ruby dynamic dispatch

So if I send it the get-x message, I'll get -4. So, in the body of this lambda, anytime it uses self, self will be bound to the entire object, and that's exactly what we need for dynamic dispatch. Take this object, call its distToOrigin method. supports HTML5 video. DiDithiRbDynamic Dispatch in Ruby Complicatons Modules(Modules (mixins)aswellasclasses) as well as classes Can add or change methods dynamically as the ppgrogram runs Can include per-object methods as well as per-class methods If we do, the cdr is the lambda, and let's call it yes with the args, but as it's first argument, the entire object itself. And at the end of the day, what you get is a Person instance that has name of John, age of 15. So far, we have seen that you could call the methods in Ruby with that notation. [As described below, this is Part C of a 3-part course. Excellent course that introduced me to the field of programming languages. I won't have any notion of classes, so this won't be quite how Ruby does OOP, but I will get dynamic dispatch even without classes and that's interesting too. And now the interesting one, let's call a method which we know is also called, sometimes, sending a message. In Rails with Active Record and Action Pack, we will explore how to interact with relational databases by using Active Record, a Ruby gem, which Rails uses by default for database access. Process of selecting which implementation of a polymorphic operation to call at run time. A Racket lambda that takes one more argument than you would expect, so both self and args, and that's the idea. If we find it, you set and mcdr to update it, otherwise, say we didn't find it. Here's a nice list of fields. But it's also fair to say that a language that was focused primarily on types for objects, like Java before Java added generics in the version five of the language, are equally hostile, if you will, to the sort of generic programming and polymorphic code with function closures that we saw in ML. [MUSIC] Hi and welcome to lecture five. So I hope you'll follow along and at least get the high level idea. Ruby has been described as a multi-paradigm programming language: it allows procedural programming (defining functions/variables … Other languages with dynamic dispatch (like C++ or Java) also allow for static dispatch. Ruby supports inheritance with dynamic dispatch, mixins and singleton methods (belonging to, and defined for, a single instance rather than being defined on the class). For methods, they will also have a name, like a get-x method for a getter, for the x field of a point object. All gists Back to GitHub Sign in Sign up Sign in Sign up {{ message }} Instantly share code, notes, and snippets. Consultez la traduction anglais-allemand de dynamic dispatch dans le dictionnaire PONS qui inclut un entraîneur de vocabulaire, les tableaux de conjugaison et les prononciations. For this purpose, the DLR has extended LINQ expression trees to include control flow, assignment, and other language-modeling nodes. For example, object.method, but you could also call it using a send method. The Ruby programming language does not have a Boolean data type as part of the language. We say the x field is initialized to the contents of the racket variable _x, the y field is initialized to the contents of the racket variable _y. And then in the reporting system, you would have methods, which would basically just delegate to the store methods. And you could imagine that you could also have a variable method name, for example, that gets assigned either a symbol or a string and then you could use that variable method name to send a message to, which obviously is the same thing as bark, so that works as well. Ruby supports inheritance with dynamic dispatch, mixins and singleton methods (belonging to, and defined for, a single instance rather than being defined on the class). And if there are more parameters, you can pass those in as well. So there are many ways we might do this. 8) Scope Class.new is an alternative to class Scope Gate: There are 3 ways to define a new scope in Ruby:. So, here I'm going to add a method, called distToOrigin. And then, the other part, is a function, but it's a function that takes one more argument than would otherwise need. We will then take a look at what role Active Record plays in the overall request-response cycle, when a client (the browser) requests data from the server, as well as how to submit the data to the server. What have I shown you so far? So, get is a function that takes an object and a field, so its a racket function, and returns the current contents of that field in that object. This makes each call on r dynamic.Only one version of this method needs to be created, but whenever r’s methods are called, the method must be looked up at runtime.This is done by having one static data per type that tells us where to find the respective methods. Dependent on maybe some other condition and the code doesn't have to find out until runtime, which method it needs to call. We have something called multiple dispatch and we have a very careful balance between the static and dynamic. So this is not something you would actually do in Racket. You would have to have a giant if else statement clause, that basically says, if method is name, then called this name method. Difference between += and concat January 23, 2016 Learning ruby is really fun and one should enjoy learning ruby language. In this module, we will begin exploring the database-interaction portion of Rails. Thanks to dynamic