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  • 2D SAT How to find collision center or point or area?

    - by Felipe Cypriano
    I've just implemented collision detection using SAT and this article as reference to my implementation. The detection is working as expected but I need to know where both rectangles are colliding. I need to find the center of the intersection, the black point on the image above. I've found some articles about this but they all involve avoiding the overlap or some kind of velocity, I don't need this. I just need to put a image on top of it. Like two cars crashed so I put an image on top of the collision. Any ideas? ## Update The information I've about the rectangles are the four points that represents them, the upper right, upper left, lower right and lower left coordinates. I'm trying to find an algorithm that can give me the intersection of these points.

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  • Yippy &ndash; the F# MVVM Pattern

    - by MarkPearl
    I did a recent post on implementing WPF with F#. Today I would like to expand on this posting to give a simple implementation of the MVVM pattern in F#. A good read about this topic can also be found on Dean Chalk’s blog although my example of the pattern is possibly simpler. With the MVVM pattern one typically has 3 segments, the view, viewmodel and model. With the beauty of WPF binding one is able to link the state based viewmodel to the view. In my implementation I have kept the same principles. I have a view (MainView.xaml), and and a ViewModel (MainViewModel.fs).     What I would really like to illustrate in this posting is the binding between the View and the ViewModel so I am going to jump to that… In Program.fs I have the following code… module Program open System open System.Windows open System.Windows.Controls open System.Windows.Markup open myViewModels // Create the View and bind it to the View Model let myView = Application.LoadComponent(new System.Uri("/FSharpWPF;component/MainView.xaml", System.UriKind.Relative)) :?> Window myView.DataContext <- new MainViewModel() :> obj // Application Entry point [<STAThread>] [<EntryPoint>] let main(_) = (new Application()).Run(myView) You can see that I have simply created the view (myView) and then created an instance of my viewmodel (MainViewModel) and then bound it to the data context with the code… myView.DataContext <- new MainViewModel() :> obj If I have a look at my viewmodel (MainViewModel) it looks like this… module myViewModels open System open System.Windows open System.Windows.Input open System.ComponentModel open ViewModelBase type MainViewModel() = // private variables let mutable _title = "Bound Data to Textbox" // public properties member x.Title with get() = _title and set(v) = _title <- v // public commands member x.MyCommand = new FuncCommand ( (fun d -> true), (fun e -> x.ShowMessage) ) // public methods member public x.ShowMessage = let msg = MessageBox.Show(x.Title) () I have exposed a few things, namely a property called Title that is mutable, a command and a method called ShowMessage that simply pops up a message box when called. If I then look at my view which I have created in xaml (MainView.xaml) it looks as follows… <Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="F# WPF MVVM" Height="350" Width="525"> <Grid> <Grid.RowDefinitions> <RowDefinition Height="Auto"/> <RowDefinition Height="Auto"/> <RowDefinition Height="*"/> </Grid.RowDefinitions> <TextBox Text="{Binding Path=Title, Mode=TwoWay}" Grid.Row="0"/> <Button Command="{Binding MyCommand}" Grid.Row="1"> <TextBlock Text="Click Me"/> </Button> </Grid> </Window>   It is also very simple. It has a button that’s command is bound to the MyCommand and a textbox that has its text bound to the Title property. One other module that I have created is my ViewModelBase. Right now it is used to store my commanding function but I would look to expand on it at a later stage to implement other commonly used functions… module ViewModelBase open System open System.Windows open System.Windows.Input open System.ComponentModel type FuncCommand (canExec:(obj -> bool),doExec:(obj -> unit)) = let cecEvent = new DelegateEvent<EventHandler>() interface ICommand with [<CLIEvent>] member x.CanExecuteChanged = cecEvent.Publish member x.CanExecute arg = canExec(arg) member x.Execute arg = doExec(arg) Put this all together and you have a basic project that implements the MVVM pattern in F#. For me this is quite exciting as it turned out to be a lot simpler to do than I originally thought possible. Also because I have my view in XAML I can use the XAML designer to design forms in F# which I believe is a much cleaner way to go rather than implementing it all in code. Finally if I look at my viewmodel code, it is actually quite clean and compact…

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  • Transformation matrix that maps a window

    - by gbhall
    I'm currently learning OpenGL at uni, and they give us questions to help us learn (these are not worth anything), however I'm stuck on this one question and would have to travel over an hour and a half to uni for an answer. How do I do this question? Please include as many steps as you can, I want to be able to follow exactly how to do this. Find the transformation that maps a window whose lower left corner is at (1,1) and upper right corner is at (3,5) onto: The entire device screen whose dimension is (600, 500) A viewport that has lower left corner at (100,100) and upper right corner at (400,400) Edit: Damn sorry I should have added I am meant to find the matrix, so no code.

