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• Keeping your options open in a cloud solution

  - by BuckWoody

  In on-premises solutions we have the full range of options open for a given computing solution – but we don’t always take advantage of them, for multiple reasons. Data goes in a Relational Database Management System, files go on a share, and e-mail goes to the Exchange server. Over time, vendors (including ourselves) add in functionality to one product that allow non-standard use of the platform. For example, SQL Server (and Oracle, and others) allow large binary storage in or through the system – something not originally intended for an RDBMS to handle. There are certainly times when this makes sense, of course, but often these platform hammers turn every problem into a nail. It can make us “lazy” in our design – we sometimes don’t take the time to learn another architecture because the one we’ve spent so much time with can handle what we want to do. But there’s a distinct danger here. In nature, when a population shares too many of the same traits, it can cause a complete collapse if a situation exploits a weakness shared by that population. The same is true with not using the righttool for the job in a computing environment. Your company or organization depends on your knowledge as a professional to select the best mix of supportable, flexible, cost-effective technologies to solve their problems, whether you’re in an architect role or not.  So take some time today to learn something new. The way I do this is to select a given problem, and try to solve it with a technology I’m not familiar with. For instance – create a Purchase Order system in Excel, then in Hadoop or MongoDB, or even in flat-files using PowerShell as an interface. No, I’m not suggesting any of these architectures are the proper way to solve the PO problem, but taking something concrete that you know well and applying that meta-knowledge to another platform will assist you in exercising the “little grey cells” and help you and your organization understand what is open to you. And of course you can do all of this on-premises – but my recommendation is to check out a cloud platform (my suggestion would of course be Windows Azure :) ) and try it there. Most providers (including Microsoft) provide free time to do that.

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• Best system for creating a 2d racing track

  - by tesselode

  I am working a 2D racing game and I'm trying to figure out what is the best way to define the track. At the very least, I need to be able to create a closed circuit with any amount of turns at any angle, and I need vehicles to collide with the edges of the track. I also want the following things to be true if possible (but they are optional): The code is simple and free of funky workarounds and extras I can define all of the parts of the track (such as turns) relative to the previous parts I can predict the exact position of the road at a certain point (that way I can easily and cleanly make closed circuits) Here are my options: Use a set of points. This is my current system. I have a set of turns and width changes that the track is supposed to make over time. I have a point which I transform according to these instructions, and I place a point every 5 steps or so, depending on how precise I want the track to be. These points make up the track. The main problem with this is the discrepancy between the collisions and the way the track is drawn. I won't get into too much detail, but the picture below shows what is happening (although it is exaggerated a bit). The blue lines are what is drawn, the red lines are what the vehicle collides with. I could work around this, but I'd rather avoid funky workaround code. Beizer curves. These seem cool, but my first impression of them is that they'll be a little daunting to learn and are probably too complicated for my needs. Some other kind of curve? I have heard of some other kinds of curves; maybe those are more applicable. Use Box2D or another physics engine. Instead of defining the center of the track, I could use a physics engine to define shapes that make up the road. The downside to this, however, is that I have to put in a little more work to place the checkpoints. Something completely different. Basically, what is the simplest system for generating a race track that would allow me to create closed circuits cleanly, handle collisions, and not have a ton of weird code?

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• Adding JavaScript to your code dependent upon conditions

  - by DavidMadden

  You might be in an environment where you code is source controlled and where you might have build options to different environments.  I recently encountered this where the same code, built on different configurations, would have the website at a different URL.  If you are working with ASP.NET as I am you will have to do something a bit crazy but worth while.  If someone has a more efficient solution please share. Here is what I came up with to make sure the client side script was placed into the HEAD element for the Google Analytics script.  GA wants to be the last in the HEAD element so if you are doing others in the Page_Load then you should do theirs last. The settings object below is an instance of a class that holds information I collection.  You could read from different sources depending on where you stored your unique ID for Google Analytics. *** This has been formatted to fit this screen. *** if (!IsPostBack) { if (settings.GoogleAnalyticsID != null || settings.GoogleAnalyticsID != string.Empty) { string str = @"//<!CDATA[ var _gaq = _gaq || []; _gaq.push(['_setAccount', '"  + settings.GoogleAnalyticsID + "']); _gaq.push(['_trackPageview']);  (function () {  var ga = document.createElement('script');  ga.type = 'text/javascript';  ga.async = true;  ga.src = ('https:' == document.location.protocol  ? 'https://ssl' :  'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0];  s.parentNode.insertBefore(ga, s);})();"; System.Web.UI.HtmlControls.HtmlGenericControl si =  new System.Web.UI.HtmlControls.HtmlGenericControl(); si.TagName = "script"; si.Attributes.Add("type", @"text/javascript"); si.InnerHtml = sb.ToString(); this.Page.Header.Controls.Add(si); } } The code above will prevent the code from executing if it is a PostBack and then if the ID was not able to be read or something caused the settings to be lost by accident. If you have larger function to declare, you can use a StringBuilder to separate the lines. This is the most compact I wished to go and manage readability.

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• Some Problems Can't Be Outsourced

  - by mikef

  More and more companies are becoming attracted to the idea of Infrastructure as a Service (or IaaS). It would seem that you can outsource the provisioning and management of your services, encompassing everything from Email, through to your servers, workstations and software, all the way down to your LAN and internet services. This type of outsourcing can be a very attractive option for companies who have tight budgets who are short of technical skills or don't have the means to provide long-term IT support. Essentially, they can outsource your services at low short-term costs that are knowable and controllable, are quickly and easily scalable, and generate a minimum of hassle for your internal staff. If you want to get a sophisticated IT infrastructure set up in a hurry without the usual high buy-in costs, or the task of finding and hiring the right specialists. It would seem the way to go, particularly when their salesmen are hypnotizing you with oleaginous phrases such as "we are closely aligned with our client organization's core business requirements, providing agile services". It sounds too good to be true, and so it is. Whereas the costs will have initially been calculated on the annual renewal fees and service fees for ongoing support, there are other charges too which aren't so obvious. It can end up costing far more than the conventional solution once you take into account the extra costs, the fees for customization and upgrades. The Total Cost of Ownership (TCO) only becomes apparent when it is too late to extract the company easily from the arrangement. After a few years, these annual fees can add up to more than the initial cost of implementing a traditional in-house system. Worse than that is that you can then lose your power to determine your priorities: When you become reliant on this company, with its own schedule of priorities, to implement every change, however simple, you have effectively lost control of your technical infrastructure. This will make senior management very nervous. There is definitely a requirement for this sort of service. If you urgently need an exceptionally high class of service or more expertise than you currently possess, then outsourcing is probably for you. You and your IT colleagues will always have something to do, be it user assistance, smoothing out integrations with an external provider, or working on something entirely new. Heck, if you outsource to IBM, the SysAdmins can go along for the ride and polish their expertise. What you need to figure out is how much your time is worth, because time is ultimately all that outsourcing will buy you and your organization. Now you just need to convince your nervous CEO. Cheers, Michael

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• Is there a factory pattern to prevent multiple instances for same object (instance that is Equal) good design?

