte.RN = 1 WHERE CustomerId = @CustomerId ORDER BY 1 DESC; which returns all orders for the customer with the statusinformation provided by the Common Table Expression. Does anyone know a good approach using Entity Framework?

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• Representing xml through a single class

  - by Charles

  I am trying to abstract away the difficulties of configuring an application that we use. This application takes a xml configuration file and it can be a bit bothersome to manually edit this file, especially when we are trying to setup some automatic testing scenarios. I am finding that reading xml is nice, pretty easy, you get a network of element nodes that you can just go through and build your structures quite nicely. However I am slowly finding that the reverse is not quite so nice. I want to be able to build a xml configuration file through a single easy to use interface and because xml is composed of a system of nodes I am having a lot of struggle trying to maintain the 'easy' part. Does anyone know of any examples or samples that easily and intuitively build xml files without declaring a bunch of element type classes and expect the user to build the network themselves? For example if my desired xml output is like so <cook version="1.1"> <recipe name="chocolate chip cookie"> <ingredients> <ingredient name="flour" amount="2" units="cups"/> <ingredient name="eggs" amount="2" units="" /> <ingredient name="cooking chocolate" amount="5" units="cups" /> </ingredients> <directions> <direction name="step 1">Preheat oven</direction> <direction name="step 2">Mix flour, egg, and chocolate</direction> <direction name="step 2">bake</direction> </directions> </recipe> <recipe name="hot dog"> ... How would I go about designing a class to build that network of elements and make one easy to use interface for creating recipes? Right now I have a recipe object, an ingredient object, and a direction object. The user must make each one, set the attributes in the class and attach them to the root object which assembles the xml elements and outputs the formatted xml. Its not very pretty and I just know there has to be a better way. I am using python so bonus points for pythonic solutions

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• I'm searching for a messaging platform (like XMPP) that allows tight integration with a web applicat

  - by loxs

  Hi, At the company I work for, we are building a cluster of web applications for collaboration. Things like accounting, billing, CRM etc. We are using a RESTfull technique: For database we use CouchDB Different applications communicate with one another and with the database via http. Besides, we have a single sign on solution, so that when you login in one application, you are automatically logged to the other. For all apps we use Python (Pylons). Now we need to add instant messaging to the stack. We need to support both web and desktop clients. But just being able to chat is not enough. We need to be able to achieve all of the following (and more similar things). When somebody gets assigned to a task, they must receive a message. I guess this is possible with some system daemon. There must be an option to automatically group people in groups by lots of different properties. For example, there must be groups divided both by geographical location, by company division, by job type (all the programers from different cities and different company divisions must form a group), so that one can send mass messages to a group of choice. Rooms should be automatically created and destroyed. For example when several people visit the same invoice, a room for them must be automatically created (and they must auto-join). And when all leave the invoice, the room must be destroyed. Authentication and authorization from our applications. I can implement this using custom solutions like hookbox http://hookbox.org/docs/intro.html but then I'll have lots of problems in supporting desktop clients. I have no former experience with instant messaging. I've been reading about this lately. I've been looking mostly at things like ejabberd. But it has been a hard time and I can't find whether what I want is possible at all. So I'd be happy if people with experience in this field could help me with some advice, articles, tales of what is possible etc.

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• How to compute a unicode string which bidirectional representation is specified?

  - by valdo

  Hello, fellows. I have a rather pervert question. Please forgive me :) There's an official algorithm that describes how bidirectional unicode text should be presented. http://www.unicode.org/reports/tr9/tr9-15.html I receive a string (from some 3rd-party source), which contains latin/hebrew characters, as well as digits, white-spaces, punctuation symbols and etc. The problem is that the string that I receive is already in the representation form. I.e. - the sequence of characters that I receive should just be presented from left to right. Now, my goal is to find the unicode string which representation is exactly the same. Means - I need to pass that string to another entity; it would then render this string according to the official algorithm, and the result should be the same. Assuming the following: The default text direction (of the rendering entity) is RTL. I don't want to inject "special unicode characters" that explicitly override the text direction (such as RLO, RLE, etc.) I suspect there may exist several solutions. If so - I'd like to preserve the RTL-looking of the string as much as possible. The string usually consists of hebrew words mostly. I'd like to preserve the correct order of those words, and characters inside those words. Whereas other character sequences may (and should) be transposed. One naive way to solve this is just to swap the whole string (this takes care of the hebrew words), and then swap inside it sequences of non-hebrew characters. This however doesn't always produce correct results, because actual rules of representation are rather complex. The only comprehensive algorithm that I see so far is brute-force check. The string can be divided into sequences of same-class characters. Those sequences may be joined in random order, plus any of them may be reversed. I can check all those combinations to obtain the correct result. Plus this technique may be optimized. For instance the order of hebrew words is known, so we only have to check different combinations of their "joining" sequences. Any better ideas? If you have an idea, not necessarily the whole solution - it's ok. I'll appreciate any idea. Thanks in advance.

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• initializing a vector of custom class in c++

  - by Flamewires

  Hey basically Im trying to store a "solution" and create a vector of these. The problem I'm having is with initialization. Heres my class for reference class Solution { private: // boost::thread m_Thread; int itt_found; int dim; pfn_fitness f; double value; std::vector<double> x; public: Solution(size_t size, int funcNo) : itt_found(0), x(size, 0.0), value(0.0), dim(30), f(Eval_Functions[funcNo]) { for (int i = 1; i < (int) size; i++) { x[i] = ((double)rand()/((double)RAND_MAX))*maxs[funcNo]; } } Solution() : itt_found(0), x(31, 0.0), value(0.0), dim(30), f(Eval_Functions[1]) { for (int i = 1; i < 31; i++) { x[i] = ((double)rand()/((double)RAND_MAX))*maxs[1]; } } Solution operator= (Solution S) { x = S.GetX(); itt_found = S.GetIttFound(); dim = S.GetDim(); f = S.GetFunc(); value = S.GetValue(); return *this; } void start() { value = f (dim, x); } /* plus additional getter/setter methods*/ } Solution S(30, 1) or Solution(2, 5) work and initalizes everything, but I need X of these solution objects. std::vector<Solution> Parents(X) will create X solutions with the default constructor and i want to construct using the (int, int) constructor. Is there any easy(one liner?) way to do this? Or would i have to do something like: size_t numparents = 10; vector<Solution> Parents; Parents.reserve(numparents); for (int i = 0; i<(int)numparents; i++) { Solution S(31, 0); Parents.push_back(S); }

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