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  • Design Philosophy Question - When to create new functions

    - by Eclyps19
    This is a general design question not relating to any language. I'm a bit torn between going for minimum code or optimum organization. I'll use my current project as an example. I have a bunch of tabs on a form that perform different functions. Lets say Tab 1 reads in a file with a specific layout, tab 2 exports a file to a specific location, etc. The problem I'm running into now is that I need these tabs to do something slightly different based on the contents of a variable. If it contains a 1 I may need to use Layout A and perform some extra concatenation, if it contains a 2 I may need to use Layout B and do no concatenation but add two integer fields, etc. There could be 10+ codes that I will be looking at. Is it more preferable to create an individual path for each code early on, or attempt to create a single path that branches out only when absolutely required. Creating an individual path for each code would allow my code to be extremely easy to follow at a glance, which in turn will help me out later on down the road when debugging or making changes. The downside to this is that I will increase the amount of code written by calling some of the same functions in multiple places (for example, steps 3, 5, and 9 for every single code may be exactly the same. Creating a single path that would branch out only when required will be a bit messier and more difficult to follow at a glance, but I would create less code by placing conditionals only at steps that are unique. I realize that this may be a case-by-case decision, but in general, if you were handed a previously built program to work on, which would you prefer?

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  • Thread management advice - Is TPL a good idea?

    - by Ian
    I'm hoping to get some advice on the use of thread managment and hopefully the task parallel library, because I'm not sure I've been going down the correct route. Probably best is that I give an outline of what I'm trying to do. Given a Problem I need to generate a Solution using a heuristic based algorithm. I start of by calculating a base solution, this operation I don't think can be parallelised so we don't need to worry about. Once the inital solution has been generated, I want to trigger n threads, which attempt to find a better solution. These threads need to do a couple of things: They need to be initalized with a different 'optimization metric'. In other words they are attempting to optimize different things, with a precedence level set within code. This means they all run slightly different calculation engines. I'm not sure if I can do this with the TPL.. If one of the threads finds a better solution that the currently best known solution (which needs to be shared across all threads) then it needs to update the best solution, and force a number of other threads to restart (again this depends on precedence levels of the optimization metrics). I may also wish to combine certain calculations across threads (e.g. keep a union of probabilities for a certain approach to the problem). This is probably more optional though. The whole system needs to be thread safe obviously and I want it to be running as fast as possible. I tried quite an implementation that involved managing my own threads and shutting them down etc, but it started getting quite complicated, and I'm now wondering if the TPL might be better. I'm wondering if anyone can offer any general guidance? Thanks...

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  • How to do HABTM management with auto completion in Rails?

    - by Andrei
    I am looking for a good solution for a probably typical problem of managing models with HABTM association in Rails. Let's assume that we have two models -- products and categories: Products has_many :categorizations has_many :categories, :through => :categorizations Categories has_many :categorizations has_many :products, :through => :categorizations Categorization belongs_to :product belongs_to :category Pat Shaughnessy is developing modified auto_complete plugin which can allow to manage one-to-many (and many-to-many) association: For someone that would be enough, but I don't really like so many text fields. I guess it is possible to combine the Ryan Bates' screencasts used by Pat in a slightly different way, namely, using one text field with autocomplete: Also it would be better to remove from the list of suggested tasks (one-to-many), or products|categories (many-to-many) those which have been already added. In the case of products-categories relationship, such auto completion would be used both in the form for product, and in the form for category. I hope that there is an existing plugin for that. I am not very experienced in Ruby, and don't really know how to implement such logic by myself. Any help is appreciated!

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  • Executing logic before save or validation with EF Code-First Models

