Search Results

Search found 23265 results on 931 pages for 'justin case'.

Page 258/931 | < Previous Page | 254 255 256 257 258 259 260 261 262 263 264 265  | Next Page >

  • How do I restore the privacy pane of the system settings?

    - by Sparhawk
    Checking out screenshots of the system settings in Ubuntu 12.10, it seems that I am missing a few. When I open up my settings, I cannot see Privacy, Backup, and Management Service. Also, nothing comes up when I search the Dash for these words. In a previous edition of Ubuntu, I purged Ubuntu One (with sudo apt-get purge ubuntuone-client python-ubuntuone-storage* ubuntuone-couch ubuntuone-installer) and appropriately, I cannot see the Ubuntu One icon. I've also previously purged unity-lens-music Perhaps I purged some metapackage that removed the others? In any case, how do I restore the privacy pane (as well as the other icons)? Also, any suggestions for what I did to remove the packages in the first place (and hence how to avoid this problem in the future)?

    Read the article

  • Can I have a .desktop Launcher for both Python2 and Python3 depending on version installed?

    - by Takkat
    After very few issues only I moved my application from Python2 to Python3 making sure it will still run with Python 2.7, and hence has python = 2.7 as dependency only. This was mainly done because Python3, and some dependencies are not installed in a default 12.04 LTS, and I do not want my users to have to install all Python3 only to run my script. When I create an appname.desktop launcher I now need to decide if it starts my application using Python2, or Python3 like EXEC=python /path/app.py EXEC=python3 /path/app.py But what I would like it to do is to Launch the application with the Python3 interpreter if Python3 is installed. Otherwise use Python2 if Python3 is not installed. How can this be done? Do I need to tell it in my package installation script, or can I have a launcher which can handle both (in case people install Python3 after they had installed my script)?

    Read the article

  • Can not resolve hostnames on Xubuntu computers

    - by P Curtis
    I have a network of computers which has been running for many years. I have changed two of those to Xubuntu 11.10 and found I can no longer connect by ssh using the host-name from any other machine. I can connect and ping by IP although ping is very slow in one case (~200ms). All other machines are fine including another with Ubuntu 11.10. Host-name resolution works from Xubuntu machines to other networked machines. I am using wins resolution and have checked settings in /etc/nsswitch.conf are the same as my working Ubuntu systems. What is different in Xubuntu networking that I might have missed?

    Read the article

  • Using multiple A-records for my domain - do web browsers ever try more than one?

    - by Jonas
    If I add multiple A-records for my domain, they are returned in a round robin order by DNS-servers. E.g: 1.1.1.1 A example.com 1.1.1.2 A example.com 1.1.1.3 A example.com But how does webbrowsers react if the first host (1.1.1.1) is down (unreachable)? do they try the second host (1.1.1.2) or do they return a error message to the user? Are there any difference between the most popular browsers? If I implement my own application, I can implement so that the second is used in case the first is down, so it's possible. And this would be very helpful to create a fault tolerant website.

    Read the article

  • Customizing UPK outputs (Part 2 - Player)

