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• How does PHP's list function work?

  - by Jacob Relkin

  After recently answering a couple of questions here on SO that involved utilizing PHP's list function, I wondered, "how in the world does that function actually work under the hood?". I was thinking about something like using func_get_args() and then iterating through the argument list, and that's all nice and peachy, but then how in the world does the assignment part work? list(...) = array($x, $y, $z); isn't this ^ evaluated first? So to be precise, my question is how is the list function able to create scoped variables which get assigned to the not-yet evaluated array?

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• OO and Writing Drupal Modules

  - by Aaron

  Preface: Yes, I've read: http://drupal.org/node/547518 I am writing 'foo' module for Drupal6, where I am organizing the code in an OO fashion. There's a class called Foo that has a bunch of setters and accessors, and it is working quite well at abstracting some pretty nasty code and SQL. The question is is it common practice to expose a class for other modules, or is it better to wrap things in the more typical foo_myfnname()? For example, if I am writing the module's docs, should I tell people to do this: $foo = new Foo(); $something = $foo->get_something(); or tell them to call: foo_get_something(); which under the hood does: function foo_get_something() { $foo = new Foo(); return $foo->get_something(); }

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• Question of using static_cast on "this" pointer in a derived object to base class

  - by Johnyy

  Hi, this is an example taken from Effective C++ 3ed, it says that if the static_cast is used this way, the base part of the object is copied, and the call is invoked from that part. I wanted to understand what is happening under the hood, will anyone help? class Window { // base class public: virtual void onResize() { } // base onResize impl }; class SpecialWindow: public Window { // derived class public: virtual void onResize() { // derived onResize impl; static_cast<Window>(*this).onResize(); // cast *this to Window, // then call its onResize; // this doesn't work! // do SpecialWindow- } // specific stuff };

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• [PHP] - Lowering script memory usage in a "big" file creation

  - by Riccardo

  Hi there people, it looks like I'm facing a typical memory outage problem when using a PHP script. The script, originally developed by another person, serves as an XML sitemap creator, and on large websites uses quite a lot of memory. I thought that the problem was related due to an algorithm holding data in memory until the job was done, but digging into the code I have discovered that the script works in this way: open file in output (will contain XML sitemap entries) in the loop: ---- for each entry to be added in sitemap, do fwrite close file end Although there are no huge arrays or variables being kept in memory, this technique uses a lot of memory. I thought that maybe PHP was buffering under the hood the fwrites and "flushing" data at the end of the script, so I have modified the code to close and open the file every Nth record, but the memory usage is still the same.... I'm debugging the script on my computer and watching memory usage: while script execution runs, memory allocation grows. Is there a particular technique to instruct PHP to free unsed memory, to force flushing buffers if any? Thanks

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• Manage groups of build configurations in Hudson

  - by Lóránt Pintér

  I'm using Hudson to build my application. I have several branches that come and go. Whenever there's a new branch, I have to set up the following builds for it: a continuous build that runs after every change in SVN a nightly build a nightly site generation (I'm using Maven under the hood) and a weekly integration build for some branches currently this means I need to copy four template configurations and set them up with the branch URL. I don't like this for two reasons: It's redundant, so modifying something is error-prone and takes a lot of time. I need four full checkouts of the product per branch on every build slave, plus four separate private Maven repository, not to mention the built artifacts. This is a lot of space wasted. What I'd like instead is to have one workspace and one configuration for allthese builds. Is this possible with Hudson?

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• NSMutableSet addObject question

  - by Jacob Relkin

  I've got a class that wraps around an NSMutableSet object, and I have an instance method that adds objects (using the addObject: method) to the NSMutableSet. This works well, but I'm smelling a performance hitch because inside the method i'm explicitly calling containsObject: before adding the object to the set. Three part question: Do I need to be calling containsObject: before I add an object to the set? If so, then what actual method should I be using, containsObject or containsObjectIdenticalTo:? If that is not so, what contains method gets invoked under the hood of addObject:? This is important to me because if I pass an object to containsObject: it would return true, but if I pass it to containsObjectIdenticalTo: it would return false.

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• Has Object in VB 2010 received the same optimalization as dynamic in C# 4.0?

  - by Abel

  Some people have argued that the C# 4.0 feature introduced with the dynamic keyword is the same as the "everything is an Object" feature of VB. However, any call on a dynamic variable will be translated into a delegate once and from then on, the delegate will be called. In VB, when using Object, no caching is applied and each call on a non-typed method involves a whole lot of under-the-hood reflection, sometimes totaling a whopping 400-fold performance penalty. Have the dynamic type delegate-optimization and caching also been added to the VB untyped method calls, or is VB's untyped Object still so slow?

