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  • F# performance question: what is the compiler doing?

    - by Stephen Swensen
    Referencing this code: http://stackoverflow.com/questions/2840714/f-static-member-type-constraints/2842037#2842037 Why is, for example, [1L..100000L] |> List.map (fun n -> factorize gL n) significantly slower than [1L..100000L] |> List.map (fun n -> factorize (G_of 1L) n) By looking at Reflector, I can see that the compiler is treating each of these in very different ways, but there is too much going on for me to decipher the essential difference. Naively I assumed the former would perform better than the later because gL is precomputed whereas G_of 1L has to be computed 100,000 times (at least it appears that way).

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  • objective C architecture question

    - by thekevinscott
    Hey folks, I'm currently teaching myself objective C. I've gone through the tutorials, but I find I learn best when slogging through a project of my own, so I've embarked on making a backgammon app. Now that I'm partway in, I'm realizing there's some overall architecture things I just don't understand. I've established a "player" class, a "piece" class, and a "board" class. A piece theoretically belongs to both a player and the board. For instance, a player has a color, and every turn makes a move; so the player owns his pieces. At the same time, when moving a piece, it has to check whether it's a valid move, whether there are pieces on the board, etc. From my reading it seems like it's frowned upon to reach across classes. For instance, when a player makes a move, where should the function live that moves the piece? Should it exist on board? This would be my instinct, as the board should decide whether a move is valid or not; but the piece needs to initialize that query, as its the one being moved, no? Any info to help a noob would be super appreciated. Thanks guys!

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  • Understanding CSRF - Simple Question

    - by byronh
    I know this might make me seem like an idiot, I've read everything there is to read about CSRF and I still don't understand how using a 'challenge token' would add any sort of prevention. Please help me clarify the basic concept, none of the articles and posts here on SO I read seemed to really explicitly state what value you're comparing with what. From OWASP: In general, developers need only generate this token once for the current session. After initial generation of this token, the value is stored in the session and is utilized for each subsequent request until the session expires. If I understand the process correctly, this is what happens. I log in at http://example.com and a session/cookie is created containing this random token. Then, every form includes a hidden input also containing this random value from the session which is compared with the session/cookie upon form submission. But what does that accomplish? Aren't you just taking session data, putting it in the page, and then comparing it with the exact same session data? Seems like circular reasoning. These articles keep talking about following the "same-origin policy" but that makes no sense, because all CSRF attacks ARE of the same origin as the user, just tricking the user into doing actions he/she didn't intend. Is there any alternative other than appending the token to every single URL as a query string? Seems very ugly and impractical, and makes bookmarking harder for the user.

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  • C# threading question

    - by MusiGenesis
    Is there any essential difference between this code: ThreadStart starter = new ThreadStart(SomeMethod); starter.Invoke(); and this? ThreadStart starter = new ThreadStart(SomeMethod); Thread th = new Thread(starter); th.Start(); Or does the first invoke the method on the current thread while the second invokes it on a new thread?

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  • question about tablecell and its contols collection

    - by Varyanica
    i have a table (System.Web.UI.WebControls). each row does have three cells. in cells' controls collection i placed some controls TableCell cell = new TableCell(); cell.Font.Bold = false; cell.BackColor = Color.FromName("lightblue"); cell.Controls.Add(new LiteralControl("????")); row.Cells.Add(cell); TableCell c3 = new TableCell(); c3.Controls.Add(new CheckBox()); r.Cells.Add(c3); i cant find the way to get values which this controls are holding i see that CheckBox stores a value, but i don't know how to get it. Can you tell me how?

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  • PhysX Question about Raycasting - Setting the shape masks

    - by sweet tv
    I am trying to make the raycast give me the distance of the terrain and nothing else. But I'm not sure how to use the group Mask Filter. virtual NxShape* raycastClosestShape (const NxRay& worldRay, NxShapesType shapeType, NxRaycastHit& hit, NxU32 groups=0xffffffff, NxReal maxDist=NX_MAX_F32, NxU32 hintFlags=0xffffffff, const NxGroupsMask* groupsMask=NULL, NxShape** cache=NULL) const = 0; \param[in] groups Mask used to filter shape objects. Let's say my terrain is set in group 1. How would I use the function above?

