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• Can WinRT really be used at just the boundaries?

  - by Bret Kuhns

  Microsoft (chiefly, Herb Sutter) recommends when using WinRT with C++/CX to keep WinRT at the boundaries of the application and keep the core of the application written in standard ISO C++. I've been writing an application which I would like to leave portable, so my core functionality was written in standard C++, and I am now attempting to write a Metro-style front end for it using C++/CX. I've had a bit of a problem with this approach, however. For example, if I want to push a vector of user-defined C++ types to a XAML ListView control, I have to wrap my user-defined type in a WinRT ref/value type for it to be stored in a Vector^. With this approach, I'm inevitably left with wrapping a large portion of my C++ classes with WinRT classes. This is the first time I've tried to write a portable native application in C++. Is it really practical to keep WinRT along the boundaries like this? How else could this type of portable core with a platform-specific boundary be handled?

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• Can't decide between Java or Python for college [on hold]

  - by Will Harrison

  I'm returning to college in about a month for Computer Science. My problem is, I have been programming on the web since I left (4 years ago), using PHP, ASP.NET, and JavaScript. I want to bone up on a more general purpose language that is cross platform before I begin. I would also like to be using a language that is common at my school and I know that they teach the students C++, Java, and Python. I would like to choose between Java or Python but I'm not sure which one. What do you think would be better based on job prospects in the next 2 years and community?

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• Simple vs Complex (but performance efficient) solution - which one to choose and when?

  - by ManojGumber

  I have been programming for a couple of years and have often found myself at a dilemma. There are two solutions - one is simple one i.e. simple approach, easier to understand and maintain. It involves some redundancy, some extra work (extra IO, extra processing) and therefore is not the most optimal solution. but other uses a complex approach,difficult to implement, often involving interaction between lot of modules and is a performance efficient solution. Which solution should I strive for when I do not have hard performance SLA to meet and even the simple solution can meet the performance SLA? I have felt disdain among my fellow developers for simple solution. Is it good practice to come up with most optimal complex solution if your performance SLA can be met by a simple solution?

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• git, maven and jenkins - versioning, dev and release builds workflow

  - by varesa

  What is the preferred way to do the following with git, maven and jenkins: I am developping an application, which I would like to maintain "dev" and "release" branches. I would like jenkins to build both. It could be so that the release-artifacts would have versions like 1.5.2 and the dev-builds would just be 0.0.1-SNAPSHOTs. I would like to not have to have 2 different pom.xml files. I looked into profiles, but they don't seem to be able to change artifact versions. One way I looked at could be adding a 'qualifier' to the test-builds. Of course I could just rename the file, because the real artifact-information on this is not important, because the app is a standalone one. What would be the preferred way to doing this? Or how would you do this?

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• Is there a canonical book for learning Java as an experienced developer?

  - by Steven Elliott Jr

  I have been a .NET developer now for about the past 5/6 years give or take. I have never done any professional Java development and the last time I really touched it was probably back in college. I have been toying with the Scala language a little bit but nothing serious. Recently, I've been offered an opportunity to do some pretty cool work, but using Java instead of .NET. I think I can get by alright with my current skill set, meaning I already know how to program well and am familiar with languages such as C# and C++, etc. So, the syntax and all that language stuff are really not a problem. What I need is a really good reference book and a book about how to think in Java. Each language/Framework/Stack tries to address things a certain way and I'm sure Java is no different. What are some great Java books that you simply can't live without? Are there any books that talk about the most important parts of Java that must be understood before all else? As a side note, I will be doing mostly Java web development. Not really 100% on what types of stuff they are using for persistence, framework, server, etc.

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• Is ASP.NET MVC completely (and exclusively) based on conventions?

