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• Formal Languages, Inductive Proofs &amp; Regular Expressions

  - by MarkPearl

  So I am slogging away at my UNISA stuff. I have just finished doing the initial once non stop read through the first 11 chapters of my COS 201 Textbook - “Introduction to Computer Theory 2nd Edition” by Daniel Cohen. It has been an interesting couple of days, with familiar concepts coming up as well as some new territory. In this posting I am going to cover the first couple of chapters of the book. Let start with Formal Languages… What exactly is a formal language? Pretty much a no duh question for me but still a good one to ask – a formal language is a language that is defined in a precise mathematical way. Does that mean that the English language is a formal language? I would say no – and my main motivation for this is that one can have an English sentence that is correct grammatically that is also ambiguous. For example the ambiguous sentence: "I once shot an elephant in my pyjamas.” For this and possibly many other reasons that I am unaware of, English is termed a “Natural Language”. So why the importance of formal languages in computer science? Again a no duh question in my mind… If we want computers to be effective and useful tools then we need them to be able to evaluate a series of commands in some form of language that when interpreted by the device no confusion will exist as to what we were requesting. Imagine the mayhem that would exist if a computer misinterpreted a command to print a document and instead decided to delete it. So what is a Formal Language made up of… For my study purposes a language is made up of a finite alphabet. For a formal language to exist there needs to be a specification on the language that will describe whether a string of characters has membership in the language or not. There are two basic ways to do this: By a “machine” that will recognize strings of the language (e.g. Finite Automata). By a rule that describes how strings of a language can be formed (e.g. Regular Expressions). When we use the phrase “string of characters”, we can also be referring to a “word”. What is an Inductive Proof? So I am not to far into my textbook and of course it starts referring to proofs and different types. I have had to go through several different approaches of proofs in the past, but I can never remember their formal names , so when I saw “inductive proof” I thought to myself – what the heck is that? Google to the rescue… An inductive proof is like a normal proof but it employs a neat trick which allows you to prove a statement about an arbitrary number n by first proving it is true when n is 1 and then assuming it is true for n=k and showing it is true for n=k+1. The idea is that if you want to show that someone can climb to the nth floor of a fire escape, you need only show that you can climb the ladder up to the fire escape (n=1) and then show that you know how to climb the stairs from any level of the fire escape (n=k) to the next level (n=k+1). Does this sound like a form of recursion? No surprise then that in the same chapter they deal with recursive definitions. An example of a recursive definition for the language EVEN would the 3 rules below: 2 is in EVEN If x is in EVEN then so is x+2 The only elements in the set EVEN are those that be produced by the rules above. Nothing to exciting… So if a definition for a language is done recursively, then it makes sense that the language can be proved using induction. Regular Expressions So I am wondering to myself what use is this all – in fact – I find this the biggest challenge to any university material is that it is quite hard to find the immediate practical applications of some theory in real life stuff. How great was my joy when I suddenly saw the word regular expression being introduced. I had been introduced to regular expressions on Stack Overflow where I was trying to recognize if some text measurement put in by a user was in a valid form or not. For instance, the imperial system of measurement where you have feet and inches can be represented in so many different ways. I had eventually turned to regular expressions as an easy way to check if my parser could correctly parse the text or not and convert it to a normalize measurement. So some rules about languages and regular expressions… Any finite language can be represented by at least one if not more regular expressions A regular expressions is almost a rule syntax for expressing how regular languages can be formed regular expressions are cool For a regular expression to be valid for a language it must be able to generate all the words in the language and no other words. This is important. It doesn’t help me if my regular expression parses 100% of my measurement texts but also lets one or two invalid texts to pass as well. Okay, so this posting jumps around a bit – but introduces some very basic fundamentals for the subject which will be built on in later postings… Time to go and do some practical examples now…

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• Silverlight 5 &ndash; What&rsquo;s New? (Including Screenshots &amp; Code Snippets)

  - by mbcrump

  Silverlight 5 is coming next year (2011) and this blog post will tell you what you need to know before the beta ships. First, let me address people saying that it is dead after PDC 2010. I believe that it’s best to see what the market is doing, not the vendor. Below is a list of companies that are developing Silverlight 4 applications shown during the Silverlight Firestarter. Some of the companies have shipped and some haven’t. It’s just great to see the actual company names that are working on Silverlight instead of “people are developing for Silverlight”. The next thing that I wanted to point out was that HTML5, WPF and Silverlight can co-exist. In case you missed Scott Gutherie’s keynote, they actually had a slide with all three stacked together. This shows Microsoft will be heavily investing in each technology.  Even I, a Silverlight developer, am reading Pro HTML5. Microsoft said that according to the Silverlight Feature Voting site, 21k votes were entered. Microsoft has implemented about 70% of these votes in Silverlight 5. That is an amazing number, and I am crossing my fingers that Microsoft bundles Silverlight with Windows 8. Let’s get started… what’s new in Silverlight 5? I am going to show you some great application and actual code shown during the Firestarter event. Media Hardware Video Decode – Instead of using CPU to decode, we will offload it to GPU. This will allow netbooks, etc to play videos. Trickplay – Variable Speed Playback – Pitch Correction (If you speed up someone talking they won’t sound like a chipmunk). Power Management – Less battery when playing video. Screensavers will no longer kick in if watching a video. If you pause a video then screensaver will kick in. Remote Control Support – This will allow users to control playback functions like Pause, Rewind and Fastforward. IIS Media Services 4 has shipped and now supports Azure. Data Binding Layout Transitions – Just with a few lines of XAML you can create a really rich experience that is not using Storyboards or animations. RelativeSource FindAncestor – Ancestor RelativeSource bindings make it much easier for a DataTemplate to bind to a property on a container control. Custom Markup Extensions – Markup extensions allow code to be run at XAML parse time for both properties and event handlers. This is great for MVVM support. Changing Styles during Runtime By Binding in Style Setters – Changing Styles at runtime used to be a real pain in Silverlight 4, now it’s much easier. Binding in style setters allows bindings to reference other properties. XAML Debugging – Below you can see that we set a breakpoint in XAML. This shows us exactly what is going on with our binding.  WCF & RIA Services WS-Trust Support – Taken from Wikipedia: WS-Trust is a WS-* specification and OASIS standard that provides extensions to WS-Security, specifically dealing with the issuing, renewing, and validating of security tokens, as well as with ways to establish, assess the presence of, and broker trust relationships between participants in a secure message exchange. You can reduce network latency by using a background thread for networking. Supports Azure now.  Text and Printing Improved text clarity that enables better text rendering. Multi-column text flow, Character tracking and leading support, and full OpenType font support.  Includes a new Postscript Vector Printing API that provides control over what you print . Pivot functionality baked into Silverlight 5 SDK. Graphics Immediate mode graphics support that will enable you to use the GPU and 3D graphics supports. Take a look at what was shown in the demos below. 1) 3D view of the Earth – not really a real-world application though. A doctor’s portal. This demo really stood out for me as it shows what we can do with the 3D / GPU support. Out of Browser OOB applications can now create and manage childwindows as shown in the screenshot below.  Trusted OOB applications can use P/Invoke to call Win32 APIs and unmanaged libraries.  Enterprise Group Policy Support allow enterprises to lock down or up the sandbox capabilities of Silverlight 5 applications. In this demo, he tore the “notes” off of the application and it appeared in a new window. See the black arrow below. In this demo, he connected a USB Device which fired off a local Win32 application that provided the data off the USB stick to Silverlight. Another demo of a Silverlight 5 application exporting data right into Excel running inside of browser. Testing They demoed Coded UI, which is available now in the Visual Studio Feature Pack 2. This will allow you to create automated testing without writing any code manually. Performance: Microsoft has worked to improve the Silverlight startup time. Silverlight 5 provides 64-bit browser support.  Silverlight 5 also provides IE9 Hardware acceleration.   I am looking forward to Silverlight 5 and I hope you are too. Thanks for reading and I hope you visit again soon.  Subscribe to my feed CodeProject

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• An Alphabet of Eponymous Aphorisms, Programming Paradigms, Software Sayings, Annoying Alliteration

  - by Brian Schroer

  Malcolm Anderson blogged about “Einstein’s Razor” yesterday, which reminded me of my favorite software development “law”, the name of which I can never remember. It took much Wikipedia-ing to find it (Hofstadter’s Law – see below), but along the way I compiled the following list: Amara’s Law: We tend to overestimate the effect of a technology in the short run and underestimate the effect in the long run. Brook’s Law: Adding manpower to a late software project makes it later. Clarke’s Third Law: Any sufficiently advanced technology is indistinguishable from magic. Law of Demeter: Each unit should only talk to its friends; don't talk to strangers. Einstein’s Razor: “Make things as simple as possible, but not simpler” is the popular paraphrase, but what he actually said was “It can scarcely be denied that the supreme goal of all theory is to make the irreducible basic elements as simple and as few as possible without having to surrender the adequate representation of a single datum of experience”, an overly complicated quote which is an obvious violation of Einstein’s Razor. (You can tell by looking at a picture of Einstein that the dude was hardly an expert on razors or other grooming apparati.) Finagle's Law of Dynamic Negatives: Anything that can go wrong, will—at the worst possible moment. - O'Toole's Corollary: The perversity of the Universe tends towards a maximum. Greenspun's Tenth Rule: Any sufficiently complicated C or Fortran program contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Common Lisp. (Morris’s Corollary: “…including Common Lisp”) Hofstadter's Law: It always takes longer than you expect, even when you take into account Hofstadter's Law. Issawi’s Omelet Analogy: One cannot make an omelet without breaking eggs - but it is amazing how many eggs one can break without making a decent omelet. Jackson’s Rules of Optimization: Rule 1: Don't do it. Rule 2 (for experts only): Don't do it yet. Kaner’s Caveat: A program which perfectly meets a lousy specification is a lousy program. Liskov Substitution Principle (paraphrased): Functions that use pointers or references to base classes must be able to use objects of derived classes without knowing it Mason’s Maxim: Since human beings themselves are not fully debugged yet, there will be bugs in your code no matter what you do. Nils-Peter Nelson’s Nil I/O Rule: The fastest I/O is no I/O.    Occam's Razor: The simplest explanation is usually the correct one. Parkinson’s Law: Work expands so as to fill the time available for its completion. Quentin Tarantino’s Pie Principle: “…you want to go home have a drink and go and eat pie and talk about it.” (OK, he was talking about movies, not software, but I couldn’t find a “Q” quote about software. And wouldn’t it be cool to write a program so great that the users want to eat pie and talk about it?) Raymond’s Rule: Computer science education cannot make anybody an expert programmer any more than studying brushes and pigment can make somebody an expert painter.  Sowa's Law of Standards: Whenever a major organization develops a new system as an official standard for X, the primary result is the widespread adoption of some simpler system as a de facto standard for X. Turing’s Tenet: We shall do a much better programming job, provided we approach the task with a full appreciation of its tremendous difficulty, provided that we respect the intrinsic limitations of the human mind and approach the task as very humble programmers.  Udi Dahan’s Race Condition Rule: If you think you have a race condition, you don’t understand the domain well enough. These rules didn’t exist in the age of paper, there is no reason for them to exist in the age of computers. When you have race conditions, go back to the business and find out actual rules. Van Vleck’s Kvetching: We know about as much about software quality problems as they knew about the Black Plague in the 1600s. We've seen the victims' agonies and helped burn the corpses. We don't know what causes it; we don't really know if there is only one disease. We just suffer -- and keep pouring our sewage into our water supply. Wheeler’s Law: All problems in computer science can be solved by another level of indirection... Except for the problem of too many layers of indirection. Wheeler also said “Compatibility means deliberately repeating other people's mistakes.”. The Wrong Road Rule of Mr. X (anonymous): No matter how far down the wrong road you've gone, turn back. Yourdon’s Rule of Two Feet: If you think your management doesn't know what it's doing or that your organisation turns out low-quality software crap that embarrasses you, then leave. Zawinski's Law of Software Envelopment: Every program attempts to expand until it can read mail. Zawinski is also responsible for “Some people, when confronted with a problem, think 'I know, I'll use regular expressions.' Now they have two problems.” He once commented about X Windows widget toolkits: “Using these toolkits is like trying to make a bookshelf out of mashed potatoes.”