  - by dsollen

  I have a number of objects storing state. There are essentially two types of fields. The ones that uniquely define what the object is (what node, what edge etc), and the others that store state describing how these things are connected (this node is connected to these edges, this edge is part of these paths) etc. My model is updating the state variables using package methods, so all these objects act as immutable to anyone not in Model scope. All Objects extend one base type. I've toyed with the idea of a Factory approach which accepts a Builder object and constructs the applicable object. However, if an instance of the object already exists (ie would return true if I created the object defined by the builder and passed it to the equal method for the existing instance) the factory returns the current object instead of creating a new instance. Because the Equal method would only compare what uniquely defines the type of object (this is node A to node B) but won't check the dynamic state stuff (node A is currently connected to nodes C and E) this would be a way of ensuring anyone that wants my Node A automatically knows its state connections. More importantly it would prevent aliasing nightmares of someone trying to pass an instance of node A with different state then the node A in my model has. I've never heard of this pattern before, and it's a bit odd. I would have to do some overriding of serialization methods to make it work (ensure that when I read in a serilized object I add it to my facotry list of known instances, and/or return an existing factory in its place), as well as using a weakHashMap as if it was a weakHashSet to know whether an instance exists without worrying about a quasi-memory leak occuring. I don't know if this is too confusing or prone to its own obscure bugs. One thing I know is that plugins interface with lowest level hardware. The plugins have to be able to return state that is different than my memory; to tell my memory when its own state is inconsistent. I believe this is possible despite their fetching objects that exist in my memory; we allow building of objects without checking their consistency with the model until the addToModel is called anyways; and the existing plugins design was written before all this extra state existed and worked fine without ever being aware of it. Should I just be using some other design to avoid this crazyness? (I have another question to that affect that I'm posting).

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• Tricky situation with EF and Include while projecting (Select / SelectMany)

  - by Vincent Grondin

  Originally posted on: http://geekswithblogs.net/vincentgrondin/archive/2014/06/07/tricky-situation-with-ef-and-include-while-projecting-select.aspxHello, the other day I stumbled on a problem I had a while back with EF and Include method calls and decided this was it and I was going to blog about it…  This would sort of to pin it inside my head and maybe help others too !  So I was using DBContext and wanted to query a DBSet and include some of it’s associations and in the end, do a projection to get a list of Ids…   At first it seems easy…  Query your DBSet, call Include right afterward, then code the rest of your statement with the appropriate where clause and then, do the projection…   Well it wasn’t that easy as my query required I code my where on some entities a few degree further in the association chain and most of these links where “Many”…  I had to do my projection right away with the SelectMany method.  So I did my stuff and tested the query….  no association where loaded…  My Include statement was simply ignored !  Then I remembered this behavior and how to get it to work…  You need to move the Include AFTER your first projection (Select or SelectMany).  So my sequence became:   Query the DBSet, do the projection with SelectMany, Include the associations, code the where clause and do the final projection…. but it wouldn’t compile…   It kept saying that it could not find an “Include” method on an IQueryable… which is perfectly true!  I knew this should work so I went to the definition of the DBset and saw it inherited DBQuery and sure enough the include method was there…  So I had to cast my statement from start until the end of the first projection in a DBQuery then do the Includes and then the rest of my query….   Bottom line is, whenever your Include statement seem to be ignored, then maybe you will need to move them further down in your query and cast your statement in whatever class gives you access to the Include…   Happy coding all !

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• How do you make a bullet ricochet off a vertical wall?

  - by Bagofsheep

  First things first. I am using C# with XNA. My game is top-down and the player can shoot bullets. I've managed to get the bullets to ricochet correctly off horizontal walls. Yet, despite using similar methods (e.g. http://stackoverflow.com/questions/3203952/mirroring-an-angle) and reading other answered questions about this subject I have not been able to get the bullets to ricochet off a vertical wall correctly. Any method I've tried has failed and sometimes made ricocheting off a horizontal wall buggy. Here is the collision code that calls the ricochet method: //Loop through returned tile rectangles from quad tree to test for wall collision. If a collision occurs perform collision logic. for (int r = 0; r < returnObjects.Count; r++) if (Bullets[i].BoundingRectangle.Intersects(returnObjects[r])) Bullets[i].doCollision(returnObjects[r]); Now here is the code for the doCollision method. public void doCollision(Rectangle surface) { if (Ricochet) doRicochet(surface); else Trash = true; } Finally, here is the code for the doRicochet method. public void doRicochet(Rectangle surface) { if (Position.X > surface.Left && Position.X < surface.Right) { //Mirror the bullet's angle. Rotation = -1 * Rotation; //Moves the bullet in the direction of its rotation by given amount. moveFaceDirection(Sprite.Width * BulletScale.X); } else if (Position.Y > surface.Top && Position.Y < surface.Bottom) { } } Since I am only dealing with vertical and horizontal walls at the moment, the if statements simply determine if the object is colliding from the right or left, or from the top or bottom. If the object's X position is within the boundaries of the tile's X boundaries (left and right sides), it must be colliding from the top, and vice verse. As you can see, the else if statement is empty and is where the correct code needs to go.

