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  • Does everything after my try statement have to be encompassed in that try statement to access variab

    - by Mithrax
    I'm learning java and one thing I've found that I don't like, is generally when I have code like this: import java.util.*; import java.io.*; public class GraphProblem { public static void main(String[] args) { if (args.length < 2) { System.out.println("Error: Please specify a graph file!"); return; } FileReader in = new FileReader(args[1]); Scanner input = new Scanner(in); int size = input.nextInt(); WeightedGraph graph = new WeightedGraph(size); for(int i = 0; i < size; i++) { graph.setLabel(i,Character.toString((char)('A' + i))); } for(int i = 0; i < size; i++) { for(int j = 0; j < size; j++) { graph.addEdge(i, j, input.nextInt()); } } // .. lots more code } } I have an uncaught exception around my FileReader. So, I have to wrap it in a try-catch to catch that specific exception. My question is does that try { } have to encompass everything after that in my method that wants to use either my FileReader (in) or my Scanner (input)? If I don't wrap the whole remainder of the program in that try statement, then anything outside of it can't access the in/input because it may of not been initialized or has been initialized outside of its scope. So I can't isolate the try-catch to just say the portion that intializes the FileReader and close the try statement immediately after that. So, is it the "best practice" to have the try statement wrapping all portions of the code that are going to access variables initialized in it? Thanks!

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  • Spring MVC: How to get the remaining path after the controller path?

    - by Willis Blackburn
    I've spent over an hour trying to find the answer to this question, which seems like it should reflect a common use case, but I can't figure it out! Basically I am writing a file-serving controller using Spring MVC. The URLs are of the format http://www.bighost.com/serve/the/path/to/the/file.jpg, in which the part after "/serve" is the path to the requested file, which may have an arbitrary number of path segments. I have a controller like this: @Controller class ServerController { @RequestMapping(value = "/serve/???") public void serve(???) { } } What I am trying to figure out is: What do I use in place of "???" to make this work? I have two theories about how this should work. The first theory is that I could replace the first "???" in the RequestMapping with a path variable placeholder that has some special syntax meaning "capture to the end of the path." If a regular placeholder looks like "{path}" then maybe I could use "{path:**}" or "{path:/}" or something like that. Then I could use a @PathVariable annotation to refer to the path variable in the second "???". The other theory is that I could replace the first "???" with "**" (match anything) and that Spring would give me an API to obtain the remainder of the path (the part matching the "**"). But I can't find such an API. Thanks for any help you can provide!

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  • Python Speeding Up Retrieving data from extremely large string

    - by Burninghelix123
    I have a list I converted to a very very long string as I am trying to edit it, as you can gather it's called tempString. It works as of now it just takes way to long to operate, probably because it is several different regex subs. They are as follow: tempString = ','.join(str(n) for n in coords) tempString = re.sub(',{2,6}', '_', tempString) tempString = re.sub("[^0-9\-\.\_]", ",", tempString) tempString = re.sub(',+', ',', tempString) clean1 = re.findall(('[-+]?[0-9]*\.?[0-9]+,[-+]?[0-9]*\.?[0-9]+,' '[-+]?[0-9]*\.?[0-9]+'), tempString) tempString = '_'.join(str(n) for n in clean1) tempString = re.sub(',', ' ', tempString) Basically it's a long string containing commas and about 1-5 million sets of 4 floats/ints (mixture of both possible),: -5.65500020981,6.88999986649,-0.454999923706,1,,,-5.65500020981,6.95499992371,-0.454999923706,1,,, The 4th number in each set I don't need/want, i'm essentially just trying to split the string into a list with 3 floats in each separated by a space. The above code works flawlessly but as you can imagine is quite time consuming on large strings. I have done a lot of research on here for a solution but they all seem geared towards words, i.e. swapping out one word for another. EDIT: Ok so this is the solution i'm currently using: def getValues(s): output = [] while s: # get the three values you want, discard the 3 commas, and the # remainder of the string v1, v2, v3, _, _, _, s = s.split(',', 6) output.append("%s %s %s" % (v1.strip(), v2.strip(), v3.strip())) return output coords = getValues(tempString) Anyone have any advice to speed this up even farther? After running some tests It still takes much longer than i'm hoping for. I've been glancing at numPy, but I honestly have absolutely no idea how to the above with it, I understand that after the above has been done and the values are cleaned up i could use them more efficiently with numPy, but not sure how NumPy could apply to the above. The above to clean through 50k sets takes around 20 minutes, I cant imagine how long it would be on my full string of 1 million sets. I'ts just surprising that the program that originally exported the data took only around 30 secs for the 1 million sets

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  • Why aren't variables declared in "try" in scope in "catch" or "finally"?

    - by Jon Schneider
    In C# and in Java (and possibly other languages as well), variables declared in a "try" block are not in scope in the corresponding "catch" or "finally" blocks. For example, the following code does not compile: try { String s = "test"; // (more code...) } catch { Console.Out.WriteLine(s); //Java fans: think "System.out.println" here instead } In this code, a compile-time error occurs on the reference to s in the catch block, because s is only in scope in the try block. (In Java, the compile error is "s cannot be resolved"; in C#, it's "The name 's' does not exist in the current context".) The general solution to this issue seems to be to instead declare variables just before the try block, instead of within the try block: String s; try { s = "test"; // (more code...) } catch { Console.Out.WriteLine(s); //Java fans: think "System.out.println" here instead } However, at least to me, (1) this feels like a clunky solution, and (2) it results in the variables having a larger scope than the programmer intended (the entire remainder of the method, instead of only in the context of the try-catch-finally). My question is, what were/are the rationale(s) behind this language design decision (in Java, in C#, and/or in any other applicable languages)?

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  • Is Domain Anaemia appropriate in a Service Oriented Architecture?