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• HTML5 and Visual Studio 2010

  - by Harish Ranganathan

  All of us work with Visual Studio (or the free Visual Web Developer Express Edition) for developing web applications targeting ASP.NET / ASP.NET MVC or Silverlight etc.,  Over the years, Visual Studio has grown to a great extent.  From being a simple limited functionality tool in VS.NET 2002 to the multi-faceted, MEF driven Visual Studio 2010, it has come a long way.  And as much as Visual Studio supports rapid web development by generating HTML mark up, it also added intellisense for some of the HTML specifications that one has otherwise monotonously type every time.  Ex.- In Visual Studio 2010, one can just type the angular bracket “<” and then the first keyword “h” or “x” for html or xhtml respectively and then press tab twice and it would render the entire markup required for XHTML or HTML 1.0/1.1 strict/transitional and the fully qualified W3C URL. The same holds good for specifying HTML type declaration.  Now, the difference between HTML and XHTML has been discussed in detail already, though, if you are interested to know, you can read it from http://www.w3schools.com/xhtml/xhtml_html.asp But, the industry trend or the buzz around is HTML5.  With browsers like IE9 Beta, Google Chrome, Firefox 4 etc., supporting HTML5 standards big time, everyone wants to start developing HTML5 based websites. VS developers (like me) often get the question around when would VS start supporting HTML5.  VS 2010 was released last year and HTML5 is still specifications under development.  Clearly, with the timelines we started developing Visual Studio (way back in 2008), HTML5 specs were almost non-existent.  Even today, the HTML5 body recommends not to fully depend on the entire mark up set as they are still under development specs and might change in the future. However, with Visual Studio 2010 SP1 beta, there is quite a bit of support for HTML5 based web development.  In fact, one of my colleagues pointed out that SP1 beta’s major enhancement is its ability to support HTML5 tags and even add server mode to them. Lets look at the existing validation schema available in Visual Studio (Tools – Options – Validation) This is before installing Visual Studio 2010 SP1 Beta.  Clearly, the validation options are restricted to HTML 4.01 and XHTML 1.1 transitional and below. Also, lets consider using some of the new HTML5 input type elements.  (I found out this, just today from my friend, also an, ASP.NET team member) <input type=”email”> is one of the new input type elements according to the HTML5 specification.  Now, this works well if you type it as is  in Visual Studio and the page renders without any issue (since the default behaviour is, if there is an “undefined” type specified to input tag, it would fall back on the default mode, which is text. The moment you add <input type=”email” runat=”server” >, you get an error Naturally you don’t get intellisense support as well for these new tags.  Once you install Visual Studio 2010 Service Pack 1 Beta from here (it takes a while so you need to be patient for the installation to complete), you will start getting additional Validation templates for HTML5, as below:- Once you set this, you can start using HTML5 elements in your web page without getting errors/warnings.  Look at the screen shot below, for the new “video” tag which is showing up in intellisense (video is a part of the new HTML5 specifications)     note that, you still need to hook up the <!DOCTYPE html /> on the top manually as it doesn’t change automatically  (from the default XHTML 1.0 strict) when you create a new page. Also, the new input type tags in HTML5 are also supported One, can also use the <asp:TextBox type=”email” which would in turn generate the <input type=”email”> markup when the page is rendered.  In fact, as of SP1 beta, this is the only way to put the new input type tags with the runat=”server” attribute (otherwise you will get the parser error mentioned above.  This issue would be fixed by the final release of SP1 beta) Going further, there may be more support for having server tags for some of the common HTML5 elements, but this is work in progress currently. So, other than not having runat=”server” support for the new HTML5  input tags, you can pretty much build and target HTML5 websites with Visual Studio 2010 SP1 Beta, today.  For those who are running Visual Studio 2008, you also have the “HTML5 intellisense for Visual Studio 2010 and 2008” available for download, from http://visualstudiogallery.msdn.microsoft.com/d771cbc8-d60a-40b0-a1d8-f19fc393127d/ Note that, if you are running Visual Studio 2010, the recommended approach is to install the SP1 beta which would be the way forward for HTML5 support in Visual Studio. Of course, you need to test these on a browser supporting HTML5 such as IE9 Beta or Chrome or FireFox 4.  You can download IE9 Beta from here You can also follow the Visual Web Developer Team Blog for more updates on the stuff they are building. Cheers !!!

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• Calling All Agile Customers-Share Your Stories at the Upcoming PLM Summit

  - by Terri Hiskey

  Now that we've closed the door on another Oracle OpenWorld, planning is in full swing for the next PLM Summit, taking place February 4-6, 2013 in San Francisco, in conjunction with the Oracle Value Chain Summit. This event is a must-attend for all Agile PLM customers. We will be holding five tracks with over forty Agile PLM-focused sessions covering a range of topics and industries. If you'd like to be notified once registration is live for this event, be sure to sign up at www.oracle.com/goto/vcs. CALL FOR PRESENTATIONS: We are looking for some fresh, new customer stories to share with attendees. Read below for descriptions of the five tracks, and the suggested topics that we'd like to hear from customers. If you are interested in presenting at the PLM Summit (and getting a FREE pass to attend if your presentation is accepted!) send me an email at terri.hiskey-AT-oracle.com with: Your proposed session title and the track your session fits into 3-5 bullets of takeaways that attendees will get from your presentation Your complete contact information including name, title, company, telephone number and email The deadline for this call for presentations is Thursday, November 15, so get your submission in soon! PLM Track #1:  Product Insights and Best Practices This track will provide executive attendees and line of business managers with an overview of how Agile PLM has been deployed and used at customers to enable and manage critical product-related business processes including enterprise quality and supplier management, compliance, product cost management, portfolio management, commercialization and software lifecycle management. These sessions will also provide details around how to manage the development and rollout of the solutions and how to achieve and track value. Possible session topics: Software Lifecycle Management Enterprise Quality Management New Product Development Integrated Business Planning ECO effectivity planning Rapid Commercialization             Manage the Design to Release Process for Complex Configured Products PLM for Life Sciences Companies I (Compliant Data Set) PLM for Life Sciences Companies II (eMDR, UDI) Discrete CPG – Private Label Mgmt Cost Management and Strategic Sourcing IP Mgmt in the Semiconductor Industry Implementing the Enterprise Training Record using Agile PLM PLM Track #2: Product Deep Dives & Demos This track is aimed at line of business  and IT managers who would like to understand the benefits of expanding their PLM footprint. The sessions in this track will provide attendees with an up-close and in-depth look Agile PLM’s newer and exciting applications, including analytics and innovation management, and will detail features and functionality that are available in the latest version of Agile PLM Possible session topics: Oracle Product Lifecycle Analytics Integrating PLM with Engineering and Supply Chain Systems Streamline PLM Design to Manufacturing Processes with AutoVue Visualization Solutions         Achieve Environmental Compliance (REACH and ROHS) with Agile Product Governance & Compliance PIM Deep Dive Achieving Integrated Change Control with Agile PLM and E-Business Suite Deploying PLM at Small and Midsize Enterprises Enhancing Oracle PQM w/APQP and 8D functionality Advanced Roles and Privileges – Enabling ITAR Model Unit Effectivity Implementing REACH with 9.3.2 Deploying Job Functions, Functional Teams in 9.3.2 to Improve Your Approval Matrix PLM Track #3: Administration & Integrations This track will provide sessions for Agile administrators, managers and daily Agile PLM users who are preparing to upgrade or looking to extend the use of their current PLM implementation through AIA and process extensions. It will include deeper conversation about Agile PLM features and best practices on managing an Agile PLM infrastructure. Possible session topics: Expand the Value of your Agile Investment with Innovative Process Extension Ideas Ensuring Implementation & Upgrade Success Ensure the Integrity and Accuracy of Product Data Across the Enterprise              Maximize the Benefits of an Integrated Architecture with AIA Integrating your PLM Implementation with ERP               Infrastructure Optimization Expanding Your PLM Implementation PLM Administrator Open Forum Q&A/Discussion FDA Validation Best Practices Best Practices for Managing a large Agile Deployment: Clustering, Load Balancing and Firewalls PLM Track #4: Agile PLM for Process This track is aimed at attendees interested in or currently using Agile PLM for Process. The sessions in this track will go over new features and functionality available in the newest version of PLM for Process and will give attendees an overview on how PLM for Process is being used to manage critical business processes such as formulation, recipe and specification management Possible session topics: PLM for Process Strategy, Roadmap and Update New Product Development and Introduction Effective Product Supplier Collaboration             Leverage Agile Formulation and Compliance to Manage Cost, Compliance, Quality, Labeling and Nutrition Menu Management Innovation Data Management Food Safety/ Introduction of P4P Quality Mgmt PLM Track #5: Agile PLM and Innovation Management This track consists of five sessions, and is for attendees interested in learning more about Oracle’s Agile Innovation Management, an exciting new addition to the Agile PLM application family that redefines the industry’s scope of product lifecycle management. Oracle’s innovation solutions enable companies to collaborate in a focused way among various functional groups (marketing, sales, operations, engineering/R&D and sourcing), combining insights of customer needs/requirements, competition, available technologies, alternate design scenarios and portfolio constraints to deliver what customers truly value. The results are better products, higher margins, greater efficiencies, more satisfied customers and the increased ability to continuously innovate. Possible session topics: Product Innovation Management Solution Overview Product Requirements & Ideation Management Concept Design Management Product Lifecycle Portfolio Management Innovation as a Competitive Differentiator

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• How does one find out which application is associated with an indicator icon?