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• June 2013 release of SSDT contains a minor bug that you should be aware of

  - by jamiet

  I have discovered what seems, to me, like a bug in the June 2013 release of SSDT and given the problems that it created yesterday on my current gig I thought it prudent to write this blog post to inform people of it. I’ve built a very simple SSDT project to reproduce the problem that has just two tables, [Table1] and [Table2], and also a procedure [Procedure1]: The two tables have exactly the same definition, both a have a single column called [Id] of type integer. CREATE TABLE [dbo].[Table1] (     [Id] INT NOT NULL PRIMARY KEY ) My stored procedure simply joins the two together, orders them by the column used in the join predicate, and returns the results: CREATE PROCEDURE [dbo].[Procedure1] AS     SELECT t1.*     FROM    Table1 t1     INNER JOIN Table2 t2         ON    t1.Id = t2.Id     ORDER BY Id Now if I create those three objects manually and then execute the stored procedure, it works fine: So we know that the code works. Unfortunately, SSDT thinks that there is an error here: The text of that error is: Procedure: [dbo].[Procedure1] contains an unresolved reference to an object. Either the object does not exist or the reference is ambiguous because it could refer to any of the following objects: [dbo].[Table1].[Id] or [dbo].[Table2].[Id]. Its complaining that the [Id] field in the ORDER BY clause is ambiguous. Now you may well be thinking at this point “OK, just stick a table alias into the ORDER BY predicate and everything will be fine!” Well that’s true, but there’s a bigger problem here. One of the developers at my current client installed this drop of SSDT and all of a sudden all the builds started failing on his machine – he had errors left right and centre because, as it transpires, we have a fair bit of code that exhibits this scenario.  Worse, previous installations of SSDT do not flag this code as erroneous and therein lies the rub. We immediately had a mass panic where we had to run around the department to our developers (of which there are many) ensuring that none of them should upgrade their SSDT installation if they wanted to carry on being productive for the rest of the day. Also bear in mind that as soon as a new drop of SSDT comes out then the previous version is instantly unavailable so rolling back is going to be impossible unless you have created an administrative install of SSDT for that previous version. Just thought you should know! In the grand schema of things this isn’t a big deal as the bug can be worked around with a simple code modification but forewarned is forearmed so they say! Last thing to say, if you want to know which version of SSDT you are running check my blog post Which version of SSDT Database Projects do I have installed? @Jamiet

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• 2D collision resolving

  - by Philippe Paré

  I've just worked out an AABB collision algorithm for my 2D game and I was very satisfied until I found out it only works properly with movements of 1 in X and 1 in Y... here it is: public bool Intersects(Rectanglef rectangle) { return this.Left < rectangle.Right && this.Right > rectangle.Left && this.Top < rectangle.Bottom && this.Bottom > rectangle.Top; } public bool IntersectsAny(params Rectanglef[] rectangles) { for (int i = 0; i < rectangles.Length; i++) { if (this.Left < rectangles[i].Right && this.Right > rectangles[i].Left && this.Top < rectangles[i].Bottom && this.Bottom > rectangles[i].Top) return true; } return false; } and here is how I use it in the update function of my player : public void Update(GameTime gameTime) { Rectanglef nextPosX = new Rectanglef(AABB.X, AABB.Y, AABB.Width, AABB.Height); Rectanglef nextPosY; if (Input.Key(Key.Left)) nextPosX.X--; if (Input.Key(Key.Right)) nextPosX.X++; bool xFree = !nextPosX.IntersectsAny(Boxes.ToArray()); if (xFree) nextPosY = new Rectanglef(nextPosX.X, nextPosX.Y, nextPosX.Width, nextPosX.Height); else nextPosY = new Rectanglef(AABB.X, AABB.Y, AABB.Width, AABB.Height); if (Input.Key(Key.Up)) nextPosY.Y--; if (Input.Key(Key.Down)) nextPosY.Y++; bool yFree = !nextPosY.IntersectsAny(Boxes.ToArray()); if (yFree) AABB = nextPosY; else if (xFree) AABB = nextPosX; } What I'm having trouble with, is a system where I can give float values to my movement and make it so there's a smooth acceleration. Do I have to retrieve the collision rectangle (the rectangle created by the other two colliding)? or should I do some sort of vector and go along this axis until I reach the collision? Thanks a lot!

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• Why occlusion is failing sometimes?

  - by cad

  I am rendering two cubes in the space using XNA 4.0 and occlusion only works from certain angles. Here is what I see from the front angle (everything ok) Here is what I see from behind This is my draw method. Cubes are drawn by serverManager and serverManager1 protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.CornflowerBlue); switch (_gameStateFSM.State) { case GameFSMState.GameStateFSM.INTROSCREEN: spriteBatch.Begin(); introscreen.Draw(spriteBatch); spriteBatch.End(); break; case GameFSMState.GameStateFSM.GAME: spriteBatch.Begin(SpriteSortMode.Deferred, BlendState.AlphaBlend); // Text screenMessagesManager.Draw(spriteBatch, firstPersonCamera.cameraPosition, fpsHelper.framesPerSecond); // Camera firstPersonCamera.Draw(); // Servers serverManager.Draw(GraphicsDevice, firstPersonCamera.viewMatrix, firstPersonCamera.projMatrix); serverManager1.Draw(GraphicsDevice, firstPersonCamera.viewMatrix, firstPersonCamera.projMatrix); // Room //roomManager.Draw(GraphicsDevice, firstPersonCamera.viewMatrix); spriteBatch.End(); break; case GameFSMState.GameStateFSM.EXITGAME: break; default: break; } base.Draw(gameTime); fpsHelper.IncrementFrameCounter(); } serverManager and serverManager1 are instances of the same class ServerManager that draws a cube. The draw method for ServerManager is: public void Draw(GraphicsDevice graphicsDevice, Matrix viewMatrix, Matrix projectionMatrix) { cubeEffect.World = Matrix.CreateTranslation(modelPosition); // Set the World matrix which defines the position of the cube cubeEffect.View = viewMatrix; // Set the View matrix which defines the camera and what it's looking at cubeEffect.Projection = projectionMatrix; // Enable textures on the Cube Effect. this is necessary to texture the model cubeEffect.TextureEnabled = true; cubeEffect.Texture = cubeTexture; // Enable some pretty lights cubeEffect.EnableDefaultLighting(); // apply the effect and render the cube foreach (EffectPass pass in cubeEffect.CurrentTechnique.Passes) { pass.Apply(); cubeToDraw.RenderToDevice(graphicsDevice); } } Obviously there is something I am doing wrong. Any hint of where to look? (Maybe z-buffer or occlusion tests?)

