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• Web framework able to handle many concurrent users [closed]

  - by Jonas

  Social networking sites needs to handle many concurrent users e.g. for chat functionality. What web frameworks scales well and are able to handle more than 10.000 concurrent users connected with Comet or WebSockets. The server is a Linux VPS with limited memory, e.g. 1GB-8GB. I have been looking for some Java frameworks but they consume much memory per connection. So I'm looking for other alternatives too. Are there any good frameworks that are able to handle more than 10.000 concurrent users with limited memory resources?

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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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• Project Idea - Android

  - by Darren Young

  Hi, I am trying to come up with some project ideas for my final year at University, and I think that I have one that would offer be a (massive) challenge, and something I could potentially make money from. I just want to check something. Is it possible(from a photograph), to be able to determine somebodys face and the individual parts of that face - eyes, ears, nose, etc? This will probably be via Android. Thanks.

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• Purpose of "new" keyword

  - by Channel72

  The new keyword in languages like Java, Javascript, and C# creates a new instance of a class. This syntax seems to have been inherited from C++, where new is used specifically to allocate a new instance of a class on the heap, and return a pointer to the new instance. In C++, this is not the only way to construct an object. You can also construct an object on the stack, without using new - and in fact, this way of constructing objects is much more common in C++. So, coming from a C++ background, the new keyword in languages like Java, Javascript, and C# seemed natural and obvious to me. Then I started to learn Python, which doesn't have the new keyword. In Python, an instance is constructed simply by calling the constructor, like: f = Foo() At first, this seemed a bit off to me, until it occurred to me that there's no reason for Python to have new, because everything is an object so there's no need to disambiguate between various constructor syntaxes. But then I thought - what's really the point of new in Java? Why should we say Object o = new Object();? Why not just Object o = Object();? In C++ there's definitely a need for new, since we need to distinguish between allocating on the heap and allocating on the stack, but in Java all objects are constructed on the heap, so why even have the new keyword? The same question could be asked for Javascript. In C#, which I'm much less familiar with, I think new may have some purpose in terms of distinguishing between object types and value types, but I'm not sure. Regardless, it seems to me that many languages which came after C++ simply "inherited" the new keyword - without really needing it. It's almost like a vestigial keyword. We don't seem to need it for any reason, and yet it's there. Question: Am I correct about this? Or is there some compelling reason that new needs to be in C++-inspired memory-managed languages like Java, Javascript and C#?

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• History of open source software

  - by Victor Sorokin

  I've been always interested, out of the pure self-amusement, in the history of open software used today: who were the people which started it and what were the reasons to start what were design decisions at the start how software evolved over the time Specifically, I'm interested in following software: GCC X Linux kernel Java Of course, there is plenty of information in Internet to google for, but I thought it would be nice to have list of interesting resources at this site. I hope some of visitors of this site have similar interest and can share a link or two they found particularly amusing/interesting. To make this entry more question-like, here's straight question: what are the most interesting/amusing links about history of open source software?

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• Finding a way to simplify complex queries on legacy application

  - by glenatron

  I am working with an existing application built on Rails 3.1/MySql with much of the work taking place in a JavaScript interface, although the actual platforms are not tremendously relevant here, except in that they give context. The application is powerful, handles a reasonable amount of data and works well. As the number of customers using it and the complexity of the projects they create increases, however, we are starting to run into a few performance problems. As far as I can tell, the source of these problems is that the data represents a tree and it is very hard for ActiveRecord to deterministically know what data it should be retrieving. My model has many relationships like this: Project has_many Nodes has_many GlobalConditions Node has_one Parent has_many Nodes has_many WeightingFactors through NodeFactors has_many Tags through NodeTags GlobalCondition has_many Nodes ( referenced by Id, rather than replicating tree ) WeightingFactor has_many Nodes through NodeFactors Tag has_many Nodes through NodeTags The whole system has something in the region of thirty types which optionally hang off one or many nodes in the tree. My question is: What can I do to retrieve and construct this data faster? Having worked a lot with .Net, if I was in a similar situation there, I would look at building up a Stored Procedure to pull everything out of the database in one go but I would prefer to keep my logic in the application and from what I can tell it would be hard to take the queried data and build ActiveRecord objects from it without losing their integrity, which would cause more problems than it solves. It has also occurred to me that I could bunch the data up and send some of it across asynchronously, which would not improve performance but would improve the user perception of performance. However if sections of the data appeared after page load that could also be quite confusing. I am wondering whether it would be a useful strategy to make everything aware of it's parent project, so that one could pull all the records for that project and then build up the relationships later, but given the ubiquity of complex trees in day to day programming life I wouldn't be surprised if there were some better design patterns or standard approaches to this type of situation that I am not well versed in.

