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  • Removing ocurrances of characters in a string

    - by DmainEvent
    I am reading this book, programming Interviews exposed by John Wiley and sons and in chapter 6 they are discussing removing all instances of characters in a src string using a removal string... so removeChars(string str, string remove) In there writeup they sey the steps to accomplish this are to have a boolean lookup array with all values initially set to false, then loop through each character in remove setting the corresponding value in the lookup array to true (note: this could also be a hash if the possible character set where huge like Unicode-16 or something like that or if str and remove are both relatively small... < 100 characters I suppose). You then iterate through the str with a source and destination index, copying each character only if its corresponding value in the lookup array is false... Which makes sense... I don't understand the code that they use however... They have for(src = 0; src < len; ++src){ flags[r[src]] == true; } which is turning the flag value at the remove string indexed at src to true... so if you start out with PLEASE HELP as your str and LEA as your remove you will be setting in your flag table at 0,1,2... t|t|t but after that you will get an out of bounds exception because r doesn't have have anything greater than 2 in it... even using there example you get an out of bounds exception... Am is there code example unworkable?

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  • Physics-perfect (or somewhere near) 3d sound engine

    - by passcod
    I'm new to game programming, although I have some years of experience in console/web development. My problem is not so much that I can't find what I'm looking for, it's just that I don't have the terminology to actually perform a successful search. I am looking for a physics engine which has great focus on sounds. In fact, I do not care at all for anything else. What I mean is better explained by an example: Suppose a 1st person type game. You are facing North, and someone somewhere around you throws a flute at you (nevermind the absurdity of the situation). The flute spins while it is on its way, making sounds through its holes. There is a wind of say, 5 knots South. I imagine a physics engine will be capable of calculating the trajectory of the flute, as well as the direction it takes after it hits. What I want is for the physics engine to calculate the precise sounds it will make, from any listener's perspective. Does any such engine exists? If there are several, which one would be best for the example above?

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  • Why is apt-cache so slow?

    - by Damn Terminal
    After upgrade to Trusty (14.04) from Saucy (13.10), all apt operations are very slow. Even those that do not include downloading anything, or connecting to any servers. For example, displaying the apt policy # time apt-cache policy [...] real 0m8.951s user 0m5.069s sys 0m3.861s takes almost ten seconds! Mostly a weird lag right after issuing the command. And it's the same even if I issue the same command again. On another system it doesn't take a tenth of a second real 0m0.096s user 0m0.070s sys 0m0.023s The other system is a little beefier but there was no noticeable difference before the upgrade. It's the same with apt-get, anything apt-related. How do I find out the source of this lag and fix it? Additional info: # cat /etc/nsswitch.conf # /etc/nsswitch.conf # # Example configuration of GNU Name Service Switch functionality. # If you have the `glibc-doc-reference' and `info' packages installed, try: # `info libc "Name Service Switch"' for information about this file. passwd: compat group: compat shadow: compat hosts: files dns networks: files protocols: db files services: db files ethers: db files rpc: db files netgroup: nis BTW is my understanding of how apt-cache works correct? It doesn't make any network connections when I run apt-cache policy, right? In case I'm wrong and it matters, here are my sources https://gist.github.com/anonymous/02920270ff68e23fc3ec

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  • How to represent a graph with multiple edges allowed between nodes and edges that can selectively disappear