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• Code testing practice

  - by Robin Castlin

  So now I have come to the conclusion like many others that having some way of constantly testing your code is good practice since it enables fewer people to be involved (colleges and customers alike) by simply knowing what's wrong before someone else finds out the hard way. I've heard and read some about Unit Testing and understand what it's supposed to do and all. The there are so many different types of bugs. It can be everything from web browser not being able not being able to send correct values, javascript failing, a global function messing up a piece of code somewhere to a change that looked good when testing it out but fails in some special case which was hard to anticipate. My simply finding these errors I learn to rarely repeat them again, but there seems to always be new bugs to be found and learnt from. I would guess maybe the best practice would be to run every page and it's functions a couple of times, witness the result and repeat this in Firefox, Chrome and Internet Explorer (and all smartphones apparently) to make sure it works as intended. However this would take quite some time to do consider I don't work with patches/versions and do little fixes here and there a couple of times per week. What I prefer would be some kind of page I can just load that tests as much things as possible to make sure the site works as intended. Basicly just run a lot of cURL's with POST-values and see if I get expected result. But how would I preferably not increase the IDs of every mysql rows if I delete these testing rows? It feels silly to be on ID 1000 with maybe 50 rows in total. If I could build a new project from scratch I would probably implement some kind of smooth way to return a "TRUE" on testing instead of the actual page. But this solution would for the moment being have to be passed on existing projects. My question What would you recommend to be the best way to test my site to make sure that existing functions does their job upon editing the code? Should I consider to implement a lot of edits first, then test manually the entire code to make sure it still works? Is there any nice way of testing codes without "hurting" the ID columns? Extra thoughs Would it be a good idea to associate all of my files to the different parts of my site which they affect? For instance if I edit home.php I will through documentation test if my homepage's start works as intended since it's the only part of my site it should affect.

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• vJUG: Worldwide Virtual JUG Created

  - by Tori Wieldt

  London Java Community leader and technical evangelist Simon Maple has created a Meetup called vJUG, with aim toward connecting Java Developers in the virtual world. The aim for vJUG is: Get technical leaders from around the world to present to the vJUG members (without travel cost concerns!). Work with local JUGs to provide worldwide content to their members and help JUGs present to a worldwide audience. Provide content to devs without access to a local JUG. Be a hub that will stream content from other JUG sessions live.  The vJUG is not intended to replace local JUG efforts. "The vJUG can never be, and will never be, as vibrant and valuable to its members as a proper local JUG can. Why? Because the true value in JUG meetings are the face to face interactions and personal networking," said Maple. "However, many people do not have access to a really active JUG with great speakers and awesome content. Or, like me, the closest JUG is about 90 mins away." WebEx and Google Hangouts are great, Maple explained, he hopes vJUG will provide more coordination of online events.  Maple hopes that in the future, vJUG will provide An Events calendar with reminders and links to up coming meetings. A Newsletter with what's coming up and links to previous sessions. Coordination of links to IRC channels which are active during presentations (to create a feeling of virtual community). Comments and forums around sessions and presentations A place where physical JUGs could advertise their sessions (i.e. a NY JUG event) to a worldwide audience, when streamed, via an event that people can sign up to. A common Webex or Hangout. Maple encourages both people who need a JUG and existing JUG members to join vJUG. "I'm looking forward to talking with many of you one to get members, speakers, and JUG support!" Join vJUG now! (I sense a need for a logo...) 

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• How does the fstab 'defaults' option work? Is relatime recommended?

  - by hushs

  I know the fstab defaults option means this: rw,suid,dev,exec,auto,nouser,async. But what if I want to add one more option, for example relatime, should I still add defaults too or they are applied anyway? Is it needed to add at least one option? Some examples: 1. UUID=bfb42838-d866-4233-9679-96e7536356df /media/data ext3 defaults 0 2 2. UUID=bfb42838-d866-4233-9679-96e7536356df /media/data ext3 0 2 3. UUID=bfb42838-d866-4233-9679-96e7536356df /media/data ext3 defaults,relatime 0 2 4. UUID=bfb42838-d866-4233-9679-96e7536356df /media/data ext3 relatime 0 2 Is the (2) correct(no option at all)? Are the (1) and (2) the same? Are the (3) and (4) the same? Furthermore, I read in the Ubuntu Community Documentation that in Ubuntu 8.04 relatime was used as default for linux native file systems. Is it still true for 12.04? If yes, then why do I see this if I use the mount command: /dev/sda2 on / type ext4 (rw,errors=remount-ro) If no, why not? It isn't recommended to use relatime now? I just wanted to apply it to my non system partitions, it is a good idea? EDIT: I found an other command to list the mounted partitions and their options: cat /proc/mounts This is the result of a partition mounted with the defaults option in fstab: /dev/sdb2 /media/adat ext3 rw,relatime,errors=continue,barrier=1,data=ordered 0 0 This is the output of mount for the same partition: /dev/sdb2 on /media/adat type ext3 (rw) And here is both result if the same partition mounted from Nautilus as a non-root user: /dev/sdb2 /media/adat ext3 rw,nosuid,nodev,relatime,errors=continue,barrier=1,data=ordered 0 0 /dev/sdb2 on /media/adat type ext3 (rw,nosuid,nodev,uhelper=udisks) So it looks like relatime is used if we mount an ext partition in 12.04. So it is unneeded to add it manually. So my problem is broadly solved. But I still can't see why the options that should be in the defaults are not listed even with the cat /proc/mounts. Maybe there is a third and even better method to list the partition mount options :)

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• Is return-type-(only)-polymorphism in Haskell a good thing?