  - by Amos Annoy

  It is trivial to do this in Ubuntu 10.04. The question is specific to Ubuntu 12.04. some pertinent references (src: answer to What is the difference between indicators and a system tray?: Here is the documentation for indicators: Application indicators | Ubuntu App Developer libindicate Reference Manual libappindicator Reference Manual also DesktopExperienceTeam/ApplicationIndicators - Ubuntu Wiki ref: How can the application that makes an indicator icon be identified? bookmark: How does one find out which application is associated with an indicator icon in Ubuntu 12.04? is a serious question for reasons & problems outlined below and for which a significant investment has been made and is necessary for remedial purposes. reviewing refs. to find an orchestrated resolution ... (an indicator ap. indicator maybe needed) This has nothing to do (does it?) with right click. How can an indicator's icon in Ubuntu 12.04 be matched with the program responsible for it's manifestation on the top panel? A list of running applications can include all processes using System Monitor. How is the correct matching process found for an indicator? How are the sub-indicator applications identified? These are the aps associated with the components of an indicators drop-down menu. (This was to be a separate question and quite naturally follows up the progression. It is included here as it is obvious there is no provisioning to track down offending either sub or indicator aps. easily.) (The examination of SM points out a rather poignant factor in the faster battery depletion and shortened run time - the ambient quiescent CPU rate in 12.04 is now well over 20% when previously, in 10.04, it was well under 10%, between 5% and 7%! - the huge inordinate cpu overhead originates from Xorg and compiz - after booting the system, only SM is run and All Processes are selected, sorting on %CPU - switching between Resources and Processes profiles the execution overhead problem - running another ap like gedit "Text Editor" briefly gives it CPU priority - going back to S&M several aps. are at the top of the list in order: gnome-system-monitor as expected, then: Xorg, compiz, unity-panel-service, hud-service, with dbus-daemon and kworker/x:y's mixed in with some expected daemons and background tasks like nm-applet - not only do Xorg and compiz require excessive CPU time but their entourage has to come along too! further exacerbating the problem - our compute bound tasks no longer work effectively in the field - reduced battery life, reduced CPU time for custom ap.s etc. - and all this precipitated from an examination of what is going on with the battery ap. indicator - this was and is not a flippant, rhetorical or idle musing but has consequences for the credible deployment of 12.04 to reduce the negative impact of its overhead in a production environment) (I have a problem with the battery indicator - it sometimes has % and other times hh:mm - it is necessary to know the ap. & v. to get more info on controlling same. ditto: There are issues with other indicator aps.: NM vs. iwlist/iwconfig conflict, BT ap. vs RF switch, Battery ap. w/ no suspend/sleep for poor battery runtime, ... the list goes on) Details from: How can I find Application Indicator ID's? suggests looking at: file:///usr/share/indicator-application/ordering-override.keyfile [Ordering Index Overrides] nm-applet=1 gnome-power-manager=2 ibus=3 gst-keyboard-xkb=4 gsd-keyboard-xkb=5 which solves the battery ap. identification, and presumably nm is NetworkManager for the rf icon, but the envelope, blue tooth and speaker indicator aps. are still a mystery. (Also, the ordering is not correlated.) Mind you, it was simple in the past to simply right click to get the About option to find the ap. & v. info. browsing around and about: file:///usr/share/indicator-application/ordering-override.keyfile examined: file:///usr/share/indicators file:///usr/share/indicators/messages/applications/ ... perhaps?/presumably? the information sought may be buried in file:///usr/share/indicators A reference in the comments was given to: What is the difference between indicators and a system tray? quoting from that source ... Unfortunately desktop indicators are not well documented yet: I couldn't find any specification doc ... Well ... the actual document https://wiki.ubuntu.com/DesktopExperienceTeam/ApplicationIndicators#Summary does not help much but it's existential information provides considerable insight ...

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• Making your WCF Web Apis to speak in multiple languages

  - by cibrax

  One of the key aspects of how the web works today is content negotiation. The idea of content negotiation is based on the fact that a single resource can have multiple representations, so user agents (or clients) and servers can work together to chose one of them. The http specification defines several “Accept” headers that a client can use to negotiate content with a server, and among all those, there is one for restricting the set of natural languages that are preferred as a response to a request, “Accept-Language”. For example, a client can specify “es” in this header for specifying that he prefers to receive the content in spanish or “en” in english. However, there are certain scenarios where the “Accept-Language” header is just not enough, and you might want to have a way to pass the “accepted” language as part of the resource url as an extension. For example, http://localhost/ProductCatalog/Products/1.es” returns all the descriptions for the product with id “1” in spanish. This is useful for scenarios in which you want to embed the link somewhere, such a document, an email or a page.  Supporting both scenarios, the header and the url extension, is really simple in the new WCF programming model. You only need to provide a processor implementation for any of them. Let’s say I have a resource implementation as part of a product catalog I want to expose with the WCF web apis. [ServiceContract][Export]public class ProductResource{ IProductRepository repository;  [ImportingConstructor] public ProductResource(IProductRepository repository) { this.repository = repository; }  [WebGet(UriTemplate = "{id}")] public Product Get(string id, HttpResponseMessage response) { var product = repository.GetById(int.Parse(id)); if (product == null) { response.StatusCode = HttpStatusCode.NotFound; response.Content = new StringContent(Messages.OrderNotFound); }  return product; }} The Get method implementation in this resource assumes the desired culture will be attached to the current thread (Thread.CurrentThread.Culture). Another option is to pass the desired culture as an additional argument in the method, so my processor implementation will handle both options. This method is also using an auto-generated class for handling string resources, Messages, which is available in the different cultures that the service implementation supports. For example, Messages.resx contains “OrderNotFound”: “Order Not Found” Messages.es.resx contains “OrderNotFound”: “No se encontro orden” The processor implementation bellow tackles the first scenario, in which the desired language is passed as part of the “Accept-Language” header. public class CultureProcessor : Processor<HttpRequestMessage, CultureInfo>{ string defaultLanguage = null;  public CultureProcessor(string defaultLanguage = "en") { this.defaultLanguage = defaultLanguage; this.InArguments[0].Name = HttpPipelineFormatter.ArgumentHttpRequestMessage; this.OutArguments[0].Name = "culture"; }  public override ProcessorResult<CultureInfo> OnExecute(HttpRequestMessage request) { CultureInfo culture = null; if (request.Headers.AcceptLanguage.Count > 0) { var language = request.Headers.AcceptLanguage.First().Value; culture = new CultureInfo(language); } else { culture = new CultureInfo(defaultLanguage); }  Thread.CurrentThread.CurrentCulture = culture; Messages.Culture = culture;  return new ProcessorResult<CultureInfo> { Output = culture }; }}   As you can see, the processor initializes a new CultureInfo instance with the value provided in the “Accept-Language” header, and set that instance to the current thread and the auto-generated resource class with all the messages. In addition, the CultureInfo instance is returned as an output argument called “culture”, making possible to receive that argument in any method implementation   The following code shows the implementation of the processor for handling languages as url extensions.   public class CultureExtensionProcessor : Processor<HttpRequestMessage, Uri>{ public CultureExtensionProcessor() { this.OutArguments[0].Name = HttpPipelineFormatter.ArgumentUri; }  public override ProcessorResult<Uri> OnExecute(HttpRequestMessage httpRequestMessage) { var requestUri = httpRequestMessage.RequestUri.OriginalString;  var extensionPosition = requestUri.LastIndexOf(".");  if (extensionPosition > -1) { var extension = requestUri.Substring(extensionPosition + 1);  var query = httpRequestMessage.RequestUri.Query;  requestUri = string.Format("{0}?{1}", requestUri.Substring(0, extensionPosition), query); ;  var uri = new Uri(requestUri);  httpRequestMessage.Headers.AcceptLanguage.Clear();  httpRequestMessage.Headers.AcceptLanguage.Add(new StringWithQualityHeaderValue(extension));  var result = new ProcessorResult<Uri>();  result.Output = uri;  return result; }  return new ProcessorResult<Uri>(); }} The last step is to inject both processors as part of the service configuration as it is shown bellow, public void RegisterRequestProcessorsForOperation(HttpOperationDescription operation, IList<Processor> processors, MediaTypeProcessorMode mode){ processors.Insert(0, new CultureExtensionProcessor()); processors.Add(new CultureProcessor());} Once you configured the two processors in the pipeline, your service will start speaking different languages :). Note: Url extensions don’t seem to be working in the current bits when you are using Url extensions in a base address. As far as I could see, ASP.NET intercepts the request first and tries to route the request to a registered ASP.NET Http Handler with that extension. For example, “http://localhost/ProductCatalog/products.es” does not work, but “http://localhost/ProductCatalog/products/1.es” does.

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• Subterranean IL: Constructor constraints