    - by Pops
    I'm trying to figure out what sort of data structure to use for modeling some hypothetical, idealized network usage. In my scenario, a number of users who are hostile to each other are all trying to form networks of computers where all potential connections are known. The computers that one user needs to connect may not be the same as the ones another user needs to connect, though; user 1 might need to connect computers A, B and D while user 2 might need to connect computers B, C and E. Image generated with the help of NCTM Graph Creator I think the core of this is going to be an undirected cyclic graph, with nodes representing computers and edges representing Ethernet cables. However, due to the nature of the scenario, there are a few uncommon features that rule out adjacency lists and adjacency matrices (at least, without non-trivial modifications): edges can become restricted-use; that is, if one user acquires a given network connection, no other user may use that connection in the example, the green user cannot possibly connect to computer A, but the red user has connected B to E despite not having a direct link between them in some cases, a given pair of nodes will be connected by more than one edge in the example, there are two independent cables running from D to E, so the green and blue users were both able to connect those machines directly; however, red can no longer make such a connection if two computers are connected by more than one cable, each user may own no more than one of those cables I'll need to do several operations on this graph, such as: determining whether any particular pair of computers is connected for a given user identifying the optimal path for a given user to connect target computers identifying the highest-latency computer connection for a given user (i.e. longest path without branching) My first thought was to simply create a collection of all of the edges, but that's terrible for searching. The best thing I can think to do now is to modify an adjacency list so that each item in the list contains not only the edge length but also its cost and current owner. Is this a sensible approach? Assuming space is not a concern, would it be reasonable to create multiple copies of the graph (one for each user) rather than a single graph?

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  • Purpose oriented user accounts on a single desktop?

    - by dd_dent
    Starting point: I currently do development for Dynamics Ax, Android and an occasional dabble with Wordpress and Python. Soon, I'll start a project involving setting up WP on Google Apps Engine. Everything is, and should continue to, run from the same PC (running Linux Mint). Issue: I'm afraid of botching/bogging down my setup due to tinkering/installing multiple runtimes/IDE's/SDK's/Services, so I was thinking of using multiple users, each purposed to handle the task at hand (web, Android etc) and making each user as inert as possible to one another. What I need to know is the following: Is this a good/feasible practice? The second closest thing to this using remote desktops connections, either to computers or to VM's, which I'd rather avoid. What about switching users? Can it be made seamless? Anything else I should know? Update and clarification regarding VM's and whatnot: The reason I wish to avoid resorting to VM's is that I dislike the performance impact and sluggishness associated with it. I also suspect it might add a layer of complexity I wish to avoid. This answer by Wyatt is interesting but I think it's only partly suited for requirements (web development for example). Also, in reference to the point made about system wide installs, there is a level compromise I should accept as experessed by this for example. This option suggested by 9000 is also enticing (more than VM's actually) and by no means do I intend to "Juggle" JVMs and whatnot, partly due to the reason mentioned before. Regarding complexity, I agree and would consider what was said, only from my experience I tend to pollute my work environment with SDKs and runtimes I tried and discarded, which would occasionally leave leftovers which cause issues throught the session. What I really want is a set of well defined, non virtualized sessions from which I can choose at my leisure and be mostly (to a reasonable extent) safe from affecting each session from the other. And what I'm really asking is if and how can this be done using user accounts.

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  • correct way to implement auth/acl in mvc

    - by WiseStrawberry
    I am looking into making a correctly laid out MVC auth/acl system. I think I want the authentication of a user (and the session handling) to be seperate from the ACL system. (I don't know why but this seems a good idea from the things I've read) What does mvc have to do with this question you ask? Because I wish for the application to be well integrated with my acl. An example of a controller (CodeIgniter) <?php class forums extends MX_Controller { $allowed = array('users', 'admin'); $need_login = true; function __construct() { //example of checking if logged in. if($this->auth->logged_in() && $this->auth->is_admin()) { echo "you're logged in!"; } } public function add_topic() { if($this->auth->allowed('add_topic') { //some add topic things. } else { echo 'not allowed to add topic'; } } } ?> My thoughts $this->auth would be autoloaded in the system. I would like to check the $allowed array against the user currently (not) logged in and react accordingly. Is this a good way of doing things? I haven't seen much literature on mvc integration and auth. I want to make things as easy as possible.

