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  • Which is a better practice - helper methods as instance or static?

    - by Ilian Pinzon
    This question is subjective but I was just curious how most programmers approach this. The sample below is in pseudo-C# but this should apply to Java, C++, and other OOP languages as well. Anyway, when writing helper methods in my classes, I tend to declare them as static and just pass the fields if the helper method needs them. For example, given the code below, I prefer to use Method Call #2. class Foo { Bar _bar; public void DoSomethingWithBar() { // Method Call #1. DoSomethingWithBarImpl(); // Method Call #2. DoSomethingWithBarImpl(_bar); } private void DoSomethingWithBarImpl() { _bar.DoSomething(); } private static void DoSomethingWithBarImpl(Bar bar) { bar.DoSomething(); } } My reason for doing this is that it makes it clear (to my eyes at least) that the helper method has a possible side-effect on other objects - even without reading its implementation. I find that I can quickly grok methods that use this practice and thus help me in debugging things. Which do you prefer to do in your own code and what are your reasons for doing so?

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  • Stuff you learned in school, that you have never used again?

    - by Mercfh
    Obviously we learn plenty of things in our University/College/Whatever that probably don't apply to everyday use, but is there anything that stands out particularly? Maybe something that was concentrated ALOT on? For me it was def. 2 things: OO Concepts and Pointers I still use OO, but not nearly to the amount people made it out to be, i can see where it'd be useful but in my line of work we don't have huge amounts of classes, maybe a couple at most. And there certainly isn't much OO reuse (i finally figured out what that means lol) Pointers are another thing, again I can see where they'd be useful...however I barely barely ever touch them, nor do the others I work with. I guess language choice has alot to do with that but still. What about you guys? edit: For those who are asking I work for a Large Printer company, and most of the Applications we work on are Java+XML and Actionscript for "Printer Apps". But we are moving towards other languages (think like webkits and stuff). So the Code amounts per parts are quite small. I never say OO wasn't useful I just said I personally havent seen it used in my workplace much.

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  • If a library doesn't provide all my needs, how should I proceed?

    - by 9a3eedi
    I'm developing an application involving math and physics models, and I'd like to use a Math library for things like Matrices. I'm using C#, and so I was looking for some libraries and found Math.NET. I'm under the impression, from past experience, that for math, using a robust and industry-approved third party library is much better than writing your own code. It seems good for many purposes, but it does not provide support for Quaternions, which I need to use as a type. Also, I need some functions in Vector and Matrix that also aren't provided, such as rotation matrices and vector rotation functions, and calculating cross products. At the same time, it provides a lot of functions/classes that I simply do not need, which might mean a lot of unnecessary bloat and complexity. At this rate, should I even bother using the library? Should I write my own math library? Or is it a better idea to stick to the third party library and somehow wrap around it? Perhaps I should make a subclass of the Matrix and Vector type of the library? But isn't that considered bad style? I've also tried looking for other libraries but unfortunately I couldn't find anything suitable.

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  • Parallel Class/Interface Hierarchy with the Facade Design Pattern?

    - by Mike G
    About a third of my code is wrapped inside a Facade class. Note that this isn't a "God" class, but actually represents a single thing (called a Line). Naturally, it delegates responsibilities to the subsystem behind it. What ends up happening is that two of the subsystem classes (Output and Timeline) have all of their methods duplicated in the Line class, which effectively makes Line both an Output and a Timeline. It seems to make sense to make Output and Timeline interfaces, so that the Line class can implement them both. At the same time, I'm worried about creating parallel class and interface structures. You see, there are different types of lines AudioLine, VideoLine, which all use the same type of Timeline, but different types of Output (AudioOutput and VideoOutput, respectively). So that would mean that I'd have to create an AudioOutputInterface and VideoOutputInterface as well. So not only would I have to have parallel class hierarchy, but there would be a parallel interface hierarchy as well. Is there any solution to this design flaw? Here's an image of the basic structure (minus the Timeline class, though know that each Line has-a Timeline): NOTE: I just realized that the word 'line' in Timeline might make is sound like is does a similar function as the Line class. They don't, just to clarify.

