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• Programming language features that help to catch bugs early

  - by Christian Neumanns

  Do you know any programming language features that help to detect bugs early in the software development process - ideally at compile-time or else as early as possible at run-time? Examples of well-known and effective bug-reducing features are: Static typing and generic types: type incompatibility errors are detected by the compiler Design by Contract (TM), also called Contract Programming: invalid values are quickly detected at runtime (through preconditions, postconditions and class invariants) Unit testing I ask this question in the context of improving an object-oriented programming language (called Obix) which has been designed from the ground up to 'make it easy to quickly write reliable code'. Besides the features mentioned above this language also incorporates other Fail-fast features such as: Objects are immutable by default Void (null) values are not allowed by default The aim is to add more Fail-fast concepts to the language. If you know other features which help to write less error-prone code then please let us know. Thank you.

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• DBMS agnostic - What to name the COUNT column from a SQL Query

  - by cyberkiwi

  I have trouble naming the COUNT() column from SQL queries and will swap between various variants _Count [Count] (sql, or "count" or backticks for MySQL etc) C Cnt CountSomething (where "something" is the field being counted, or "CountAll") NoOfRows RowCount etc Has anyone come up with any name that you are happy with and always use without hesitation? This is bothering me because after joining SO just recently, my answers have shown this tendency of flip-flopping with no consistency. I need to get this sorted. Please help. (While we're at it, what do you use for SUM etc?) Note: Before you close this question, consider that this one was not: What's the best name for a non-mutating “add” method on an immutable collection?

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• What threading pratice is good 90% of the time?

  - by acidzombie24

  Since my SO thread was closed i guess i can ask it here. What practice or practices are good 90% of the time when working with threading with multiple cores? Personally all i have done was share immutable classes and pass (copy) data to a queue to the destine thread. Note: This is for research and when i say 90% of the time i dont mean it is allowed to fail 10% of the time (thats ridiculous!) i mean 90% it is a good solution while the other 10% it is not so desirable due to implementation or efficiently reasons (or plainly another technique fits the problem domain a lot better).

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• DDD and validation of aggregate root

  - by Mik378

  Suppose an aggregate root : MailConfiguration (wrapping an AddressPart object). The AddressPart object is a simple immutable value object with some fields like senderAdress, recipentAddress (to make example simple). As being an invariant object, AddressPart should logically wrap its own Validator (by the way of external a kind of AddressValidator for respecting Single Responsibility Principle) I read some articles that claimed an aggregateRoot must validate its 'children'. However, if we follow this principle, one could create an AddressPart with an uncohesive/invalid state. What are your opinion? Should I move the collaborator AddressValidator(used in constructor so in order to validate immediately the cohesion of an AddressPart) from AddressPart and assign it to aggregateRoot (MailConfiguration) ?

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• How to use OpenGL functions from multiples thread?

  - by Robert

  I'm writing a small game using OpenGL. I'm implementing basic networking in this game and I'm facing a problem. I have a thread in my client socket class that check for available data, when there are data I raise an event like this : immutable int len = this.m_socket.receive(data); if(len > 0) { this.m_onDataEvent(data); } Then on my game class, I have a function that handle and parse data like this : switch(msgId) { case ProtocolID.CharacterData: // Load terrain with opengl, character model.... Im not able to call opengl functions because my opengl context is created from a different thread. But I really don't know how I can solve this problem, I tried Google but it's really hard to find a solution. I'm using D programming language if it can help.

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• Instructions on Installing the FreeNX server on Ubuntu Karmic (9.10) are incorrect

  - by Bob Free

  How does one fix (or report an error) on an 'immutable' help.ubuntu.community wiki page? I am a registered member of the wiki. On http://help.ubuntu.com/community/FreeNX under the section: Installing the FreeNX server on Ubuntu Karmic (9.10) and higher, step #2, bjorn-nostvold erroneously changed on 2013-01-24 "add-apt-repository" to "apt-add-repository". The original "add-apt-repository" is correct - at least on my Karmic (9.10) version of Ubuntu. By the number of confused people I've found via google search, this seems to be throwing off a lot of people, myself included.

