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• Interface vs Abstract Class (general OO)

  - by Kave

  Hi, I have had recently two telephone interviews where I've been asked about the differences between an Interface and an Abstract class. I have explained every aspect of them I could think of, but it seems they are waiting for me to mention something specific, and I dont know what it is. From my experience I think the following is true, if i am missing a major point please let me know: Interface: Every single Method declared in an Interface will have to be implemented in the subclass. Only Events, Delegates, Properties (C#) and Methods can exist in a Interface. A class can implement multiple Interfaces. Abstract Class Only Abstract methods have to be implemented by the subclass. An Abstract class can have normal methods with implementations. Abstract class can also have class variables beside Events, Delegates, Properties and Methods. A class can only implement one abstract class only due non-existence of Multi-inheritance in C#. 1) After all that the interviewer came up with the question What if you had an Abstract class with only abstract methods, how would that be different from an interface? I didnt know the answer but I think its the inheritance as mentioned above right? 2) An another interviewer asked me what if you had a Public variable inside the interface, how would that be different than in Abstract Class? I insisted you can't have a public variable inside an interface. I didn't know what he wanted to hear but he wasn't satisfied either. Many Thanks for clarification, Kave See Also: When to use an interface instead of an abstract class and vice versa Interfaces vs. Abstract Classes How do you decide between using an Abstract Class and an Interface?

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• How to optimize Conway's game of life for CUDA?

  - by nlight

  I've written this CUDA kernel for Conway's game of life: global void gameOfLife(float* returnBuffer, int width, int height) { unsigned int x = blockIdx.x*blockDim.x + threadIdx.x; unsigned int y = blockIdx.y*blockDim.y + threadIdx.y; float p = tex2D(inputTex, x, y); float neighbors = 0; neighbors += tex2D(inputTex, x+1, y); neighbors += tex2D(inputTex, x-1, y); neighbors += tex2D(inputTex, x, y+1); neighbors += tex2D(inputTex, x, y-1); neighbors += tex2D(inputTex, x+1, y+1); neighbors += tex2D(inputTex, x-1, y-1); neighbors += tex2D(inputTex, x-1, y+1); neighbors += tex2D(inputTex, x+1, y-1); __syncthreads(); float final = 0; if(neighbors < 2) final = 0; else if(neighbors 3) final = 0; else if(p != 0) final = 1; else if(neighbors == 3) final = 1; __syncthreads(); returnBuffer[x + y*width] = final; } I am looking for errors/optimizations. Parallel programming is quite new to me and I am not sure if I get how to do it right. The rest of the app is: Memcpy input array to a 2d texture inputTex stored in a CUDA array. Output is memcpy-ed from global memory to host and then dealt with. As you can see a thread deals with a single pixel. I am unsure if that is the fastest way as some sources suggest doing a row or more per thread. If I understand correctly NVidia themselves say that the more threads, the better. I would love advice on this on someone with practical experience.

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• Design for a Debate club assignment application

  - by Amir Rachum

  Hi all, For my university's debate club, I was asked to create an application to assign debate sessions and I'm having some difficulties as to come up with a good design for it. I will do it in Java. Here's what's needed: What you need to know about BP debates: There are four teams of 2 debaters each and a judge. The four groups are assigned a specific position: gov1, gov2, op1, op2. There is no significance to the order within a team. The goal of the application is to get as input the debaters who are present (for example, if there are 20 people, we will hold 2 debates) and assign them to teams and roles with regards to the history of each debater so that: Each debater should debate with (be on the same team) as many people as possible. Each debater should uniformly debate in different positions. The debate should be fair - debaters have different levels of experience and this should be as even as possible - i.e., there shouldn't be a team of two very experienced debaters and a team of junior debaters. There should be an option for the user to restrict the assignment in various ways, such as: Specifying that two people should debate together, in a specific position or not. Specifying that a single debater should be in a specific position, regardless of the partner. etc... If anyone can try to give me some pointers for a design for this application, I'll be so thankful! Also, I've never implemented a GUI before, so I'd appreciate some pointers on that as well, but it's not the major issue right now.

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• What's a reasonable way to mutate a primitive variable from an anonymous Java class?