    - by [email protected]
    There are a few things that can be done to give the Player output a personalized look to match your corporate branding. In my previous post, I talked about changing the logo. In addition to the logo, you can change the graphic in the heading, button colors, border colors and many other items. Prior to making any customizations, I strongly recommend making a copy of the existing Player style. This will give you a backup in case things go wrong. I'd also recommend that you create your own brand. This way, when you install the newest updates from us, your brand will remain intact. Creating your own brand is pretty easy. Make sure you have modify permissions on the publishing styles directory, if you are using a multi-user installation. Under the Publishing/Styles folder, create a new folder with your company name. Copy all the publishing styles from the UPK folder to your newly created folder. Now, when you go through the Publishing wizard, you will have two categories to choose from: the UPK category or your custom category. Now, for updating the Player output. First, the graphic that appears on the right hand side of the Player. If you're using a multi-user installation, check out the player style from your custom brand. Open the player style. Open the img folder. The file named "banner_image.png" represents the graphic that appears on the right hand side of the player. It is currently sized at 425 x 54. Try to keep your graphic about the same size. Rename your graphic file to be "banner_image.png", and drag it into the img folder. Save the package. Check in the package if you are in a multi-user installation. You've just updated the banner heading! Next, let's work on updating some of the other colors in the player. All the customizable areas are located in the skin.css file which is in the root of the Player style. Many of our customers update the colors to match their own theme. You don't have to be a programmer to make these changes, honest. :) To change the colors in the player: Make a copy of the original skin.css file. (This is to make sure you have a working version to revert to, in case something goes wrong.) Open the skin.css file from the Player package. You can edit it using Notepad. Make the desired changes. Save the file. Save the package. Publish to view your new changes. When you open the skin.css, you will see groupings like this: .headerDivbar { height: 21px; background-color: #CDE2FD; } Change the value of the background-color to the color of your choice. Note that you cannot use "red" as a color, but rather you should enter the hexadecimal color code. If you don't know the color code, search the web for "hexadecimal colors" and you'll find many sites to provide the information. Here are a few of the variables that you can update. Heading: .headerDivbar -this changes the color of the banner that appears under the graphic Button colors: .navCellOn - changes the color of the mode buttons when your mouse is hovering on them. .navCellOff - changes the color of the mode buttons when the mouse is not over them Lines: .thorizontal - this is the color of the horizontal lines surrounding the outline .tvertical - this is the color of the vertical lines on the left and right margin in the outline. .tsep - this is the color of the line that separates the outline from the content area Search frame: .tocSearchColor - this is the color of the search area .tocFrameText - this is the background color of the TOC tree. Hint: If you want to try out the changes prior to updating the style, you can update the skin.css in some content you've already published for the player (it's located in the css folder of the player package). This way, you can immediately see the changes without going through publishing. Once you're happy with the changes, update the skin.css in player style. Want to customize more? Refer to the "Customizing the Player" section of the Content Development manual for more details on all the options in the skin.css that can be changed, and pictures of what each variable controls. I'd love to see how you've customized the player for your corporate needs. Also, if there are other areas of the player you'd like to modify but have not been able to, let us know. Feel free to share your thoughts in the comments. --Maria Cozzolino, Manager of Requirements & UI Design for UPK

    Read the article

  • Nearly technical books that you enjoyed reading

    - by pablo
    I've seen questions about "What books you recommend" in several of the Stack Exchange verticals. Perhaps these two questions (a and b) are the most popular. But, I'd like to ask for recommendations of a different kind of books. I have read in the past "The Passionate Programmer" and I am now reading "Coders at Work". Both of them I would argue that are almost a biography (or biographies in the "Coders at work") or even a bit of "self-help" book (that is more the case of the "Passionate programmer"). And please don't get me wrong. I loved reading the first one, and I am loving reading the second one. There's a lot of value in it, mostly in "lessons of the trade" kind of way. So, here is what I'd like to know. What other books that you read that are similar to these ones in intent that you enjoyed? Why?

    Read the article

  • How to boot load the kernel using EFI stub (efistub) loader?

    - by Pro Backup
    I have Ubuntu 14.04 running in UEFI mode as only operating system, no dual-boot here. The kernel version is 3.13.0-24-generic. There is an EFI partition. In this case the EFI partition is not at the default /dev/sda1 but at /dev/sda3 because I did actually convert BIOS mode to EFI mode. I have used the grub-efi-amd64 package, though that actually loads GRUB boot menu from UEFI firmware boot menu (UEFI boot loads \EFI\ubuntu\grubx64.efi). I want to skip that double boot menu loading step, and boot faster, directly from UEFI into the kernel. The Ubuntu kernels since 12.10 have "Kernel EFI stub loader" feature. I know I do need to copy the Ubuntu kernel to the EFI partition (possibly rename) and create an entry in UEFI boot menu (for instance using efibootmgr). Which exact terminal commands are necessary to do this?