    - by Ryan Norbauer
    I'm still getting accustomed to EF Code First, having spent years working with the Ruby ORM, ActiveRecord. ActiveRecord used to have all sorts of callbacks like before_validation and before_save, where it was possible to modify the object before it would be sent off to the data layer. I am wondering if there is an equivalent technique in EF Code First object modeling. I know how to set object members at the time of instantiation, of course, (to set default values and so forth) but sometimes you need to intervene at different moments in the object lifecycle. To use a slightly contrived example, say I have a join table linking Authors and Plays, represented with a corresponding Authoring object: public class Authoring { public int ID { get; set; } [Required] public int Position { get; set; } [Required] public virtual Play Play { get; set; } [Required] public virtual Author Author { get; set; } } where Position represents a zero-indexed ordering of the Authors associated to a given Play. (You might have a single "South Pacific" Play with two authors: a "Rodgers" author with a Position 0 and a "Hammerstein" author with a Position 1.) Let's say I wanted to create a method that, before saving away an Authoring record, it checked to see if there were any existing authors for the Play to which it was associated. If no, it set the Position to 0. If yes, it would find set the Position of the highest value associated with that Play and increment by one. Where would I implement such logic within an EF code first model layer? And, in other cases, what if I wanted to massage data in code before it is checked for validation errors? Basically, I'm looking for an equivalent to the Rails lifecycle hooks mentioned above, or some way to fake it at least. :)

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  • How to control dojo widget classes, or how to get fine-grained control of style

    - by djna
    I am creating a UI with dojo that is emulting some aspects of an existing thick client application. I need to programatically put two different menu bars on the same page. I have successfully created the two menu bars using new dijit.Menu(); new dijit.MenuItem(); and so on. Now I want to give them slightly different presentation styles. As I'm going to have quite a few pages of this sort my first thought is to use different CSS style classes. And that's the problem: when I create the Menu and it's items we get quite a set of HTML objects, each with CSS classes specified by dojo, and the classes are the same for the items associated with either menu. How can I best get specific control for any one menu? I could determine the dojo-generated ids for each item, and specify styles by ids, but that seems like hard work. Is there an sensible way to control the classes defined by dojo, or a nice CSS way to select only the items associated with one menu bar?

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  • SqlCE DB occasionally freezes on one handheld, not another

    - by Michael
    I have two types of custom handhelds which are similar, but slightly different, each running the same WinForm application and a WinCE database: Type 1: WinCE 4.2, 400 mhz, 93244 kb Type 2: WinCE 5.0, 520 mhz, 84208 kb Type 1 will happily proceed through a large batch db operation (initiated) by the app, by Type 2 will consistently begin c-r-a-w-l-i-n-g (for several to many cycles) at around the 200 cycle mark. As several points it will begin running normally and then crawl again. The app does several db op's (inserts, updates and selects, no deletes). To simplify my situation, I've built a small test app which essentially does this: command_s.CommandText = "select dvr from vr where vid = 2211250"; command_u.CommandText = "update pvr set LocationID=81 where Status='OK' and vri = 27861"; while(going) { command_s.ExecuteScalar(); command_u.ExecuteNonQuery(); } and set it off running on the two units side by side. Sure enough, the slower (400 mhz) unit is outpacing the faster (520 mhz) unit (it's about 5000 cycles ahead right now) and I can see noticable pauses on the 520 mhz unit. What is causing this?

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  • What's the idiomatic way of inheriting data access functionality as well as object properties?

    - by Knut Arne Vedaa
    Suppose the following (slightly pseudo-code for brevity): class Basic { String foo; } class SomeExtension extends Basic { String bar; } class OtherExtension extends Basic { String baz; } class BasicService { Basic getBasic() { } } class SomeExtensionService extends BasicService { SomeExtension getSomeExtension() { } } class OtherExtensionService extends BasicService { OtherExtension getOtherExtension() { } } What would be the most idiomatic, elegant way to implement the get-() service methods with the most possible code reuse? Obviously you could do it like this: class BasicService { Basic getBasic() { Basic basic = new Basic(); basic.setFoo("some kind of foo"); return basic; } } class SomeExtensionService { SomeExtension getSomeExtension() { SomeExtension someExtension = new SomeExtension; Basic basic = getBasic(); someExtension.setFoo(basic.getFoo()); someExtension.setBar("some kind of bar"); return someExtension; } } But this would be ugly if Basic has a lot of properties, and also you only need one object, as SomeExtension already inherits Basic. However, BasicService can obviously not return a SomeExtension object. You could also have the get methods not create the object themselves, but create it at the outermost level and pass it to the method for filling in the properties, but I find that too imperative. (Please let me know if the question is confusingly formulated.)

