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• How best to deal with the frustration that you encounter at the beginning of learning to code [closed]

  - by coderboy

  I am right now a newbie on the job learning to code in Cocoa . In the beginning I decided that I would try and understand everything I was doing . But right now I just feel like a clueless wizard chanting some spells . Its all just a matter of googling the right incantation . Frequently getting stuck and having to google for answers is proving to be a major demotivator for me . I know that this will get better over time but still I feel that somewhere , somehow I'm just approaching things the wrong way . I sit there stumped and then finally just look at sample code from Apple and I go Wow ! This is so logical and well structured ! . But just reading it is not going to get me to that level . So I would like to know , how do you guys approach learning something new . Do you read the whole documentation first , or do you read sample code or maybe its just about making lots of small programs first ?

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• Ubuntu not shutting down ( going to black screen ) 12.04

  - by Orrin Fox

  I am currently using a USB persistent install of ubuntu. its a simple 4GB drive with a 2.8GB partition ( casper-rw storage partition ). I setup an administrator account and set it to login automatically. I also removed ubiquity to simply use this as a go anywhere install. Heres my issue. Im logged in as my account, and I click the top right gear and select "shut down". Text pops up showing its quitting processes.. etc. and then goes to the plymouth animation. But... The screen goes black, and then it goes to the login screen. Now when im at the login screen i go into terminal ( alt+F2 ) and dont you know, im logged in as Ubuntu. so then I try the following: ubuntu@ubuntu:~$ sudo shutdown now It goes to the plymouth screen again as if its shutting down, AND the screen goes black once again but the computer has not turned off, as in the usb is still flashing the light, the fans are still on, the only thing off is the screen. Is this a bug? If not maybe i did something wrong? Perhaps its that I made an account but... if there is a work around for this please let me know. Thanks again, Fox

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• How does a segment based rendering engine work?

  - by Calmarius

  As far as I know Descent was one of the first games that featured a fully 3D environment, and it used a segment based rendering engine. Its levels are built from cubic segments (these cubes may be deformed as long as it remains convex and sides remain roughly flat). These cubes are connected by their sides. The connected sides are traversable (maybe doors or grids can be placed on these sides), while the unconnected sides are not traversable walls. So the game is played inside of this complex. Descent was software rendered and it had to be very fast, to be playable on those 10-100MHz processors of that age. Some latter levels of the game are huge and contain thousands of segments, but these levels are still rendered reasonably fast. So I think they tried to minimize the amount of cubes rendered somehow. How to choose which cubes to render for a given location? As far as I know they used a kind of portal rendering, but I couldn't find what was the technique used in this particular kind of engine. I think the fact that the levels are built from convex quadrilateral hexahedrons can be exploited.

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• SQL SERVER – What is the Maximum Relational Database Size Supported by Single Instance?

  - by Pinal Dave

  I often get asked following question? “How much data SQL Server can handle?” Every single time when I get this question – I ask back following question - “How much data your storage system can handle?” The reason I ask this question back is because in reality for enterprise systems the limitation of storage is no more an issue. The Matter of the fact most of the database is now a days limited by the size of the storage system. SQL Server is enterprise system and it is very mature product. Even though if you still want to know what is the actual limit here is the answer. SQL Server 2008R2, 2012 and 2014 have maximum capacity of 524 PB (Petabyte) in the Enterprise, BI and Standard edition. SQL Server Express has a limitation of 10 GB due to its nature. I guess, now when you look at my question it will make sense that it is all depending on the size of your storage system. I personally believe at this point of time 524 PB is quite a huge data, but we never know after 10 years when we read this blog post, we all may think what was I thinking actually. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Is it just me or is this a baffling tech interview question

  - by Matthew Patrick Cashatt

  Background I was just asked in a tech interview to write an algorithm to traverse an "object" (notice the quotes) where A is equal to B and B is equal to C and A is equal to C. That's it. That is all the information I was given. I asked the interviewer what the goal was but apparently there wasn't one, just "traverse" the "object". I don't know about anyone else, but this seems like a silly question to me. I asked again, "am I searching for a value?". Nope. Just "traverse" it. Why would I ever want to endlessly loop through this "object"?? To melt my processor maybe?? The answer according to the interviewer was that I should have written a recursive function. OK, so why not simply ask me to write a recursive function? And who would write a recursive function that never ends? My question: Is this a valid question to the rest of you and, if so, can you provide a hint as to what I might be missing? Perhaps I am thinking too hard about solving real world problems. I have been successfully coding for a long time but this tech interview process makes me feel like I don't know anything. Final Answer: CLOWN TRAVERSAL!!! (See @Matt's answer below) Thanks! Matt

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• How to Fix this specific Google "Fetch as Googlebot" error appearing on my Webmaster Tools?