    Read the article

  • Big Data – Buzz Words: What is HDFS – Day 8 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned what is MapReduce. In this article we will take a quick look at one of the four most important buzz words which goes around Big Data – HDFS. What is HDFS ? HDFS stands for Hadoop Distributed File System and it is a primary storage system used by Hadoop. It provides high performance access to data across Hadoop clusters. It is usually deployed on low-cost commodity hardware. In commodity hardware deployment server failures are very common. Due to the same reason HDFS is built to have high fault tolerance. The data transfer rate between compute nodes in HDFS is very high, which leads to reduced risk of failure. HDFS creates smaller pieces of the big data and distributes it on different nodes. It also copies each smaller piece to multiple times on different nodes. Hence when any node with the data crashes the system is automatically able to use the data from a different node and continue the process. This is the key feature of the HDFS system. Architecture of HDFS The architecture of the HDFS is master/slave architecture. An HDFS cluster always consists of single NameNode. This single NameNode is a master server and it manages the file system as well regulates access to various files. In additional to NameNode there are multiple DataNodes. There is always one DataNode for each data server. In HDFS a big file is split into one or more blocks and those blocks are stored in a set of DataNodes. The primary task of the NameNode is to open, close or rename files and directory and regulate access to the file system, whereas the primary task of the DataNode is read and write to the file systems. DataNode is also responsible for the creation, deletion or replication of the data based on the instruction from NameNode. In reality, NameNode and DataNode are software designed to run on commodity machine build in Java language. Visual Representation of HDFS Architecture Let us understand how HDFS works with the help of the diagram. Client APP or HDFS Client connects to NameSpace as well as DataNode. Client App access to the DataNode is regulated by NameSpace Node. NameSpace Node allows Client App to connect to the DataNode based by allowing the connection to the DataNode directly. A big data file is divided into multiple data blocks (let us assume that those data chunks are A,B,C and D. Client App will later on write data blocks directly to the DataNode. Client App does not have to directly write to all the node. It just has to write to any one of the node and NameNode will decide on which other DataNode it will have to replicate the data. In our example Client App directly writes to DataNode 1 and detained 3. However, data chunks are automatically replicated to other nodes. All the information like in which DataNode which data block is placed is written back to NameNode. High Availability During Disaster Now as multiple DataNode have same data blocks in the case of any DataNode which faces the disaster, the entire process will continue as other DataNode will assume the role to serve the specific data block which was on the failed node. This system provides very high tolerance to disaster and provides high availability. If you notice there is only single NameNode in our architecture. If that node fails our entire Hadoop Application will stop performing as it is a single node where we store all the metadata. As this node is very critical, it is usually replicated on another clustered as well as on another data rack. Though, that replicated node is not operational in architecture, it has all the necessary data to perform the task of the NameNode in the case of the NameNode fails. The entire Hadoop architecture is built to function smoothly even there are node failures or hardware malfunction. It is built on the simple concept that data is so big it is impossible to have come up with a single piece of the hardware which can manage it properly. We need lots of commodity (cheap) hardware to manage our big data and hardware failure is part of the commodity servers. To reduce the impact of hardware failure Hadoop architecture is built to overcome the limitation of the non-functioning hardware. Tomorrow In tomorrow’s blog post we will discuss the importance of the relational database in Big Data. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

    Read the article

  • 2D pathfinding - finding smooth paths

    - by Kooi Nam Ng
    I was trying to implement a simple pathfinding, but the outcome is less satisfactory than what I intended to achieve. The thing is units in games like Starcraft 2 move in all directions whereas units in my case only move in at most 8 directions (Warcraft 1 style) as these 8 directions direct to next available nodes (they move from a tile to next neighboring tile). What should I do in order to achieve the result as in Starcraft 2? Shrink the tile size? On the picture you can see a horizontal line of rock tiles being obstacles, and the found path marked as green tiles. The red line is the path I want to achieve.

