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• How to define type-specific scripts when using a 'type object' programming pattern?

  - by Erik

  I am in the process of creating a game engine written in C++, using the C/C++ SQLite interface to achieve a 'type object' pattern. The process is largely similar to what is outlined here (Thank you Bob Nystrom for the great resource!). I have a generally defined Entity class that when a new object is created, data is taken from a SQLite database and then is pushed back into a pointer vector, which is then iterated through, calling update() for each object. All the ints, floats, strings are loaded in fine, but the script() member of Entity is proving an issue. It's not much fun having a bunch of stationary objects laying around my gameworld. The only solutions I've come up with so far are: Create a monolithic EntityScript class with member functions encompassing all game AI and then calling the corresponding script when iterating through the Entity vector. (Not ideal) Create bindings between C++ and a scripting language. This would seem to get the job done, but it feels like implementing this (given the potential memory overhead) and learning a new language is overkill for a small team (2-3 people) that know the entirety of the existing game engine. Can you suggest any possible alternatives? My ideal situation would be that to add content to the game, one would simply add a script file to the appropriate directory and append the SQLite database with all the object data. All that is required is to have a variety of integers and floats passed between both the engine and the script file.

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• Ubuntu doesn't load, can't even open a terminal to type commands, even after boot repair

  - by Sky

  When I start Ubuntu I only get my desktop picture and am unable to open a terminal to type any commands. When I try a Guest session all I get is a red Ubuntu backdrop, nothing else. I tried boot repair but no improvement. Summary information following boot repair: http://paste.ubuntu.com/8109809/ I can paste some of it here if someone can tell me which part of it is relevant. This all occurred after I tried to remove compizconfig (which I might not have completed), because it's been using up my CPU (running at 50-60% with compiz at the top in System monitor. My laptop has been running very slow since installing Ubuntu so I've been trying to fix that, also website videos play slow and the startup of Ubuntu has been faulty. I also installed a proprietory Nvidia driver (304) before this launcher issue occurred, in an effort to fix my video problem (didn't help anything). Laptop is Dell 620m with Intel Core 2; 1.83GHz, 2 GB RAM, Ubuntu 14.04 (new to Linux); 66GB Ubuntu partition. Everything works fine on the small XP partition of my laptop, but I've moved all my files to the larger Ubuntu portion. I wanted to try some answers I found to similar questions but they all seem to involve commands in a terminal and I can't open a terminal. How can I get the launcher back, along with access to my programmes etc? Thank you for any help.

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• Using runtime generic type reflection to build a smarter DAO

  - by kerry

  Have you ever wished you could get the runtime type of your generic class? I wonder why they didn’t put this in the language. It is possible, however, with reflection: Consider a data access object (DAO) (note: I had to use brackets b/c the arrows were messing with wordpress): public interface Identifiable { public Long getId(); } public interface Dao { public T findById(Long id); public void save(T obj); public void delete(T obj); } Using reflection, we can create a DAO implementation base class, HibernateDao, that will work for any object: import java.lang.reflect.Field; import java.lang.reflect.ParameterizedType; public class HibernateDao implements Dao { private final Class clazz; public HibernateDao(Session session) { // the magic ParameterizedType parameterizedType = (ParameterizedType) clazz.getGenericSuperclass(); return (Class) parameterizedType.getActualTypeArguments()[0]; } public T findById(Long id) { return session.get(clazz, id); } public void save(T obj) { session.saveOrUpdate(obj); } public void delete(T obj) { session.delete(obj); } } Then, all we have to do is extend from the class: public class BookDaoHibernateImpl extends HibernateDao { }

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• What type of pattern would be used in this case

  - by Admiral Kunkka

  I want to know how to tackle this type of scenario. We are building a person's background, from scratch, and I want to know, conceptually, how to proceed with a secure object pattern in both design and execution... I've been reading on Factory patterns, Model-View-Controller types, Dependency injection, Singleton approaches... and I can't seem to grasp or 'fit' these types of designs decisions into what I'm trying to do.. First and foremost, I started with having a big jack-of-all-trades class, then I read some more, and some tips were to make sure your classes only have a single purpose.. which makes sense and I started breaking down certain things into other classes. Okay, cool. Now I'm looking at dependency injection and kind of didn't really know what's going on. Example/insight of what kind of heirarchy I need to accomplish... class Person needs to access and build from a multitude of different classes. class Culture needs to access a sub-class for culture benefits class Social needs to access class Culture, and other sub-classes class Birth needs to access Social, Culture, and other sub-classes class Childhood/Adolescence/Adulthood need to access everything. Also, depending on different rolls, this class heirarchy needs to create multiple people as well, such as Family, and their backgrounds using some, if not all, of these same classes. Think of it as a people generator, all random, with backgrounds and things that happen to them. Ageing, death of loved ones, military careers, e.t.c. Most of the generation is done randomly, making calls to a mt_rand function to pick from most of the selections inside the classes, guaranteeing the data to be absolutely random. I have most of the bulk-data down, and was looking for some insight from fellow programmers, what do you think?

