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  • Why does TDD work?

    - by CesarGon
    Test-driven development (TDD) is big these days. I often see it recommended as a solution for a wide range of problems here in Programmers SE and other venues. I wonder why it works. From an engineering point of view, it puzzles me for two reasons: The "write test + refactor till pass" approach looks incredibly anti-engineering. If civil engineers used that approach for bridge construction, or car designers for their cars, for example, they would be reshaping their bridges or cars at very high cost, and the result would be a patched-up mess with no well thought-out architecture. The "refactor till pass" guideline is often taken as a mandate to forget architectural design and do whatever is necessary to comply with the test; in other words, the test, rather than the user, sets the requirement. In this situation, how can we guarantee good "ilities" in the outcomes, i.e. a final result that is not only correct but also extensible, robust, easy to use, reliable, safe, secure, etc.? This is what architecture usually does. Testing cannot guarantee that a system works; it can only show that it doesn't. In other words, testing may show you that a system contains defects if it fails a test, but a system that passes all tests is not safer than a system that fails them. Test coverage, test quality and other factors are crucial here. The false safe feelings that an "all green" outcomes produces to many people has been reported in civil and aerospace industries as extremely dangerous, because it may be interepreted as "the system is fine", when it really means "the system is as good as our testing strategy". Often, the testing strategy is not checked. Or, who tests the tests? I would like to see answers containing reasons why TDD in software engineering is a good practice, and why the issues that I have explained above are not relevant (or not relevant enough) in the case of software. Thank you.

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  • C# Role Provider for multiple applications

    - by Juventus18
    I'm making a custom RoleProvider that I would like to use across multiple applications in the same application pool. For the administration of roles (create new role, add users to role, etc..) I would like to create a master application that I could login to and set the roles for each additional application. So for example, I might have AppA and AppB in my organization, and I need to make an application called AppRoleManager that can set roles for AppA and AppB. I am having troubles implementing my custom RoleProvider because it uses an initialize method that gets the application name from the config file, but I need the application name to be a variable (i.e. "AppA" or "AppB") and passed as a parameter. I thought about just implementing the required methods, and then also having additional methods that pass application name as a parameter, but that seems clunky. i.e. public override CreateRole(string roleName) { //uses the ApplicationName property of this, which is set in web.config //creates role in db } public CreateRole(string ApplicationName, string roleName) { //creates role in db with specified params. } Also, I would prefer if people were prevented from calling CreateRole(string roleName) because the current instance of the class might have a different applicationName value than intended (what should i do here? throw NotImplementedException?). I tried just writing the class without inheriting RoleProvider. But it is required by the framework. Any general ideas on how to structure this project? I was thinking make a wrapper class that uses the role provider, and explicitly sets the application name before (and after) and calls to the provider something like this: static class RoleProviderWrapper { public static CreateRole(string pApplicationName, string pRoleName) { Roles.Provider.ApplicationName = pApplicationName; Roles.Provider.CreateRole(pRoleName); Roles.Provider.ApplicationName = "Generic"; } } is this my best-bet?

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  • XNA - Saving Game Data without TypeWriter?

    - by Zabby
    In the past, I've had some trouble with reading and writing content for XNA. I think I'm firmly set on this tutorial which sets up a four project structure (Game, Content, Library, Pipeline Extension) for the solution that other websites suggest, too. The options it offers for content reading seem great. But problem! This tutorial (and all others I've found) have stated that the Content Pipeline Extension Project is not distributed with the game, which is fine in itself, but this is combined with the fact that any content writing objects are placed in this non-distributable library. The ability to actually write content of an already existing type (save game files, namely) is pretty critical to the project I'm trying to make. I've already learned the hard way you simply can't place the Content Pipeline reference in another project besides the extension for easier access to the intermediate deserializer. Is there another object I can access for writing save game data? Am I actually, despite the warnings of this tutorial, able to use the TypeWriter outside of the Content Pipeline Extension Project? Or is there a third option I am missing here?

