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• Cloud service and IM protocol advice, for a backend to group chat mobile app

  - by Jonathan

  Overview I’m going to develop an app on Android and iOS. It will allow users to set up group ‘chat rooms’ and talk on chat rooms set up by other users. The service needs to be highly scalable, such that it could accommodate a massive increase in users overnight (we can only dream). Chat requirements The chat protocol used should be flexible: it should allow me to determine who can view/post on ‘chat rooms’ based on certain other factors, as determined by the first poster/creator of the particular ‘chat room’. It should also allow for users to simply install the app and begin using the service, after only providing a simple nickname (which could be changed later). Chat protocol plans Having looked around I think the XMPP protocol is the best candidate. In particular the Multi-user chat extension looks like what I’ll need. Would this be most suited to my requirements, or do you know another potential solution? Cloud service I have been deciding between Amazon Web Services, Google App Engine and Windows Azure. I’m coming to the conclusion that Azure will be best, as it is easier to manage than AWS (ease of scalability will be a key factor in the design), I think it may be less restricted than GAE, plus Azure will soon have toolkits to allow easy interfacing with both Android and iOS phones. Is this the decision you would have made, or would you recommend/look into other cloud services? General project philosophy I have only recently started looking into this project’s feasibility, and am no expert on any of its aspects. So wherever possible I will leave the actual implementations to experts, i.e. choosing a higher-level cloud service, using a well-documented plugin of a, proven reliable, group chat protocol etc. My background I have some programming knowledge from a computer science degree. Main languages I’ve used have been Java and Python, but I don’t want this to affect design decisions for the project. The most appropriate languages for the task should be used, i.e. I don’t mind learning a lot of new skills (my current programming levels are relatively basic anyway). Thank you Thanks for reading, and any advice you have about any aspect would be greatly appreciated :-)

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• Software cost estimation

  - by David Conde

  I've seen on my work place (a University) most students making the software estimation cost of their final diploma work using COCOMO. My guessing is that this way of estimating costs is somewhat old (COCOMO dates of 1981), hence my question: How do you estimate costs in your software? I've seen things like : Cost = ( HoursOfWork + EstimatedIddle ) * HourlyRate That's not what I want, I'm looking for a properly (scientifically) defined cost model EDIT I've found some related questions on SO: What are some of the software cost estimation methods and models? How do you estimate the cost of developing software requirements?

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• Version control implementation advice on legacy websites?

  - by Eric

  Assuming no experience with version control systems, just local to live web development. I've been dropped in on a few legacy website projects, and want an easier and more robust way to be able to quickly push and revert changes en masse. I'm currently the only developer on these projects, but more may be added in the future and I think it would be beneficial to set up a system that others can use.

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• What's the problem with Scala's XML literals?

  - by Oak

  In this post, Martin (the language's head honcho) writes: [XML literals] Seemed a great idea at the time, now it sticks out like a sore thumb. I believe with the new string interpolation scheme we will be able to put all of XML processing in the libraries, which should be a big win. Being interested in language design myself, I'm wondering: Why does he write that it was a mistake to incorporate XML literals into the language? What is the controversy regarding this feature?

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• Popular programming books which have been translated into Russian

  - by arikfr

  I'm looking for recommendations of popular programming books that have been translated into Russian. I'm talking about books like: Test-Driven Development by Example by Kent Beck Code Complete The Pragmatic Programmer And other books like them. Also, recommendations for books in Russian by other authors but about similar topics (TDD, BDD, general programming methodologies) will be appreciated.

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• Are all languages basically the same?

  - by Anirudh

  Recently, i had to understand the design of a small program written in a language i had no idea about (ABAP, if you must know). I could figure it out without too much difficulty. I realize that mastering a new language is a completely different ball game, but purely understanding the intent of code (specifically production standard code, which is not necessarily complex) in any language is straight forward, if you already know a couple of languages (preferably one procedural/OO and one functional). Is this generally true? Are all programming languages made up of similar constructs like loops, conditional statements and message passing between functions? Are there non-esoteric languages that a typical Java/Ruby/Haskell programmer would not be able to make sense of? Do all languages have a common origin?

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• What are the typical applications of Lisp macros?

