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• Building a Redundant / Distrubuted Application

  - by MattW

  This is more of a "point me in the right direction" question. I (and my team of 3) have built a hosted web app that queues and routes customer chat requests to available customer service agents (It does other things as well, but this is enough background to illustrate the issue). The basic dev architecture today is: a single page ajax web UI (ASP.NET MVC) with floating chat windows (think Gmail) a backend Windows service to queue and route the chat requests this service also logs the chats, calculates service levels, etc a Comet server product that routes data between the web frontend and the backend Windows service this also helps us detect which Agents are still connected (online) And our hardware architecture today is: 2 servers to host the web UI portion of the application a load balancer to route requests to the 2 different web app servers a third server to host the SQL Server DB and the backend Windows service responsible for queuing / delivering chats So as it stands today, one of the web app servers could go down and we would be ok. However, if something would happen to the SQL Server / Windows Service server we would be boned. My question - how can I make this backend Windows service logic be able to be spread across multiple machines (distributed)? The Windows service is written to accept requests from the Comet server, check for available Agents, and route the chat to those agents. How can I make this more distributed? How can I make it so that I can distribute the work of the backend Windows service can be spread across multiple machines for redundancy and uptime purposes? Will I need to re-write it with distributed computing in mind? I should also note that I am hosting all of this on Rackspace Cloud instances - so maybe it is something I should be less concerned about? Thanks in advance for any help!

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• Use of Service Bus in a Pub-Sub Engine

  - by JoseK

  In one of our projects, we've built a Publisher - Subscriber Engine on Oracle Service Bus. The functionality being a series of events are published and subscribers (JMS queues) receive these whenever a new event is published. We are facing some technical issues now, performance-wise and hence an architectural review is underway. Now for my questions: Architecturally the ESB has to publish events into a DB and read from the DB which users wish to be notified, then push the event onto their respective queues. There is a high amount of DB interaction and the question is whether ESB should be having such high amount of interaction with the DB in the first place? Or should there have been some alternate component responsible for doing this. Alternately is there any non-DB approach in which we can store the events and subscribers? Where else can this application data be held within the ESB context?

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• At what point would you drop some of your principles of software development for the sake of more money?

  - by MeshMan

  I'd like to throw this question out there to interestingly see where the medium is. I'm going to admit that in my last 12 months, I picked up TDD and a lot of the Agile values in software development. I was so overwhelmed with how much better my development of software became that I would never drop them out of principle. Until...I was offered a contracting role that doubled my take home pay for the year. The company I joined didn't follow any specific methodology, the team hadn't heard of anything like code smells, SOLID, etc., and I certainly wasn't going to get away with spending time doing TDD if the team had never even seen unit testing in practice. Am I a sell out? No, not completely... Code will always been written "cleanly" (as per Uncle Bob's teachings) and the principles of SOLID will always be applied to the code that I write as they are needed. Testing was dropped for me though, the company couldn't afford to have such a unknown handed to the team who quite frankly, even I did create test frameworks, they would never use/maintain the test framework correctly. Using that as an example, what point would you say a developer should never drop his craftsmanship principles for the sake of money/other benefits to them personally? I understand that this can be a very personal opinion on how concerned one is to their own needs, business needs, and the sake of craftsmanship etc. But one can consider that for example testing can be dropped if the company decided they would rather have a test team, than rather understand unit testing in programming, would that be something you could forgive yourself for like I did? So given that there is something you would drop, there usually should be an equal cost in the business that makes up for what you drop - hopefully, unless of course you are pretty much out for lining your own pockets and not community/social collaborating ;). Double your money, go back to RAD? Or walk on, and look for someone doing Agile, and never look back...

