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• Only Integrating Box2D collision detection in my 2d engine?

  - by Mr.Gando

  I have integrated box2d in my engine, ( Debug Draw, etc. ) and with a world I can throw in some 2d squares/rectangles etc. I saw this post, where the user is basically not using a world for collision detection, however the user doesn't explain anything about how he's using the manifold (b2Manifold), etc. Another post, is in the cocos2d forum, ( scroll down to the user Lam in the third reply ) Could anyone help me a bit with this?, basically want to add collision detection without the need of using b2World ,etc etc. Thanks a lot!

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• postgres counting one record twice if it meets certain criteria

  - by Dashiell0415

  I thought that the query below would naturally do what I explain, but apparently not... My table looks like this: id | name | g | partner | g2 1 | John | M | Sam | M 2 | Devon | M | Mike | M 3 | Kurt | M | Susan | F 4 | Stacy | F | Bob | M 5 | Rosa | F | Rita | F I'm trying to get the id where either the g or g2 value equals 'M'... But, a record where both the g and g2 values are 'M' should return two lines, not 1. So, in the above sample data, I'm trying to return: $q = pg_query("SELECT id FROM mytable WHERE ( g = 'M' OR g2 = 'M' )"); 1 1 2 2 3 4 But, it always returns: 1 2 3 4

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• What exactly is a Monad?

  - by WeNeedAnswers

  Can someone please explain to me what a Monad is. I think I grasp Monoids and I grasp that they basically control the input of state into a system. I just look at the text in Haskell and glaze over. A simple example in python would be great. My current understanding is that a Monoid is a procedural piece of code that needs to be read from top to bottom in sequence with the output being the input for the function. I think that I may even got that wrong, but hey I am here to learn.

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• Why are the contents of my UITableViewCell disappearing?

  - by barfoon

  Hey everyone, I am learning about using the checkmark cell accessory and am wondering why the contents of my cell is disappearing when toggling it. Here is my code: + (void) toggleCheckmarkedCell:(UITableViewCell *)cell { if (cell.accessoryType == UITableViewCellAccessoryNone) cell.accessoryType = UITableViewCellAccessoryCheckmark; else cell.accessoryType = UITableViewCellAccessoryNone; } And here is didSelectRowAtIndexPath: UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath]; [cell setSelectionStyle:UITableViewCellSelectionStyleNone]; [RootViewController toggleCheckmarkedCell:cell]; The checkmark is toggling on/off and is visible but the main contents of the cell disappears. Can anyone explain why this is happening? Thank you,

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• SQL to return dates that fall in period and range

  - by Nate

  Hey stackers, I’ve been grinding my head on this for a while… My goal is to return all dates that fall between a start and end date and have a certain period as a factor, from the start date. (hard to explain) For example… Start Date: Nov 20, 1987; End Date: Jan 01, 1988; Period: 10 days; I want these dates: Nov 20, 1987; Nov 30, 1987; Dec 10, 1987; Dec 20, 1987; Dec 30, 1987; I already have a date table with all dates from 1900 to 2099. The period could be by days, months or years. Any ideas? Let me know if you need more info.

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• Inheriting and static members

  - by Bruce

  Here is my code - #include <iostream> #include <conio.h> using namespace std; class Base { public: int a; }; //int Base::a = 5; class Derived : public Base { public: int static a; }; int main() { Derived d; cout<<d.a; getch(); return 0; } I get a linker error here. But when I do it the other way round - class Base { public: int static a; }; int Base::a = 5; class Derived : public Base { public: int a; }; I get no error. Can someone please explain what is happening here.

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• tomcat 6 - Cluster / BackupManager

  - by Kevin

  Hi, I have a question regarding Clustering (session replication/failover) in tomcat 6 using BackupManager. Reason I chose BackupManager, is because it replicates the session to only one other server. I am going to run through the example below to try and explain my question. I have 6 nodes setup in a tomcat 6 cluster with BackupManager. The front end is one Apache server using mod_jk with sticky session enabled Each node has 1 session each. node1 has a session from client1 node2 has a session from client2 .. .. Now lets say node1 goes down ; assuming node2 is the backup, node2 now has two sessions (for client2 and client1) The next time client1 makes a request, what exactly happens ? Does Apache "know" that node1 is down and does it send the request directly to node2 ? =OR= does it try each of the 6 instances and find out the hard way who the backup is ?