  - by Giorgio

  I am trying to learn some LISP and I have read a lot about the importance of LISP macros so I would like to get some working experience with them. Can you suggest a practical application area that would allow me to use macros to solve a real-world problem, and to understand the usefulness of this programming construct? NOTE This is not a generic what project should I do next question. I am interested to understand which kinds of problems are typically solved by means of LISP macros. E.g., are they good for implementing abstract data types? Why was this construct added to the language? What kinds of problems does it solve that cannot be solved by means of simple functions?

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• TBXML parsing issue while the value cannot get in UILabel

  - by Dany

  In my app I'm using TBXML parser where I need to get a value from xml file and print it on the label. This is my xml file in server <gold> <price> <title>22 K Gold</title> </price> <price> <title>24 K Gold</title> </price> </gold> any my Viewcontroller.h looks like #import <UIKit/UIKit.h> #import "TBXML.h" @interface ViewController : UIViewController{ IBOutlet UILabel *lab; IBOutlet UILabel *lab1; TBXML *tbxml; } @end and my Viewcontrooler.m looks like - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. NSData *xmlData = [[NSData alloc]initWithContentsOfURL:[NSURL URLWithString:@"http://www.abcde.com/sample.xml"]]; tbxml = [[TBXML alloc]initWithXMLData:xmlData]; TBXMLElement * root = tbxml.rootXMLElement; if (root) { TBXMLElement * elem_PLANT = [TBXML childElementNamed:@"price" parentElement:root]; while (elem_PLANT !=nil) { TBXMLElement * elem_BOTANICAL = [TBXML childElementNamed:@"title" parentElement:elem_PLANT]; NSString *botanicalName = [TBXML textForElement:elem_BOTANICAL]; lab.text=[NSString stringWithFormat:@"re %@", botanicalName]; elem_PLANT = [TBXML nextSiblingNamed:@"price" searchFromElement:elem_PLANT]; elem_BOTANICAL = [TBXML childElementNamed:@"title" parentElement:elem_PLANT]; botanicalName = [TBXML textForElement:elem_BOTANICAL]; lab1.text=[NSString stringWithFormat:@"re %@", botanicalName]; } } } I'm getting BAD_ACCESS thread. Am I missing anything?

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• Can I migrate a clone of Google Code repository into Github?

  - by David Conde

  I want to create a clone of a Google Code repository, which I cannot download due to Country restrictions and I want to migrate that clone into Github, which I can use without any problem. The thing is I have a Github account and I can browse through GoogleCode but I cannot take my TortoiseHg and clone a repo just like that because I'm from Cuba and I get a lovely Google page saying that I cannot go into Google code. I'm guessing you know how I manage to browse :) I would like to import a mercurial repository into my Github repo, my questions: Is it possible? How can I do it?

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• In a multidisciplicary team, how much should each member's skills overlap?

  - by spade78

  I've been working in embedded software development for this small startup and our team is pretty small: about 3-4 people. We're responsible for all engineering which involves an RF device controlled by an embedded microcontroller that connects to a PC host which runs some sort of data collection and analysis software. I have come to develop these two guidelines when I work with my colleagues: Define a clear separation of responsibilities and make sure each person's contribution to the final product doesn't overlap. Don't assume your colleagues know everything about their responsibilities. I assume there is some sort of technology that I will need to be competent at to properly interface with the work of my colleagues. The first point is pretty easy for us. I do firmware, one guy does the RF, another does the PC software, and the last does the DSP work. Nothing overlaps in terms of two people's work being mixed into the final product. For that to happen, one guy has to hand off work to another guy who will vet it and integrate it himself. The second point is the heart of my question. I've learned the hard way not to trust the knowledge of my colleagues absolutley no matter how many years experience they claim to have. At least not until they've demonstrated it to me a couple of times. So given that whenever I develop a piece of firmware, if it interfaces with some technology that I don't know then I'll try to learn it and develop a piece of test code that helps me understand what they're doing. That way if my piece of the product comes into conflict with another piece then I have some knowledge about possible causes. For example, the PC guy has started implementing his GUI's in .NET WPF (C#) and using LibUSBdotNET for USB access. So I've been learning C# and the .NET USB library that he uses and I build a little console app to help me understand how that USB library works. Now all this takes extra time and energy but I feel it's justified as it gives me a foothold to confront integration problems. Also I like learning this new stuff so I don't mind. On the other hand I can see how this can turn into a time synch for work that won't make it into the final product and may never turn into a problem. So how much experience/skills overlap do you expect in your teammates relative to your own skills? Does this issue go away as the teams get bigger and more diverse?