    - by Stimul8d
    I want to be clear on this. When I say domain anaemia, I mean intentional domain anaemia, not accidental. In a world where most of our business logic is hidden away behind a bunch of services, is a full domain model really necessary? This is the question I've had to ask myself recently since working on a project where the "domain" model is in reality a persistence model; none of the domain objects contain any methods and this is a very intentional decision. Initially, I shuddered when I saw a library full of what are essentially type-safe data containers but after some thought it struck me that this particular system doesn't do much but basic CRUD operations, so maybe in this case this is a good choice. My problem I guess is that my experience so far has been very much focussed on a rich domain model so it threw me a little. The remainder of the domain logic is hidden away in a group of helpers, facades and factories which live in a separate assembly. I'm keen to hear what people's thoughts are on this. Obviously, the considerations for reuse of these classes are much simpler but is really that great a benefit?

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  • App Engine - Query using a class member as parameter

    - by Zach
    I have a simple class, relevant details below: @PersistenceCapable(identityType = IdentityType.APPLICATION) public class SimpleCategory implements Serializable{ ... public static enum type{ Course, Category, Cuisine } @Persistent public type t; ... } I am attempting to query all SimpleCategory objects of the same type. public SimpleCategory[] getCategories(SimpleCategory.type type) { PersistenceManager pm = PMF.get().getPersistenceManager(); try{ Query q = pm.newQuery(SimpleCategory.class); q.setFilter("t == categoryType"); q.declareParameters("SimpleCategory.type categoryType"); List<SimpleCategory> cats = (List<SimpleCategory>) q.execute(type); ... } This results in a ClassNotResolvedException for SimpleCategory.type. The google hits I've found so far recommended to: Use query.declareImports to specify the class i.e. q.declareImports("com.test.zach.SimpleCategory.type"); Specify the fully qualified name of SimpleCategory in declareParameters Neither of these suggestions has worked. By removing .type and recompiling, I can verify that declareParameters can see SimpleCategory just fine, it simply cannot see the SimpleCategory.type, despite the fact that the remainder of the method has full visibility to it. What am I missing?

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  • New to JEE; architecture suggestions for a service/daemon?

    - by Kate
    I am brand new to the JEE world. As an exercise to try and familiarize myself with JEE, I'm trying to create a tiered web-app, but I'm getting a little stuck on what the best way is to spin up a service in the background that does work. Parameters of the service: It must open and hold a socket connection and receive information from the connected server. There is a 1-to-1 correlation between a user and a new socket connection. So the idea is the user presses a button on the web-page, and somewhere on the server a socket connection is opened. For the remainder of the users session (or until the user presses some sort of disconnect button) the socket remains open and pushes received information to some sort of centralized store that servlets can query and return to the user via AJAX. Is there a JEE type way to handle this situation? Naturally what I would think to do is to just write a Java application that listens on a port that the servlets can connect to and spawns new threads that open these sockets, but that seems very ad-hoc to me. (PS: I am also new to Stack Overflow, so forgive me if it takes me some time to figure the site out!)

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  • Peculiar JRE behaviour running RMI server under load, should I worry?

    - by darri
    I've been developing a minimalistic Java rich client CRUD application framework for the past few years, mostly as a hobby but also actively using it to write applications for my current employer. The framework provides database access to clients either via a local JDBC based connection or a lightweight RMI server. Last night I started a load testing application, which ran 100 headless clients, bombarding the server with requests, each client waiting only 1 - 2 seconds between running simple use cases, consisting of selecting records along with associated detail records from a simple e-store database (Chinook). This morning when I looked at the telemetry results from the server profiling session I noticed something which to me seemed strange (and made me keep the setup running for the remainder of the day), I don't really know what conclusions to draw from it. Here are the results: Memory GC activity Threads CPU load Interesting, right? So the question is, is this normal or erratic? Is this simply the JRE (1.6.0_03 on Windows XP) doing it's thing (perhaps related to the JRE configuration) or is my framework design somehow causing this? Running the server against MySQL as opposed to an embedded H2 database does not affect the pattern. I am leaving out the details of my server design, but I'll be happy to elaborate if this behaviour is deemed erratic.

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  • New to J2EE; architecture suggestions for a service/daemon?

    - by Kate
    I am brand new to the J2EE world. As an exercise to try and familiarize myself with J2EE, I'm trying to create a tiered web-app, but I'm getting a little stuck on what the best way is to spin up a service in the background that does work. Paramters of the service: It must open and hold a socket connection and receive information from the connected server. There is a 1-to-1 correlation between a user and a new socket connection. So the idea is the user presses a button on the web-page, and somewhere on the server a socket connection is opened. For the remainder of the users session (or until the user presses some sort of disconnect button) the socket remains open and pushes received information to some sort of centralized store that servlets can query and return to the user via AJAX. Is there a J2EE type way to handle this situation? Naturally what I would think to do is to just write a Java application that listens on a port that the servlets can connect to and spawns new threads that open these sockets, but that seems very ad-hoc to me. (PS: I am also new to Stack Overflow, so forgive me if it takes me some time to figure the site out!)

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  • Beginner Question ; About Prime Generation in "C" - What is wrong with my code ? -

    - by alorsoncode
    I'm a third year irregular CS student and ,i just realized that i have to start coding. I passed my coding classes with lower bound grades so that i haven't a good background in coding&programming. I'm trying to write a code that generates prime numbers between given upper and lower bounds. Not knowing C well, enforce me to write a rough code then go over it to solve. I can easily set up the logic for intended function but i probably create a wrong algorithm through several different ways. Here I share my last code, i intend to calculate that when a number gives remainder Zero , it should be it self and 1 , so that count==2; What is wrong with my implementation and with my solution generating style? I hope you will warm me up to programming world, i couldn't find enough motivation and courage to get deep into programming. Thanks in Advance :) Stdio and Math.h is Included int primegen(int down,int up) { int divisor,candidate,count=0,k; for(candidate=down;candidate<=up;candidate++) { for(divisor=1;divisor<=candidate;divisor++) { k=(candidate%divisor); } if (k==0) count++; if(count==2) { printf("%d\n", candidate); count=0; } else { continue; } } } int main() { primegen(3,15); return 0; }

