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• Where to turn upon realizing I can't program my way out of a paper bag?

  - by luminarious

  I have no job and just enough money to get by until April or so. While looking for work, I figured I might as well go through with a pet project, a browser based card game. Make it nice and free, collect donations and maybe earn enough for a movie ticket to escape reality for a while. I have dabbled in web development a bit. I can make simple stuff happen with JS/PHP if I follow tutorials. I designed my own art blog's template - http://luminarious.tumblr.com. I can visualise the game working in my head, flowcharts and everything. But then I tried to go deeper with Javascript and almost had an aneurysm before understanding what a closure is. Wether I suck at learning, have ADD or fail epically at productivity, I have not got much done. Coming up with ideas, screen mock-ups and so forth was very enjoyable, but actual implementation.. not so much. In fact, I cry a bit every time I think about the time someone competent could have finished this in. I'd like to excuse myself with my ENTP personality type, but that hardly solves anything. Rather, I'd like to know to get from A (bunch of ideas with little semblance to a web app) to B (something to proudly show others) while being unable to pay anyone? Are there any secret techniques for learning? Is there any way to get mentoring or code review? Is there anyone with too much free time willing to code for me? How to trust someone to not steal my code when I ask for assistance? Is there anything I should have asked instead of any of those?

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• Permuting output of a tree of closures

  - by yan

  This a conceptual question on how one would implement the following in Lisp (assuming Common Lisp in my case, but any dialect would work). Assume you have a function that creates closures that sequentially iterate over an arbitrary collection (or otherwise return different values) of data and returns nil when exhausted, i.e. (defun make-counter (up-to) (let ((cnt 0)) (lambda () (if (< cnt up-to) (incf cnt) nil)))) CL-USER> (defvar gen (make-counter 3)) GEN CL-USER> (funcall gen) 1 CL-USER> (funcall gen) 2 CL-USER> (funcall gen) 3 CL-USER> (funcall gen) NIL CL-USER> (funcall gen) NIL Now, assume you are trying to permute a combinations of one or more of these closures. How would you implement a function that returns a new closure that subsequently creates a permutation of all closures contained within it? i.e.: (defun permute-closures (counters) ......) such that the following holds true: CL-USER> (defvar collection (permute-closures (list (make-counter 3) (make-counter 3)))) CL-USER> (funcall collection) (1 1) CL-USER> (funcall collection) (1 2) CL-USER> (funcall collection) (1 3) CL-USER> (funcall collection) (2 1) ... and so on. The way I had it designed originally was to add a 'pause' parameter to the initial counting lambda such that when iterating you can still call it and receive the old cached value if passed ":pause t", in hopes of making the permutation slightly cleaner. Also, while the example above is a simple list of two identical closures, the list can be an arbitrarily-complicated tree (which can be permuted in depth-first order, and the resulting permutation set would have the shape of the tree.). I had this implemented, but my solution wasn't very clean and am trying to poll how others would approach the problem. Thanks in advance.

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• Is there an alias for 'this' in TypeScript?

  - by Todd

  I've attempted to write a class in TypeScript that has a method defined which acts as an event handler callback to a jQuery event. class Editor { textarea: JQuery; constructor(public id: string) { this.textarea = $(id); this.textarea.focusin(onFocusIn); } onFocusIn(e: JQueryEventObject) { var height = this.textarea.css('height'); // <-- This is not good. } } Within the onFocusIn event handler, TypeScript sees 'this' as being the 'this' of the class. However, jQuery overrides the this reference and sets it to the DOM object associated with the event. One alternative is to define a lambda within the constructor as the event handler, in which case TypeScript creates a sort of closure with a hidden _this alias. class Editor { textarea: JQuery; constructor(public id: string) { this.textarea = $(id); this.textarea.focusin((e) => { var height = this.textarea.css('height'); // <-- This is good. }); } } My question is, is there another way to access the this reference within the method-based event handler using TypeScript, to overcome this jQuery behavior?