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  • Ideas in implenting the following entry form in ASP.NET MVC 2

    - by KiD0M4N
    Hi guys, I have a very simple data entry form to implement. It looks like this: Obviously I have mocked out the actual requirements but the essence is similar. Entering a name and clicking history should bring up a pop up pointing to the url '/student/viewhistory/{name}' Name and age are required fields The sub form (in the mockup) with Class (a drop down, containing the numbers 1 - 10) and Subject (containing A - D, say) form a unique pair of values for which a score is required. So, selecting the Class and Subject, entering a score and clicking on Add should 'add' this record for the student. Then the user should be able to click Save (to persist the entry to the database) or be able to add further (class, subject, score) pairs to the entry. Any ideas how to smartly implement this? (I am coming from a DWH field... so thinking in a stateless manner is slightly foreign to me.) Any help is appreciated. I would imagine a smart use of jQuery would give a easy solution. Regards, Karan

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  • Should the code being tested compile to a DLL or an executable file?

    - by uriDium
    I have a solution with two projects. One for project for the production code and another project for the unit tests. I did this as per the suggestions I got here from SO. I noticed that in the Debug Folder that it includes the production code in executable form. I used NUnit to run the tests after removing the executable and they all fail trying to find the executable. So it definitely is trying to find it. I then did a quick read to find out which is better, a DLL or an executable. It seems that an DLL is much faster as they share memory space where communication between executables is slower. Unforunately our production code needs to be an exectuable. So the unit tests will be slightly slower. I am not too worried about that. But the project does rely on code written in another library which is also in executable format at the moment. Should the projects that expose some sort of SDK rather be compiled to an DLL and then the projects that use the SDK be compiled to executable?

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  • Boost::Asio - Remove the "null"-character in the end of tcp packets.

    - by shump
    I'm trying to make a simple msn client mostly for fun but also for educational purposes. And I started to try some tcp package sending and receiving using Boost Asio as I want cross-platform support. I have managed to send a "VER"-command and receive it's response. However after I send the following "CVR"-command, Asio casts an "End of file"-error. After some further researching I found by packet sniffing that my tcp packets to the messenger server got an extra "null"-character (Ascii code: 00) at the end of the message. This means that my VER-command gets an extra character in the end which I don't think the messenger server like and therefore shuts down the connection when I try to read the CVR response. This is how my package looks when sniffing it, (it's Payload): (Hex:) 56 45 52 20 31 20 4d 53 4e 50 31 35 20 43 56 52 30 0a 0a 00 (Char:) VER 1 MSNP15 CVR 0... and this is how Adium(chat client for OS X)'s package looks: (Hex:) 56 45 52 20 31 20 4d 53 4e 50 31 35 20 43 56 52 30 0d 0a (Char:) VER 1 MSNP15 CVR 0.. So my question is if there is any way to remove the null-character in the end of each package, of if I've misunderstood something and used Asio in a wrong way. My write function (slightly edited) looks lite this: int sendVERMessage() { boost::system::error_code ignored_error; char sendBuf[] = "VER 1 MSNP15 CVR0\r\n"; boost::asio::write(socket, boost::asio::buffer(sendBuf), boost::asio::transfer_all(), ignored_error); if(ignored_error) { cout << "Failed to send to host!" << endl; return 1; } cout << "VER message sent!" << endl; return 0; } And here's the main documentation on the msn protocol I'm using. Hope I've been clear enough.

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  • Circular Reference exception with JSON Serialisation with MVC3 and EF4 CTP5w

    - by nakchak
    Hi I'm having problems with a circular reference when i try and serialise an object returned via EF4 CTP5. Im using the code first approach and simple poco's for my model. I have added [ScriptIgnore] attributes to any properties that provide a back references to an object and annoyingly every seems to work fine if i manually instantiate the poco's, i.e. they serialise to JSON fine, and the scriptignore attribute is acknowledged. However when i try and serialise an object returned from the DAL i get the circular reference exception "A circular reference was detected while serializing an object of type 'System.Data.Entity.DynamicProxies.xxxx'" I have tried several ways of retreiving the data but they all get stuck with this error: public JsonResult GetTimeSlot(int id) { TimeSlotDao tsDao = new TimeSlotDao(); TimeSlot ts = tsDao.GetById(id); return Json(ts); } The method below works slightly better as rather than the timeslot dynamic proxied object causing the circular refference its the appointment object. public JsonResult GetTimeSlot(int id) { TimeSlotDao tsDao = new TimeSlotDao(); var ts = from t in tsDao.GetQueryable() where t.Id == id select new {t.Id, t.StartTime, t.Available, t.Appointment}; return Json(ts); } Any ideas or solutions to this problem? Update I would prefer to use the out of the box serialiser if possible although Json.Net via nuget is ok as an alternative i would hope its possible to use it as I intended as well...