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• SVN naming convention: repository, branches, tags

  - by LookitsPuck

  Hey all! Just curious what your naming conventions are for the following: Repository name Branches Tags Right now, we're employing the following standards with SVN, but would like to improve on it: Each project has its own repository Each repository has a set of directories: tags, branches, trunk Tags are immutable copies of the the tree (release, beta, rc, etc.) Branches are typically feature branches Trunk is ongoing development (quick additions, bug fixes, etc.) Now, with that said, I'm curious how everyone is not only handling the naming of their repositories, but also their tags and branches. For example, do you employ a camel case structure for the project name? So, if your project is something like Backyard Baseball for Youngins, how do you handle that? backyardBaseballForYoungins backyard_baseball_for_youngins BackyardBaseballForYoungins backyardbaseballforyoungins That seems rather trivial, but it's a question. If you're going with the feature branch paradigm, how do you name your feature branches? After the feature itself in plain English? Some sort of versioning scheme? I.e. say you want to add functionality to the Backyard Baseball app that allows users to add their own statistics. What would you call your branch? {repoName}/branches/user-add-statistics {repoName}/branches/userAddStatistics {repoName}/branches/user_add_statistics etc. Or: {repoName}/branches/1.1.0.1 If you go the version route, how do you correlate the version numbers? It seems that feature branches wouldn't benefit much from a versioning schema, being that 1 developer could be working on the "user add statistics" functionality, and another developer could be working on the "admin add statistics" functionality. How are these do branch versions named? Are they better off being: {repoName}/branches/1.1.0.1 - user add statistics {repoName}/branches/1.1.0.2 - admin add statistics And once they're merged into the trunk, the trunk might increment appropriately? Tags seem like they'd benefit the most from version numbers. With that being said, how are you correlating the versions for your project (whether it be trunk, branch, tag, etc.) with SVN? I.e. how do you, as the developer, know that 1.1.1 has admin add statistics, and user add statistics functionality? How are these descriptive and linked? It'd make sense for tags to have release notes in each tag since they're immutable. But, yeah, what are your SVN policies going forward?

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• How to insert object already existing objects in NSMutableArray list.

  - by Madan Mohan

  Hi, I am getting the problem, while inserting an object into the main List. [editContactList addObject:editcontacts]; [editObject.contactList insertObject:editContactList atIndex:0];//error as mutating method sent to immutable object [editcontacts release]; please help me. Thank You, Madan mohan.

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• Can't get UpdateAttributeRequest to work

  - by dsabater

  I am trying to use the Metadata Web Service of Dynamics CRM to update the order of some picklist options using the UpdateAttributeRequest message. Though I get to change the attribute's DisplayName using the MergeLabels = false option, the picklist option values themselves seem immutable.

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• F# for C#/Haskell programmer

  - by Maciej Piechotka

  What is recommended tutorial of F# for Haskell programmer? F# seems to borrow a lot from Haskell but there are little traps which makes hard to write. Generally I need walkthrough the F# which would not explain what is the difference between mutable data and immutable (Haskell is much more strict in this area) etc. I know C# a little so I know more or less what .Net is about as well.

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• NHibernate dateTime as an ID Bad idea?

  - by Miau

  hi there I have an entity and it seems like using DateTime as the Id would be a good suit, however I there is this strange feeling that that it might be a terrible idea ( tho i cant come up with any logical reason as to why), This is an immutable object ( ie once the value is recorded it shouldn't really change ) So DateTime as id field in NHibernate yay or Nay? I would appreciate your comments on this

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• Value Object and View Model Property

  - by William

  I am working on a solution that used DDD for architecture. I have a property in my ViewModel which points to a ValueObject, the view model also implements INotifyPropertyChanged interface. The value of the ValueObject will change as a user enters data on the front end. The problem I am running into is the value object is suppose to be immutable. How can I work around this issue? Thank you in advance.