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• Objected oriented approach to structure inside structure

  - by RishiD

  This is for C++ but should apply to any OO language. Trying to figure out the correct object oriented apporach to do the following (this is what I do in C). struct Container { enum type; union { TypeA a; TypeB b; }; } The type field determines if it TypeA or TypeB object. I am using this to handle responses coming back from a connection, they get parsed and get put into this structure and then based on the message type the appropriate fields get filled in. e.g. struct Container parseResponse(bufferIn, bufferLength); Is there an OO approach for doing this?

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• Why isn't Japanese software industry as strong as their hardware technology?

  - by Joan Venge

  I admire Japanese technology and their innovation. They always seem to be one step ahead of everyone else. But why isn't their software industry just as developed? Why aren't there any Japanese operating systems, high-end game engines, 3D digital content creation applications? I would like to see their take on these and I think it could bring alot of innovation. Btw I mentioned 3D software because the animation industry is strong there as well, but they are using North American software for this.

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• Why is using C++ libraries is so complicated?

  - by Pius

  First of all, I want to note I love C++ and I'm one of those people who thinks it is easier to code in C++ than Java. Except for one tiny thing: libraries. In Java you can simply add some jar to the build path and you're done. In C++ you usually have to set multiple paths for the header files and the library itself. In some cases, you even have to use special build flags. I have mainly used Visual Studio, Code Blocks and no IDE at all. All 3 options do not differ much when talking about using external libraries. I wonder why was there made no simpler alternative for this? Like having a special .zip file that has everything you need in one place so the IDE can do all the work for you setting up the build flags. Is there any technical barrier for this?

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• Help me get started in TDD for web development

  - by Snow_Mac

  I've done a tiny, tiny bit of TDD in building an app for a company that I interned with. We used lots of mocking and wrote lots of assert statements, after reading lots of blogs, I'm convinced that TDD is the way to go, but how do you go about TDD web applications? My main framework is Yii in PHP. My main questions are: What do you test? Models? Controllers? Views? How do you know if the output is correct? All my web apps interact with a DB, are there cavets to that and gotchas? Can I do testing in Netbeans? Can you test form elements or just strictly objects & methods?

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• How to estimate freight / shipping costs ??

  - by Vani

  Hi, I am working on a PHP web application and want to know the best way to estimate freight costs in USA. The site deals with construction materials that uses LTL or Truck loads. I found a few sites like www.freightCenter.com that provide quotes using webservice. Two drawbacks, its paid service and the other, my site response time is slow if I use the webservice. Is there a open source tool/logic avaliable for estimating shipping / freight costs?? Or a way to determine the rate per mile per pound for different freight classes? Thank you, Vani

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• Decorator not calling the decorated instance - alternative design needed

  - by Daniel Hilgarth

  Assume I have a simple interface for translating text (sample code in C#): public interface ITranslationService { string GetTranslation(string key, CultureInfo targetLanguage); // some other methods... } A first simple implementation of this interface already exists and simply goes to the database for every method call. Assuming a UI that is being translated at start up this results in one database call per control. To improve this, I want to add the following behavior: As soon as a request for one language comes in, fetch all translations from this language and cache them. All translation requests are served from the cache. I thought about implementing this new behavior as a decorator, because all other methods of that interface implemented by the decorater would simple delegate to the decorated instance. However, the implementation of GetTranslation wouldn't use GetTranslation of the decorated instance at all to get all translations of a certain language. It would fire its own query against the database. This breaks the decorator pattern, because every functionality provided by the decorated instance is simply skipped. This becomes a real problem if there are other decorators involved. My understanding is that a Decorator should be additive. In this case however, the decorator is replacing the behavior of the decorated instance. I can't really think of a nice solution for this - how would you solve it? Everything is allowed, even a complete re-design of ITranslationService itself.

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• Performing client-side OAuth authorized Twitter API calls versus server side, how much of a difference is there in terms of performance?