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• Onsite Interview : QA Engineer with more Emphasis on Java Skills

  - by coolrockers2007

  Hello I'm having a onsite interview for QA engineer with Startup. While phone interview the person said he would want to test my JAVA, JUnit and SQL skills on white board with more importance on Object-oriented skills, So what all can i questions can i expect ? One more important issue : How do i overcome the fear of White board interview ?. I'm very bad at White board sessions, i get fully tensed. Please suggest me tips to overcome my jinx

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• Gödel, Escher, Bach - Gödel's string

  - by Brad Urani

  In the book Gödel, Escher, Bach: An Eternal Golden Braid by Douglas Hofstadter, the author gives us a representation of the precursor to Gödel's string (Gödel's string's uncle) as: ~Ea,a': (I don't have the book in front of me but I think that's right). All that remains to get Gödel's string is to plug the Gödel number for this string into the free variable a''. What I don't understand is how to get the Gödel number for the functions PROOF-PAIR and ARITHMOQUINE. I understand how to write these functions in a programming language like FlooP (from the book) and could even write them myself in C# or Java, but the scheme that Hofstadter defines for Gödel numbering only applies to TNT (which is just his own syntax for natural number theory) and I don't see any way to write a procedure in TNT since it doesn't have any loops, variable assignments etc. Am I missing the point? Perhaps Gödel's string is not something that can actually be printed, but rather a theoretical string that need not actually be defined? I thought it would be neat to write a computer program that actually prints Gödel's string, or Gödel's string encoded by Gödel numbering (yes, I realize it would have a gazillion digits) but it seems like doing so requires some kind of procedural language and a Gödel numbering system for that procedural language that isn't included in the book. Of course once you had that, you could write a program that plugs random numbers into variable "a" and run procedure PROOF-PAIR on it to test for theoromhood of Gödel's string. If you let it run for a trillion years you might find a derivation that proves Gödel's string.

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• Why is it that software is still easily pirated today?

  - by mohabitar

  I've always been curious about this. Now I wouldn't call myself a programmer yet, but I'm learning, so maybe the answer to this is obvious. It just seems a little hard to believe that with all of our technological advances and the billions of dollars spent on engineering the most unbelievable and mind-blowing software, we still have no other means of protecting against piracy then a "serial number/activation key". I'm sure a ton of money, maybe even billions, went into creating Windows 7 or Office and even Snow Leopard, yet I can get it for free in less than 20 minutes. Same for all of Adobe's products, which are probably the easiest. I guess my question is: can there exist a fool proof and hack proof method of protecting your software against piracy? If not realistically, how about theoretically possible? Or no matter what mechanisms these companies deploy, hackers can always find a way around it? EDIT: So apparently, the answer is no. There's pretty much no way. And so I'm sure these big companies have realized this as well. Should they adopt another sales model rather than charging a crapload for their software (I know its justified and they put a lot of hard work into their software, but its still a lot of money). Are there any alternative solutions that will benefit both the company and the user (i.e. if you purchase our product, we'll apply $X dollars to your account that will apply to future purchases from our company)?

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• Overloading interface buttons, what are the best practices?

  - by XMLforDummies

  Imagine you'll have always a button labeled "Continue" in the same position in your app's GUI. Would you rather make a single button instance that takes different actions depending on the current state? private State currentState = State.Step1; private ContinueButton_Click() { switch(currentState) { case State.Step1: DoThis(); currentState = State.Step2; break; case State.Step2: DoThat(); break; } } Or would you rather have something like this? public Form() { this.ContinueStep2Button.Visible = false; } private ContinueStep1Button_Click() { DoThis(); this.ContinueStep1Button.Visible = false; this.ContinueStep2Button.Visible = true; } private ContinueStep2Button_Click() { DoThat(); }

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• Where to store global enterprise properties?