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• Verifying compiler optimizations in gcc/g++ by analyzing assembly listings

  - by Victor Liu

  I just asked a question related to how the compiler optimizes certain C++ code, and I was looking around SO for any questions about how to verify that the compiler has performed certain optimizations. I was trying to look at the assembly listing generated with g++ (g++ -c -g -O2 -Wa,-ahl=file.s file.c) to possibly see what is going on under the hood, but the output is too cryptic to me. What techniques do people use to tackle this problem, and are there any good references on how to interpret the assembly listings of optimized code or articles specific to the GCC toolchain that talk about this problem?

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• Getting ready for learn html5

  - by vtortola

  Hi, I'm a desktop application developer, and I plan learning html5, but as it's not released, there is no (almost) published books and no too much infomation from beginners on the web... I fell I should start with html4 and the current web development skills. I think, I should start with html4, css and javascript... but there are so many technologies related that I get lost :D So, what current technologies will be sill used when html5 be released? I mean, what about "jquery" and "ajax"? I know they are javascript under the hood, but will they still make sense in the future? What would you recommend me considering that I have just a little bit of html knowlegde, almost null CSS and completely null in javascript? Thanks in advance.

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• very simple delegate musing

  - by Ted

  Sometimes the simplest questions make me love C/C++ and C# more and more. Today sitting on the bus musing aout delegates I remembered reading somwhere you don't need to use the new keyword when instaniating a new delegate. For example: public static void SomeMethod(string message) { ... } ... public delegate void TestDelgate(string message); //Define a delegate ........... //create a new instance ..METHOD 1 TestDelgate t = new TestDelgate(SomeMethod); //OR another way to create a new instance ..METHOD 2 TestDelgate t = SomeMethod; //create a new instance ..METHOD 2 So todays questions are What happens under the hood in method 2. Does the compiler expand method 2 into method 1, hence writing TestDelgate t = SomeMethod; is just a shortcut for TestDelgate t = new TestDelgate(SomeMethod);, or is there another reason for the exsitence of method 2 Do you guys think method 1 or method 2 is better for readability (this is a subjective question, but I'd just like to get a unscientific feel of general opinion of stackoverflow :-))

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• Possible to see what actual SQL queries Rails invokes when using console script?

  - by randombits

  Sometimes I like to pop open the console script that comes with Rails to test small excerpts of code. That code normally involves some more involved ActiveRecord queries. Although not an expert in ActiveRecord, I'm proficient with SQL and want to see what it's translating underneath the hood for efficiency purposes. This will help me refactor or rethink how I'm writing my app if it looks inefficient. Now when the query is in the actual application itself, it all shows up in logs. Ad-hoc ActiveRecord queries in the console do not though. Anyway to change that behavior?

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• Quicklfix related question(FIX::Application)

  - by Pradyot

  I am trying to use FIX::Application along with SessionSettings. The Fix server I am trying to connect to does not see any incoming connection. From my side I see a Logon Message being formulated in toAdmin() callback(which I print out and add certain fields to. The Question is 1. Do I need to call some form of sendTarget in toAdmin?(I tried that but get a Session not found error) 2. Is there anyway I can increase logging(start logging whats going on under the hood). Thanks

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• How does array class work in Java?

  - by oks16

  In Java, array is a class and extends Object. I am curious to know about this special array class. I don't find the class definition anywhere. Doing a getClass().getName() gives strange result. String[] array = new String[]{"one","two"}; System.out.println(array.getClass().getName()); // prints [Ljava.lang.String; I want to understand how array works under the hood. Is the array class definition hardcoded in the JVM? Any resources, books, links on this will be helpful. Thank you.

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• What are the differences between these three patterns of "class" definitions in JavaScript?

  - by user1889765

  Are there any important/subtle/significant differences under the hood when choosing to use one of these three patterns over the others? And, are there any differences between the three when "instantiated" via Object.create() vs the new operator? The pattern that CoffeeScript uses when translating "class" definitions: Animal = (function() { function Animal(name) { this.name = name; } Animal.prototype.move = function(meters) { return alert(this.name + (" moved " + meters + "m.")); }; return Animal; })(); and The pattern that Knockout seems to promote: var DifferentAnimal = function(name){ var self = this; self.name = name; self.move = function(meters){ return alert(this.name + (" moved " + meters + "m.")); }; return {name:self.name, move:self.move}; } and The pattern that Backbone promotes: var OneMoreAnimal= ClassThatAlreadyExists.extend({ name:'', move:function(){} });

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• before_filter not inheriting from parent controller correctly?