  - by Mike Valeriano

  --TL;DR Is there a "Hello World!" ASP.NET MVC tutorial out there that doesn't rely on conventions and "stock" projects? Is it even possible to take advantage of the technology without reusing the default file structure, and start from a single "hello_world.asp" file or something (like in PHP)? Am I completely mistaken and I should be looking somewhere else, maybe this? I'm interested in the MVC framework, not Web Forms --Background I've played a bit with PHP in the past, just for fun, and now I'm back to it since web development became relevant for me once again. I'm no professional, but I try to gain as much knowledge and control over the technology I'm working with as possible. I'm using Visual Studio 2012 for C# - my "desktop" language of choice - and since I got the Professional Edition from Dreamspark, the Web Development Tools are available, including ASP.NET MVC 4. I won't touch Web Forms, but the MVC Framework got my attention because the MVC pattern is something I can really relate to, since it provides the control I want but... not quite. Learning PHP was easy - and right form the start I could just create a "hello_world.php" file and just do something like this for immediate results: <!-- file: hello_world.php --> <?php> echo "Hello World!"; <?> But I couldn't find a single ASP.NET (MVC) tutorial out there (I'll be sure to buy one of the upcoming MVC 4 books, only a month away or so) that would start like that. They all start with a sample project, building up knowledge from the basics and heavily using conventions as they go along. Which is fine, I suppose, but it's now the best way for me to learn things. Even the "Empty" project template for a new ASP.NET MVC 4 Application in VS2012 is not empty at all: several files and folders are created for you - much like a new C# desktop application project, but with C# I can in fact start from scratch, creating the project structure myself. It is not the case with PHP: I can choose from a plethora of different MVC frameworks I can just create my own framework I can just skip frameworks altogether, and toss random PHP along with my HTML on a single file and make it work I understand the framework needs to establish some rules, but what if I just want to create a single page website with some C# logic behind it? Do I really need to create a whole bloat of files and folders for the sake of convention? Also, please understand that I haven't gotten far on any of those tutorials mainly because of this reason, but, if that's the only way to do it, I'll go for it using one of the books I've mentioned before. This is my first contact with ASP.NET but from the few comparisons I've read, I believe I should stay the hell away from Web Forms. Thank you. (Please forgive the broken English - it is not my primary language.)

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• Can One Get a Solid Programming Foundation Without Going To College/University?

  - by Daniel

  First, I have already searched the site and read all the previous "self-taught vs. college" topics. The majority of the answers defended that going to college was the best choice, for two main reasons: Going to college gives you the paper, which is essential to landing jobs, especially in tough economic times. Going to college gives you a solid programming base, teaching you the principles that will be essential regardless of the language/path you take after. Here comes my question: I am not worried about reason 1 at all, because I already have my own company (I build websites/ do affiliate marketing) and a stable financial situation, so I am pretty sure I won't need to look around for a job. I am worried about reason 2 though. That is, I want to make sure I'll have as solid a programming foundation as anyone else out there, and I am wondering if that is possible with self-learning. Suppose I take my time to study the very basics, like discrete maths, algorithm design, programming logic, computer architecture, Assembly, C programming, databases and data structures - mostly using books,online resources and lots of coding. Say I spend 1-2 years covering those basics. Do you think my foundation would be solid, or still lack in comparison to someone who went to college?

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• From physics to Java programmer?

  - by inovaovao

  I'm a physics phd with little actual programming experience. I've always liked programming and played around with Basic and Pascal (also VB and Delphi) as a teen, but the largest actual project I completed was an assignement for the introductory computer science class in university where I wrote a nice little program (about 1500 lines of pascal) to display functions of 2 variables in 3D. I've had also a couple other projects of a few hundred lines range, but during my phd I didn't have (or take) the time to program more (string theory is hard guys!), beside playing around with ruby. Now I've decided that I'm more interested in programming than in physics and started to learn Java (hoping to pass the certification exam next week) and OO design. Still, I have trouble deciding on what to focus next (Java EE? Web development? algorithms and C programming?) in order to maximize my employement chances. Bear in mind that I'm aiming (mostly) at the swedish job market and that I'm 30 years old. So for the questions: Do you think that I have any chances to start and make a career in IT and programming coming from physics? What would be the best strategy to maximize my value in the field? Do you have suggestions as to where my physics background might be useful?