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  - by skhtyu skhtyu

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• SQL SERVER – Best Reference – Wait Type – Day 27 of 28

  - by pinaldave

  I have great learning experience to write my article series on Extended Event. This was truly learning experience where I have learned way more than I would have learned otherwise. Besides my blog series there was excellent quality reference available on internet which one can use to learn this subject further. Here is the list of resources (in no particular order): sys.dm_os_wait_stats (Book OnLine) – This is excellent beginning point and official documentations on the wait types description. SQL Server Best Practices Article by Tom Davidson – I think this document goes without saying the BEST reference available on this subject. Performance Tuning with Wait Statistics by Joe Sack – One of the best slide deck available on this subject. It covers many real world scenarios. Wait statistics, or please tell me where it hurts by Paul Randal – Notes from real world from SQL Server Skilled Master Paul Randal. The SQL Server Wait Type Repository… by Bob Ward – A thorough article on wait types and its resolution. A MUST read. Tracking Session and Statement Level Waits by by Jonathan Kehayias – A unique article on the subject where wait stats and extended events are together. Wait Stats Introductory References By Jimmy May – Excellent collection of the reference links. Great Resource On SQL Server Wait Types by Glenn Berry – A perfect DMV to find top wait stats. Performance Blog by Idera – In depth article on top of the wait statistics in community. I have listed all the reference I have found in no particular order. If I have missed any good reference, please leave a comment and I will add the reference in the list. Read all the post in the Wait Types and Queue series. Reference: Pinal Dave (http://blog.SQLAuthority.com) Tracking Session and Statement Level Waits Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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• XNA extending an existing Content type

  - by Maarten

  We are doing a game in XNA that reacts to music. We need to do some offline processing of the music data and therefore we need a custom type containing the Song and some additional data: // Project AudioGameLibrary namespace AudioGameLibrary { public class GameTrack { public Song Song; public string Extra; } } We've added a Content Pipeline extension: // Project GameTrackProcessor namespace GameTrackProcessor { [ContentSerializerRuntimeType("AudioGameLibrary.GameTrack, AudioGameLibrary")] public class GameTrackContent { public SongContent SongContent; public string Extra; } [ContentProcessor(DisplayName = "GameTrack Processor")] public class GameTrackProcessor : ContentProcessor<AudioContent, GameTrackContent> { public GameTrackProcessor(){} public override GameTrackContent Process(AudioContent input, ContentProcessorContext context) { return new GameTrackContent() { SongContent = new SongProcessor().Process(input, context), Extra = "Some extra data" // Here we can do our processing on 'input' }; } } } Both the Library and the Pipeline extension are added to the Game Solution and references are also added. When trying to use this extension to load "gametrack.mp3" we run into problems however: // Project AudioGame protected override void LoadContent() { AudioGameLibrary.GameTrack gameTrack = Content.Load<AudioGameLibrary.GameTrack>("gametrack"); MediaPlayer.Play(gameTrack.Song); } The error message: Error loading "gametrack". File contains Microsoft.Xna.Framework.Media.Song but trying to load as AudioGameLibrary.GameTrack. AudioGame contains references to both AudioGameLibrary and GameTrackProcessor. Are we maybe missing other references? EDIT Selecting the correct content processor helped, it loads the audio file correctly. However, when I try to process some data, e.g: public override GameTrackContent Process(AudioContent input, ContentProcessorContext context) { int count = input.Data.Count; // With this commented out it works fine return new GameTrackContent() { SongContent = new SongProcessor().Process(input, context) }; } It crashes with the following error: Managed Debugging Assistant 'PInvokeStackImbalance' has detected a problem in 'C:\Users\Maarten\Documents\Visual Studio 2010\Projects\AudioGame\DebugPipeline\bin\Debug\DebugPipeline.exe'. Additional Information: A call to PInvoke function 'Microsoft.Xna.Framework.Content.Pipeline!Microsoft.Xna.Framework.Content.Pipeline.UnsafeNativeMethods+AudioHelper::OpenAudioFile' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature. Information from logger right before crash: Using "BuildContent" task from assembly "Microsoft.Xna.Framework.Content.Pipel ine, Version=4.0.0.0, Culture=neutral, PublicKeyToken=842cf8be1de50553". Task "BuildContent" Building gametrack.mp3 -> bin\x86\Debug\Content\gametrack.xnb Rebuilding because asset is new Importing gametrack.mp3 with Microsoft.Xna.Framework.Content.Pipeline.Mp3Imp orter Im experiencing exactly this: http://forums.create.msdn.com/forums/t/75996.aspx

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• Inheritance of list-style-type property in Firefox (bug in Firebug?)

  - by Marcel Korpel

  Let's have a look at some comments on a page generated by Wordpress (it's not a site I maintain, I'm just wondering what's going on here). As these pages might disappear in the near future, I've put some screenshots online. Here's what I saw: Obviously, the list-item markers shouldn't be there. So I decided to look at the source using Firebug. As you can see, Firebug claims that the list-style property (containing none) is inherited from ol.commentlist. But if that's the case, why are the circle and the square visible? When checking the computed style, Firebug shows the list-style-types correctly. What's the correct behaviour? I just did a quick check in Chromium, whose Web Inspector gave a better view of reality (the list item markers were also displayed in this browser): According to WebKit, list-style of ol.commentlist isn't inherited, only the default value of list-style-type from the rendering engine. So, we may conclude that the output of both browsers is correct and that Firefox (Firebug) shows an incorrect representation of inherited styles. What does the CSS specification say? Inheritance will transfer the list-style values from OL and UL elements to LI elements. This is the recommended way to specify list style information. Not much about the inheritance of ol properties to uls. Is Firebug wrong in this respect? BTW, I managed to let the markers disappear by just changing line 312 of style.css to ol.commentlist, li.commentlist, ul.children { When also explicitly defining the list-style of ul.children to none, the markers are not painted. You can have a look at screenshots of Firebug and WebKit's Web Inspector in this case, if you like.