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  • Windows 7 + Deep Freeze - I'm stuck in an endless reboot loop

    - by myermian
    I have the following setup: Windows 7 Ultimate Deep Freeze I "thawed" my machine last night and performed a Windows Update. The update is having issues (it gets stuck at 32%, fails, and restarts my machine). When it reboots it attempts it again, and again, and again, etc. (Endless loop). I looked online and found some solutions, but none of them seem to be working: When I run Safe Mode, Safe Mode w/ Network, or Safe Mode w/ Command Prompt it attempts to revert the Windows Update changes. However, the problem is with Deep Freeze on (and now in "Frozen" mode) the reverted changes don't stay, and I'm back into the loop of death. Oh, and side note: "Safe Mode w/ Command Prompt" does not actually take me to a command prompt window? Perhaps because it is attempting to complete the Windows Update changes first? I have tried to select the option to NOT restart when an windows error occurs, but it still does. I tried the remainder of all the other options in the F8 screen. The only other option left is to find my Windows 7 Media Disc (I can't find it right now) and use it to repair windows (because for some reason the repair option does not show up in the F8 screen). Is there a way to disable Deep Freeze from loading? When I selected "Safe Mode w/ Command Prompt" I noticed that it loads the DpFrz.sys file. I know that when I'm in the Windows Boot Manager if I press F10 instead of F8 (while highlighting Windows 7) it takes me to an "Edit Boot Options" screen: Edit Windows boot options for: Windows 7 Path: \Windows\system32\winload.exe Partition: 2 Hard Disk: 8e90e329 [ /NOEXECUTE=OPTIN (I CAN EDIT THIS LINE) ] Update: I found my Windows 7 Media Disk and it did not help out. The laptop had the "System Restore" as a partition on the HDD. I later received (in the mail) a Windows 7 Upgrade Disc from Sony to upgrade my system from Windows Vista to Windows 7 Ultimate. I placed the disc into the DVD drive and it does not come up as a "bootable" disc. I'm going to try to find an alternative disc to see if I can get into Command Prompt. Update 2: I got a Windows Repair disc and got into a command prompt window. I got into the registry and disabled Deep Freeze. Also: I renamed the Pending.xml file to Pending.old I cleared out the Windows Temp directory I still am stuck in the loop (though, it isn't an issue with DeepFreeze anymore because I can make changes to the hard drive and they persist). Not sure what to do at this point? Update 3: I ran the repair option and it couldn't repair, but it did point me to something. It says the error was due to a driver that was failing. I have a feeling it is my UPEK Fingerprint scanner.

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  • Windows Phone 8 Launch Event Summary

    - by Tim Murphy
    Today was the official coming out party for Windows Phone 8.  Below is a summary of the launch event.  There is a lot here to stay with me. They started with a commercial staring Joe Belfiore show how his Windows Phone 8 was personal too him which highlights something I think Microsoft has done well over the last couple of event: spotlight how Windows Phone is a different experience from other smartphones.  Joe actually called iPhone and Android “tired old metaphors" and explained that the idea around Windows Phone was to “reinvent the smartphone around you” as “the most personal smartphone operating system”.  The is the message that they need to drive home in their adds. The only real technical aspect we found out was that they have optimized the operating system around the dual core Qualcomm Snapdragon chip set.  It seems like all of the other hardware goodies had already been announced.  The remainder of the event was centered around new features of the OS and app announcements. So what are we getting?  The integrated features included lock screen live tile, Data Sense, Rooms and Kids corner.  There wasn’t a lot of information about it, but Joe also talked about apps not just having live tiles, but being live apps that could integrate with wallet and the hub. The lock screen will now be able to be personalized with live tile data or even a photo slide show.  This gives the lock screen an even better ability to give you the information you want to know before you even unlock the phone. The Kids Corner allows you as a parent to setup an area on your phone that you kids can go into an use it without disturbing your apps.  They can play games or use apps that you have designated and will only see those apps.  It even has a special lock screen gesture just for the kids corner. Rooms allow you to organize your phone around the groups of people in your life.  You get a shared calendar, a room wall as well as shared notes beyond just being able to send messages to a group.  You can also invite people not on the Windows Phone platform to access an online version of the room. Data Sense is a new feature that gives you better control and understanding of your data plan usage.  You can see which applications are using data and it can automatically adjust they way your phone behaves as you get close to your data limit. Add to these features the fact that the entire Windows ecosystem is integrated with SkyDrive and you have an available anywhere experience that is unequaled by any other platform.  Your document, photos and music are available on your Windows Phone, Window 8 device and Xbox.  SkyDrive also doesn’t limit how long you can keep files like the competing cloud platforms and give more free storage. It was interesting the way they made the launch event more personal.  First Joe brought out his own kids to demo the Kids Corner.  They followed this up by bringing out Jessica Alba to discuss her experience on the Windows Phone 8.  They need to keep putting a face on the product instead of just showing features as a cold list. Then we get to apps.  We knew that the new Skype was coming, but we found out that it was created in such a way that it can receive calls without running consistently in the background which would eat up battery.  This announcement was follow by the coming Facebook app that is optimized for Windows Phone 8.  As a matter of fact they indicated that just after launch the marketplace would have 46 out of the top 50 apps used by all smartphone platforms.  In a rational world this tide with over 120,000 apps currently in the marketplace there should be no more argument about the Windows Phone ecosystem. For those of us who develop for Windows Phone and weren’t on the early adoption program will finally get access to the SDK tomorrow after an announcement at Build (more waiting).  Perhaps we will get a few new features then. In the end I wouldn’t say there were any huge surprises, but I am really excited about getting my hands on the devices next month and starting to develop.  Stay tuned. del.icio.us Tags: Windows Phone,Windows Phone 8,Winodws Phone 8 Launch,Joe Belfiore,Jessica Alba

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  • How do I correctly Re-render a Recaptcha in ASP.NET MVC 2 after an AJAX POST