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• Agile Awakenings and the Rules of Agile

  - by Robert May

  For those that care, you can read my history of management and technology to understand why I think I’m qualified to talk about this at all.  It’s boring, so feel free to skip it. Awakenings I first started to play around with the idea of “agile” in 2004 or 2005.  I found a book on the Rational Unified Process that I thought was good, and attempted to implement parts of it.  I thought I was agile, but really, it wasn’t.   I still didn’t understand the concept of a team.  I still wanted to tell the team what to do and how to get it done.  I still thought I was smarter than the team. After that job, I started work on another project and began helping that team.  The first few months were really rough.  We were implementing Scrum, which was relatively new to everyone on the team, and, quite frankly, I was doing a poor job of it.  I was trying to micro-manage every aspect of the teams work, and we were all miserable. The moment of change came when the senior architect bailed on the project.  His comment to me was: “This isn’t Agile.  Where are the stand-ups?  Where are the stories?”  He was dead on, and I finally woke up.  I finally realized that I was the problem!  I wasn’t trusting the team.  I wasn’t helping the team.  I was being a manager. Like many (most?), I was claiming to be Agile and use Scrum, but I wasn’t in fact following the rules Scrum.  Since then, I’ve done a lot of studying, hands on practice, coaching of many different teams, and other learning around Scrum, and I have discovered that Scrum has some rules that must be followed for success, even though the process is about continuous improvement. I’ve been practicing Scrum right for about 4 years now and have helped multiple teams implement it successfully, so what you’re about to get is based on experience, rather than just theory. The Rules of Scrum In my experience, what I’ve found is that most companies that claim to be doing Scrum or Agile are actually NOT doing either.  This stems largely because they think that they can “adopt the rules of Agile that fit their organization.”  Sadly, many of them think that this means they can adopt iterations (sprints) and not much else.  Either that, or they think they can do whatever they want, or were doing before, and call it Scrum.  This is simply not true. Here are some rules that must be followed for you to really be doing Scrum.  I’ll go into detail on each one of these posts in future blog posts and update links here.  My intent is that this will help other teams implementing scrum to see more success. Agile does not allow you to do whatever you want A Product Owner is required A ScrumMaster is required The team must function as a Team, and QA must be part of the team Support from upper management is required A prioritized product backlog is required A prioritized sprint backlog is required Release planning is required Complete spring planning is required Showcases are required Velocity must be measured Retrospectives are required Daily stand-ups are required Visibility is absolutely required For now, I think that’s enough, although I reserve the right to add more.  If you’re breaking any of these rules, you’re probably not doing Scrum.  There are exceptions to these rules, but until you have practiced Scrum for a while, you don’t know what those exceptions are. Breaking the Rules Many teams break these rules because they are the ones that expose the most pain.  Scrum is not Advil.  It’s not intended to mask the pain, its intended to cure it.  Let me explain that analogy a bit more.  Recently, my 7 year old son broke his arm, quite severely (see the X-Ray to the right).  That caused him a great deal of pain.  We went first to one doctor, and after viewing the X-Ray, they determined that there was no way that they’d cast the arm at their location.  It was simply too bad of a break for them to deal with.  They did, however, give him some Advil for the pain and put a splint on his arm to stabilize the broken bones.  Within minutes, he was feeling much better.  Had we been stupid, we could have gone home and he’d have been just as happy as ever . . . until the pain medication wore off or one of his siblings touched the splint.  Then, all of that pain would come right back to the top.  Sure, he could make it go away by just taking more Advil and moving the splint out of the way, but that wasn’t going to fix the problem permanently. We ended up in an emergency room with a doctor who could fix his arm.  However, we were warned that the fix was going to be VERY painful, and it was.  Even with heavy sedation (Propofol), my son was in enough pain that he squirmed and wiggled trying to get his arm away from the doctor.  He had to endure this pain in order to have a functional arm. But the setting wasn’t the end.  He had to have several casts, had to have it re-broken once, since the first setting didn’t take and finally was given a clean bill of health. Agile implementation is much like this story.  Agile was developed as a result of people recognizing that the development methodologies that were currently in place simply were ineffective.  However, the fix to the broken development that’s been festering for many years is not painless.  Many people start Agile thinking that things will be wonderful.  They won’t!  Agile is about visibility, and often, it brings great pain to surface.  It causes all of the missed deadlines, the cowboy coders, the coasters, the micro-managers, the lazy, and all of the other problems that are really part of your development process now to become painfully visible to EVERYONE.  Many people don’t like this exposure.  Agile will make the pain better, but not if you remove the cast (the rules above) prematurely and start breaking the rules that expose the most pain.  The healing will take time and is not instant (like Advil).  Figuring out what the true source of pain and fixing it is very valuable to you, your team, and your company.  Remember as you’re doing this that Agile isn’t the source of the pain, it’s really just exposing it.  Find the source. My recommendation is that ALL of these rules are followed for a minimum of six months, and preferably for an entire year, before you decide to break any of these rules.  Get a few good releases under your belt.  Figure out what your velocity is and start firing as a team.  Chances are, after you see agile really in action, you won’t want to break the rules because you’ll see their value. More Reading Jean Tabaka recently published a list of 78 Things I Have Learned in 6 Years of Agile Coaching.  Highly recommended. Technorati Tags: Agile,Scrum,Rules

