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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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• 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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• Finding recurrence relations of an algorithm

  - by Roarke

  I'm reading my algorithms text book, and I'm reading about recurrence relations and finding the algorithms big O complexity. I run across this line "In the case of the merge-sort algorithm, we get the recurrence equation: t(n) = b if n < 2 = 2t(n/2) +bn if n >= 2 for b > 0 my response was "how the heck did we know that?!?!" So i'm wondering if there is a systematic approach, or just a logical way of getting these recurrence relations from the algorithms can some one explain where the b and the two 2's come from?

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• What is "sentry object" in C++?

  - by Romain Hippeau

  I answered this question, and Potatoswatter answered too as The modern C++ equivalent would be a sentry object: construct it at the beginning of a function, with its constructor implementing call(), and upon return (or abnormal exit), its destructor implements I am not familiar with using sentry objects in C++. I thought they were limited to input and output streams. Could somebody explain to me about C++ sentry objects as well as how to use them as an around interceptor for one or more methods in a class ? i.e. How to do this ? Sentry objects are very similar indeed. On the one hand they require explicit instantiation (and being passed this) but on the other hand you can add to them so that they check not only the invariants of the class but some pre/post conditions for the function at hand.

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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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• 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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• 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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• PayPal testing without using Sandbox

  - by Webbo

  I am developing a website in PHP that accepts PayPal payments. It uses the IPN from PayPal and has a custom payment template etc etc. It all works great through the Sandbox server but when it comes to showing my client, I don't want to have to tell them to login to/create a Sandbox account, create a buyer account and make a payment - he hasn't got time for that and probably won't be able to do it. Therefore, my question is - is there any simple way that I can show my client the PayPal integration in "test mode" without him using the sandbox? I realise that I can set the transaction value to 0.01 and just test on the live PayPal server but that isn't an ideal solution. Cheers! Edit: Just to better explain what I mean, this is what my client sees when he first goes to checkout; As you can see, he has to login to his Sandbox account before then purchasing the item using the buyer email that he sets up. It's just confusing and totally non user-friendly.

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• How to change the text color in a disabled edit box using MFC?

  - by anand.arumug

  Hello all, I have a dialog in which the edit box is disabled but the text should be displayed in red instead of the default grey. I tried the following: void CMyEdit::OnEnable(BOOL bEnable) { CEdit::OnEnable(bEnable); if (bEnable) { m_BackGroundColor = kRGBWhite; } else { m_BackGroundColor = kRGBDefaultGray; } m_TextColor = kRGBRed; m_BackgroundBrush.DeleteObject(); m_BackgroundBrush.CreateSolidBrush(m_BackGroundColor); Invalidate(); } But its still displaying the text in grey only. But if I remove the base class call CEdit::OnEnable(bEnable); then new text color takes effect. Can anyone explain whats wrong in the code? Thanks for your time. cheers...

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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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• initialize a numpy array

  - by Curious2learn

  Is there way to initialize a numpy array of a shape and add to it? I will explain what I need with a list example. If I want to create a list of objects generated in a loop, I can do: a = [] for i in range(5): a.append(i) I want to do something similar with a numpy array. I know about vstack, concatenate etc. However, it seems these require two numpy arrays as inputs. What I need is: big_array # Initially empty. This is where I don't know what to specify for i in range(5): array i of shape = (2,4) created. add to big_array The big_array should have a shape (10,4). How to do this? Thanks for your help.

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• How to transfer binary data through multiple http server?

  - by solotim

  Well, the question is not intended to be that big. Let me explain the scenario: I have two http servers. server A is accessible to end user by web browser, while server B is internal server which can only be accessed by server A. If server B generate some big jpeg image in local disk, obviously we can't just delivery those path to image to server A and eventually to end user. Then, how to let end user see those image without firstly storing those image data in server A temporarily? I run PHP on server A and perl on server B, but this should not matter. I need a general pattern for implementing this.

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• Does mod_rewrite in subdirectories' .htaccess override higher levels?

  - by Ryan

  I'm using mod_rewrite to map my old directory structure to a new one. I have the following rule in my top-level .htaccess file, and it works: RewriteEngine On RewriteCond %{REQUEST_URI} /blog/archives/(.*) RewriteRule ^.*$ /archives/%1 [L,R=301] As you can guess, this takes http://example.com/blog/archives/00001.php and redirects it to http://example.com/archives/00001.php. But when I add these rewrite rules to the .htaccess file in the /blog directory RewriteEngine on RewriteRule atom.xml$ /atom.xml [L,R=301] the top-level redirect no longer works. If I move the rule in the /blog .htaccess file to the top-levle file both rules work. Can someone explain what is happening here?