    Read the article

  • Unable to wake display with remote

    - by Eugene
    I'm running an HTPC (xbmc) without a keyboard/mouse attached, running oneiric. After some indeterminate amount of time, sometime between 1 and 12 hours, the display goes to sleep. The computer itself is not sleeping, I can still SSH to it from another computer. The remote will not wake the display. The IR receiver is working, as irw will show me the remote key presses. The only way to get my display back is to restart the display manager, lightdm in this case. Does anybody know a way to keep the display from going to sleep? I don't really need any power management at all considering that it connects to my TV and when I want my display to go to sleep, I turn off my TV.

    Read the article

  • Checking is sides of cubes are solid

    - by Christian Frantz
    In relation to this question: http://gamedev.stackexchange.com/a/28524/31664 And a question I asked earlier: Creating a DrawableGameComponent And also because my internet is too slow to get on chat. I'm wondering how to check if the sides of a cube are solid. I've created 12 methods, each one creating indices and vertices for sides of a cube. Now when I use these methods, the cube creates how it should. All 6 sides show up and its like I didnt change a thing. How can use if statements to check if the side of a cube is solid? The pseudocode from the question above shows this: if(!isSolidAt(x+1,y,z)) verticesToDraw += AddXPlusFace(x,y,z) But in my case is would be: if(!sideIsSolid) SetUpFrontFaceIndices(); My method simply takes these index and vertex values and adds them to a list indicesToDraw and verticesToDraw, as shown in the answer above

    Read the article

  • the "additional drivers" shows nothing

    - by Yasser al-Zainy
    I started using Ubuntu 32 bit last week. I love it but I recognized there was a problem with the cooling system. the fan doesn't stop and slightly loud all the time (that wasn't the case while running with windows 7). I told a friend who claimed that it should be a drivers problem. My machine is dell inspiron n5110 and the official site recommends win 7 64 bit only. there's no support for linux. (the page showing the machine drivers and system recommendation I tried to fix the problem using the "additional drivers", it opens but it shows nothing (no drivers to activate, just the help and the close buttons) is there a way to fix this?