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• Liskov principle: violation by type-hinting

  - by Elias Van Ootegem

  According to the Liskov principle, a construction like the one below is invalid, as it strengthens a pre-condition. I know the example is pointless/nonsense, but when I last asked a question like this, and used a more elaborate code sample, it seemed to distract people too much from the actual question. //Data models abstract class Argument { protected $value = null; public function getValue() { return $this->value; } abstract public function setValue($val); } class Numeric extends Argument { public function setValue($val) { $this->value = $val + 0;//coerce to number return $this; } } //used here: abstract class Output { public function printValue(Argument $arg) { echo $this->format($arg); return $this; } abstract public function format(Argument $arg); } class OutputNumeric extends Output { public function format(Numeric $arg)//<-- VIOLATION! { $format = is_float($arg->getValue()) ? '%.3f' : '%d'; return sprintf($format, $arg->getValue()); } } My question is this: Why would this kind of "violation" be considered harmful? So much so that some languages, like the one I used in this example (PHP), don't even allow this? I'm not allowed to strengthen the type-hint of an abstract method but, by overriding the printValue method, I am allowed to write: class OutputNumeric extends Output { final public function printValue(Numeric $arg) { echo $this->format($arg); } public function format(Argument $arg) { $format = is_float($arg->getValue()) ? '%.3f' : '%d'; return sprintf($format, $arg->getValue()); } } But this would imply repeating myself for each and every child of Output, and makes my objects harder to reuse. I understand why the Liskov principle exists, don't get me wrong, but I find it somewhat difficult to fathom why the signature of an abstract method in an abstract class has to be adhered to so much stricter than a non-abstract method. Could someone explain to me why I'm not allowed to hind at a child class, in a child class? The way I see it, the child class OutputNumeric is a specific use-case of Output, and thus might need a specific instance of Argument, namely Numeric. Is it really so wrong of me to write code like this?

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• How to detect browser type and version from ADF Faces

  - by Frank Nimphius

  Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Sometimes ADF applications need to know about the user browser type and version. For this, assuming you need this information in Java, you can use the Trinidad RequestContext object. You could also use the AdfFacesContext object for the same, but since the ADF Faces Agent class is marked as deprecated, using the equivalent Trinidad classes is the better choice. The source code below prints the user browser information to the Oracle JDeveloper message window import org.apache.myfaces.trinidad.context.Agent; import org.apache.myfaces.trinidad.context.RequestContext; … RequestContext requestCtx = RequestContext.getCurrentInstance(); Agent agent = requestCtx.getAgent(); String version = agent.getAgentVersion(); String browser = agent.getAgentName(); String platform = agent.getPlatformName(); String platformVersion = agent.getPlatformVersion(); System.out.println("=================="); System.out.println("Your browser information: "); System.out.println("Browser: "+browser); System.out.println("Browser Version : "+version); System.out.println("Browser Platform: "+platform); System.out.println("Browser Platform Version: "+platformVersion); System.out.println("==================");

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• Why am I getting an error when return TRUE/FALSE to type Boolean?

  - by phill

  I wrote the following code: import java.lang.*; import DB.*; private Boolean validateInvoice(String i) { int count = 0; try { //check how many rowsets ResultSet c = connection.DBquery("select count(*) from Invce i,cust c where tranid like '"+i+"' and i.key = c.key "); while (c.next()) { System.out.println("rowcount : " + c.getInt(1)); count = c.getInt(1); } if (count > 0 ) { return TRUE; } else { return FALSE; } //end if } catch(Exception e){e.printStackTrace();return FALSE;} } The errors I'm getting are: i.java:195: cannot find symbol symbol : variable TRUE location: class changei.iTable return TRUE; i.java:197: cannot find symbol symbol : variable TRUE location: class changei.iTable return FALSE; i.java:201:: cannot find symbol symbol : variable FALSE location: class changei.iTable catch(Exception e){e.printStackTrace();return FALSE;} The Connection class comes from the DB package i created. Is the return TRUE/FALSE correct since the function is a Boolean return type?

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• Ubuntu VM "read only file system" fix?

  - by David

  I was going to install VMWare tools on an Ubuntu server Virtual Machine, but I ran into the issue of not being able to create a cdrom directory in the /mnt directory. I then tested to see if it was just a permissions issue, but I couldn't even create a folder in the home directory. It continues to state that it is a read only file system. I know a little about Linux, and I'm not comfortable with it yet. Any advice would be much appreciated. Requested Information from a comment: username@servername:~$ mount /dev/sda1 on / type ext4 (rw,errors=remount-ro) proc on /proc type proc (rw) none on /sys type sysfs (rw,noexec,nosuid,nodev) none on /sys/fs/fuse/connections type fusectl (rw) none on /sys/kernel/debug type debugfs (rw) none on /sys/kernel/security type securityfs (rw) udev on /dev type tmpfs (rw,mode=0755) none on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620) none on /dev/shm type tmpfs (rw,nosuid,nodev) none on /var/run type tmpfs (rw,nosuid,mode=0755) none on /var/lock type tmpfs (rw,noexec,nosuid,nodev) none on /lib/init/rw type tmpfs (rw,nosuid,mode=0755) binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev) For sure root output. root@server01:~# mount /dev/sda1 on / type ext4 (rw,errors=remount-ro) proc on /proc type proc (rw) none on /sys type sysfs (rw,noexec,nosuid,nodev) none on /sys/fs/fuse/connections type fusectl (rw) none on /sys/kernel/debug type debugfs (rw) none on /sys/kernel/security type securityfs (rw) udev on /dev type tmpfs (rw,mode=0755) none on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620) none on /dev/shm type tmpfs (rw,nosuid,nodev) none on /var/run type tmpfs (rw,nosuid,mode=0755) none on /var/lock type tmpfs (rw,noexec,nosuid,nodev) none on /lib/init/rw type tmpfs (rw,nosuid,mode=0755) binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev)