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  • SQL Server Interview Questions

    - by Rodney Vinyard
    User-Defined Functions Scalar User-Defined Function A Scalar user-defined function returns one of the scalar data types. Text, ntext, image and timestamp data types are not supported. These are the type of user-defined functions that most developers are used to in other programming languages. Table-Value User-Defined Function An Inline Table-Value user-defined function returns a table data type and is an exceptional alternative to a view as the user-defined function can pass parameters into a T-SQL select command and in essence provide us with a parameterized, non-updateable view of the underlying tables. Multi-statement Table-Value User-Defined Function A Multi-Statement Table-Value user-defined function returns a table and is also an exceptional alternative to a view as the function can support multiple T-SQL statements to build the final result where the view is limited to a single SELECT statement. Also, the ability to pass parameters into a T-SQL select command or a group of them gives us the capability to in essence create a parameterized, non-updateable view of the data in the underlying tables. Within the create function command you must define the table structure that is being returned. After creating this type of user-defined function, I can use it in the FROM clause of a T-SQL command unlike the behavior found when using a stored procedure which can also return record sets.

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  • What is the evidence that an API has exceeded its orthogonality in the context of types?

    - by hawkeye
    Wikipedia defines software orthogonality as: orthogonality in a programming language means that a relatively small set of primitive constructs can be combined in a relatively small number of ways to build the control and data structures of the language. The term is most-frequently used regarding assembly instruction sets, as orthogonal instruction set. Jason Coffin has defined software orthogonality as Highly cohesive components that are loosely coupled to each other produce an orthogonal system. C.Ross has defined software orthogonality as: the property that means "Changing A does not change B". An example of an orthogonal system would be a radio, where changing the station does not change the volume and vice-versa. Now there is a hypothesis published in the the ACM Queue by Tim Bray - that some have called the Bánffy Bray Type System Criteria - which he summarises as: Static typings attractiveness is a direct function (and dynamic typings an inverse function) of API surface size. Dynamic typings attractiveness is a direct function (and static typings an inverse function) of unit testing workability. Now Stuart Halloway has reformulated Banfy Bray as: the more your APIs exceed orthogonality, the better you will like static typing My question is: What is the evidence that an API has exceeded its orthogonality in the context of types? Clarification Tim Bray introduces the idea of orthogonality and APIs. Where you have one API and it is mainly dealing with Strings (ie a web server serving requests and responses), then a uni-typed language (python, ruby) is 'aligned' to that API - because the the type system of these languages isn't sophisticated, but it doesn't matter since you're dealing with Strings anyway. He then moves on to Android programming, which has a whole bunch of sensor APIs, which are all 'different' to the web server API that he was working on previously. Because you're not just dealing with Strings, but with different types, the API is non-orthogonal. Tim's point is that there is a empirical relationship between your 'liking' of types and the API you're programming against. (ie a subjective point is actually objective depending on your context).

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  • Packages not showing up in created APT repository

    - by David
    I created an APT repository using deb-scanpackages, and it seemed to go well. When I did a apt-get update on another server, the Packages.gz file was retrieved, and all seemed well - until I went to search for the packages contained in that repository (all packages are created locally). Several recommendations suggested reprepro; I tried that. Same result - except I had to rebuild the packages with the Priority and Section lines in the control file (nothing says this anywhere). The reprepro utility also generates a complicated directory structure which required rewriting the repository entry on the requesting server. I then found that the arch directory referenced i386 and not amd64 (which was requested by the requesting server). Is it possible that the AMD64 system isn't seeing packages compiled for i386? Searching the *Packages files in /var/lib/apt/lists show that the only packages for i386 are those I added (the other files are for the server - Ubuntu 10.04.2 LTS). The server the packages were built on is Ubuntu 10.04.2 LTS i686; the requesting server is x86_64. I found some discussion at the Debian AMD64FAQ but it claims to be obsolete. It makes mention of an extended syntax for repository listings for APT, and a command dpkg-subarchitecture - neither of which work on the local AMD64 server. Do I have to build two different sets of packages?

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  • Is the difference between sudo and gksu the same as the difference between sudo -i and sudo -s?

    - by fred.bear
    Is the difference between sudo cmd and gksu cmd, the same as the difference between starting a shell with sudo -i and sudo -s? ... or put another way, Is sudo cmd the same as sudo -i cmd and gksu cmd the same as sudo -s cmd? EDIT: Based on what I read on an Ubuntu Documentation Page where it says: You should never use normal sudo to start graphical applications as root. You should use gksudo (kdesudo on Kubuntu) to run such programs. gksudo sets HOME=~root, and copies .Xauthority to a tmp directory. This prevents files in your home directory becoming owned by root. (AFAICT, this is all that's special about the environment of the started process with gksudo vs. sudo). The "AFAICT" doen't really give me full confidence that there is nothing more to it. (..a belated UPDATE: I tested his commemnt today (2 months later) about: "This prevents files in your home directory becoming owned by root." All files I created via sudo/gksu were all owned by "root", and the group was "root".) I've read parts of the info sudo and noticed the -i and -s seem to be doing the same thing as the AFAICT environment issue... but I hit overload.. so I've asked my question here. PS.. My question is not about sudo vs gksu .. It is more about: Is gksu the same as sudo -s .. and if not, how do they differ?