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• Support / Maintenance documentation for development team

  - by benwebdev

  Hi, I'm working in the Development dept (around 40 developers) for a large E-Commerce company. We've grown quickly but have not evolved very well in the field of documenting our work. We work with an Agile / Scrum-like methodology with our development and testing but documentation seems to be neglected. We need to be able to make documentation that would aid a developer who hasnt worked on our project before or was new to the company. We also have to create more high level information for our support department to explain any extra config settings and fixes of known issues that may arise, if any. Currently we put this in a badly put together wiki, based on an old Sharepoint / TFS site. Can anyone suggest some ideal links or advice on improving the documentation standard? What works in other companies? Has anyone got avice on developing documentation as part of an agile process? Many thanks, ben

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• Organizing code for iOS app development

  - by KronoS

  I've been developing an app for the iOS platform, and as I've been going along, I've noticed that I've done a terrible job of keeping my files (.h, .m, .mm) organized. Is there any industry standards or best practices when it comes to organizing files for an iOS project? My files include custom classes (beside the view controllers), customized View Controllers, third-party content, code that works only on iOS 5.0+ and code that works on previous versions. What I'm looking for is a solution to keep things organized in a manner that others (or myself in years to come) can look at this and understand the basic structure of the application and not get lost in the multiple files found therein.

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• What are the pros and cons about developing under MAC OS? [closed]

  - by user827992

  Sometimes i get the chance to program under MAC OS, i knew about this OS since Apple shipped its computers with a PowerPC by Motorola ( since Panther, more or less ), these days they are all X86 and i see no particular advantages about adopting this platform, also i see only downsides for the main part, i do not want to cause flames, please reply if you have a good answer or you can contribute in some constructive way. I'm trying to write a list of the natively supported languages, or the languages that comes only under MAC OS with some particular technology, my list is this: Objective C with Cocoa/Carbon I'm not considering personal preferences here, if a person X likes to code under Xcode it's probably ok to have a MAC, if a person Y likes to code under Visual Studio it's probably ok to not having a MAC, my purpose is to clarify what MAC OS is good for. I also do not get why people glorify the MAC for historical reasons, I mean a language like Java just comes for MAC only in the 7th edition of its JDK, things like GCC are just a porting and many technologies are out of the question like C# ( I'm sorry, i do not consider MonoDevelop like a serious alternative ) , .Net, ASP, DirectX, and many others are just, again, porting or free software, like PHP, MySQL, Javascript, XML, CSS, OpenGL, etc etc. My question is: what is so special about being a programmer under MAC OS? There is something that I have not seen? I also noticed that a significant portion of MAC users end up using their MAC like a normal Windows PC with Parallels or something like that. I can afford to buy a MAC, show me why this machine is so unique.

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• Naming boolean field that is a verb

  - by dnhang

  In Java, by convention getter and setter for boolean fields will be isField() and setField(). This works perfectly fine with field names that are adjectives like active, visible, closed, etc. But how do I name a field that has meaning of a verb, like haveChildren? Add _ing to the verb (havingChildren), maybe? Edit: to clarify, I don't have control of the method names (getter and setter), they are auto-generated by the IDE. So what I need is an appropriate field name so that when the IDE generate a getter for it, it make senses. For example, hasChildren is a perfect field name, but when the IDE generate the getter for the field it would be isHasChildren. How do I solve this?

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• How fast does a language get outdated?

  - by Dummy Derp

  I started learning Java recently. I started learning it using books that I picked up from the library, some that I bought, and here and there from Java documentation. The book that I use for Java was published in the year 2011. In 2012, Java8 will be released followed by Java9 in the year 2013. The questions are: How do I keep myself updated about developments in Java without having to buy a tome for Java8 and/or Java9 Is a book published in 2008 an outdated book for studying JSP and Servelets? I'm talking about Head First Servlets and JSP

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• How does the GPL work in regards to languages like Dart which compile to other languages?