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• What is the convention for the star location in reference variables?

  - by Brett Ryan

  Have been learning Objective-C and different books and examples use differing conventions for the location of the star (*) when naming reference variables. MyType* x; MyType *y; MyType*z; // this also works Personally I prefer the first option as it illustrates that x is a "pointer type of MyType". I see the first two used interchangeably, and sometimes in the same code I've seen differing uses of both. I want to know what is the most common convention It's been a very long time since I've programmed in C (15 years) so I can't remember if all variants are legal for C also or if this is Objective-C specific. I'd prefer answers which state why one is better than the other, as how I explained how I read it above.

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• Is an 'if password == XXXXXXX' enough for minimum security?

  - by Morgan Herlocker

  If I create a login for an app that has middle to low security risk (in other words, its not a banking app or anything), is it acceptable for me to verify a password entered by the user by just saying something like: if(enteredPassword == verifiedPassword) SendToRestrictedArea(); else DisplayPasswordUnknownMessage(); It seems to easy to be effective, but I certainly would not mind if that was all that was required. Is a simple check on username/password combo enough? Update: The particular project happens to be a web service, the verification is entirely server side, and it is not open-source. Does the domain change how you would deal with this?

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• How do we keep dependent data structures up to date?

  - by Geo

  Suppose you have a parse tree, an abstract syntax tree, and a control flow graph, each one logically derived from the one before. In principle it is easy to construct each graph given the parse tree, but how can we manage the complexity of updating the graphs when the parse tree is modified? We know exactly how the tree has been modified, but how can the change be propagated to the other trees in a way that doesn't become difficult to manage? Naturally the dependent graph can be updated by simply reconstructing it from scratch every time the first graph changes, but then there would be no way of knowing the details of the changes in the dependent graph. I currently have four ways to attempt to solve this problem, but each one has difficulties. Nodes of the dependent tree each observe the relevant nodes of the original tree, updating themselves and the observer lists of original tree nodes as necessary. The conceptual complexity of this can become daunting. Each node of the original tree has a list of the dependent tree nodes that specifically depend upon it, and when the node changes it sets a flag on the dependent nodes to mark them as dirty, including the parents of the dependent nodes all the way down to the root. After each change we run an algorithm that is much like the algorithm for constructing the dependent graph from scratch, but it skips over any clean node and reconstructs each dirty node, keeping track of whether the reconstructed node is actually different from the dirty node. This can also get tricky. We can represent the logical connection between the original graph and the dependent graph as a data structure, like a list of constraints, perhaps designed using a declarative language. When the original graph changes we need only scan the list to discover which constraints are violated and how the dependent tree needs to change to correct the violation, all encoded as data. We can reconstruct the dependent graph from scratch as though there were no existing dependent graph, and then compare the existing graph and the new graph to discover how it has changed. I'm sure this is the easiest way because I know there are algorithms available for detecting differences, but they are all quite computationally expensive and in principle it seems unnecessary so I'm deliberately avoiding this option. What is the right way to deal with these sorts of problems? Surely there must be a design pattern that makes this whole thing almost easy. It would be nice to have a good solution for every problem of this general description. Does this class of problem have a name?

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• Using an actor model versus a producer-consumer model?

  - by hewhocutsdown

  I'm doing some early-stage research towards architecting a new software application. Concurrency and multithreading will likely play a significant part, so I've been reading up on the various topics. The producer-consumer model, at least how it is expressed in Java, has some surface similarities but appears to be deeply dissimilar to the actor model in use with languages such as Erlang and Scala. I'm having trouble finding any good comparative data, or specific reasons to use or avoid the one or the other. Is the actor model even possible with Java or C#, or do you have do use one of the languages built for the purpose? Is there a third way?

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• Good resources for language design

  - by Aaron Digulla

  There are lots of books about good web design, UI design, etc. With the advent of Xtext, it's very simple to write your own language. What are good books and resources about language design? I'm not looking for a book about compiler building (like the dragon book) but something that answers: How to create a grammar that is forgiving (like adding optional trailing commas)? Which grammar patterns cause problems for users of a language? How create a compact grammar without introducing ambiguities

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• How do software projects go over budget and under-deliver?