    Read the article

  • Some mail details about Orange Mauritius

    Being an internet service provider is not easy after all for a lot of companies. Luckily, there are quite some good international operators in this world. For example Orange Mauritius aka Mauritius Telecom aka Wanadoo(?) aka MyT here in Mauritius. The local circumstances give them a quasi-monopol position on fixed lines for telephony and therefore cable-based DSL internet connectivity. So far, not bad but as usual... the details. Just for the records, I am only using the services of Orange for mobile but friends and customers are bound, eh stuck, with other services of Orange Mauritius. And usually, being the IT guy, they get in touch with me to complain about problems or to ask questions on either their ADSL / MyT connection, mail services or whatever. Most of those issues are user-related and easily to solve by tweaking the configuration of their computer a little bit but sometimes it's getting weird. Using Orange ADSL... somewhere else Now, let's imagine we are an Orange ADSL customer for ages and we are using their mail services with our very own mail address like "[email protected]". We configured our mail client like Thunderbird, Outlook Express, Outlook or Windows Mail as publicly described, and we are able to receive and send emails like a champion. No problems at all, the world is green. Did I mention that we have a laptop? Ok, let's take our movable piece of information technology and visit a friend here on the island. Not surprising, he is also customer of Orange, so we can read and answer emails. But Orange is not the online internet service provider and one day, we happen to hang out with someone that uses Emtel via WiMAX or UMTS.. And the fun starts... We can still receive and read emails from our Orange mail account and the IT world is still bright but try to send mails to someone outside the domain "@intnet.mu" or "@orange.mu". Your mail client will deny sending mail with SMTP message 5.1.0 "blah not allowed". First guess, there is problem with the mail client, maybe magically the configuration changed over-night. But no it is still working at home... So, there is for sure a problem with the guy's internet connection. At least, it is his fault not to have Orange internet services, so it can not work properly... The Orange Mail FAQ After some more frustation we finally checkout the Orange Mail FAQ to see whether this (obviously?) common problem has been described already. Sorry, but those FAQ entries are even more confusing as it is not really clear how to handle this scenario. Best of all is that most of the entries are still refering to use servers of the domain "intnet.mu". I mean Orange will disable those systems in favour of the domain "orange.mu" in the near future and does not amend their FAQs. Come on, guys! Ok, settings for POP3 are there. Hm, what about the secure version POP3S? No signs at all... Even changing your mail client to use password encryption with STARTTLS is not allowed at all. Use "bow.intnet.mu" for incoming mail... Ahhh, pretty obvious host name. I mean, at least something like pop.intnet.mu or pop3.intnet.mu would have been more accurate. Funny of all, the hostname "pop.orange.mu" is accessible to receive your mail account. Alright, checking SMTP options for authentication or other like POP-before-SMTP or whatever well-known and established mechanism to send emails are described. I guess that spotting a whale or shark in Mauritian waters would be easier. Trial and error on SMTP settings reveal that neither STARTTLS or any other connection / password encryption is available. Using SSL/TLS on SMTP only reveals that there is no service answering your request. Calling customer service So, we have to bite into the bitter apple and get in touch with Orange customer service and complain/explain them our case and ask for advice. After some hiccups, we finally manage to get hold of someone competent in mail services and we receive the golden spoon of mail configuration made by Orange Mauritius: SMTP hostname: smtpauth.intnet.mu And the world of IT is surprisingly green again. Customer satisfaction? Dear Orange Mauritius, what's the problem with this information? Are you scared of mail spammer? Why isn't there any case in your FAQs? Ok, talking about your FAQs - simply said: they are badly outdated! Configure your mail client to use server name based in the domain intnet.mu but specify your account username with orange.mu as domain part. Although, that there are servers available on the domain orange.mu after all. So, why don't you provide current information like this: POP3 server name: pop.orange.muSMTP server name: smtp.orange.muSMTP authenticated: smtpauth.orange.mu It's not difficult, is it? In my humble opinion not really and you would provide clean, consistent and up-to-date information for your customers. This would produce less frustation and so less traffic on your customer service lines. Which after all, would improve the total user experience and satisfaction level on both sides. Without knowing these facts. Now, imagine you would take your laptop abroad and have to use other internet service providers to be able to be online... Calling your customer service would be unnecessary expensive!

    Read the article

  • Best URL for cars related website? [duplicate]

    - by Claudio ??is Mulas
    This question already has an answer here: What is the best stucture of SEO friendly URL? 3 answers If this was your website, what will be the URLs for each car on sale? http://www.autoscout24.eu/Details.aspx?id=247572735&asrc=ha I'm working on a car dealership website. What should be the best URL? Consider also that the company can have more models of the same car. I'm not asking for a url scheme, there are a lot of similar questions. My question is: in a car dealership website what is the best url for a car? What are by you the best variables I've to put on the url. Brand, model, year, location, color, miles/km, etc. This website, that url, this particulary case: what will you choose for urls? (even not in the following list) audi_q5_2009.html audi_q5_2009_used.html audi_q5_2009_used.html audi_q5_2009_used_in_alcobendas.html audi_q5_2009_used/247572735.html

    Read the article

  • Using Sql Server Change Data Capture with a frequently changing schema

    - by Pete
    We are looking into enabling Sql Server Change Data Capture for a new subsystem we are building. It's not really because we need it, but we are being pushed for having a complete history traceability, and CDC would nicely solve this requirement with minimum effort on our parts. We are following an agile development process, which in this case means that we frequently make changes to the database schema, e.g. adding new columns, moving data to other columns, etc. We did a small test where we created a table, enabled CDC for that table, and then added a new column to the table. Changes to the new column is not registered in the CDC table. Is there a mechanism to update the CDC table to the new schema, and are there any best practices to how you deal with captured data when migrating the database schema?