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  • Updating Google sitemap for mobile

    - by dimo414
    I have a series of utilities to generate Google sitemaps for my whole site. These files are massive, and slow to build. We want to start telling Google these pages are mobile-crawl-able too, by adding them to mobile sitemaps, but the documentation is unclear if I need to specify physically different files for my mobile URLs than for my normal ones. If this is my current sitemap: <?xml version="1.0" encoding="UTF-8" ?> <urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"> <url> <loc>http://mobile.example.com/article100.html</loc> </url> </urlset> Can I simply change it to: <?xml version="1.0" encoding="UTF-8" ?> <urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9" xmlns:mobile="http://www.google.com/schemas/sitemap-mobile/1.0"> <url> <loc>http://mobile.example.com/article100.html</loc> <mobile:mobile/> </url> </urlset> Or do I need to create new files with the additional markup, alongside my existing files?

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  • Should Android and iPhone UI be different?

    - by Phonon
    I'm not completely new to developing apps, but I'm at a point where I'm trying to develop something and deploy it on several mobile platforms. To only concentrate on two major ones, suppose I'm developing an app for Android and iPhone and designing UI and the general user interaction architecture. Both platforms give guidelines as to how their UIs should work. For example, most iPhone apps have the Navigation Bar (the one that says Testing 1 and has a Back button) and an Icon Bar for navigating a program, while Android uses an Options Menu fetched via a Menu button and the "back" navigation is handled with the physical Back button on the device. I've seen many apps that try to force the same UI on every platform. For example, custom-building an iPhone style Icon Bar and putting it in their Android apps, but it just doesn't quite look right to me and it feels like it violates UI design guidelines somewhat. Are there any good design patters for implementing something sufficiently similar on both platforms, yet still platform-specific enough so that the user would not feel out of their comfort zone? What do people usually do in these situations?

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  • How to do a 3-tier using PHP [closed]

    - by Ric
    I have a requirement from a client for my PHP Web application to be 3-tier. For example, I would have a web server on Apache in the DMZ, but it should NOT contain any DB connections. It should connect to a Middle server that would host the business objects but be behind the firewall. Then those objects connect to my SQL cluster on another server. I have actually done this using .NET, but I am not sure how to setup my stack using PHP. I suppose I could have my UI front tier call the middle tier using REST based web services if I create my middle tier as a second web server, but this seems overly complex. The main reason for this is advanced security: we can not have any passwords on the DMZ first tier web server. The second reason is scalability - to have multiple server on different tiers that can handle the requests. The Last reason is for deployment - it is easier if I can take one set of servers offline for testing before putting them back in production. Is there a open source project that shows how to do this? The only example I can find is the web server hosting files from a shared drive on another machine (kind of how DotNetNuke pretends to be 3-tier), but that is NOT secure.

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  • TFS SQL Deployment Data Script

    - by Greg
    We are using TFS and SQL 2005 (looking to upgrade to SQL 2012 if that makes a difference). We store our database schema in a Visual Studio Database project (VS 2010). When code is released to live we currently use the Visual Studio Database Project to build a script for all our schema changes. The problem we have been getting is having to alter or add to that script to add/fix data for the deployment. For example if we add a new non-nullable column to an existing table we need to populate that column with data during the insert. Other times we may want to create new records in transactional tables (e.g. assign specific users to a new security access). Do Visual Studio Database Projects have a way to store these scripts that only need to be run once and somehow include them in the build? Does it know which scripts need to be run (for example if we are inserting default data we don't want to do that again a second time)? OR Is there a better way to manage these scripts?