  - by Simon Cooper

  The constructor generic constraint is a slightly wierd one. The ECMA specification simply states that it: constrains [the type] to being a concrete reference type (i.e., not abstract) that has a public constructor taking no arguments (the default constructor), or to being a value type. There seems to be no reference within the spec to how you actually create an instance of a generic type with such a constraint. In non-generic methods, the normal way of creating an instance of a class is quite different to initializing an instance of a value type. For a reference type, you use newobj: newobj instance void IncrementableClass::.ctor() and for value types, you need to use initobj: .locals init ( valuetype IncrementableStruct s1 ) ldloca 0 initobj IncrementableStruct But, for a generic method, we need a consistent method that would work equally well for reference or value types. Activator.CreateInstance<T> To solve this problem the CLR designers could have chosen to create something similar to the constrained. prefix; if T is a value type, call initobj, and if it is a reference type, call newobj instance void !!0::.ctor(). However, this solution is much more heavyweight than constrained callvirt. The newobj call is encoded in the assembly using a simple reference to a row in a metadata table. This encoding is no longer valid for a call to !!0::.ctor(), as different constructor methods occupy different rows in the metadata tables. Furthermore, constructors aren't virtual, so we would have to somehow do a dynamic lookup to the correct method at runtime without using a MethodTable, something which is completely new to the CLR. Trying to do this in IL results in the following verification error: newobj instance void !!0::.ctor() [IL]: Error: Unable to resolve token. This is where Activator.CreateInstance<T> comes in. We can call this method to return us a new T, and make the whole issue Somebody Else's Problem. CreateInstance does all the dynamic method lookup for us, and returns us a new instance of the correct reference or value type (strangely enough, Activator.CreateInstance<T> does not itself have a .ctor constraint on its generic parameter): .method private static !!0 CreateInstance<.ctor T>() { call !!0 [mscorlib]System.Activator::CreateInstance<!!0>() ret } Going further: compiler enhancements Although this method works perfectly well for solving the problem, the C# compiler goes one step further. If you decompile the C# version of the CreateInstance method above: private static T CreateInstance() where T : new() { return new T(); } what you actually get is this (edited slightly for space & clarity): .method private static !!T CreateInstance<.ctor T>() { .locals init ( [0] !!T CS$0$0000, [1] !!T CS$0$0001 ) DetectValueType: ldloca.s 0 initobj !!T ldloc.0 box !!T brfalse.s CreateInstance CreateValueType: ldloca.s 1 initobj !!T ldloc.1 ret CreateInstance: call !!0 [mscorlib]System.Activator::CreateInstance<T>() ret } What on earth is going on here? Looking closer, it's actually quite a clever performance optimization around value types. So, lets dissect this code to see what it does. The CreateValueType and CreateInstance sections should be fairly self-explanatory; using initobj for value types, and Activator.CreateInstance for reference types. How does the DetectValueType section work? First, the stack transition for value types: ldloca.s 0 // &[!!T(uninitialized)] initobj !!T // ldloc.0 // !!T box !!T // O[!!T] brfalse.s // branch not taken When the brfalse.s is hit, the top stack entry is a non-null reference to a boxed !!T, so execution continues to to the CreateValueType section. What about when !!T is a reference type? Remember, the 'default' value of an object reference (type O) is zero, or null. ldloca.s 0 // &[!!T(null)] initobj !!T // ldloc.0 // null box !!T // null brfalse.s // branch taken Because box on a reference type is a no-op, the top of the stack at the brfalse.s is null, and so the branch to CreateInstance is taken. For reference types, Activator.CreateInstance is called which does the full dynamic lookup using reflection. For value types, a simple initobj is called, which is far faster, and also eliminates the unboxing that Activator.CreateInstance has to perform for value types. However, this is strictly a performance optimization; Activator.CreateInstance<T> works for value types as well as reference types. Next... That concludes the initial premise of the Subterranean IL series; to cover the details of generic methods and generic code in IL. I've got a few other ideas about where to go next; however, if anyone has any itching questions, suggestions, or things you've always wondered about IL, do let me know.

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• Subscribable World Cup 2010 Calendar

  - by jamiet

  I bang on quite a lot on this blog about ways in which data can get published over the web and one of the most interesting ways, in my opinion, of publishing data in a structured manner that is well understood is to use the iCalendar specification. There isn’t much information in the world that doesn’t have some concept of “when” so iCalendar is a great way of distributing that information. You have probably used iCalendar at some point without even knowing about it. All files with a .ics suffix are iCalendar format files and that is why you can happily import them into Outlook, Hotmail Calendar, Google Calendar etc… where they can be parsed and have the semantic data (when, where and who) extracted from them. Importing of iCalendar format data is really only half the trick though; in my opinion the real value of iCalendar-formatted calendar is the ability to subscribe to them. Subscribing has a simple benefit over importing but that single benefit is of massive importance: a subscriber to an iCalendar calendar can periodically check to see if any updates have been made and, if they have, automatically update the local copy. The real benefit to the user is the productivity gain – a single update to an iCalendar means that all subscribers are automatically made aware of the change and there is zero effort on the part of the subscriber; as my former colleague Howard van Rooijen is fond of saying, “work smarter not harder” – nowhere is this edict more ably demonstrated than subscribing versus importing of calendars. If you want to read some more thoughts about iCalendar then go and read my past blog post Calendar syndication - My big hope for 2009's breakthrough technology or better still go and seek out Jon Udell who speaks very authoritatively on the issue of iCalendar. With this subject of iCalendar on my mind I was interested to discover (via Steve Clayton’s blog post Download the world cup fixtures) that the BBC had made a .ics file available containing all of the matches in the upcoming World Cup. As you can probably guess this was a file that was made available so that it could be imported into your calendar of choice. It had one obvious downside though, right now nobody knows who is going to be playing in the knock-out stages so the calendar looks like this: with no teams being named after 25th June. How much more useful would this calendar have been if the BBC had made it possible to subscribe to the calendar instead, thus the calendar could be updated with the teams for the knock out stages when they are known and every subscriber would have a permanently up-to-date record of all the fixtures in their calendar. Better still, the calendar could be updated with match results as well or perhaps even post a match report from the BBC sport pages; when calendars are made subscribable a sea of opportunity opens up for distribution of information. So with that in mind I have decided to go one better than the BBC. I have imported their .ics into a brand new Hotmail calendar and made it publicly available at the following URLs: HTML http://cid-dc1ed121af0476be.calendar.live.com/calendar/World+Cup+2010/index.html iCalendar webcal://cid-dc1ed121af0476be.calendar.live.com/calendar/World+Cup+2010/calendar.ics The link you’re really interested in is the second one - click on that and it should open up in your calendar software of choice. Or, if you want to view it in an online calendar such as Hotmail Calendar or Google Calendar, copy and paste that URL into the appropriate place. Some people have told me they’re having trouble with the iCalendar link in which case hit the HTML link and then click “View ICS” at the resultant web page: I shall endeavour to keep the calendar updated throughout the World Cup and even if I don’t you’re no worse off than if you had imported the BBC’s .ics file so why not give it a try? If I do keep it up to date then you will have a permanent record of the 2010 World Cup available in your calendar. Forever. If you have your calendar synced to your smartphone then you’ll be carrying match reports around with you without you having to do a single thing. Surely that’s worth a quick click isn’t it?   If you have any thoughts let me have them in the comments below. Thanks for reading. @Jamiet Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Blog Buzz - Devoxx 2011

  - by Janice J. Heiss

  Some day I will make it to Devoxx – for now, I’m content to vicariously follow the blogs of attendees and pick up on what’s happening.  I’ve been doing more blog "fishing," looking for the best commentary on 2011 Devoxx. There’s plenty of food for thought – and the ideas are not half-baked.The bloggers are out in full, offering useful summaries and commentary on Devoxx goings-on.Constantin Partac, a Java developer and a member of Transylvania JUG, a community from Cluj-Napoca/Romania, offers an excellent summary of the Devoxx keynotes. Here’s a sample:“Oracle Opening Keynote and JDK 7, 8, and 9 Presentation•    Oracle is committed to Java and wants to provide support for it on any device.•    JSE 7 for Mac will be released next week.•    Oracle would like Java developers to be involved in JCP, to adopt a JSR and to attend local JUG meetings.•    JEE 7 will be released next year.•    JEE 7 is focused on cloud integration, some of the features are already implemented in glassfish 4 development branch.•    JSE 8 will be release in summer of 2013 due to “enterprise community request” as they can not keep the pace with an 18    month release cycle.•    The main features included in JSE8 are lambda support, project Jigsaw, new Date/Time API, project Coin++ and adding   support for sensors. JSE 9 probably will focus on some of these features:1.    self tuning JVM2.    improved native language integration3.    processing enhancement for big data4.    reification (adding runtime class type info for generic types)5.    unification of primitive and corresponding object classes6.    meta-object protocol in order to use type and methods define in other JVM languages7.    multi-tenancy8.    JVM resource management” Thanks Constantin! Ivan St. Ivanov, of SAP Labs Bulgaria, also commented on the keynotes with a different focus.  He summarizes Henrik Stahl’s look ahead to Java SE 8 and JavaFX 3.0; Cameron Purdy on Java EE and the cloud; celebrated Java Champion Josh Bloch on what’s good and bad about Java; Mark Reinhold’s quick look ahead to Java SE 9; and Brian Goetz on lambdas and default methods in Java SE 8. Here’s St. Ivanov’s account of Josh Bloch’s comments on the pluses of Java:“He started with the virtues of the platform. To name a few:    Tightly specified language primitives and evaluation order – int is always 32 bits and operations are executed always from left  to right, without compilers messing around    Dynamic linking – when you change a class, you need to recompile and rebuild just the jar that has it and not the whole application    Syntax  similarity with C/C++ – most existing developers at that time felt like at home    Object orientations – it was cool at that time as well as functional programming is today    It was statically typed language – helps in faster runtime, better IDE support, etc.    No operator overloading – well, I’m not sure why it is good. Scala has it for example and that’s why it is far better for defining DSLs. But I will not argue with Josh.”It’s worth checking out St. Ivanov’s summary of Bloch’s views on what’s not so great about Java as well. What's Coming in JAX-RS 2.0Marek Potociar, Principal Software Engineer at Oracle and currently specification lead of Java EE RESTful web services API (JAX-RS), blogged on his talk about what's coming in JAX-RS 2.0, scheduled for final release in mid-2012.  Here’s a taste:“Perhaps the most wanted addition to the JAX-RS is the Client API, that would complete the JAX-RS story, that is currently server-side only. In JAX-RS 2.0 we are adding a completely interface-based and fluent client API that blends nicely in with the existing fluent response builder pattern on the server-side. When we started with the client API, the first proposal contained around 30 classes. Thanks to the feedback from our Expert Group we managed to reduce the number of API classes to 14 (2 of them being exceptions)! The resulting is compact while at the same time we still managed to create an API that reflects the method invocation context flow (e.g. once you decide on the target URI and start setting headers on the request, your IDE will not try to offer you a URI setter in the code completion). This is a subtle but very important usability aspect of an API…” Obviously, Devoxx is a great Java conference, one that is hitting this year at a time when much is brewing in the platform and beginning to be anticipated.