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• what is the idea behind scaling an image using lanczos?

  - by banister

  Hi, I'm interested in image scaling algorithms and have implemented the bilinear and bicubic methods. However, I have heard of the lanczos and other more sophisticated methods for even higher quality image scaling and I am very curious how they work. Could someone here explain the basic idea behind scaling an image using lanczos (both upscaling and downscaling) and why it results in higher quality? I do have a background in fourier analysis and have done some signal processing stuff in the past, but not with relation to image processing, so don't be afraid to use terms like "frequency response" and such in your answer :) EDIT: I guess what i really want to know is the concept and theory behind using a convolution filter for interpolation. (Note: i have already read the wikipedia article on lanczos resampling but it didn't have nearly enough detail for me) thanks alot!

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• Haskell: What is the difference between $ (dollar) and $! (dollar exclamation point)

  - by Jelle Fresen

  Can anybody explain the difference in Haskell between the operators ($) and ($!) (dollar sign vs dollar sign exclamation point)? I haven't seen the use of $! anywhere so far, but while browsing through the Haskell reference on www.zvon.org, I noticed its existence and that it has the exact same definition as $. When trying some simple statements in a Haskell interpreter (ghci), I couldn't find any difference, nor could I find any reference to the operator in the top listed tutorials when googling for haskell tutorial. So, just out of curiosity, what is the difference, if at all?

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• Select from table by knowing only date without time (ORACLE)

  - by Abdulrhman

  Greeting People,, I'm trying to retrieve records from table by knowing the date in column contains date and time. let me explain my self clearly with this example: suppose i have table called t1 which contains only two column name, date respectively the data stored in column date like this "8/3/2010 12:34:20 PM" i want to retrieve this record by this query for example: Select * from t1 where date="8/3/2010" // notes i don't put the time. this query give me nothing ! SO now my question is how can i retrieve date by knowing only date without the time !

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• LINQ: why does this query not work on an ArrayList?

  - by Benny

  public static ArrayList GetStudentAsArrayList() { ArrayList students = new ArrayList { new Student() { RollNumber = 1,Name ="Alex " , Section = 1 ,HostelNumber=1 }, new Student() { RollNumber = 2,Name ="Jonty " , Section = 2 ,HostelNumber=2 } }; return students; } The following code doesn't compile. The error is ArrayList is not IEnumerable ArrayList lstStudents = GetStudentAsArrayList(); var res = from r in lstStudents select r; This compiles: ArrayList lstStudents = GetStudentAsArrayList(); var res = from Student r in lstStudents select r; Can anybody explain what the difference is between these two snippets? Why the second works?

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• GLOBAL problem with javascript

  - by Syom

  There is some problem, i can't understand anyway. look at this code please <script type="text/javascript"> function math(x) { var y; y = x*10; alert(y); } </script> <input type="button" onclick="math(0.011)"> What must be alerted after i click on button? i think 0.11, but no, it alerts 0.10999999999999999 explain please this behavior. thanks in advance

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• How can i have a div stuck on the left side of the page no matter how much i scroll horizontally?

  - by Noor

  This is kind of difficult to explain so ill link to a page that has the effect i need; http://wpaoli.building58.com/wp-content/uploads/2009/08/feedback-panel.html The feedback thing on the left side is what im trying to implement on my side, instead of feedback im going to use it as a navigation menu that shows up when clicked on. the things above is what i have right now. my problem is when i scroll to the right ( my page is around 6000px wide ) i want it to stay on the left side, is there a way to pull this off? (this is to much for my brain to handle)..thanks!

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• Socket ping-pong performance

  - by Kamil_H

  I have written two simple programs (tried it in C++ and C#). This is pseudo code: -------- Client --------------- for(int i = 0; i < 200.000; i++) { socket_send("ping") socket_receive(buff) } --------- Server ------------- while(1) { socket_receive(buff) socket_send("pong") } I tried it on Windows. Execution time of client is about 45 seconds. Can somebody explain me why this takes so long? I understand that if there were real network connection between client and server the time of one 'ping-pong' would be: generate_ping + send_via_network + generate_pong + send_via_network but here everything is done in 'local' mode. Is there any way to make this inter process ping-pong faster using network sockets (I'm not asking about shared memory for example :) )

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• How to optimise MySQL query containing a subquery?

