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• How employable am I as a programmer?

  - by dsimcha

  I'm currently a Ph.D. student in Biomedical Engineering with a concentration in computational biology and am starting to think about what I want to do after graduate school. I feel like I've accumulated a lot of programming skills while in grad school, but taken a very non-traditional path to learning all this stuff. I'm wondering whether I would have an easy time getting hired as a programmer and could fall back on that if I can't find a good job directly in my field, and if so whether I would qualify for a more prestigious position than "code monkey". Things I Have Going For Me Approximately 4 years of experience programming as part of my research. I believe I have a solid enough grasp of the fundamentals that I could pick up new languages and technologies pretty fast, and could demonstrate this in an interview. Good math and statistics skills. An extensive portfolio of open source work (and the knowledge that working on these projects implies): I wrote a statistics library in D, mostly from scratch. I wrote a parallelism library (parallel map, reduce, foreach, task parallelism, pipelining, etc.) that is currently in review for adoption by the D standard library. I wrote a 2D plotting library for D against the GTK Cairo backend. I currently use it for most of the figures I make for my research. I've contributed several major performance optimizations to the D garbage collector. (Most of these were low-hanging fruit, but it still shows my knowledge of low-level issues like memory management, pointers and bit twiddling.) I've contributed lots of miscellaneous bug fixes to the D standard library and could show the change logs to prove it. (This demonstrates my ability read other people's code.) Things I Have Going Against Me Most of my programming experience is in D and Python. I have very little to virtually no experience in the more established, "enterprise-y" languages like Java, C# and C++, though I have learned a decent amount about these languages from small, one-off projects and discussions about language design in the D community. In general I have absolutely no knowledge of "enterprise-y" technlogies. I've never used a framework before, possibly because most reusable code for scientific work and for D tends to call itself a "library" instead. I have virtually no formal computer science/software engineering training. Almost all of my knowledge comes from talking to programming geek friends, reading blogs, forums, StackOverflow, etc. I have zero professional experience with the official title of "developer", "software engineer", or something similar.

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• PL/SQL Practices - "On Emulating FINALLY"

  Code PL/SQL to function like the Java FINALLY section.

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• How essential is it to make a service layer?

  - by BornToCode

  I started building an app in 3 layers (DAL, BL, UI) [it mainly handles CRM, some sales reports and inventory]. A colleague told me that I must move to service layer pattern, that developers came to service pattern from their experience and it is the better approach to design most applications. He said it would be much easier to maintain the application in the future that way. Personally, I get the feeling that it's just making things more complex and I couldn't see much of a benefit from it that would justify that. This app does have an additional small partial ui that uses some (but only few) of the desktop application functions so I did find myself duplicating some code (but not much). Just because of some code duplication I wouldn't convert it to be service oriented, but he said I should use it anyway because in general it's a very good architecture, why programmers are so in love with services?? I tried to google on it but I'm still confused and can't decide what to do.

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• .NET Compiler Platform (Roslyn) , its relevance to developer community and its performance? [on hold]

  - by jerriclynsjohn

  I'm just starting out with a Code-Quality-plugin development for my organization based on the recently released .NET Compiler Platform APIs (Roslyn APIs). I would like to know what are the most relevant possible ways that it could be used by the developer community apart from the usual IDE experience as answered in other questions. I was wondering the implications of opening up a compiler to general public and never came across anything "breakthrough", that could possibly add up to the value of IDE experiences. Is there any performance bottleneck for its implementation since the compiler itself is managed code?

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• Exporting an animated FBX to XNA? (in 3DS Max)

  - by Itamar Marom

  I'm now working on an XNA 3D game, and I want to add animated models in it. I came across this example. I see there is one FBX file and a few texture files in the content project, and that in the code you can choose which "take" to play. In this code it is "Take_001". Please tell me: When I create and animate my own 3D model in 3DS Max (2012, since I was told it's only possible in this version), how can I define those takes? plus, are any configurations need to be made when exporting FBX from 3DS Max to XNA? Thank you.

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• Elegant ways to handle if(if else) else

  - by Benjol

  This is a minor niggle, but every time I have to code something like this, the repetition bothers me, but I'm not sure that any of the solutions aren't worse. if(FileExists(file)) { contents = OpenFile(file); // <-- prevents inclusion in if if(SomeTest(contents)) { DoSomething(contents); } else { DefaultAction(); } } else { DefaultAction(); } Is there a name for this kind of logic? Am I a tad too OCD? I'm open to evil code suggestions, if only for curiosity's sake...