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• Advanced Continuous Delivery to Azure from TFS, Part 1: Good Enough Is Not Great

  - by jasont

  The folks over on the TFS / Visual Studio team have been working hard at releasing a steady stream of new features for their new hosted Team Foundation Service in the cloud. One of the most significant features released was simple continuous delivery of your solution into your Azure deployments. The original announcement from Brian Harry can be found here. Team Foundation Service is a great platform for .Net developers who are used to working with TFS on-premises. I’ve been using it since it became available at the //BUILD conference in 2011, and when I recently came to work at Stackify, it was one of the first changes I made. Managing work items is much easier than the tool we were using previously, although there are some limitations (more on that in another blog post). However, when continuous deployment was made available, it blew my mind. It was the killer feature I didn’t know I needed. Not to say that I wasn’t previously an advocate for continuous delivery; just that it was always a pain to set up and configure. Having it hosted - and a one-click setup – well, that’s just the best thing since sliced bread. It made perfect sense: my source code is in the cloud, and my deployment is in the cloud. Great! I can queue up a build from my iPad or phone and just let it go! I quickly tore through the quick setup and saw it all work… sort of. This will be the first in a three part series on how to take the building block of Team Foundation Service continuous delivery and build a CD model that will actually work for any team deploying something more advanced than a “Hello World” example. Part 1: Good Enough Is Not Great Part 2: A Model That Works: Branching and Multiple Deployment Environments Part 3: Other Considerations: SQL, Custom Tasks, Etc Good Enough Is Not Great There. I’ve said it. I certainly hope no one on the TFS team is offended, but it’s the truth. Let’s take a look under the hood and understand how it works, and then why it’s not enough to handle real world CD as-is. How it works. (note that I’ve skipped a couple of steps; I already have my accounts set up and something deployed to Azure) The first step is to establish some oAuth magic between your Azure management portal and your TFS Instance. You do this via the management portal. Once it’s done, you have a new build process template in your TFS instance. (Image lifted from the documentation) From here, you’ll get the usual prompts for security, allowing access, etc. But you’ll also get to pick which Solution in your source control to build. Here’s what the bulk of the build definition looks like. All I’ve had to do is add in the solution to build (notice that mine is from a specific branch – Release – more on that later) and I’ve changed the configuration. I trigger the build, and voila! I have an Azure deployment a few minutes later. The beauty of this is that it’s all in the cloud and I’m not waiting for my machine to compile and upload the package. (I also had to enable the build definition first – by default it is created in disabled state, probably a good thing since it will trigger on every.single.checkin by default.) I get to see a history of deployments from the Azure portal, and can link into TFS to see the associated changesets and work items. You’ll notice also that this build definition also automatically put my code in the Staging slot of my Azure deployment – more on this soon. For now, I can VIP swap and be in production. (P.S. I hate VIP swap and “production” and “staging” in Azure. More on that later too.) That’s it. That’s the default out-of-box experience. Easy, right? But it’s full of room for improvement, so let’s get into that….   The Problems Nothing is perfect (except my code – it’s always perfect), and neither is Continuous Deployment without a bit of work to help it fit your dev team’s process. So what are the issues? Issue 1: Staging vs QA vs Prod vs whatever other environments your team may have. This, for me, is the big hairy one. Remember how this automatically deployed to staging rather than prod for us? There are a couple of issues with this model: If I want to deliver to prod, it requires intervention on my part after deployment (via a VIP swap). If I truly want to promote between environments (i.e. Nightly Build –> Stable QA –> Production) I likely have configuration changes between each environment such as database connection strings and this process (and the VIP swap) doesn’t account for this. Yet. Issue 2: Branching and delivering on every check-in. As I mentioned above, I have set this up to target a specific branch – Release – of my code. For the purposes of this example, I have adopted the “basic” branching strategy as defined by the ALM Rangers. This basically establishes a “Main” trunk where you branch off Dev and Release branches. Granted, the Release branch is usually the only thing you will deploy to production, but you certainly don’t want to roll to production automatically when you merge to the Release branch and check-in (unless you like the thrill of it, and in that case, I like your style, cowboy….). Rather, you have nightly build and QA environments, or if you’ve adopted the feature-branch model you have environments for those. Those are the environments you want to continuously deploy to. But that takes us back to Issue 1: we currently have a 1:1 solution to Azure deployment target. Issue 3: SQL and other custom tasks. Let’s be honest and address the elephant in the room: I need to get some sleep because I see an elephant in the room. But seriously, I can’t think of an application I have touched in the last 10 years that doesn’t need to consider SQL changes when deploying code and upgrading an environment. Microsoft seems perfectly content to ignore this elephant for now: yes, they’ve added Data Tier Applications. But let’s be honest with ourselves again: no one really uses it, and it’s not suitable for anything more complex than a Hello World sample project database. Why? Because it doesn’t fit well into a great source control story. Developers make stored procedure and table changes all day long while coding complex applications, and if someone forgets to go update the DACPAC before the automated deployment, you have a broken build until it’s completed. Developers – not just DBAs – also like to work with SQL in SQL tools, not in Visual Studio. I’m really picking on SQL because that’s generally the biggest concern that I hear. But we need to account for any custom tasks as well in the build process.   The Solutions… ? We’ve taken a look at how this all works, and addressed the shortcomings. In my next post (which I promise will be very, very soon), I will detail how I’ve overcome these shortcomings and used this foundation to create a mature, flexible model for deploying my app – any version, any time, to any environment.