  - by Terence Ponce

  I'm working on a Twitter application in Ruby on Rails. One of the biggest arguments that I have with other people on the project is the method of calling the Twitter API. Before, everything was done on the server: OAuth login, updating the user's Twitter data, and retrieving tweets. Retrieving tweets was the heaviest thing to do since we don't store the tweets in our database, so viewing the tweets means that we have to call the API every time. One of the people in the project suggested that we call the tweets through Javascript instead to lessen the load on the server. We used GET search, which, correct me if I'm wrong, will be removed when v1.0 becomes completely deprecated, but that really isn't a concern now. When the Twitter API has migrated completely to v1.1 (again, correct me if I'm wrong), every calls to the API must be authenticated, so we have to authenticate our Javascript requests to the API. As said here: We don't support or recommend performing OAuth directly through Javascript -- it's insecure and puts your application at risk. The only acceptable way to perform it is if you kept all keys and secrets server-side, computed the OAuth signatures and parameters server side, then issued the request client-side from the server-generated OAuth values. If we do exactly what Twitter suggests, the only difference between this and doing everything server-side is that our server won't have to contact the Twitter API anymore every time the user wants to view tweets. Here's how I would picture what's happening every time the user makes a request: If we do it through Javascript, it would be harder on my part because I would have to create the signatures manually for every request, but I will gladly do it if the boost in performance is worth all the trouble. Doing it through Ruby on Rails would be very easy since the Twitter gem does most of the grunt work already, so I'm really encouraging the other people in the project to agree with me. Is the difference in performance trivial or is it significant enough to switch to Javascript?

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• How to "back track"?

  - by esqew

  I find that I start projects and, due to my lack of experience, find that old database structures and huge blocks of code are inefficient and memory-costly. However, by the time I realize a re-design of the entire project is needed, the project has grown to such a size that it is simply too late to go back and modify the project in its current state and requires a completely new project file and the whole shebang. How should I prevent ruts such as this one, where it is too late to go back and modify the current project to fit specifications modified far down the road from the creation of the project? (Apologies in advance for confusing grammar, it's been a long day here... as you can probably tell.)

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• Which is more important in a web application code promotion hierarchy? production environment to repo equivalence or unidirectional propagation?

  - by ghbarratt

  Lets say you have a code promotion hierarchy consisting of several environments, (the polar end) two of which are development (dev) and production (prod). Lets say you also have a web application where important (but not developer controlled) files are created (and perhaps altered) in the production environment. Lets say that you (or someone above you) decided that the files which are controlled/created/altered/deleted in the production environment needed to go into the repository. Which of the following two sets of practice / approaches do you find best: Committing these non-developed file modifications made in the production environment so that the repository reflects the production environment as closely and as often as possible. Generally ignoring the non-developed production environment alterations, placing confidence in backups to restore the production environment should it be harmed, and keeping a resolution to avoid pushing developments through the promotion hierarchy in the reverse direction (avoiding pushing from prod to dev), only committing the files found in the production environment if they were absolutely necessary in other environments for development. So, 1 or 2, and why? PS - I am currently slightly biased toward maintaining production environment to repository equivalence (option 1), but I keep an open mind and would accept an answer supporting either.

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• Rewriting GPL code to change license

  - by I_like_traffic_lights

  I have found a GPL library (no dual license), which does exactly what I need. Unfortunately, the GPL license on the library is incompatible with the license of a different library I use. I have therefore decided to rewrite the GPL library, so the license can be changed. My question is: How extensive do the changes need to be to the library in order to be able to change the license? In other words, what is the cheapest way to do this?

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• Programming Language, Turing Completeness and Turing Machine