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• Creating SparseImages for Pivot

  - by John Conwell

  Learning how to programmatically make collections for Microsoft Live Labs Pivot has been a pretty interesting ride. There are very few examples out there, and the folks at MS Live Labs are often slow on any feedback.  But that is what Reflector is for, right? Well, I was creating these InfoCard images (similar to the Car images in the "New Cars" sample collection that that MS created for Pivot), and wanted to put a Tag Cloud into the info card.  The problem was the size of the tag cloud might vary in order for all the tags to fit into the tag cloud (often times being bigger than the info card itself).  This was because the varying word lengths and calculated font sizes. So, to fix this, I made the tag cloud its own separate image from the info card.  Then, I would create a sparse image out of the two images, where the tag cloud fit into a small section of the info card.  This would allow the user to see the info card, but then zoom into the tag cloud and see all the tags at a normal resolution.  Kind'a cool. But...I couldn't find one code example (not one!) of how to create a sparse image.  There is one page on the SeaDragon site (http://www.seadragon.com/developer/creating-content/deep-zoom-tools/) that gives over the API for creating images and collections, and it sparsely goes over how to create a sparse image, but unless you are familiar with the API already, the documentation doesn't help very much. The key is the Image.ViewportWidth and Image.ViewportOrigin properties of the image that is getting super imposed on the main image.  I'll walk through the code below.  I've setup a couple Point structs to represent the parent and sub image sizes, as well as where on the parent I want to position the sub image.  Next, create the parent image.  This is pretty straight forward.  Then I create the sub image.  Then I calculate several ratios; the height to width ratio of the sub image, the width ratio of the sub image to the parent image, the height ratio of the sub image to the parent image, then the X and Y coordinates on the parent image where I want the sub image to be placed represented as a ratio of the position to the parent image size. After all these ratios have been calculated, I use them to calculate the Image.ViewportWidth and Image.ViewportOrigin values, then pass the image objects into the SparseImageCreator and call Create. The key thing that was really missing from the API documentation page is that when setting up your sub images, everything is expressed in a ratio in relation to the main parent image.  If I had known this, it would have saved me a lot of trial and error time.  And how did I figure this out?  Reflector of course!  There is a tool called Deep Zoom Composer that came from MS Live Labs which can create a sparse image.  I just dug around the tool's code until I found the method that create sparse images.  But seriously...look at the API documentation from the SeaDragon size and look at the code below and tell me if the documentation would have helped you at all.  I don't think so!   public static void WriteDeepZoomSparseImage(string mainImagePath, string subImagePath, string destination) {     Point parentImageSize = new Point(720, 420);     Point subImageSize = new Point(490, 310);     Point subImageLocation = new Point(196, 17);     List<Image> images = new List<Image>();     //create main image     Image mainImage = new Image(mainImagePath);     mainImage.Size = parentImageSize;     images.Add(mainImage);     //create sub image     Image subImage = new Image(subImagePath);     double hwRatio = subImageSize.X/subImageSize.Y;            // height width ratio of the tag cloud     double nodeWidth = subImageSize.X/parentImageSize.X;        // sub image width to parent image width ratio     double nodeHeight = subImageSize.Y / parentImageSize.Y;    // sub image height to parent image height ratio     double nodeX = subImageLocation.X/parentImageSize.X;       //x cordinate position on parent / width of parent     double nodeY = subImageLocation.Y / parentImageSize.Y;     //y cordinate position on parent / height of parent     subImage.ViewportWidth = (nodeWidth < double.Epsilon) ? 1.0 : (1.0 / nodeWidth);     subImage.ViewportOrigin = new Point(         (nodeWidth < double.Epsilon) ? -1.0 : (-nodeX / nodeWidth),         (nodeHeight < double.Epsilon) ? -1.0 : ((-nodeY / nodeHeight) / hwRatio));     images.Add(subImage);     //create sparse image     SparseImageCreator creator = new SparseImageCreator();     creator.Create(images, destination); }

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• Install Samba 3.0.24 on Ubuntu Server 10.04 from Source

  - by Nilpo

  Has anyone had any luck compiling and installing Samba 3.0.24 on Ubuntu 10.04? I'm trying to set up realtime virus scanning on Samba shares (ClamAV) using the legacy version of Samba as it is the latest release supported by samba-vscan-0.3.6b. I'm no expert at this but I think I have all of the dependencies covered and I'm following the documentation with the source code but I'm getting errors as if there is a problem with the source code. I downloaded the source directly from http://ftp.samba.org/pub/samba/stable/samba-3.0.24.tar.gz After running ./configure and make, I get the following error. Compiling client/mount.cifs.c client/mount.cifs.c: In function ‘main’: client/mount.cifs.c:1068: error: ‘PATH_MAX’ undeclared (first use in this function) client/mount.cifs.c:1068: error: (Each undeclared identifier is reported only once client/mount.cifs.c:1068: error: for each function it appears in.) make: *** [client/mount.cifs.o] Error 1 You can view the full output log here. Can anyone help me get this installed or suggest another means of implementing realtime virus scanning on Samba shares?