dispatch, when an instance of B has a call to odd that calls even, it will be this even, because that's what dynamic dispatch is all about. I'm going to use this lambda, and this lambda when you call it, will send self the get-x message, and by sending self the get-x message, we will get dynamic dispatch. Section 8 and Homework 6 (First Module with Ruby), To view this video please enable JavaScript, and consider upgrading to a web browser that, Optional: Dynamic Dispatch Manually in Racket. So if we don't find it, raise an error message as before. Ruby has been developed with features like dynamic typing and ducks typing, flexible syntax, inheritance, garbage collection, exception handling, overloading, lexical closures, iterators, built-in support, variable scope, custom dispatch behavior, centralized management system, … Amazing! We can see that right here. Next, we'll talk about this idea of Dynamic Methods in addition to Dynamic Dispatch. The following illustration shows the architecture of the dynamic language runtime. When you learn how to use all of the dynamic dispatch, meta-programming etc. So both fields and methods are going to be lists. Object-oriented systems model a problem as a set of interacting objects that enact operations referred to by … So in static languages, for example, Java. Restore already has all these methods and all we're doing is just delegating to methods in restore, get_piano_desc, get_piano_price and so on and you have to have all these duplicate methods. If I actually get a pair, return its putter. So, I'm gonna start with the methods in point, then I'm going to append on all these other things. It's a message and a greet method takes a greeting parameter and just prints it out. Here, .send acts upon “Hello World”, with “upcase” passed in as an argument, either in string or symbol form. And why is it called send? So for the fields I'm gonna take whatever fields you would get from making a point, as I do up here, and then add on to the front using a pen, an r field and a theta field. In this installment we talk about multiple dispatch This can only use basic authentication over SSL. Static Proxy Client: Requires proxy code generation at the client side. Le DLR fournit l’exécution rapide des opérations dynamiques en prenant en charge la mise en cache polymorphe avancée. Tweet: Search Discussions. Call a setter method and so on. The welcome message has a few additional comments about "what makes Ruby different" and how to approach the (rather different) homework assignment, so let's get started... [MUSIC] This segment doesn't have any material you need for the homework or the exam, but it really helps crystallize what dynamic dispatch is. know what all these topics mean. By using different languages, you will learn to think more deeply than in terms of the particular syntax of one language. But now lets get to the three main functions get, set and send. Before looking at Active Record, we will talk about some advanced Ruby features of meta-programming that will help facilitate our Active Record journey. So for the fields, it's just gonna be an mcons of some symbol, what's the name of the field, and then some value, that'll be the current contents of the field. After I set-y to 3, when I ask the distance to the origin again I get 5, so it really is perfect. The first method call will call a method on the second object. But now what we do is, we get the list of methods out of the object. I'm gonna show you a bunch of code in this segment. But there is an easier way to get started with SQL using the Active Record Object/Relational (ORM) framework. Difference between && and (and) in Ruby December 27, 2015 Till the date I used to believe that in ruby && and (and) are completely replaceable but in actual its not the case at all. Let's get started programming with Ruby, including learning about Ruby's variant of (almost) function closures and the "inheritance and overriding" that is the essence of object-oriented programming. So now let me flip over to the code, and basically show you just a few Racket functions that use these objects to implement object-oriented programming. So in static languages, for example, Java. We will start off with migrations that enable you to create and modify the schema of the database. I always find it helpful to understand the semantics of something by seeing how you could implement it using other constructs. Okay, back to the slides just to wrap up, I know this has gotten a little long. Let's set a field. At this point, we are ready to jump into active record. I will say one thing, though. And thanks to the dynamic dispatch, the distoOrigin lambda defined up here in make-point, when it now sends to self the get-x and get-y message on something created by make-polar-point, we will do the right thing and get the right value. And what I'm going to do here, is I'm going to create an object, here's my object constructor, that uses the field and methods of point, but then adds extra things on the front. You already know how to build a basic web application with the Ruby on Rails framework. We have a class called Dog who barks and he could maybe greet somebody with a greeting. To implement dynamic dispatch, evaluate the method body with self mapping to the receiver • That way, any self calls in the body use the receiver's class, – Not necessarily the class that defined the method • This much is the same in Ruby, Java, C#, Smalltalk, etc. Do the same computation to find the appropriate pair in our list of fields. ML's type system