  - by Steve

  I would like to write the following code: boolean found = false; search(new SearchCallback() { @Override void onFound(Object o) { found = true; } }); Obviously this is not allowed, since found needs to be final. I can't make found a member field for thread-safety reasons. What is the best alternative? One workaround is to define final class MutableReference<T> { private T value; MutableReference(T value) { this.value = value; } T get() { return value; } void set(T value) { this.value = value; } } but this ends up taking a lot of space when formatted properly, and I'd rather not reinvent the wheel if at all possible. I could use a List<Boolean> with a single element (either mutating that element, or else emptying the list) or even a Boolean[1]. But everything seems to smell funny, since none of the options are being used as they were intended. What is a reasonable way to do this?

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• Algorithm for count-down timer that can add on time

  - by Person

  I'm making a general timer that has functionality to count up from 0 or count down from a certain number. I also want it to allow the user to add and subtract time. Everything is simple to implement except for the case in which the timer is counting down from some number, and the user adds or subtracts time from it. For example: (m_clock is an instance of SFML's Clock) float Timer::GetElapsedTime() { if ( m_forward ) { m_elapsedTime += m_clock.GetElapsedTime() - m_elapsedTime; } else { m_elapsedTime -= m_elapsedTime - m_startingTime + m_clock.GetElapsedTime(); } return m_elapsedTime; } To be a bit more clear, imagine that the timer starts at 100 counting down. After 10 seconds, the above function would look like 100 -= 100 - 100 + 10 which equals 90. If it was called after 20 more seconds it would look like 90 -= 90 - 100 + 30 which equals 70. This works for normal counting, but if the user calls AddTime() ( just m_elapsedTime += arg ) then the algorithm for backwards counting fails miserably. I know that I can do this using more members and keeping track of previous times, etc. but I'm wondering whether I'm missing some implementation that is extremely obvious. I'd prefer to keep it as simple as possible in that single operation.

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• Supersede users need to press enter after inputting a string in python 3.0

  - by Cimex

  I've been attempting to create a simple Rock, Paper, Scissors game in python 3.0 -- very standard task for anybody learning programming. But, as I finish up to a point, I think,"wow, that'd be awesome", or,"it'd be cool to do this!" So anyways, I keep building upon the project... I've developed a menu, a single player game vs the computer, and just finished the multiplayer game. But, I've realized, that the multiplayer game isn't very effective. It just dosen't work like the analog version of the game. Currently, it'll ask for player1's input, then player2's input, compare them, and spit out the result and the current score. What I'd rather have happen is that the program asks for both players input at the same time and both players input their choice at the same time. I understand that I can easily do that by just grabbing the index of the first and second answer and compare the 2 inputs -- easy. But what I'd rather have happen is that after both players enter their one character answers at the same time (r for rock, p for paper, or s for scissors), then the program will auto enter the input. Not needing someone to press enter. The input would be dictated by the fact that 2 characters have been entered. I guess my question is: Is there any way to dictate what can be used as an input for 'enter'?

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• How can I split my conkeror-rc config over multiple files?

  - by Ryan Thompson

  Short version: can you help me fill in this code? var conkeror_settings_dir = ".conkeror.mozdev.org/settings"; function load_all_js_files_in_dir (dir) { var full_path = get_home_directory().appendRelativePath(dir); // YOUR CODE HERE } load_all_js_files_in_dir(conkeror_settings_dir); Background I'm trying out Conkeror for web browsing. It's an emacs-like browser running on Mozilla's rendering engine, using javascript as configuration language (filling the role that elisp plays for emacs). In my emacs config, I have split my customizations into a series of files, where each file is a single unit of related options (for example, all my perl-related settings might be in perl-settings.el. All these settings files are loaded automatically by a function in my .emacs that simply loads every elisp file under my "settings" directory. I am looking to structure my Conkeror config in the same way, with my main conkeror-rc file basically being a stub that loads all the js files under a certain directory relative to my home directory. Unfortunately, I am much less literate in javascript than I am in elisp, so I don't even know how to "source" a file.

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• What is an elegant way to set up a leiningen project that requires different dependencies based on the build platform?