  - by dainichi

  One thing that I've never quite come to terms with in Haskell is how you can have polymorphic constants and functions whose return type cannot be determined by their input type, like class Foo a where foo::Int -> a Some of the reasons that I do not like this: Referential transparency: "In Haskell, given the same input, a function will always return the same output", but is that really true? read "3" return 3 when used in an Int context, but throws an error when used in a, say, (Int,Int) context. Yes, you can argue that read is also taking a type parameter, but the implicitness of the type parameter makes it lose some of its beauty in my opinion. Monomorphism restriction: One of the most annoying things about Haskell. Correct me if I'm wrong, but the whole reason for the MR is that computation that looks shared might not be because the type parameter is implicit. Type defaulting: Again one of the most annoying things about Haskell. Happens e.g. if you pass the result of functions polymorphic in their output to functions polymorphic in their input. Again, correct me if I'm wrong, but this would not be necessary without functions whose return type cannot be determined by their input type (and polymorphic constants). So my question is (running the risk of being stamped as a "discussion quesion"): Would it be possible to create a Haskell-like language where the type checker disallows these kinds of definitions? If so, what would be the benefits/disadvantages of that restriction? I can see some immediate problems: If, say, 2 only had the type Integer, 2/3 wouldn't type check anymore with the current definition of /. But in this case, I think type classes with functional dependencies could come to the rescue (yes, I know that this is an extension). Furthermore, I think it is a lot more intuitive to have functions that can take different input types, than to have functions that are restricted in their input types, but we just pass polymorphic values to them. The typing of values like [] and Nothing seems to me like a tougher nut to crack. I haven't thought of a good way to handle them. I doubt I am the first person to have had thoughts like these. Does anybody have links to good discussions about this Haskell design decision and the pros/cons of it?

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• PHP Fingerprinting CMS Versions by their meta tags [migrated]

  - by Mud

  Hey guys I'm having some issues with the speed of my script. I'm a novice I know so getting past that - what suggestions would you have to speed up my script? I was originally just reading in the index.php and then searching the <head> of the page for an array of strings. Then I read about the get_meta_tags and went that way. Then I had issues with some sites having 300 redirects in place so I used curl to check the URL existed and to speed up things but it's still taking 5 minutes or so to execute. <?php function url_exist($url){ $c=curl_init(); curl_setopt($c,CURLOPT_URL,$url); curl_setopt($c,CURLOPT_HEADER,1); curl_setopt($c,CURLOPT_NOBODY,1); curl_setopt($c,CURLOPT_RETURNTRANSFER,1); curl_setopt($c,CURLOPT_FRESH_CONNECT,1); if(!curl_exec($c)){ return false; }else{ return true; } curl_close($c); } function checkVersion($url){ $tags = get_meta_tags($url); if (is_array($tags) && array_key_exists('generator', $tags)) { $v = "<span style='background-color:#7BF55D;color:#A3A0A0'>".$tags['generator']."</span"; }else{ $v="<span style='background-color:#F55D67;color:#A3A0A0'>Metatag not found!</span>"; } return $v; } $row = 1; echo "<table>"; if (($handle = fopen("url.csv", "r")) !== FALSE) { while (($data = fgetcsv($handle, 1000, ",")) !== FALSE) { $num = count($data); $row++; for ($c=0; $c < $num; $c++) { if(url_exist($data[$c])){ echo "<tr><td>".$data[$c]."</td><td>".checkVersion($data[$c])."</td></tr>"; sleep(2); }else{ echo "<tr><td>".$data[$c]."</td><td><td><span style='background-color:#F55D5D;color:#A3A0A0'>URL not valid!<span></td></tr>"; } } } fclose($handle); } echo "</table>"; ?>

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• ArrayList of Entites Random Movement

  - by opiop65

  I have an arraylist of entites that I want to move randomly. No matter what I do, they won't move. Here is my female class: import java.awt.Graphics2D; import java.awt.Image; import java.awt.Rectangle; import java.util.Random; import javax.swing.ImageIcon; public class Female extends Entity { static int femaleX = 0; static int femaleY = 0; double walkSpeed = .1f; Random rand = new Random(); int random; int dir; Player player; public Female(int posX, int posY) { super(posX, posY); } public void update() { posX += femaleX; posY += femaleY; } public void draw(Graphics2D g2d) { g2d.drawImage(getFemaleImg(), posX, posY, null); if (Player.showBounds == true) { g2d.draw(getBounds()); } } public Image getFemaleImg() { ImageIcon ic = new ImageIcon("res/female.png"); return ic.getImage(); } public Rectangle getBounds() { return new Rectangle(posX, posY, getFemaleImg().getHeight(null), getFemaleImg().getWidth(null)); } public void moveFemale() { random = rand.nextInt(3); System.out.println(random); if (random == 0) { dir = 0; posX -= (int) walkSpeed; } } } And here is how I update the female class in the main class: public void actionPerformed(ActionEvent ae) { player.update(); for(int i = 0; i < females.size(); i++){ Female tempFemale = females.get(i); tempFemale.update(); } repaint(); } If I do something like this(in the female update method): public void update() { posX += femaleX; posY += femaleY; posX -= walkSpeed; } The characters move with no problem. Why is this?

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• Best Practice Method for Including Images in a DataGrid using MVVM

  - by Killercam

  All, I have a WPF DataGrid. This DataGrid shows files ready for compilation and should also show the progress of my compiler as it compiles the files. The format of the DataGrid is Image|File Path|State -----|---------|----- * |C:\AA\BB |Compiled & |F:PP\QQ |Failed > |G:HH\LL |Processing .... The problem is the image column (the *, &, and are for representation only). I have a ResourceDictionary that contains hundreds of vector images as Canvas objects: <ResourceDictionary xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"> <Canvas x:Key="appbar_acorn" Width="48" Height="48" Clip="F1 M 0,0L 48,0L 48,48L 0,48L 0,0"> <Path Width="22.3248" Height="25.8518" Canvas.Left="13.6757" Canvas.Top="11.4012" Stretch="Fill" Fill="{DynamicResource BlackBrush}" Data="F1 M 16.6309,18.6563C 17.1309,8.15625 29.8809,14.1563 29.8809,14.1563C 30.8809,11.1563 34.1308,11.4063 34.1308,11.4063C 33.5,12 34.6309,13.1563 34.6309,13.1563C 32.1309,13.1562 31.1309,14.9062 31.1309,14.9062C 41.1309,23.9062 32.6309,27.9063 32.6309,27.9062C 24.6309,24.9063 21.1309,22.1562 16.6309,18.6563 Z M 16.6309,19.9063C 21.6309,24.1563 25.1309,26.1562 31.6309,28.6562C 31.6309,28.6562 26.3809,39.1562 18.3809,36.1563C 18.3809,36.1563 18,38 16.3809,36.9063C 15,36 16.3809,34.9063 16.3809,34.9063C 16.3809,34.9063 10.1309,30.9062 16.6309,19.9063 Z "/> </Canvas> </ResourceDictionary> Now, I want to be able to include these in my image column and change them at run-time. I was going to attempt to do this by setting up a property in my View Model that was of type Image and binding this to my View via: <DataGrid.Columns> <DataGridTemplateColumn Header="" Width="SizeToCells" IsReadOnly="True"> <DataGridTemplateColumn.CellTemplate> <DataTemplate> <Image Source="{Binding Canvas}"/> </DataTemplate> </DataGridTemplateColumn.CellTemplate> </DataGridTemplateColumn> </DataGrid.Columns> Where in the View Model I have the appropriate property. Now, I was told this is not 'pure' MVVM. I don't fully accept this, but I want to know if there is a better way of doing this. Say, binding to an enum and using a converter to get the image? Any advice would be appreciated.