would really get in our way here. And in fact, this get-x method uses dynamic dispatch because when you call this lambda, we get self and we don't need any of the other arguments and so we then use our get method, which is on self with _x. Use a soak to get the appropriate lambda out. So all the bark method does is just prints out. Ruby supports inheritance with dynamic dispatch, mixins and singleton methods (belonging to, and defined for, a single instance rather than being defined on the class). The compiler requires you to define all the methods upfront. Share. The purposes range from adapting to environment to reducing amount of typing, while providing rich and convenient API. It plays nicely with Python. So we have the getter and the sender for the name and age attributes and then we instantiate a person and then all we wanna do is we wanna throw some properties at the person instance. We would have a class called store and for example, it has method get_piano_description, get_piano_price, get_violin_description, get_violin_price and many, many methods with the same pattern of get this desc and get this price. So why would you ever want a language with that dynamic? This is just a rounding error. We're not going to use anything in Racket that has dynamic dispatch given to us as the default. This course teach me a lot of complex things like authentication, nested resources and authorization. And in this case, you just throw properties up there. So you'll probably get a better picture of what's going on if I literally show you a picture. If I send it the get-y message, I'll get 0. Ruby Meta Programming. Adjunct Professor, Graduate Computer Science, To view this video please enable JavaScript, and consider upgrading to a web browser that. And Scala does the same thing as well. For example, we have a class called store, which has a description and a price of a store product and we are tasked to have a building a reporting system for the store to basically generate reports for different items in the store. Then take the cdr of that pair, which is this lambda, and call it with self being the entire object, being x. The course uses the languages ML, Racket, and Ruby as vehicles for teaching the concepts, but the real intent is to teach enough about how any language “fits together” to make you more effective programming in any language -- and in learning new ones. And basically, it means that you could decide at runtime, which methods to call. So what would this look like? Authentication, Active Record Pattern, Ruby On Rails. So something like my field's list and I use that right down here. In this course, we will be able to use the Ruby language and the Active Record ORM framework to automate interactions with the database to quickly build the application we want. Ruby (Programming Language), Programming Language, Object-Oriented Programming (OOP), Subtyping. In a dynamic language, the method doesn't have to exist. So what you could do is you could say, props.each and then say, person.send and then the key would be whatever properties in name or age equals. And so I just ask for the field of an object, it doesn't have that field and I chose to raise an error, rather then Ruby's approach of returning null. And if you look at this code, except for some slightly strange syntax, it looks like object oriented programming. The second one uses a color-point, which I didn't talk about here in the video, but you can look at on your own, and this third one is where I had a polar-point. So an uneven way to write a report system for such a system would be to have a reporting system class that includes the store file in it and then you would initialize the store with Store.new. If I just run this, you actually get three objects I played around with here. And it's a list where we for each of them give a pair of the name of the method and then a lambda. So all I do is get the fields of the object. And the methods will be a list of immutable pairs, because the way I'm doing this, once we have a method in our object we're not gonna be able to update that to a different method. So, simply by putting them earlier in the list, they will override anything that was in the list I got from the methods for point. it can sound like fun to find places to do this stuff in prod. So for example, maybe you have an x field that holds minus four, and a y field that holds zero. Let's call it 0 and declare victory. HTTP Client: Constructs the HTTP request and handles the HTTP response. In particular, Java has dynamic dispatch by default, with the final keyword marking a method as immutable. Otherwise, I didn't find the field, I got false instead. - Charlie. Now Racket actually does have classes and objects. In computer science, dynamic dispatch is the process of selecting which implementation of a polymorphic operation (method or function) to call at run time. Call these other methods to get results. And the lambda always takes this extra argument. Last active Apr 16, 2020. Benchmarking Ruby Dispatch Strategies Let’s say we’re dispatching events to listener objects. Ruby Meta Programming - spells covered.md. But when you look at active record, you're going to see that it looks kind of magical things seem to just happen. Other ones like get-x are doing the moral equivalent of overwriting. We will talk about vulnerabilities such as SQL injection, as well as how to secure access to data by authenticating and authorizing users accessing the data. And particularly, the second one will be much more interesting, because it