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  • What to choose for a multilingual site with support for Markdown and commenting

    - by Kent
    I want to publish articles at a multilingual site. I want to be able to write an article in two languages and have them available on separate URLs: thesite.foo/english-breakfast thesite.com/engelsk-frukost If the users web browser is set to English I'd like to show a small notice at the top of the Swedish version with a link to the English one. The link should have an appropriate rel attribute for a translation (search for hreflang at http://diveintohtml5.org/semantics.html). There should be a way to list all articles belonging to these sets: Swedish only, English only, Swedish versions + English only, English versions + Swedish only. I'd like to publish these as four RSS-feeds. And I would like to have two versions of the main site, one in Swedish (showing Swedish versions + English only) and one in English (showing English versions). I shall be able to write the articles using Markdown, as that is the formatting language I find most convenient. There should be a way for users to comment. And some kind of way for me to protect myself against comment spam. I am leaning towards learning Drupal. I suspect I'll have to code this behavior myself as a module. To be frank I'd rather work with Java. Is Drupal the way to go? Or is there something more suitable for this project?

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  • Oracle Magazine: Getting started with SQL Analytics

    - by KLaker
    I am currently working on a series of podcasts covering the broad categories of our SQL analytical functions and features and while I was doing some research I came across of series of four articles in the Oracle Magazine. This series of article is written by Melanie Caffrey who is a senior development manager at Oracle. She is a coauthor of Expert PL/SQL Practices for Oracle Developers and DBAs (Apress, 2011) and Expert Oracle Practices: Oracle Database Administration from the Oak Table (Apress, 2010). The four articles are under the banner "Technology: SQL 101" and parts 9, 10, 11 and 12 cover SQL analytics. Here are the links to the four articles: Jan 2013 Having Sums, Averages, and Other Grouped Data March 2013 A Window into the World of Analytic Functions May 2013 Leading Ranks and Lagging Percentages: Analytic Functions, Continued July 2013 Pivotal Access to Your Data: Analytic Functions, Concluded The articles cover topics such as GROUP BY, SUM, AVG, HAVING, window functions, RANK, FIRST, LAST, LAG, LEAD etc.   The great news is that  you can try out the examples in this series. All you need is access to an Oracle Database instance. All the schemas, data sets and SQL statements that you will need can be downloaded from a link included in the January article.    I hope you find this series of articles useful.

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  • Algorithm to figure out appointment times?

    - by Rachel
    I have a weird situation where a client would like a script that automatically sets up thousands of appointments over several days. The tricky part is the appointments are for a variety of US time zones, and I need to take the consumer's local time zone into account when generating appointment dates and times for each record. Appointment Rules: Appointments should be set from 8AM to 8PM Eastern Standard Time, with breaks from 12P-2P and 4P-6P. This leaves a total of 8 hours per day available for setting appointments. Appointments should be scheduled 5 minutes apart. 8 hours of 5-minute intervals means 96 appointments per day. There will be 5 users at a time handling appointments. 96 appointments per day multiplied by 5 users equals 480, so the maximum number of appointments that can be set per day is 480. Now the tricky requirement: Appointments are restricted to 8am to 8pm in the consumer's local time zone. This means that the earliest time allowed for each appointment is different depending on the consumer's time zone: Eastern: 8A Central: 9A Mountain: 10A Pacific: 11A Alaska: 12P Hawaii or Undefined: 2P Arizona: 10A or 11A based on current Daylight Savings Time Assuming a data set can be several thousand records, and each record will contain a timezone value, is there an algorithm I could use to determine a Date and Time for every record that matches the rules above?