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  • Web Crawler for Learnign Topics on Wikipedia

    - by Chris Okyen
    When I want to learn a vast topic on wikipedia, I don't know where to start. For instance say I want to learn about Binary Stars, I then have to know other things linked on that pages and linked pages on all the linked pages and so on for the specified number of levels. I want to write a web crawler like HTTracker or something similiar, that will display a heiarchy of the links on a certain page and the links on those linked pages.I wish to use as much prewritten code as possible. Here is an example: Pretending we are bending the rules by grabing links from only the first sentence of each pages The example archives and "processes" two levels deep The page is Ternary operation The First Level In mathematics a ternary operation is an N-ary operation The Second Level Under Mathmatics: Mathematics (from Greek µ???µa máthema, “knowledge, study, learning”) is the abstract study of topics encompassing quantity, structure, space, change and others; it has no generally accepted definition. Under N-ary In logic,mathematics, and computer science, the arity i/'ær?ti/ of a function or operation is the number of arguments or operands that the function takes Under Operation In its simplest meaning in mathematics and logic, an operation is an action or procedure which produces a new value from one or more input values ------------------------------------------------------------------------- I need some way to determine what oder to approach all these wiki pages to learn the concept ( in this case ternary operations )... Following along with this exmpakle, one way to show the path to read would a printout flowout like so: This shows that the first sentence of the Mathematics page doesn't link to the first sentence of pages linked on ternary page two levels deep. (Please tell me how I should explain this ) --- In otherwords, the child node of the top pages first sentence, ternary_operation, does not have any child nodes that reference the children of the top pages other children nodes- N-ary and operation. Thus it is safe to read this first. Since N-ary has a link to operations we shoudl read the operation page second and finally read the N-ary page last. Again, I wish to use as much prewritten code as possible, and was wondering what language to use and what would be the simpliest way to go about doing this if there isn't already somethign out there? Thank You!

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  • Select Data From XML in MS SQL Server (T-SQL)

    - by Doug Lampe
    So you have used XML to give you some schema flexibility in your database, but now you need to get some data out.  What do you do?  The solution is relatively  simple:   DECLARE @iDoc INT /* Stores a pointer to the XML document */ DECLARE @XML VARCHAR(MAX) /* Stores the content of the XML */   set @XML = (SELECT top 1 Xml_Column_Name FROM My_Table where Primary_Key_Column = 'Some Value')   EXEC sp_xml_preparedocument @iDoc OUTPUT, @XML   SELECT * FROM OPENXML(@iDoc,'/some/valid/xpath',2)                      WITH (output_column1_name varchar(50)  'xml_node_name1',                                                     output_column2_name varchar(50)  'xml_node_name2')   EXEC sp_xml_removedocument @iDoc   In this example, the XML data would look something like this:   <some>   <valid>     <xpath>       <xml_node_name1>Value1</xml_node_name1>       <xml_node_name2>Value2</cml_node_name2>     </xpath>   </valid> </some>   The resulting query should give you this:   output_column1_name    output_column2_name ------------------------------------------ Value1                 Value2   Note that in this example we are only looking at a single record at a time.  You could use a cursor to iterate through multiple records and insert the XML data into a temporary table.

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  • How do sites avoid SEO issues / legalities with subdomain unique ids?

    - by JM4
    I was looking through a few websites recently and noticed a trend I'm not sure I understand. Sites are creating unique referral URLs for customers in the form of: http://customname.site.com (If somebody were to use http://www.site.com/customname it would function the same way). I can see the sites are using 302 redirects at some point using Google Chrome then doing some sort of htaccess redirect, taking the subdomain name (customname) and applying it as a referral parameter then keeping in session during the entire process. However, there must be thousands of these custom URLs that people are typing in. How are each one of these "subdomains" not treated as separate URLs which in turn are redirected to the same page (in short, generating tons of links all pointing to the same page which Google would normally frown upon)? Additionally, the links also appear on the site themselves as clickable links so I'm not sure how these are not tracked. Similarly, the "unique" url is not indexed or cached in any Google search results. How is this capability handled? It does NOT highlight the referral aspect, but a true example of this is visiting http://sfgiants.com which does a 302 redirect to the much longer proper San Francisco Giants MLB homepage. I am wondering how SFgiants.com is not indexed (assuming that direct shortened link appears on several MLB pages)? 1 - I know these are 302 redirects, I can see this on the sites network flow. 2 - These links do in fact appear on the page itself because in some areas (for example, the bottom of the page may say: send this page to a friend! http://name.site.com/ which in turn would again redirect to something like http://www.site.com?id=name so the id value could be stored in session

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  • WiFi slow sometimes, reboot helps, how do I debug it?