  - by Peter-W

  Google's Dart language is not supported by any Web Browsers other than a special build of Chromium known as Dartium. To use Dart for production code you need to run it through a Dart-JavaScript compiler/translator and then use the outputted JavaScript in your web application. Because JavaScript is an interpreted language everyone who receives the "binary"(Aka, the .js file) has also received the source code. Now, the GNU General Public License v3.0 states that: "The “source code” for a work means the preferred form of the work for making modifications to it." Which would imply that the original Dart code in addition to the JavaScript code must also be provided to the end user. Does this mean that any web applications written in Dart must also provide the original Dart code to all visitors of their website even though a copy of the source code has already been provided in a human readable/writable/modifiable form?

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• Empirical evidence for choice of programming paradigm to address a problem

  - by Graham Lee

  The C2 wiki has a discussion of Empirical Evidence for Object-Oriented Programming that basically concludes there is none beyond appeal to authority. This was last edited in 2008. Discussion here seems to bear this out: questions on whether OO is outdated, when functional programming is a bad choice and the advantages and disadvantages of AOP are all answered with contributors' opinions without reliance on evidence. Of course, opinions of established and reputed practitioners are welcome and valuable things to have, but they're more plausible when they're consistent with experimental data. Does this evidence exist? Is evidence-based software engineering a thing? Specifically, if I have a particular problem P that I want to solve by writing software, does there exist a body of knowledge, studies and research that would let me see how the outcome of solving problems like P has depended on the choice of programming paradigm? I know that which paradigm comes out as "the right answer" can depend on what metrics a particular study pays attention to, on what conditions the study holds constant or varies, and doubtless on other factors too. That doesn't affect my desire to find this information and critically appraise it. It becomes clear that some people think I'm looking for a "turn the crank" solution - some sausage machine into which I put information about my problem and out of which comes a word like "functional" or "structured". This is not my intention. What I'm looking for is research into how - with a lot of caveats and assumptions that I'm not going into here but good literature on the matter would - certain properties of software vary depending on the problem and the choice of paradigm. In other words: some people say "OO gives better flexibility" or "functional programs have fewer bugs" - (part of) what I'm asking for is the evidence of this. The rest is asking for evidence against this, or the assumptions under which these statements are true, or evidence showing that these considerations aren't important. There are plenty of opinions on why one paradigm is better than another; is there anything objective behind any of these?

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• Selecting a JAX-RS implementation for a new project

  - by Fernando Correia

  I'm starting a new Java project which will require a RESTful API. It will be a SaaS business application serving mobile clients. I have developed one project with Java EE 6, but I'm not very familiar with the ecosystem, since most of my experience is on the Microsoft platform. Which would be a sensible choice for a JAX-RS implementation for a new project such as described? Judging by Wikipedia's list, main contenders seem to be Jersey, Apache CXF, RESTeasy and Restlet. But the Comparison of JAX-RS Implementations cited on Wikipedia is from 2008. My first impressings from their respective homepages is that: CXF aims to be a very comprehensive solution (reminds me of WCF in the Microsoft space), which makes me think it can be more complex to understand, setup and debug than what I need; Jersey is the reference implementation and might be a good choice, but it's legacy from Sun and I'm not sure how Oracle is treating it (announcements page doesn't work and last commit notice is from 4 months ago); RESTeasy is from JBoss and probably a solid option, though I'm not sure about learning curve; Restlet seems to be popular but has a lot of history, I'm not sure how up-to-date it is in the Java EE 6 world or if it carries a heavy J2EE mindset (like lots of XML configuration). What would be the merits of each of these alternatives? What about learning curve? Feature support? Tooling (e.g. NetBeans or Eclipse wizards)? What about ease of debugging and also deployment? Is any of these project more up-to-date than the others? How stable are them?

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• Best exception handling practices or recommendations?