    - by Eoin Campbell
    Ok... I've downloaded and implemented this Recaptcha implementation for MVC which uses the ModelState to confirm the validity of the captcha control. It works brilliantly... except when I start to use it in an AJAX Form. In a nutshell, when a div is re-rendered with AJAX, the ReCaptcha that it should contain does not appear, even though the relevant <scripts> are in the source after the partial render. Code Below. using (Ajax.BeginForm("CreateComment", "Blog", new AjaxOptions() { HttpMethod = "POST", UpdateTargetId = "CommentAdd", OnComplete="ReloadRecaptcha", OnSuccess = "ShowComment", OnFailure = "ShowComment", OnBegin = "HideComment" })) {%> <fieldset class="comment"> <legend>Add New Comment</legend> <%= Html.ValidationSummary()%> <table class="postdetails"> <tbody> <tr> <td rowspan="3" id="blahCaptcha"> <%= Html.CreateRecaptcha("recaptcha", "blackglass") %> </td> .... Remainder of Form Omitted for Brevity I've confirmed the Form is perfectly functional when the Recaptcha Control is not present and the Javascript calls in the AjaxOptions are all working fine. The problem is that if the ModelState is Invalid as a result of the Recaptcha or some other validation, then the ActionResult returns the View to reshow the form. [RecaptchaFilter(IgnoreOnMobile = true)] [HttpPost] public ActionResult CreateComment(Comment c) { if (ModelState.IsValid) { try { //Code to insert Comment To DB return Content("Thank You"); } catch { ModelState.AddRuleViolations(c.GetRuleViolations()); } } else { ModelState.AddRuleViolations(c.GetRuleViolations()); } return View("CreateComment", c); } When it's InValid and the form posts back, for some reason the ReCaptcha Control does not re-render. I've checked the source and the <script> & <noscript> blocks are present in the HTML so the HTML Helper function below is obviously working <%= Html.CreateRecaptcha("recaptcha", "blackglass") %> I assume this has something to do with scripts injected into the DOM by AJAX are not re-executed. As you can see from the HTML snippet above, I've tried to add an OnComplete= javascript function to re-create the Captcha on the client side, but although the script executes with no errors, it doesn't work. OnComplete Function is. function ReloadRecaptcha() { Recaptcha.create("my-pub-key", 'blahCaptcha', { //blahCaptcha is the ID of the <td> where the ReCaptcha should go. theme: 'blackglass' }); } Can anyone shed any light on this ? Thanks, Eoin C

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  • UITableView with background UIImageView hides table controls

    - by Khanzor
    I am having a problem setting the background of UITableView to a UIImageView (see below for why I am doing this), once the view is set, it works fine, and scrolls with the UITableView, but it hides the elements of the Table View. I need to have a UIImageView as the background for a UITableView. I know this has been answered before, but the answers are to use: [UIColor colorWithPatternImage:[UIImage imageNamed:@"myImage.png"]]; Or something like (which I need to use): UIImageView *background = [MainWindow generateBackgroundWithFrame:tableView.bounds]; [tableView addSubview:background]; [tableView sendSubviewToBack:background]; The reason I need to use the latter is because of my generateBackgroundWithFrame method, which takes a large image, and draws a border around that image to the dimensions specified, and clips the remainder of the image: + (UIImageView *) generateBackgroundWithFrame: (CGRect)frame { UIImageView *background = [[[UIImageView alloc] initWithFrame:frame] autorelease]; background.image = [UIImage imageNamed:@"globalBackground.png"]; [background.layer setMasksToBounds:YES]; [background.layer setCornerRadius:10.0]; [background.layer setBorderColor:[[UIColor grayColor] CGColor]]; [background.layer setBorderWidth:3.0]; return background; } Please note: I understand that this might poorly effect performance, but I don't have the resources to go through and make those images for each potential screen in the app. Please do not answer this question with a mindless "you shouldn't do this" response. I am aware that it is possibly the wrong thing to do. How do I show my UITableView control elements? Is there something that I am doing wrong in my delegate? Here is a simplified version: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithFrame:CGRectMake(20, 20, 261, 45) reuseIdentifier:CellIdentifier] autorelease]; cell.accessoryType = UITableViewCellAccessoryDetailDisclosureButton; UIImage *rowBackground; NSString *imageName = @"standAloneTVButton.png"; rowBackground = [UIImage imageNamed:imageName]; UITextView *textView = [[UITextView alloc] initWithFrame:CGRectMake(0, 5, 300, 200)]; textView.backgroundColor = [UIColor clearColor]; textView.textColor = [UIColor blackColor]; textView.font = [UIFont fontWithName:@"Helvetica" size:18.0f]; Purchase *purchase = [[PurchaseModel productsPurchased] objectAtIndex:indexPath.row]; textView.text = [purchase Title]; selectedTextView.text = textView.text; UIImageView *normalBackground = [[[UIImageView alloc] init] autorelease]; normalBackground.image = rowBackground; [normalBackground insertSubview:textView atIndex:0]; cell.backgroundView = normalBackground; [textView release]; } return cell; }

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  • Which functions in the C standard library commonly encourage bad practice?