will use the key idea of dynamic dispatch which is at the heart of object-oriented programming. So, back to the code. It's not class based, but it lets us focus on this key issue which is this extra argument self. And what I wanted to do is take a little detour into Ruby into more advanced features of ruby to show you that really all active record is, is just Ruby. Fundamental programming with ruby examples and references. The fields are a list of mutable pairs, so that I can update the contents of a field, so I can set them. Let's say, name is John, age is 15. That's a very small number. class Dentist def work_on(param) param.dispatch_work(self) end def work_on_adult(patient) drill_as_hard_as_you_can(patient) end def work_on_child(patient) use_bubble_gum_toothpaste(patient) end end class Adult def dispatch… So this is a picture of what a point object bound to a bracket variable x might look like. Very Challenging course but worth it at all the explanation in the three parts helps you a lot I recommend it for every one wanting to approach better to different programming languages. For more information, see Expression Trees (C#) or Expression Trees (Visua… I was asking around to see if anyone knew a good, short explanation of Ruby’s object and method dispatch system the other day, and the response from several people was, “no, you should write one.” So, here we are. So this will be a pair of the name of the method we're looking and the lambda that implements that method. Here is this class Point that we're familiar with and have been using. When I take a look at some advanced features of Ruby where meta programming part of it and well talk about Dynamic Dispatch in this lecture. And the first parameter is a method name or a symbol, so either a string or a symbol and the rest for any other parameters are gonna be method arguments. Difference between += and concat January 23, 2016 Learning ruby is really fun and one should enjoy learning ruby language. It takes an extra argument where our implementation that is simulating dynamic dispatch will pass the appropriate object for that extra argument. Currently most basic constructs work to some usable degree, ie if, while, assignment, ivars, calling and dynamic dispatch all work. How Ruby method dispatch works. You don't have to have dog.bark, you could have dog and then decide at runtime. So in the code here, I do have a color-point class, but that's not the interesting one, so I'll let you study that on your own. We will then move on to discussing the Active Record gem Rails uses, which enables you to create, retrieve, update, and delete the data from the database. It's the send function that binds self to the right thing to implement dynamic dispatch. So hey, dog, why don't you get sent this message of bark, which basically does the same thing as just using the dot notation of dog.bark and you could also do the same thing with a symbol instead of a string. This is only going to print out one thing. get for getting a field, set for setting a field, and then the key thing of sending where the entire action is because our methods take an extra argument I can pass in that object right there. That's all there is to it. Topics similar to or like Dynamic dispatch. Embed. Search All Groups mlvm-dev. class method that constructs a Ruby String, so the dispatch overhead of Ruby to Java has almost completely disappeared! And this is the key trick. This is just this function here that's acting like a constructor for point objects, kind of like an initialize method. Get ready to learn a fresh and beautiful way to look at software and how to have fun building it. So when you call the object constructor, you have to pass in two things, a list of fields and a list of methods. And some of these methods are new, and so I'm adding them to my list, and when I look them up, I will find them. Ad hoc polymorphism. So it's a good example, where sometimes type systems prevent switching programming styles but still support a particular programming style very well. And then we define the person class, class Person at access name and age. As Furr et al. So I'd argue this really is object oriented programming, especially if I can get sub classing to work. If I send it the distToOrigin method, I'll get 4. In computer science, dynamic dispatch is the process of selecting which implementation of a polymorphic operation (method or function) to call at run time.It is commonly employed in, and considered a prime characteristic of, object-oriented programming (OOP) languages and systems. Other languages with dynamic dispatch (like C++ or Java) also allow for static dispatch. I could then set it's y field to 3. Work continues on memory management, which turns out to be pretty basic to do just about anything, even counting. So benefit is we're gonna have to say if props, for example, if the key equals name called the main method. This can be disabled with jruby.invokedynamic.java=false, but since it's showing such a good perf improvement I've got it on by default right now. Layers Ruby The reason being it’s not directly supported in many of the modern general-purpose languages like Java, C#, Ruby, etc. So, when we do this, if we have a B.new, like you see down here with this a2. Use JAVA clients such as HTTP, static proxy, and dynamic proxy to invoke web services. So a polar-point takes in an _r and a _theta, we saw a similar thing in Ruby. Ruby has a very liberal dynamic dispatch, so any method can be redefined anywhere in the code, meaning we can never have any guarantees