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  • BindException/Too many file open while using HttpClient under load

    - by Langali
    I have got 1000 dedicated Java threads where each thread polls a corresponding url every one second. public class Poller { public static Node poll(Node node) { GetMethod method = null; try { HttpClient client = new HttpClient(new SimpleHttpConnectionManager(true)); ...... } catch (IOException ex) { ex.printStackTrace(); } finally { method.releaseConnection(); } } } The threads are run every one second: for (int i=0; i <1000; i++) { MyThread thread = threads.get(i) // threads is a static field if(thread.isAlive()) { // If the previous thread is still running, let it run. } else { thread.start(); } } The problem is if I run the job every one second I get random exceptions like these: java.net.BindException: Address already in use INFO httpclient.HttpMethodDirector: I/O exception (java.net.BindException) caught when processing request: Address already in use INFO httpclient.HttpMethodDirector: Retrying request But if I run the job every 2 seconds or more, everything runs fine. I even tried shutting down the instance of SimpleHttpConnectionManager() using shutDown() with no effect. If I do netstat, I see thousands of TCP connections in TIME_WAIT state, which means they are have been closed and are clearing up. So to limit the no of connections, I tried using a single instance of HttpClient and use it like this: public class MyHttpClientFactory { private static MyHttpClientFactory instance = new HttpClientFactory(); private MultiThreadedHttpConnectionManager connectionManager; private HttpClient client; private HttpClientFactory() { init(); } public static HttpClientFactory getInstance() { return instance; } public void init() { connectionManager = new MultiThreadedHttpConnectionManager(); HttpConnectionManagerParams managerParams = new HttpConnectionManagerParams(); managerParams.setMaxTotalConnections(1000); connectionManager.setParams(managerParams); client = new HttpClient(connectionManager); } public HttpClient getHttpClient() { if (client != null) { return client; } else { init(); return client; } } } However after running for exactly 2 hours, it starts throwing 'too many open files' and eventually cannot do anything at all. ERROR java.net.SocketException: Too many open files INFO httpclient.HttpMethodDirector: I/O exception (java.net.SocketException) caught when processing request: Too many open files INFO httpclient.HttpMethodDirector: Retrying request I should be able to increase the no of connections allowed and make it work, but I would just be prolonging the evil. Any idea what is the best practise to use HttpClient in a situation like above? Btw, I am still on HttpClient3.1.

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  • ASP.NET MVC Beginner's question

    - by Amutha
    Just I am learning MVC,(ofcourse i get enough information from MS Website).I want to quickly clarify some details. 1) What is the use of PartialView in MVC,Is it similar to partial update of Ajax? I am does the partialView modify the HTML DOM structure? 2)Can i use Response.Redirect() in MVC?

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  • Symfony + JQueryUI Tabs navigation menu question

    - by Andy Poquette
    I'm trying to use the tabs purely as a navigational menu, loading my pages in the tabs, but being able to bookmark said tabs, and have the address bar correspond with the action I'm executing. So here is my simple nav partial: <div id='tabs'> <ul> <li id='home'><a href="<?php echo url_for('post/index') ?>" title="Home">Home</a></li> <li id='test'><a href="<?php echo url_for('post/test') ?>" title="Test">Test</a></li> </ul> </div> And the simple tabs intializer: $(document).ready(function() { $('#tabs').tabs({spinner: '' }); }); My layout just displays $sf_content. I want to display the content for the action I'm executing (currently home or test) in the tab, via ajax, and have the tab be bookmarkable. I've googled this like 4000 times and I can't find an example of what I'm trying to do. If anyone has a resource they know of, I can look it up, or if you can help, I would greatly appreciate it. Thank you in advance.