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• 2D game - Missile shooting problem on Android

  - by Niksa

  Hello, I have to make a tank that sits still but moves his turret and shoots missiles. As this is my first Android application ever and I haven't done any game development either, I've come across a few problems... Now, I did the tank and the moving turret once I read the Android tutorial for the LunarLander sample code. So this code is based on the LunarLander code. But I'm having trouble doing the missile firing then SPACE button is being pressed. private void doDraw(Canvas canvas) { canvas.drawBitmap(backgroundImage, 0, 0, null); // draws the tank canvas.drawBitmap(tank, x_tank, y_tank, new Paint()); // draws and rotates the tank turret canvas.rotate((float) mHeading, (float) x_turret + mTurretWidth, y_turret); canvas.drawBitmap(turret, x_turret, y_turret, new Paint()); // draws the grenade that is a regular circle from ShapeDrawable class bullet.setBounds(x_bullet, y_bullet, x_bullet + width, y_bullet + height); bullet.draw(canvas); } UPDATE GAME method private void updateGame() throws InterruptedException { long now = System.currentTimeMillis(); if (mLastTime > now) return; double elapsed = (now - mLastTime) / 1000.0; mLastTime = now; // dUP and dDown, rotates the turret from 0 to 75 degrees. if (dUp) mHeading += 1 * (PHYS_SLEW_SEC * elapsed); if (mHeading >= 75) mHeading = 75; if (dDown) mHeading += (-1) * (PHYS_SLEW_SEC * elapsed); if (mHeading < 0) mHeading = 0; if (dSpace){ // missile Logic, a straight trajectorie for now x_bullet -= 1; y_bullet -= 1; //doesn't work, has to be updated every pixel or what? } boolean doKeyDown(int keyCode, KeyEvent msg) { boolean handled = false; synchronized (mSurfaceHolder) { if (keyCode == KeyEvent.KEYCODE_SPACE){ dSpace = true; handled = true; } if (keyCode == KeyEvent.KEYCODE_DPAD_UP){ dUp = true; handled = true; } if (keyCode == KeyEvent.KEYCODE_DPAD_DOWN){ dDown = true; handled = true; } return handled; } } } a method run that runs the game... public void run() { while (mRun) { Canvas c = null; try { c = mSurfaceHolder.lockCanvas(null); synchronized (mSurfaceHolder) { if (mMode == STATE_RUNNING) updateGame(); doDraw(c); } } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { // do this in a finally so that if an exception is thrown // during the above, we don't leave the Surface in an // inconsistent state if (c != null) { mSurfaceHolder.unlockCanvasAndPost(c); } } } } So the question would be, how do I make that the bullet is fired on a single SPACE key press from the turret to the end of the screen? Could you help me out here, I seem to be in the dark here... Thanks, Niksa

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• Why would I learn C++11, having known C and C++?

  - by Shahbaz

  I am a programmer in C and C++, although I don't stick to either language and write a mixture of the two. Sometimes having code in classes, possibly with operator overloading, or templates and the oh so great STL is obviously a better way. Sometimes use of a simple C function pointer is much much more readable and clear. So I find beauty and practicality in both languages. I don't want to get into the discussion of "If you mix them and compile with a C++ compiler, it's not a mix anymore, it's all C++" I think we all understand what I mean by mixing them. Also, I don't want to talk about C vs C++, this question is all about C++11. C++11 introduces what I think are significant changes to how C++ works, but it has introduced many special cases that change how different features behave in different circumstances, placing restrictions on multiple inheritance, adding lambda functions, etc. I know that at some point in the future, when you say C++ everyone would assume C++11. Much like when you say C nowadays, you most probably mean C99. That makes me consider learning C++11. After all, if I want to continue writing code in C++, I may at some point need to start using those features simply because my colleagues have. Take C for example. After so many years, there are still many people learning and writing code in C. Why? Because the language is good. What good means is that, it follows many of the rules to create a good programming language. So besides being powerful (which easy or hard, almost all programming languages are), C is regular and has few exceptions, if any. C++11 however, I don't think so. I'm not sure that the changes introduced in C++11 are making the language better. So the question is: Why would I learn C++11? Update: My original question in short was: "I like C++, but the new C++11 doesn't look good because of this and this and this. However, deep down something tells me I need to learn it. So, I asked this question here so that someone would help convince me to learn it." However, the zealous people here can't tolerate pointing out a flaw in their language and were not at all constructive in this manner. After the moderator edited the question, it became more like a "So, how about this new C++11?" which was not at all my question. Therefore, in a day or too I am going to delete this question if no one comes up with an actual convincing argument. P.S. If you are interested in knowing what flaws I was talking about, you can edit my question and see the previous edits.