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  • LCD? LED? Plasma? The How-To Geek Guide to HDTV Technology

    - by Eric Z Goodnight
    With image technology progressing faster than ever, High-Def has become the standard, giving TV buyers more options at cheaper prices. But what’s different in all these confusing TVs, and what should you know before buying one? If you’re considering buying a television this Holiday season for a loved one (or simply for yourself), it can be a big help to know what to look for. Take a look to find out what sets HD televisions apart, learn some of the confusing jargon associated with them, and see a comparison of four of the types of HDTVs commonly sold today. Latest Features How-To Geek ETC The How-To Geek Guide to Learning Photoshop, Part 8: Filters Get the Complete Android Guide eBook for Only 99 Cents [Update: Expired] Improve Digital Photography by Calibrating Your Monitor The How-To Geek Guide to Learning Photoshop, Part 7: Design and Typography How to Choose What to Back Up on Your Linux Home Server How To Harmonize Your Dual-Boot Setup for Windows and Ubuntu Hang in There Scrat! – Ice Age Wallpaper How Do You Know When You’ve Passed Geek and Headed to Nerd? On The Tip – A Lamborghini Theme for Chrome and Iron What if Wile E. Coyote and the Road Runner were Human? [Video] Peaceful Winter Cabin Wallpaper Store Tabs for Later Viewing in Opera with Tab Vault

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  • Beyond S&OP: Integrated Business Planning

    - by Paul Homchick
    In most corporations, planning is done at the department level — leaving disconnects and gaps across different departments. Finance sets revenue and profit goals with minimum validation from Manufacturing that the company has the resources, material, capacity, or demand to reach these goals. On the operations side, Manufacturing is developing plans to balance demand and supply but seldom knows if the resulting "plan" will meet the budgets on which the company's revenue and profit goals are based. The Sales department agrees to quotas that meet Finance's revenue goals without a complete understanding of what manufacturing can deliver. Integrated Business Planning (IBP) bridges these gaps in corporate planning systems. Integrated Business Planning integrates the financial planning provided by EPM systems with operations planning provided by Sales and Operations Planning solutions. This means that revenue goals and budgets are validated against a bottom-up operating plan, and that the operating plan is reconciled against financial goals. When detailed changes are made to the operations plan, planners can immediately see the big picture impact of the changes. IBP also addresses one the CFO's big concerns—the reliability of the revenue forecast. Operating plans are updated daily or weekly from a precise forecast based on current market conditions. These updated plans are then made available so that financial analysts are working with data that best represents what is going to happen - not what they projected would happen based on last quarter's data. For a discussion in more depth, see my article: Improve Reliability of Financial Forecasts with Integrated Business Planning in Supply & Demand Chain-Executive Magazine.

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  • Beyond S&OP: Integrated Business Planning

    - by Paul Homchick
    In most corporations, planning is done at the department level — leaving disconnects and gaps across different departments. Finance sets revenue and profit goals with minimum validation from Manufacturing that the company has the resources, material, capacity, or demand to reach these goals. On the operations side, Manufacturing is developing plans to balance demand and supply but seldom knows if the resulting "plan" will meet the budgets on which the company's revenue and profit goals are based. The Sales department agrees to quotas that meet Finance's revenue goals without a complete understanding of what manufacturing can deliver. Integrated Business Planning (IBP) bridges these gaps in corporate planning systems. Integrated Business Planning integrates the financial planning provided by EPM systems with operations planning provided by Sales and Operations Planning solutions. This means that revenue goals and budgets are validated against a bottom-up operating plan, and that the operating plan is reconciled against financial goals. When detailed changes are made to the operations plan, planners can immediately see the big picture impact of the changes. IBP also addresses one the CFO's big concerns—the reliability of the revenue forecast. Operating plans are updated daily or weekly from a precise forecast based on current market conditions. These updated plans are then made available so that financial analysts are working with data that best represents what is going to happen - not what they projected would happen based on last quarter's data. For a discussion in more depth, see my article: Improve Reliability of Financial Forecasts with Integrated Business Planning in Supply & Demand Chain-Executive Magazine.

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  • Public Speaking in software development.