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  • Hardware from Oracle, Pricing for Education (HOPE) Program: New version now available!

    - by Cinzia Mascanzoni
    With HOPE Version 5, Oracle offers education institutions even more unmatched savings on its award-winning systems products making it more affordable for educational institutions to create scalable, high-performing, and low TCO teaching and learning environments. With special discounts for you, on selected Sun products from Oracle, the net result is that you can assist your Resellers in reducing the impact on their customers' budget in two ways: • Lower the total cost for technology acquisition of systems and hardware, for the end user • Reduce the environmental impact of the educational institutions served by your Resellers, by running and maintaining a lower cost, more efficient infrastructure Start today to take advantage of the new release of this exciting program from Oracle. Check the EMEA VAD Resource Center for a description of the products and discounts offered to you and to find links to more detailed information about these Sun products.

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  • Faulty memtest result

    - by dhojgaard
    I've been a bit suspicious about my RAM lately. They seem not work like i expect them to. For instance i run a lot of Virtual Test Environments in VMware Workstation and lately Ubuntu starts to lag just running 4 virtual machines each dedicated 512 MB. BTW im having 6GB memory on my laptop. This did not use to be a problem for me on my last laptop that even had a lot lower CPU resources. So i was led to try a memtest after reading some websites about RAM testing. So i did a memtest overnight but when i woke up this morning i was just looping and i could not Exit or do anything. It was just looping the number of errors besides test 7 which you can see in the lower right part of the screenshot. Can anyone interpret this screenshot for me? Do i have a faulty set of RAMs?

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  • Do we still need to avoid using frame/iframe for good SEO?

    - by Marco Demaio
    I thought frame and iframe are something bad for SEO. Today I was doing some search and searching for "numismatica" in Google.it and the 3rd site is www.lemonete.com (ranks high also in Google.com). It's all made with frames. A competitor site (www.nummus.com) that is all done with no frames ranks much lower when searching for the same word: "numismatica" So can we use frame, don't they hit SEO ranking anymore? Any explanation (possibly simple) would be appreciated also about the fact the 2nd site ranks much lower. :) UPDATE: thanks for all the replies , I noticed now I wrote down the wrong url, it was not lemonete.it (which is just a spam site) but lemonete.com.

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  • Checking whether a specific key was pressed in enchantJS

    - by MxyL
    I am using enchantJS and would like to use the letters and numbers as well as numpad on a keyboard to do different things (eg: hotkeys). From this page http://users.csc.calpoly.edu/~foaad/enchant/guide/playerInput.html By default, enchant.js provides input listeners for six buttons: UP, DOWN, LEFT, RIGHT, A, and B. By default, the directions are bound to the arrow keys. Any of the six buttons may also be bound to any key with an ASCII value. We’ll address that later. So enchant provides the ability to bind keys to different input such as up, down, left, right...but how can I simply check whether the D or X key was pressed, and if so, perform certain actions based on that event?

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  • Are the technologies used in an application part of the architecture, or do they represent implementation/detailed design details?

    - by m3th0dman
    When designing and writing documentation for a project an architecture needs to be clearly defined: what are the high-level modules of the system, what are their responsibilities, how do they communicate with each other, what protocols are used etc. But in this list, should the concrete technologies be specified or this is actually an implementation detail and need to be specified at a lower level? For example, consider a distributed application that has two modules which communicate asynchronously via AMQP protocol, mediated by a message broker. The fact that these modules use the Spring AMQP library for sending and receiving messages is a fact that needs to be specified in the architecture or is a lower-level detailed design/implementation detail?