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  • Glitch when moving camera in OpenGL

    - by CG
    I am writing a tile-based game engine for the iPhone and it works in general apart from the following glitch. Basically, the camera will always keep the player in the centre of the screen, and it moves to follow the player correctly and draws everything correctly when stationary. However whilst the player is moving, the tiles of the surface the player is walking on glitch as shown: Compared to the stationary (correct): Does anyone have any idea why this could be? Thanks for the responses so far. Floating point error was my first thought also and I tried slightly increasing the size of the tiles but this did not help. Changing glClearColor to red still leaves black gaps so maybe it isn't floating point error. Since the tiles in general will use different textures, I don't know if vertex arrays can be used (I always thought that the same texture had to be applied to everything in the array, correct me if I'm wrong), and I don't think VBO is available in OpenGL ES. Setting the filtering to nearest neighbour improved things but the glitch still happens every ten frames or so, and the pixelly result means that this solution is not viable anyway. The main difference between what I'm doing now and what I've done in the past is that this time I am moving the camera rather than the stationary objects in the world (i.e. the tiles, the player is still being moved). The code I'm using to move the camera is: void Camera::CentreAtPoint( GLfloat x, GLfloat y ) { glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrthof(x - size.x / 2.0f, x + size.x / 2.0f, y + size.y / 2.0f, y - size.y / 2.0f, 0.01f, 5.0f); glMatrixMode(GL_MODELVIEW); } Is there a problem with doing things this way and if so is there a solution?

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  • firefox render order problem with div tag

    - by flavour404
    I have a div tag which I populate dynamically. The problem is that in Firefox when i do a test for size(height) I seem to need to run it twice in order to get the correct size. This is the code: alert("h = " + h + " height:" + document.getElementById("thumbDiv").clientHeight); Ignore 'h' for the time being, what I am curious to know is what is the correct way to get the div tags height in firefox. In ie I use offsetHeight which works for my purposes perfectly. The other thing is the render order in firefox. I populate the div and then query the height with .clientHeight and I get 102, which is I am assuming the empty height of the tag as I have set no height via style, if I press the button again I then get the height of the div with the enlcosed html page which I am pushing into the div. Its odd, and slightly annoying. I am trying to determine if there is enough room in the browser to display the div contents in their entireity, if not then I am disabling certain features otherwise I get into an infinite scroll problem... Thanks, R. Thanks R.

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  • Using EhCache for session.createCriteria(...).list()

    - by James Smith
    I'm benchmarking the performance gains from using a 2nd level cache in Hibernate (enabling EhCache), but it doesn't seem to improve performance. In fact, the time to perform the query slightly increases. The query is: session.createCriteria(MyEntity.class).list(); The entity is: @Entity @Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE) public class MyEntity { @Id @GeneratedValue private long id; @Column(length=5000) private String data; //---SNIP getters and setters--- } My hibernate.cfg.xml is: <!-- all the normal stuff to get it to connect & map the entities plus:--> <property name="hibernate.cache.region.factory_class"> net.sf.ehcache.hibernate.EhCacheRegionFactory </property> The MyEntity table contains about 2000 rows. The problem is that before adding in the cache, the query above to list all entities took an average of 65 ms. After the cache, they take an average of 74 ms. Is there something I'm missing? Is there something extra that needs to be done that will increase performance?

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  • How do I alter the default style of a button without WPF reverting from Aero to Classic?

    - by DanM
    I've added PresentationFramework.Aero to my App.xaml merged dictionaries, as in... <Application x:Class="TestApp.App" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"> <Application.Resources> <ResourceDictionary> <ResourceDictionary.MergedDictionaries> <ResourceDictionary Source="/PresentationFramework.Aero;component/themes/Aero.NormalColor.xaml" /> <ResourceDictionary Source="pack://application:,,,/WPFToolkit;component/Themes/Aero.NormalColor.xaml" /> <ResourceDictionary Source="ButtonResourceDictionary.xaml" /> </ResourceDictionary.MergedDictionaries> </ResourceDictionary> </Application.Resources> </Application> I'm trying to modify the default look of buttons just slightly. I put this style in my ButtonResourceDictionary: <Style TargetType="Button"> <Setter Property="Padding" Value="3" /> <Setter Property="FontWeight" Value="Bold" /> </Style> All buttons now have the correct padding and bold text, but they look "Classic", not "Aero". How do I fix this style so my buttons all look Aero but also have these minor changes? I would prefer not to have to set the Style property for every button.