    - by mummey
    Greetings my fellow cubicle dwellers. I've found my role gradually change from "feature-maintainer" to "feature-developer". While much of the former would consist of fixing and/or updating an existing feature (and quietly grumbling about it's implementation with complete naiveté), in this new role I find: Have to communicate with immediate management to define the development requirements to turnaround the new feature Have to communicate with design to determine the user requirements of the new feature Have to communicate with QA to determine test sets for the new feature, as well as it's current state during development. Have to communicate with producers/project-managers to define remaining turnaround time as well as updates in development requirements. and finally, have to occasionally communicate with upper-management to defend the new feature and demonstrate it's minimized risk to the upcoming release. The last item is key here, and this took me a couple occasions to completely realize. In all, though, it becomes very apparent that communication skills ARE important, even or especially as such for developers who feel they 'own' the feature they're working on. All of this said, I recognize it's importance and would like to improve my skills in this area further. I enjoy one-on-one communication but find I tend to stutter a bit when speaking to any group larger than a few people I know well. Where can I find good resources to improve my own communication skills?

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  • Tips for switching jobs and moving into web based programming?

    - by JerryC
    I graduated in 2006 with a computer science degree and got solid grades (3.5 overall 3.8 in my major) For the past 4.5 years I've been working as a Software Engineer doing primarily rich client development. Most of my experience is with Java, Swing and C++. I've done a lot of network programming and I have acquired some skill working & debugging in distributed environments. I would like to switch jobs and move into a role where I can get exposure to some new technologies and frameworks. I would like to move into a more web development role but I find my lack of web development experience is hurting me. 90% of the jobs I see advertised are looking for one of two skill sets: 1) Stereotypical server side Java web developer. Experience with Spring, Hibernate, J2EE, etc. 2) Stereotypical front end web developer. Experience with Javascript, jQuery, HTML5, GWT, CSS, etc I find most of these companies are looking really specifically for this experience and they are not willing to take on good programmers/ CS fundamental guys who lack experience with this stuff. I would love to get a job doing stuff like this, but have my skills become out of date and unmarketable? Any opinions on ways to sell myself to help get a new position?

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  • Developing Ext JS Charts in NetBeans IDE

    - by Geertjan
    I took my first tentative steps into the world of Ext JS charts today, in NetBeans IDE 7.4. Click to enlarge the image. I will make a screencast soon showing how charts such as the above can be created with NetBeans IDE and Ext JS. Setting up Ext JS is easy in NetBeans IDE because there's a JavaScript library browser, by means of which I can browse for the Ext JS libraries that I need and then NetBeans IDE sets up the project for me. The JavaScript code shown above comes directly from here: http://www.quizzpot.com/courses/learning-ext-js-3/articles/chart-series The index.html is as follows: <html> <head> <title>TODO supply a title</title> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width"> <link rel="stylesheet" href="js/libs/extjs/resources/css/ext-all.css"/> <script src="js/libs/ext-core/ext-core.js"></script> <script src="js/libs/extjs/adapter/ext/ext-base-debug.js"></script> <script src="js/libs/extjs/ext-all-debug.js"></script> <script src="app.js"></script> </head> <body> </body> </html> More info on Ext JS: http://docs.sencha.com/extjs/4.1.3/ By the way, quite a few other articles are out there on Ext JS and NetBeans IDE, such as these, which I will be learning from during the coming days: http://netbeans.dzone.com/extjs-rest-netbeans http://netbeans.dzone.com/articles/create-your-first-extjs-4 http://netbeans.dzone.com/articles/mixing-extjs-json-p-and-java

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  • OBIEE Version 11.1.1.7.140527 Now Released

    - by Lia Nowodworska - Oracle
    (in via Martin) The Oracle Business Intelligence Enterprise Edition (OBIEE) 11g 11.1.1.7.140527 Bundle Patch is now available to download via My Oracle Support | Patches & Updates. This is provided as single Bundle Patch  Patch  18507268 and is comprised of the following: Patch 16913445 - 1 of 8 Oracle BI Installer (BIINST) Patch 18507640 - 2 of 8 Oracle BI Publisher (BIP) Patch 18657616 - 3 of 8 EPM Components Installed from BI Installer 11.1.1.7.0 (BIFNDNEPM) Patch 18507802 - 4 of 8 Oracle BI Server (BIS) Patch 18507778 - 5 of 6 Oracle BI Presentation Services (BIPS) Patch 17300045 - 6 of 8 Oracle Real-Time Decisions (RTD) Patch 16997936 - 7 of 8 Oracle BI ADF Components (BIADFCOMPS) Patch 18507823 - 8 of 8 Oracle BI Platform Client Installers and MapViewer NOTE: Also required to be downloaded: Patch 16569379 - Dynamic Monitoring Service patch This patch set is available for all customers who are using Oracle Business Intelligence Enterprise Edition 11.1.1.7.0, 11.1.1.7.1, 11.1.1.7.131017, 11.1.1.7.140114, 11.1.1.7.140225 and 11.1.1.7.140415 NOTE: It is also available for Exalytics customers who have applied the Exalytics PS3 patch. For more information refer to: OBIEE 11g 11.1.1.7.140527 Bundle Patch is Available for OBIEE ( Doc ID 1676798.1 ) The OBIEE Suite Bundle Patches are cumulative - the content of the previous 11.1.1.7.x bundle patches are included in this latest bundle patch. Ensure to review the Readme documentation for further important patch information.  This is available via the My Oracle Support | Patches & Updates screen when downloading. Keep up to-date with the latest OBIEE Patches and Patch Set Updates by visiting OBIEE 11g: Required and Recommended Patches and Patch Sets (Doc ID 1488475.1 )