  - by UXdesigner

  Good day, I'm currently finding out why I have lost all of my website's rank in google. I don't even appear in google results by the domain. But other sites do link me and they appear in the google results. I think it's all about leaving my site two months alone and finding out I had 20k in comment spam, which I completely deleted and fixed with filters and adding a new Disqus comment service. Thing is, I added my site to Google Webmaster Tools and I'm finding out several awful things. For example, when I click in Google Fetch As GoogleBot. I receive this error message below in response to my request. And I don't even know what's the real problem and how to fix it. I simply don't get it. This is what appears: Date: Wednesday, July 20, 2011 9:43:35 AM PDT Googlebot Type: Web Download Time (in milliseconds): 55 HTTP/1.1 403 Forbidden Date: Wed, 20 Jul 2011 16:43:36 GMT Server: Apache Vary: Accept-Encoding Content-Encoding: gzip Content-Length: 248 Keep-Alive: timeout=2, max=100 Connection: Keep-Alive Content-Type: text/html; charset=iso-8859-1 403 Forbidden Forbidden You don't have permission to access / on this server. Additionally, a 403 Forbidden error was encountered while trying to use an ErrorDocument to handle the request. Do you guys know anything about this problem ? I need to have Google crawl my site again. I used to have a really nice google result in the past three years. Now, there's nothing. thanks,

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• Developing professionally for both iOS, Android, web - an insight

  - by Scott Roberts

  This is not really a question on how to develop for both, I know various cross platform ways and so on. But I more want to know from developer standpoint how hard it is to basically develop iOS, Android and web apps? I am currently in my first job as a mobile/web developer. I have already developed my first iPhone/iPad app and now I have to develop the app for android because the web version I tried just didn't perform as well as needed and web databases just did not seem to make the cut. But I am not sure it's possible to be good at developing all 3 in terms of remembering all the api's etc. I wouldn't say I have an issue with the programming languages just how to use the api's for the various platforms. Also, all the other languages I look at, in my spare time, just feel like I am spreading myself to thin. Is it feasible for one person to be developing ios, android and web apps? Should I think about reducing it to iOS and web based apps? I develop everything by myself, so I have no one to discuss what the best solutions are for everything and I am just trying to workout as I go along. So any cross platform developers out there? Do companies have different teams for different platforms? Any insight would just help me get my head together. Hopefully this question makes sense.

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• Why does my browser take me to Scour.com? (redirect virus)

  - by Paula DiTallo

  The "scour" or Rootkit.Win32.TDSS virus has a long history which can be found here: http://en.wikipedia.org/wiki/Scour Here is the primary symptom: after searching for something in your web browser using google, one of the results that you click on redirects you to scour.com. If you've executed ClamWin, Malwarebytes, McAfee, Norton, etc. to find and isolate the virus without any luck--this isn't really a surprise, since this virus attaches to existing system drivers. I only know of one reliable package that will remove this without ill effects--like adding new spyware. This package is called TDSSKiller. I have seen multiple websites that claim to have this software available, but the one that I know is reliable is located here: http://support.kaspersky.com/viruses/solutions?qid=208280684 Once you go to Kaspersky's tech support site, the TDSSKiller zip file is available for downloading. When you execute this software, you will be able to "cure" or repair the infected driver. Remember to jot down the name of the driver for future reference--should you need to reinstall the driver from a "same-as" working computer, or your install disk if the repair is ineffective. The driver that happened to get infected on my computer was the tcpip.sys driver. This caused my win sockets to loose their ip addresses. In most other instances, less critical drivers such as HDAudBus.sys are infected. In my case, I was not through correcting my computer problems until I corrected the broken WinSock issue and loaded an earlier version of the tcpip.sys driver from: C:\WINDOWS\ServicePackFiles\i386 which I placed in: C:\WINDOWS\system32\drivers Don't forget to reboot your computer after your repair! Once you download TDSSKiller and cure/repair your infected driver(s), the redirect on google searches should disappear .