  - by Amumu

  A programming language is said to be Turing Completeness if it can successfully simulate a universal TM. Let's take functional programming language for example. In functional programming, function has highest priority over anything. You can pass functions around like any primitives or objects. This is called first class function. In functional programming, your function does not produce side effect i.e. output strings onto screen, change the state of variables outside of its scope. Each function has a copy of its own objects if the objects are passed from the outside, and the copied objects are returned once the function finishes its job. Each function written purely in functional style is completely independent to anything outside of it. Thus, the complexity of the overall system is reduced. This is referred as referential transparency. In functional programming, each function can have its local variables kept its values even after the function exits. This is done by the garbage collector. The value can be reused the next time the function is called again. This is called memoization. A function usually should solve only one thing. It should model only one algorithm to answer a problem. Do you think that a function in a functional language with above properties simulate a Turing Machines? Functions (= algorithms = Turing Machines) are able to be passed around as input and returned as output. TM also accepts and simulate other TMs Memoization models the set of states of a Turing Machine. The memorized variables can be used to determine states of a TM (i.e. which lines to execute, what behavior should it take in a give state ...). Also, you can use memoization to simulate your internal tape storage. In language like C/C++, when a function exits, you lose all of its internal data (unless you store it elsewhere outside of its scope). The set of symbols are the set of all strings in a programming language, which is the higher level and human-readable version of machine code (opcode) Start state is the beginning of the function. However, with memoization, start state can be determined by memoization or if you want, switch/if-else statement in imperative programming language. But then, you can't Final accepting state when the function returns a value, or rejects if an exception happens. Thus, the function (= algorithm = TM) is decidable. Otherwise, it's undecidable. I'm not sure about this. What do you think? Is my thinking true on all of this? The reason I bring function in functional programming because I think it's closer to the idea of TM. What experience with other programming languages do you have which make you feel the idea of TM and the ideas of Computer Science in general? Can you specify how you think?

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• Anonymous function vs. separate named function for initialization in jquery

  - by Martin N.

  We just had some controversial discussion and I would like to see your opinions on the issue: Let's say we have some code that is used to initialize things when a page is loaded and it looks like this: function initStuff() { ...} ... $(document).ready(initStuff); The initStuff function is only called from the third line of the snippet. Never again. Now I would say: Usually people put this into an anonymous callback like that: $(document).ready(function() { //Body of initStuff }); because having the function in a dedicated location in the code is not really helping with readability, because with the call on ready() makes it obvious, that this code is initialization stuff. Would you agree or disagree with that decision? And why? Thank you very much for your opinion!

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• Registering as developer on Google Play store

  - by ChosenOne

  I am registering as a Developer to sell paid applications on the Google Play store and have run into a slight issue: After I paid, I clicked on "Setup merchant details" link. I filled out the business address section, but in the "Public contact" section, Google says this: How can your customers get in touch with you? This information will be made available to your customers when they make a purchase. I work from home. I do not want customers knowing my home address, nor do I want it displayed anywhere online or even accessible by anyone. Should I just enter NA in each of the following fields? Surely Google understands that we have a right to keep such things private? How can I get around this while not getting my account suspended or risk not being approved?

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• Should I expect my team to have more than a basic proficiency with our source control system?

  - by Joshua Smith

  My company switched from Subversion to Git about three months ago. We had weeks of advance notice prior to the switch. Since I'd never used Git before (or any other DVCS), I read Pro Git and spent a little time spinning up my own repositories and playing around, so that when we switched I'd be able to keep working with minimal pain. Now I'm the 'Git guy' by default. With a couple of exceptions, most of my team still has no idea how Git works. For example, they still think of branches as complete copies of the source code, and even go so far as to clone the repo into multiple folders (one per branch). They generally look at Git as a scary black box. Given the fundamental nature of source control in our daily work (not to mention the ridiculous amount of power Git affords us), I'm of the opinion that any dev who doesn't achieve a certain level of proficiency with it is a liability. Should I expect my team to have at least some understanding of how Git works internally, and how to use it beyond the most basic pull/merge/push operations? Or am I just making something out of nothing?

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• First languages with generic programming support

  - by oluies

  Which was the first language with generic programming support, and what was the first major staticly typed language (widely used) with generics support. Generics implement the concept of parameterized types to allow for multiple types. The term generic means "pertaining to or appropriate to large groups of classes." I have seen the following mentions of "first": First-order parametric polymorphism is now a standard element of statically typed programming languages. Starting with System F [20,42] and functional programming lan- guages, the constructs have found their way into mainstream languages such as Java and C#. In these languages, first-order parametric polymorphism is usually called generics. From "Generics of a Higher Kind", Adriaan Moors, Frank Piessens, and Martin Odersky Generic programming is a style of computer programming in which algorithms are written in terms of to-be-specified-later types that are then instantiated when needed for specific types provided as parameters. This approach, pioneered by Ada in 1983 From Wikipedia Generic Programming

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