    - by January
    Ubuntu 12.04.1 with all updates installed. Laptop Lenovo Thinkpad X230 with Intel Corporation Centrino Advanced-N 6205. WiFi sometimes becomes extremely slow. Often this occurs when I wake the system from suspend and connect to a different network. I find no obvious clues in system logs. /etc/init.d/network-manager restart doesn't help, but a reboot does. How can I go on with debugging this issue? In specific, which parts of the system should I try to restart (without a complete reboot)? I know of problems with Intel WiFi (see for example this question and the instructions here), but if that was the problem, I would expect the WiFi to be slow at all times, and not just sometimes. Also, I have a gut feeling that it might be a DNS issue (for example, getting a page from a known server is faster than accessing a new server), but I don't know how to tackle it. Update: despite numerous updates in the meanwhile, I still observe this behavior. It happens always when I access my WiFi router at home after returning from work; when I reboot my laptop, the connection speed is good again.

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  • game play strategy in an arena

    - by joulesm
    I am writing a player's behavior for an arena game, and I'm wondering if you can offer some strategies. I'm writing it in Python, but I'm just interested in the high level game play. Here are the game aspects: Arena is a circle of a given size. The arena size shrinks every round to help break ties. Players are much smaller circles, can be on teams of 1 or 2 players. Players attack by colliding with other players, and based on the physics of the collision (speed of both players, angle), one could force another player out of the arena. Once a player is out of the arena, they are out of the game (for that round). The goal is to be the only team with players left in the arena. All other players have been pushed (through collisions or mistakes) out of the arena. It is possible for there to be no winner if the last two players exit the arena at the same time. Once the player has been programmed, the game just runs. There is no human intervention in the game. I'm thinking it's easiest to implement a few simple programmatic rules for my player to follow. For example, stay close to center of the arena, attack opponents from the inner side of the arena, etc. Are there any good simple game strategies? Would adding a random aspect to the game help? For example, to avoid predictability by the other team or something. Thanks in advance.

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  • GAPI output doesn't match Google Analytics website

    - by Yekver
    I have to get the main info about my Google Analytics Goals. I'm using GAPI lib, with this code: <?php require_once 'conf.inc'; require_once 'gapi.class.php'; $ga = new gapi(ga_email,ga_password); $dimensions = array('pagePath', 'hostname'); $metrics = array('goalCompletionsAll', 'goalConversionRateAll', 'goalValueAll'); $ga->requestReportData(ga_profile_id, $dimensions, $metrics, '-goalCompletionsAll', '', '2012-09-07', '2012-10-07', 1, 500); $gaResults = $ga->getResults(); foreach($gaResults as $result) { var_dump($result); } cut this code is output: object(gapiReportEntry)[7] private 'metrics' => array (size=3) 'goalCompletionsAll' => int 12031 'goalConversionRateAll' => float 206.93154454764 'goalValueAll' => float 0 private 'dimensions' => array (size=2) 'pagePath' => string '/catalogs.php' (length=13) 'hostname' => string 'www.example.com' (length=13) object(gapiReportEntry)[6] private 'metrics' => array (size=3) 'goalCompletionsAll' => int 9744 'goalConversionRateAll' => float 661.05834464043 'goalValueAll' => float 0 private 'dimensions' => array (size=2) 'pagePath' => string '/price.php' (length=10) 'hostname' => string 'www.example.com' (length=13) What I see on Google Analytics website on Goals URLs page with the same period of date is: Goal Completion Location Goal Completions Goal Value 1. /price.php 9,396 $0.00 2. /saloni.php 3,739 $0.00 As you can see outputs doesn't match. Why? What's wrong?