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• How do I capture a 10053 trace for a SQL statement called in a PL/SQL package?

  - by Maria Colgan

  Traditionally if you wanted to capture an Optimizer trace (10053) for a SQL statement you would issue an alter session command to switch on a 10053 trace for that entire session, and then issue the SQL statement you wanted to capture the trace for. Once the statement completed you would exit the session to disable the trace. You would then look in the USER_DUMP_DEST directory for the trace file. But what if the SQL statement you were interested  in was actually called as part of a PL/SQL package? Oracle Database 11g, introduced a new diagnostic events infrastructure, which greatly simplifies the task of generating a 10053 trace for a specific SQL statement in a PL/SQL package. All you will need to know is the SQL_ID for the statement you are interested in. Instead of turning on the trace event for the entire session you can now switch it on for a specific SQL ID. Oracle will then capture a 10053 trace for the corresponding SQL statement when it is issued in that session. Remember the SQL statement still has to be hard parsed for the 10053 trace to be generated.  Let's begin our example by creating a PL/SQL package called 'cal_total_sales'. The SQL statement we are interested in is the same as the one in our original example, SELECT SUM(AMOUNT_SOLD) FROM SALES WHERE CUST_ID = :B1. We need to know the SQL_ID of this SQL statement to set up the trace, and we can find in V$SQL. We now have everything we need to generate the trace. Finally  you would look in the USER_DUMP_DEST directory for the trace file with the name you specified. Maria Colgan+

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• Trace Mobile Service Serving 20,000 + Request Per Month

  - by Gopinath

  We introduced Trace Mobile Service in April 2010 and we are glad to announce that now the service is processing 20000 + per month. After a long time today I looked at the statistics and overwhelmed to see the number of trace requests processing by the service as 24282, 23781 and 18475 in the months of January 11, December 10 and November 10 respectively. Also I’m glad to announce that this service is contributes close to 10% of our revenues. Here is a table that provide stats for the past 7 months For those who don’t know about this service It is a tiny, yet very useful service for tracing information of Indian mobile phones. Usage of this service is very simple: enter any Indian mobile phone number and it will instantaneously let you know the location and the service provider of the mobile phone. Visit Trace Mobile Service or read Introducing “Trace Mobile Information” Service for more details This article titled,Trace Mobile Service Serving 20,000 + Request Per Month, was originally published at Tech Dreams. Grab our rss feed or fan us on Facebook to get updates from us.

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• Good Freelance models for web developers

  - by Matthew Underwood

  I am a web developer with four years of experience in PHP, MYSQL and experience in Javascript etc. One day I hope to develop a freelance career in web development. Areas of freelance that I am thinking of going towards includes Wordpress, Magento development along with bespoke applications. I am also thinking of doing some consultancy work for clients and businesses when I build up some more experience and technical knowledge. I want to offer a web development service to potential clients that plays on my strengths in what I know but most importantly has a market. Web development can cover so many subjects that its difficult to pick out the areas that have demand. I am also curious to find out if web developers offer services that bring in a monthly income e.g application maintenance or database maintenance? Is there a market for certain areas like WordPress plugins or bespoke applications? Are there certain things to avoid because of work duration, unrealistic client expectations or the fact that its impossible to find a market for it? As professional and experienced freelance web developers have you learned some important do's and don'ts? Is there certain services that the majority of web developers offer because its in high demand? This is the one area of web development freelancing that I cant get my head around. I know there is never a definitive answer but there must be some good practises and general consensus on this subject. Web designers design websites they offer a lump sum and get paid monthly sometimes to add new content, PPC and SEO consultants market sites to the top this will involve monthly payments, web development doesn’t seem so clear cut.