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  • can't open web pages in google chrome

    - by javapowered
    When I type in google chrome "google.com" I receive such error: 404. That’s an error. The requested URL /cgi-bin/authme?s=0.2068704296834766 was not found on this server. That’s all we know. It seems I'm redirected somehow by some reason. Probably lenovo notebook problem? At the same time IE works fine. This problem reproducable with other webpages too, for example i'm redirected from vkontakte.ru to such web page which doesn't exist too http://www.vkontakte.ru/cgi-bin/authme?s=0.7140683813486247 Also I see such message when chrome starts "Lütfen yönlendirilirken bekleyin", this is very strange because I only have russian and english languages installed in system.

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  • Swing Panel Question

    - by dalton conley
    Ok, so I've been pulling my hair out over this all day. I cannot get my panels to resize. I add a panel to anything.. a frame, a content pane, and It wont .. "force" setBounds for some strange reason. Container pane = window.getContentPane(); JPanel calendarPanel = new JPanel(); pane.add(calendarPanel); calendarPanel.setBounds(0,0, 320, 335); note that window is of JFrame. Any suggestions to sizing a panel would be appreciated!

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  • sqllite - sql question 101

    - by qstar
    Hi, I would do something like this* select * from cars_table where body not equal to null. select * from cars_table where values not equal to null And id = "3" I know the syntax for 'not equal' is <, but i get an empty results. For the second part, I want to get a result set where it only returns the columns that have a value. So, if the value is null, then don't include that column. Thanks

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  • Basic question about std::vector instantiation

    - by recipriversexclusion
    This looks simple but I am confused: The way I create a vector of hundred, say, ints is std::vector<int> *pVect = new std::vector<int>(100); However, looking at std::vector's documentation I see that its constructor is of the form explicit vector ( size_type n, const T& value= T(), const Allocator& = Allocator() ); So, how does the previous one work? Does new call the constructor with an initialization value obtained from the default constructor? If that is the case, would std::vector<int, my_allocator> *pVect = new std::vector<int>(100, my_allocator); where I pass my own allocator, also work?

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  • GoDaddy Subdomain Hosting Issue/Question with Disk Access (C#/ASP.NET 3.5)

    - by Vogel
    This isn't a very complicated scenario really, but as I start to type out the problem I'm realizing how convoluted it can become textually. Let me try and be very clear: First, the set up... I have a C#/ASP.NET web application that is publicly facing on my main domain (www), let's call it www.mysite.com. Nothing fancy, just a front-end that connects to SQL to display records. Then, I have a second C#/ASP.NET web application that is secured using forms authentication running on a subdomain, let's call it admin.mysite.com. This is a very light-weight CMS system to administer the public site. Now, the problem... Both of these sites run fine for basic tasks, however, my problem arises when I try to gain access to the file system for uploading. GoDaddy requires subdomains to run as a virtual directories under the main application in IIS (so the subdomains actually resolve/re-direct to www.mysite.com/admin when you type in admin.mysite.com), but because of this I am unable to write to my website root from the subfolder. Let me explain a little more... The CMS system (running as a virtual directory) gives the admin the ability to upload photos for display on the main site, the target folder of which is www.mysite.com/images - when attempting disk access from the root app, I am able to write to the virtual directory, but cannot do the opposite -- that is, write to the root from the virtual directory, getting security violations. If I can only upload to the /admin/ virtual directory, the entire point is moot because it's a secured folder that the public can't see! The only solution I can think of is to upload the files to the /admin/ virtual directory, then call a URL in the root that moves files from /admin/ back to the root, but that is entirely ghetto. I hope this post makes sense. Anyone else experience anything like this? The bottom line is that it seems virtual directories ONLY have access to themselves, and not their parent directories, no matter what credentials are used. Thanks!

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  • Path String Concatenation Question in C#.

    - by Nano HE
    Hello. I want to output D:\Learning\CS\Resource\Tutorial\C#LangTutorial But can't work. Compiler error error CS0165: Use of unassigned local variable 'StrPathHead Please give me some advice about how to correct my code or other better solution for my case. Thank you. static void Main(string[] args) { string path = "D:\\Learning\\CS\\Resource\\Book\\C#InDeepth"; int n = 0; string[] words = path.Split('\\'); foreach (string word in words) { string StrPathHead; string StrPath; Console.WriteLine(word); if (word == "Resource") { StrPath = StrPathHead + word + "\\Tutorial\\C#LangTutorial"; } else { StrPathHead += words[n++] + "\\"; } } }

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  • Alternative to google map api, so that I can use it on a HTTPS/SSL encrypted website.