  - by Carlos

  I've come across this story quite a few times here in the UK: NHS Computer System Summary: We're spunking £12 Billion on some health software with barely anything working. I was sitting the office discussing this with my colleagues, and we had a little think about. From what I can see, all the NHS needs is a database + middle tier of drugs/hospitals/patients/prescriptions objects, and various GUIs for doctors and nurses to look at. You'd also need to think about security and scalability. And you'd need to sit around a hospital/pharmacy/GPs office for a bit to figure out what they need. But, all told, I'd say I could knock together something with that kind of structure in a couple of days, and maybe throw in a month or two to make it work in scale. * If I had a few million quid, I could probably hire some really excellent designers to make a maintainable codebase, and also buy appropriate hardware to run the system on. I hate to trivialize something that seems to have caused to much trouble, but to me it looks like just a big distributed CRUD + UI system. So how on earth did this project bloat to £12B without producing much useful software? As I don't think the software sounds so complicated, I can only imagine that something about how it was organised caused this mess. Is it outsourcing that's the problem? Is it not getting the software designers to understand the medical business that caused it? What are your experiences with projects gone over budget, under delivered? What are best practices for large projects? Have you ever worked on such a project? EDIT *This bit seemed to get a lot of attention. What I mean is I could probably do this for say, 30 users, spending a few tens of thousands of pounds. I'm not including stuff I don't know about the medical industry and government, but I think most people who've been around programming are familiar with that kind of database/front end kind of design. My point is the NHS project looks like a BIG version of this, with bells and whistles, notably security. But surely a budget millions of times larger than mine could provide this?

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• Need explanation of hexagonal architecture

  - by Victor Grazi

  I am reading about Alistair Cockburn's Hexagonal Architecture http://alistair.cockburn.us/Hexagonal+architecture with interest. One claim he makes is: "Finally, the automated function regression tests detect any violation of the promise to keep business logic out of the presentation layer. The organization can detect, and then correct, the logic leak." I do not understand this point. Is he saying that because the test is headless, then calls to a ui layer will throw exceptions? That doesn't seem to be a very sound test!

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• what are the advantages and disadvantages of putting code for an unfinished project on github

  - by cori

  I'm stating to work on a project that I intend to release as open source via the githubs. What are the advantages of putting the code on github from the outset, as opposed to waiting until the project is in a working state before publishing. If it matters, this particular project is a C# app/service, and I have only a free github account (so I can't make it private and then pull back the covers later)

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• Why don't we just fix Javascript?

  - by Jan Meyer

  Javascript sucks because of a few fatalities well pointed out by Douglas Crockford. We talk a lot about it. But the point here is, why we don't fix it? Coffeescript of course does that and a lot more. But the question here is another: if we provide a webservice that can convert one version of Javascript to the next, and so on, we can keep the language up to date. Such a conversion allows old code to run, albeit with an ever-increasing startup delay, as newer browsers convert old code to the new syntax. To avoid that delay, the site only needs to take the output of the code-transform and paste it in! The effort has immediate benefits for those businesses interested in the results. The rest can sleep tight: their code will continue to run. If we provide backward code-transformation also, then elder browsers can also run ANY new code! Migration scripts should be created by those that make changes to a language. Today they don't, which is in itself a fundamental omission! It should be am obvious part of their job to provide them, as their job isn't really done without them. The onus of making it work should be on them. With this system Any site will be able to run in Any browser, but new code will run best on the newest browsers. This way we reap the benefit of an up-to-date and productive development environment, where today we suffer, supposedly because of yesterday. This is a misconception. We are all trapped in committee-thinking, and we drag along things that only worsen our performance over time! We cause an ever increasing complexity that is hard to underestimate. Javascript is easily fixed. The fact is we don't. As an example, I have seen Patrick Michaud tackle the migration problem in PmWiki. It included forward migration scripts. Whenever syntax changes were made, a migration script was added to transform pages to the new syntax. As far as I know, ALL migrations have worked flawlessly. In other words, we don't tackle the migration problem, we just drag it along. We are incompetent! And why is that? Because technically incompetent people feel they must decide for us. Because they are incompetent, fear rules them. They are obnoxiously conservative, and we suffer the consequence of bad leadership. But the competent don't need to play by the same rules. They can (and must) change them. They are the path forward. It is about time to leave the past behind, and pursue the leanest meanest, no, eternal functionality. That would in and of itself revolutionize programming. So, why don't we stop whining and fix programming? Begin with Javascript and change the world. Even if the browser doesn't hook into this system, coders could. So language updaters should take it upon them to provide migration scripts. Once they exist, browsers may take advantage of them.

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• Do certain corporations hold more weight on a resume?