    - by Ninefingers
    Hello all, This is inspired by this question and the comments on one particular answer in that I learnt that strncpy is not a very safe string handling function in C and that it pads zeros, until it reaches n, something I was unaware of. Specifically, to quote R.. strncpy does not null-terminate, and does null-pad the whole remainder of the destination buffer, which is a huge waste of time. You can work around the former by adding your own null padding, but not the latter. It was never intended for use as a "safe string handling" function, but for working with fixed-size fields in Unix directory tables and database files. snprintf(dest, n, "%s", src) is the only correct "safe strcpy" in standard C, but it's likely to be a lot slower. By the way, truncation in itself can be a major bug and in some cases might lead to privilege elevation or DoS, so throwing "safe" string functions that truncate their output at a problem is not a way to make it "safe" or "secure". Instead, you should ensure that the destination buffer is the right size and simply use strcpy (or better yet, memcpy if you already know the source string length). And from Jonathan Leffler Note that strncat() is even more confusing in its interface than strncpy() - what exactly is that length argument, again? It isn't what you'd expect based on what you supply strncpy() etc - so it is more error prone even than strncpy(). For copying strings around, I'm increasingly of the opinion that there is a strong argument that you only need memmove() because you always know all the sizes ahead of time and make sure there's enough space ahead of time. Use memmove() in preference to any of strcpy(), strcat(), strncpy(), strncat(), memcpy(). So, I'm clearly a little rusty on the C standard library. Therefore, I'd like to pose the question: What C standard library functions are used inappropriately/in ways that may cause/lead to security problems/code defects/inefficiencies? In the interests of objectivity, I have a number of criteria for an answer: Please, if you can, cite design reasons behind the function in question i.e. its intended purpose. Please highlight the misuse to which the code is currently put. Please state why that misuse may lead towards a problem. I know that should be obvious but it prevents soft answers. Please avoid: Debates over naming conventions of functions (except where this unequivocably causes confusion). "I prefer x over y" - preference is ok, we all have them but I'm interested in actual unexpected side effects and how to guard against them. As this is likely to be considered subjective and has no definite answer I'm flagging for community wiki straight away. I am also working as per C99.

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  • How to Solve N-Queens Problem in Scheme?

    - by Philip
    Hi, I'm stuck on the extended exercise 28.2 of How to Design Programs. Here is the link to the question: http://www.htdp.org/2003-09-26/Book/curriculum-Z-H-35.html#node_chap_28 I used a vector of true or false values to represent the board instead of using a list. This is what I've got which doesn't work: #lang Scheme (define-struct posn (i j)) ;takes in a position in i, j form and a board and returns a natural number that represents the position in index form ;example for board xxx ; xxx ; xxx ;(0, 1) - 1 ;(2, 1) - 7 (define (board-ref a-posn a-board) (+ (* (sqrt (vector-length a-board)) (posn-i a-posn)) (posn-j a-posn))) ;reverse of the above function ;1 - (0, 1) ;7 - (2, 1) (define (get-posn n a-board) (local ((define board-length (sqrt (vector-length a-board)))) (make-posn (floor (/ n board-length)) (remainder n board-length)))) ;determines if posn1 threatens posn2 ;true if they are on the same row/column/diagonal (define (threatened? posn1 posn2) (cond ((= (posn-i posn1) (posn-i posn2)) #t) ((= (posn-j posn1) (posn-j posn2)) #t) ((= (abs (- (posn-i posn1) (posn-i posn2))) (abs (- (posn-j posn1) (posn-j posn2)))) #t) (else #f))) ;returns a list of positions that are not threatened or occupied by queens ;basically any position with the value true (define (get-available-posn a-board) (local ((define (get-ava index) (cond ((= index (vector-length a-board)) '()) ((vector-ref a-board index) (cons index (get-ava (add1 index)))) (else (get-ava (add1 index)))))) (get-ava 0))) ;consume a position in the form of a natural number and a board ;returns a board after placing a queen on the position of the board (define (place n a-board) (local ((define (foo x) (cond ((not (board-ref (get-posn x a-board) a-board)) #f) ((threatened? (get-posn x a-board) (get-posn n a-board)) #f) (else #t)))) (build-vector (vector-length a-board) foo))) ;consume a list of positions in the form of natural number and consumes a board ;returns a list of boards after placing queens on each of the positions on the board (define (place/list alop a-board) (cond ((empty? alop) '()) (else (cons (place (first alop) a-board) (place/list (rest alop) a-board))))) ;returns a possible board after placing n queens on a-board ;returns false if impossible (define (placement n a-board) (cond ((zero? n) a-board) (else (local ((define available-posn (get-available-posn a-board))) (cond ((empty? available-posn) #f) (else (or (placement (sub1 n) (place (first available-posn) a-board)) (placement/list (sub1 n) (place/list (rest available-posn) a-board))))))))) ;returns a possible board after placing n queens on a list of boards ;returns false if all the boards are not valid (define (placement/list n boards) (cond ((empty? boards) #f) ((zero? n) (first boards)) ((not (boolean? (placement n (first boards)))) (first boards)) (else (placement/list n (rest boards)))))

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  • UITableViewCells appear behind backgroundView

    - by Khanzor
    I am having a problem setting the background of UITableView to a UIImageView (see below for why I am doing this), once the view is set, it works fine, and scrolls with the UITableView, but it hides the elements of the Table View. I need to have a UIImageView as the background for a UITableView. I know this has been answered before, but the answers are to use: [UIColor colorWithPatternImage:[UIImage imageNamed:@"myImage.png"]]; Or something like (which I need to use): UIImageView *background = [MainWindow generateBackgroundWithFrame:tableView.bounds]; [tableView addSubview:background]; [tableView sendSubviewToBack:background]; The reason I need to use the latter is because of my generateBackgroundWithFrame method, which takes a large image, and draws a border around that image to the dimensions specified, and clips the remainder of the image: + (UIImageView *) generateBackgroundWithFrame: (CGRect)frame { UIImageView *background = [[[UIImageView alloc] initWithFrame:frame] autorelease]; background.image = [UIImage imageNamed:@"globalBackground.png"]; [background.layer setMasksToBounds:YES]; [background.layer setCornerRadius:10.0]; [background.layer setBorderColor:[[UIColor grayColor] CGColor]]; [background.layer setBorderWidth:3.0]; return background; } Please note: I understand that this might poorly effect performance, but I don't have the resources to go through and make those images for each potential screen in the app. Please do not answer this question with a mindless "you shouldn't do this" response. I am aware that it is possibly the wrong thing to do. How do I show my UITableView control elements? Is there something that I am doing wrong in my delegate? Here is a simplified version: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithFrame:CGRectMake(20, 20, 261, 45) reuseIdentifier:CellIdentifier] autorelease]; cell.accessoryType = UITableViewCellAccessoryDetailDisclosureButton; UIImage *rowBackground; NSString *imageName = @"standAloneTVButton.png"; rowBackground = [UIImage imageNamed:imageName]; UITextView *textView = [[UITextView alloc] initWithFrame:CGRectMake(0, 5, 300, 200)]; textView.backgroundColor = [UIColor clearColor]; textView.textColor = [UIColor blackColor]; textView.font = [UIFont fontWithName:@"Helvetica" size:18.0f]; Purchase *purchase = [[PurchaseModel productsPurchased] objectAtIndex:indexPath.row]; textView.text = [purchase Title]; selectedTextView.text = textView.text; UIImageView *normalBackground = [[[UIImageView alloc] init] autorelease]; normalBackground.image = rowBackground; [normalBackground insertSubview:textView atIndex:0]; cell.backgroundView = normalBackground; [textView release]; } return cell; }