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• Send a "304 Not Modified" for images stored in the datastore

  - by Emilien

  I store user-uploaded images in the Google App Engine datastore as db.Blob, as proposed in the docs. I then serve those images on /images/<id>.jpg. The server always sends a 200 OK response, which means that the browser has to download the same image multiple time (== slower) and that the server has to send the same image multiple times (== more expensive). As most of those images will likely never change, I'd like to be able to send a 304 Not Modified response. I am thinking about calculating some kind of hash of the picture when the user uploads it, and then use this to know if the user already has this image (maybe send the hash as an Etag?) I have found this answer and this answer that explain the logic pretty well, but I have 2 questions: Is it possible to send an Etag in Google App Engine? Has anyone implemented such logic, and/or is there any code snippet available?

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• iOS CollectionView with horizontal paging instead of vertical scrolling

  - by Nico Griffioen

  I'm working on a project for a client. It's an iPad pdf reader. The client wants a collection view, but instead of scrolling vertically, he wants it to use a page control. It's pretty hard to explain, but what I basically want is all the PDFs on the device in a grid, like on the iBooks app. When that grid overflows, I want to use a page control to display the extra elements on a second page (like in the weather app). My thoughts on this were: - Create a page control with one page. - On that page, create a UICollectionView. - If the number of elements is greater than 9 add a page to the page control and add another UICollectionView, until there are enough pages to display all elements. However, this seems horribly inefficient, so my question is if there's a better way to do this.

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• What do you do when you feel you need a variatic list comprehension?

  - by cspyr0

  I would like to make a method where I could give it a list of lengths and it would return all combinations of cartesian coordinates up to those lengths. Easier to explain with an example: cart [2,5] Prelude> [ [0,0],[0,1],[0,2],[0,3],[0,4],[1,0],[1,1],[1,2],[1,3],[1,4] ] cart [2,2,2] Prelude> [ [0,0,0],[0,0,1],[0,1,0],[0,1,1],[1,0,0],[1,0,1],[1,1,0],[1,1,1] ] A simple list comprehension won't work because I don't know how long the lists are going to be. While I love Haskell's simplicity for many problems, this is one that I could write procedurally (in C or something) in 5 minutes whereas Haskell gives me an aneurysm! A solution to this specific problem would help me out a lot; I'd also love to hear about your thought processes when tackling stuff like this.

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• Why is the 'if' statement considered evil?

  - by Vadim

  I just came from Simple Design and Testing Conference. In one of the session we were talking about evil keywords in programming languages. Corey Haines, who proposed the subject, was convinced that if statement is absolute evil. His alternative was to create functions with predicates. Can you please explain to me why if is evil. I understand that you can write very ugly code abusing if. But I don't believe that it's that bad.

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• c# xml string special characters

  - by sam

  Please help explain why the dataset cannot read the encoded xml? string xml = "<?xml version=\"1.0\" standalone=\"yes\" ?> <DataSet><node>it's my \"node\" & i like it</node></DataSet>"; string encodedXml = System.Security.SecurityElement.Escape(xml); DataSet ds = new DataSet(); ds.ReadXml(New XmlTextReader(new StringReader(encodedXml))); I have checked the link http://weblogs.sqlteam.com/mladenp/archive/2008/10/21/Different-ways-how-to-escape-an-XML-string-in-C.aspx What i want to do is to read a string with special characters into a dataset. But the code cannot locate the special characters in the string, c# added all the \ so the linenumber is not accurate generated by XmlException object. Anyone could provide the code to read a string with special characters into a dataset. thanks very much

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• Recognizing file - Python

  - by Francisco Aleixo

  Ok, so the title may trick you a bit, and I'm sorry for that but didn't find a better title. This question might be a bit hard to understand so I'll try my best. I have no idea how this works or if it is even possible but what I want to do is for example create a file type (lets imagine .test (in which a random file name would be random.test)). Now before I continue, its obviously easy to do this using for example: filename = "random.test" file = open(filename, 'w') file.write("some text here") But now what I would like to know is if it is possible to write the file .test so if I set it to open with a wxPython program, it recognizes it and for example opens up a Message Dialog automatically. I'm sorry if I'm being vague and in case you don't understand, let me know so I can try my best to explain you.