  - by Scott

  Sorry if this may be a stupid question but I'm unable get my filters to inherit the way the Rails 3 documentation is saying it should. Specifically I have an Admin controller that was generated via: rails generate controller admin I added only a single action to the admin controller, the before filter & the private filter method class AdminController < ApplicationController before_filter require_admin_creds def index end private def require_admin_creds unless current_user && current_user.admin? flash[:error] = ... redirect_to .... end end end I next then created my nested resources under the admin section with: rails generate scaffold admin/model While my admin index is indeed getting the filter, the admin/model index (or any other actions) are not. What is happening under the hood here that I must have excluded? Thanks in advance.

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• How to research unmanaged memory leaks in .NET?

  - by Brandon

  I have a WCF service running over MSMQ. Memory gradually increases over time, indicating that there is some sort of memory leak. I ran the service locally and monitored some counters using PerfMon. Total CLR memory managed heap bytes remains relatively constant, while the process' private bytes increases over time. This leads me to believe that there is some sort of unmanaged memory leak. Assuming that unmanaged memory leak is the issue, how do I address the issue? Are there any tools I could use to give me hints as to what is causing the unmanaged memory leak? Also, all my service is doing is reading from the transactional queue and writing to a database, all as part of a DTC transaction (handled under the hood by requiring a transaction on the service contract). I am not doing anything explicitly with COM or DllImports. Thanks in advance!

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• How does this JavaScript/JQuery Syntax work: (function( window, undefined ) { })(window)?

  - by DKinzer

  Have you ever taken a look under the hood at the JQuery 1.4 source code and noticed how it's encapsulated in the following way: (function( window, undefined ) { //All the JQuery code here ... })(window); I've read an article on JavaScript Namespacing and another one called "An Important Pair of Parens," so I know some about what's going on here. But I've never seen this particular syntax before. What is that undefined doing there? And why does window need to be passed and then appear at the end again?

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• system() call returns "Permission Denied" on Windows XP

  - by bde

  I am experiencing a problem with a C program running on Windows XP that is getting Permission Denied (EACCES) errors when it tries to call system(). It doesn't seem to matter what I put in the command string, the commands all work manually but get Permission Denied errors when executed via system() The other interesting thing is that the program works correctly on other XP machines, just not this one. That makes it feel like some kind of OS setting, but I am not totally sure what system() does under the hood and would like to understand what is happening here. Thanks.

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• Looking for resources for learning SharePoint Foundation on the Internet

  - by Kabeer

  Hello. While I am quite comfortable with the .Net world, I am a baby as far as SharePoint technologies are concerned. With the advent of SharePoint 2010 (Foundation especially), I'd like to directly learn the new version. However, I am not getting enough resources on the Internet that can be helpful. Besides knowing to maneuver a SharePoint site, I'd like to understand stuff under the hood from the architecture standpoint and subsequently the APIs. Can the community please guide me to the most suitable resource(s) available on the Internet?

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• Should properties in C# perform a lot of work?

  - by Hamish Grubijan

  When a property is read from or is assigned to, one would not expect it to perform a lot of work. When setSomeValue(...) and getSomeValue(...) methods are used instead, one should not be that surprised that something non-trivial might be going on under the hood. However, now that C# gave the world Properties, it seems silly to use getter and setter methods instead. What is your take on this? Should I mark this Q as a community wiki? Thanks.

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• Should I be using libraries if I'm trying to learn how to program?

  - by CodeJustin.com

  I have been programming "a lot" in the past few months and at first I was trying to find the "easyest" language. Fortunately I realized that it's not about the language, it's about learning HOW to code. I ran into the Stanford lectures online (programming methodology) and I watched them all (around 23 hours total) awhile ago. Then I got into Java ME and programmed about 28.47% of a mobile RPG game (only around 2k lines of code). I feel like I learned a lot from those two experiences compared to previous ones but now that I'm moving into flash/actionscript 3.0 development and I'm finding myself learning like I did when I first started with PHP. I'm not really getting whats under the hood kind of. I'm finding myself using libraries to speed up development time which doesn't seem like a bad thing BUT I personally do not know how to write the libraries myself off hand. So should I be coding everything myself or is it ok to use libraries when you don't even know how to code them?