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  • IE6 "frame" layout with 100% height and scrollbars

    - by Joe
    I want to achieve a simple "frame" layout with fixed header, fixed left navigation area, and a main content area that fills 100% of the remainder of the viewport with scrollbars if necessary. My best attempt is below - but when I add enough content to the main div to force scrolling, I see that the scrollbar extends below the bottom of the viewport. What am I doing wrong? Or what is IE6 doing wrong and how can I fix it? NB please don't recommend using a more recent browser - I'd love to but can't. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head> <title></title> <style type="text/css"> html, body { height:100%; margin:0; padding:0; overflow:hidden; } div { border:0; margin:0; padding:0; } div#top { background-color:#dddddd; height:100px; } div#left { background-color:#dddddd; float:left; width:120px; height:100%; overflow:hidden; } div#main { height:100%; overflow:auto; } </style> </head> <body> <div id="top">Title</div> <div id="left">LeftNav</div> <div id="main"> Content <p> Lorem ipsum ... </p> ... repeated several times ... </div> </body> </html>

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  • Scared of Calculus - Required to pass Differential Calculus as part of my Computer science major

    - by ke3pup
    Hi guys I'm finishing my Computer science degree in university but my fear of maths (lack of background knowledge) made me to leave all my maths units til' the very end which is now. i either take them on and pass or have to give up. I've passed all my programming units easily but knowing my poor maths skills won't do i've been staying clear of the maths units. I have to pass Differential Calculus and Linear Algebra first. With a help of book named "Linear Algebra: A Modern Introduction" i'm finding myself on track and i think i can pass the Linear Algebra unit. But with differential calculus i can't find a book to help me. They're either too advanced or just too simple for what i have to learn. The things i'm required to know for this units are: Set notation, the real number line, Complex numbers in cartesian form. Complex plane, modulus. Complex numbers in polar form. De Moivre’s Theorem. Complex powers and nth roots. Definition of ei? and ez for z complex. Applications to trigonometry. Revision of domain and range of a function Working in R3. Curves and surfaces. Functions of 2 variables. Level curves.Partial derivatives and tangent planes. The derivative as a difference quotient. Geometric significance of the derivative. Discussion of limit. Higher order partial derivatives. Limits of f(x,y). Continuity. Maxima and minima of f(x,y). The chain rule. Implicit differentiation. Directional derivatives and the gradient. Limit laws, l’Hoˆpital’s rule, composition law. Definition of sinh and cosh and their inverses. Taylor polynomials. The remainder term. Taylor series. Is there a book to help me get on track with the above? Being a student i can't buy too many books hence why i'm looking for a book that covers topics I need to know. The University library has a fairly limited collection which i took as loan but didn't find useful as it was too complex.

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  • Redundant margins when adding ImageView to ScrollView in Android.

    - by Shmuel Meymann
    Hi.. I have been trying to use a ScrollView on a single ImageView with a JPG (~770 x 1024) over an AVD that's 600x800. My main.xml is: <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <ScrollView android:id="@+id/scroller" android:layout_width="fill_parent" android:layout_height="wrap_content" /> </LinearLayout> Now, I add a single ImageView with setContentView(R.layout.main); ScrollView sv = (ScrollView)findViewById( R.id.scroller ); ImageView iv = new ImageView(this); iv.setImageDrawable( new BitmapDrawable( "/sdcard/770x1024.jpg" ) ); // same happens with ScaleDrawable. iv.setScaleType( ScaleType.CENTER_INSIDE ); sv.addView( sv ); // and it does not go any better if I use Linear Layout between the ScrollView and the ImageView. The result is The image was displayed in a middle of a ScrollView, wrapped with background area on top and bottom as following: ##### ##### image . . . ##### ##### Where ##### stands for background area I tried to set the background of the ImageView red, and it verified that the blank margins were ImageView background. iv.setBackgroundColor( color.Red ); Where I would expect the image to take no more than its size (scaled to the AVD size) and I expect the ScrollView to let me scroll over the remainder (if any). For some reason, I see that the drawable size is 600x1024. Moreover I tried to add a LinearLayout with a dummy text view such as the linear layout is a parent to the ImageView and the TextView, and the ScrollView is a parent to the LinearLayout. LinearLayout dummy = new LinearLayout( this ); dummy.addView(iv); TextView someTextView = new TextView( this ); someTextView.setLayoutParams(new LayoutParams( LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT )); dummy.addView( someTextView ); sv.addView( dummy ); The result was very peculiar: The entire layout was set into the width of a text-less text view (19). It is important for me to avoid stretching the image. What is the recommended way to implement a display of a page that can be potentially scrolled? Do I have to do it manually with a plain layout and scrolling upon OnMove events? Thanks Shmuel

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  • XSD sequence shows as abiguous!