  - by shylynx

  I'm faced with a crowd of java applications, which need different global enterprise wide properties for operation, for example: hostname of the central RDBMS, hostname and location of the central self-service portal, host location of central LDAP, host location of central mail server etc. Formally we build each application with a properties file, where all this properties are definied. But that's a very bad solution, because if the hostname of the mail server changes, we need to change the properties files for each application and deploy all applications again. Our idea is to centralize this properties, so that each application can ask for each property at runtime, for example: Idea: Put the properties file to an easy accessible file share. So if we need to change a property, each application uses the new properties. Idea: Put the properties to database. Main disadvantage: we need a dependency to database client libraries for each application. Idea: Put all applications into one big application server, that provides system properties for each application. Main disadvantage: needs deployment of each application to one application server. But that isn't a realistic scenario. Idea: Webservice that provides global enterprise wide properties. Main disadvantage: not very secure, because some properties are passwords or user credentials. What other alternatives are recommended? What is state of the art?

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• How to discriminate commented code and documentation comments

  - by linquize

  After using version control tools, it is no longer necessary to comment out old code. However, some team members still comment out old code. Therefore, I want to clean them up. I want to mark commented lines which are really comments / documentation, so that every time I do not need to re-read all commented regions. The unmarked lines left are new commented code. How do I achieve this? Any existing tools or need to write on my own? Similar concept: in git, we have 'partial commit' to select some lines to commit. However, the lines marked in 'partial commit' is valid once only.

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• Should integer divide by zero halt execution?

  - by Pyrolistical

  I know that modern languages handle integer divide by zero as an error just like the hardware does, but what if we could design a whole new language? Ignoring existing hardware, what should a programming language does when an integer divide by zero occurs? Should it return a NaN of type integer? Or should it mirror IEEE 754 float and return +/- Infinity? Or is the existing design choice correct, and an error should be thrown? Is there a language that handles integer divide by zero nicely? EDIT When I said ignore existing hardware, I mean don't assume integer is represented as 32 bits, it can be represented in anyway you can to imagine.

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• how protect intellectual property when oursourcing software development?

  - by gkdsp

  I'm a small company needing to outsource software development. I've written both functional and technical specifications for GUI developers and back-end (C or PHP) developers to implement my software application. I'm a little nervous handing over copies of these documents to request bids from numerous companies. Looking for recommendations to protect my work while outsourcing. What's the conventional wisdom? Is there generic NDA someone could send me a link to. How do others handle this situation. What would the outsource companies expect, or not expect, from me?

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• Authentication for users on a Single Page App?

  - by John H

  I have developed a single page app prototype that is using Backbone on the front end and going to consume from a thin RESTful API on the server for it's data. Coming from heavy server side application development (php and python), I have really enjoyed the new different design approach with a thick client side MVC but am confused on how best to restrict the app to authenticated users who log in. I prefer to have the app itself behind a login and would also like to implement other types of logins eventually (openid, fb connect, etc) in addition to the site's native login. I am unclear how this is done and have been searching - but unsuccessful in finding information that made it clear to me. In the big picture, what is the current best practice for registering users and requiring them to login to use your single page app? Once a user is logged in, how are the api requests authenticated? Can I store a session but how do I detect for this session in the API calls? Any answers to this would be much appreciated!

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• Mutating Programming Language?

  - by MattiasK

  For fun I was thinking about how one could build a programming language that differs from OOP and came up with this concept. I don't have a strong foundation in computer science so it might be common place without me knowing it (more likely it's just a stupid idea :) I apologize in advance for this somewhat rambling question :) Anyways here goes: In normal OOP methods and classes are variant only upon parameters, meaning if two different classes/methods call the same method they get the same output. My, perhaps crazy idea, is that the calling method and class could be an "invisible" part of it's signature and the response could vary depending on who call's an method. Say that we have a Window object with a Break() method, now anyone (who has access) could call this method on Window with the same result. Now say that we have two different objects, Hammer and SledgeHammer. If Break need to produce different results based on these we'd pass them as parameters Break(IBluntObject bluntObject) With a mutating programming language (mpl) the operating objects on the method would be visible to the Break Method without begin explicitly defined and it could adopt itself based on them). So if SledgeHammer calls Window.Break() it would generate vastly different results than if Hammer did so. If OOP classes are black boxes then MPL are black boxes that knows who's (trying) to push it's buttons and can adapt accordingly. You could also have different permission sets on methods depending who's calling them rather than having absolute permissions like public and private. Does this have any advantage over OOP? Or perhaps I should say, would it add anything to it since you should be able to simply add this aspect to methods (just give access to a CallingMethod and CallingClass variable in context) I'm not sure, might be to hard to wrap one's head around, it would be kinda interesting to have classes that adopted themselves to who uses them though. Still it's an interesting concept, what do you think, is it viable?