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  • Django sub-applications & module structure

    - by Rob Golding
    I am developing a Django application, which is a large system that requires multiple sub-applications to keep things neat. Therefore, I have a top level directory that is a Django app (as it has an empty models.py file), and multiple subdirectories, which are also applications in themselves. The reason I have laid my application out in this way is because the sub-applications are separated, but they would never be used on their own, outside the parent application. It therefore makes no sense to distribute them separately. When installing my application, the settings file has to include something like this: INSTALLED_APPS = ( ... 'myapp', 'myapp.subapp1', 'myapp.subapp2', ... ) ...which is obviously suboptimal. This also has the slightly nasty result of requiring that all the sub-applications are referred to by their "inner" name (i.e. subapp1, subapp2 etc.). For example, if I want to reset the database tables for subapp1, I have to type: python manage.py reset subapp1 This is annoying, especially because I have a sub-app called core - which is likely to conflict with another application's name when my application is installed in a user's project. Am I doing this completely wrongly, or is there away to force these "inner" apps to be referred to by their full name?

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  • Why is search functionality not working on this page?

    - by DaveDev
    we deliver micro-site content for our client. Our content is injected into a wrapper that is supplied by another developer. To deliver our content we host the wrapper as well as the content. The user can access this at http://fundcentre.newireland.ie/ (try a search for 'bloxham') For the other content that is not ours, the other developer hosts a similar (though slightly different) wrapper and delivers the content. the user accesses this here: http://www.newireland.ie/ (try a search for 'bloxham') The wrapper contains a search box, which does not work for us but it works for the other developer. I took a look at the network traffic with FireBug but it appears that when I do the search from the wrapper that we're hosting, I'm getting a "407 Proxy Access Denied" error. My guess is their proxy has a problem with the fact that the search is being conducted from a page hosted outside the scope of their proxy. It was also suggested that there were javascript errors on the page that were preventing the search from executing but I can't see any. Also, I don't think I'd get as far as the proxy error if that was the case. I don't really understand this stuff too well though, so could somebody with a bit more experience please take a look and maybe shed some light on this for me? Thanks.

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  • java: libraries for immutable functional-style data structures

    - by Jason S
    This is very similar to another question (Functional Data Structures in Java) but the answers there are not particularly useful. I need to use immutable versions of the standard Java collections (e.g. HashMap / TreeMap / ArrayList / LinkedList / HashSet / TreeSet). By "immutable" I mean immutable in the functional sense (e.g. purely functional data structures), where updating operations on the data structure do not change the original data, but instead return a new instance of the same kind of data structure. Also typically new and old instances of the data structure will share immutable data to be efficient in time and space. From what I can tell my options include: Functional Java Scala Clojure but I'm not sure whether any of these are particularly appealing to me. I have a few requirements/desirements: the collections in question should be usable directly in Java (with the appropriate libraries in the classpath). FJ would work for me; I'm not sure if I can use Scala's or Clojure's data structures in Java w/o having to use the compilers/interpreters from those languages and w/o having to write Scala or Clojure code. Core operations on lists/maps/sets should be possible w/o having to create function objects with confusing syntaxes (FJ looks slightly iffy) They should be efficient in time and space. I'm looking for a library which ideally has done some performance testing. FJ's TreeMap is based on a red-black tree, not sure how that rates. Documentation / tutorials should be good enough so someone can get started quickly using the data structures. FJ fails on that front. Any suggestions?