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• How should a new programmers behave at their first job? [on hold]

  - by Dimension

  What are programmers expected to know at their first job and how old will they typically be? I'm not going to school so I'm not around other programmers, therefore I have no idea what kind of programmers they are when they first get hired. I just want to get an idea what the median programmer's knowledge looks like. Will they already have had experience with version control? Are they writing good maintainable code? And what are they expected to do do? I'm programming my own software at home and because of the complexities of it and how new I am to programming I'm sometimes throwing all the code out and starting again with a better design. Aren't new programmers going to write terribly structured software for their employer, or is someone else going to be making the decisions on how everything is laid out?

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• "Hello World" in C++ AMP

  - by Daniel Moth

  Some say that the equivalent of "hello world" code in the data parallel world is matrix multiplication :) Below is the before C++ AMP and after C++ AMP code. For more on what it all means, watch the recording of my C++ AMP introduction (the example below is part of the session). void MatrixMultiply(vector<float>& vC, const vector<float>& vA, const vector<float>& vB, int M, int N, int W ) { for (int y = 0; y < M; y++) { for (int x = 0; x < N; x++) { float sum = 0; for(int i = 0; i < W; i++) { sum += vA[y * W + i] * vB[i * N + x]; } vC[y * N + x] = sum; } } } Change the function to use C++ AMP and hence offload the computation to the GPU, and now the calling code (which I am not showing) needs no changes and the overall operation gives you really nice speed up for large datasets…  #include <amp.h> using namespace concurrency; void MatrixMultiply(vector<float>& vC, const vector<float>& vA, const vector<float>& vB, int M, int N, int W ) { array_view<const float,2> a(M, W, vA); array_view<const float,2> b(W, N, vB); array_view<writeonly<float>,2> c(M, N, vC); parallel_for_each( c.grid, [=](index<2> idx) mutable restrict(direct3d) { float sum = 0; for(int i = 0; i < a.x; i++) { sum += a(idx.y, i) * b(i, idx.x); } c[idx] = sum; } ); } Again, you can understand the elements above, by using my C++ AMP presentation slides and recording… Stay tuned for more… Comments about this post welcome at the original blog.

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• How to get distinct values from the List&lt;T&gt; with LINQ

  - by Vincent Maverick Durano

  Recently I was working with data from a generic List<T> and one of my objectives is to get the distinct values that is found in the List. Consider that we have this simple class that holds the following properties: public class Product { public string Make { get; set; } public string Model { get; set; } }   Now in the page code behind we will create a list of product by doing the following: private List<Product> GetProducts() { List<Product> products = new List<Product>(); Product p = new Product(); p.Make = "Samsung"; p.Model = "Galaxy S 1"; products.Add(p); p = new Product(); p.Make = "Samsung"; p.Model = "Galaxy S 2"; products.Add(p); p = new Product(); p.Make = "Samsung"; p.Model = "Galaxy Note"; products.Add(p); p = new Product(); p.Make = "Apple"; p.Model = "iPhone 4"; products.Add(p); p = new Product(); p.Make = "Apple"; p.Model = "iPhone 4s"; products.Add(p); p = new Product(); p.Make = "HTC"; p.Model = "Sensation"; products.Add(p); p = new Product(); p.Make = "HTC"; p.Model = "Desire"; products.Add(p); p = new Product(); p.Make = "Nokia"; p.Model = "Some Model"; products.Add(p); p = new Product(); p.Make = "Nokia"; p.Model = "Some Model"; products.Add(p); p = new Product(); p.Make = "Sony Ericsson"; p.Model = "800i"; products.Add(p); p = new Product(); p.Make = "Sony Ericsson"; p.Model = "800i"; products.Add(p); return products; }   And then let’s bind the products to the GridView. protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { Gridview1.DataSource = GetProducts(); Gridview1.DataBind(); } }   Running the code will display something like this in the page: Now what I want is to get the distinct row values from the list. So what I did is to use the LINQ Distinct operator and unfortunately it doesn't work. In order for it work is you must use the overload method of the Distinct operator for you to get the desired results. So I’ve added this IEqualityComparer<T> class to compare values: class ProductComparer : IEqualityComparer<Product> { public bool Equals(Product x, Product y) { if (Object.ReferenceEquals(x, y)) return true; if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null)) return false; return x.Make == y.Make && x.Model == y.Model; } public int GetHashCode(Product product) { if (Object.ReferenceEquals(product, null)) return 0; int hashProductName = product.Make == null ? 0 : product.Make.GetHashCode(); int hashProductCode = product.Model.GetHashCode(); return hashProductName ^ hashProductCode; } }   After that you can then bind the GridView like this: protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { Gridview1.DataSource = GetProducts().Distinct(new ProductComparer()); Gridview1.DataBind(); } }   Running the page will give you the desired output below: As you notice, it now eliminates the duplicate rows in the GridView. Now what if we only want to get the distinct values for a certain field. For example I want to get the distinct “Make” values such as Samsung, Apple, HTC, Nokia and Sony Ericsson and populate them to a DropDownList control for filtering purposes. I was hoping the the Distinct operator has an overload that can compare values based on the property value like (GetProducts().Distinct(o => o.PropertyToCompare). But unfortunately it doesn’t provide that overload so what I did as a workaround is to use the GroupBy,Select and First LINQ query operators to achieve what I want. Here’s the code to get the distinct values of a certain field. protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { DropDownList1.DataSource = GetProducts().GroupBy(o => o.Make).Select(o => o.First()); DropDownList1.DataTextField = "Make"; DropDownList1.DataValueField = "Model"; DropDownList1.DataBind(); } } Running the code will display the following output below:   That’s it! I hope someone find this post useful!