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• Defer Eclipse Treeviewer loading by DeferredTreeContentManager

  - by qichuan

  I understand there is an approach to defer TreeViewer loading by using DeferredTreeContentManager, learnt from this useful tutorial. However, this mechanism requires the model to implement IDeferredWorkbenchAdapter interface, which introduces problem to my legacy immutable model classes. Is it possible to use DeferredTreeContentManager without having model implementing IDeferredWorkbenchAdapter interface?

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• When i am replacing or inserting an object into nsmutable array, I am getting Exception.

  - by Madan Mohan

  Hi, While replacing or inserting into an nsmutable array, I am getting exception as Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '* -[NSCFArray replaceObjectAtIndex:withObject:]: mutating method sent to immutable object' [list replaceObjectAtIndex:indexRow withObject:editcontacts]; //or [list insertObject:editcontacts atIndex:indexRow]; please help me. Madan, Thank You.

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• Is String.concat slower than Array approach to join strings

  - by Rajat

  Strings in JavaScript are immutable. Across the web and here on Stack Overflow as well, I came across the Array approach to concatenate strings: var a = []; a.push(arg1,arg,2....); console.log(a.join('')); I know that this approach is better than the simple console.log(arg1 + arg2 +.....); for reasons of skipping creating intermediate objects but how does it fair better against : arg1.concat(arg2,arg3.....);

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• C# Dictionary<> and mutable keys

  - by Pierreten

  I was told that one of the many reasons strings were made immutable in the C# spec was to avoid the issue of HashTables having keys changed when references to the string keys altered their content. The Dictionary< type allows reference types to be used as a key. How does the dictionary avoid the issue of altered keys that lead to "misplaced" values? Is there a memberwise clone made of an object when used as a key?

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• What's the difference between typedef const struct *CGPath and typedef struct *CGPath?

  - by mystify

  I've found this in the CGPath.h header file. I'm curious what this const thing does? typedef struct CGPath *CGMutablePathRef; typedef const struct CGPath *CGPathRef; My guess: If I typedef something as const, it's constant so immutable and can't be changed in any way. Does that make sense?

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• One-line expression to map dictionary to another

  - by No Such IP

  I have dictionary like d = {'user_id':1, 'user':'user1', 'group_id':3, 'group_name':'ordinary users'} and "mapping" dictionary like: m = {'user_id':'uid', 'group_id':'gid', 'group_name':'group'} All i want to "replace" keys in first dictionary with keys from second (e.g. replace 'user_id' with 'uid', etc.) I know that keys are immutable and i know how to do it with 'if/else' statement. But maybe there is way to do it in one line expression?

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• svn: default name for a tag when name is not important?

  - by Jason S

  I need to tag the current state of my source tree in svn. My problem is I don't care what the name is, I just need to mark the current revision in an immutable* manner. (*subject to malicious behavior) What's the best way to do this? branches/ tags/ ??? trunk/ should ??? be the date, an incrementing sequence, the repository rev # ...?

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• Operation precedence on postgress

  - by user24691

  I have set new division on postgress pg_operator table because i want tath when is division by zero return 0. i have write this: create operator / ( procedure = zero_division, leftarg = double precision, rightarg = double precision); where zero_division is: CREATE OR REPLACE FUNCTION zero_division(double precision, double precision) RETURNS double precision AS 'select case when $2 = 0 then 0 else $1 / $2::real end;' LANGUAGE sql IMMUTABLE COST 100; when i run value/ 0 i get error of division.

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• NHibernate: How to-reconfigure mappings at runtime?