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  • TechEd 2010 Day Four: Learning how to help others learn

    - by BuckWoody
    I do quite a few presentations, and teach at the University of Washington, and also teach other classes. But I'm always learning from others how to help others learn. At events like TechEd I have access to some of the best speakers around, so I try to find out what they do that works. I attended a great session by allen White, in which he demonstrated a set of PowerShell scripts. He said that Dan Jones of the Microsoft Manageability team told him while he demonstrated a script he needed to provide some visual way to represent the process. Allen used one of the oldest visualizations around - a flowchart. It was the first time I'd seen one used to illustrate a PowerShell script, and it was very effective. I'm totally stealing the idea. All of us are teachers - we help others on our team understand what we're up to. Make sure you make notes for what you find effective in dealing with you, and then meld that into your own way of teaching. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • Earmarks of a Professional PHP Programmer

    - by Scotty C.
    I'm a 19 year old student who really REALLY enjoys programming, and I'm hoping to glean from your years of experience here. At present, I'm studying PHP every chance I get, and have been for about 3 years, although I've never taken any formal classes. I'd love to some day be a programmer full time, and make a good career of it. My question to you is this: What do you consider to be the earmarks or traits of a professional programmer? Mainly in the field of PHP, but other, more generalized qualifications are also more than welcome, as I think PHP is more of a hobbyist language and may not be the language of choice in the eyes of potential employers. Please correct me if I'm wrong. Above all, I don't want to wast time on something that isn't worth while. I'm currently feeling pretty confident in my knowledge of PHP as a language, and I know that I could build just about anything I need and have it "work", but I feel sorely lacking in design concepts and code structure. I can even write object oriented code, but in my personal opinion, that isn't worth a hill of beans if it isn't organized well. For this reason, I bought Matt Zandstra's book "PHP Objects, Patterns, and Practice" and have been reading that a little every day. Anyway, I'm starting to digress a little here, so back to the original question. What advice would you give to an aspiring programmer who wants to make an impact in this field? Also, on a side note, I've been working on a project with a friend of mine that would give a fairly good idea of where I'm at coding wise. I'm gonna give a link, I don't want anyone to feel as though I'm pushing or spamming here, so don't click it if you don't want to. But if you are interested on giving some feedback there as well, you can see the code on github. I'm known as The Craw there. https://github.com/PureChat/PureChat--Beta-/tree/

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  • Designing a plug-in system

    - by madflame991
    I'm working on a Java project and I would like to add a plug-in system. More precisely, I would like to let the user design his own module, pack it into a jar, leave it in a "plugins/" subfolder of my application and be done with it. I've managed to get a child classloader to instantiate objects of classes located in external jars, but now I'm facing a design dilemma: Say Joe makes a plug-in and he packs it in joeplugin.jar. I would really like Joe to have a class named "instantiation.Factory" and I would also like everyone to have this class with this exact location and name. (This factory class obviously implements a interface that I provide and through it I get what I want from the plug-in.) If Joe wouldn't be restricted in this way I would have to look into his entire jar for some class that implements my factory interface and I don't want to imagine how complicated things get. So my question is: should I enforce a strict naming convention for this single class? I have no idea how plug-in systems work.

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  • Mocking concrete class - Not recommended

    - by Mik378
    I've just read an excerpt of "Growing Object-Oriented Software" book which explains some reasons why mocking concrete class is not recommended. Here some sample code of a unit-test for the MusicCentre class: public class MusicCentreTest { @Test public void startsCdPlayerAtTimeRequested() { final MutableTime scheduledTime = new MutableTime(); CdPlayer player = new CdPlayer() { @Override public void scheduleToStartAt(Time startTime) { scheduledTime.set(startTime); } } MusicCentre centre = new MusicCentre(player); centre.startMediaAt(LATER); assertEquals(LATER, scheduledTime.get()); } } And his first explanation: The problem with this approach is that it leaves the relationship between the objects implicit. I hope we've made clear by now that the intention of Test-Driven Development with Mock Objects is to discover relationships between objects. If I subclass, there's nothing in the domain code to make such a relationship visible, just methods on an object. This makes it harder to see if the service that supports this relationship might be relevant elsewhere and I'll have to do the analysis again next time I work with the class. I can't figure out exactly what he means when he says: This makes it harder to see if the service that supports this relationship might be relevant elsewhere and I'll have to do the analysis again next time I work with the class. I understand that the service corresponds to MusicCentre's method called startMediaAt. What does he mean by "elsewhere"? The complete excerpt is here: http://www.mockobjects.com/2007/04/test-smell-mocking-concrete-classes.html