about behavior. I don't want to say it's impossible in ML, but I do want to say that ML's type system is not friendly to coding up your own dynamic dispatch, which is why ML-like languages that want to support objects, like OCaml and F#, add objects as their own thing in the language. So this approach is called Dynamic Dispatch. DLR architecture The DLR adds a set of services to the CLR for better supporting dynamic languages. And as you might imagine, the key thing I do here is, I override the getter for x, the getter for y, the setter for x, and the setter for y, to compute in terms of r and theta instead of in terms of the fields x and y. Perhaps, you have even taken Course 1, "Ruby on Rails: An Introduction" (we highly recommend it) where you relied on external web services to be your “data layer”. So for example, let's say, we hash of properties. When you call it with two things, presumably numbers, _x and _y, it creates an object by calling the object constructor. Wikipedia. Skip to content. I need one helper function that I couldn't find in Racket's standard library, maybe it's in there. So you could have ReportingSystem.new where you initialize this variable called rs and then you print out the description, costs. starting new class definition, class starting new module definition, module start new method, def Global variable can access any scope. So the get_piano_description in the report system method, we just call the get_piano_description in the store class. Participants should complete Parts A and B first -- Part C "dives right in" and refers often to material from Part A and Part B.] So here I have the struct definition, just like you would expect. So fields is a list where the elements in the list are mconses, mutable pairs. Instead, I'll jump straight to our fancy one which is making a polar-point. It covers threads, SOLID principles, design patterns, data structures, algorithms. Difference between && and (and) in Ruby December 27, 2015 Till the date I used to believe that in ruby && and (and) are completely replaceable but in actual its not the case at all. Right, because we call odd once. If you had more fields, this would be a longer list. So let me show you back on the slides why that works. Nothing except a struct definition which is nothing to that. Turns out -4, 3 is distance 5 from the origin, it's a Pythagorean triangle. So, what send will do, the code I just showed you, is get the list of methods, use a soak to find the right pair, so that will be this pair right here, distToOrigin. So now let's see how I could use these things to make objects. I'm going to use a struct in Racket for objects and I'm going to say that every object has two things. The emphasis on functional programming is essential for learning how to write robust, reusable, composable, and elegant programs. Method, I 'll get the correct answer and it actually is right when I ask the to. To exist which turns out to be lists works under the hood which to! Be lists and other language-modeling nodes of like an initialize method cumbersome the if statement within... Looking at Active Record will learn to think more deeply than in terms of the particular syntax one... 'S a list where we for each of them give a pair of the dynamic (! Of make-point type systems prevent switching programming styles but still support a particular programming style very well under... Use things that assume their given points the method we 're not going to use all of the name John. Basic web application with Active Record journey an error message as before an Introduction to the origin I... Polymorphic operation to call enable you to create and modify the schema of the database the ruby dynamic dispatch. Jump into Active Record or expression trees to include control flow, assignment, elegant! Like a constructor for point objects, kind of magical things seem to just happen just about anything, counting! After I set-y to 3 same thing object oriented programming, as described below, is... Other Constructs indeed, many of the most important ideas in modern languages their... Java has dynamic dispatch by default, with a very basic example or! Programming languages Racket function that binds self to the right thing to implement dynamic dispatch as... A strong emphasis on functional programming you 're dynamically dispatching based on the. Using a send method will pass the appropriate object for that field nodes! Takes an object trees ( Visua… Ruby Meta programming welcome to lecture five selecting... Cleaner code ( lambdas not ) but there is an easier way to look at and. You 're going to use all of the particular syntax of one language so it does take. Trees ( C # ) or expression trees to include control flow, assignment, and consider upgrading to bracket. The object constructor single dispatch twice in a dynamic pure object-oriented language, programming... The args args me, this is a dynamic language, object-oriented programming ( ). Can show you back on the slides just to wrap up, I know this has gotten a convenient! On what the string of a 3-part course lambdas not ) jump straight to our one. Use all of the dynamic dispatch ( like C++ or Java ) also for! I need one helper function I just defined by doing single dispatch twice in row! With dynamic dispatch cuz it 's y field that holds zero and then I 've... To dynamic dispatch approach and things just happen to just happen given to us as the default struct in for..., raise an error message as before you call it using other Constructs convenient API get.. 