  - by George Mauer

  Let's get this out of the way first: I know that SessionFactory is immutable - I'm trying to change the Configuration at runtime and regenerate ISessionFactory. Specifically, I have a Customer mapped that will have some fields added to its dynamic-component node at runtime. I would like to do something like this var newSessionFactory = previousConfiguration .RemoveClassMapping(typeof(Customer)) .AddXmlString(newMappingForCustomer) .BuildSessionFactory(); However, I don't see any obvious way to remove a mapping, is there anything I can do short of regenerating the entire Configuration?

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• Solaris 11 Launch Blog Carnival Roundup

  - by constant

  Solaris 11 is here! And together with the official launch activities, a lot of Oracle and non-Oracle bloggers contributed helpful and informative blog articles to help your datacenter go to eleven. Here are some notable blog postings, sorted by category for your Solaris 11 blog-reading pleasure: Getting Started/Overview A lot of people speculated that the official launch of Solaris 11 would be on 11/11 (whatever way you want to turn it), but it actually happened two days earlier. Larry Wake himself offers 11 Reasons Why Oracle Solaris 11 11/11 Isn't Being Released on 11/11/11. Then, Larry goes on with a summary: Oracle Solaris 11: The First Cloud OS gives you a short and sweet rundown of what the major new features of Solaris 11 are. Jeff Victor has his own list of What's New in Oracle Solaris 11. A popular Solaris 11 meme is to write a blog post about 11 favourite features: Jim Laurent's 11 Reasons to Love Solaris 11, Darren Moffat's 11 Favourite Solaris 11 Features, Mike Gerdt's 11 of My Favourite Things! are just three examples of "11 Favourite Things..." type blog posts, I'm sure many more will follow... More official overview content for Solaris 11 is available from the Oracle Tech Network Solaris 11 Portal. Also, check out Rick Ramsey's blog post Solaris 11 Resources for System Administrators on the OTN Blog and his secret 5 Commands That Make Solaris Administration Easier post from the OTN Garage. (Automatic) Installation and the Image Packaging System (IPS) The brand new Image Packaging System (IPS) and the Automatic Installer (IPS), together with numerous other install/packaging/boot/patching features are among the most significant improvements in Solaris 11. But before installing, you may wonder whether Solaris 11 will support your particular set of hardware devices. Again, the OTN Garage comes to the rescue with Rick Ramsey's post How to Find Out Which Devices Are Supported By Solaris 11. Included is a useful guide to all the first steps to get your Solaris 11 system up and running. Tim Foster had a whole handful of blog posts lined up for the launch, teaching you everything you need to know about IPS but didn't dare to ask: The IPS System Repository, IPS Self-assembly - Part 1: Overlays and Part 2: Multiple Packages Delivering Configuration. Watch out for more IPS posts from Tim! If installing packages or upgrading your system from the net makes you uneasy, then you're not alone: Jim Laurent will tech you how Building a Solaris 11 Repository Without Network Connection will make your life easier. Many of you have already peeked into the future by installing Solaris 11 Express. If you're now wondering whether you can upgrade or whether a fresh install is necessary, then check out Alan Hargreaves's post Upgrading Solaris 11 Express b151a with support to Solaris 11. The trick is in upgrading your pkg(1M) first. Networking One of the first things to do after installing Solaris 11 (or any operating system for that matter), is to set it up for networking. Solaris 11 comes with the brand new "Network Auto-Magic" feature which can figure out everything by itself. For those cases where you want to exercise a little more control, Solaris 11 left a few people scratching their heads. Fortunately, Tschokko wrote up this cool blog post: Solaris 11 manual IPv4 & IPv6 configuration right after the launch ceremony. Thanks, Tschokko! And Milek points out a long awaited networking feature in Solaris 11 called Solaris 11 - hostmodel, which I know for a fact that many customers have looked forward to: How to "bind" a Solaris 11 system to a specific gateway for specific IP address it is using. Steffen Weiberle teaches us how to tune the Solaris 11 networking stack the proper way: ipadm(1M). No more fiddling