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  • What does SVN do better than git?

    - by doug
    No question that the majority of debates over programmer tools distill to either personal choice (by the user) or design emphasis, i.e., optimizing design according to particular uses cases (by the tool builder). Text Editors are probably the most prominent example--a coder who works on a Windows at work and codes in Haskell on the Mac at home, values cross-platform and compiler integration and so chooses Emacs over Textmate, etc. It's less common that a newly introduced technology is genuinely, demonstrably superior to the extant options. I wonder if this is in fact the case with version-control systems, in particular, centralized VCS (CVS, SVN) versus distributed VCS (git, hg)? I used SVN for about five years, and SVN is currently used where I work. A little less than three years ago, I switched to git (and gitHub) for all of my personal projects. I can think of a number of advantages of git over subversion (and which for the most part abstract to advantages of distributed over centralized VCS), but I cannot think of one contra example--some task (that's relevant and arises in a programmers usual workflow) that subversion does better than git. The only conclusion I have drawn from this is that I don't have any data--not that git is better, etc. My guess is that such counter-examples exist, hence this question.

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  • Centring an HTML element relative to its parent when its width is greater than its parent. [closed]

    - by casr
    I mocked up my intended outcome. So the blue element is the main content of the website and the yellow element represents something like a diagram or an image that has a greater width than the blue element. Ideally, I would like a purely CSS solution that is able to deal with various sizes of images. I have tried various things but have failed so far. I hope you can help! Here’s some example markup to set you on your way. <!DOCTYPE HTML> <html> <head> <title>Example</title> <style> #el1 { display: block; margin: 0 auto; width: 30em; background-color: #8cabde } #el2 { /* works when the width is less than the parent */ display: block; margin: 0 auto; } </style> </head> <body> <article id=el1> <p>Some content above.</p> <img id=el2 src=http://i.imgur.com/JFfGG.gif title=spaceball width=600 height=400> <p>Some content below.</p> </article> </body> </html>

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  • how to architect this to make it unit testable

    - by SOfanatic
    I'm currently working on a project where I'm receiving an object via web service (WSDL). The overall process is the following: Receive object - add/delete/update parts (or all) of it - and return the object with the changes made. The thing is that sometimes these changes are complicated and there is some logic involved, other databases, other web services, etc. so to facilitate this I'm creating a custom object that mimics the original one but has some enhanced functionality to make some things easier. So I'm trying to have this process: Receive original object - convert/copy it to custom object - add/delete/update - convert/copy it back to original object - return original object. Example: public class Row { public List<Field> Fields { get; set; } public string RowId { get; set; } public Row() { this.Fields = new List<Field>(); } } public class Field { public string Number { get; set; } public string Value { get; set; } } So for example, one of the "actions" to perform on this would be to find all Fields in a Row that match a Value equal to something, and update them with some other value. I have a CustomRow class that represents the Row class, how can I make this class unit testable? Do I have to create an interface ICustomRow to mock it in the unit test? If one of the actions is to sum all of the Values in the Fields that have a Number equal to 10, like this function, how can design the custom class to facilitate unit tests. Sample function: public int Sum(FieldNumber number) { return row.Fields.Where(x => x.FieldNumber.Equals(number)).Sum(x => x.FieldValue); } Am I approaching this the wrong way?