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• Session Report - Java on the Raspberry Pi

  - by Janice J. Heiss

  On mid-day Wednesday, the always colorful Oracle Evangelist Simon Ritter demonstrated Java on the Raspberry Pi at his session, “Do You Like Coffee with Your Dessert?”. The Raspberry Pi consists of a credit card-sized single-board computer developed in the UK with the intention of stimulating the teaching of basic computer science in schools. “I don't think there is a single feature that makes the Raspberry Pi significant,” observed Ritter, “but a combination of things really makes it stand out. First, it's $35 for what is effectively a completely usable computer. You do have to add a power supply, SD card for storage and maybe a screen, keyboard and mouse, but this is still way cheaper than a typical PC. The choice of an ARM (Advanced RISC Machine and Acorn RISC Machine) processor is noteworthy, because it avoids problems like cooling (no heat sink or fan) and can use a USB power brick. When you add in the enormous community support, it offers a great platform for teaching everyone about computing.”Some 200 enthusiastic attendees were present at the session which had the feel of Simon Ritter sharing a fun toy with friends. The main point of the session was to show what Oracle was doing to support Java on the Raspberry Pi in a way that is entertaining and fun. Ritter pointed out that, in addition to being great for teaching, it’s an excellent introduction to the ARM architecture, and runs well with Java and will get better once it has official hard float support. The possibilities are vast.Ritter explained that the Raspberry Pi Project started in 2006 with the goal of devising a computer to inspire children; it drew inspiration from the BBC Micro literacy project of 1981 that produced a series of microcomputers created by the Acorn Computer company. It was officially launched on February 29, 2012, with a first production of 10,000 boards. There were 100,000 pre-orders in one day; currently about 4,000 boards are produced a day. Ritter described the specification as follows:* CPU: ARM 11 core running at 700MHz Broadcom SoC package Can now be overclocked to 1GHz (without breaking the warranty!) * Memory: 256Mb* I/O: HDMI and composite video 2 x USB ports (Model B only) Ethernet (Model B only) Header pins for GPIO, UART, SPI and I2C He took attendees through a brief history of ARM Architecture:* Acorn BBC Micro (6502 based) Not powerful enough for Acorn’s plans for a business computer * Berkeley RISC Project UNIX kernel only used 30% of instruction set of Motorola 68000 More registers, less instructions (Register windows) One chip architecture to come from this was… SPARC * Acorn RISC Machine (ARM) 32-bit data, 26-bit address space, 27 registers First machine was Acorn Archimedes * Spin off from Acorn, Advanced RISC MachinesNext he presented its features:* 32-bit RISC Architecture–  ARM accounts for 75% of embedded 32-bit CPUs today– 6.1 Billion chips sold last year (zero manufactured by ARM)* Abstract architecture and microprocessor core designs– Raspberry Pi is ARM11 using ARMv6 instruction set* Low power consumption– Good for mobile devices– Raspberry Pi can be powered from 700mA 5V only PSU– Raspberry Pi does not require heatsink or fanHe described the current ARM Technology:* ARMv6– ARM 11, ARM Cortex-M* ARMv7– ARM Cortex-A, ARM Cortex-M, ARM Cortex-R* ARMv8 (Announced)– Will support 64-bit data and addressingHe next gave the Java Specifics for ARM: Floating point operations* Despite being an ARMv6 processor it does include an FPU– FPU only became standard as of ARMv7* FPU (Hard Float, or HF) is much faster than a software library* Linux distros and Oracle JVM for ARM assume no HF on ARMv6– Need special build of both– Raspbian distro build now available– Oracle JVM is in the works, release date TBDNot So RISCPerformance Improvements* DSP Enhancements* Jazelle* Thumb / Thumb2 / ThumbEE* Floating Point (VFP)* NEON* Security Enhancements (TrustZone)He spent a few minutes going over the challenges of using Java on the Raspberry Pi and covered:* Sound* Vision * Serial (TTL UART)* USB* GPIOTo implement sound with Java he pointed out:* Sound drivers are now included in new distros* Java Sound API– Remember to add audio to user’s groups– Some bits work, others not so much* Playing (the right format) WAV file works* Using MIDI hangs trying to open a synthesizer* FreeTTS text-to-speech– Should work once sound works properlyHe turned to JavaFX on the Raspberry Pi:* Currently internal builds only– Will be released as technology preview soon* Work involves optimal implementation of Prism graphics engine– X11?* Once the JavaFX implementation is completed there will be little of concern to developers-- It’s just Java (WORA). He explained the basis of the Serial Port:* UART provides TTL level signals (3.3V)* RS-232 uses 12V signals* Use MAX3232 chip to convert* Use this for access to serial consoleHe summarized his key points. The Raspberry Pi is a very cool (and cheap) computer that is great for teaching, a great introduction to ARM that works very well with Java and will work better in the future. The opportunities are limitless. For further info, check out, Raspberry Pi User Guide by Eben Upton and Gareth Halfacree. From there, Ritter tried out several fun demos, some of which worked better than others, but all of which were greeted with considerable enthusiasm and support and good humor (even when he ran into some glitches).  All in all, this was a fun and lively session.

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• Computer Networks UNISA - Chap 8 &ndash; Wireless Networking

  - by MarkPearl

  After reading this section you should be able to Explain how nodes exchange wireless signals Identify potential obstacles to successful transmission and their repercussions, such as interference and reflection Understand WLAN architecture Specify the characteristics of popular WLAN transmission methods including 802.11 a/b/g/n Install and configure wireless access points and their clients Describe wireless MAN and WAN technologies, including 802.16 and satellite communications The Wireless Spectrum All wireless signals are carried through the air by electromagnetic waves. The wireless spectrum is a continuum of the electromagnetic waves used for data and voice communication. The wireless spectrum falls between 9KHZ and 300 GHZ. Characteristics of Wireless Transmission Antennas Each type of wireless service requires an antenna specifically designed for that service. The service’s specification determine the antenna’s power output, frequency, and radiation pattern. A directional antenna issues wireless signals along a single direction. An omnidirectional antenna issues and receives wireless signals with equal strength and clarity in all directions The geographical area that an antenna or wireless system can reach is known as its range Signal Propagation LOS (line of sight) uses the least amount of energy and results in the reception of the clearest possible signal. When there is an obstacle in the way, the signal may… pass through the object or be obsrobed by the object or may be subject to reflection, diffraction or scattering. Reflection – waves encounter an object and bounces off it. Diffraction – signal splits into secondary waves when it encounters an obstruction Scattering – is the diffusion or the reflection in multiple different directions of a signal Signal Degradation Fading occurs as a signal hits various objects. Because of fading, the strength of the signal that reaches the receiver is lower than the transmitted signal strength. The further a signal moves from its source, the weaker it gets (this is called attenuation) Signals are also affected by noise – the electromagnetic interference) Interference can distort and weaken a wireless signal in the same way that noise distorts and weakens a wired signal. Frequency Ranges Older wireless devices used the 2.4 GHZ band to send and receive signals. This had 11 communication channels that are unlicensed. Newer wireless devices can also use the 5 GHZ band which has 24 unlicensed bands Narrowband, Broadband, and Spread Spectrum Signals Narrowband – a transmitter concentrates the signal energy at a single frequency or in a very small range of frequencies Broadband – uses a relatively wide band of the wireless spectrum and offers higher throughputs than narrowband technologies The use of multiple frequencies to transmit a signal is known as spread-spectrum technology. In other words a signal never stays continuously within one frequency range during its transmission. One specific implementation of spread spectrum is FHSS (frequency hoping spread spectrum). Another type is known as DSS (direct sequence spread spectrum) Fixed vs. Mobile Each type of wireless communication falls into one of two categories Fixed – the location of the transmitted and receiver do not move (results in energy saved because weaker signal strength is possible with directional antennas) Mobile – the location can change WLAN (Wireless LAN) Architecture There are two main types of arrangements Adhoc – data is sent directly between devices – good for small local devices Infrastructure mode – a wireless access point is placed centrally, that all devices connect with 802.11 WLANs The most popular wireless standards used on contemporary LANs are those developed by IEEE’s 802.11 committee. Over the years several distinct standards related to wireless networking have been released. Four of the best known standards are also referred to as Wi-Fi. They are…. 802.11b 802.11a 802.11g 802.11n These four standards share many characteristics. i.e. All 4 use half duplex signalling Follow the same access method Access Method 802.11 standards specify the use of CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) to access a shared medium. Using CSMA/CA before a station begins to send data on an 802.11 network, it checks for existing wireless transmissions. If the source node detects no transmission activity on the network, it waits a brief period of time and then sends its transmission. If the source does detect activity, it waits a brief period of time before checking again. The destination node receives the transmission and, after verifying its accuracy, issues an acknowledgement (ACT) packet to the source. If the source receives the ACK it assumes the transmission was successful, – if it does not receive an ACK it assumes the transmission failed and sends it again. Association Two types of scanning… Active – station transmits a special frame, known as a prove, on all available channels within its frequency range. When an access point finds the probe frame, it issues a probe response. Passive – wireless station listens on all channels within its frequency range for a special signal, known as a beacon frame, issued from an access point – the beacon frame contains information necessary to connect to the point. Re-association occurs when a mobile user moves out of one access point’s range and into the range of another. Frames Read page 378 – 381 about frames and specific 802.11 protocols Bluetooth Networks Sony Ericson originally invented the Bluetooth technology in the early 1990s. In 1998 other manufacturers joined Ericsson in the Special Interest Group (SIG) whose aim was to refine and standardize the technology. Bluetooth was designed to be used on small networks composed of personal communications devices. It has become popular wireless technology for communicating among cellular telephones, phone headsets, etc. Wireless WANs and Internet Access Refer to pages 396 – 402 of the textbook for details.

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• What's My Problem? What's Your Problem?

  - by Jacek Ziabicki

  Software installers are not made for building demo environments. I can say this much after 12 years (on and off) of supporting my fellow sales consultants with environments for software demonstrations. When we release software, we include installation programs and procedures that are designed for use by our clients – to build a production environment and a limited number of testing, training and development environments. Different Objectives Your priorities when building an environment for client use vs. building a demo environment are very different. In a production environment, security, stability, and performance concerns are paramount. These environments are built on a specific server and rarely, if ever, moved to a different server or different network address. There is typically just one application running on a particular server (physical or virtual). Once built, the environment will be used for months or years at a time. Because of security considerations, the installation program wants to make these environments very specific to the organization using the software and the use case, encoding a fully qualified name of the server, or even the IP address on the network, in the configuration. So you either go through the installation procedure for each environment, or learn how to clone and reconfigure the software as a separate instance to build all your non-production environments. This may not matter much if the installation is as simple as clicking on the Setup program. But for enterprise applications, you have a number of configuration settings that you need to get just right – so whether you are installing from scratch or reconfiguring an existing installation, this requires both time and expertise in the particular piece of software. If you need a setup of several applications that are integrated to talk to one another, it is a whole new level of complexity. Now you need the expertise in all of the applications involved (plus the supporting technology products), and in addition to making each application work, you also have to configure the integration endpoints. Each application needs the URLs and credentials to call the integration layer, and the integration must be able to call each application. Then you have to make sure that each app has the right data so a business process initiated in one application can continue in the next. And, you will need to check that each application has the correct version and patch level for the integration to work. When building demo environments, your #1 concern is agility. If you can get away with a small number of long-running environments, you are lucky. More likely, you may get a request for a dedicated environment for a demonstration that is two weeks away: how quickly can you make this available so we still have the time to build the client-specific data? We are running a hands-on workshop next month, and we’ll need 15 instances of application X environment so each student can have a separate server for the exercises. We cannot connect to our data center from the client site, the client’s security policy won’t allow our VPN to go through – so we need a portable environment that we can bring with us. Our consultants need to be able to work at the hotel, airport, and the airplane, so we really want an environment that can run on a laptop. The client will need two playpen environments running in the cloud, accessible from their network, for a series of workshops that start two weeks from now. We have seen all of these scenarios and more. Here you would be much better served by a generic installation that would be easy to clone. Welcome to the Wonder Machine The reason I started this blog is to share a particular design of a demo environment, a special way to install software, that can address the above requirements, even for integrated setups. This design was created by a team at Oracle Utilities Global Business Unit, and we are using this setup for most of our demo environments. In a bout of modesty we called it the Wonder Machine. Over the next few posts – think of it as a novel in parts – I will tell you about the big idea, how it was implemented and what you can do with it. After we have laid down the groundwork, I would like to share some tips and tricks for users of our Wonder Machine implementation, as well as things I am learning about building portable, cloneable environments. The Wonder Machine is by no means a closed specification, it is under active development! I am hoping this blog will be of interest to two groups of readers – the users of the Wonder Machine we have built at Oracle Utilities, who want to get the most out of their demo environments and be able to reconfigure it to their needs – and to people who need to build environments for demonstration, testing, training, development and would like to make them cloneable and portable to maximize the reuse of their effort. Surely we are not the only ones facing this problem? If you can think of a better way to solve it, or if you can help us improve on our concept, I will appreciate your comments!