    Read the article

  • Seminario "ABC - Activity Based Costing in Italia"

    - by claudiac.caramelli
    Martedì 5 novembre si è svolto un interessante seminario organizzato da Oracle in collaborazione con Assocontroller. Sono stati approfonditi temi riguardanti la metodologia ABC ed è stato discusso in modo oggettivo sulle problematiche, le esperienze e le evoluzioni di tale approccio. Il primo intervento, a cura di Giorgio Cinciripini (consulente e presidente di Assocontroller) ha aperto la strada alla presentazione del Prof. Alberto Bubbio, professore in economia aziendale presso l'Università Liuc. Sono stati successivamente presentati 3 case history (il caso Sandvik, Atac Patrimonio e Marazzi Group), che hanno permesso di approfondire e meglio spiegare come questa metodologia possa aiutare un'azienda a controllare i costi, per arrivare a gestirli in modo dinamico e finalizzato a seguire razionalmente l'andamento del mercato e del valore che il mercato attribuisce al prodotto o servizio che si desidera vendere. Una sala interessata e attenta agli interventi, responsi più che ottimi... Ci sono tutte le premesse per ripetere l'evento!

    Read the article

  • Having trouble compiling UnrealScript with defaultproperties

    - by Enchanter
    Have just started scripting in Unreal Script and am following the instructions of the opening chapter of a book on the subject. I have set the development tools up as described in the book such that it is now possible to compile the scripts for UDK before adding them to a level. My issue is: the very first script the book asks you to compile is the following: class AwesomeActor extends Actor placeable; defaultproperties { Begin Object Class=SpriteComponent Name = Sprite Sprite = Texture2D'EditorResources.S_NavP' End Object Components.Add(Sprite) } And when I hit F9 in the compiler I get the following error message: Error, BEGIN OBJECT: Must specify valid name for suboject/copmponent: Begin Object class=SpriteComponent name = Sprite My question: As far as I'm aware I've copied the code from the book veribatim including capital and smaller case letters but I'm getting this error and I was wondering if anyone knew why and if so how I would fix it?

    Read the article

  • Are there any formalized/mathematical theories of software testing?

    - by Erik Allik
    Googling "software testing theory" only seems to give theories in the soft sense of the word; I have not been able to find anything that would classify as a theory in the mathematical, information theoretical or some other scientific field's sense. What I'm looking for is something that formalizes what testing is, the notions used, what a test case is, the feasibility of testing something, the practicality of testing something, the extent to which something should be tested, formal definition/explanation of code coverage, etc. UPDATE: Also, I'm not sure, intuitively, about the connection between formal verification and what I asked, but there's clearly some sort of connection.

    Read the article

  • 2D object-aligned bounding-box intersection test

    - by AshleysBrain
    Hi all, I have two object-aligned bounding boxes (i.e. not axis aligned, they rotate with the object). I'd like to know if two object-aligned boxes overlap. (Edit: note - I'm using an axis-aligned bounding box test to quickly discard distant objects, so it doesn't matter if the quad routine is a little slower.) My boxes are stored as four x,y points. I've searched around for answers, but I can't make sense of the variable names and algorithms in examples to apply them to my particular case. Can someone help show me how this would be done, in a clear and simple way? Thanks. (The particular language isn't important, C-style pseudo code is OK.)

    Read the article

  • Using which technique does facebook and pininterest show images?

    - by manish
    If anybody has ever noticed that when you open a image in Facebook something like this happens:- suppose you are at your homepage on Facebook:- the URL is https://www.facebook.com/ now if you open a image it gets opened in new modal like window and URL changes to:- https://www.facebook.com/photo.php?fbid=10151125374887397&set=a.338008237396.161268.36922302396&type=1&theater As far as I know in any common case a modal overlay would have kept the url in the address bar the same , My question is how does facebook / pintrest achieve this behaviour of not re-loading the whole page but still achieving the change in the address bar. Is there any jquery or javascript plugin for this?