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• Future of WPF and free controls ? [closed]

  - by Justin

  I am willing to work on a personal project that I would like to release publicly. I am working with Silverlight and have experience with XAML, as it is my full-time job. It is enjoyably for me to create UIs in Blend and XAML. I am also a big fan of C# language. I don't know what I would do without LINQ now. Anyways, I was looking at using WPF for my personal project. It seems that a lot of the controls out on the web are pay for items. The only place I have found to have a significant number of free controls is the WPF extended framework on codeplex. I want to make a financial application and need a powerful datagrid type of control that will allow me to enter transaction data. I haven't found such control for free in the net. It doesn't seem like there is much free community libraries/controls out there for Microsoft products. So, I was wondering if WPF would be the right way for me to go. I couldn't find any information on WPF usage in Windows 8, which coming very soon. I don't know Microsoft's plans for this technology. Would it be a better idea to use something different for the UI instead of WPF?

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• Great Blog Comments

  - by Paul Sorensen

  Just a quick note to let you know that in the interest of keeping the most useful content available here on the Oracle Certification Blog, we do moderate the comments. We welcome (and encourage dialog, questions, comments, etc) here on the topics at hand. We'll never 'censor' out a comment just because we don't like it - in fact, this is how we often learn ways in which we can do better. But of course we will filter out the typical list like anyone else: crude/offensive remarks, foul language, reference to illegal activity, etc. We will also often redirect any customer-service type inquiries to [email protected] where they can best be handled.Also, if you have a question of a general nature, please research it on the Oracle Certification website first. We often won't respond to questions asking such as "tell me how to get 11g ocp", as we've already made sure that you have that kind of information available. Now if we've inadvertently 'hidden' something on our site (gulp), then fair enough - please let us know that you're having a hard time finding it and we'll be sure to try and "unbury it" ;-)Additionally, you may have more of an 'opinion' type question, such as "should I do 'x' certification or 'y' certification." For these, we highly recommend checking on the Oracle Technology Network (OTN) Certification Forum, where you can engage in peer-to-peer discussions, share techniques, advice and best practices with others in the field.In the meantime, please continue to share your thoughts, ideas, opinions, tech tips etc - we look forward to seeing them and passing them wherever we can!QUICK LINKS:Oracle Certification WebsiteEmail - Customer ServiceOracle Technology Network (OTN) Certification Forum

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• How to Detect Sprites in a SpriteSheet?

  - by IAE

  I'm currently writing a Sprite Sheet Unpacker such as Alferds Spritesheet Unpacker. Now, before this is sent to gamedev, this isn't necessarily about games. I would like to know how to detect a sprite within a spriitesheet, or more abstactly, a shape inside of an image. Given this sprite sheet: I want to detect and extract all individual sprites. I've followed the algorithm detailed in Alferd's Blog Post which goes like: Determine predominant color and dub it the BackgroundColor Iterate over each pixel and check ColorAtXY == BackgroundColor If false, we've found a sprite. Keep going right until we find a BackgroundColor again, backtrack one, go down and repeat until a BackgroundColor is reached. Create a box from location to ending location. Repeat this until all sprites are boxed up. Combined overlapping boxes (or within a very short distance) The resulting non-overlapping boxes should contain the sprite. This implementation is fine, especially for small sprite sheets. However, I find the performance too poor for larger sprite sheets and I would like to know what algorithms or techniques can be leveraged to increase the finding of sprites. A second implementation I considered, but have not tested yet, is to find the first pixel, then use a backtracking algorithm to find every connected pixel. This should find a contiguous sprite (breaks down if the sprite is something like an explosion where particles are no longer part of the main sprite). The cool thing is that I can immediately remove a detected sprite from the sprite sheet. Any other suggestions?

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• When to use http status code 404

  - by Sybiam

  I am working on a project and after arguing with people at work for about more than a hour. I decided to know what people on stack-exchange might say. We're writing an API for a system, there is a query that should return a tree of Organization or a tree of Goals. The tree of Organization is the organization in which the user is present, In other words, this tree should always exists. In the organization, a tree of goal should be always present. (that's where the argument started). In case where the tree doesn't exist, my co-worker decided that it would be right to answer response with status code 200. And then started asking me to fix my code because the application was falling apart when there is no tree. I'll try to spare flames and fury. I suggested to raise a 404 error when there is no tree. It would at least let me know that something is wrong. When using 200, I have to add special check to my response in the success callback to handle errors. I'm expecting to receive an object, but I may actually receive an empty response because nothing is found. It sounds totally fair to mark the response as a 404. And then war started and I got the message that I didn't understand HTTP status code schema. So I'm here and asking what's wrong with 404 in this case? I even got the argument "It found nothing, so it's right to return 200". I believe that it's wrong since the tree should be always present. If we found nothing and we are expecting something, it should be a 404. Extra Also, I believe the best answer to the problem is to create default objects when organizations are created, having no tree shouldn't be a valid case and should be seen as an undefined behavior. There is no way an account can be used without both trees. For that reasons, they should be always present.