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• PDF Converter Elite Giveaway – Lets you create, convert and edit any type of PDF with ease

  - by Gopinath

  Are you looking for a PDF editing software that lets you create, edit and convert  any type of PDF with ease? Then here is a chance for you to win a lifetime free license of PDF Converter Elite software. Tech Dreams in partnership with pdfconverter.com  brings a giveaway contest exclusively for our readers. Continue reading to know the features of the application and giveaway contest details Adobe Acrobat  is the best software for creating, editing and converting PDF files, but you need spend a lot of money to buy it. PDF Converter Elite, which is priced at $100 has a rich set of features that satisfies most of your PDF management needs. Here is a quick run down of the feature of the application Create PDF files from almost every popular Windows file format – You can create a PDF  from almost 300 popular file formats supported by Windows. Want to convert a word document to PDF? It’s just a click away. How about converting Excels, PowerPoint presentations, text files, images, etc? Yes, with a single click you will be able to turn them to PDF Files. Convert PDF to Word, Excel, PowerPoint, Publisher, HTML – This is one of the best features i liked in this software. You can convert a PDF to any MS Office file format without loosing alignment and quality of the document. The converted documents looks exactly same as your PDF documents and you would be surprised to see near 100% layout replication in the converted document. I feel in love with the perfection at which the files are converted. Edit PDF files easily – You can rework with your PDF documents by inserting watermarks, numbers, headers, footers and more. Also you will be able to merge two PDF files, overlay pages, remove unwanted pages, split a single PDF in to multiple files. Secure PDF files by setting password – You can secure PDF files by limiting how others can use them – set password to open the documents, restrict various activities like printing, copy & paste, screen reading, form filling, etc.. If you are looking for an affordable PDF editing application then PDF Converter Elite is there for you. 10 x PDF Converter Elite Licenses Giveaway Here comes the details on wining a free single user license for our readers – we have 10 PDF Converter Elite single user licenses worth of $100 each. To win a license all you need to do is Like Tech Dreams Fan page on Facebook Tweet or Like this post – buttons are available just below the post heading in the top section of this page Finally drop a comment on how you would like to use PDF Converter Elite We will choose 10 winners through a lucky draw and the licenses will be sent to them in a personal email. Names of the winners will also be announced on Tech Dreams. So are you ready to grab a free copy of PDF Converter worth of $100?

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• SQL SERVER – IO_COMPLETION – Wait Type – Day 10 of 28

  - by pinaldave

  For any good system three things are vital: CPU, Memory and IO (disk). Among these three, IO is the most crucial factor of SQL Server. Looking at real-world cases, I do not see IT people upgrading CPU and Memory frequently. However, the disk is often upgraded for either improving the space, speed or throughput. Today we will look at an IO-related wait types. From Book On-Line: Occurs while waiting for I/O operations to complete. This wait type generally represents non-data page I/Os. Data page I/O completion waits appear as PAGEIOLATCH_* waits. IO_COMPLETION Explanation: Any tasks are waiting for I/O to finish. This is a good indication that IO needs to be looked over here. Reducing IO_COMPLETION wait: When it is an issue concerning the IO, one should look at the following things related to IO subsystem: Proper placing of the files is very important. We should check the file system for proper placement of files – LDF and MDF on a separate drive, TempDB on another separate drive, hot spot tables on separate filegroup (and on separate disk),etc. Check the File Statistics and see if there is higher IO Read and IO Write Stall SQL SERVER – Get File Statistics Using fn_virtualfilestats. Check event log and error log for any errors or warnings related to IO. If you are using SAN (Storage Area Network), check the throughput of the SAN system as well as the configuration of the HBA Queue Depth. In one of my recent projects, the SAN was performing really badly so the SAN administrator did not accept it. After some investigations, he agreed to change the HBA Queue Depth on development (test environment) set up and as soon as we changed the HBA Queue Depth to quite a higher value, there was a sudden big improvement in the performance. It is very possible that there are no proper indexes in the system and there are lots of table scans and heap scans. Creating proper index can reduce the IO bandwidth considerably. If SQL Server can use appropriate cover index instead of clustered index, it can effectively reduce lots of CPU, Memory and IO (considering cover index has lesser columns than cluster table and all other; it depends upon the situation). You can refer to the two articles that I wrote; they are about how to optimize indexes: Create Missing Indexes Drop Unused Indexes Checking Memory Related Perfmon Counters SQLServer: Memory Manager\Memory Grants Pending (Consistent higher value than 0-2) SQLServer: Memory Manager\Memory Grants Outstanding (Consistent higher value, Benchmark) SQLServer: Buffer Manager\Buffer Hit Cache Ratio (Higher is better, greater than 90% for usually smooth running system) SQLServer: Buffer Manager\Page Life Expectancy (Consistent lower value than 300 seconds) Memory: Available Mbytes (Information only) Memory: Page Faults/sec (Benchmark only) Memory: Pages/sec (Benchmark only) Checking Disk Related Perfmon Counters Average Disk sec/Read (Consistent higher value than 4-8 millisecond is not good) Average Disk sec/Write (Consistent higher value than 4-8 millisecond is not good) Average Disk Read/Write Queue Length (Consistent higher value than benchmark is not good) Note: The information presented here is from my experience and there is no way that I claim it to be accurate. I suggest reading Book OnLine for further clarification. All the discussions of Wait Stats in this blog are generic and vary from system to system. It is recommended that you test this on a development server before implementing it to a production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Types, SQL White Papers, T SQL, Technology

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• Automount of external hard disk