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• OWB 11gR2 &ndash; Flexible and extensible

  - by David Allan

  The Oracle data integration extensibility capabilities are something I love, nothing more frustrating than a tool or platform that is very constraining. I think extensibility and flexibility are invaluable capabilities in the data integration arena. I liked Uli Bethke's posting on some extensibility capabilities with ODI (see Nesting ODI Substitution Method Calls here), he has some useful guidance on making customizations to existing KMs, nice to learn by example. I thought I'd illustrate the same capabilities with ODI's partner OWB for the OWB community. There is a whole new world of potential. The LKM/IKM/CKM/JKMs are the primary templates that are supported (plus the Oracle Target code template), so there is a lot of potential for customizing and extending the product in this release. Enough waffle... Diving in at the deep end from Uli's post, in OWB the table operator has a number of additional properties in OWB 11gR2 that let you annotate the column usage with ODI-like properties such as the slowly changing usage or for your own user-defined purpose as in Uli's post, below you see for the target table SALES_TARGET we can use the UD5 property which when assigned the code template (knowledge module) which has been modified with Uli's change we can do custom things such as creating indices - provides The code template used by the mapping has the additional step which is basically the code illustrated from Uli's posting just used directly, the ODI 10g substitution references also supported from within OWB's runtime. Now to see whether this does what we expect before we execute it, we can check out the generated code similar to how the traditional mapping generation and preview works, you do this by clicking on the 'Inspect Code' button on the execution units code template assignment. This then  creates another tab with prefix 'Code - <mapping name>' where the generated code is put, scrolling down we find the last step with the indices being created, looks good, so we are ready to deploy and execute. After executing the mapping we can then use the 'Audit Information' panel (select the mapping in the designer tree and click on View/Audit Information), this gives us a view of the execution where we can drill into the tasks that were executed and inspect both the template and the generated code that was executed and any potential errors. Reflecting back on earlier versions of OWB, these were the kinds of features that were always highly desirable, getting under the hood of the code generation and tweaking bit and pieces - fun and powerful stuff! We can step it up a bit here and explore some further ideas. The example below is a daisy-chained set of execution units where the intermediate table is a target of one unit and the source for another. We want that table to be a global temporary table, so can tweak the templates. Back to the copy of SQL Control Append (for demo purposes) we modify the create target table step to make the table a global temporary table, with the option of on commit preserve rows. You can get a feel for some of the customizations and changes possible, providing some great flexibility and extensibility for the data integration tools.

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• Internet Explorer 9 RC Now Available: Here’s the Most Interesting New Stuff

  - by The Geek

  Yesterday Microsoft announced the release candidate of Internet Explorer 9, which is very close to the final product. Here’s a screenshot tour of the most interesting new stuff, as well as answers to your questions. The most important question is should you install this version? And the answer is absolutely yes. Even if you don’t use IE, it’s better to have a newer, more secure version on your PC. What’s New Under the Hood in Release Candidate vs Beta? If you want to see the full list of changes with all the original marketing detail, you can read Microsoft’s Beauty of the Web page, but here’s the highlights that you might be interested in. Improved Performance – they’ve made a lot of changes, and it really feels faster, especially when using more intensive web apps like Gmail. Power Consumption Settings – since the JavaScript engine in any browser uses a lot of CPU power, they’ve now integrated it into the power settings, so if you’re on battery it will use less CPU, and save battery life. This is really a great change. UI Changes – The tab bar can now be moved below the address bar (see below for more), they’ve shaved some pixels off the design to save space, and now you can toggle the Menu bar to be always on. Pinned Sites – now you can pin multiple pages to a single taskbar button. Very useful if you always use a couple web apps together. You can also pin a site in InPrivate mode. FlashBlock and AdBlock are Integrated (sorta) – there’s a new ActiveX filtering that lets you enable plug-ins only for sites you trust. There’s also a tracking protection list that can block certain content (which can obviously be used to block ads). Geolocation – while a lot of privacy conscious people might complain about this, if you use your laptop while traveling, it’s really useful to have geo-located features when using Google Maps, etc. Don’t worry, it won’t leak your privacy by default. WebM Video – Yeah, Google recently removed H.264 from Chrome, but Microsoft has added Google’s WebM video format to Internet Explorer. Keep reading for more about using the new features Latest Features How-To Geek ETC Internet Explorer 9 RC Now Available: Here’s the Most Interesting New Stuff Here’s a Super Simple Trick to Defeating Fake Anti-Virus Malware How to Change the Default Application for Android Tasks Stop Believing TV’s Lies: The Real Truth About "Enhancing" Images The How-To Geek Valentine’s Day Gift Guide Inspire Geek Love with These Hilarious Geek Valentines The 50 Faces of Mario Death [Infographic] Clean Up Google Calendar’s Interface in Chrome and Iron The Rise and Fall of Kramerica? [Seinfeld Video] GNOME Shell 3 Live CDs for OpenSUSE and Fedora Available for Testing Picplz Offers Special FX, Sharing, and Backup of Your Smartphone Pics BUILD! An Epic LEGO Stop Motion Film [VIDEO]