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• How to run the pixel shader effcet??

  - by Yashwinder

  Below stated is the code for my pixel shader which I am rendering after the vertex shader. I have set the wordViewProjection matrix in my program but I don't know to set the progress variable i.e in my pixel shader file which will make the image displayed by the help of a quad to give out transition effect. Here is the code for my pixel shader program::: As my pixel shader is giving a static effect and now I want to use it to give some effect. So for this I have to add a progress variable in my pixel shader and initialize to the Constant table function i.e constantTable.SetValue(D3DDevice,"progress",progress ); I am having the problem in using this function for progress in my program. Anybody know how to set this variable in my program. And my new pixel Shader code is float progress : register(C0); sampler2D implicitInput : register(s0); sampler2D oldInput : register(s1); struct VS_OUTPUT { float4 Position : POSITION; float4 Color : COLOR0; float2 UV : TEXCOORD 0; }; float4 Blinds(float2 uv) { if(frac(uv.y * 5) < progress) { return tex2D(implicitInput, uv); } else { return tex2D(oldInput, uv); } } // Pixel Shader { return Blinds(input.UV); }

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• Drawing particles as a smooth blob

  - by Nömmik

  I'm new to game/graphics development and I'm playing around with particles (in 2D). I want to draw particles close to each other as a blob, just as liquid/water. I do not want to draw big circles overlapping as the blob won't be smooth (and too big). I don't really know physics but I assume what I want is something looking similar to surface tension. I haven't been able to find anything on stackexchange or on Google (maybe I do not know the correct keywords?). So far I have found two possible solutions, but I am unable to find any concrete information about algorithms. One of them is to calculate the concave hull of particles I consider being a blob. I can calculate the blob by creating an equivalence class (on the relation "close to each other"). Strangely enough I haven't been able to find any algorithm explaining how to calculate the concave hull. Many posts (and among stackexchange) links to libraries or commercial products that do this (I need libraries to work in C#), but never any algorithm. Also this solution might have a problem with a circle of particles, which would not detect the empty space in the middle. While researching concave hull I stumbled upon something called alpha shapes. Which seems to be exactly what I want to do, however just as with concave hull I haven't found any source explaining how they actually work. I have found some presentation materials but not enough to go on. It's like a big secret everyone knows except me :-/ After calculating the concave hull or alpha shape I want to make it a Bézier curve to make it smooth and nice. Although I do find my approach a bit too complex, maybe I am trying to solve this the wrong way? If you can either suggest any other solution to my problem, or explain the pieces I am missing I would be very happy and grateful :-) Thanks.

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• early audio offset in Audacity and VLC, but not Banshee

  - by reek

  I'm editing audio files with speech in Audacity, marking particular types of speech. I just noticed that files edited in Windows have different intervals marked than files edited in Ubuntu. After testing and confirming this error, it seems that the audio playback in Ubuntu clips the sound too early from the end (early offset), which causes the person doing the editing to mark the interval wrongly. Interestingly, the error appears in Audacity and VLC (which I sometimes use for playback), but NOT Banshee. Since both Audacity and VLC have this problem, I assume it is not application-specific. I don't know why Banshee handles this without problem though... Are there any ALSA or Pulseaudio settings that are likely to cause this problem (I know very little about either)? The task itself does not appear to consume large amounts of resources, but I am on an old laptop, so here are my specs: Ubuntu 11.10. Dell XPS m1210 1.6 GHz Intel Core, 2 x 512 Mb 667 MHz RAM, Audio device: Intel Corporation N10/ICH 7 Family High Definition Audio Controller (rev 01). Audacity settings: Device Interface: ALSA (cannot select anything else)

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• How to learn the math behind the code?