  - by moose

  I have an Intenso 6002560 1TB Memory Station - an external hard disk. This hard disk gets connected via Y-USB cable. When I connect both USB-ends to my Notebook, it gets recognized by my Ubuntu 10.04.4 LTS system: moose@pc07:~$ lsusb [...] Bus 002 Device 005: ID 13fd:1840 Initio Corporation [...] and Disk /dev/sda: 320.1 GB, 320072933376 bytes 255 heads, 63 sectors/track, 38913 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00065e10 Device Boot Start End Blocks Id System /dev/sda1 * 1 37810 303704064 83 Linux /dev/sda2 37810 38914 8864769 5 Extended /dev/sda5 37810 38914 8864768 82 Linux swap / Solaris Disk /dev/sdc: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x0d6ea32a Device Boot Start End Blocks Id System /dev/sdc1 1 121601 976759008+ c W95 FAT32 (LBA) But it did not get mounted: moose@pc07:/dev$ mount -l /dev/sda1 on / type ext4 (rw,errors=remount-ro,user_xattr) proc on /proc type proc (rw,noexec,nosuid,nodev) none on /sys type sysfs (rw,noexec,nosuid,nodev) none on /sys/fs/fuse/connections type fusectl (rw) none on /sys/kernel/debug type debugfs (rw) none on /sys/kernel/security type securityfs (rw) none on /dev type devtmpfs (rw,mode=0755) none on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620) none on /dev/shm type tmpfs (rw,nosuid,nodev) none on /var/run type tmpfs (rw,nosuid,mode=0755) none on /var/lock type tmpfs (rw,noexec,nosuid,nodev) none on /lib/init/rw type tmpfs (rw,nosuid,mode=0755) binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev) gvfs-fuse-daemon on /home/moose/.gvfs type fuse.gvfs-fuse-daemon (rw,nosuid,nodev,user=moose) However, I could mount it manually with mount -t vfat /dev/sdc1 /mnt/sdc1 as you can see here: moose@pc07:~$ mount -l /dev/sda1 on / type ext4 (rw,errors=remount-ro,user_xattr) proc on /proc type proc (rw,noexec,nosuid,nodev) none on /sys type sysfs (rw,noexec,nosuid,nodev) none on /sys/fs/fuse/connections type fusectl (rw) none on /sys/kernel/debug type debugfs (rw) none on /sys/kernel/security type securityfs (rw) none on /dev type devtmpfs (rw,mode=0755) none on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620) none on /dev/shm type tmpfs (rw,nosuid,nodev) none on /var/run type tmpfs (rw,nosuid,mode=0755) none on /var/lock type tmpfs (rw,noexec,nosuid,nodev) none on /lib/init/rw type tmpfs (rw,nosuid,mode=0755) binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev) gvfs-fuse-daemon on /home/moose/.gvfs type fuse.gvfs-fuse-daemon (rw,nosuid,nodev,user=moose) /dev/sdc1 on /mnt/sdc1 type vfat (rw) edit: Another command: moose@pc07:~$ sudo blkid -o list device fs_type label mount point UUID ---------------------------------------------------------------------------------------------------------------------- /dev/sda1 ext4 / 45eb611b-517e-425b-8057-0391726cccd5 /dev/sda5 swap <swap> e9dc42f3-594c-4b62-874a-305eda5eed41 moose@pc07:~$ blkid -o list device fs_type label mount point UUID ---------------------------------------------------------------------------------------------------------------------- /dev/sda1 ext4 / 45eb611b-517e-425b-8057-0391726cccd5 /dev/sda5 swap <swap> e9dc42f3-594c-4b62-874a-305eda5eed41 /dev/sdc1 /mnt/sdc1 edit: another command: moose@pc07:~$ ls -l /dev/disk/by-uuid/ total 0 lrwxrwxrwx 1 root root 10 2012-09-30 09:31 45eb611b-517e-425b-8057-0391726cccd5 -> ../../sda1 lrwxrwxrwx 1 root root 10 2012-09-30 09:31 e9dc42f3-594c-4b62-874a-305eda5eed41 -> ../../sda5 Here is a link to a Launchpad question about this problem. But I would like it to mount automatically. What do I have to do?

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• Naming methods that do the same thing but return different types

  - by Konstantin Ð.

  Let's assume that I'm extending a graphical file chooser class (JFileChooser). This class has methods which display the file chooser dialog and return a status signature in the form of an int: APPROVE_OPTION if the user selects a file and hits Open /Save, CANCEL_OPTION if the user hits Cancel, and ERROR_OPTION if something goes wrong. These methods are called showDialog(). I find this cumbersome, so I decide to make another method that returns a File object: in the case of APPROVE_OPTION, it returns the file selected by the user; otherwise, it returns null. This is where I run into a problem: would it be okay for me to keep the showDialog() name, even though methods with that name — and a different return type — already exist? To top it off, my method takes an additional parameter: a File which denotes in which directory the file chooser should start. My question to you: Is it okay to call a method the same name as a superclass method if they return different types? Or would that be confusing to API users? (If so, what other name could I use?) Alternatively, should I keep the name and change the return type so it matches that of the other methods? public int showDialog(Component parent, String approveButtonText) // Superclass method public File showDialog(Component parent, File location) // My method

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• Duck checker in Python: does one exist?