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• Concurrency Utilities for Java EE Early Draft (JSR 236)

  - by arungupta

  Concurrency Utilities for Java EE is being worked as JSR 236 and has released an Early Draft. It provides concurrency capabilities to Java EE application components without compromising container integrity. Simple (common) and advanced concurrency patterns are easily supported without sacrificing usability. Using Java SE concurrency utilities such as java.util.concurrent API, java.lang.Thread and java.util.Timer in a Java EE application component such as EJB or Servlet are problematic since the container and server have no knowledge of these resources. JSR 236 enables concurrency largely by extending the Concurrency Utilities API developed under JSR-166. This also allows a consistency between Java SE and Java EE concurrency programming model. There are four main programming interfaces available: ManagedExecutorService ManagedScheduledExecutorService ContextService ManagedThreadFactory ManagedExecutorService is a managed version of java.util.concurrent.ExecutorService. The implementations of this interface are provided by the container and accessible using JNDI reference: <resource-env-ref>  <resource-env-ref-name>    concurrent/BatchExecutor  </resource-env-ref-name>  <resource-env-ref-type>    javax.enterprise.concurrent.ManagedExecutorService  </resource-env-ref-type><resource-env-ref> and available as: @Resource(name="concurrent/BatchExecutor")ManagedExecutorService executor; Its recommended to bind the JNDI references in the java:comp/env/concurrent subcontext. The asynchronous tasks that need to be executed need to implement java.lang.Runnable or java.util.concurrent.Callable interface as: public class MyTask implements Runnable { public void run() { // business logic goes here }} OR public class MyTask2 implements Callable<Date> {  public Date call() { // business logic goes here   }} The task is then submitted to the executor using one of the submit method that return a Future instance. The Future represents the result of the task and can also be used to check if the task is complete or wait for its completion. Future<String> future = executor.submit(new MyTask(), String.class);. . .String result = future.get(); Another example to submit tasks is: class MyTask implements Callback<Long> { . . . }class MyTask2 implements Callback<Date> { . . . }ArrayList<Callable> tasks = new ArrayList<();tasks.add(new MyTask());tasks.add(new MyTask2());List<Future<Object>> result = executor.invokeAll(tasks); The ManagedExecutorService may be configured for different properties such as: Hung Task Threshold: Time in milliseconds that a task can execute before it is considered hung Pool Info Core Size: Number of threads to keep alive Maximum Size: Maximum number of threads allowed in the pool Keep Alive: Time to allow threads to remain idle when # of threads > Core Size Work Queue Capacity: # of tasks that can be stored in inbound buffer Thread Use: Application intend to run short vs long-running tasks, accordingly pooled or daemon threads are picked ManagedScheduledExecutorService adds delay and periodic task running capabilities to ManagedExecutorService. The implementations of this interface are provided by the container and accessible using JNDI reference: <resource-env-ref>  <resource-env-ref-name>    concurrent/BatchExecutor  </resource-env-ref-name>  <resource-env-ref-type>    javax.enterprise.concurrent.ManagedExecutorService  </resource-env-ref-type><resource-env-ref> and available as: @Resource(name="concurrent/timedExecutor")ManagedExecutorService executor; And then the tasks are submitted using submit, invokeXXX or scheduleXXX methods. ScheduledFuture<?> future = executor.schedule(new MyTask(), 5, TimeUnit.SECONDS); This will create and execute a one-shot action that becomes enabled after 5 seconds of delay. More control is possible using one of the newly added methods: MyTaskListener implements ManagedTaskListener {  public void taskStarting(...) { . . . }  public void taskSubmitted(...) { . . . }  public void taskDone(...) { . . . }  public void taskAborted(...) { . . . } }ScheduledFuture<?> future = executor.schedule(new MyTask(), 5, TimeUnit.SECONDS, new MyTaskListener()); Here, ManagedTaskListener is used to monitor the state of a task's future. ManagedThreadFactory provides a method for creating threads for execution in a managed environment. A simple usage is: @Resource(name="concurrent/myThreadFactory")ManagedThreadFactory factory;. . .Thread thread = factory.newThread(new Runnable() { . . . }); concurrent/myThreadFactory is a JNDI resource. There is lot of interesting content in the Early Draft, download it, and read yourself. The implementation will be made available soon and also be integrated in GlassFish 4 as well. Some references for further exploring ... Javadoc Early Draft Specification concurrency-ee-spec.java.net [email protected]

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• Collaborative Whiteboard using WebSocket in GlassFish 4 - Text/JSON and Binary/ArrayBuffer Data Transfer (TOTD #189)

  - by arungupta

  This blog has published a few blogs on using JSR 356 Reference Implementation (Tyrus) as its integrated in GlassFish 4 promoted builds. TOTD #183: Getting Started with WebSocket in GlassFish TOTD #184: Logging WebSocket Frames using Chrome Developer Tools, Net-internals and Wireshark TOTD #185: Processing Text and Binary (Blob, ArrayBuffer, ArrayBufferView) Payload in WebSocket TOTD #186: Custom Text and Binary Payloads using WebSocket One of the typical usecase for WebSocket is online collaborative games. This Tip Of The Day (TOTD) explains a sample that can be used to build such games easily. The application is a collaborative whiteboard where different shapes can be drawn in multiple colors. The shapes drawn on one browser are automatically drawn on all other peer browsers that are connected to the same endpoint. The shape, color, and coordinates of the image are transfered using a JSON structure. A browser may opt-out of sharing the figures. Alternatively any browser can send a snapshot of their existing whiteboard to all other browsers. Take a look at this video to understand how the application work and the underlying code. The complete sample code can be downloaded here. The code behind the application is also explained below. The web page (index.jsp) has a HTML5 Canvas as shown: <canvas id="myCanvas" width="150" height="150" style="border:1px solid #000000;"></canvas> And some radio buttons to choose the color and shape. By default, the shape, color, and coordinates of any figure drawn on the canvas are put in a JSON structure and sent as a message to the WebSocket endpoint. The JSON structure looks like: { "shape": "square", "color": "#FF0000", "coords": { "x": 31.59999942779541, "y": 49.91999053955078 }} The endpoint definition looks like: @WebSocketEndpoint(value = "websocket",encoders = {FigureDecoderEncoder.class},decoders = {FigureDecoderEncoder.class})public class Whiteboard { As you can see, the endpoint has decoder and encoder registered that decodes JSON to a Figure (a POJO class) and vice versa respectively. The decode method looks like: public Figure decode(String string) throws DecodeException { try { JSONObject jsonObject = new JSONObject(string); return new Figure(jsonObject); } catch (JSONException ex) { throw new DecodeException("Error parsing JSON", ex.getMessage(), ex.fillInStackTrace()); }} And the encode method looks like: public String encode(Figure figure) throws EncodeException { return figure.getJson().toString();} FigureDecoderEncoder implements both decoder and encoder functionality but thats purely for convenience. But the recommended design pattern is to keep them in separate classes. In certain cases, you may even need only one of them. On the client-side, the Canvas is initialized as: var canvas = document.getElementById("myCanvas");var context = canvas.getContext("2d");canvas.addEventListener("click", defineImage, false); The defineImage method constructs the JSON structure as shown above and sends it to the endpoint using websocket.send(). An instant snapshot of the canvas is sent using binary transfer with WebSocket. The WebSocket is initialized as: var wsUri = "ws://localhost:8080/whiteboard/websocket";var websocket = new WebSocket(wsUri);websocket.binaryType = "arraybuffer"; The important part is to set the binaryType property of WebSocket to arraybuffer. This ensures that any binary transfers using WebSocket are done using ArrayBuffer as the default type seem to be blob. The actual binary data transfer is done using the following: var image = context.getImageData(0, 0, canvas.width, canvas.height);var buffer = new ArrayBuffer(image.data.length);var bytes = new Uint8Array(buffer);for (var i=0; i<bytes.length; i++) { bytes[i] = image.data[i];}websocket.send(bytes); This comprehensive sample shows the following features of JSR 356 API: Annotation-driven endpoints Send/receive text and binary payload in WebSocket Encoders/decoders for custom text payload In addition, it also shows how images can be captured and drawn using HTML5 Canvas in a JSP. How could this be turned in to an online game ? Imagine drawing a Tic-tac-toe board on the canvas with two players playing and others watching. Then you can build access rights and controls within the application itself. Instead of sending a snapshot of the canvas on demand, a new peer joining the game could be automatically transferred the current state as well. Do you want to build this game ? I built a similar game a few years ago. Do somebody want to rewrite the game using WebSocket APIs ? :-) Many thanks to Jitu and Akshay for helping through the WebSocket internals! Here are some references for you: JSR 356: Java API for WebSocket - Specification (Early Draft) and Implementation (already integrated in GlassFish 4 promoted builds) Subsequent blogs will discuss the following topics (not necessary in that order) ... Error handling Interface-driven WebSocket endpoint Java client API Client and Server configuration Security Subprotocols Extensions Other topics from the API

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• Rx Reactive extensions: Unit testing with FromAsyncPattern