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• Object Oriented Design of a Small Java Game

  - by user2733436

  This is the problem i am dealing with. I have to make a simple game of NIM. I am learning java using a book so far i have only coded programs that deal with 2 classes. This program would have about 4 classes i guess including the main class. My problem is i am having a difficult time designing classes how they will interact with each other. I really want to think and use a object oriented approach. So the first thing i did was design the Pile CLASS as it seemed the easiest and made the most sense to me in terms of what methods go in it. Here is what i have got down for the Pile Class so far. package Nim; import java.util.Random; public class Pile { private int initialSize; public Pile(){ } Random rand = new Random(); public void setPile(){ initialSize = (rand.nextInt(100-10)+10); } public void reducePile(int x){ initialSize = initialSize - x; } public int getPile(){ return initialSize; } public boolean hasStick(){ if(initialSize>0){ return true; } else { return false; } } } Now i need help in designing the Player Class. By that i mean i am not asking for anyone to write code for me as that defeats the purpose of learning i was just wondering how would i design the player class and what would go on it. My guess is that the player class would contain method for choosing move for computer and also receiving the move human user makes. Lastly i am guessing in the Game class i am guessing the turns would be handeled. I am really lost right now so i was wondering if someone can help me think through this problem it would be great. Starting with the player class would be appreciated. I know there are some solutions for this problem online but i refuse to look at because i want to develop my own approach to such problems and i am confident if i can get through this problem i can solve other problems. I apologize if this question is a bit poor but in specific i need help in designing the Player class.

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• Why do some user agents have spam urls in them (and why are they always Opera/Presto User-Agents)?

  - by Erx_VB.NExT.Coder

  If you go to (say) the last 100 entries (visits) to the botsvsbrowsers.com website (exact link, feel free to take a look: http://www.botsvsbrowsers.com/recent/listings/index.html ), you'd notice that almost every User Agent that has the keywords "Opera" and "Presto" inside them, will almost certainly have a web link (URL/Web Address) inside it, and it won't just be a normal web address, but a HTML anchor tag/link to that address. Why is this so, I could not even find a single discussion about it on the internet, nowhere, I tried varying my search terms many times. If the user agent contains the words "Opera" and "Presto" it doesnt mean it will have this weblink, but it means there is about an 80% change that it will. A typical anchor tag/link inside a user agent will look like this: Mozilla/4.0 <a href="http://osis-uk.co.uk/disabled-equipment">disability equipment</a> (Windows NT 5.1; U; en) Presto/2.10.229 Version/11.60 If you check it out at the website, http://www.botsvsbrowsers.com/recent/listings/index.html you will notice that the back and forward arrows are in there unescaped format. This isn't just true for botsvsbrowsers, but several other user agent listing sites. I'm really confused and feel line I'm in a room full of 10,000 people and am the only one seeing this ghost :). If I'm doing statistical analysis, should I include or exclude this type of user agent from my listing (ie: are these just normal users who've set their user agents to attempt to drive some traffic to their sites as they browser the web), or is there something else going on? The fact that it is so consistent in terms of its format leads me to believe that it is an automated process (the setting or alteration of the user agent) so I cannot decide or understand the process by which this change is made (I know how to change a user agent), but unsure which program or facility is doing this, especially since it is exclusive to Opera (Presto) user agents that are beyond I think an 8 or 9 point something browser version. I've run some statistical tests, parsing entries from all over the place, writing custom programs, to get a better understanding of this. Keep in mind that I see normal URL's in user agents infrequently, they are just text such as +http://www.someSite.com appended to a user agent normally, especially if its a crawler or bot it provided its service URL, this is normal and isnt done with an embedded link (A HREF=) etc, so I'm not talking about "those".

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• Why is Java the lingua franca at so many institutions?

  - by Billy ONeal

  EDIT: This question at first seems to be bashing Java, and I guess at this point it is a bit. However, the bigger point I am trying to make is why any one single language is chosen as the one end all be all solution to all problems. Java happens to be the one that's used so that's the one I had to beat on here, but I'm not intentionality ripping Java a new one :) I don't like Java in most academic settings. I'm not saying the language itself is bad -- it has several extremely desirable aspects, most importantly the ability to run without recompilation on most any platform. Nothing wrong with using the language for Your Next App ^TM. (Not something I would personally do, but that's more because I have less experience with it, rather than it's design being poor) I think it is a waste that high level CS courses are taught using Java as a language. Too many of my co-students cannot program worth a damn, because they don't know how to work in a non-garbage-collected world. They don't fundamentally understand the machines they are programming for. When someone can work outside of a garbage collected world, they can work inside of one, but not vice versa. GC is a tool, not a crutch. But the way it is used to teach computer science students is a as a crutch. Computer science should not teach an entire suite of courses tailored to a single language. Students leave with the idea that all good design is idiomatic Java design, and that Object Oriented Design is the ONE TRUE WAY THAT IS THE ONLY WAY THINGS CAN BE DONE. Other languages, at least one of them not being a garbage collected language, should be used in teaching, in order to give the graduate a better understanding of the machines. It is an embarrassment that somebody with a PHD in CS from a respected institution cannot program their way out of a paper bag. What's worse, is that when I talk to those CS professors who actually do understand how things operate, they share feelings like this, that we're doing a disservice to our students by doing everything in Java. (Note that the above would be the same if I replaced it with any other language, generally using a single language is the problem, not Java itself) In total, I feel I can no longer respect any kind of degree at all -- when I can't see those around me able to program their way out of fizzbuzz problems. Why/how did it get to be this way?