  - by aidan

  I have two tables, House and Person. For any row in House, there can be 0, 1 or many corresponding rows in Person. But, of those people, a maximum of one will have a status of "ACTIVE", the others will all have a status of "CANCELLED". e.g. SELECT * FROM House LEFT JOIN Person ON House.ID = Person.HouseID House.ID | Person.ID | Person.Status 1 | 1 | CANCELLED 1 | 2 | CANCELLED 1 | 3 | ACTIVE 2 | 1 | ACTIVE 3 | NULL | NULL 4 | 4 | CANCELLED I want to filter out the cancelled rows, and get something like this: House.ID | Person.ID | Person.Status 1 | 3 | ACTIVE 2 | 1 | ACTIVE 3 | NULL | NULL 4 | NULL | NULL I've achieved this with the following sub select: SELECT * FROM House LEFT JOIN ( SELECT * FROM Person WHERE Person.Status != "CANCELLED" ) Person ON House.ID = Person.HouseID ...which works, but breaks all the indexes. Is there a better solution that doesn't? I'm using MySQL and all relevant columns are indexed. EXPLAIN lists nothing in possible_keys. Thanks.

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• WPF Dispatcher {"The calling thread cannot access this object because a different thread owns it."}

  - by user359446

  first I need to say that I´m noob with WPF and C#. Application: Create Mandelbrot Image (GUI) My disptacher works perfektly this this case: private void progressBarRefresh(){ while ((con.Progress) < 99) { progressBar1.Dispatcher.Invoke(DispatcherPriority.Send, new Action(delegate { progressBar1.Value = con.Progress; } )); } } I get the Message (Title) when tring to do this with the below code: bmp = BitmapSource.Create(width, height, 96, 96, pf, null, rawImage, stride); this.Dispatcher.Invoke(DispatcherPriority.Send, new Action(delegate { img.Source = bmp; ViewBox.Child = img; //vllt am schluss } )); I will try to explain how my program works. I created a new Thread (because GUI dont response) for the calculation of the pixels and the colors. In this Thread(Mehtod) I´m using the Dispatcher to Refresh my Image in the ViewBox after the calculations are ready. When I´m dont put the calculation in a seperate Thread then I can refresh or build my Image.

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• Perl Hash Slice, Replication x Operator, and sub params

  - by user210757

  Ok, I understand perl hash slices, and the "x" operator in Perl, but can someone explain the following code example from here (slightly simplified)? sub test{ my %hash; @hash{@_} = (undef) x @_; } Example Call to sub: test('one', 'two', 'three'); This line is what throws me: @hash{@_} = (undef) x @_; It is creating a hash where the keys are the parameters to the sub and initializing to undef, so: %hash: 'one' = undef, 'two' = undef, 'three' = undef The rvalue of the x operator should be a number; how is it that @_ is interpreted as the length of the sub's parameter array? I would expect you'd at least have to do this: @hash{@_} = (undef) x length(@_);

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• Having an online highscore leaderboard for a Flash game

  - by Marco Fox

  Why, hello there. I'm trying to develop a simple Flash game using Actionscript 2 (I know its a bit dated, but its a simple project that doesen't benefict much from AS3), and I came up with an ideia of implementing an online leaderboard that records and shows the highscore of the player. This isn't anything too complicated, but I seem to be having problem finding resources online that explain how I should implement this. All I want is a call, probably to a PHP/MySQL database that records the player's name (which will be recorded via a input window) and its current score. It would also have to show the best all time scores, by order. I should remind you that I am working on a Actionscript 2 so Actionscript 3 solutions are probably not going to work. Can anyone out there help me out here? Did any of you already been through this?

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• 2-Version software: Best VCS approach?