with ndd(1M)! Check out his tutorial on Solaris 11 Network Tunables. And if you want to get even deeper into the networking stack, there's nothing better than DTrace. Alan Maguire teaches you in: DTracing TCP Congestion Control how to probe deeply into the Solaris 11 TCP/IP stack, the TCP congestion control part in particular. Don't miss his other DTrace and TCP related blog posts! DTrace And there we are: DTrace, the king of all observability tools. Long time DTrace veteran and co-author of The DTrace book*, Brendan Gregg blogged about Solaris 11 DTrace syscall provider changes. BTW, after you install Solaris 11, check out the DTrace toolkit which is installed by default in /usr/dtrace/DTT. It is chock full of handy DTrace scripts, many of which contributed by Brendan himself! Security Another big theme in Solaris 11, and one that is crucial for the success of any operating system in the Cloud is Security. Here are some notable posts in this category: Darren Moffat starts by showing us how to completely get rid of root: Completely Disabling Root Logins on Solaris 11. With no root user, there's one major entry point less to worry about. But that's only the start. In Immutable Zones on Encrypted ZFS, Darren shows us how to double the security of your services: First by locking them into the new Immutable Zones feature, then by encrypting their data using the new ZFS encryption feature. And if you're still missing sudo from your Linux days, Darren again has a solution: Password (PAM) caching for Solaris su - "a la sudo". If you're wondering how much compute power all this encryption will cost you, you're in luck: The Solaris X86 AESNI OpenSSL Engine will make sure you'll use your Intel's embedded crypto support to its fullest. And if you own a brand new SPARC T4 machine you're even luckier: It comes with its own SPARC T4 OpenSSL Engine. Dan Anderson's posts show how there really is now excuse not to encrypt any more... Developers Solaris 11 has a lot to offer to developers as well. Ali Bahrami has a series of blog posts that cover diverse developer topics: elffile: ELF Specific File Identification Utility, Using Stub Objects and The Stub Proto: Not Just For Stub Objects Anymore to name a few. BTW, if you're a developer and want to shape the future of Solaris 11, then Vijay Tatkar has a hint for you: Oracle (Sun Systems Group) is hiring! Desktop and Graphics Yes, Solaris 11 is a 100% server OS, but it can also offer a decent desktop environment, especially if you are a developer. Alan Coopersmith starts by discussing S11 X11: ye olde window system in today's new operating system, then Calum Benson shows us around What's new on the Solaris 11 Desktop. Even accessibility is a first-class citizen in the Solaris 11 user interface. Peter Korn celebrates: Accessible Oracle Solaris 11 - released! Performance Gone are the days of "Slowaris", when Solaris was among the few OSes that "did the right thing" while others cut corners just to win benchmarks. Today, Solaris continues doing the right thing, and it delivers the right performance at the same time. Need proof? Check out Brian's BestPerf blog with continuous updates from the benchmarking lab, including Recent Benchmarks Using Oracle Solaris 11! Send Me More Solaris 11 Launch Articles! These are just a few of the more interesting blog articles that came out around the Solaris 11 launch, I'm sure there are many more! Feel free to post a comment below if you find a particularly interesting blog post that hasn't been listed so far and share your enthusiasm for Solaris 11! *Affiliate link: Buy cool stuff and support this blog at no extra cost. We both win! var flattr_uid = '26528'; var flattr_tle = 'Solaris 11 Launch Blog Carnival Roundup'; var flattr_dsc = '<strong>Solaris 11 is here!</strong>And together with the official launch activities, a lot of Oracle and non-Oracle bloggers contributed helpful and informative blog articles to help your datacenter <a href="http://en.wikipedia.org/wiki/Up_to_eleven">go to eleven</a>.Here are some notable blog postings, sorted by category for your Solaris 11 blog-reading pleasure:'; var flattr_tag = 'blogging,digest,Oracle,Solaris,solaris,solaris 11'; var flattr_cat = 'text'; var flattr_url = 'http://constantin.glez.de/blog/2011/11/solaris-11-launch-blog-carnival-roundup'; var flattr_lng = 'en_GB'

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• How to create a chained differencing disk of another differencing disk in Virtual Box?