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• Advantages to Multiple Methods over Switch

  - by tandu

  I received a code review from a senior developer today asking "By the way, what is your objection to dispatching functions by way of a switch statement?" I have read in many places about how pumping an argument through switch to call methods is bad OOP, not as extensible, etc. However, I can't really come up with a definitive answer for him. I would like to settle this for myself once and for all. Here are our competing code suggestions (php used as an example, but can apply more universally): class Switch { public function go($arg) { switch ($arg) { case "one": echo "one\n"; break; case "two": echo "two\n"; break; case "three": echo "three\n"; break; default: throw new Exception("Unknown call: $arg"); break; } } } class Oop { public function go_one() { echo "one\n"; } public function go_two() { echo "two\n"; } public function go_three() { echo "three\n"; } public function __call($_, $__) { throw new Exception("Unknown call $_ with arguments: " . print_r($__, true)); } } Part of his argument was "It (switch method) has a much cleaner way of handling default cases than what you have in the generic __call() magic method." I disagree about the cleanliness and in fact prefer call, but I would like to hear what others have to say. Arguments I can come up with in support of Oop scheme: A bit cleaner in terms of the code you have to write (less, easier to read, less keywords to consider) Not all actions delegated to a single method. Not much difference in execution here, but at least the text is more compartmentalized. In the same vein, another method can be added anywhere in the class instead of a specific spot. Methods are namespaced, which is nice. Does not apply here, but consider a case where Switch::go() operated on a member rather than a parameter. You would have to change the member first, then call the method. For Oop you can call the methods independently at any time. Arguments I can come up with in support of Switch scheme: For the sake of argument, cleaner method of dealing with a default (unknown) request Seems less magical, which might make unfamiliar developers feel more comfortable Anyone have anything to add for either side? I'd like to have a good answer for him.

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• Why is my collision detection not accurate?

  - by optimisez

  After trying and trying, I still cannot understand why the leg of character exceeds the wall but no clipping issue when I hit the wall from below. How should I fix it to make him stand still on the wall? From collideWithBox() function below, it shows that playerDest.Y = boxDest.Y - boxDest.height; will get the position the character should standstill on the wall. Theoretically, the clipping effect won't be happen as the character hit the box from below works with the equation playerDest.Y = boxDest.Y + boxDest.height;. void collideWithBox() { if ( spriteCollide(playerDest, boxDest) && keyArr[VK_UP]) //playerDest.Y += 50; playerDest.Y = boxDest.Y + boxDest.height; else if ( spriteCollide(playerDest, boxDest) && !keyArr[VK_UP]) playerDest.Y = boxDest.Y - boxDest.height; } void initPlayer() { // Create texture. hr = D3DXCreateTextureFromFileEx(d3dDevice, "player.png", 169, 44, D3DX_DEFAULT, NULL, D3DFMT_A8R8G8B8, D3DPOOL_MANAGED, D3DX_DEFAULT, D3DX_DEFAULT, D3DCOLOR_XRGB(255, 255, 255), NULL, NULL, &player); playerRect.left = playerRect.top = 0; playerRect.right = 29; playerRect.bottom = 36; playerDest.X = 0; playerDest.Y = 564; playerDest.length = playerRect.right - playerRect.left; playerDest.height = playerRect.bottom - playerRect.top; } void initBox() { hr = D3DXCreateTextureFromFileEx(d3dDevice, "brock.png", 330, 132, D3DX_DEFAULT, NULL, D3DFMT_A8R8G8B8, D3DPOOL_MANAGED, D3DX_DEFAULT, D3DX_DEFAULT, D3DCOLOR_XRGB(255, 255, 255), NULL, NULL, &box); boxRect.left = 33; boxRect.top = 0; boxRect.right = 63; boxRect.bottom = 30; boxDest.X = boxDest.Y = 300; boxDest.length = boxRect.right - boxRect.left; boxDest.height = boxRect.bottom - boxRect.top; } bool spriteCollide(Entity player, Entity target) { float left1, left2; float right1, right2; float top1, top2; float bottom1, bottom2; left1 = player.X; left2 = target.X; right1 = player.X + player.length; right2 = target.X + target.length; top1 = player.Y; top2 = target.Y; bottom1 = player.Y + player.height; bottom2 = target.Y + target.height; if (bottom1 < top2) return false; if (top1 > bottom2) return false; if (right1 < left2) return false; if (left1 > right2) return false; return true; }

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• C# Collision Math Help

  - by user36037

  I am making my own collision detection in MonoGame. I have a PolyLine class That has a property to return the normal of that PolyLine instance. I have a ConvexPolySprite class that has a List LineSegments. I hav a CircleSprite class that has a Center Property and a Radius Property. I am using a static class for the collision detection method. I am testing it on a single line segment. Vector2(200,0) = Vector2(300, 200) The problem is it detects the collision anywhere along the path of line out into space. I cannot figure out why. Thanks in advance; public class PolyLine { //--------------------------------------------------------------------------------------------------------------------------- // Class Properties /// <summary> /// Property for the upper left-hand corner of the owner of this instance /// </summary> public Vector2 ParentPosition { get; set; } /// <summary> /// Relative start point of the line segment /// </summary> public Vector2 RelativeStartPoint { get; set; } /// <summary> /// Relative end point of the line segment /// </summary> public Vector2 RelativeEndPoint { get; set; } /// <summary> /// Property that gets the absolute position of the starting point of the line segment /// </summary> public Vector2 AbsoluteStartPoint { get { return ParentPosition + RelativeStartPoint; } }//end of AbsoluteStartPoint /// <summary> /// Gets the absolute position of the end point of the line segment /// </summary> public Vector2 AbsoluteEndPoint { get { return ParentPosition + RelativeEndPoint; } }//end of AbsoluteEndPoint public Vector2 NormalizedLeftNormal { get { Vector2 P = AbsoluteEndPoint - AbsoluteStartPoint; P.Normalize(); float x = P.X; float y = P.Y; return new Vector2(-y, x); } }//end of NormalizedLeftNormal //--------------------------------------------------------------------------------------------------------------------------- // Class Constructors /// <summary> /// Sole ctor /// </summary> /// <param name="parentPosition"></param> /// <param name="relStart"></param> /// <param name="relEnd"></param> public PolyLine(Vector2 parentPosition, Vector2 relStart, Vector2 relEnd) { ParentPosition = parentPosition; RelativeEndPoint = relEnd; RelativeStartPoint = relStart; }//end of ctor }//end of PolyLine class public static bool Collided(CircleSprite circle, ConvexPolygonSprite poly) { var distance = Vector2.Dot(circle.Position - poly.LineSegments[0].AbsoluteEndPoint, poly.LineSegments[0].NormalizedLeftNormal) + circle.Radius; if (distance <= 0) { return false; } else { return true; } }//end of collided