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• When should I use static variables with primitive types?

  - by Felipe Cypriano

  Recently I came across the question NSString: Why use static over literal? and in the comments arrived a new question. In Objective-C there some "special" types that are just maps to C primitives. Like the NSInteger. #if __LP64__ || (TARGET_OS_EMBEDDED && !TARGET_OS_IPHONE) || TARGET_OS_WIN32 || NS_BUILD_32_LIKE_64 typedef long NSInteger; #else typedef int NSInteger; #endif I know how to use the static keywords for objects but I don't understand the implications on C primitive types. When should I use a static NSInteger x instead of NSInteger x? What happens with the memory in both cases?

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• How to handle mutiple API calls using javascript/jquery

  - by James Privett

  I need to build a service that will call multiple API's at the same time and then output the results on the page (Think of how a price comparison site works for example). The idea being that as each API call completes the results are sent to the browser immediately and the page would get progressively bigger until all process are complete. Because these API calls may take several seconds each to return I would like to do this via javascript/jquery in order to create a better user experience. I have never done anything like this before using javascript/jquery so I was wondering if there was any frameworks/advice that anyone would be willing to share.

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• How to manage focus for a small set of simple widgets

  - by Christoph

  I'm developing a set of simple widgets for a small (128x128) display. For example I'd like to have a main screen with an overlay menu which I can use to toggle visibilty of main screen elements. Each option would be an icon with a box around it while it is selected. Button (left, up, right, down, enter) events should be given to the widget that has "focus". Focus is a simple thing to understand when using a GUI, but I'm having trouble implementing this. Can you suggest a simple concept for managing focus and input events? I have these simple ideas: Only one widget can have focus, so I need a single pointer to that widget. When this widget gets some kind of "cycle" input (as in "highlight the next item in this list"), the focus is given to a different widget. a widget must have a way of telling the application which widget the focus is given to next. if a widget cannot give a "next focus" hint, the application must be able to figure out where the focus should go. Widgets are currently structured like this: A widget can have a parent, which is passed to the constructor. Widgets are created statically, as I want to avoid dynamic memory allocation (I only have 16kB of RAM and I'd like to have control over that). widgets have siblings, implemented as an intrusive linked list (they have a next member). A parent has a pointer to the head of its list of children. Input events are arguments to the widgets buttonEvent methods which can accept or ignore that event. If it ignores the event, it can pass the event to its parent. My Questions: How can I manage focus for these widgets? Am I making this too complicated?

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• Is it recommended to use more than one language at a startup?

  - by GoofyBall

  I work for a mobile startup where, for historical reasons, our chosen language was C#. I was recently assigned to a small project to build a tool that would be used by us internally. When I explained my intention to use Python to build this tool I was heavily criticized for this because introducing new languages, and technologies (Debian, Apache, Python and Django) into our ecosystem would make it harder for other developers to maintain (because only two other people know more than one language besides C#). I countered that this project would take far longer to develop in C# (which I think is an inherent problem with the language/.NET framework) and that the project was small and designed to solve a very particular problem. Of course it is necessary that the ecosystem be as a homogeneous as possible but if your are developing tooling, infrastructure, and internal systems when there are better things to build them with than C# then you should consider using them. By using one language you exclude a lot of other great libraries and frameworks out there, and this case it was the difference between taking one week to build in Python as opposed to a month in C#. Do you think it is acceptable to understand and use only only one language at a startup or even a larger company? Am I perhaps being naive??