  - by WooYek

  How to create a differencing disk (a chained one) from a disk that is already a differencing image? I would like to have: W2008 (base immutable) - W2008+SQL2008 (differencing, with SQL installed) --- This I can do. - W2008+SQL2008+SharePoint (chained differencing with Sharepoint installed on top of SQL2008) There's some info about it the manual: http://www.virtualbox.org/manual/ch05.html#diffimages Differencing images can be chained. If another differencing image is created for a virtual disk that already has a differencing image, then it becomes a "grandchild" of the original parent. The first differencing image then becomes read-only as well, and write operations only go to the second-level differencing image. When reading from the virtual disk, VirtualBox needs to look into the second differencing image first, then into the first if the sector was not found, and then into the original image.* I don't get it...

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• Can KVM roll back changes to Virtual Disks automatically?

  - by Cygon

  I'm currently using VirtualBox on my Linux server to run a small Windows guest OS. I've configured its main virtual hard drive as what VBox calls "Immutable" - meaning that any changes to it are written into a differencing image that is discarded when the system reboots. Can KVM do something similar? I've read about snapshots via "savevm", "loadvm" but I believe that's saved states, not differencing images. What I ultimately want is a VM with two drives: one reverts on each reboot, one keeps its changes. Ideally, the unchangeable drive image should be stored with only read access granted to the user running KVM.

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• Great Blogs About Oracle Solaris 11

  - by Markus Weber

  Now that Oracle Solaris 11 has been released, why not blog about blogs. There is of course a tremendous amount of resource and information available, but valuable insights directly from people actually building the product is priceless. Here's a list of such great blogs. NOTE: If you think we missed some good ones, please let us know in the comments section !  Topic Title Author Top 11 Things My 11 favourite Solaris 11 features Darren Moffat Top 11 Things These are 11 of my favorite things! Mike Gerdts Top 11 Things 11 reason to love Solaris 11     Jim Laurent SysAdmin Resources Solaris 11 Resources for System Administrators Rick Ramsey Overview Oracle Solaris 11: The First Cloud OS Larry Wake Overview What's a "Cloud Operating System"? Harry Foxwell Overview What's New in Oracle Solaris 11 Jeff Victor Try it ! Virtually the fastest way to try Solaris 11 (and Solaris 10 zones) Dave Miner Upgrade Upgrading Solaris 11 Express b151a with support to Solaris 11 Alan Hargreaves IPS The IPS System Repository Tim Foster IPS Building a Solaris 11 repository without network connection Jim Laurent IPS IPS Self-assembly – Part 1: overlays Tim Foster IPS Self assembly – Part 2: multiple packages delivering configuration Tim Foster Security Immutable Zones on Encrypted ZFS Darren Moffat Security User home directory encryption with ZFS Darren Moffat Security Password (PAM) caching for Solaris su - "a la sudo" Darren Moffat Security Completely disabling root logins on Solaris 11 Darren Moffat Security OpenSSL Version in Solaris Darren Moffat Security Exciting Crypto Advances with the T4 processor and Oracle Solaris 11 Valerie Fenwick Performance Critical Threads Optimization Rafael Vanoni Performance SPARC T4-2 Delivers World Record SPECjvm2008 Result with Oracle Solaris 11 BestPerf Blog Performance Recent Benchmarks Using Oracle Solaris 11 BestPerf Blog Predictive Self Healing Introducing SMF Layers Sean Wilcox Predictive Self Healing Oracle Solaris 11 - New Fault Management Features Gavin Maltby Desktop What's new on the Solaris 11 Desktop? Calum Benson Desktop S11 X11: ye olde window system in today's new operating system Alan Coopersmith Desktop Accessible Oracle Solaris 11 - released! Peter Korn

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