  - by Solomon Wise

  I am a 12 year old who has recently gotten into programming. (Although I know that the number of books you have read does not determine your programming competency or ability, just to paint a "map" of where I am in terms of the content I know...) I've finished the books: Python 3 For Absolute Beginners Pro Python Python Standard Library by Example Beautiful Code Agile Web Development With Rails and am about halfway into Programming Ruby. I have written many small programs (One that finds which files have been updated and deleted in a directory, one that compares multiple players' fantasy baseball value, and some text based games, and many more). Obviously, as I'm not some sort of child prodigy, I can't take a formal Computer Science course until high school. I really want to learn computer science to increase my knowledge about the code, and the how the code runs. I've really become interested in the math part after reading the source code for Python's random module. Is there a place where I can learn CS, or programming math online for free, at a level that would be at least partially understandable to a person my age?

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• Windows CE and the Compact Framework are dead?

  - by Valter Minute

  This is one of the question that I’ve been asked more and more frequently at my public speeches and each time I meet customers. The announcement of the new Windows Phone 7 platform and the release of Visual Studio 2010 generated a bit of confusion around Windows CE and some of the technologies it supports. Windows CE is still alive and a lot of good programmers are working on the new releases (I had a chance to know some of them during the MVP summit in February). Here’s a blog post from Olivier Bloch that describes the situation and provides some good news about the OS: http://blogs.msdn.com/obloch/archive/2010/05/03/windows-ce-is-not-dead.aspx As you can read here, Windows Phone 7 keeps its “roots” inside Windows CE. Regarding the .NET Compact Framework, this article from the excellent “I know the answer (it’s 42)” blog from Abhinaba (it seems that we share a passion for photography, Douglas Adams and embedded development), explains that the .NET CF is the foundation of XNA and Silverlight implementation on the WP7 platform: http://blogs.msdn.com/abhinaba/archive/2010/03/18/what-is-netcf.aspx So Windows CE is here to stay, powering one of the most interesting smart phone platforms and ready to power also your devices. Add those blogs to your RSS reader list and stay tuned for more good news about CE and the Compact Framework!

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• Developing a mobile application, how to show help if it contains too much data?

  - by MobileDev123

  I am developing a mobile application which has many functionality, and I am pretty sure that the design will confuse the user about how to use some functionality so we decided to include some help as we can see them regularly in desktop applications, but later we found that the help text is too long. We don't think that one screen is enough to describe what a user can do. Moreover the project itself is subjected to evolve based on beta stage and user reports. After a lot of thinking and meetings we have decided three options to show the users what they can do. Create the website or blog, so we can let the users know what they can do with this application, the advantage is that it can provide us a good source of marketing, but for that they have to access the site while most part of the application can be used while being offline in earlier versions. Create a section in the application called demos to show the same thing locally, but we are afraid that it will increase the size, that we think can be avoided (and we are planning to avoid if there is any option) Show popups, but we discarded this thinking that pop ups annoys user no matter what the platform is. I want to know from community that which option will you choose, we are also open to accept other ideas if you have.

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• An Interesting Perspective on Oracle's Mobile Strategy

  - by Carlos Chang

  Oracle’s well known for being an acquisitive company. On average, I think we acquire about 1 company a month. (don’t quote me, I didn't run the numbers)  With all the excitement around mobile, mobile and wait for it… mobile, well, you know...what' s up with that? Well, just to be clear and quote Schultz from Hogan's Heroes "I know nothing! Nothing! "  But I did recently run across this blog by Kevin Benedict over at mobileenterprisestrategies.com covering this very topic, Oracle Mobility Emerges Prepared for the Future,  a little (fair use) snippet here:"History, however, may reward Oracle's patience.  While veteran mobile platform vendors (including SAP) have struggled to keep up with the fast changing market, R&D investment requirements, the fickle preferences of mobile developers, and the emergence of cloud-based mobile services, Oracle has kept their focus on supporting mobile developers with integration services and tools that extend their solutions out to mobile apps.”It’s an interesting read, and I would encourage you to check it out here.   BTW, if you’re a Twitter user, follow our new account @OracleMobile To the first ten thousand followers, I bequeath you my sincere virtual thanks and gratitude. :)  For the dedicated mobile blog, go to blogs.oracle.com/mobile.