  - by Savanni D'Gerinel

  In order to do some multi-platform GUI development, I have just switched from GTK + Clojure (because it looks like the Java bindings for GTK never got ported to Windows) to SWT + Clojure. So far, so good in that I have gotten an uberjar built for Linux. The catch, though, is that I want to build an uberjar for Windows and I am trying to figure out a clean way to manage the project.clj file. At first, I thought I would set the classpath to point to the SWT libraries and then build the uberjar. This would require that I set a classpath to the SWT libraries before running the jar, but I would likely need a launcher script, anyway. However, leiningen seems to ignore the classpath in this instance because it always reports that Currently, project.clj looks like this for me: (defproject alyra.mana-punk/character "1.0.0-SNAPSHOT" :description "FIXME: write" :dependencies [[org.clojure/clojure "1.2.0"] [org.clojure/clojure-contrib "1.2.0"] [org.eclipse/swt-gtk-linux-x86 "3.5.2"]] :main alyra.mana-punk.character.core) The relevant line is the org.eclipse/swt-gtk-linux-x86 line. If I want to make an uberjar for Windows, I have to depend on org.eclipse/swt-win32-win32-x86, and another one for x86-64, and so on and so forth. My current solution is to simply create a separate branch for each build environment with a different project.clj. This seems kinda like using a semi to deliver a single gallon of milk, but I am using bazaar for version control, so branching and repeated integrations are easy. Maybe the better way is to have a project.linux.clj, project.win32.clj, etc, but I do not see any way to tell leiningen which project descriptor to use. What are other (preferably more elegant) ways to set up such an environment?

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• How to manually set an authenticated user in Spring Security / SpringMVC

  - by David Parks

  After a new user submits a 'New account' form, I want to manually log that user in so they don't have to login on the subsequent page. The normal form login page going through the spring security interceptor works just fine. In the new-account-form controller I am creating a UsernamePasswordAuthenticationToken and setting it in the SecurityContext manually: SecurityContextHolder.getContext().setAuthentication(authentication); On that same page I later check that the user is logged in with: SecurityContextHolder.getContext().getAuthentication().getAuthorities(); This returns the authorities I set earlier in the authentication. All is well. But when this same code is called on the very next page I load, the authentication token is just UserAnonymous. I'm not clear why it did not keep the authentication I set on the previous request. Any thoughts? Could it have to do with session ID's not being set up correctly? Is there something that is possibly overwriting my authentication somehow? Perhaps I just need another step to save the authentication? Or is there something I need to do to declare the authentication across the whole session rather than a single request somehow? Just looking for some thoughts that might help me see what's happening here.

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• Rails - any fancy ways to handle 404s?

  - by jyoseph

  I have a rails app I built for an old site I converted from another cms (in a non-rails language, hehe). Most of the old pages are mapped to the new pages using routes.rb. But there are still a few 404s. I am a rails newb so I'm asking if there are any advanced ways to handle 404s. For example, if I was programming in my old language I'd do this: Get the URL (script_name) that was being accessed and parse it. Do a lookup in the database for any keywords, ids, etc found in the new URL. If found, redirect to the page (or if multiple records are found, show them all on a results page and let user choose). With rails I'd probably want to do :status = :moved_permanently I'm guessing? If not found, show a 404. Are there any gems/plugins or tutorials you know of that would handle such a thing, if it's even possible. Or can you explain on a high level how that can be done? I don't need a full code sample, just a push in the right direction. PS. It's a simple rails 3 app that uses a single Content model.

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• ANTLR : How to replace all characters defined as space with actual space

  - by Puneet Pawaia

  Hi All, My ANTLR code is as follow : LPARENTHESIS : ('('); RPARENTHESIS : (')'); fragment CHARACTER : ('a'..'z'|'0'..'9'|); fragment QUOTE : ('"'); fragment WILDCARD : ('*'); fragment SPACE : (' '|'\n'|'\r'|'\t'|'\u000C'|';'|':'|','); WILD_STRING : (CHARACTER)* ( ('?') (CHARACTER)* )+ ; PREFIX_STRING : (CHARACTER)+ ( ('*') )+ ; WS : (SPACE) { $channel=HIDDEN; }; PHRASE : (QUOTE)(LPARENTHESIS)?(WORD)(WILDCARD)?(RPARENTHESIS)?((SPACE)+(LPARENTHESIS)?(WORD)(WILDCARD)?(RPARENTHESIS)?)*(SPACE)+(QUOTE); WORD : (CHARACTER)+; What I would like to do is to replace all characters marked as space to be replaced with actual space character in the PHRASE. Also if possible, I would then like all continuous spaces to be represented by a single space. Any help would be most appreciated. For some reason, I am finding it hard to understand ANTLR. Any good tutorials out there ?

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• Are monads Writer m and Either e categorically dual?