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• Need to Know

  - by Tony Davis

  Sometimes, I wonder whether writers of documentation, tutorials and articles stop to ask themselves one very important question: Does the reader really need to know this? I recently took on the task of writing a concise series of articles about the transaction log, what is it, how it works and why it's important. It was an enjoyable task; rather like peering inside a giant, complex clock mechanism. Initially, one sees only the basic components, which work to guarantee the integrity of database transactions, and preserve these transactions so that data can be restored to a previous point in time. On closer inspection, one notices all of small, arcane mechanisms that are necessary to make this happen; LSNs, virtual log files, log chains, database checkpoints, and so on. It was engrossing, escapist, stuff; what I'd written looked weighty and steeped in mysterious significance. Suddenly, however, I jolted myself back to reality with the awful thought "does anyone really need to know all this?" The driver of a car needs only to be dimly aware of what goes on under the hood, however exciting the mechanism is to the engineer. Similarly, while everyone who uses SQL Server ought to be aware of the transaction log, its role in guaranteeing the ACID properties, and how to control its growth, the intricate mechanisms ticking away under its clock face are a world away from the daily work of the harassed developer. The DBA needs to know more, such as the correct rituals for ensuring optimal performance and data integrity, setting the appropriate growth characteristics, backup routines, restore procedures, and so on. However, even then, the average DBA only needs to understand enough about the arcane processes to spot problems and react appropriately, or to know how to Google for the best way of dealing with it. The art of technical writing is tied up in intimate knowledge of your audience and what they need to know at any point. It means serving up just enough at each point to help the reader in a practical way, but not to overcook it, or stuff the reader with information that does them no good. When I think of the books and articles that have helped me the most, they have been full of brief, practical, and well-informed guidance, based on experience. This seems far-removed from the 900-page "beginner's guides" that one now sees everywhere. The more I write and edit, the more I become convinced that the real art of technical communication lies in knowing what to leave out. In what areas do the SQL Server technical materials suffer from "information overload"? Where else does it seem that concise, practical advice is drowned out by endless discussion of the "clock mechanisms"? Cheers, Tony.

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• SQL SERVER – DMV – sys.dm_exec_query_optimizer_info – Statistics of Optimizer

  - by pinaldave

  Incredibly, SQL Server has so much information to share with us. Every single day, I am amazed with this SQL Server technology. Sometimes I find several interesting information by just querying few of the DMV. And when I present this info in front of my client during performance tuning consultancy, they are surprised with my findings. Today, I am going to share one of the hidden gems of DMV with you, the one which I frequently use to understand what’s going on under the hood of SQL Server. SQL Server keeps the record of most of the operations of the Query Optimizer. We can learn many interesting details about the optimizer which can be utilized to improve the performance of server. SELECT * FROM sys.dm_exec_query_optimizer_info WHERE counter IN ('optimizations', 'elapsed time','final cost', 'insert stmt','delete stmt','update stmt', 'merge stmt','contains subquery','tables', 'hints','order hint','join hint', 'view reference','remote query','maximum DOP', 'maximum recursion level','indexed views loaded', 'indexed views matched','indexed views used', 'indexed views updated','dynamic cursor request', 'fast forward cursor request') All occurrence values are cumulative and are set to 0 at system restart. All values for value fields are set to NULL at system restart. I have removed a few of the internal counters from the script above, and kept only documented details. Let us check the result of the above query. As you can see, there is so much vital information that is revealed in above query. I can easily say so many things about how many times Optimizer was triggered and what the average time taken by it to optimize my queries was. Additionally, I can also determine how many times update, insert or delete statements were optimized. I was able to quickly figure out that my client was overusing the Query Hints using this dynamic management view. If you have been reading my blog, I am sure you are aware of my series related to SQL Server Views SQL SERVER – The Limitations of the Views – Eleven and more…. With this, I can take a quick look and figure out how many times Views were used in various solutions within the query. Moreover, you can easily know what fraction of the optimizations has been involved in tuning server. For example, the following query would tell me, in total optimizations, what the fraction of time View was “reference“. As this View also includes system Views and DMVs, the number is a bit higher on my machine. SELECT (SELECT CAST (occurrence AS FLOAT) FROM sys.dm_exec_query_optimizer_info WHERE counter = 'view reference') / (SELECT CAST (occurrence AS FLOAT) FROM sys.dm_exec_query_optimizer_info WHERE counter = 'optimizations') AS ViewReferencedFraction Reference : Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL DMV, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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