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  • How to Find Your Lost Android Phone, Even if You Never Set Up a Tracking App

    - by Chris Hoffman
    Android doesn’t come with a “find my Android” feature, so there’s no official way to track your phone if you lose it. You should prepare your phone for loss by setting up such a tracking app — but what if you didn’t? Your first instinct may be to download Lookout’s Plan B, which has been the go-to app for this purpose. However, Plan B only runs on Android 2.3 Gingerbread and lower, so modern Android phones will require a new solution. If you are still running 2.3 or lower, you should definitely check it out, but everybody else can keep reading.    

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  • creating a list of consecutive integers in c#

    - by Alex Bransky
    If there's already a way to get a List<int> of consecutive integers without a loop in C#, I don't know what it is, so I created a method for it.         public static List<int> GetIntegerListFromRange(int start, int end) {             if (end < start) {                 throw new ArgumentException("Faulty parameter(s) passed: lower bound cannot be less than upper bound.");                }             List<int> returnList = new List<int>(end - start + 1);             for(int i = start; i <= end; i++) {                 returnList.Add(i);             }             return returnList;         }

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  • Handling cameras in a large scale game engine

    - by Hannesh
    What is the correct, or most elegant, way to manage cameras in large game engines? Or should I ask, how does everybody else do it? The methods I can think of are: Binding cameras straight to the engine; if someone needs to render something, they bind their own camera to the graphics engine which is in use until another camera is bound. A camera stack; a small task can push its own camera onto the stack, and pop it off at the end to return to the "main" camera. Attaching a camera to a shader; Every shader has exactly one camera bound to it, and when the shader is used, that camera is set by the engine when the shader is in use. This allows me to implement a bunch of optimizations on the engine side. Are there other ways to do it?

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  • Combobox binding with different types

    - by George Evjen
    Binding to comboboxes in Silverlight has been an adventure the past couple of days. In our framework at ArchitectNow we use LookupGroups and LookupValues. In our database we would have a LookupGroup of NBA Teams for example. The group would be called NBATeams, we get the LookupGroupID and then get the values from the LookupValues table. So we would end up with a list of all 30+ teams. Our lookup values entity has a display text(string), value(string), IsActive and some other fields. With our applications we load all this information into the system when the user is logging in or right after they login. So in cache we have a list of groups and values that we can get at whenever we want to. We get this information in our framework simply by creating an observable collection of type LookupValue. To get a list of these values into our property all we have to do is. var NBATeams = AppContext.Current.LookupSerivce.GetLookupValues(“NBATeams”); Our combobox then is bound like this. (We use telerik components in most if not all our projects) <telerik:RadComboBox ItemsSource="{Binding NBATeams}”></telerik:RadComboBox> This should give you a list in your combobox. We also set up another property in our ViewModel that is a just single object of NBATeams  - “SelectedNBATeam” Our selectedItem in our combobox would look like, we would set this to a two way binding since we are sending data back. SelectedItem={Binding SelectedNBATeam, mode=TwoWay}” This is all pretty straight forward and we use this pattern throughout all our applications. What do you do though when you have a combobox in a ItemsControl or ListBox? Here we have a list of NBA Teams that are a string that are being brought back from the database. We cant have the selected item be our LookupValue because the data is a string and its being bound in an ItemsControl. In the example above we would just have the combobox in a form. Here though we have it in a ItemsControl, where there is no selected item from the initial ItemsSource. In order to get the selected item to be displayed in the combobox you have to convert the LookupValue to a string. Then instead of using SelectedItem in the combobox use SelectedValue. To convert the LookupValue we do this. Create an observable collection of strings public ObservableCollection<string> NBATeams { get; set;} Then convert your lookups to strings var NBATeams = new ObservableCollection<string>(AppContext.Current.LookupService.GetLookupValues(“NBATeams”).Select(x => x.DisplayText)); This will give us a list of strings and our selected value should be bound to the NBATeams property in our ItemsSource in our ItemsControl. SelectedValue={Binding NBATeam, mode=TwoWay}”

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  • TDD, new tests while old ones not implemented yet

    - by liori
    I am experimenting with test-driven development, and I found that I often come to a following situation: I write tests for some functionality X. Those tests fail. While trying to implement X, I see that I need to implement some feature Y in a lower layer of my code. So... I write tests for Y. Now both tests for X and Y fail. Once I had 4 features in different layers of code being worked on at the same time, and I was losing my focus on what I am actually doing (too many tests failing at the same time). I think I could solve this by putting more effort into planning my tasks even before I start writing tests. But in some cases I didn't know that I will need to go deeper, because e.g. I didn't know the API of lower layer very well. What should I do in such cases? Does TDD have any recommendations?