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• Collision rectangle response

  - by dotty

  I'm having difficulties getting a moveable rectangle to collide with more than one rectangle. I'm using SFML and it has a handy function called Intersect() which takes 2 rectangles and returns the intersections. I have a vector full of rectangles which I want my moveable rectangle to collide with. I'm looping through this using the following code (p is the moveble rectangle). IsCollidingWith returns a bool but also uses SFML's Interesect to work out the intersections. while(unsigned i = 0; i!= testRects.size(); i++){ if(p.IsCollidingWith(testRects[i]){ p.Collide(testRects[i]); } } and the actual Collide() code void gameObj::collide( gameObj collidingObject ){ printf("%f %f\n", this->colliderResult.width, this->colliderResult.height); if (this->colliderResult.width < this->colliderResult.height) { // collided on X if (this->getCollider().left < collidingObject.getCollider().left ) { this->move( -this->colliderResult.width , 0); }else { this->move( this->colliderResult.width, 0 ); } } if(this->colliderResult.width > this->colliderResult.height){ if (this->getCollider().top < collidingObject.getCollider().top ) { this->move( 0, -this->colliderResult.height); }else { this->move( 0, this->colliderResult.height ); } } } and the IsCollidingWith() code is bool gameObj::isCollidingWith( gameObj testObject ){ if (this->getCollider().intersects( testObject.getCollider(), this->colliderResult )) { return true; }else { return false; } } This works fine when there's only 1 Rect in the scene. However, when there's move than one Rect it causes issue when working out 2 collisions at once. Any idea how to deal with this correctly? I have uploaded a video to youtube to show my problem. The console on the far-right shows the width and height of the intersections. You can see on the console that it's trying to calculate 2 collisions at once, I think this is where the problem is being caused. The youtube video is at http://www.youtube.com/watch?v=fA2gflOMcAk also , this image also seems to illustrate the problem nicely. Can someone please help, I've been stuck on this all weekend!

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• Silverlight and WCF caching

  - by subodhnpushpak

  There are scenarios where Silverlight client calls WCF (or REST) service for data. Now, if the data is cached on the WCF layer, the calls can take considerable resources at the server if NOT cached. Keeping that in mind along with the fact that cache is an cross-cutting aspect, and therefore it should be as easy as possible to put Cache wherever required. The good thing about the solution is that it caches based on the inputs. The input can be basic type of any complex type. If input changes the data is fetched and then cached for further used. If same input is provided again, data id fetched from the cache. The cache logic itself is implemented as PostSharp aspect, and it is as easy as putting an attribute over service call to switch on cache. Notice how clean the code is:        [OperationContract]       [CacheOnArgs(typeof(int))] // based on actual value of cache        public string DoWork(int value)        {            return string.Format("You entered: {0} @ cached time {1}", value, System.DateTime.Now);        } The cache is implemented as POST Sharp as below 1: public override void OnInvocation(MethodInvocationEventArgs eventArgs) 2: { 3: try 4: { 5: object value = new object(); 6: object[] args = eventArgs.GetArgumentArray(); 7: if (args != null || args.Count() > 0) 8: { 9:   10: string key = string.Format("{0}_{1}", eventArgs.Method.Name, XMLUtility<object>.GetDataContractXml(args[0], null));// Compute the cache key (details omitted). 11:   12: 13: value = GetFromCache(key); 14: if (value == null) 15: { 16: eventArgs.Proceed(); 17: value = XMLUtility<object>.GetDataContractXml(eventArgs.ReturnValue, null); 18: value = eventArgs.ReturnValue; 19: AddToCache(key, value); 20: return; 21: } 22:   23:   24: Log(string.Format("Data returned from Cache {0}",value)); 25: eventArgs.ReturnValue = value; 26: } 27: } 28: catch (Exception ex) 29: { 30: //ApplicationLogger.LogException(ex.Message, Source.UtilityService); 31: } 32: } 33:   34: private object GetFromCache(string inputKey) { if (ServerConfig.CachingEnabled) { return WCFCache.Current[inputKey]; } return null; }private void AddToCache(string inputKey,object outputValue) 35: { 36: if (ServerConfig.CachingEnabled) 37: { 38: if (WCFCache.Current.CachedItemsNumber < ServerConfig.NumberOfCachedItems) 39: { 40: if (ServerConfig.SlidingExpirationTime <= 0 || ServerConfig.SlidingExpirationTime == int.MaxValue) 41: { 42: WCFCache.Current[inputKey] = outputValue; 43: } 44: else 45: { 46: WCFCache.Current.Insert(inputKey, outputValue, new TimeSpan(0, 0, ServerConfig.SlidingExpirationTime), true); 47:   48: // _bw.DoWork += bw_DoWork; 49: //string arg = string.Format("{0}|{1}", inputKey,outputValue); 50: //_bw.RunWorkerAsync(inputKey ); 51: } 52: } 53: } 54: }     The cache class can be extended to support Velocity / memcahe / Nache. the attribute can be used over REST services as well. Hope the above helps. Here is the code base for the same.   Please do provide your inputs / comments.

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