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  • Time Zone on WebLogic Server

    - by adejuanc
    In order to configure the time zone with WebLogic Server, use the following JVM startup command: -Duser.timezone=<timezone> For example, in the java arguments in the admin console at Environments -> Servers -> Servername -> - Server Start tab, configure the startup settings that Node Manager will use to start the particular server. For example: -Duser.timezone='America/Arizona' There are many different time zones, each with its own code. For a complete list please refer to : http://en.wikipedia.org/wiki/List_of_zoneinfo_time_zones For testing, you can run the following code on WLS with a JSP, servlet, or deploying the class: import java.util.Calendar; import java.util.TimeZone; public class TestTimeZone {  public static void main(String[] args) {    Calendar calendar = Calendar.getInstance();    TimeZone timeZone = calendar.getTimeZone();    System.out.println(" your Current TimeZone is : " + timeZone.getDisplayName());    System.out.println(" Time Zone id : "+ timeZone.getID());  } }

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  • Seperation of drawing and logic in games

    - by BFree
    I'm a developer that's just now starting to mess around with game development. I'm a .Net guy, so I've messed with XNA and am now playing around with Cocos2d for the iPhone. My question really is more general though. Let's say I'm building a simple Pong game. I'd have a Ball class and a Paddle class. Coming from the business world development, my first instinct is to not have any drawing or input handling code in either of these classes. //pseudo code class Ball { Vector2D position; Vector2D velocity; Color color; void Move(){} } Nothing in the ball class handles input, or deals with drawing. I'd then have another class, my Game class, or my Scene.m (in Cocos2D) which would new up the Ball, and during the game loop, it would manipulate the ball as needed. The thing is though, in many tutorials for both XNA and Cocos2D, I see a pattern like this: //pseudo code class Ball : SomeUpdatableComponent { Vector2D position; Vector2D velocity; Color color; void Update(){} void Draw(){} void HandleInput(){} } My question is, is this right? Is this the pattern that people use in game development? It somehow goes against everything I'm used to, to have my Ball class do everything. Furthermore, in this second example, where my Ball knows how to move around, how would I handle collision detection with the Paddle? Would the Ball need to have knowledge of the Paddle? In my first example, the Game class would have references to both the Ball and the Paddle, and then ship both of those off to some CollisionDetection manager or something, but how do I deal with the complexity of various components, if each individual component does everything themselves? (I hope I'm making sense.....)

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  • Testing a codebase with sequential cohesion

    - by iveqy
    I've this really simple program written in C with ncurses that's basically a front-end to sqlite3. I would like to implement TDD to continue the development and have found a nice C unit framework for this. However I'm totally stuck on how to implement it. Take this case for example: A user types a letter 'l' that is captured by ncurses getch(), and then an sqlite3 query is run that for every row calls a callback function. This callback function prints stuff to the screen via ncurses. So the obvious way to fully test this is to simulate a keyboard and a terminal and make sure that the output is the expected. However this sounds too complicated. I was thinking about adding an abstraction layer between the database and the UI so that the callback function will populate a list of entries and that list will later be printed. In that case I would be able to check if that list contains the expected values. However, why would I struggle with a data structure and lists in my program when sqlite3 already does this? For example, if the user wants to see the list sorted in some other way, it would be expensive to throw away the list and repopulate it. I would need to sort the list, but why should I implement sorting when sqlite3 already has that? Using my orginal design I could just do an other query sorted differently. Previously I've only done TDD with command line applications, and there it's really easy to just compare the output with what I'm expected. An other way would be to add CLI interface to the program and wrap a test program around the CLI to test everything. (The way git.git does with it's test-framework). So the question is, how to add testing to a tightly integrated database/UI.

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  • Messaging with KnockoutJs