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• ASP.NET Membership - Change password without asking the old (WITH Question and Answer)

  - by djsolid

  I have received many comments and questions about how you can do what is described in this post when you site requires question and answer. The solution is definiterly not the best and should be used with EXTREME caution because in a high traffic website can cause problems but I write it down anyway. We will use reflection in order to solve our problem. And this is the code But this code changes the only instance of MembershipProvider meaning if you access somewhere else from your application the property RequiresQuestionAndAnswer until you set back it’s original value you will get false instead of true. So again be VERY careful. Hope you find it useful!

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• Incorrect results for frustum cull

  - by DeadMG

  Previously, I had a problem with my frustum culling producing too optimistic results- that is, including many objects that were not in the view volume. Now I have refactored that code and produced a cull that should be accurate to the actual frustum, instead of an axis-aligned box approximation. The problem is that now it never returns anything to be in the view volume. As the mathematical support library I'm using does not provide plane support functions, I had to code much of this functionality myself, and I'm not really the mathematical type, so it's likely that I've made some silly error somewhere. As follows is the relevant code: class Plane { public: Plane() { r0 = Math::Vector(0,0,0); normal = Math::Vector(0,1,0); } Plane(Math::Vector p1, Math::Vector p2, Math::Vector p3) { r0 = p1; normal = Math::Cross((p2 - p1), (p3 - p1)); } Math::Vector r0; Math::Vector normal; }; This class represents one plane as a point and a normal vector. class Frustum { public: Frustum( const std::array<Math::Vector, 8>& points ) { planes[0] = Plane(points[0], points[1], points[2]); planes[1] = Plane(points[4], points[5], points[6]); planes[2] = Plane(points[0], points[1], points[4]); planes[3] = Plane(points[2], points[3], points[6]); planes[4] = Plane(points[0], points[2], points[4]); planes[5] = Plane(points[1], points[3], points[5]); } Plane planes[6]; }; The points are passed in order where (the inverse of) each bit of the index of each point indicates whether it's the left, top, and back of the frustum, respectively. As such, I just picked any three points where they all shared one bit in common to define the planes. My intersection test is as follows (based on this): bool Intersects(Math::AABB lhs, const Frustum& rhs) const { for(int i = 0; i < 6; i++) { Math::Vector pvertex = lhs.TopRightFurthest; Math::Vector nvertex = lhs.BottomLeftClosest; if (rhs.planes[i].normal.x <= -0.0f) { std::swap(pvertex.x, nvertex.x); } if (rhs.planes[i].normal.y <= -0.0f) { std::swap(pvertex.y, nvertex.y); } if (rhs.planes[i].normal.z <= -0.0f) { std::swap(pvertex.z, nvertex.z); } if (Math::Dot(rhs.planes[i].r0, nvertex) < 0.0f) { return false; } } return true; } Also of note is that because I'm using a left-handed co-ordinate system, I wrote my Cross function to return the negative of the formula given on Wikipedia. Any suggestions as to where I've made a mistake?

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• Is slower performance, of programming languages, really, a bad thing?

  - by Emanuil

  Here's how I see it. There's machine code and it's all that computers needs in order to run something. Computers don't care about programming languages. It doesn't matter to them whether the machine code comes from Perl, Python or PHP. Programming languages don't serve computers. They serve programmers. Some programming languages run slower than others but that's not necessarily because there is something wrong with them. In many cases, it's because they do more things that programmers would otherwise have to do (i.e. memory management) and by doing these things, they are better in what they are supposed to do - serve programmers. So, is slower performance, of programming languages, really, a bad thing?

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• where to define variable for a for each loop?

  - by David

  can you please advise me why my first code attempt didn't work : public void listAllFiles() { for(String filename : files) { int position = 0; System.out.println(position + ": " + filename); position = position + 1; } } it kept printing position at 0 without iterating position but it seems to work after i did it this way: public void listAllFiles() { int position = 0; for(String filename : files) { System.out.println(position + ": " + filename); position = position + 1; } } I don't understand why the position + 1 was not being executed, is it because we are not meant to define variables inside for loops or am i missing something in my code.