  - by Andrew Anderson

  The Reactive Extensions have a sexy little hook to simplify calling async methods: var func = Observable.FromAsyncPattern<InType, OutType>( myWcfService.BeginDoStuff, myWcfService.EndDoStuff); func(inData).ObserveOnDispatcher().Subscribe(x => Foo(x)); I am using this in an WPF project, and it works great at runtime. Unfortunately, when trying to unit test methods that use this technique I am experiencing random failures. ~3 out of every five executions of a test that contain this code fails. Here is a sample test (implemented using a Rhino/unity auto-mocking container): [TestMethod()] public void SomeTest() { // arrange var container = GetAutoMockingContainer(); container.Resolve<IMyWcfServiceClient>() .Expect(x => x.BeginDoStuff(null, null, null)) .IgnoreArguments() .Do( new Func<Specification, AsyncCallback, object, IAsyncResult>((inData, asyncCallback, state) => { return new CompletedAsyncResult(asyncCallback, state); })); container.Resolve<IRepositoryServiceClient>() .Expect(x => x.EndRetrieveAttributeDefinitionsForSorting(null)) .IgnoreArguments() .Do( new Func<IAsyncResult, OutData>((ar) => { return someMockData; })); // act var target = CreateTestSubject(container); target.DoMethodThatInvokesService(); // Run the dispatcher for everything over background priority Dispatcher.CurrentDispatcher.Invoke(DispatcherPriority.Background, new Action(() => { })); // assert Assert.IsTrue(my operation ran as expected); } The problem that I see is that the code that I specified to run when the async action completed (in this case, Foo(x)), is never called. I can verify this by setting breakpoints in Foo and observing that they are never reached. Further, I can force a long delay after calling DoMethodThatInvokesService (which kicks off the async call), and the code is still never run. I do know that the lines of code invoking the Rx framework were called. Other things I've tried: I have attempted to modify the second last line according to the suggestions here: Reactive Extensions Rx - unit testing something with ObserveOnDispatcher No love. I have added .Take(1) to the Rx code as follows: func(inData).ObserveOnDispatcher().Take(1).Subscribe(x = Foo(x)); This improved my failure rate to something like 1 in 5, but they still occurred. I have rewritten the Rx code to use the plain jane Async pattern. This works, however my developer ego really would love to use Rx instead of boring old begin/end. In the end I do have a work around in hand (i.e. don't use Rx), however I feel that it is not ideal. If anyone has ran into this problem in the past and found a solution, I'd dearly love to hear it.

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• Geb not working with chrome driver

  - by user2346867

  @Grapes([ @Grab("org.gebish:geb-core:0.9.0"), @Grab("org.gebish:geb-spock:0.9.0"), @Grab("org.seleniumhq.selenium:selenium-firefox-driver:2.33.0"), @Grab("org.seleniumhq.selenium:selenium-chrome-driver:2.33.0"), @Grab("org.seleniumhq.selenium:selenium-support:2.26.0"), @Grab( group='org.spockframework', module='spock-core', version='0.3' ), @Grab(group='org.gebish', module='geb-implicit-assertions', version='0.9.0') ]) import geb.Browser import geb.spock.GebReportingSpec import org.openqa.selenium.chrome.* import spock.lang.Specification import geb.navigator.NonEmptyNavigator import geb.navigator.factory.* System.setProperty("webdriver.chrome.driver", "C:\\chromedriver\\chromedriver.exe"); def browser = new Browser(driver: new ChromeDriver()) browser.go "http://www.google.com/" assert browser.title == "Google" browser.$("input", name: "q").value("query") When i try to run the above code i am getting the following error WARNING: Sanitizing stacktrace: java.lang.NoClassDefFoundError: Could not initialize class geb.navigator.NonEmptyNavigator at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:171) at geb.navigator.factory.DefaultInnerNavigatorFactory.class$(DefaultInnerNavigatorFactory.groovy) at geb.navigator.factory.DefaultInnerNavigatorFactory.$get$$class$geb$navigator$NonEmptyNavigator(DefaultInnerNavigatorFactory.groovy) at geb.navigator.factory.DefaultInnerNavigatorFactory.createNavigator(DefaultInnerNavigatorFactory.groovy:40) at geb.navigator.factory.InnerNavigatorFactory$createNavigator.call(Unknown Source) at geb.navigator.factory.AbstractNavigatorFactory.createFromWebElements(AbstractNavigatorFactory.groovy:44) at geb.navigator.factory.NavigatorFactory$createFromWebElements.callCurrent(Unknown Source) at geb.navigator.factory.BrowserBackedNavigatorFactory.getBase(BrowserBackedNavigatorFactory.groovy:33) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90) at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233) at groovy.lang.MetaClassImpl.getProperty(MetaClassImpl.java:1671) at groovy.lang.MetaClassImpl.getProperty(MetaClassImpl.java:3408) at geb.navigator.factory.AbstractNavigatorFactory.getProperty(AbstractNavigatorFactory.groovy) at org.codehaus.groovy.runtime.callsite.PogoGetPropertySite.getProperty(PogoGetPropertySite.java:47) at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callGetProperty(AbstractCallSite.java:227) at geb.content.NavigableSupport.getNavigator(NavigableSupport.groovy:39) at geb.content.NavigableSupport.$(NavigableSupport.groovy:96) at geb.content.NavigableSupport$$.call(Unknown Source) at geb.Page.$(Page.groovy) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90) at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233) at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1085) at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:909) at org.codehaus.groovy.runtime.InvokerHelper.invokePogoMethod(InvokerHelper.java:848) at org.codehaus.groovy.runtime.InvokerHelper.invokeMethod(InvokerHelper.java:831) at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodN(ScriptBytecodeAdapter.java:164) at geb.Browser.methodMissing(Browser.groovy:193) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90) at groovy.lang.MetaClassImpl.invokeMissingMethod(MetaClassImpl.java:837) Any idea on this how to resolve it ???

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• Server side Xforms form validation and integration into ASP.NET

  - by Nigel

  I have recently been investigating methods of creating web-based forms for an ASP.NET web application that can be edited and managed at runtime. For example an administrator might wish to add a new validation rule or a new set of fields. The holy grail would provide a means of specifying a form along with (potentially very complex) arbitrary validation rules, and allocation of data sources for each field. The specification would then be used to update the deployed form in the web application which would then validate submissions both on the client side and on the server side. My investigations led me to Xforms and a number of technologies that support it. One solution appears to be IBM Lotus Forms, but this requires a very large investment in terms of infrastructure, which makes it infeasible, although the forms designer may be useful as a stand-alone tool for creating the forms. I have also discounted browser plug-ins as the form must be publicly visible and cross-browser compliant. I have noticed that there are numerous javascript libraries that provide client side implementations given an Xforms schema. These would provide a partial solution but server side validation is still a requirement. Another option seems to involve the use of server side solutions such as the Java application Orbeon. Orbeon provides a tool for specifying the forms (although not as rich as Lotus Forms Designer), but the most interesting point is that it can translate an XForms schema into an XHTML form complete with validation. The fact that it is written in Java is not a big problem if it is possible to integrate with the existing ASP.NET application. So my question is whether anyone has done this before. It sounds like a problem that should have been solved but is inherently very complex. It seems possible to use an off-the-shelf tool to design the form and export it to an Xforms schema and xhtml form, and it seems possible to take that xforms schema and form and publish it using a client side library. What seems to be difficult is providing a means of validating the form submission on the server side and integrating the process nicely with .NET (although it seems the .NET community doesn't involve themselves with XForms; please correct me if I'm wrong on this count). I would be more than happy if a product provided something simple like a web service that could validate a submission against a schema. Maybe Orbeon does this but I'd be grateful if somebody in the know could point me in the right direction before I research it further. Many thanks.

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• C# 4.0 'dynamic' and foreach statement

  - by ControlFlow

  Not long time before I've discovered, that new dynamic keyword doesn't work well with the C#'s foreach statement: using System; sealed class Foo { public struct FooEnumerator { int value; public bool MoveNext() { return true; } public int Current { get { return value++; } } } public FooEnumerator GetEnumerator() { return new FooEnumerator(); } static void Main() { foreach (int x in new Foo()) { Console.WriteLine(x); if (x >= 100) break; } foreach (int x in (dynamic)new Foo()) { // :) Console.WriteLine(x); if (x >= 100) break; } } } I've expected that iterating over the dynamic variable should work completely as if the type of collection variable is known at compile time. I've discovered that the second loop actually is looked like this when is compiled: foreach (object x in (IEnumerable) /* dynamic cast */ (object) new Foo()) { ... } and every access to the x variable results with the dynamic lookup/cast so C# ignores that I've specify the correct x's type in the foreach statement - that was a bit surprising for me... And also, C# compiler completely ignores that collection from dynamically typed variable may implements IEnumerable<T> interface! The full foreach statement behavior is described in the C# 4.0 specification 8.8.4 The foreach statement article. But... It's perfectly possible to implement the same behavior at runtime! It's possible to add an extra CSharpBinderFlags.ForEachCast flag, correct the emmited code to looks like: foreach (int x in (IEnumerable<int>) /* dynamic cast with the CSharpBinderFlags.ForEachCast flag */ (object) new Foo()) { ... } And add some extra logic to CSharpConvertBinder: Wrap IEnumerable collections and IEnumerator's to IEnumerable<T>/IEnumerator<T>. Wrap collections doesn't implementing Ienumerable<T>/IEnumerator<T> to implement this interfaces. So today foreach statement iterates over dynamic completely different from iterating over statically known collection variable and completely ignores the type information, specified by user. All that results with the different iteration behavior (IEnumarble<T>-implementing collections is being iterated as only IEnumerable-implementing) and more than 150x slowdown when iterating over dynamic. Simple fix will results a much better performance: foreach (int x in (IEnumerable<int>) dynamicVariable) { But why I should write code like this? It's very nicely to see that sometimes C# 4.0 dynamic works completely the same if the type will be known at compile-time, but it's very sadly to see that dynamic works completely different where IT CAN works the same as statically typed code. So my question is: why foreach over dynamic works different from foreach over anything else?