  - by sdcvvc

  I noticed there is a dual relation between Writer m and Either e monads. If m is a monoid, then unit :: () -> m join :: (m,m) -> m can be used to form a monad: return is composition: a -> ((),a) -> (m,a) join is composition: (m,(m,a)) -> ((m,m),a) -> (m,a) The dual of () is Void (empty type), the dual of product is coproduct. Every type e can be given "comonoid" structure: unit :: Void -> e join :: Either e e -> e in the obvious way. Now, return is composition: a -> Either Void a -> Either e a join is composition: Either e (Either e a) -> Either (Either e e) a -> Either e a and this is the Either e monad. The arrows follow exactly the same pattern. Question: Is it possible to write a single generic code that will be able to perform both as Either e and as Writer m depending on the monoid given?

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• Strongly Typed DataSet column requires custom type to implement IXmlSerializable?

  - by Phil

  I have a strongly typed Dataset with a single table with three columns. These columns all contain custom types. DataColumn1 is of type Parent DataColumn2 is of type Child1 DataColumn3 is of type Child2 Here is what these classes look like: [Serializable] [XmlInclude(typeof(Child1)), XmlInclude(typeof(Child2))] public abstract class Parent { public int p1; } [Serializable] public class Child1 :Parent { public int c1; } [Serializable] public class Child2 : Parent { public int c1; } now, if I add a row with DataColumn1 being null, and DataColumns 2 and 3 populated and try to serialize it, it works: DataSet1 ds = new DataSet1(); ds.DataTable1.AddDataTable1Row(null, new Child1(), new Child2()); StringBuilder sb = new StringBuilder(); using (StringWriter writer = new StringWriter(sb)) { ds.WriteXml(writer);//Works! } However, if I try to add a value to DataColumn1, it fails: DataSet1 ds = new DataSet1(); ds.DataTable1.AddDataTable1Row(new Child1(), new Child1(), new Child2()); StringBuilder sb = new StringBuilder(); using (StringWriter writer = new StringWriter(sb)) { ds.WriteXml(writer);//Fails! } Here is the Exception: "Type 'WindowsFormsApplication4.Child1, WindowsFormsApplication4, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' does not implement IXmlSerializable interface therefore can not proceed with serialization." I have also tried using the XmlSerializer to serialize the dataset, but I get the same exception. Does anyone know of a way to get around this where I don't have to implement IXmlSerializable on all the Child classes? Alternatively, is there a way to implement IXmlSerializable keeping all default behavior the same (ie not having any class specific code in the ReadXml and WriteXml methods)

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• How to specialize a type parameterized argument to multiple different types for in Scala?

  - by jmount

  I need a back-check (please). In an article ( http://www.win-vector.com/blog/2010/06/automatic-differentiation-with-scala/ ) I just wrote I stated that it is my belief in Scala that you can not specify a function that takes an argument that is itself a function with an unbound type parameter. What I mean is you can write: def g(f:Array[Double]=>Double,Array[Double]):Double but you can not write something like: def g(f[Y]:Array[Y]=>Double,Array[Double]):Double because Y is not known. The intended use is that inside g() I will specialize fY to multiple different types at different times. You can write: def g[Y](f:Array[Y]=>Double,Array[Double]):Double but then f() is of a single type per call to g() (which is exactly what we do not want). However, you can get all of the equivalent functionality by using a trait extension instead insisting on passing around a function. What I advocated in my article was: 1) Creating a trait that imitates the structure of Scala's Function1 trait. Something like: abstract trait VectorFN { def apply[Y](x:Array[Y]):Y } 2) declaring def g(f:VectorFN,Double):Double (using the trait is the type). This works (people here on StackOverflow helped me find it, and I am happy with it)- but am I mis-representing Scala by missing an even better solution?

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• How should I secure my webapp written using Wicket, Spring, and JPA?