  - by elliot42

  Python uses duck-typing, rather than static type checking. But many of the same concerns ultimately apply: does an object have the desired methods and attributes? Do those attributes have valid, in-range values? Whether you're writing constraints in code, or writing test cases, or validating user input, or just debugging, inevitably somewhere you'll need to verify that an object is still in a proper state--that it still "looks like a duck" and "quacks like a duck." In statically typed languages you can simply declare "int x", and anytime you create or mutate x, it will always be a valid int. It seems feasible to decorate a Python object to ensure that it is valid under certain constraints, and that every time that object is mutated it is still valid under those constraints. Ideally there would be a simple declarative syntax to express "hasattr length and length is non-negative" (not in those words. Not unlike Rails validators, but less human-language and more programming-language). You could think of this as ad-hoc interface/type system, or you could think of it as an ever-present object-level unit test. Does such a library exist to declare and validate constraint/duck-checking on Python-objects? Is this an unreasonable tool to want? :) (Thanks!) Contrived example: rectangle = {'length': 5, 'width': 10} # We live in a fictional universe where multiplication is super expensive. # Therefore any time we multiply, we need to cache the results. def area(rect): if 'area' in rect: return rect['area'] rect['area'] = rect['length'] * rect['width'] return rect['area'] print area(rectangle) rectangle['length'] = 15 print area(rectangle) # compare expected vs. actual output! # imagine the same thing with object attributes rather than dictionary keys.

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• How do you encode Algebraic Data Types in a C#- or Java-like language?

  - by Jörg W Mittag

  There are some problems which are easily solved by Algebraic Data Types, for example a List type can be very succinctly expressed as: data ConsList a = Empty | ConsCell a (ConsList a) consmap f Empty = Empty consmap f (ConsCell a b) = ConsCell (f a) (consmap f b) l = ConsCell 1 (ConsCell 2 (ConsCell 3 Empty)) consmap (+1) l This particular example is in Haskell, but it would be similar in other languages with native support for Algebraic Data Types. It turns out that there is an obvious mapping to OO-style subtyping: the datatype becomes an abstract base class and every data constructor becomes a concrete subclass. Here's an example in Scala: sealed abstract class ConsList[+T] { def map[U](f: T => U): ConsList[U] } object Empty extends ConsList[Nothing] { override def map[U](f: Nothing => U) = this } final class ConsCell[T](first: T, rest: ConsList[T]) extends ConsList[T] { override def map[U](f: T => U) = new ConsCell(f(first), rest.map(f)) } val l = (new ConsCell(1, new ConsCell(2, new ConsCell(3, Empty))) l.map(1+) The only thing needed beyond naive subclassing is a way to seal classes, i.e. a way to make it impossible to add subclasses to a hierarchy. How would you approach this problem in a language like C# or Java? The two stumbling blocks I found when trying to use Algebraic Data Types in C# were: I couldn't figure out what the bottom type is called in C# (i.e. I couldn't figure out what to put into class Empty : ConsList< ??? >) I couldn't figure out a way to seal ConsList so that no subclasses can be added to the hierarchy What would be the most idiomatic way to implement Algebraic Data Types in C# and/or Java? Or, if it isn't possible, what would be the idiomatic replacement?

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• How to distinguish doc, ppt, xls files, without looking at file extension

  - by Shelby. S

  So I was wondering how would you differentiate ppt, xls and doc files from each other in linux regardless of extensions. I tried 'file' but from the looks of it, all of MSOffice files are categorized under the same file type. Similarly I'm having trouble with docx, xlsx and pptx files, since they're essentially all zip files containing a bunch of xml. I also tried a python script importing the magic module, but no go. I'm trying to identify the actual file for a sandbox analysis. And for this specific purpose I need to find the actual file type in order to run it in the sandbox vm (the Windows vm runs everything by extension). Let's say my sample file is labeled as try.exe, but in reality it's just a doc file. My script will rename it as try.exe.doc, which would work fine for doc files. But since linux identifies all MSOffice files as simple DOC files then there's no way to identify ppt or xls files. As a result the sandbox wont' analyze the sample correctly.

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• Matlab: Why is '1' + 1 == 50? [migrated]

  - by phi

  Matlab has weak dynamic typing, which is what causes this weird behaviour. What I do not understand is what exactly happens, as this result really surprises me. Edit: To clarify, what I'm describing is clearly a result of Matlab storing chars in ASCII-format, which was also mentioned in the comments. I'm more interested in the way Matlab handles its variables, and specifically, how and when it assigns a type/tag to the values. Thanks. '1' is a 1-by-1 matrix of chars in matlab and '123' is a 1-by-3 matrix of chars. As expected, 1 returns a 1-by-1 double. Now if I enter '1' + 1 I get 50 as a 1-by-1 double, and if I enter '123' + 1 I get a 1-by-3 double [ 50 51 52 ] Furthermore, if I type 'a' + 1 the result is 98 in a 1-by-1 double. I assume this has to do with how Matlab stores char-variables in ascii form, but how exactly is it handling these? Are the data actually unityped and tagged, or how does it work? Thanks.

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• How can I make the C# compiler infer these type parameters automatically?