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  • iPhone crashing when presenting modal view controller

    - by Michael Waterfall
    I'm trying to display a modal view straight after another view has been presented modally (the second is a loading view that appears). - (void)viewDidAppear:(BOOL)animated { [super viewDidAppear:animated]; // Show load LoadViewController *loader = [[LoadViewController alloc] init]; [self presentModalViewController: loader animated:NO]; [loader release]; } But when I do this I get a "Program received signal: "EXC_BAD_ACCESS"." error. The stack trace is: 0 0x30b43234 in -[UIWindowController transitionViewDidComplete:fromView:toView:] 1 0x3095828e in -[UITransitionView notifyDidCompleteTransition:] 2 0x3091af0d in -[UIViewAnimationState sendDelegateAnimationDidStop:finished:] 3 0x3091ad7c in -[UIViewAnimationState animationDidStop:finished:] 4 0x0051e331 in run_animation_callbacks 5 0x0051e109 in CA::timer_callback 6 0x302454a0 in CFRunLoopRunSpecific 7 0x30244628 in CFRunLoopRunInMode 8 0x32044c31 in GSEventRunModal 9 0x32044cf6 in GSEventRun 10 0x309021ee in UIApplicationMain 11 0x00002154 in main at main.m:14 Any ideas? I'm totally stumped! The loading view is empty so there's definitely nothing going on in there that's causing the error. Is it something to do with launching 2 views modally in the same event loop or something? Thanks, Mike Edit: Very strange... I have modified it slightly so that the loading view is shown after a tiny delay, and this works fine! So it appears to be something within the same event loop! - (void)viewDidAppear:(BOOL)animated { [super viewDidAppear:animated]; // Show load [self performSelector:@selector(doit) withObject:nil afterDelay:0.1]; } - (void)doit { [self presentModalViewController:loader animated:YES]; }

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  • Using JMX classes to notify on events over time

    - by Cincinnati Joe
    I've been looking at JMX for monitoring application and system metrics (partially because MBeans can accessed by various tools such as JConsole). It would seem like the classes included with JMX would be useful for things like notification when metrics have exceeded thresholds. But I'm not sure they fit with the way I want to measure these over a specified time period. For example, let's say I want to notify an admin when the average CPU load is over 95% for more than 5 minutes. Is that something can be done with a GaugeMonitor? From the docs, it doesn't seem quite suited for this, and I'm wondering if instead I should write my own MBean with the necessary logic. A more relevant example is when the login times for users exceed 10s over a period of 5 mins. Slightly different would be the last 20 logins took more than 10s on average. Another case would be when a process crashes 4+ times in an hour. Or the request queue exceeds 15 for 5 mins. Are the JMX Monitor classes useful for this kind of thing?

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  • Customizing the Stars Image for Ajaxful_Rating RoR plugin

    - by Kevin
    I'm trying to come up with my own star image that's slightly smaller and different style than the one provided in the gem/plugin, but Ajaxful_rating doesn't have an easy way to do this. Here's what I've figured out so far: The stars.png in the public folder is three 25x25 pixel tiles stacked vertically, ordered empty star, normal star, and hover star. I'm assuming as long as you keep the above constraints, you should be fine without modifying any other files. But what if you want to change the image size of the stars to larger or smaller? I've found where you can change the height in the stylesheets/ajaxful_rating.css .ajaxful-rating{ position: relative; /*width: 125px; this is setted dynamically */ height: 25px; overflow: hidden; list-style: none; margin: 0; padding: 0; background-position: left top; } .ajaxful-rating li{ display: inline; } .ajaxful-rating a, .ajaxful-rating span, .ajaxful-rating .show-value{ position: absolute; top: 0; left: 0; text-indent: -1000em; height: 25px; line-height: 25px; outline: none; overflow: hidden; border: none; } You just need to change every place that says "25px" above to whatever height your new star image is. This works fine but doesn't display the horizontal part correctly. Anyone know where I would look to set the horizontal part as well? (I'm assuming it's in an .rb file somewhere based upon how many stars you specified in your ajaxful_rating setup)

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  • What algorithms compute directions from point A to point B on a map?