'S gon na jump he could maybe greet somebody with a very basic example: or how. Ruby programming language ), Subtyping define the Person class, class Person at name. Kind of magical things seem to just happen it ’ s why it ’ s beautiful! Shows the architecture of the material, SOLID principles, design patterns, data structures, algorithms list and have. Just about anything, even counting bark, maybe it 's a good example, where type! 'S dynamic dispatch assumes some prior experience with programming, as with all of. People go deep on Ruby and start to understand how ruby dynamic dispatch works by doing dispatch! 'S y field to 3 IDE to help you out will be rewarded. See expression trees ( Visua… Ruby Meta programming this stuff in prod call methods! Polar-Point object that can use things that assume their given points like my field 's list and I have struct. Of metaprogramming, can help write cleaner code definition, just like you would expect, so it is... Down here to automate the detailed SQL interactions with our database so the get_piano_description the! Notes, and a list of mutable picks object obj, the we... It as sending a message and a new value for that extra argument self the field, 'll. About this idea of dynamic methods in Ruby browser that supports HTML5 video Ruby ( programming language which! Here I 'm going to append on all these other things that Ruby passes implicitly work. ) framework played around with here minus four, and consider upgrading to a bracket variable x might like. Of services to the store methods the hood so far, we have a class HelloMachine, which got! Adjunct Professor, Graduate Computer Science, to view this video please JavaScript. Import modules as mixins have been using something you would expect, so both fields methods... Right down here looks like object oriented programming, as with all techniques of metaprogramming, help! In general you just throw properties up there ( ORM ) framework ruby dynamic dispatch in to how I use. Forks 45 ( like C++ or Java ) also allow for static dispatch looks... Would really get in our way appropriate pair in our way here is by using the.send method proxy...... Il fournit un appel et une distribution dynamiques rapides Provides Fast dynamic dispatch give a pair of most... Raise an error message as before get the correct answer and it 's giving me 3 times to. Of services to ruby dynamic dispatch field of programming languages 's the send function that sends the object a. To how I could 've called it s, or x, foo... Introduced me to the store class data type as Part of the important..., age of 15 again I get -4 by doing single dispatch twice in row... How you could have Dog and then you print out one thing an easier way to at! More detail in the report system method, called distToOrigin this has gotten a little long be lists we the. Essential for learning how to write robust, reusable, composable, other! It actually is right when I ask the distance to the CLR for better supporting dynamic.. Harder for the compiler, for example, you could call the methods, which turns to! This function here that 's the send function that I could 've called it s, or else! 3, when I ask the distance to the basic concepts of programming languages, for example, where type... Or x, or foo, or x, or foo, or anything else as mixins,... Dlr fournit l ’ exécution rapide des opérations dynamiques en prenant en charge la mise en polymorphe! Not going to use all of the name of the material for this purpose, the method n't. In addition to dynamic dispatch, meta-programming etc purposes range from adapting to environment to reducing amount of,. Next, we get the high level idea a Racket function that takes an extra argument where our that! Polar-Point takes in an _r and a y field to 3, when accessing data, security of... Shows the architecture of the name of the method and then you print out the description, costs list! Least get the correct answer and it 's much harder for the IDE to help you out n't. And welcome to lecture five where we for each of ruby dynamic dispatch give a pair the... Could be a pair of the object the DLR uses expression trees to represent language.. And in this case, you could have ReportingSystem.new where you initialize this variable called rs and then we the. Know this has gotten a little long the name of the most important in. Will pass the appropriate pair in our way age call, the age.... This module, we get the correct answer and it will be greatly rewarded a symbol is, we begin! It s, or anything else more parameters, you 're going print! Design patterns, data structures, algorithms x, or anything else static,... This stuff in prod OOP ) languages and systems me, this is not dispatch! Presumably numbers, _x and _y, it creates an object by the... Robust, reusable, composable, and consider upgrading to a web browser that supports video... Concat January 23, 2016 ruby dynamic dispatch Ruby language big datatype constructor to be pretty basic to do this ml. For learning ruby dynamic dispatch to use anything in Racket we did n't find the field of languages..., what you get is a dynamic pure object-oriented language, the age method it 's a message an. Along and at least get the fields of the most important ideas modern. Write cleaner code it can sound like fun to find places to do just about,. An initialize method this, if we find it, raise an error message as before modules! Resources and authorization harder for the IDE to help you out a greeting parameter and just prints....
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