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  • Copy-and-Pasted Test Code: How Bad is This?

    - by joshin4colours
    My current job is mostly writing GUI test code for various applications that we work on. However, I find that I tend to copy and paste a lot of code within tests. The reason for this is that the areas I'm testing tend to be similar enough to need repetition but not quite similar enough to encapsulate code into methods or objects. I find that when I try to use classes or methods more extensively, tests become more cumbersome to maintain and sometimes outright difficult to write in the first place. Instead, I usually copy a big chunk of test code from one section and paste it to another, and make any minor changes I need. I don't use more structured ways of coding, such as using more OO-principles or functions. Do other coders feel this way when writing test code? Obviously I want to follow DRY and YAGNI principles, but I find that test code (automated test code for GUI testing anyway) can make these principles tough to follow. Or do I just need more coding practice and a better overall system of doing things? EDIT: The tool I'm using is SilkTest, which is in a proprietary language called 4Test. As well, these tests are mostly for Windows desktop applications, but I also have tested web apps using this setup as well.

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  • which style of member-access is preferable

    - by itwasntpete
    the purpose of oop using classes is to encapsulate members from the outer space. i always read that accessing members should be done by methods. for example: template<typename T> class foo_1 { T state_; public: // following below }; the most common doing that by my professor was to have a get and set method. // variant 1 T const& getState() { return state_; } void setState(T const& v) { state_ = v; } or like this: // variant 2 // in my opinion it is easier to read T const& state() { return state_; } void state(T const& v) { state_ = v; } assume the state_ is a variable, which is checked periodically and there is no need to ensure the value (state) is consistent. Is there any disadvantage of accessing the state by reference? for example: // variant 3 // do it by reference T& state() { return state_; } or even directly, if I declare the variable as public. template<typename T> class foo { public: // variant 4 T state; }; In variant 4 I could even ensure consistence by using c++11 atomic. So my question is, which one should I prefer?, Is there any coding standard which would decline one of these pattern? for some code see here

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  • How do I get others to see past my prior inexperience?

    - by Kevin
    My core question is how do I proceed from the following predicament. I will be honest with you, I wasted my College Experience. I slacked off and didn't take any of my comp sci classes that seriously, somehow i still got out with a 3.25 GPA. But truth be told I learned nothing. I befriended most of my professors who went pretty lenient on me in terms of grading. However, I basically came out of College knowing how to program a simple calculator in VB.Net. I was (to my great surprise) hired by a very large respected company in Denver as a Junior developer. Well the long and the short of it is that I knew so little about programming that I quickly became the office pariah and was almost fired due to my incompetence. It has been 8 months now and I feel I have learned some basic things and I am not as picked on as I used to be by the other developers. However, everyone hates me and the first few months have given the other developers a horrible perception of me. I am no longer afraid of code or learning, but I have put my self in the precarious position of being the scapegoat of our department. I hate going to work every day because no one there is my friend and pretty much everyone is hostile to me. What should I do? Any advice?

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  • Should components have sub-components in a component-based system like Artemis?

    - by Daniel Ingraham
    I am designing a game using Artemis, although this is more of philosophical question about component-based design in general. Let's say I have non-primitive data which applies to a given component (a Component "animal" may have qualities such as "teeth" or "diet"). There are three ways to approach this in data-driven design, as I see it: 1) Generate classes for these qualities using "traditional" OOP. I imagine this has negative implications for performance, as systems then must be made aware of these qualities in order to process them. It also seems counter to the overall philosophy of data-driven design. 2) Include these qualities as sub-components. This seems off, in that we are now confusing the role of components with that of entities. Moreover out of the box Artemis isn't capable of mapping these subcomponents onto their parent components. 3) Add "teeth", "diet", etc. as components to the overall entity alongside "animal". While this feels odd hierarchically, it may simply be a peculiarity of component-based systems. I suspect 3 is the correct way to think about things, but I was curious about other ideas.