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• What's the best platform for blogging about coding? [closed]

  - by timday

  I'm toying with starting an occasional blog for posting odd bits of coding related stuff (mainly C++, probably). Are there any platforms which can be recommended as providing exceptionally good support (e.g syntax highlighting) for posting snippets of code ? (Or any to avoid because posting mono-spaced font blocks of text is a pain). Outcome: I accepted Josh K's answer because what I actually ended up doing was realizing I was more interested in articles than a blog style, getting back into LaTeX (after almost 20 years away from it), using the "listings" package for code, and pushing the HTML/PDF results to my ISP's static-hosting pages. (HTML generated using tex4ht). Kudos to the answers mentioning Wordpress, Tumblr and Jekyll; I spent some time looking into all of them.

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• Optimizing a thread safe Java NIO / Serialization / FIFO Queue [migrated]

  - by trialcodr

  I've written a thread safe, persistent FIFO for Serializable items. The reason for reinventing the wheel is that we simply can't afford any third party dependencies in this project and want to keep this really simple. The problem is it isn't fast enough. Most of it is undoubtedly due to reading and writing directly to disk but I think we should be able to squeeze a bit more out of it anyway. Any ideas on how to improve the performance of the 'take'- and 'add'-methods? /** * <code>DiskQueue</code> Persistent, thread safe FIFO queue for * <code>Serializable</code> items. */ public class DiskQueue<ItemT extends Serializable> { public static final int EMPTY_OFFS = -1; public static final int LONG_SIZE = 8; public static final int HEADER_SIZE = LONG_SIZE * 2; private InputStream inputStream; private OutputStream outputStream; private RandomAccessFile file; private FileChannel channel; private long offs = EMPTY_OFFS; private long size = 0; public DiskQueue(String filename) { try { boolean fileExists = new File(filename).exists(); file = new RandomAccessFile(filename, "rwd"); if (fileExists) { size = file.readLong(); offs = file.readLong(); } else { file.writeLong(size); file.writeLong(offs); } } catch (FileNotFoundException e) { throw new RuntimeException(e); } catch (IOException e) { throw new RuntimeException(e); } channel = file.getChannel(); inputStream = Channels.newInputStream(channel); outputStream = Channels.newOutputStream(channel); } /** * Add item to end of queue. */ public void add(ItemT item) { try { synchronized (this) { channel.position(channel.size()); ObjectOutputStream s = new ObjectOutputStream(outputStream); s.writeObject(item); s.flush(); size++; file.seek(0); file.writeLong(size); if (offs == EMPTY_OFFS) { offs = HEADER_SIZE; file.writeLong(offs); } notify(); } } catch (IOException e) { throw new RuntimeException(e); } } /** * Clears overhead by moving the remaining items up and shortening the file. */ public synchronized void defrag() { if (offs > HEADER_SIZE && size > 0) { try { long totalBytes = channel.size() - offs; ByteBuffer buffer = ByteBuffer.allocateDirect((int) totalBytes); channel.position(offs); for (int bytes = 0; bytes < totalBytes;) { int res = channel.read(buffer); if (res == -1) { throw new IOException("Failed to read data into buffer"); } bytes += res; } channel.position(HEADER_SIZE); buffer.flip(); for (int bytes = 0; bytes < totalBytes;) { int res = channel.write(buffer); if (res == -1) { throw new IOException("Failed to write buffer to file"); } bytes += res; } offs = HEADER_SIZE; file.seek(LONG_SIZE); file.writeLong(offs); file.setLength(HEADER_SIZE + totalBytes); } catch (IOException e) { throw new RuntimeException(e); } } } /** * Returns the queue overhead in bytes. */ public synchronized long overhead() { return (offs == EMPTY_OFFS) ? 0 : offs - HEADER_SIZE; } /** * Returns the first item in the queue, blocks if queue is empty. */ public ItemT peek() throws InterruptedException { block(); synchronized (this) { if (offs != EMPTY_OFFS) { return readItem(); } } return peek(); } /** * Returns the number of remaining items in queue. */ public synchronized long size() { return size; } /** * Removes and returns the first item in the queue, blocks if queue is empty. */ public ItemT take() throws InterruptedException { block(); try { synchronized (this) { if (offs != EMPTY_OFFS) { ItemT result = readItem(); size--; offs = channel.position(); file.seek(0); if (offs == channel.size()) { truncate(); } file.writeLong(size); file.writeLong(offs); return result; } } return take(); } catch (IOException e) { throw new RuntimeException(e); } } /** * Throw away all items and reset the file. */ public synchronized void truncate() { try { offs = EMPTY_OFFS; file.setLength(HEADER_SIZE); size = 0; } catch (IOException e) { throw new RuntimeException(e); } } /** * Block until an item is available. */ protected void block() throws InterruptedException { while (offs == EMPTY_OFFS) { try { synchronized (this) { wait(); file.seek(LONG_SIZE); offs = file.readLong(); } } catch (IOException e) { throw new RuntimeException(e); } } } /** * Read and return item. */ @SuppressWarnings("unchecked") protected ItemT readItem() { try { channel.position(offs); return (ItemT) new ObjectInputStream(inputStream).readObject(); } catch (ClassNotFoundException e) { throw new RuntimeException(e); } catch (IOException e) { throw new RuntimeException(e); } } }

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• How Do I Do Alpha Transparency Properly In XNA 4.0?