  - by Martin

  So, I have an web-based application that is using the Wicket 1.4 framework, and it uses Spring beans, the Java Persistence API (JPA), and the OpenSessionInView pattern. I'm hoping to find a security model that is declarative, but doesn't require gobs of XML configuration -- I'd prefer annotations. Here are the options so far: Spring Security (guide) - looks complete, but every guide I find that combines it with Wicket still calls it Acegi Security, which makes me think it must be old. Wicket-Auth-Roles (guide 1 and guide 2) - Most guides recommend mixing this with Spring Security, and I love the declarative style of @Authorize("ROLE1","ROLE2",etc). I'm concerned about having to extend AuthenticatedWebApplication, since I'm already extending org.apache.wicket.protocol.http.WebApplication, and Spring is already proxying that behind org.apache.wicket.spring.SpringWebApplicationFactory. SWARM / WASP (guide) - This looks the newest (though the main contributor passed away years ago), but I hate all of the JAAS-styled text files that declare permissions for principals. I also don't like the idea of making an Action class for every single thing a user might want to do. Secure models also aren't immediately obvious to me. Plus, there isn't an Authn example. Additionally, it looks like lots of folks recommend mixing the first and second options. I can't tell what the best practice is at all, though.

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• Git-Based Source Control in the Enterprise: Suggested Tools and Practices?

  - by Bob Murphy

  I use git for personal projects and think it's great. It's fast, flexible, powerful, and works great for remote development. But now it's mandated at work and, frankly, we're having problems. Out of the box, git doesn't seem to work well for centralized development in a large (20+ developer) organization with developers of varying abilities and levels of git sophistication - especially compared with other source-control systems like Perforce or Subversion, which are aimed at that kind of environment. (Yes, I know, Linus never intended it for that.) But - for political reasons - we're stuck with git, even if it sucks for what we're trying to do with it. Here are some of the things we're seeing: The GUI tools aren't mature Using the command line tools, it's far to easy to screw up a merge and obliterate someone else's changes It doesn't offer per-user repository permissions beyond global read-only or read-write privileges If you have a permission to ANY part of a repository, you can do that same thing to EVERY part of the repository, so you can't do something like make a small-group tracking branch on the central server that other people can't mess with. Workflows other than "anything goes" or "benevolent dictator" are hard to encourage, let alone enforce It's not clear whether it's better to use a single big repository (which lets everybody mess with everything) or lots of per-component repositories (which make for headaches trying to synchronize versions). With multiple repositories, it's also not clear how to replicate all the sources someone else has by pulling from the central repository, or to do something like get everything as of 4:30 yesterday afternoon. However, I've heard that people are using git successfully in large development organizations. If you're in that situation - or if you generally have tools, tips and tricks for making it easier and more productive to use git in a large organization where some folks are not command line fans - I'd love to hear what you have to suggest. BTW, I've asked a version of this question already on LinkedIn, and got no real answers but lots of "gosh, I'd love to know that too!"

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• Google app engine: Poor Performance with JDO + Datastore

  - by Bosh

  I have a simple data model that includes USERS: store basic information (key, name, phone # etc) RELATIONS: describe, e.g. a friendship between two users (supplying a relationship_type + two user keys) I'm getting very poor performance, for instance, if I try to print the first names of all of a user's friends. Say the user has 500 friends: I can fetch the list of friend user_ids very easily in a single query. But then, to pull out first names, I have to do 500 back-and-forth trips to the Datastore, each of which seems to take on the order of 30 ms. If this were SQL, I'd just do a JOIN and get the answer out fast. I understand there are rudimentary facilities for performing joins across un-owned relations in a relaxed implementation of JDO (as described at http://gae-java-persistence.blogspot.com) but they sound experimental and non-standard (e.g. my code won't work in any other JDO implementation). Is this really my best bet? Otherwise, how do people extract satisfactory performance from JDO/Datastore in this kind of (very common) situation? -Bosh

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• How to model has_many with polymorphism?

  - by Daniel Abrahamsson

  I've run into a situation that I am not quite sure how to model. Suppose I have a User class, and a user has many services. However, these services are quite different, for example a MailService and a BackupService, so single table inheritance won't do. Instead, I am thinking of using polymorphic associations together with an abstract base class: class User < ActiveRecord::Base has_many :services end class Service < ActiveRecord::Base validates_presence_of :user_id, :implementation_id, :implementation_type belongs_to :user belongs_to :implementation, :polymorphic = true delegate :common_service_method, :name, :to => :implementation end #Base class for service implementations class ServiceImplementation < ActiveRecord::Base validates_presence_of :user_id, :on => :create has_one :service, :as => :implementation has_one :user, :through => :service after_create :create_service_record #Tell Rails this class does not use a table. def self.abstract_class? true end #Default name implementation. def name self.class.name end protected #Sets up a service object def create_service_record service = Service.new(:user_id => user_id) service.implementation = self service.save! end end class MailService < ServiceImplementation #validations, etc... def common_service_method puts "MailService implementation of common service method" end end #Example usage MailService.create(..., :user_id => user.id) BackupService.create(...., :user_id => user.id) user.services.each do |s| puts "#{user.name} is using #{s.name}" end #Daniel is using MailService, Daniel is using BackupService So, is this the best solution? Or even a good one? How have you solved this kind of problem?