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  • Clarify the Single Responsibility Principle.

    - by dsimcha
    The Single Responsibility Principle states that a class should do one and only one thing. Some cases are pretty clear cut. Others, though, are difficult because what looks like "one thing" when viewed at a given level of abstraction may be multiple things when viewed at a lower level. I also fear that if the Single Responsibility Principle is honored at the lower levels, excessively decoupled, verbose ravioli code, where more lines are spent creating tiny classes for everything and plumbing information around than actually solving the problem at hand, can result. How would you describe what "one thing" means? What are some concrete signs that a class really does more than "one thing"?

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  • How can I limit CD drive speed while on the live CD to avoid drive noise?

    - by iugamarian
    I sometimes disconect my harddisks for the weeks while only using the internet and I use the Ubuntu Live CD. But every time it needs something while in live desktop it accelerates and makes a lot of noise, also the acceleration takes too long. I want lower drive speed than acceleration lags, because acceleration lags stop me completly exactly when I need something. How can I lower the CD drive speed, say to maximum 16x, without restarting? I can't restart because I only use the CD drive, no harddisks, no flash disks, no network disks. Edit: No USB drives. Setcd does not work for the live session.

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  • Ubuntu 12.04 wallpaper problem when using two monitors

    - by jiomsa
    I am using two monitors, the main resolution is 1920x1080 and the secondary is 1440x900. Everything seems to work fine (with default drivers, fglrx crashes bad), besides windows opening in the wrong monitor (even when the main is set correctly), but now what I am trying to fix is the wallpaper problem, here's an image to explain it easier: http://i.imgur.com/msLRR.jpg It also happens with gradients. The secondary monitor is physically aligned like in the image, lower than the other, the wallpaper on the main screen seems to keep the size of the lower resolution, and then it start at the correct resolution the last part at right. Any way to fix this? I am using Ubuntu 12.04 with Gnome-Shell 3.4.1, the vga is a Radeon HD 6950 UPDATE I went to gnome-tweak-tool and disabled "Have file manager handle the desktop", now it looks ok on both monitors, but I can't have icons on my desktop, so I am still interested in solving it. UPDATE2 Disabling "Have file manager handle the desktop", in gnome-tweak-tool and then re-enabling it seems to work, but has to be done every time you turn on the PC.

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  • Why can't Java/C# implement RAII?

    - by mike30
    Question: Why can't Java/C# implement RAII? Clarification: I am aware the garbage collector is not deterministic. So with the current language features it is not possible for an object's Dispose() method to be called automatically on scope exit. But could such a deterministic feature be added? My understanding: I feel an implementation of RAII must satisfy two requirements: 1. The lifetime of a resource must be bound to a scope. 2. Implicit. The freeing of the resource must happen without an explicit statement by the programmer. Analogous to a garbage collector freeing memory without an explicit statement. The "implicitness" only needs to occur at point of use of the class. The class library creator must of course explicitly implement a destructor or Dispose() method. Java/C# satisfy point 1. In C# a resource implementing IDisposable can be bound to a "using" scope: void test() { using(Resource r = new Resource()) { r.foo(); }//resource released on scope exit } This does not satisfy point 2. The programmer must explicitly tie the object to a special "using" scope. Programmers can (and do) forget to explicitly tie the resource to a scope, creating a leak. In fact the "using" blocks are converted to try-finally-dispose() code by the compiler. It has the same explicit nature of the try-finally-dispose() pattern. Without an implicit release, the hook to a scope is syntactic sugar. void test() { //Programmer forgot (or was not aware of the need) to explicitly //bind Resource to a scope. Resource r = new Resource(); r.foo(); }//resource leaked!!! I think it is worth creating a language feature in Java/C# allowing special objects that are hooked to the stack via a smart-pointer. The feature would allow you to flag a class as scope-bound, so that it always is created with a hook to the stack. There could be a options for different for different types of smart pointers. class Resource - ScopeBound { /* class details */ void Dispose() { //free resource } } void test() { //class Resource was flagged as ScopeBound so the tie to the stack is implicit. Resource r = new Resource(); //r is a smart-pointer r.foo(); }//resource released on scope exit. I think implicitness is "worth it". Just as the implicitness of garbage collection is "worth it". Explicit using blocks are refreshing on the eyes, but offer no semantic advantage over try-finally-dispose(). Is it impractical to implement such a feature into the Java/C# languages? Could it be introduced without breaking old code?