  - by user828584

  I think the two main problems with my programs are my code structure/organization and my error handling. I'm reading Code Complete 2, but I need something to read for working with potential problems. For example, on a website, if something can only happen if the user tampers with data via javascript, do you write for that? Also, when do you not catch errors? When you write a class that expects a string and an int as input, and they aren't a string and int, do you check for that, or do you let it bubble up to the calling method that passed incorrect parameters? I know this is a broad topic that can't be answered in a single answer here, so what I'm looking for is a book or resource that's commonly accepted as teaching proper exception handling practice.

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• Advice on a good comeback strategy after years of java abstinence

  - by simou

  It's almost 5 yrs since I left the java IT-project/enterprise business. Before I was a highly skilled enterprise developer / OO architect with more than 10 years experience in the business. I was proficient in many of those enterprise related technologies, including DWHing. Since then I haven't been doing any large scale programming, a little bit of C, Python, some dips into Scala, hacking a small java-plugin framework, opengl, but only as fun projects. Now I want to re-enter the java stage again, i.e. I'm looking for job opportunities as a developer. But I fear I might have lost much of my former punching strength, e.g. I would have to give my SQL knowledge a deep refreshing breath, re-visit basic stuff like design patterns, enterprise architectures, etc. and probably learn the new stuff like EJB3.1, JEE 6 too. I also missed the whole scrum craze. So from your own experience, what subject should I tackle first? Like technology (which ones?) or design skills (uml..)? But what I'm also wondering is since the basic design / architectural principles haven't changed much by now, what would be the chance on the job market for someone like me who left the java-world at a time where everything was less fragmented and EJB2.1 and XDoclet were de-facto standards? And how could I convince a potential employer that I'm still an effective on-the-job learner? Should I rather aim for "junior positions" ? Lots of questions but I'd be really glad if you could share your (encouraging :) thoughts with me. cheers! (btw I'm based in Austria)

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• What Programming languages/technologies stack to use when building Facebook like website ?

  - by Blaze Boy

  I'm developing a website idea that will perform the same as Facebook functionality without the applications extensibility. the site will have a client application to perform a task similar to dropbox.com the site will be a social network of some sort of professionalism, it will highlight code of almost all languages has a high speed backend database Now what languages/techniques do I need to use to achieve that?

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• Error Copying Source File in Audio Spectrum Visualizer [closed]