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• Javascript: Machine Constants Applicable?

  - by DavidB2013

  I write numerical routines for students of science and engineering (although they are freely available for use by anybody else as well) and am wondering how to properly use machine constants in a JavaScript program, or if they are even applicable. For example, say I am writing a program in C++ that numerically computes the roots of the following equation: exp(-0.7x) + sin(3x) - 1.2x + 0.3546 = 0 A root-finding routine should be able to compute roots to within the machine epsilon. In C++, this value is specified by the language: DBL_EPSILON. C++ also specifies the smallest and largest values that can be held by a float or double variable. However, how does this convert to JavaScript? Since a Javascript program runs in a web browser, and I don't know what kind of computer will run the program, and JavaScript does not have corresponding predefined values for these quantities, how can I implement my own version of these constants so that my programs compute results to as much accuracy as allowed on the computer running the web browser? My first draft is to simply copy over the literal constants from C++: FLT_MIN: 1.17549435082229e-038 FLT_MAX: 3.40282346638529e+038 DBL_EPSILON: 2.2204460492503131e-16 I am also willing to write small code blocks that could compute these values for each machine on which the program is run. That way, a supercomputer might compute results to a higher accuracy than an old, low-level, PC. BUT, I don't know if such a routine would actually reach the computer, in which case, I would be wasting my time. Anybody here know how to compute and use (in Javascript) values that correspond to machine constants in a compiled language? Is it worth my time to write small programs in Javascript that compute DBL_EPSILON, FLT_MIN, FLT_MIN, etc. for use in numerical routines? Or am I better off simply assigning literal constants that come straight from C++ on a standard Windows PC?

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• How to choose the right web development language for my app without much programming experience?

  - by twinbornJoint

  I have my own idea for a web application, and I am not a programmer. The application will work similar to Facebook and Twitter, profiles and feeds. I have learned some computer science theory, all the way up to OOP, but have no practical experience. Without any experience, is there a way I can evaluate the different language and platform choices available to me? What kind of things should I be looking at? Ease of setup? How many followers it has? How can I evaluate whether a language will have the capabilities I need?

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• Humor in Documentation

  - by Lex Fridman

  Is a small amount of lighthearted wording or humor acceptable in source code documentation? For example, I have an algorithm that has a message hop around a graph (network) until its path forms a cycle. When this happens it is removed from the queue of the node it last resided on which removes it from memory. I write that in a comment, and finish the comment with "Rest in peace, little guy". That serves very little documenting purpose, but it cheers me up a bit, and I imagine it might cheer up other people I'm working with as they read through the code. Is this an acceptable practice, or should my in-code documentation resemble as much as possible the speeches of 2004 United States presidential candidate John Kerry? ;-)

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• Why are Javascript for/in loops so verbose?

  - by Matthew Scharley

  I'm trying to understand the reasoning behind why the language designers would make the for (.. in ..) loops so verbose. For example: for (var x in Drupal.settings.module.stuff) { alert("Index: " + x + "\nValue: " + Drupal.settings.module.stuff[x]); } It makes trying to loop over anything semi-complex like the above a real pain as you either have to alias the value locally inside the loop yourself, or deal with long access calls. This is especially painful if you have two to three nested loops. I'm assuming there is a reason why they would do things this way, but I'm struggling with the reasoning.

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• My boss is feuding with his boss. My workload is expanding What should I do?