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  • SQL Server Memory Manager Changes in Denali

    - by SQLOS Team
    The next version of SQL Server will contain significant changes to the memory manager component.  The memory manager component has been rewritten for Denali.  In the previous versions of SQL Server there were two distinct memory managers.  There was one memory manager which handled allocation sizes of 8k or less and another for greater than 8k.  For Denali there will be one memory manager for all allocation sizes.   The majority of the changes will be transparent to the end user.  However, some changes will be visible to the user.  These are listed below: ·         The ‘max server memory’ configuration option has new lower limits.  Specifically, 32-bit versions of SQL Server will have a lower limit of 64 MB.  The 64-bit versions will have a lower limit of 128 MB. ·         All memory allocations by SQL Server components will observe the ‘max server memory’ configuration option.  In previous SQL versions only the 8k allocations were limited the ‘max server memory’ configuration option.  Allocations larger than 8k weren’t constrained. ·         DMVs which refer to memory manager internals have been modified.  This includes adding or removing columns and changing column names. ·         The memory manager configuration messages in the error log have minor changes. ·         DBCC memorystatus output has been changed. ·         Address Windowing Extensions (AWE) has been deprecated.   In the next blog post I will discuss the changes to the memory manager DMVs in greater detail.  In future blog posts I will discuss the other changes in greater detail.  

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  • Enable button based on TextBox value (WPF)

    - by zendar
    This is MVVM application. There is a window and related view model class. There is TextBox, Button and ListBox on form. Button is bound to DelegateCommand that has CanExecute function. Idea is that user enters some data in text box, presses button and data is appended to list box. I would like to enable command (and button) when user enters correct data in TextBox. Things work like this now: CanExecute() method contains code that checks if data in property bound to text box is correct. Text box is bound to property in view model UpdateSourceTrigger is set to PropertyChanged and property in view model is updated after each key user presses. Problem is that CanExecute() does not fire when user enters data in text box. It doesn't fire even when text box lose focus. How could I make this work? Edit: Re Yanko's comment: Delegate command is implemented in MVVM toolkit template and when you create new MVVM project, there is Delegate command in solution. As much as I saw in Prism videos this should be the same class (or at least very similar). Here is XAML snippet: ... <UserControl.Resources> <views:CommandReference x:Key="AddObjectCommandReference" Command="{Binding AddObjectCommand}" /> </UserControl.Resources> ... <TextBox Text="{Binding ObjectName, UpdateSourceTrigger=PropertyChanged}"> </TextBox> <Button Command="{StaticResource AddObjectCommandReference}">Add</Button> ... View model: // Property bound to textbox public string ObjectName { get { return objectName; } set { objectName = value; OnPropertyChanged("ObjectName"); } } // Command bound to button public ICommand AddObjectCommand { get { if (addObjectCommand == null) { addObjectCommand = new DelegateCommand(AddObject, CanAddObject); } return addObjectCommand; } } private void AddObject() { if (ObjectName == null || ObjectName.Length == 0) return; objectNames.AddSourceFile(ObjectName); OnPropertyChanged("ObjectNames"); // refresh listbox } private bool CanAddObject() { return ObjectName != null && ObjectName.Length > 0; } As I wrote in the first part of question, following things work: property setter for ObjectName is triggered on every keypress in textbox if I put return true; in CanAddObject(), command is active (button to) It looks to me that binding is correct. Thing that I don't know is how to make CanExecute() fire in setter of ObjectName property from above code. Re Ben's and Abe's answers: CanExecuteChanged() is event handler and compiler complains: The event 'System.Windows.Input.ICommand.CanExecuteChanged' can only appear on the left hand side of += or -= there are only two more members of ICommand: Execute() and CanExecute() Do you have some example that shows how can I make command call CanExecute(). I found command manager helper class in DelegateCommand.cs and I'll look into it, maybe there is some mechanism that could help. Anyway, idea that in order to activate command based on user input, one needs to "nudge" command object in property setter code looks clumsy. It will introduce dependencies and one of big points of MVVM is reducing them. Is it possible to solve this problem by using dependency properties?

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