    Read the article

  • Subterranean IL: Generics and array covariance

    - by Simon Cooper
    Arrays in .NET are curious beasts. They are the only built-in collection types in the CLR, and SZ-arrays (single dimension, zero-indexed) have their own commands and IL syntax. One of their stranger properties is they have a kind of built-in covariance long before generic variance was added in .NET 4. However, this causes a subtle but important problem with generics. First of all, we need to briefly recap on array covariance. SZ-array covariance To demonstrate, I'll tweak the classes I introduced in my previous posts: public class IncrementableClass { public int Value; public virtual void Increment(int incrementBy) { Value += incrementBy; } } public class IncrementableClassx2 : IncrementableClass { public override void Increment(int incrementBy) { base.Increment(incrementBy); base.Increment(incrementBy); } } In the CLR, SZ-arrays of reference types are implicitly convertible to arrays of the element's supertypes, all the way up to object (note that this does not apply to value types). That is, an instance of IncrementableClassx2[] can be used wherever a IncrementableClass[] or object[] is required. When an SZ-array could be used in this fashion, a run-time type check is performed when you try to insert an object into the array to make sure you're not trying to insert an instance of IncrementableClass into an IncrementableClassx2[]. This check means that the following code will compile fine but will fail at run-time: IncrementableClass[] array = new IncrementableClassx2[1]; array[0] = new IncrementableClass(); // throws ArrayTypeMismatchException These checks are enforced by the various stelem* and ldelem* il instructions in such a way as to ensure you can't insert a IncrementableClass into a IncrementableClassx2[]. For the rest of this post, however, I'm going to concentrate on the ldelema instruction. ldelema This instruction pops the array index (int32) and array reference (O) off the stack, and pushes a pointer (&) to the corresponding array element. However, unlike the ldelem instruction, the instruction's type argument must match the run-time array type exactly. This is because, once you've got a managed pointer, you can use that pointer to both load and store values in that array element using the ldind* and stind* (load/store indirect) instructions. As the same pointer can be used for both input and output to the array, the type argument to ldelema must be invariant. At the time, this was a perfectly reasonable restriction, and maintained array type-safety within managed code. However, along came generics, and with it the constrained callvirt instruction. So, what happens when we combine array covariance and constrained callvirt? .method public static void CallIncrementArrayValue() { // IncrementableClassx2[] arr = new IncrementableClassx2[1] ldc.i4.1 newarr IncrementableClassx2 // arr[0] = new IncrementableClassx2(); dup newobj instance void IncrementableClassx2::.ctor() ldc.i4.0 stelem.ref // IncrementArrayValue<IncrementableClass>(arr, 0) // here, we're treating an IncrementableClassx2[] as IncrementableClass[] dup ldc.i4.0 call void IncrementArrayValue<class IncrementableClass>(!!0[],int32) // ... ret } .method public static void IncrementArrayValue<(IncrementableClass) T>( !!T[] arr, int32 index) { // arr[index].Increment(1) ldarg.0 ldarg.1 ldelema !!T ldc.i4.1 constrained. !!T callvirt instance void IIncrementable::Increment(int32) ret } And the result: Unhandled Exception: System.ArrayTypeMismatchException: Attempted to access an element as a type incompatible with the array. at IncrementArrayValue[T](T[] arr, Int32 index) at CallIncrementArrayValue() Hmm. We're instantiating the generic method as IncrementArrayValue<IncrementableClass>, but passing in an IncrementableClassx2[], hence the ldelema instruction is failing as it's expecting an IncrementableClass[]. On features and feature conflicts What we've got here is a conflict between existing behaviour (ldelema ensuring type safety on covariant arrays) and new behaviour (managed pointers to object references used for every constrained callvirt on generic type instances). And, although this is an edge case, there is no general workaround. The generic method could be hidden behind several layers of assemblies, wrappers and interfaces that make it a requirement to use array covariance when calling the generic method. Furthermore, this will only fail at runtime, whereas compile-time safety is what generics were designed for! The solution is the readonly. prefix instruction. This modifies the ldelema instruction to ignore the exact type check for arrays of reference types, and so it lets us take the address of array elements using a covariant type to the actual run-time type of the array: .method public static void IncrementArrayValue<(IncrementableClass) T>( !!T[] arr, int32 index) { // arr[index].Increment(1) ldarg.0 ldarg.1 readonly. ldelema !!T ldc.i4.1 constrained. !!T callvirt instance void IIncrementable::Increment(int32) ret } But what about type safety? In return for ignoring the type check, the resulting controlled mutability pointer can only be used in the following situations: As the object parameter to ldfld, ldflda, stfld, call and constrained callvirt instructions As the pointer parameter to ldobj or ldind* As the source parameter to cpobj In other words, the only operations allowed are those that read from the pointer; stind* and similar that alter the pointer itself are banned. This ensures that the array element we're pointing to won't be changed to anything untoward, and so type safety within the array is maintained. This is a typical example of the maxim that whenever you add a feature to a program, you have to consider how that feature interacts with every single one of the existing features. Although an edge case, the readonly. prefix instruction ensures that generics and array covariance work together and that compile-time type safety is maintained. Tune in next time for a look at the .ctor generic type constraint, and what it means.