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  • How to balance a non-symmetric "extension" based game?

    - by Klaim
    Most strategy games have fixed units and possible behaviours. However, think of a game like Magic The Gathering : each card is a set of rules. Regularly, new sets of card types are created. I remember that the firsts editions of the game have been said to be prohibited in official tournaments because the cards were often too powerful. Later extensions of the game provided more subtle effects/rules in cards and they managed to balance the game apparently effectively, even if there is thousands of different cards possible. I'm working on a strategy game that is a bit in the same position : every units are provided by extensions and the game is thought to be extended for some years, at least. The effects variety of the units are very large even with some basic design limitations set to be sure it's manageable. Each player choose a set of units to play with (defining their global strategy) before playing (like chooseing a themed deck of Magic cards). As it's a strategy game (you can think of Magic as a strategy game too in some POV), it's essentially skirmish based so the game have to be fair, even if the players don't choose the same units before starting to play. So, how do you proceed to balance this type of non-symmetric (strategy) game when you know it will always be extended? For the moment, I'm trying to apply those rules but I'm not sure it's right because I don't have enough design experience to know : each unit would provide one unique effect; each unit should have an opposite unit that have an opposite effect that would cancel each others; some limitations based on the gameplay; try to get a lot of beta tests before each extension release? Looks like I'm in the most complex case?

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  • OOP concept: is it possible to update the class of an instantiated object?

    - by Federico
    I am trying to write a simple program that should allow a user to save and display sets of heterogeneous, but somehow related data. For clarity sake, I will use a representative example of vehicles. The program flow is like this: The program creates a Garage object, which is basically a class that can contain a list of vehicles objects Then the users creates Vehicles objects, these Vehicles each have a property, lets say License Plate Nr. Once created, the Vehicle object get added to a list within the Garage object --Later on--, the user can specify that a given Vehicle object is in fact a Car object or a Truck object (thus giving access to some specific attributes such as Number of seats for the Car, or Cargo weight for the truck) At first sight, this might look like an OOP textbook question involving a base class and inheritance, but the problem is more subtle because at the object creation time (and until the user decides to give more info), the computer doesn't know the exact Vehicle type. Hence my question: how would you proceed to implement this program flow? Is OOP the way to go? Just to give an initial answer, here is what I've came up until now. There is only one Vehicle class and the various properties/values are handled by the main program (not the class) through a dictionary. However, I'm pretty sure that there must be a more elegant solution (I'm developing using VB.net): Public Class Garage Public GarageAdress As String Private _ListGarageVehicles As New List(Of Vehicles) Public Sub AddVehicle(Vehicle As Vehicles) _ListGarageVehicles.Add(Vehicle) End Sub End Class Public Class Vehicles Public LicensePlateNumber As String Public Enum VehicleTypes Generic = 0 Car = 1 Truck = 2 End Enum Public VehicleType As VehicleTypes Public DictVehicleProperties As New Dictionary(Of String, String) End Class NOTE that in the example above the public/private modifiers do not necessarily reflect the original code

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  • Calculating collision force with AfterCollision/NormalImpulse is unreliable when IgnoreCCD = false?