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• Hardware settings reviewing

  - by dino99

  Get some hardware related errors logged into dmesg: oem@dub:~$ dmesg | grep ata10 [ 1.007989] ata10: PATA max UDMA/133 cmd 0xa800 ctl 0xa480 bmdma 0xa408 irq 18 [ 1.691664] ata10: prereset failed (errno=-19) [ 1.691670] ata10: reset failed, giving up oem@dub:~$ dmesg | grep ata2 [ 0.990290] ata2: SATA max UDMA/133 abar m1024@0xfebfb800 port 0xfebfb980 irq 45 [ 1.688011] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 300) [ 1.688055] ata2.00: unsupported device, disabling [ 1.688057] ata2.00: disabled As I understand, its related to my old Seagate SATA HDD, and the PATA CDROM. These errors are quite new, so I feel that their settings (dma, write-cache, ...) have been modified by some upgrades. I've already used hdparm to set write-cache off on the HDDs. But it seems like I need to review some other setting(s) too. With oldest distro it was easy to know about the hardware settings, but now on Quantal/Precise its deeply hidden for the average user. So i would like to know how to view/modify these settings. About the CDROM reader, the problem is different: - the system don't identify it with an UUID; but only with ATAPI or by-id oem@dub:~$ dmesg|grep 'ATAPI' [ 1.308611] ata3.00: ATAPI: TSSTcorp CDDVDW SH-S203D, SB00, max UDMA/100 oem@dub:~$ ls -l /dev/disk/by-id/ ...... lrwxrwxrwx 1 root root 9 oct. 1 06:42 ata-TSSTcorp_CDDVDW_SH-S203D -> ../../sr0 .....

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• Switch vs Polymorphism when dealing with model and view

  - by Raphael Oliveira

  I can't figure out a better solution to my problem. I have a view controller that presents a list of elements. Those elements are models that can be an instance of B, C, D, etc and inherit from A. So in that view controller, each item should go to a different screen of the application and pass some data when the user select one of them. The two alternatives that comes to my mind are (please ignore the syntax, it is not a specific language) 1) switch (I know that sucks) //inside the view controller void onClickItem(int index) { A a = items.get(index); switch(a.type) { case b: B b = (B)a; go to screen X; x.v1 = b.v1; // fill X with b data x.v2 = b.v2; case c: go to screen Y; etc... } } 2) polymorphism //inside the view controller void onClickItem(int index) { A a = items.get(index); Screen s = new (a.getDestinationScreen()); //ignore the syntax s.v1 = a.v1; // fill s with information about A s.v2 = a.v2; show(s); } //inside B Class getDestinationScreen(void) { return Class(X); } //inside C Class getDestinationScreen(void) { return Class(Y); } My problem with solution 2 is that since B, C, D, etc are models, they shouldn't know about view related stuff. Or should they in that case?

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• What's the relationship between meta-circular interpreters, virtual machines and increased performance?

  - by Gomi

  I've read about meta-circular interpreters on the web (including SICP) and I've looked into the code of some implementations (such as PyPy and Narcissus). I've read quite a bit about two languages which made great use of metacircular evaluation, Lisp and Smalltalk. As far as I understood Lisp was the first self-hosting compiler and Smalltalk had the first "true" JIT implementation. One thing I've not fully understood is how can those interpreters/compilers achieve so good performance or, in other words, why is PyPy faster than CPython? Is it because of reflection? And also, my Smalltalk research led me to believe that there's a relationship between JIT, virtual machines and reflection. Virtual Machines such as the JVM and CLR allow a great deal of type introspection and I believe they make great use it in Just-in-Time (and AOT, I suppose?) compilation. But as far as I know, Virtual Machines are kind of like CPUs, in that they have a basic instruction set. Are Virtual Machines efficient because they include type and reference information, which would allow language-agnostic reflection? I ask this because many both interpreted and compiled languages are now using bytecode as a target (LLVM, Parrot, YARV, CPython) and traditional VMs like JVM and CLR have gained incredible boosts in performance. I've been told that it's about JIT, but as far as I know JIT is nothing new since Smalltalk and Sun's own Self have been doing it before Java. I don't remember VMs performing particularly well in the past, there weren't many non-academic ones outside of JVM and .NET and their performance was definitely not as good as it is now (I wish I could source this claim but I speak from personal experience). Then all of a sudden, in the late 2000s something changed and a lot of VMs started to pop up even for established languages, and with very good performance. Was something discovered about the JIT implementation that allowed pretty much every modern VM to skyrocket in performance? A paper or a book maybe?

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