  - by David Dimalanta

  I'm testing this code using LibGDX, Java, and Eclipse to test the music player that detects the frequency. I saw this one on this website plus the link on GitHub: http://gtomee.com/2012/07/28/audio-spectrum-visualizer-with-libgdx/ It works when running on desktop project folder but not on Android project folder and the result is this: 10-10 13:57:45.320: E/AndroidRuntime(9421): FATAL EXCEPTION: GLThread 16845 10-10 13:57:45.320: E/AndroidRuntime(9421): com.badlogic.gdx.utils.GdxRuntimeException: Error copying source file: soundtrack 1 bioman.mp3 (Internal) 10-10 13:57:45.320: E/AndroidRuntime(9421): To destination: tmp/audio-spectrum.mp3 (External) 10-10 13:57:45.320: E/AndroidRuntime(9421): at com.badlogic.gdx.files.FileHandle.copyFile(FileHandle.java:625) 10-10 13:57:45.320: E/AndroidRuntime(9421): at com.badlogic.gdx.files.FileHandle.copyTo(FileHandle.java:534) 10-10 13:57:45.320: E/AndroidRuntime(9421): at com.bodapps.rhythm.Drop.create(Drop.java:393) 10-10 13:57:45.320: E/AndroidRuntime(9421): at com.badlogic.gdx.backends.android.AndroidGraphics.onSurfaceChanged(AndroidGraphics.java:292) 10-10 13:57:45.320: E/AndroidRuntime(9421): at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1505) 10-10 13:57:45.320: E/AndroidRuntime(9421): at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1240) 10-10 13:57:45.320: E/AndroidRuntime(9421): Caused by: com.badlogic.gdx.utils.GdxRuntimeException: Error stream writing to file: tmp/audio-spectrum.mp3 (External) 10-10 13:57:45.320: E/AndroidRuntime(9421): at com.badlogic.gdx.files.FileHandle.write(FileHandle.java:313) 10-10 13:57:45.320: E/AndroidRuntime(9421): at com.badlogic.gdx.files.FileHandle.copyFile(FileHandle.java:623) 10-10 13:57:45.320: E/AndroidRuntime(9421): ... 5 more 10-10 13:57:45.320: E/AndroidRuntime(9421): Caused by: com.badlogic.gdx.utils.GdxRuntimeException: Error writing file: tmp/audio-spectrum.mp3 (External) 10-10 13:57:45.320: E/AndroidRuntime(9421): at com.badlogic.gdx.files.FileHandle.write(FileHandle.java:293) 10-10 13:57:45.320: E/AndroidRuntime(9421): at com.badlogic.gdx.files.FileHandle.write(FileHandle.java:305) 10-10 13:57:45.320: E/AndroidRuntime(9421): ... 6 more 10-10 13:57:45.320: E/AndroidRuntime(9421): Caused by: java.io.FileNotFoundException: /storage/sdcard0/tmp/audio-spectrum.mp3: open failed: EACCES (Permission denied) 10-10 13:57:45.320: E/AndroidRuntime(9421): at libcore.io.IoBridge.open(IoBridge.java:416) 10-10 13:57:45.320: E/AndroidRuntime(9421): at java.io.FileOutputStream.<init>(FileOutputStream.java:88) 10-10 13:57:45.320: E/AndroidRuntime(9421): at com.badlogic.gdx.files.FileHandle.write(FileHandle.java:289) 10-10 13:57:45.320: E/AndroidRuntime(9421): ... 7 more 10-10 13:57:45.320: E/AndroidRuntime(9421): Caused by: libcore.io.ErrnoException: open failed: EACCES (Permission denied) 10-10 13:57:45.320: E/AndroidRuntime(9421): at libcore.io.Posix.open(Native Method) 10-10 13:57:45.320: E/AndroidRuntime(9421): at libcore.io.BlockGuardOs.open(BlockGuardOs.java:110) 10-10 13:57:45.320: E/AndroidRuntime(9421): at libcore.io.IoBridge.open(IoBridge.java:400) 10-10 13:57:45.320: E/AndroidRuntime(9421): ... 9 more I'm not sure if I come this to the right place for help and suggestions.

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• How do you develop web applications? [closed]

  - by ck3g

  How do you and/or your team develop your web applications? Language, framework or platform doesn't matter. I would like to know about the structure of your environment. For example: Using IDE on workstation and project files on remote host accessing via sftp. Files are saved instantly on remote host; All files are local and are uploaded on remote host during saving; Files are local, web server is running on local computer and is tested at local host. etc. You could write down also about the benefits of your approach, this will be useful for me. Thanks upd: Here must be a question and here it is: which is the best approach by your opinion?

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• How much is modern programming still tied to underyling digital logic?

  - by New Talk

  First of all: I've got no academic background. I'm working primarily with Java and Spring and I'm also fond of web programming and relational databases. I hope I'm using the right terms and I hope that this vague question makes some sense. Today the following question came to my mind: How much is modern programming still tied to the underlying digital logic? With modern programming I mean concepts like OOP, AOP, Java 7, AJAX, … I hope you get the idea. Do they no longer need the digital logic with which computers are working internally? Or is binary logic still ubiquitous when programming this way? If I'd change the inner workings of a computer overnight, would it matter, because my programming techniques are already that abstract? P. S.: With digital logic I mean the physical representation of everything "inside" the computer as zeroes and ones. Changed "binary" to "digital".