    Read the article

  • Command line options style - POSIX or what?

    - by maaartinus
    Somewhere I saw a rant against java/javac allegedly using a mix of Windows and Unix style like java -classpath ... -ea ... Something IMHO, it is no mix, it's just like find works as well, isn't it? AFAIK, according to POSIX, the syntax should be like java --classpath ... --ea ... Something and -abcdef would mean specifying 6 short options at once. I wonder which version leads in general to less typing and less errors. I'm writing a small utility in Java and in no case I'm going to use Windows style /a /b since I'm interested primarily in Unix. What style should I choose?

    Read the article

  • Why fork a library for your own application?

    - by Mr. Shickadance
    Why should a programmer ever fork a library for inclusion in a widely used application? I ask this question because I was reading an article about why Chromium isn't packaged for many Linux distros like Fedora. Apparently its largely due to the fact that Google has forked a number of libraries, modified them, and included them in Chromium. This has driven up the complexity of packaging releases. There are a number of reasons why this can be a bad thing, but how strong a case can you actually make for doing so in a large widely used application such as Chromium? The original article: http://ostatic.com/blog/making-projects-easier-to-package-why-chromium-isnt-in-fedora Isn't it usually worth the effort to make slight modifications to your own program in order to use a popular and well developed library?

    Read the article

  • Solving 2D Collision Detection Issues with Relative Velocities

    - by Jengerer
    Imagine you have a situation where two objects are moving parallel to one-another and are both within range to collide with a static wall, like this: A common method used in dynamic collision detection is to loop through all objects in arbitrary order, solve for pair-wise collision detection using relative velocities, and then move the object to the nearest collision, if any. However, in this case, if the red object is checked first against the blue one, it would see that the relative velocity to the blue object is -20 m/s (and would thereby not collide this time frame). Then it would see that the red object would collide with the static wall, and the solution would be: And the red object passes through the blue one. So it appears to be a matter of choosing the right order in which you check collisions; but how can you determine which order is correct? How can this passing through of objects be avoided? Is ignoring relative velocity and considering every object as static during pair-wise checks a better idea for this reason?

    Read the article

  • Is it possible to construct a cube with fewer than 24 vertices

    - by Telanor
    I have a cube-based world like Minecraft and I'm wondering if there's a way to construct a cube with fewer than 24 vertices so I can reduce memory usage. It doesn't seem possible to me for 2 reasons: the normals wouldn't come out right and per-face textures wouldn't work. Is this the case or am I wrong? Maybe there's some fancy new DX11 tech that can help? Edit: Just to clarify, I have 2 requirements: I need surface normals for each cube face in order to do proper lighting and I need a way to address a different indexes in a texture array for each cube face

    Read the article

< Previous Page | 254 255 256 257 258 259 260 261 262 263 264 265  | Next Page >