    - by Aligned
    MVVM Light has Messaging that helps keep View Models decoupled, isolated, and keep the separation of concerns, while allowing them to communicate with each other. This is a very helpful feature. One View Model can send off a message and if anyone is listening for it, they will react, otherwise nothing will happen. I now want to do the same with KnockoutJs View Models. Here are some links on how to do this: http://stackoverflow.com/questions/9892124/whats-the-best-way-of-linking-synchronising-view-models-in-knockout http://www.knockmeout.net/2012/05/using-ko-native-pubsub.html ~ this is a great article describing the ko.subscribable type. http://jsfiddle.net/rniemeyer/z7KgM/ ~ shows how to do the subscription https://github.com/rniemeyer/knockout-postbox will be used to help with the PubSub (described in the blog post above) through the Nuget package. http://jsfiddle.net/rniemeyer/mg3hj/ of knockout-postbox   Implementation: Use syncWith for two-way synchronization. MainVM: self.selectedElement= ko.observable().syncWith (“selectedElement”); ElementListComponentVM example: self.selectedElement= ko.observable().syncWith(“selectedElement”); ko.selectedElement.subscribe(function(){ // do something with the seletion change }); ElementVMTwo: self.selectedElement= ko.observable().syncWith (“selectedElement”); // subscribe example ko.postbox.subscribe(“changeMessage”, function(newValue){ }); // or use subscribeTo this.visible = ko.observable().subscribeTo("section", function(newValue) { // do something here }); · Use ko.toJS to avoid both sides having the same reference (see the blog post). · unsubscribeFrom should be called when the dialog is hidden or closed · Use publishOn to automatically send out messages when an observable changes o ko.observable().publishOn(“section”);

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  • Minimum percentage of free physical memory that Linux require for optimal performance

    - by csoto
    Recently, we have been getting questions about this percentage of free physical memory that OS require for optimal performance, mainly applicable to physical compute nodes. Under normal conditions you may see that at the nodes without any application running the OS take (for example) between 24 and 25 GB of memory. The Linux system reports the free memory in a different way, and most of those 25gbs (of the example) are available for user processes. IE: Mem: 99191652k total, 23785732k used, 75405920k free, 173320k buffers The MOS Doc Id. 233753.1 - "Analyzing Data Provided by '/proc/meminfo'" - explains it (section 4 - "Final Remarks"): Free Memory and Used Memory Estimating the resource usage, especially the memory consumption of processes is by far more complicated than it looks like at a first glance. The philosophy is an unused resource is a wasted resource.The kernel therefore will use as much RAM as it can to cache information from your local and remote filesystems/disks. This builds up over time as reads and writes are done on the system trying to keep the data stored in RAM as relevant as possible to the processes that have been running on your system. If there is free RAM available, more caching will be performed and thus more memory 'consumed'. However this doesn't really count as resource usage, since this cached memory is available in case some other process needs it. The cache is reclaimed, not at the time of process exit (you might start up another process soon that needs the same data), but upon demand. That said, focusing more specifically on the percentage question, apart from this memory that OS takes, how much should be the minimum free memory that must be available every node so that they operate normally? The answer is: As a rule of thumb 80% memory utilization is a good threshold, anything bigger than that should be investigated and remedied.

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  • Centrally managing 100+ websites without bankrupting a small company

    - by palintropos
    I'm mainly interested in opinions on the trade-offs between having a single central server all the websites connect to as opposed to each website mirroring a subset of the master database with all the products in it. For example, will I run into severe performance issues (or even security issues, or restrictions) making queries to an offsite database? Will we hit scalability issues we can't handle early on from the sheer bandwidth required to maintain this? If we do go with something like a script that keeps smaller databases (each containing a subset of the central master data) in sync, what sorts of issues will we likely encounter there? I would really like the opinions of people far more knowledgeable than I am regarding the pros and cons of both setups and what headaches we are likely to encounter. CLARIFICATION: This should not be viewed as a question about whether we should implement one database vs multiple databases. This question has been answered numerous times. The question is regarding the pros and cons for a deployment like this having the ability to manage all the websites centrally (one server) vs trying to keep them all in sync if they each have their own db (multiple servers). REAL-WORLD EXAMPLE: We are a t-shirt company, and we have individual websites for our different kinds of t-shirts, but we're looking at a central order management integrated with our single shopping cart (which is ColdFusion + MySQL). Now, let's say we have a t-shirt that's on 10 of our websites and we change an image for it. Ideally we would change that in one place and the change would propagate, but how would we set this up?

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