    - by Michael
    I'm using Farseer Physics Engine 3.3.1 in a very simple XNA 4 test game. (Note: I'm also tagging this Box2D, because Farseer is a direct port of Box2D and I will happily accept Box2D answers that solve this problem.) In this game, I'm creating two bodies. The first body is created using BodyFactory.CreateCircle and BodyType.Dynamic. This body can be moved around using the keyboard (which sets Body.LinearVelocity). The second body is created using BodyFactory.CreateRectangle and BodyType.Static. This body is static and never moves. Then I'm using this code to calculate the force of collision when the two bodies collide: staticBody.FixtureList[0].AfterCollision += new AfterCollisionEventHandler(AfterCollision); protected void AfterCollision(Fixture fixtureA, Fixture fixtureB, Contact contact) { float maxImpulse = 0f; for (int i = 0; i < contact.Manifold.PointCount; i++) maxImpulse = Math.Max(maxImpulse, contact.Manifold.Points[i].NormalImpulse); // maxImpulse should contain the force of the collision } This code works great if both of these bodies are set to IgnoreCCD=true. I can calculate the force of collision between them 100% reliably. Perfect. But here's the problem: If I set the bodies to IgnoreCCD=false, that code becomes wildly unpredictable. AfterCollision is called reliably, but for some reason the NormalImpulse is 0 about 75% of the time, so only about one in four collisions is registered. Worse still, the NormalImpulse seems to be zero for completely random reasons. The dynamic body can collide with the static body 10 times in a row in virtually exactly the same way, and only 2 or 3 of the hits will register with a NormalImpulse greater than zero. Setting IgnoreCCD=true on both bodies instantly solves the problem, but then I lose continuous physics detection. Why is this happening and how can I fix it? Here's a link to a simple XNA 4 solution that demonstrates this problem in action: http://www.mediafire.com/?a1w242q9sna54j4

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  • Sort algorithms that work on large amount of data

    - by Giorgio
    I am looking for sorting algorithms that can work on a large amount of data, i.e. that can work even when the whole data set cannot be held in main memory at once. The only candidate that I have found up to now is merge sort: you can implement the algorithm in such a way that it scans your data set at each merge without holding all the data in main memory at once. The variation of merge sort I have in mind is described in this article in section Use with tape drives. I think this is a good solution (with complexity O(n x log(n)) but I am curious to know if there are other (possibly faster) sorting algorithms that can work on large data sets that do not fit in main memory. EDIT Here are some more details, as required by the answers: The data needs to be sorted periodically, e.g. once in a month. I do not need to insert a few records and have the data sorted incrementally. My example text file is about 1 GB UTF-8 text, but I wanted to solve the problem in general, even if the file were, say, 20 GB. It is not in a database and, due to other constraints, it cannot be. The data is dumped by others as a text file, I have my own code to read this text file. The format of the data is a text file: new line characters are record separators. One possible improvement I had in mind was to split the file into files that are small enough to be sorted in memory, and finally merge all these files using the algorithm I have described above.

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  • Current SPARC Architectures

    - by Darryl Gove
    Different generations of SPARC processors implement different architectures. The architecture that the compiler targets is controlled implicitly by the -xtarget flag and explicitly by the -arch flag. If an application targets a recent architecture, then the compiler gets to play with all the instructions that the new architecture provides. The downside is that the application won't work on older processors that don't have the new instructions. So for developer's there is a trade-off between performance and portability. The way we have solved this in the compiler is to assume a "generic" architecture, and we've made this the default behaviour of the compiler. The only flag that doesn't make this assumption is -fast which tells the compiler to assume that the build machine is also the deployment machine - so the compiler can use all the instructions that the build machine provides. The -xtarget=generic flag tells the compiler explicitly to use this generic model. We work hard on making generic code work well across all processors. So in most cases this is a very good choice. It is also of interest to know what processors support the various architectures. The following Venn diagram attempts to show this: A textual description is as follows: The T1 and T2 processors, in addition to most other SPARC processors that were shipped in the last 10+ years supported V9b, or sparcvis2. The SPARC64 processors from Fujitsu, used in the M-series machines, added support for the floating point multiply accumulate instruction in the sparcfmaf architecture. Support for this instruction also appeared in the T3 - this is called sparcvis3 Later SPARC64 processors added the integer multiply accumulate instruction, this architecture is sparcima. Finally the T4 includes support for both the integer and floating point multiply accumulate instructions in the sparc4 architecture. So the conclusion should be: Floating point multiply accumulate is supported in both the T-series and M-series machines, so it should be a relatively safe bet to start using it. The T4 is a very good machine to deploy to because it supports all the current instruction sets.