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  • Using PDO with MVC

    - by mister martin
    I asked this question at stackoverflow and received no response (closed as duplicate with no answer). I'm experimenting with OOP and I have the following basic MVC layout: class Model { // do database stuff } class View { public function load($filename, $data = array()) { if(!empty($data)) { extract($data); } require_once('views/header.php'); require_once("views/$filename"); require_once('views/footer.php'); } } class Controller { public $model; public $view; function __construct() { $this->model = new Model(); $this->view = new View(); // determine what page we're on $page = isset($_GET['view']) ? $_GET['view'] : 'home'; $this->display($page); } public function display($page) { switch($page) { case 'home': $this->view->load('home.php'); break; } } } These classes are brought together in my setup file: // start session session_start(); require_once('Model.php'); require_once('View.php'); require_once('Controller.php'); new Controller(); Now where do I place my database connection code and how do I pass the connection onto the model? try { $db = new PDO('mysql:host='.DB_HOST.';dbname='.DB_DATABASE.'', DB_USERNAME, DB_PASSWORD); $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); } catch(PDOException $err) { die($err->getMessage()); } I've read about Dependency Injection, factories and miscellaneous other design patterns talking about keeping SQL out of the model, but it's all over my head using abstract examples. Can someone please just show me a straight-forward practical example?

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  • BCM2046B1 Bluetooth Dongle connection problem

    - by Andfoy
    Well i have a Blueooth dongle with an BCM2046 IC intrregated, my problem is that when i connect it, Ubuntu recognize it, but it don't work whe i try to scan or scan the PC from other device, i replaced the default Gnome Bluetooth manager and i installed Blueman, but the problem presists. The Bluetooth LED indicator appears to be "working". I'm using 11.10 Oneiric Ocelot hcitool dev: Devices: hci0 89:21:XX:XX:XX:XX lsusb: Bus 002 Device 003: ID 0a5c:4500 Broadcom Corp. BCM2046B1 USB 2.0 Hub (part of BCM2046 Bluetooth) Bus 002 Device 004: ID 0a5c:2100 Broadcom Corp. Bluetooth 2.0+eDR dongle hciconfig -a: hci0: Type: BR/EDR Bus: USB BD Address: 89:21:XX:XX:XX:XX ACL MTU: 1017:8 SCO MTU: 64:0 UP RUNNING PSCAN ISCAN RX bytes:1329 acl:0 sco:0 events:40 errors:0 TX bytes:671 acl:0 sco:0 commands:35 errors:0 Features: 0xff 0xff 0x8d 0xfe 0x9b 0xf9 0x00 0x80 Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3 Link policy: RSWITCH HOLD SNIFF PARK Link mode: SLAVE ACCEPT Name: 'ubuntu-0' Class: 0x4a0100 Service Classes: Networking, Capturing, Telephony Device Class: Computer, Uncategorized HCI Version: 2.0 (0x3) Revision: 0x4000 LMP Version: 2.0 (0x3) Subversion: 0x430e Manufacturer: Broadcom Corporation (15) Sorry for my English and thanks for any hints.