  - by John Feminella

  I have some code that looks like the following. First I have some domain classes and some special comparators for them. public class Fruit { public int Calories { get; set; } public string Name { get; set; } } public class FruitEqualityComparer : IEqualityComparer<Fruit> { // ... } public class BasketEqualityComparer : IEqualityComparer<IEnumerable<Fruit>> { // ... } Next, I have a helper class called ConstraintChecker. It has a simple BaseEquals method that makes sure some simple base cases are considered: public static class ConstraintChecker { public static bool BaseEquals(T lhs, T rhs) { bool sameObject = l == r; bool leftNull = l == null; bool rightNull = r == null; return sameObject && !leftNull && !rightNull; } There's also a SemanticEquals method which is just a BaseEquals check and a comparator function that you specify. public static bool SemanticEquals<T>(T lhs, T rhs, Func<T, T, bool> f) { return BaseEquals(lhs, rhs) && f(lhs, rhs); } And finally there's a SemanticSequenceEquals method which accepts two IEnumerable<T> instances to compare, and an IEqualityComparer instance that will get called on each pair of elements in the list via Enumerable.SequenceEquals. public static bool SemanticSequenceEquals<T, U, V>(U lhs, U rhs, V comparator) where U : IEnumerable<T> where V : IEqualityComparer<T> { return SemanticEquals(lhs, rhs, (l, r) => lhs.SequenceEqual(rhs, comparator)); } } // end of ConstraintChecker The point of SemanticSequenceEquals is that you don't have to define two comparators whenever you want to compare both IEnumerable<T> and T instances; now you can just specify an IEqualityComparer<T> and it will also handle lists when you invoke SemanticSequenceEquals. So I could get rid of the BasketEqualityComparer class, which would be nice. But there's a problem. The C# compiler can't figure out the types involved when you invoke SemanticSequenceEquals: return ConstraintChecker.SemanticSequenceEquals(lhs, rhs, new FruitEqualityComparer()); If I specify them explicitly, it works: return ConstraintChecker.SemanticSequenceEquals< Fruit, IEnumerable<Fruit>, IEqualityComparer<Fruit> > (lhs, rhs, new FruitEqualityComparer()); What can I change here so that I don't have to write the type parameters explicitly?

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• Why is my (Type).GetFields(BindingFlags.Instance | BindingFlags.Public) not working?

  - by granadaCoder

  My code can see the NonPublic members, but not the Public ones. (???) Full sample code below. FieldInfo[] publicFieldInfos = t.GetFields(BindingFlags.Instance | BindingFlags.Public); is returning nothing. Note, I'm trying to get at the properties on the abstract class as well as the 1 concrete class. (And read the attributes as well). I'm going bonkers on this one....the msdn example works with the 2 flags (BindingFlags.Instance | BindingFlags.Public).....but my mini inheritance example below is not. THANKS in advance. /////////////START CODE private void RunTest1() { try { textBox1.Text = string.Empty; Type t = typeof(MyInheritedClass); //Look at the BindingFlags *** NonPublic *** int fieldCount = 0; while (null != t) { fieldCount += t.GetFields(BindingFlags.Instance | BindingFlags.NonPublic).Length; FieldInfo[] nonPublicFieldInfos = t.GetFields(BindingFlags.Instance | BindingFlags.NonPublic); foreach (FieldInfo field in nonPublicFieldInfos) { if (null != field) { Console.WriteLine(field.Name); } } t = t.BaseType; } Console.WriteLine("\n\r------------------\n\r"); //Look at the BindingFlags *** Public *** t = typeof(MyInheritedClass); FieldInfo[] publicFieldInfos = t.GetFields(BindingFlags.Instance | BindingFlags.Public); foreach (FieldInfo field in publicFieldInfos) { if (null != field) { Console.WriteLine(field.Name); object[] attributes = field.GetCustomAttributes(t, true); if (attributes != null && attributes.Length > 0) { foreach (Attribute att in attributes) { Console.WriteLine(att.GetType().Name); } } } } } catch (Exception ex) { ReportException(ex); } } private void ReportException(Exception ex) { Exception innerException = ex; while (innerException != null) { Console.WriteLine(innerException.Message + System.Environment.NewLine + innerException.StackTrace + System.Environment.NewLine + System.Environment.NewLine); innerException = innerException.InnerException; } } public abstract class MySuperType { public MySuperType(string st) { this.STString = st; } public string STString { get; set; } public abstract string MyAbstractString {get;set;} } public class MyInheritedClass : MySuperType { public MyInheritedClass(string ic) : base(ic) { this.ICString = ic; } [Description("This is an important property"),Category("HowImportant")] public string ICString { get; set; } private string _oldSchoolPropertyString = string.Empty; public string OldSchoolPropertyString { get { return _oldSchoolPropertyString; } set { _oldSchoolPropertyString = value; } } [Description("This is a not so importarnt property"), Category("HowImportant")] public override string MyAbstractString { get; set; } }

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• SQL SERVER – Signal Wait Time Introduction with Simple Example – Wait Type – Day 2 of 28