    - by Tim C
    I have an XSD which was transformed from a RELAX NG schema with a few errors I am trying to fix. The big issue I have it with the following <xs:element name="list"> <xs:complexType> <xs:sequence> <xs:choice> <xs:sequence> <xs:element minOccurs="0" ref="preamble"/> <xs:element minOccurs="0" ref="title"/> </xs:sequence> <xs:sequence> <xs:element minOccurs="0" ref="title"/> <xs:element minOccurs="0" ref="preamble"/> </xs:sequence> </xs:choice> <xs:group maxOccurs="unbounded" ref="block-selectionListItem"/> </xs:sequence> <xs:attributeGroup ref="attlist-selectionList"/> </xs:complexType> </xs:element> As you can see the xs:choice block allows you to pick between two xs:sequence blocks. Seems to make sense except that Visual Studio gives the following warning on the second <xs:element minOccurs="0" ref="title/> element which is throwing everything off: Multiple definition of element 'title' causes the content model to become ambiguous. A content model must be formed such that during validation of an element information item sequence, the particle contained directly, indirectly or implicitly therein with which to attempt to validate each item in the sequence in turn can be uniquely determined without examining the content or attributes of that item, and without any information about the items in the remainder of the sequence. Because you can only choose one I do not see how this is ambiguous. Any help would be greatly appreciated! Edit: To be a bit more concise here are the possible outputs of the XML that would validate with this schema: <list> <preamble>My Preamble</preamble> <title>My Title</title> </list> or: <list> <title>My Title</title> <preamble>My Preamble</preamble> </list> As you can see it can be either one way or the other but not both. Also you could just have a title or a preamble and not both.

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  • Finding what makes strings unique in a list, can you improve on brute force?

    - by Ed Guiness
    Suppose I have a list of strings where each string is exactly 4 characters long and unique within the list. For each of these strings I want to identify the position of the characters within the string that make the string unique. So for a list of three strings abcd abcc bbcb For the first string I want to identify the character in 4th position d since d does not appear in the 4th position in any other string. For the second string I want to identify the character in 4th position c. For the third string it I want to identify the character in 1st position b AND the character in 4th position, also b. This could be concisely represented as abcd -> ...d abcc -> ...c bbcb -> b..b If you consider the same problem but with a list of binary numbers 0101 0011 1111 Then the result I want would be 0101 -> ..0. 0011 -> .0.. 1111 -> 1... Staying with the binary theme I can use XOR to identify which bits are unique within two binary numbers since 0101 ^ 0011 = 0110 which I can interpret as meaning that in this case the 2nd and 3rd bits (reading left to right) are unique between these two binary numbers. This technique might be a red herring unless somehow it can be extended to the larger list. A brute-force approach would be to look at each string in turn, and for each string to iterate through vertical slices of the remainder of the strings in the list. So for the list abcd abcc bbcb I would start with abcd and iterate through vertical slices of abcc bbcb where these vertical slices would be a | b | c | c b | b | c | b or in list form, "ab", "bb", "cc", "cb". This would result in four comparisons a : ab -> . (a is not unique) b : bb -> . (b is not unique) c : cc -> . (c is not unique) d : cb -> d (d is unique) or concisely abcd -> ...d Maybe it's wishful thinking, but I have a feeling that there should be an elegant and general solution that would apply to an arbitrarily large list of strings (or binary numbers). But if there is I haven't yet been able to see it. I hope to use this algorithm to to derive minimal signatures from a collection of unique images (bitmaps) in order to efficiently identify those images at a future time. If future efficiency wasn't a concern I would use a simple hash of each image. Can you improve on brute force?

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  • bin_at in dlmalloc

    - by chunhui
    In glibc malloc.c or dlmalloc It said "repositioning tricks"As in blew, and use this trick in bin_at. bins is a array,the space is allocated when av(struct malloc_state) is allocated.doesn't it? the sizeof(bin[i]) is less then sizeof(struct malloc_chunk*)? Who can describe this trick for me? I can't understand the bin_at macro.why they get the bins address use this method?how it works? Very thanks,and sorry for my poor English. /* To simplify use in double-linked lists, each bin header acts as a malloc_chunk. This avoids special-casing for headers. But to conserve space and improve locality, we allocate only the fd/bk pointers of bins, and then use repositioning tricks to treat these as the fields of a malloc_chunk*. */ typedef struct malloc_chunk* mbinptr; /* addressing -- note that bin_at(0) does not exist */ #define bin_at(m, i) \ (mbinptr) (((char *) &((m)->bins[((i) - 1) * 2])) \ - offsetof (struct malloc_chunk, fd)) The malloc_chunk struct like this: struct malloc_chunk { INTERNAL_SIZE_T prev_size; /* Size of previous chunk (if free). */ INTERNAL_SIZE_T size; /* Size in bytes, including overhead. */ struct malloc_chunk* fd; /* double links -- used only if free. */ struct malloc_chunk* bk; /* Only used for large blocks: pointer to next larger size. */ struct malloc_chunk* fd_nextsize; /* double links -- used only if free. */ struct malloc_chunk* bk_nextsize; }; And the bin type like this: typedef struct malloc_chunk* mbinptr; struct malloc_state { /* Serialize access. */ mutex_t mutex; /* Flags (formerly in max_fast). */ int flags; #if THREAD_STATS /* Statistics for locking. Only used if THREAD_STATS is defined. */ long stat_lock_direct, stat_lock_loop, stat_lock_wait; #endif /* Fastbins */ mfastbinptr fastbinsY[NFASTBINS]; /* Base of the topmost chunk -- not otherwise kept in a bin */ mchunkptr top; /* The remainder from the most recent split of a small request */ mchunkptr last_remainder; /* Normal bins packed as described above */ mchunkptr bins[NBINS * 2 - 2]; /* Bitmap of bins */ unsigned int binmap[BINMAPSIZE]; /* Linked list */ struct malloc_state *next; #ifdef PER_THREAD /* Linked list for free arenas. */ struct malloc_state *next_free; #endif /* Memory allocated from the system in this arena. */ INTERNAL_SIZE_T system_mem; INTERNAL_SIZE_T max_system_mem; };

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  • Flip clock showing time issue (animations invovled)