  - by steve

  These two have always had a somewhat shaky relationship when they were on the same level. The other guy was recently promoted to director and now my boss reports to him. On the surface, they appear to get along when they get together, but my boss despises the man and badmouths him every chance that he gets (to peers, subordinates, etc). He believe that the director is setting him up to fail. The Director and upper management is holding my boss responsible for the not-so-great performance by the team as of late. He's been playing games to make my boss look bad. Due to lay offs, we don't have the manpower to deliever the results that we did before...but expectations have not lowered...and my boss is taking the heat for it. Now he's on the warpath and starting to micromanage. He's giving everyone more work. He's forcing us midlevel guys to take responsibility for the level one techs' performance. I'm spending less and less time coding....and more time babysitting vendors, techs, etc. I'm not so sure that's a bad thing because I'm sorta burnt out on coding, but I don't really care for the idea of having to be responsible for others poor performance....isn't that the manager's job? Anyway, do you guys have any suggestions on dealing with the situation?

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• Basis of definitions

  - by Yttrill

  Let us suppose we have a set of functions which characterise something: in the OO world methods characterising a type. In mathematics these are propositions and we have two kinds: axioms and lemmas. Axioms are assumptions, lemmas are easily derived from them. In C++ axioms are pure virtual functions. Here's the problem: there's more than one way to axiomatise a system. Given a set of propositions or methods, a subset of the propositions which is necessary and sufficient to derive all the others is called a basis. So too, for methods or functions, we have a desired set which must be defined, and typically every one has one or more definitions in terms of the others, and we require the programmer to provide instance definitions which are sufficient to allow all the others to be defined, and, if there is an overspecification, then it is consistent. Let me give an example (in Felix, Haskell code would be similar): class Eq[t] { virtual fun ==(x:t,y:t):bool => eq(x,y); virtual fun eq(x:t, y:t)=> x == y; virtual fun != (x:t,y:t):bool => not (x == y); axiom reflex(x:t): x == x; axiom sym(x:t, y:t): (x == y) == (y == x); axiom trans(x:t, y:t, z:t): implies(x == y and y == z, x == z); } Here it is clear: the programmer must define either == or eq or both. If both are defined, the definitions must be equivalent. Failing to define one doesn't cause a compiler error, it causes an infinite loop at run time. Defining both inequivalently doesn't cause an error either, it is just inconsistent. Note the axioms specified constrain the semantics of any definition. Given a definition of == either directly or via a definition of eq, then != is defined automatically, although the programmer might replace the default with something more efficient, clearly such an overspecification has to be consistent. Please note, == could also be defined in terms of !=, but we didn't do that. A characterisation of a partial or total order is more complex. It is much more demanding since there is a combinatorial explosion of possible bases. There is an reason to desire overspecification: performance. There also another reason: choice and convenience. So here, there are several questions: one is how to check semantics are obeyed and I am not looking for an answer here (way too hard!). The other question is: How can we specify, and check, that an instance provides at least a basis? And a much harder question: how can we provide several default definitions which depend on the basis chosen?

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• Why isn't the source code of programs shown in research papers released?

  - by Antoine

  Is there a reason why the source code of programs shown in research papers are not released ? I understand that research papers are more about the general idea of accomplishing something than implementation details, but I don't get why they don't release the code. For example, in this paper ends with: Results The human line drawing system is implemented through the Qt framework in C++ using OpenGL, and runs on a 2.00 GHz Intel dual core processor workstation without any additional hardware assistance. We can interactively draw lines while the system synthesizes the new path and texture. Do they keep the source code closed intentionally because of a monetization they intend to make with it, or because of copyright ?

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• What languages are most commonly used in medical research?

  - by Chris Taylor

  For someone about to go into a career in medical research, what language would be the most useful to learn? From my limited experience (I have been a researcher in mathematics and in finance) I have been able to recommend looking at R (for statistics) Matlab (for general numeric processing) and Python (for general purpose programming with statistics/numerics as an add-on) but I don't know which of those (if any) are in common use -- or if there are other, more specialized languages that are used. To be clear, I'm not talking about a professional programmer working in a medical setting. I am talking about a medical or genetics researcher who uses programming to analyse data, or generally to help get their work done.

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