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• How to display many SVGs in Java with high performance

  - by Oak

  What I want My goal is to be able to display a large number of SVG images on a single drawing area in Java, each with its own translation/rotation/scale values. I'm looking for the simplest solution allowing this, optionally even using OpenGL to speed things up. What I've Tried My initial naive approach was to use SVGSalamander to draw directly on a JPanel, but the performance was pathetic. I poked around around and learned that I should do something like manually convert each SVG into a BufferedImage created with createCompatibleImage, then do the transformations I want, then draw it using double buffering. I ran into some troubles here, and before I continued I tried looking for frameworks to simplify things. What I've Looked At I've been a bit overwhelmed by the available options, which is why I'm turning to SO for help. I've looked at: Cairo (with Glitz maybe?) Libart - not sure if this actually supports SVGs FengGUI Slick - looks promising but a bit of an overkill But couldn't decide what is best for me to start working with, and I hope someone here as experience with any of these doing similar things.

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• Want to display a 3D model on the iPhone: how to get started?

  - by JeremyReimer

  I want to display and rotate a single 3D model, preferably textured, on the iPhone. Doesn't have to zoom in and out, or have a background, or anything. I have the following: an iPhone a MacBook the iPhone SDK Blender My knowledge base: I can make 3D models in various 3D programs (I'm most comfortable with 3D Studio Max, which I once took a course on, but I've used others) General knowledge of procedural programming from years ago (QuickBasic - I'm old!) Beginner's knowledge of object-oriented programming from going through simple Java and C# tutorials (Head Start C# book and my wife's intro to OOP course that used Java) I have managed to display a 3D textured model and spin it using a tutorial in C# I got off the net (I didn't just copy and paste, I understand basically how it works) and the XNA game development library, using Visual Studio on Windows. What I do not know: Much about Objective C Anything about OpenGL or OpenGL ES, which the iPhone apparently uses Anything about XCode My main problem is that I don't know where to start! All the iPhone books I found seem to be about creating GUI applications, not OpenGL apps. I found an OpenGL book but I don't know how much, if any, applies to iPhone development. And I find the Objective C syntax somewhat confusing, with the weird nested method naming, things like "id" that don't make sense, and the scary thought that I have to do manual memory management. Where is the best place to start? I couldn't find any tutorials for this sort of thing, but maybe my Google-Fu is weak. Or maybe I should start with learning Objective C? I know of books like Aaron Hillgrass', but I've also read that they are outdated and much of the sample code doesn't work on the iPhone SDK, plus it seems geared towards the Model-View-Controller paradigm which doesn't seem that suited for 3D apps. Basically I'm confused about what my first steps should be.

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• How to use R's ellipsis feature when writing your own function?

  - by Ryan Thompson

  The R language has a nifty feature for defining functions that can take a variable number of arguments. For example, the function data.frame takes any number of arguments, and each argument becomes the data for a column in the resulting data table. Example usage: > data.frame(letters=c("a", "b", "c"), numbers=c(1,2,3), notes=c("do", "re", "mi")) letters numbers notes 1 a 1 do 2 b 2 re 3 c 3 mi The function's signature includes an ellipsis, like this: function (..., row.names = NULL, check.rows = FALSE, check.names = TRUE, stringsAsFactors = default.stringsAsFactors()) { [FUNCTION DEFINITION HERE] } I would like to write a function that does something similar, taking multiple values and consolidating them into a single return value (as well as doing some other processing). In order to do this, I need to figure out how to "unpack" the ... from the function's arguments within the function. I don't know how to do this. The relevant line in the function definition of data.frame is object <- as.list(substitute(list(...)))[-1L], which I can't make any sense of. So how can I convert the ellipsis from the function's signature into, for example, a list? To be more specific, how can I write get_list_from_ellipsis in the code below? my_ellipsis_function(...) { input_list <- get.list.from.ellipsis(...) output_list <- lapply(X=input_list, FUN=do_something_interesting) return(output_list) } my_ellipsis_function(a=1:10,b=11:20,c=21:30)