  - by Tom R

  I suppose I'd better explain my situation: I'm in the process of developing some software, and I'm at the stage where I'd like to split my project into two branches which differ in features. It so happens that this application is an Android application which I will be deploying on the Market, which has the constraint that every app must have a unique package identifier (sensible, no?). My current approach has been to clone the git repo of my original project, but this causes issues with package names. I want the system to be robust enough so that a bugfix/new feature on one branch will merge into another branch, but only when I want it to. Does anyone have any suggestions?

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• CSS [custom?] attributes

  - by Michael

  radio[pane] { list-style-image: url("jar:resource:///chrome/classic.jar! /skin/classic/browser/preferences/Options.png"); } radio[pane="prefpane-appearance"] { -moz-image-region: rect(0px, 32px, 32px, 0px); } radio[pane="prefpane-appearance"]:hover, radio[pane="prefpane-appearance"][selected="true"] { -moz-image-region: rect(32px, 32px, 64px, 0px); } Can anyone explain a syntax of this css, particularly what is pane.. I couldn't find such attribute for radio element in context of XUL. So I guess it's some custom attribute? If it is, then how it is evolving through the lines, first declaration, then several assignments? It has also selected, which means can have multiple custom attributes? How can those attributes be used later?

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• Issue with UITextView in an animation block

  - by collin

  I'm having an issue with a UITextView inside another UIView whose frame is manipulated in an animation block when the keyboard displays. During the animation block the UIView scales beautifully and as expected, but the UITextView jumps out of it's superview(the UIView being animated) at the start of the animation. By the end of the animation, the UITextView ends up in the right place... what gives? Can anybody explain why the UITextView is jumping out of it's container view at the start of the animation? Thanks in advance.

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• Static and overriding in Java

  - by Abhishek Jain

  public class B { static int i =1; public static int multiply(int a,int b) { return i; } public int multiply1(int a,int b) { return i; } public static void main(String args[]) { B b = new A(); System.out.println(b.multiply(5,2)); System.out.println(b.multiply1(5,2)); } } class A extends B { static int i =8; public static int multiply(int a,int b) { return 5*i; } public int multiply1(int a,int b) { return 5*i; } } Output: 1 40 Why is it so? Please explain.

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• Service design or access to another process

  - by hotyi

  I have a cache service,it's works as .net remoting, i want to create another windows service to clean up the that cache service by transfer the objects from cache to files. because they are in separate process, is their any way i could access that cache service or do i have to expose a method from the cache service to do that clean up work? the "clean up" means i want to serialize the object from Cache to file and these saved file will be used for further process. let me explain this application more detail. the application is mainly a log service to log all the coming request and these request will be saved to db for further data mining. we have 2 design for this log system 1) use MSMQ, but seems it's performance is not good enough, we don't use it. 2) we design a cache service, each request will be saved into the cache, and we need another function to clean up the cache by serialize the object to file.

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• How does this "&" work in this statement?

  - by aquaibm

  I know how bitwise AND works,but I don't understand how does (sourceDragMask & NSDragOperationGeneric) work here,I don't get the point.Is there anyone can explain to me?Thanks a lot. (NSDragOperation)draggingEntered:(id )sender { NSPasteboard *pboard; NSDragOperation sourceDragMask; sourceDragMask = [sender draggingSourceOperationMask]; pboard = [sender draggingPasteboard]; if ( [[pboard types] containsObject:NSColorPboardType] ) { if (sourceDragMask & NSDragOperationGeneric) { return NSDragOperationGeneric; } } return NSDragOperationNone; }

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• Why is this not a bug in qmail?

  - by jemfinch

  I was reading DJB's "Some thoughts on security after ten years of Qmail 1.0" and he listed this function for moving a file descriptor: int fd_move(to,from) int to; int from; { if (to == from) return 0; if (fd_copy(to,from) == -1) return -1; close(from); return 0; } It occurred to me that this code does not check the return value of close, so I read the man page for close(2), and it seems it can fail with EINTR, in which case the appropriate behavior would seem to be to call close again with the same argument. Since this code was written by someone with far more experience than I in both C and UNIX, and additionally has stood unchanged in qmail for over a decade, I assume there must be some nuance that I'm missing that makes this code correct. Can anyone explain that nuance to me?

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