  - by Ryan

  Would a developer/tester position at Google, Apple, Microsoft, etc. (any large tech. company of which most people have heard) be more valuable on a resume than working as a developer/tester somewhere where tech. isn't the main objective (shipping company, restaurant chain, insurance company, etc.)? Let's say you have two offers, and you only plan to stay with whichever company for 5 years, before trying to get a better position at a different company. One at Google that has a starting salary of $60,000, and one at some insurance company that has a starting salary of $80,000. I guess what I'm trying to say is... with university's, if someone graduates from MIT or Carnegie Mellon, they can pretty much get a job anywhere. Does someone seem more valuable after having worked at a company like Google, Apple, Microsoft, etc.? In other words, would taking the lower paying job be better in the long run since it's at Google, or would it be better to take the higher paying job at the insurance company?

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• Not getting paid for hours you've worked?

  - by Mercfh

  So I was reading from a previous thread about App vs Game Development Here Which brought me to this site: Clicky Alot of it talked about devs working something like 85 hours a week.....and not getting paid overtime, or anything. Just getting paid for the 40 hours.....Is this normal for most software companies? I mean where I work im only an entry level guy....but I get overtime, and Anything over 40 hours is considered this. But it got me thinking "Holy crap" I could never do that. My FREE time is important to me. But is this commonplace in most software companies? or...more a rarity to certain types (game development, etc) Cause it got me scared! Like I understand having to put some extra hours in for a project......but like 80! thats ridiculous.

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• Learning the GO programming language and its prospects [closed]

  - by SHOUBHIK BOSE

  Possible Duplicate: What are the chances of Google's Go becoming a mainstream language? Recently I've started experimenting with The GO programming language by Google. Its a programmer-friendly language having the simplicity of Python. I was wondering whether companies other than Google would also start using Go for development, and if they do , what would be the prospects of being a Go programmer?

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• Social IT guy barrier [closed]

  - by sergiol

  Possible Duplicate: How do you deal with people who ask you to fix their computer? Hello. Almost every person that deserves the title of being a programmer as faced the problem of persons that do not even remember the mere existence of those professionals, unless they have serious problems in their computer or some other IT related problem. May be my post will be considered off-topic, but I think it is a very important question. As Joel Spolsky says, IT guys are not Asperger geeks, and they need social life like everybody. But the people that is always asking for favors from us, can ruin deeply our social and personal life. I could experience this by myself. This fact as generated articles like http://www.lifereboot.com/2007/10-reasons-it-doesnt-pay-to-be-the-computer-guy/ and http://ecraazul.wordpress.com/2009/01/29/o-gajo-da-informatica-de-a-a-z/ (I received this one in my mailbox. It is in Portuguese, but I believe it is translated from English). Basically the idea is to criticize people that is always asking us favors. It is even more annoying if you are person very specialized in some subject and a person asks you a completely out-of-that-context question. For example, you are a VBA programmer and somebody says you to that his/her Mobile Internet Pen stopped to work five days ago and needs your help to put it working again. When you go to a doctor to fix your legs, you don't go to an ophthalmologist. You go to an orthopedist. And you pay. I don't how it works in other countries, but in Portugal being a doctor is so an overvalued job, that they earn very much money and almost nobody asks them free favors. So, my question is: what kind of social barrier (or whatever else) do you use to protect yourself from that situation?

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• Why does this static field always get initialized over-eagerly?

  - by TheSilverBullet

  I am looking at this excellent article from Jon Skeet. While executing the demo code, Jon Skeet says that we can expect three different kinds of behaviours. To quote that article: The runtime could decide to run the type initializer on loading the assembly to start with... Or perhaps it will run it when the static method is first run... Or even wait until the field is first accessed... When I try this out (on framework 4), I always get the first result. That is, the static method is initialized before the assembly is loaded. I have tried running this multiple times and get the same result. (I tried both the debug and release versions) Why is this so? Am I missing something?

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• blurry lines between web application context layer, service layer and data access layer in spring

  - by thenaglecode

  I Originally asked this question in SO but on advice I have moved the question here... I'll admit I'm a spring newbie, but you can correct me if I'm wrong, this one liner looks kinda fishy in a best practices sort of way: @RepositoryRestResource(collectionResourceRel="people"...) public interface PersonRepository extends PagingAndSortingRepository<Person, Long> For those who are unaware, the following does many things: It is an interface definition that can be registered in an application context as a jpa repository, automagically hooking up all the default CRUD operations within a persistence context (that is externally configured). and also configures default controller/request-mapping/handler functionality at the namespace "/people" relative to your configured dispatcher servlet-mapping. Here's my point. I just crossed 3 conceptual layers with one line of code! this feels against my seperation-of-concern instincts but i wanted to hear your opinion. And for the sake of being on a question and answer site, I would like to know whether there is a better way of seperating these different layers - Service, Data, Controllers - whilst maintaining as minimal configuration as possible

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• CMS vs Admin Panel?