  - by pinaldave

  In this post, let’s delve a bit more in depth regarding wait stats. The very first question: when do the wait stats occur? Here is the simple answer. When SQL Server is executing any task, and if for any reason it has to wait for resources to execute the task, this wait is recorded by SQL Server with the reason for the delay. Later on we can analyze these wait stats to understand the reason the task was delayed and maybe we can eliminate the wait for SQL Server. It is not always possible to remove the wait type 100%, but there are few suggestions that can help. Before we continue learning about wait types and wait stats, we need to understand three important milestones of the query life-cycle. Running - a query which is being executed on a CPU is called a running query. This query is responsible for CPU time. Runnable – a query which is ready to execute and waiting for its turn to run is called a runnable query. This query is responsible for Signal Wait time. (In other words, the query is ready to run but CPU is servicing another query). Suspended – a query which is waiting due to any reason (to know the reason, we are learning wait stats) to be converted to runnable is suspended query. This query is responsible for wait time. (In other words, this is the time we are trying to reduce). In simple words, query execution time is a summation of the query Executing CPU Time (Running) + Query Wait Time (Suspended) + Query Signal Wait Time (Runnable). Again, it may be possible a query goes to all these stats multiple times. Let us try to understand the whole thing with a simple analogy of a taxi and a passenger. Two friends, Tom and Danny, go to the mall together. When they leave the mall, they decide to take a taxi. Tom and Danny both stand in the line waiting for their turn to get into the taxi. This is the Signal Wait Time as they are ready to get into the taxi but the taxis are currently serving other customer and they have to wait for their turn. In other word they are in a runnable state. Now when it is their turn to get into the taxi, the taxi driver informs them he does not take credit cards and only cash is accepted. Neither Tom nor Danny have enough cash, they both cannot get into the vehicle. Tom waits outside in the queue and Danny goes to ATM to fetch the cash. During this time the taxi cannot wait, they have to let other passengers get into the taxi. As Tom and Danny both are outside in the queue, this is the Query Wait Time and they are in the suspended state. They cannot do anything till they get the cash. Once Danny gets the cash, they are both standing in the line again, creating one more Signal Wait Time. This time when their turn comes they can pay the taxi driver in cash and reach their destination. The time taken for the taxi to get from the mall to the destination is running time (CPU time) and the taxi is running. I hope this analogy is bit clear with the wait stats. You can check the Signalwait stats using following query of Glenn Berry. -- Signal Waits for instance SELECT CAST(100.0 * SUM(signal_wait_time_ms) / SUM (wait_time_ms) AS NUMERIC(20,2)) AS [%signal (cpu) waits], CAST(100.0 * SUM(wait_time_ms - signal_wait_time_ms) / SUM (wait_time_ms) AS NUMERIC(20,2)) AS [%resource waits] FROM sys.dm_os_wait_stats OPTION (RECOMPILE); Higher the Signal wait stats are not good for the system. Very high value indicates CPU pressure. In my experience, when systems are running smooth and without any glitch the Signal wait stat is lower than 20%. Again, this number can be debated (and it is from my experience and is not documented anywhere). In other words, lower is better and higher is not good for the system. In future articles we will discuss in detail the various wait types and wait stats and their resolution. Read all the post in the Wait Types and Queue series. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL DMV, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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• SQL SERVER – Single Wait Time Introduction with Simple Example – Wait Type – Day 2 of 28

  - by pinaldave

  In this post, let’s delve a bit more in depth regarding wait stats. The very first question: when do the wait stats occur? Here is the simple answer. When SQL Server is executing any task, and if for any reason it has to wait for resources to execute the task, this wait is recorded by SQL Server with the reason for the delay. Later on we can analyze these wait stats to understand the reason the task was delayed and maybe we can eliminate the wait for SQL Server. It is not always possible to remove the wait type 100%, but there are few suggestions that can help. Before we continue learning about wait types and wait stats, we need to understand three important milestones of the query life-cycle. Running - a query which is being executed on a CPU is called a running query. This query is responsible for CPU time. Runnable – a query which is ready to execute and waiting for its turn to run is called a runnable query. This query is responsible for Single Wait time. (In other words, the query is ready to run but CPU is servicing another query). Suspended – a query which is waiting due to any reason (to know the reason, we are learning wait stats) to be converted to runnable is suspended query. This query is responsible for wait time. (In other words, this is the time we are trying to reduce). In simple words, query execution time is a summation of the query Executing CPU Time (Running) + Query Wait Time (Suspended) + Query Single Wait Time (Runnable). Again, it may be possible a query goes to all these stats multiple times. Let us try to understand the whole thing with a simple analogy of a taxi and a passenger. Two friends, Tom and Danny, go to the mall together. When they leave the mall, they decide to take a taxi. Tom and Danny both stand in the line waiting for their turn to get into the taxi. This is the Signal Wait Time as they are ready to get into the taxi but the taxis are currently serving other customer and they have to wait for their turn. In other word they are in a runnable state. Now when it is their turn to get into the taxi, the taxi driver informs them he does not take credit cards and only cash is accepted. Neither Tom nor Danny have enough cash, they both cannot get into the vehicle. Tom waits outside in the queue and Danny goes to ATM to fetch the cash. During this time the taxi cannot wait, they have to let other passengers get into the taxi. As Tom and Danny both are outside in the queue, this is the Query Wait Time and they are in the suspended state. They cannot do anything till they get the cash. Once Danny gets the cash, they are both standing in the line again, creating one more Single Wait Time. This time when their turn comes they can pay the taxi driver in cash and reach their destination. The time taken for the taxi to get from the mall to the destination is running time (CPU time) and the taxi is running. I hope this analogy is bit clear with the wait stats. You can check the single wait stats using following query of Glenn Berry. -- Signal Waits for instance SELECT CAST(100.0 * SUM(signal_wait_time_ms) / SUM (wait_time_ms) AS NUMERIC(20,2)) AS [%signal (cpu) waits], CAST(100.0 * SUM(wait_time_ms - signal_wait_time_ms) / SUM (wait_time_ms) AS NUMERIC(20,2)) AS [%resource waits] FROM sys.dm_os_wait_stats OPTION (RECOMPILE); Higher the single wait stats are not good for the system. Very high value indicates CPU pressure. In my experience, when systems are running smooth and without any glitch the single wait stat is lower than 20%. Again, this number can be debated (and it is from my experience and is not documented anywhere). In other words, lower is better and higher is not good for the system. In future articles we will discuss in detail the various wait types and wait stats and their resolution. Read all the post in the Wait Types and Queue series. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL DMV, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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• JBoss 5.1.0.GA and huge vfs-nested.tmp

  - by Petteri Hietavirta

  I noticed this while running a performance test with JMeter. For first half an hour everything was fine and the /server/all/tmp directory size was around 36M. Then suddenly the tmp directory grew up to 6.1G. The space was taken by jar files inside vfs-nested.tmp. I found https://jira.jboss.org/jira/browse/JBAS-7126 but adding that config but it made no difference.

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