  - by Soshimo

  Okay, I've read several articles, tutorials, and questions regarding this. Most point to the same technique which doesn't solve my problem. I need the ability to create semi-transparent sprites (texture2D's really) and have them overlay another sprite. I can achieve that somewhat with the code samples I've found but I'm not satisfied with the results and I know there is a way to do this. In mobile programming (BREW) we did it old school and actually checked each pixel for transparency before rendering. In this case it seems to render the sprite below it blended with the alpha above it. This may be an artifact of how I'm rendering the texture but, as I said before, all examples point to this one technique. Before I go any further I'll go ahead and paste my example code. public void Draw(SpriteBatch batch, Camera camera, float alpha) { int tileMapWidth = Width; int tileMapHeight = Height; batch.Begin(SpriteSortMode.Texture, BlendState.AlphaBlend, SamplerState.PointWrap, DepthStencilState.Default, RasterizerState.CullNone, null, camera.TransformMatrix); for (int x = 0; x < tileMapWidth; x++) { for (int y = 0; y < tileMapHeight; y++) { int tileIndex = _map[y, x]; if (tileIndex != -1) { Texture2D texture = _tileTextures[tileIndex]; batch.Draw( texture, new Rectangle( (x * Engine.TileWidth), (y * Engine.TileHeight), Engine.TileWidth, Engine.TileHeight), new Color(new Vector4(1f, 1f, 1f, alpha ))); } } } batch.End(); } As you can see, in this code I'm using the overloaded SpriteBatch.Begin method which takes, among other things, a blend state. I'm almost positive that's my problem. I don't want to BLEND the sprites, I want them to be transparent when alpha is 0. In this example I can set alpha to 0 but it still renders both tiles, with the lower z ordered sprite showing through, discolored because of the blending. This is not a desired effect, I want the higher z-ordered sprite to fade out and not effect the color beneath it in such a manner. I might be way off here as I'm fairly new to XNA development so feel free to steer me in the correct direction in the event I'm going down the wrong rabbit hole. TIA

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• Debugging Minimum Translation Vector

  - by SyntheCypher

  I implemented the minimum translation vector from codezealot's tutorial on SAT (Separating Axis Theorem) but I'm having an issue I can't quite figure out. Here's the example I have: As you can see in top and bottom left images regardless of the side the of the green car which red car is penetrating the MTV for the red car still remains as a negative number also here is the same example when the front of the red car is facing the opposite direction the number will always be positive. When the red car is past the half way through the green car it should switch polarity. I thought I'd compensated for this in my code, but apparently not either that or it's a bug I can find. Here is my function for finding and returning the MTV, any help would be much appreciated: Code

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• LuaJit FFI and hiding C implementation details

  - by wirrbel

  I would like to extend an application using LuaJit FFI. Having seen http://luajit.org/ext_ffi_tutorial.html this is surprisingly easy when comparing this to the Lua C API. So far so good. However I do not plainly want to wrap C functions but provide a higher level API to users writing scripts for the application. Especially I do not want users to be able to access "primitives", i.e. the ffi.* namespace. Is this possible or will that ffi namespace be available to user's Lua scripts? On the issue of Sandboxing Lua I found http://lua-users.org/wiki/SandBoxes which is not talking about FFI though. Furthermore, the plan I have described above is assuming that the introduction of abstraction layers happens on the lua side of code. Is this an advisable approach or would you rather abstract functionality on the statically compiled code (on the C-side)?

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• CSS3PS : de Photoshop à la feuille de style grâce à un nouveau plug-in

  Convertissez vos calques Photoshop en CSS3 grâce à ce nouveau plugin Un nouveau plugin pour Photoshop vient de voir le jour : CSS3Ps. Ce plugin, entièrement gratuit, vous permettra de générer le plus simplement du monde du code CSS à partir de calques sous Photoshop. Il n'est pas rare, dans le monde du web design, de vouloir adapter des créations graphiques pour le design d'un site. Malheureusement, il est bien souvent compliqué de passer d'une image créée sous Photoshop à un style en CSS. La solution la plus simple étant d'utiliser l'image directement, mais cela ne permet aucune souplesse en terme de code CSS. Et c'est justement cette souplesse qu'appo...