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  • The Enterprise Side of JavaFX: Part Two

    - by Janice J. Heiss
    A new article, part of a three-part series, now up on the front page of otn/java, by Java Champion Adam Bien, titled “The Enterprise Side of JavaFX,” shows developers how to implement the LightView UI dashboard with JavaFX 2. Bien explains that “the RESTful back end of the LightView application comes with a rudimentary HTML page that is used to start/stop the monitoring service, set the snapshot interval, and activate/deactivate the GlassFish monitoring capabilities.”He explains that “the configuration view implemented in the org.lightview.view.Browser component is needed only to start or stop the monitoring process or set the monitoring interval.”Bien concludes his article with a general summary of the principles applied:“JavaFX encourages encapsulation without forcing you to build models for each visual component. With the availability of bindable properties, the boundary between the view and the model can be reduced to an expressive set of bindable properties. Wrapping JavaFX components with ordinary Java classes further reduces the complexity. Instead of dealing with low-level JavaFX mechanics all the time, you can build simple components and break down the complexity of the presentation logic into understandable pieces. CSS skinning further helps with the separation of the code that is needed for the implementation of the presentation logic and the visual appearance of the application on the screen. You can adjust significant portions of an application's look and feel directly in CSS files without touching the actual source code.”Check out the article here.

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  • Best Architecture for ASP.NET WebForms Application

    - by stack man
    I have written an ASP.NET WebForms portal for a client. The project has kind of evolved rather than being properly planned and structured from the beginning. Consequently, all the code is mashed together within the same project and without any layers. The client is now happy with the functionality, so I would like to refactor the code such that I will be confident about releasing the project. As there seems to be many differing ways to design the architecture, I would like some opinions about the best approach to take. FUNCTIONALITY The portal allows administrators to configure HTML templates. Other associated "partners" will be able to display these templates by adding IFrame code to their site. Within these templates, customers can register and purchase products. An API has been implemented using WCF allowing external companies to interface with the system also. An Admin section allows Administrators to configure various functionality and view reports for each partner. The system sends out invoices and email notifications to customers. CURRENT ARCHITECTURE It is currently using EF4 to read/write to the database. The EF objects are used directly within the aspx files. This has facilitated rapid development while I have been writing the site but it is probably unacceptable to keep it like that as it is tightly coupling the db with the UI. Specific business logic has been added to partial classes of the EF objects. QUESTIONS The goal of refactoring will be to make the site scalable, easily maintainable and secure. 1) What kind of architecture would be best for this? Please describe what should be in each layer, whether I should use DTO's / POCO / Active Record pattern etc. 2) Is there a robust way to auto-generate DTO's / BOs so that any future enhancements will be simple to implement despite the extra layers? 3) Would it be beneficial to convert the project from WebForms to MVC?

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  • Is this an acceptable approach to undo/redo in Python?

    - by Codemonkey
    I'm making an application (wxPython) to process some data from Excel documents. I want the user to be able to undo and redo actions, even gigantic actions like processing the contents of 10 000 cells simultaneously. I Googled the topic, and all the solutions I could find involves a lot of black magic or is overly complicated. Here is how I imagine my simple undo/redo scheme. I write two classes - one called ActionStack and an abstract one called Action. Every "undoable" operation must be a subclass of Action and define the methods do and undo. The Action subclass is passed the instance of the "document", or data model, and is responsible for committing the operation and remembering how to undo the change. Now, every document is associated with an instance of the ActionStack. The ActionStack maintains a stack of actions (surprise!). Every time actions are undone and new actions are performed, all undone actions are removed for ever. The ActionStack will also automatically remove the oldest Action when the stack reaches the configurable maximum amount. I imagine the workflow would produce code looking something like this: class TableDocument(object): def __init__(self, table): self.table = table self.action_stack = ActionStack(history_limit=50) # ... def delete_cells(self, cells): self.action_stack.push( DeleteAction(self, cells) ) def add_column(self, index, name=''): self.action_stack.push( AddColumnAction(self, index, name) ) # ... def undo(self, count=1): self.action_stack.undo(count) def redo(self, count=1): self.action_stack.redo(count) Given that none of the methods I've found are this simple, I thought I'd get the experts' opinion before I go ahead with this plan. More specifically, what I'm wondering about is - are there any glaring holes in this plan that I'm not seeing?

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  • How should I load level data in java?