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• Java: How do you access a sub-object of an object with no "getXXX" method to that sub-object

  - by Daxon

  I'll explain with pictures from Eclipse Debugger I have an Class called "FieldContext", (I can't edit it, it's compiled in the Java OVal API) Within "FieldContext" on the eclipse variable tab are "CompileTimeType" and "field" Q1 Is there a legend for the icons in the variables tab? like what the red box with the "F" means + yellow diamond boxes? Now I want to access the fields inside the "field" object (RedBox) .. preferably "name" But the "FieldContext" does not have a "getField()" method, yet it has a "getCompileTimeType()" method. Q2 So is there anyway to get that field object being a "SerializableField" Class from the "FieldContext"? If eclipse debugger can see/get/edit them then I hope I can do the same in Java.

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• How do I read the cache of Chrome and Firefox programmatically on the Mac?

  - by John Gallagher

  Background I want to access the cache of Chrome and Firefox in my Cocoa application. I need to get the HTML for pages accessed recently. Safari is a piece of cake - all this information is available in SQLite data stores, but not so in Chrome and Firefox. The Problem For Firefox, the cache is in /Library/Caches/Firefox/Profiles/xxx.default/Cache with filenames _CACHE_001_ _CACHE_002_ _CACHE_003_ and _CACHE_MAP_ For Chrome, the cache is in /Library/Caches/Google/Chrome/Default/Cache with filenames data_0 data_1 data_2 and data_3 What I've tried The only article I can find that sheds any light on what format these caches are in is here. It recommends a Cache Viewer tool, but doesn't explain how one might do this programmatically. Questions Is there any way of reconstructing this data using command line tools or the Cocoa framework? Or is it much too low level? Is there another way of getting at the HTML of recent web pages that I don't know about?

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• How to execute in javascriptfunction in asp.net c#

  - by shree-khanal

  i have a textarea which i want to disable when I check a checkbox. I made a working demo in plain html and javascript, but When I am migrating to Asp.net, neither the function is being executed nor I can keep the onselect event in my check box. <asp:CheckBox ID="ChkOthers" runat="server" Text="Others(Please Explain)" Width="205px" AutoPostBack="True" OnCheckedChanged="ChkOthers_CheckedChanged" /></td> <asp:TextBox ID="TxtOtherReason" runat="server" MaxLength="1024" TextMode="MultiLine" ></asp:TextBox></td> i want to create client side validation when check box is checked textbox is enable else disable.

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• flex custom events bubbling

  - by Rajeshbabu TRC

  Dear Richard Szalay, i go through your answers regarding bubbling, i want explore bubbling more. Please see my sample below <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" xmlns:view="com.view.*" > } ]] In my custom event class i set bubbling=true, cancelable=true I can understand from previous answer that bubbling only affects UI components; events fired from custom classes will not bubble, even if the bubbles argument is set to true. My question is how can i prevent panelClickHandler function got fired when i click button in the "Load" (custom component)?? pleas explain bubbling with good example ( like to have with custom event classes)?

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• Why is this HTTP request continually looping?

  - by alex

  I'm probably overlooking something really obvious here. Comments are in to help explain any library specific code. public function areCookiesEnabled() { $random = 'cx67ds'; // set cookie cookie::set('test_cookie', $random); // try and get cookie, if not set to false $testCookie = cookie::get('test_cookie', false); $cookiesAppend = '?cookies=false'; // were we able to get the cookie equal ? $cookiesEnabled = ($testCookie === $random); // if $_GET['cookies'] === false , etc try and remove $_GET portion if ($this->input->get('cookies', false) === 'false' AND $cookiesEnabled) { url::redirect(str_replace($cookiesAppend, '', url::current())); // redirect return false; } // all else fails, add a $_GET[] if ( ! $cookiesEnabled) { url::redirect(url::current().$cookiesAppend); } return $cookiesEnabled; }

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• SaaS practical basics and projects

  - by Medardas

  So i need some directions. I want to understand Cloud Software as a Service(SaaS) practical initialization. The thing is I want to create a simple cloud service which would let me run programs on this cloud from remote machine. As I understand, I need some kind of specific backbone project to start this system, similar like OpenStack or Apache Cloud for Infostructure as a Service. Of course it may be that I understand it completely wrong and even if there is such project, it is not open source, free. I could also comprehend SaaS building on IaaS, but the thing is, I can't find any practical information at all. Could Somebody indulge me if there is any kind of free licence SaaS project or recommend a related articles or explain everything in a nut case with atleast vague direction.

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