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  • What is the correct way to restart udev in Ubuntu?

    - by zerkms
    I've changed the name of my eth1 interface to eth0. How to ask udev now to re-read the config? service udev restart and udevadm control --reload-rules don't help. So is there any valid way except of rebooting? (yes, reboot helps with this issue) UPD: yes, I know I should prepend the commands with sudo, but either one I posted above changes nothing in ifconfig -a output: I still see eth1, not eth0. UPD 2: I just changed the NAME property of udev-rule line. Don't know any reason for this to be ineffective. There is no any error in executing of both commands I've posted above, but they just don't change actual interface name in ifconfig -a output. If I perform reboot - then interface name changes as expected. UPD 3: let I explain all the case better ;-) For development purposes I write some script that clones virtual machines (VirtualBox-driven) and pre-sets them up in some way. So I perform a command to clone VM, start it and as long as network interface MAC is changed - udev adds the second rule to network persistent rules. Right after machine is booted for the first time there are 2 rules: eth0, which does not exist, as long as it existed in the original VM image MAC eth1, which exists, but all the configuration in all files refers to eth0, so it is not that good for me So I with sed delete the line with eth0 (it is obsolete and useless in cloned image) and replace eth1 with eth0. So currently I have valid persistent rule, but there is still eth1 in /dev. The issue: I don't want to reboot the machine (it will take another time, which is not good thing on building-VM-stage) and just want to have my /dev rebuilt with some command so I have ready-to-use VM without any reboots.

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  • Mutating Programming Language?

    - by MattiasK
    For fun I was thinking about how one could build a programming language that differs from OOP and came up with this concept. I don't have a strong foundation in computer science so it might be common place without me knowing it (more likely it's just a stupid idea :) I apologize in advance for this somewhat rambling question :) Anyways here goes: In normal OOP methods and classes are variant only upon parameters, meaning if two different classes/methods call the same method they get the same output. My, perhaps crazy idea, is that the calling method and class could be an "invisible" part of it's signature and the response could vary depending on who call's an method. Say that we have a Window object with a Break() method, now anyone (who has access) could call this method on Window with the same result. Now say that we have two different objects, Hammer and SledgeHammer. If Break need to produce different results based on these we'd pass them as parameters Break(IBluntObject bluntObject) With a mutating programming language (mpl) the operating objects on the method would be visible to the Break Method without begin explicitly defined and it could adopt itself based on them). So if SledgeHammer calls Window.Break() it would generate vastly different results than if Hammer did so. If OOP classes are black boxes then MPL are black boxes that knows who's (trying) to push it's buttons and can adapt accordingly. You could also have different permission sets on methods depending who's calling them rather than having absolute permissions like public and private. Does this have any advantage over OOP? Or perhaps I should say, would it add anything to it since you should be able to simply add this aspect to methods (just give access to a CallingMethod and CallingClass variable in context) I'm not sure, might be to hard to wrap one's head around, it would be kinda interesting to have classes that adopted themselves to who uses them though. Still it's an interesting concept, what do you think, is it viable?

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  • Oracle Endeca Information Discovery 3.1 is Now Available

    - by p.anda
    Oracle Endeca Information Discovery (OEID) 3.1 is a major release that incorporates significant new self-service discovery capabilities for business users. These include agile data mashup, extended support for unstructured analytics, and an even tighter integration with Oracle BI This release is available for download from: Oracle Delivery Cloud Oracle Technology Network Some of the what's new highlights ... Self-service data mashup... enables access to a wider variety of personal and trusted enterprise data sources. Blend multiple data sets in a single app. Agile discovery dashboards... allows users to easily create, configure, and securely share discovery dashboards with intelligent defaults, intuitive wizards and drag-and-drop configuration. Deeper unstructured analysis ... enables users to enrich text using term extraction and whitelist tagging while the data is live. Enhanced integration with OBI... provides easier wizards for data selection and enables OBI Server as a self-service data source. Enterprise-class data discovery... offers faster performance, a trusted data connection library, improved auditing and increased data connectivity for Hadoop, web content and Oracle Data Integrator. Find out more ... visit the OEID Overview page to download the What's New and related Data Sheet PDF documents. Have questions or want to share details for Oracle Endeca Information Discovery?  The MOS Communities is a great first stop to visit and you can stop-by at MOS OEID Community.

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