  - by Bob

  Okay, so this probably seems like an unusual, more grammar related question, but I was unsure of what to call it. If you use a software such as vBulletin or MyBB or even Blogger and you're the administrator (or other, lesser position such as moderator) of the forum, or publisher/author of the blog, you generally have access to something of an "admin panel". For example, vBulletin's admin panel looks like this and Blogger's admin panel looks something like this. While they both look different and do different things, the goal is fundamentally the same: to provide the user with a method for adding, modifying, or deleting content... to let them control and administrate their forum or blog. Also, they're both made specifically by the company for use in a specific product. Now, there's also options like Drupal. It seems to offer quite a bit more and be quite a bit more generalized. How does something like this work? If you were freelancing, would you deploy a website with Drupal, or would it be something the client might already have installed on their own server? I've never really used Drupal, only heard about it, so please let me know. Also, there seems to be other options like cPanel, a sort of global CMS that allows you to administrate over your entire website. How do those work in comparison to Drupal, or the administrative panels with vBulletin? They seem to serve related, but different purposes. Basically, what is the norm? If I'm developing a web application for a group that needs to be able to edit their website without the need to go into the code or the database (or rather, wants to act in a graphical, easy-to-use content-management/admin panel), would it also be necessary to write my own miniature admin panel? Or would I be able to send them off knowing that they have cPanel? Or could something like Drupal fill this void? Again, I'm a little new to web development, and I'm working on planning out my first, real, large website. So I need a little advice on the standards and expectations for web development - security and coding practices aside, what should I be looking for as far as usability and administration for the client (who will be running the site once I'm done creating the website)? Any extra tips would also be appreciated! Oh, and just a little bit: I'm writing the website using Ruby on the Sinatra framework (both Ruby and Sinatra are things I'm fairly comfortable with) and I'm not being paid to make the website (and I will also be a user, and one of the three administrators of the website) - it's being built for a club I'm in.

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• What are the arguments against parsing the Cthulhu way?

  - by smarmy53

  I have been assigned the task of implementing a Domain Specific Language for a tool that may become quite important for the company. The language is simple but not trivial, it already allows nested loops, string concatenation, etc. and it is practically sure that other constructs will be added as the project advances. I know by experience that writing a lexer/parser by hand -unless the grammar is trivial- is a time consuming and error prone process. So I was left with two options: a parser generator à la yacc or a combinator library like Parsec. The former was good as well but I picked the latter for various reasons, and implemented the solution in a functional language. The result is pretty spectacular to my eyes, the code is very concise, elegant and readable/fluent. I concede it may look a bit weird if you never programmed in anything other than java/c#, but then this would be true of anything not written in java/c#. At some point however, I've been literally attacked by a co-worker. After a quick glance at my screen he declared that the code is uncomprehensible and that I should not reinvent parsing but just use a stack and String.Split like everybody does. He made a lot of noise, and I could not convince him, partially because I've been taken by surprise and had no clear explanation, partially because his opinion was immutable (no pun intended). I even offered to explain him the language, but to no avail. I'm positive the discussion is going to re-surface in front of management, so I'm preparing some solid arguments. These are the first few reasons that come to my mind to avoid a String.Split-based solution: you need lot of ifs to handle special cases and things quickly spiral out of control lots of hardcoded array indexes makes maintenance painful extremely difficult to handle things like a function call as a method argument (ex. add( (add a, b), c) very difficult to provide meaningful error messages in case of syntax errors (very likely to happen) I'm all for simplicity, clarity and avoiding unnecessary smart-cryptic stuff, but I also believe it's a mistake to dumb down every part of the codebase so that even a burger flipper can understand it. It's the same argument I hear for not using interfaces, not adopting separation of concerns, copying-pasting code around, etc. A minimum of technical competence and willingness to learn is required to work on a software project after all. (I won't use this argument as it will probably sound offensive, and starting a war is not going to help anybody) What are your favorite arguments against parsing the Cthulhu way?* *of course if you can convince me he's right I'll be perfectly happy as well

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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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• What would be the best approach to make revisions of user content?

  - by Kevin Simper

  I have searched and could not find any information about it. What is the best approach to storing revisions? I have a website where the user can write a document which can be fairly long (200-300 lines). How do you determine when to make a revision? Is it not a scalable solution to make a new one whenever the save, because that would be useless to the user when the want to look back, and it would require quite a lot of space. You could use time and say for every 15 minute they are working on it there would be a revision, but that would sometimes be nothing or the whole document have completely changed. I could make a diff from the previous revision, and compare by line and look at how many percent of the lines have been changed. What are other doing revisions?

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