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• Eclipse Dynamic Web Project fails to load under WTP

  - by Cue

  When trying to run an Eclipse Dynamic Web Project under a Tomcat setup using WTP, it fails with the attached stacktrace. Checklist At the project properties, under "Java EE Module Dependencies" I have checked the "Maven Dependencies" At the wtp deploy directory, under lib indeed all dependencies are present (esp. struts-taglib-1.3.10.jar) On the other hand, if I package with maven and copy the war file under the webapps directory everything is working as normal. Specification Eclipse JEE Galileo SR2 (with WTP 3.1.1) Tomcat 6.0.26 Java(TM) SE Runtime Environment (build 1.6.0_17-b04-248-10M3025) Java HotSpot(TM) 64-Bit Server VM (build 14.3-b01-101, mixed mode) stacktrace org.apache.jasper.JasperException: Unable to read TLD "META-INF/tld/struts-html-el.tld" from JAR file "file:/Users/cue/Development/workspace/eclipse/.metadata/.plugins/org.eclipse.wst.server.core/tmp2/wtpwebapps/ticketing/WEB-INF/lib/struts-el-1.3.10.jar": org.apache.jasper.JasperException: Failed to load or instantiate TagExtraInfo class: org.apache.struts.taglib.html.MessagesTei at org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:51) at org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:409) at org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:181) at org.apache.jasper.compiler.TagLibraryInfoImpl.<init>(TagLibraryInfoImpl.java:182) at org.apache.jasper.compiler.Parser.parseTaglibDirective(Parser.java:383) at org.apache.jasper.compiler.Parser.parseDirective(Parser.java:446) at org.apache.jasper.compiler.Parser.parseElements(Parser.java:1393) at org.apache.jasper.compiler.Parser.parse(Parser.java:130) at org.apache.jasper.compiler.ParserController.doParse(ParserController.java:255) at org.apache.jasper.compiler.ParserController.parse(ParserController.java:103) at org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:185) at org.apache.jasper.compiler.Compiler.compile(Compiler.java:347) at org.apache.jasper.compiler.Compiler.compile(Compiler.java:327) at org.apache.jasper.compiler.Compiler.compile(Compiler.java:314) at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:589) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:317) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Thread.java:637)

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• Code Golf: Evaluating Mathematical Expressions

  - by Noldorin

  Challenge Here is the challenge (of my own invention, though I wouldn't be surprised if it has previously appeared elsewhere on the web). Write a function that takes a single argument that is a string representation of a simple mathematical expression and evaluates it as a floating point value. A "simple expression" may include any of the following: positive or negative decimal numbers, +, -, *, /, (, ). Expressions use (normal) infix notation. Operators should be evaluated in the order they appear, i.e. not as in BODMAS, though brackets should be correctly observed, of course. The function should return the correct result for any possible expression of this form. However, the function does not have to handle malformed expressions (i.e. ones with bad syntax). Examples of expressions: 1 + 3 / -8 = -0.5 (No BODMAS) 2*3*4*5+99 = 219 4 * (9 - 4) / (2 * 6 - 2) + 8 = 10 1 + ((123 * 3 - 69) / 100) = 4 2.45/8.5*9.27+(5*0.0023) = 2.68... Rules I anticipate some form of "cheating"/craftiness here, so please let me forewarn against it! By cheating, I refer to the use of the eval or equivalent function in dynamic languages such as JavaScript or PHP, or equally compiling and executing code on the fly. (I think my specification of "no BODMAS" has pretty much guaranteed this however.) Apart from that, there are no restrictions. I anticipate a few Regex solutions here, but it would be nice to see more than just that. Now, I'm mainly interested in a C#/.NET solution here, but any other language would be perfectly acceptable too (in particular, F# and Python for the functional/mixed approaches). I haven't yet decided whether I'm going to accept the shortest or most ingenious solution (at least for the language) as the answer, but I would welcome any form of solution in any language, except what I've just prohibited above! My Solution I've now posted my C# solution here (403 chars). Update: My new solution has beaten the old one significantly at 294 chars, with the help of a bit of lovely regex! I suspected that this will get easily beaten by some of the languages out there with lighter syntax (particularly the funcional/dynamic ones), and have been proved right, but I'd be curious if someone could beat this in C# still. Update I've seen some very crafty solutions already. Thanks to everyone who has posted one. Although I haven't tested any of them yet, I'm going to trust people and assume they at least work with all of the given examples. Just for the note, re-entrancy (i.e. thread-safety) is not a requirement for the function, though it is a bonus. Format Please post all answers in the following format for the purpose of easy comparison: Language Number of characters: ??? Fully obfuscated function: (code here) Clear/semi-obfuscated function: (code here) Any notes on the algorithm/clever shortcuts it takes.

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• Which third party website thumbnailing services do you use?

  - by Ben Delarre

  I've got a requirement for showing thumbnails of arbitrary websites. I need to be able to show small thumbnails (120px by 90px), and larger thumbnails of around 480px wide. I'll need to specify the queue and invalid placeholder images and preferably have a pingback when the queued images are processed so I can respond appropriately. I'd also need a simple API I can use either directly embedded in my HTML, or from a simple web request to queue the images. I've been looking at various services ranging from low-fi services, to large scale ones - here's some examples: www.bitpixels.com Uses Google AppEngine, seems like a prototype or a toy. Free! www.websnapr.com Tried using this, made a free account and requested a thumbnail. Waited a few minutes and refreshed a couple of times, and ended up having the account banned. Free is tricky yes, but if I can't try it out successfully I'm disinclined to pay. www.shrinktheweb.com Free account seems to be very quick. Lots of documentation on the site, and even covers local caching of the images to your own server (documentation mostly in PHP). Quality of thumbnails look good, and there appear to be sufficient options for setting thumbnail placeholder images and parameters for altering how the thumbnailing is done. Also supports large 'screenshots' of URLs - very useful for me. Discovered the PRO pricing is an à la carte menu, allowing me to select just the features I want and keep the monthly cost low. Excellent stuff, have decided to use this service. www.thumbalizr.com Good coverage of thumbnail sizes and control options - even allowing specification for browser width when thumbnailing. No ping-back, but I can live without that. Supports local caching of images with PHP API, would prefer .NET, but can port it if necessary. Looks like a fairly professional service but seems fairly expensive for the number of thumbnails you get to generate. apologies for lack of proper linking - spam protection! I'm not entirely convinced by any of them, and since this will be a long term service I'd like some stability and support. I'm willing to pay for the service, but I'd want something that fulfills most if not all of my requirements for that. I should also mention that we're hosted on Windows under IIS, so local solutions involving Xvfb and the like sadly can't be used for this project. So my question is: what services do you use? How have they panned out, are you happy with them?

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• Google Bookmarks Accelerator for IE8

  - by MACHiNESMiTH

  To Editors: Sorry, I didnt realise the question thing till you pointed it out. Also I didn't know about the appengine tag, I'm assuming it was selected by mistake from that JS autosuggestion box (it usually happens with me, I run a P3) my apologies for that too. I've edited it now, if it doesnt work let me know. Hi all, I'm making (or at least trying to make) a Google bookmarks accelerator for IE8, but I keep running into "Internet Explorer could not install this accelerator. There was a problem with the Accelerator's information." Does anyone know why this is happening? Here is the code I've made <?xml version="1.0" encoding="UTF-8" ?> <os:openServiceDescription xmlns="http://www.microsoft.com/schemas/openservicedescription/1.0"> <os:homepageUrl>http://www.google.com/bookmarks</os:homepageUrl> <os:display> <os:description>Add this page to GoogleBookmarks</os:description> <os:name>Add to GoogleBookmarks</os:name> <os:icon>http://www.google.com/favicon.ico</os:icon> </os:display> <os:activity category="Bookmarks"> <os:activityAction context="document"> <os:execute method="get" action="http://www.google.com/bookmarks/mark?op=add&output=popup"> <os:parameter name="bkmk" value="{documentUrl}" /> <os:parameter name="title" value="{documentTitle}" /> <os:parameter name="annotation" value="{selection}" /> </os:execute> </os:activityAction> </os:activity> </os:openServiceDescription> These are the references I used: MSDN Developers Guide MSDN Format Specification Unofficial Google API (used as a look up so far) and yes i know that I cannot send document variables between schemes (HTTP - HTTPS, for example) or between servers in different security zones (Intranet - Internet etc) Also, if this is the wrong place, what are the recommended sites and/or forums for xml related posts? (not really questions - but more like full blown detailed rant like posts) Thanks

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• Using JUnit as an acceptance test framework

  - by Chris Knight

  OK, so I work for a company who has openly adopted agile practices for development in recent years. Our unit tests and code quality are improving. One area we still are working on is to find what works best for us in the automated acceptance test arena. We want to take our well formed user stories and use these to drive the code in a test driven manner. This will also give us acceptance level tests for each user story which we can then automate. To date, we've tried Fit, Fitnesse and Selenium. Each have their advantages, but we've also had real issues with them as well. With Fit and Fitnesse, we can't help but feel they overcomplicate things and we've had many technical issues using them. The business haven't fully bought in these tools and aren't particularly keen on maintaining the scripts all the time (and aren't big fans of the table style). Selenium is really good, but slow and relies on real time data and resources. One approach we are now considering is the use of the JUnit framework to provide similiar functionality. Rather than testing just a small unit of work using JUnit, why not use it to write a test (using the JUnit framework) to cover an acceptance level swath of the application? I.e. take a new story ("As a user I would like to see basic details of my policy...") and write a test in JUnit which starts executing application code at the point of entry for the policy details link but covers all code and logic down to the stubbed data access layer and back to the point of forwarding to the next page in the application, asserting on what data the user should see on that page. This seems to me to have the following advantages: Simplicity (no additional frameworks required) Zero effort to integrate with our Continuous Integration build server (since it already handles our JUnit tests) Full skillset already present in the team (its just a JUnit test after all) And the downsides being: Less customer involvement (though they are heavily involved in writing the user stories in the first place from which the acceptance tests will be written) Perhaps more difficult to understand (or make understood) the user story and acceptance criteria in a JUnit class verses a freetext specification ala Fit or Fitnesse So, my question is really, have you ever tried this method? Ever considered it? What are your thoughts? What do you like and dislike about this approach? Finally, please only mention alternative frameworks if you can say why you like or dislike them more than this approach.

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• Custom Rails actions: I have issues every time

  - by normalocity

  Every time I go to add a custom action to a controller, I completely screw it up somehow. I'm trying to add a route "listings/buyer_listings", that will display all of my listings where someone is a buyer (rather than a seller). With the routes.rb file below, when I go to "listings/buyer_listings", I get routed instead to "users" WTF? In the past, I've had to define my routes using "map.", but this seems like a very verbose way to do something that should work with the :collection specification. You can see that I've done this with many routes as specified toward the end of the file, such as "edit_my_profile", etc. If I put the ":collection" part last my browser routes to the "show" action, which is not the correct action, and which also doesn't make sense to me why it would even do this. If I do "rake routes", my routes look correctly mapped. If I go into a Ruby console and have it recognize the url, it maps to the correct action, so what am I missing? ActionController::Routing::Routes.draw do |map| map.resources :locations map.resources :browse_boxes map.resources :tags map.resources :ratings map.resources :listings, :collection => { :buyer_listings => :get }, :has_many => :bids, :has_many => :comments map.resources :users map.resources :invite_requests map.resource :user_session map.resource :account, :controller => "users" map.root :controller => "listings", :action => "index" # optional, this just sets the root route map.login "login", :controller => "user_sessions", :action => "new" map.logout "logout", :controller => "user_sessions", :action => "destroy" map.search "search", :controller => "listings", :action => "search" map.edit_my_profile "edit_my_profile", :controller => "users", :action => "edit_my_profile" map.all_listings "all_listings", :controller => "listings", :action => "all_listings" map.my_listings "my_listings", :controller => "listings", :action => "my_listings" map.posting_guidelines "posting_guidelines", :controller => "listings", :action => "posting_guidelines" map.filter_on "filter_on", :controller => "listings", :action => "filter_on" map.top_25_tags "top_25_tags", :controller => "tagging_search", :action => "top_25_tags" map.connect ':controller/:action/:id' map.connect ':controller/:action/:id.:format' end

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