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• Using hashing to group similar records

  - by Neil Dobson

  I work for a fulfillment company and we have to pack and ship many orders from our warehouse to customers. To improve efficiency we would like to group identical orders and pack these in the most optimum way. By identical I mean having the same number of order lines containing the same SKUs and same order quantities. To achieve this I was thinking about hashing each order. We can then group by hash to quickly see which orders are the same. We are moving from an Access database to a PostgreSQL database and we have .NET based systems for data loading and general order processing systems, so we can either do the hashing during the data loading or hand this task over to the DB. My question firstly is should the hashing be managed by DB, possibly using triggers, or should the hash be created on-the-fly using a view or something? And secondly would it be best to calculate a hash for each order line and then to combine these to find an order-level hash for grouping, or should I just use a trigger for all CRUD operations on the order lines table which re-calculates a single hash for the entire order and store the value in the orders table? TIA

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• Obfuscating ASP.Net dll breaks web application.

  - by uriDium

  I wouldn't usually bother to obfuscate a web application DLL but right now I have to share some server space with someone who might have a conflict of interest and might be tempted to steal the deal and decompile it. Not an ideal solution I know but hey. So I am using VS 2005, a web deployment project (which compiles into a single DLL) and Dotfuscator community edition. When I obfuscate the DLL the web application breaks and I get some message like Could not load type 'Browse' from assembly MyAssembly So I searched around and found that if I disable renaming then it should fix it. Which it does. But now when I look at the DLL using .Net reflector I can see everything again. So this seems kind of pointless. Is there a way to get this to work? Is there a better way to protect my DLL from someone I have to share a server with? UPDATE: I figured out my problem. All the classnames have changed but now all my <%@ Page Language="C#" AutoEventWireup="true" CodeFile="mycode.aspx.cs" Inherits="mycode" % is incorrect because mycode no longer exists. It is now aef or something. Is there any tool out there that will also change the names of the Codefile and Inherits tags?

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• Why do WCF clients depend on the app.config file?

  - by routeNpingme

  Like a lot of things, I'm sure there's a good reason for this, so please help me understand... Why, by default, do WCF services store settings in app.config? This has been so frustrating trying to work with multiple Silverlight class libraries. These class libraries are supposed to be completely independent from each other, and this dependency on the app.config seems to cause the following headaches: Single Responsibility Principle - I should be able to add a reference to a class library and go. If that class library uses a service reference, this idea is shot before I even start coding against it. Muddy Configuration - To get other libraries to work, I have to copy and paste the service configurations into the "main" application configs. If an endpoint changes in any way, I can't just worry about a new version of that class DLL - I have to worry about anything that uses it, too. Complex Alternatives - Programmatically creating the endpoint isn't pretty. Period. There has to be a better way. Why doesn't WCF at least separate the service configurations into a ServiceName.config or something that gets copied to an output directory. What am I missing? How do you deal with this?

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• How do I debug into an ILMerged assembly?

  - by Rory Becker

  Summary I want to alter the build process of a 2-assembly solution, such that a call to ILMerge is invoked, and the build results in a single assembly. Further I would like to be able to debug into the resultant assembly. Preparation - A simple example New Solution - ClassLibrary1 Create a static function 'GetMessage' in Class1 which returns the string "Hello world" Create new console app which references the ClassLibrary. Output GetMessage from main() via the console. You now have a 2 assembly app which outputs "Hello World" to the console. So what next..? I would like to alter the Console app build process, to include a post build step which uses ILMerge, to merge the ClassLibrary assembly into the Console assembly After this step I should be able to: Run the Console app directly with no ClassLibrary1.dll present Run the Console app via F5 (or F11) in VS and be able to debug into each of the 2 projects. Limited Success I read this blogpost and managed to achieve the merge I was after with a post-build command of... "$(ProjectDir)ILMerge.bat" "$(TargetDir)" $(ProjectName) ...and an ILMerge.bat file which read... CD %1 Copy %2.exe temp.exe ILMerge.exe /out:%2.exe temp.exe ClassLibrary1.dll Del temp.exe Del ClassLibrary1.* This works fairly well, and does in fact produce an exe which runs outside the VS environment as required. However it does not appear to produce symbols (.pdb file) which VS is able to use in order to debug into the code. I think this is the last piece of the puzzle. Does anyone know how I can make this work? FWIW I am running VS2010 on an x64 Win7 x64 machine.

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