    - by Zeeshan Rang
    I have a question regarding map api. I was using the the google map api in my website before. But since I have encryption the site using HTTPS/SSL support, the google map api stopped working. I checked online, and realised that google has a Premier account only that would allow me to use HTTPS supported maps api and it cost $10,000 per year. I do not this kind of money with me. So, can you give any other alternative to have a map api on my website. Anything that could give me driving directions would be fine. Regards Zeeshan

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  • Another IKImageView Question: copying a region

    - by Brian Postow
    I'm trying to use the select and copy feature of the IKImageView. If all you want to do is have an app with an image, select a portion and copy it to the clipboard, it's easy. You set the copy menu pick to the first responder's copy:(id) method and magically everything works. However, if you want something more complicated, like you want to copy as part of some other operation, I can't seem to find the method to do this. IKImageView doesn't seem to have a copy method, it doesn't seem to have a method that will even tell you the selected rectangle! I have gone through Hillegass' book, so I understand how the clipboard works, just not how to get the portion of the image out of the view... Now, I'm starting to think that I made a mistake in basing my project on IKImageView, but it's what Preview is built on (or so I've read), so I figured it had to be stable... and anyway, now it's too late, I'm too deep in this to start over... So, other than not using IKImageView, any suggestions on how to copy the select region to the clipboard manually? EDIT actually, I have found the copy(id) method, but when I call it, I get <Error>: CGBitmapContextCreate: unsupported parameter combination: 8 integer bits/component; 16 bits/pixel; 1-component color space; kCGImageAlphaPremultipliedLast; 2624 bytes/row. Which obviously doesn't happen when I do a normal copy through the first-responder... I understand the error message, but I'm not sure where it's getting those parameters from... Is there any way to trace through this and see how this is happening? A debugger won't help for obvious reasons, as well as the fact that I'm doing this in Mozilla, so a debugger isn't an option anyway... EDIT 2 It occurs to me that the copy:(id) method I found may be copying the VIEW rather than copying a chunk of the image to the clipboard, which is what I need. The reason I thought it was the clipboard copy is that in another project, where I'm copying from an IKImageView to the clipboard straight from the edit menu, it just sends a copy:(id) to the firstResponder, but I'm not actually sure what the firstresponder does with it...

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  • Easy XPath question for iPhone

    - by Sam
    Hey guys! This is driving me NUTS! Here's my XML document <?xml version="1.0" encoding="UTF-8"?> <container version="1.0" xmlns="urn:oasis:names:tc:opendocument:xmlns:container"> <rootfiles> <rootfile full-path="content.opf" media-type="application/oebps-package+xml"/> </rootfiles> </container> All I want to do is get the root file element. I'm using TouchXML on the iPhone and here is my xPath query: /container/rootfiles/rootfile It doesn't work! I've tried everything. Any help would be appreciated... Sam

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  • Question on dynamic URL parsing

    - by jerebear
    I see many, many sites that have URLs for individual pages such as http://www.mysite.com/articles/this-is-article-1 http://www.mysite.com/galleries/575 And they don't redirect, they don't run slowly... I know how to parse URL's, that's easy enough. But in my mind, that seems slow and cumbersome on a dynamic site. As well, if the pages are all staticly built (hende the custom URL) then that means all components of the page are static as well... (which would be bad) I'd love to hear some ideas about how this is typically accomplished.

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  • 2D World design question

    - by Maciek
    I'm facing a problem which is probably extremely common in game-design. Let's assume that we've got a 2D world The world's size is M x N rect The world may contain some items in it The items have (x,y) coords The world can be browsed via a window that is physically (m x n) large. The browser window can be zoomed in / out The browser window can be panned up/down + left right, while in the extents of the world's rect. How should I go about implementing this? I'm especially concerned about the browser window. Can anyone recommend any good reads ? This is not a homework - it's more of a task which I've set myself to complete.

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