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• Per-pixel collision detection - why does XNA transform matrix return NaN when adding scaling?

  - by JasperS

  I looked at the TransformCollision sample on MSDN and added the Matrix.CreateTranslation part to a property in my collision detection code but I wanted to add scaling. The code works fine when I leave scaling commented out but when I add it and then do a Matrix.Invert() on the created translation matrix the result is NaN ({NaN,NaN,NaN},{NaN,NaN,NaN},...) Can anyone tell me why this is happening please? Here's the code from the sample: // Build the block's transform Matrix blockTransform = Matrix.CreateTranslation(new Vector3(-blockOrigin, 0.0f)) * // Matrix.CreateScale(block.Scale) * would go here Matrix.CreateRotationZ(blocks[i].Rotation) * Matrix.CreateTranslation(new Vector3(blocks[i].Position, 0.0f)); public static bool IntersectPixels( Matrix transformA, int widthA, int heightA, Color[] dataA, Matrix transformB, int widthB, int heightB, Color[] dataB) { // Calculate a matrix which transforms from A's local space into // world space and then into B's local space Matrix transformAToB = transformA * Matrix.Invert(transformB); // When a point moves in A's local space, it moves in B's local space with a // fixed direction and distance proportional to the movement in A. // This algorithm steps through A one pixel at a time along A's X and Y axes // Calculate the analogous steps in B: Vector2 stepX = Vector2.TransformNormal(Vector2.UnitX, transformAToB); Vector2 stepY = Vector2.TransformNormal(Vector2.UnitY, transformAToB); // Calculate the top left corner of A in B's local space // This variable will be reused to keep track of the start of each row Vector2 yPosInB = Vector2.Transform(Vector2.Zero, transformAToB); // For each row of pixels in A for (int yA = 0; yA < heightA; yA++) { // Start at the beginning of the row Vector2 posInB = yPosInB; // For each pixel in this row for (int xA = 0; xA < widthA; xA++) { // Round to the nearest pixel int xB = (int)Math.Round(posInB.X); int yB = (int)Math.Round(posInB.Y); // If the pixel lies within the bounds of B if (0 <= xB && xB < widthB && 0 <= yB && yB < heightB) { // Get the colors of the overlapping pixels Color colorA = dataA[xA + yA * widthA]; Color colorB = dataB[xB + yB * widthB]; // If both pixels are not completely transparent, if (colorA.A != 0 && colorB.A != 0) { // then an intersection has been found return true; } } // Move to the next pixel in the row posInB += stepX; } // Move to the next row yPosInB += stepY; } // No intersection found return false; }

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• Support ARMv7 instruction set in Windows Embedded Compact applications

  - by Valter Minute

  On of the most interesting new features of Windows Embedded Compact 7 is support for the ARMv5, ARMv6 and ARMv7 instruction sets instead of the ARMv4 “generic” support provided by the previous releases. This means that code build for Windows Embedded Compact 7 can leverage features (like the FPU unit for ARMv6 and v7) and instructions of the recent ARM cores and improve their performances. Those improvements are noticeable in graphics, floating point calculation and data processing. The ARMv7 instruction set is supported by the latest Cortex-A8, A9 and A15 processor families. Those processor are currently used in tablets, smartphones, in-car navigation systems and provide a great amount of processing power and a low amount of electric power making them very interesting for portable device but also for any kind of device that requires a rich user interface, processing power, connectivity and has to keep its power consumption low. The bad news is that the compiler provided with Visual Studio 2008 does not provide support for ARMv7, building native applications using just the ARMv4 instruction set. Porting a Visual Studio “Smart Device” native C/C++ project to Platform Builder is not easy and you’ll lack many of the features that the VS2008 application development environment provides. You’ll also need access to the BSP and OSDesign configuration for your device to be able to build and debug your application inside Platform Builder and this may prevent independent software vendors from using the new compiler to improve their applications performances. Adeneo Embedded now provides a whitepaper and a Visual Studio plug-in that allows usage of the new ARMv7 enabled compiler to build applications inside Visual Studio 2008. I worked on the whitepaper and the tools, with the help of my colleagues and now the results can be downloaded from Adeneo Embedded’s website: http://www.adeneo-embedded.com/OS-Technologies/Windows-Embedded (Click on the “WEC7 ARMv7 Whitepaper tab to access the download links, free registration required) A very basic benchmark showed a very good performance improvement in integer and floating-point operations. Obviously your mileage may vary and we can’t promise the same amount of improvement on any application, but with a small effort on your side (even smaller if you use the plug-in) you can try on your own application. ARMv7 support is provided using Platform Builder’s compiler and VS2008 application debugger is not able to debut ARMv7 code, so you may need to put in place some workaround like keeping ARMv4 code for debugging etc.

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