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• Type checking and recursive types (Writing the Y combinator in Haskell/Ocaml)

  - by beta

  When explaining the Y combinator in the context of Haskell, it's usually noted that the straight-forward implementation won't type-check in Haskell because of its recursive type. For example, from Rosettacode [1]: The obvious definition of the Y combinator in Haskell canot be used because it contains an infinite recursive type (a = a -> b). Defining a data type (Mu) allows this recursion to be broken. newtype Mu a = Roll { unroll :: Mu a -> a } fix :: (a -> a) -> a fix = \f -> (\x -> f (unroll x x)) $ Roll (\x -> f (unroll x x)) And indeed, the “obvious” definition does not type check: ?> let fix f g = (\x -> \a -> f (x x) a) (\x -> \a -> f (x x) a) g <interactive>:10:33: Occurs check: cannot construct the infinite type: t2 = t2 -> t0 -> t1 Expected type: t2 -> t0 -> t1 Actual type: (t2 -> t0 -> t1) -> t0 -> t1 In the first argument of `x', namely `x' In the first argument of `f', namely `(x x)' In the expression: f (x x) a <interactive>:10:57: Occurs check: cannot construct the infinite type: t2 = t2 -> t0 -> t1 In the first argument of `x', namely `x' In the first argument of `f', namely `(x x)' In the expression: f (x x) a (0.01 secs, 1033328 bytes) The same limitation exists in Ocaml: utop # let fix f g = (fun x a -> f (x x) a) (fun x a -> f (x x) a) g;; Error: This expression has type 'a -> 'b but an expression was expected of type 'a The type variable 'a occurs inside 'a -> 'b However, in Ocaml, one can allow recursive types by passing in the -rectypes switch: -rectypes Allow arbitrary recursive types during type-checking. By default, only recursive types where the recursion goes through an object type are supported. By using -rectypes, everything works: utop # let fix f g = (fun x a -> f (x x) a) (fun x a -> f (x x) a) g;; val fix : (('a -> 'b) -> 'a -> 'b) -> 'a -> 'b = <fun> utop # let fact_improver partial n = if n = 0 then 1 else n*partial (n-1);; val fact_improver : (int -> int) -> int -> int = <fun> utop # (fix fact_improver) 5;; - : int = 120 Being curious about type systems and type inference, this raises some questions I'm still not able to answer. First, how does the type checker come up with the type t2 = t2 -> t0 -> t1? Having come up with that type, I guess the problem is that the type (t2) refers to itself on the right side? Second, and perhaps most interesting, what is the reason for the Haskell/Ocaml type systems to disallow this? I guess there is a good reason since Ocaml also will not allow it by default even if it can deal with recursive types if given the -rectypes switch. If these are really big topics, I'd appreciate pointers to relevant literature. [1] http://rosettacode.org/wiki/Y_combinator#Haskell

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• Refactoring this code that produces a reverse-lookup hash from another hash

  - by Frank Joseph Mattia

  This code is based on the idea of a Form Object http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/ (see #3 if unfamiliar with the concept). My actual code in question may be found here: https://gist.github.com/frankjmattia/82a9945f30bde29eba88 The code takes a hash of objects/attributes and creates a reverse lookup hash to keep track of their delegations to do this. delegate :first_name, :email, to: :user, prefix: true But I am manually creating the delegations from a hash like this: DELEGATIONS = { user: [ :first_name, :email ] } At runtime when I want to look up the translated attribute names for the objects, all I have to go on are the delegated/prefixed (have to use a prefix to avoid naming collisions) attribute names like :user_first_name which aren't in sync with the rails i18n way of doing it: en: activerecord: attributes: user: email: 'Email Address' The code I have take the above delegations hash and turns it into a lookup table so when I override human_attribute_name I can get back the original attribute name and its class. Then I send #human_attribute_name to the original class with the original attribute name as its argument. The code I've come up with works but it is ugly to say the least. I've never really used #inject so this was a crash course for me and am quite unsure if this code effective way of solving my problem. Could someone recommend a simpler solution that does not require a reverse lookup table or does that seem like the right way to go? Thanks, - FJM

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• Adaptive Payment with Paypal in Iphone App

  - by user2436477

  I wanted to implement three way transection where there is only one payer but two different receivers. Both receivers will receive predefined percentage of payment. I implemented demo for single sender and single receiver,And it works fine.But i don't know how to implement for three way transection. So do i have to create library by myself ? OR Is there any library for adaptive payment feature?

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