    - by Matthew G.
    I'm setting up my engine for a certain action/arcade game to have a set of commands that would look something like this. Set landscape to grass Create rocks at ... Create player at X, Y Set goal to "Get to point X Y" Spawn enemy at X, Y I'd then have each object knowing what it has to do, and acting on its own. I've been thinking about how to store this data. External data files could be parsed by a level class, and certain objects can be spawned through that. I could also create a base level class and extend it for each level, but that'd create a large amount of classes. Another idea is to have one level parser class, but have a case for each level. This would be extremely silly and bulky, but I mention it because I found that I did this at 2 AM last night. I'm finally getting why I have to plan out my inheritances, though. RIP project. I might be completely missing another option.

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  • Standards & compliances for secure web application development?

    - by MarkusK
    I am working with developers right now that write code the way they want and when i tell them to do it other way they respond that its just matter of preference how to do it and they have their way and i have mine. I am not talking about the formatting of code, but rather of way site is organized in classes and the way the utilize them. and the way they create functions and process forms etc. Their coding does not match my standards, but again they argue that its matter of preference and as long as goal achieved the can be different way's to do it. I agree but their way is proven to have bugs and we spend a lot of time going back and forth with them to fix all problems security or functionality, yet they still write same code no matter how many times i asked them to stop doing certain things. Now i am ready to dismiss them but friend of mine told me that he has same exact problem with freelance developers he work with. So i don't want to trade one bad apple for another. Question is is there some world wide (or at least europe and usa) accepted standard or compliance on how write secure web based applications. What application architecture should be for maintainable application. Is there are some general standard that can be used for any language ruby php or java govern security and functionality and quality of code? Or at least for PHP and MySQL i use for my website. So i can make them follow this strict standard and stop making excuses.

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  • The Correct Usage of DLLs with a DirectX Game?

    - by smoth190
    I'm using DirectX 10 (in C++) to make a game engine, and a test driver program on top of it. Now that I've written many messy rough drafts of an engine, I want to make the final (or sorta final) clean version. I choose to follow how I've seen other engines do it, and that's to have all the core nasty messy crap in a DLL, and then you can create games with just a few functions (well, not really :D). However, I'm unsure of what nasty messy crap to put in that DLL. I don't know about speed restrictions with DLLs. What I've done is put my winproc in the DLL, and have a class that takes the messages, and sends them through to the program using the DLL. Then that program does what it needs to do, and calls a rendering functions back in the DLL that renders everything. Only problem is it gets very low FPS (2, to be exact...). I've looked through everything, and I don't know if the way I'm using DLLs in causing this, or its something different. Whether it's the DLLs or not, I still want to know how to use a DLL correctly with a game engine. I like being neat, I hate having to see all those long names of DirectX classes. I use typedef a lot.

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  • What Does Installing Ubuntu "Alongside" Windows Entail?

    - by Soft Skeleton
    I recently posted a question about an error I was receiving trying to access Ubuntu from the boot menu. I am using Windows 7 and Ubuntu 12.x (I THINK because I haven't accessed it in over a year due to being unable to run an important program for one of my classes on Ubuntu). On another laptop, I partitioned the hard drive and installed Windows and Ubuntu on the partitions. On this laptop, I simply installed Ubuntu from Windows, picking the option "alongside Windows", and didn't partition my hard drive manually. I was under the impression "alongside" entailed that Ubuntu would partition my hard drive, and that if I were to return my Windows partition to factory settings it would not affect the Ubuntu partition. However, given my current problem, I am wondering if I was mistaken in this assumption? When installing Ubuntu from Windows, selecting "alongside" Windows as the option from the Ubuntu installer, does that simply install Ubuntu within the Windows partition and thus returning it to factory settings would wipe out anything I had on the Ubuntu OS as well? Ubuntu is still in the boot menu as an option, but when I try to access it it says the drive is "corrupt" and wubi is mentioned in the error. I additionally tried to download a program ran from Windows to investigate partitions and there were no sign of my Ubuntu partition viewable from Windows. Is it possible Windows just can't see it? Any insight, corrections or answers is appreciated.

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  • Can higher-order functions in FP be interpreted as some kind of dependency injection?