    - by Hwang
    I'm creating a flip clock (clock where you always see in airport), but I can't seems to get the time to show at the correct timing. After the flip, then will see the number changing. But I want it to change before it flips. Currently I'm not sure whether is the animation problem, or isit I have to do something else on the script. I've uploaded the FLA so that you could have a look on how I set up the flipping animation. http://www.mediafire.com/?nzmymjgtntz Below is the AS3 code: package { import flash.display.MovieClip; import flash.events.TimerEvent; import flash.utils.Timer; public class flipClock extends MovieClip { private var clock:clockMC=new clockMC(); //seconds private var secTop1=clock.second.top1.digit; private var secTop2=clock.second.top2.digit; private var secBot1=clock.second.bot1.digit; private var secBot2=clock.second.bot2.digit; private var seconds:Number; private var minutes:Number; private var hours:Number; private var days:Number; public function flipClock():void { decrease(); addChild(clock); } private function decrease():void { var countdownTimer:Timer=new Timer(1000); //Adding an event listener to the timer object countdownTimer.addEventListener(TimerEvent.TIMER,updateTime); //Initializing timer object countdownTimer.start(); } private function updateTime(event:TimerEvent):void { decreasTimerFunction(); updateSecond(); //updateMinute(); } private function updateSecond():void { clock.second.play(); secTop1.text=num2; secTop2.text=num1; if (num1<10) { num1="0"+num1; } if (num2<10) { num2="0"+num2; } if (num1==60) { num1=0; } if (num2==60) { num2=0; } secTop1.text=num1; secTop2.text=num2; //secBot1.text=num1; //secBot2.text=num2; } private function decreasTimerFunction():void { //Create a date object for Christmas Morning var endTime:Date=new Date(2010,4,26,0,0,0,0); //Current date object var now:Date=new Date(); // Set the difference between the two date and times in milliseconds var timeDiff:Number=endTime.getTime()-now.getTime(); seconds=Math.floor(timeDiff/1000); minutes=Math.floor(seconds/60); hours=Math.floor(minutes/60); days=Math.floor(hours/24); // Set the remainder of the division vars above hours%=24; minutes%=60; seconds%=60; } } }

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  • How do I print out objects in an array in python?

    - by Jonathan
    I'm writing a code which performs a k-means clustering on a set of data. I'm actually using the code from a book called collective intelligence by O'Reilly. Everything works, but in his code he uses the command line and i want to write everything in notepad++. As a reference his line is >>>kclust=clusters.kcluster(data,k=10) >>>[rownames[r] for r in k[0]] Here is my code: from PIL import Image,ImageDraw def readfile(filename): lines=[line for line in file(filename)] # First line is the column titles colnames=lines[0].strip( ).split('\t')[1:] rownames=[] data=[] for line in lines[1:]: p=line.strip( ).split('\t') # First column in each row is the rowname rownames.append(p[0]) # The data for this row is the remainder of the row data.append([float(x) for x in p[1:]]) return rownames,colnames,data from math import sqrt def pearson(v1,v2): # Simple sums sum1=sum(v1) sum2=sum(v2) # Sums of the squares sum1Sq=sum([pow(v,2) for v in v1]) sum2Sq=sum([pow(v,2) for v in v2]) # Sum of the products pSum=sum([v1[i]*v2[i] for i in range(len(v1))]) # Calculate r (Pearson score) num=pSum-(sum1*sum2/len(v1)) den=sqrt((sum1Sq-pow(sum1,2)/len(v1))*(sum2Sq-pow(sum2,2)/len(v1))) if den==0: return 0 return 1.0-num/den class bicluster: def __init__(self,vec,left=None,right=None,distance=0.0,id=None): self.left=left self.right=right self.vec=vec self.id=id self.distance=distance def hcluster(rows,distance=pearson): distances={} currentclustid=-1 # Clusters are initially just the rows clust=[bicluster(rows[i],id=i) for i in range(len(rows))] while len(clust)>1: lowestpair=(0,1) closest=distance(clust[0].vec,clust[1].vec) # loop through every pair looking for the smallest distance for i in range(len(clust)): for j in range(i+1,len(clust)): # distances is the cache of distance calculations if (clust[i].id,clust[j].id) not in distances: distances[(clust[i].id,clust[j].id)]=distance(clust[i].vec,clust[j].vec) #print 'i' #print i #print #print 'j' #print j #print d=distances[(clust[i].id,clust[j].id)] if d<closest: closest=d lowestpair=(i,j) # calculate the average of the two clusters mergevec=[ (clust[lowestpair[0]].vec[i]+clust[lowestpair[1]].vec[i])/2.0 for i in range(len(clust[0].vec))] # create the new cluster newcluster=bicluster(mergevec,left=clust[lowestpair[0]], right=clust[lowestpair[1]], distance=closest,id=currentclustid) # cluster ids that weren't in the original set are negative currentclustid-=1 del clust[lowestpair[1]] del clust[lowestpair[0]] clust.append(newcluster) return clust[0] def kcluster(rows,distance=pearson,k=4): # Determine the minimum and maximum values for each point ranges=[(min([row[i] for row in rows]),max([row[i] for row in rows])) for i in range(len(rows[0]))] # Create k randomly placed centroids clusters=[[random.random( )*(ranges[i][1]-ranges[i][0])+ranges[i][0] for i in range(len(rows[0]))] for j in range(k)] lastmatches=None for t in range(100): print 'Iteration %d' % t bestmatches=[[] for i in range(k)] # Find which centroid is the closest for each row for j in range(len(rows)): row=rows[j] bestmatch=0 for i in range(k): d=distance(clusters[i],row) if d<distance(clusters[bestmatch],row): bestmatch=i bestmatches[bestmatch].append(j) # If the results are the same as last time, this is complete if bestmatches==lastmatches: break lastmatches=bestmatches # Move the centroids to the average of their members for i in range(k): avgs=[0.0]*len(rows[0]) if len(bestmatches[i])>0: for rowid in bestmatches[i]: for m in range(len(rows[rowid])): avgs[m]+=rows[rowid][m] for j in range(len(avgs)): avgs[j]/=len(bestmatches[i]) clusters[i]=avgs return bestmatches

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