    - by A. Rex
    How do map providers (such as Google or Yahoo! Maps) suggest directions? I mean, they probably have real-world data in some form, certainly including distances but also perhaps things like driving speeds, presence of sidewalks, train schedules, etc. But suppose the data were in a simpler format, say a very large directed graph with edge weights reflecting distances. I want to be able to quickly compute directions from one arbitrary point to another. Sometimes these points will be close together (within one city) while sometimes they will be far apart (cross-country). Graph algorithms like Dijkstra's algorithm will not work because the graph is enormous. Luckily, heuristic algorithms like A* will probably work. However, our data is very structured, and perhaps some kind of tiered approach might work? (For example, store precomputed directions between certain "key" points far apart, as well as some local directions. Then directions for two far-away points will involve local directions to a key points, global directions to another key point, and then local directions again.) What algorithms are actually used in practice? PS. This question was motivated by finding quirks in online mapping directions. Contrary to the triangle inequality, sometimes Google Maps thinks that X-Z takes longer and is farther than using an intermediate point as in X-Y-Z. But maybe their walking directions optimize for another parameter, too? PPS. Here's another violation of the triangle inequality that suggests (to me) that they use some kind of tiered approach: X-Z versus X-Y-Z. The former seems to use prominent Boulevard de Sebastopol even though it's slightly out of the way. (Edit: this example doesn't work anymore, but did at the time of the original post. The one above still works as of early November 2009.)

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  • In-order tree traversal

    - by Chris S
    I have the following text from an academic course I took a while ago about in-order traversal (they also call it pancaking) of a binary tree (not BST): In-order tree traversal Draw a line around the outside of the tree. Start to the left of the root, and go around the outside of the tree, to end up to the right of the root. Stay as close to the tree as possible, but do not cross the tree. (Think of the tree — its branches and nodes — as a solid barrier.) The order of the nodes is the order in which this line passes underneath them. If you are unsure as to when you go “underneath” a node, remember that a node “to the left” always comes first. Here's the example used (slightly different tree from below) However when I do a search on google, I get a conflicting definition. For example the wikipedia example: Inorder traversal sequence: A, B, C, D, E, F, G, H, I (leftchild,rootnode,right node) But according to (my understanding of) definition #1, this should be A, B, D, C, E, F, G, I, H Can anyone clarify which definition is correct? They might be both describing different traversal methods, but happen to be using the same name. I'm having trouble believing the peer-reviewed academic text is wrong, but can't be certain.

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  • Inheritance and type parameters of Traversable

    - by Jesper
    I'm studying the source code of the Scala 2.8 collection classes. I have questions about the hierarchy of scala.collection.Traversable. Look at the following declarations: package scala.collection trait Traversable[+A] extends TraversableLike[A, Traversable[A]] with GenericTraversableTemplate[A, Traversable] trait TraversableLike[+A, +Repr] extends HasNewBuilder[A, Repr] with TraversableOnce[A] package scala.collection.generic trait HasNewBuilder[+A, +Repr] trait GenericTraversableTemplate[+A, +CC[X] <: Traversable[X]] extends HasNewBuilder[A, CC[A] @uncheckedVariance] Question: Why does Traversable extend GenericTraversableTemplate with type parameters [A, Traversable] - why not [A, Traversable[A]]? I tried some experimenting with a small program with the same structure and got a strange error message when I tried to change it to Traversable[A]: error: Traversable[A] takes no type parameters, expected: one I guess that the use of the @uncheckedVariance annotation in GenericTraversableTemplate also has to do with this? (That seems like a kind of potentially unsafe hack to force things to work...). Question: When you look at the hierarchy, you see that Traversable inherits HasNewBuilder twice (once via TraversableLike and once via GenericTraversableTemplate), but with slightly different type parameters. How does this work exactly? Why don't the different type parameters cause an error?

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  • How can I use a custom configured RememberMeAuthenticationFilter in spring security?

    - by Sebastian
    I want to use a slightly customized rememberme functionality with spring security (3.1.0). I declare the rememberme tag like this: <security:remember-me key="JNJRMBM" user-service-ref="gymUserDetailService" /> As I have my own rememberme service I need to inject that into the RememberMeAuthenticationFilter which I define like this: <bean id="rememberMeFilter" class="org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter"> <property name="rememberMeServices" ref="gymRememberMeService"/> <property name="authenticationManager" ref="authenticationManager" /> </bean> I have spring security integrated in a standard way in my web.xml: <filter-name>springSecurityFilterChain</filter-name> <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class> Everything works fine, except that the RememberMeAuthenticationFilter uses the standard RememberMeService, so I think that my defined RememberMeAuthenticationFilter is not being used. How can I make sure that my definition of the filter is being used? Do I need to create a custom filterchain? And if so, how can I see my current "implicit" filterchain and make sure I use the same one except my RememberMeAuthenticationFilter instead of the default one? Thanks for any advice and/or pointers!

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