    - by Giorgio
    According to this article, in object-oriented programming / design dependency injection involves a dependent consumer, a declaration of a component's dependencies, defined as interface contracts, an injector that creates instances of classes that implement a given dependency interface on request. Let us now consider a higher-order function in a functional programming language, e.g. the Haskell function filter :: (a -> Bool) -> [a] -> [a] from Data.List. This function transforms a list into another list and, in order to perform its job, it uses (consumes) an external predicate function that must be provided by its caller, e.g. the expression filter (\x -> (mod x 2) == 0) [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] selects all even numbers from the input list. But isn't this construction very similar to the pattern illustrated above, where the filter function is the dependent consumer, the signature (a -> Bool) of the function argument is the interface contract, the expression that uses the higher-order is the injector that, in this particular case, injects the implementation (\x -> (mod x 2) == 0) of the contract. More in general, can one relate higher-order functions and their usage pattern in functional programming to the dependency injection pattern in object-oriented languages? Or in the inverse direction, can dependency injection be compared to using some kind of higher-order function?

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  • What alternative is better to diagram this scenario?

    - by Mosty Mostacho
    I was creating and discussing a class diagram with a partner of mine. To simplify things, I've modify the real domain we're working on and made up the following diagram: Basically, a company works on constructions that are quite different one from each other but are still constructions. Note I've added one field for each class but there should be many more. Now, I thought this was the way to go but my partner told me that if in the future new construction classes appear we would have to modify the Company class, which is correct. So the new proposed class diagram would be this: Now I've been wondering: Should the fact that in no place of the application will there be mixed lists of planes and bridges affect the design in any way? When we have to list only planes for a company, how are we supposed to distinguish them from the other elements in the list without checking for their class names? Related to the previous question, is it correct to assume that this type of diagram should be high-level and this is something it shouldn't matter at this stage but rather be thought and decided at implementation time? Any comment will be appreciated.

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  • TechEd 2010 Day Four: Learning how to help others learn

    - by BuckWoody
    I do quite a few presentations, and teach at the University of Washington, and also teach other classes. But I'm always learning from others how to help others learn. At events like TechEd I have access to some of the best speakers around, so I try to find out what they do that works. I attended a great session by allen White, in which he demonstrated a set of PowerShell scripts. He said that Dan Jones of the Microsoft Manageability team told him while he demonstrated a script he needed to provide some visual way to represent the process. Allen used one of the oldest visualizations around - a flowchart. It was the first time I'd seen one used to illustrate a PowerShell script, and it was very effective. I'm totally stealing the idea. All of us are teachers - we help others on our team understand what we're up to. Make sure you make notes for what you find effective in dealing with you, and then meld that into your own way of teaching. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • "Programming error" exceptions - Is my approach sound?

    - by Medo42
    I am currently trying to improve my use of exceptions, and found the important distinction between exceptions that signify programming errors (e.g. someone passed null as argument, or called a method on an object after it was disposed) and those that signify a failure in the operation that is not the caller's fault (e.g. an I/O exception). As far as I understand, it makes little sense for an immediate caller to actually handle programming error exceptions, he should instead assure that the preconditions are met. Only "outer" exception handlers at task boundaries should catch them, so they can keep the system running if a task fails. In order to ensure that client code can cleanly catch "failure" exceptions without catching error exceptions by mistake, I create my own exception classes for all failure exceptions now, and document them in the methods that throw them. I would make them checked exceptions in Java. Now I have a few questions: Before, I tried to document all exceptions that a method could throw, but that sometimes creates an unwiedly list that needs to be documented in every method up the call chain until you can show that the error won't happen. Instead, I document the preconditions in the summary / parameter descriptions and don't even mention what happens if they are not met. The idea is that people should not try to catch these exceptions explicitly anyway, so there is no need to document their types. Would you agree that this is enough? Going further, do you think all preconditions even need to be documented for every method? For example, calling methods in IDisposable objects after calling Dispose is an error, but since IDisposable is such a widely used interface, can I just assume a programmer will know this? A similar case is with reference type parameters where passing null makes no conceivable sense: Should I document "non-null" anyway? IMO, documentation should only cover things that are not obvious, but I am not sure where "obvious" ends.

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