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• Thou shalt not put code on a piedestal - Code is a tool, no more, no less

  - by Ralf Westphal

  “Write great code and everything else becomes easier” is what Paul Pagel believes in. That´s his version of an adage by Brian Marick he cites: “treat code as an end, not just a means.” And he concludes: “My post-Agile world is software craftsmanship.” I wonder, if that´s really the way to go. Will “simply” writing great code lead the software industry into the light? He´s alluding to the philosopher Kant who proposed, a human beings should never be treated as a means, but always as an end. But should we transfer this ethical statement into the world of software? I doubt it.   Reason #1: Human beings are categorially different from code. They are autonomous entities who need to find a way of living happily together. To Kant it seemed this goal could only be reached if nobody (ab)used a human being for his/her purposes. Because using a human being, i.e. treating it as a means, would contradict the fundamental autonomy and freedom of human beings. People should hold up a symmetric view of their relationships: Since nobody wants to be (ab)used, nobody should (ab)use anybody else. If you want to be treated decently, with respect, in accordance with your own free will - which means as an end - then do the same to other people. Code is dead, it´s a product, it´s a tool for people to reach their goals. No company spends any money on code other than to save money or earn money in the long run. Code is not a puppy. Enterprises do not commission software development to just feel good in its company. Code is not a buddy. Code is a slave, if you will. A mechanical slave, a non-tangible robot. Code is a tool, is a tool. And if we start to treat it differently, if we elevate its status unduely… I guess that will contort our relationship in a contraproductive way. Please get me right: Just because something is “just a tool”, “just a product” does not mean we should not be careful while designing, building, using it. Right to the contrary. We should be very careful when writing code – but not for the code´s sake! We should be careful because we respect our customers who are fellow human beings who should be treated as an end. If we are careless, neglectful, ignorant when producing code on their behalf, then we´re using them. Being sloppy means you´re caring more for yourself that for your customer. You´re then treating the customer as a means to fulfill some of your own needs. That´s plain unethical behavior.   Reason #2: The focus should always be on your purpose, not on any tool. But if code is treated as an end, then the focus is on the code. That might sound right, because where else should be your focus as a software developer? But, well, I´d say, your focus should be on delivering value to your customer. Because in the end your customer does not care if you write a single line of code. She just wants her problem to be solved. Solving problems is the purpose of any contractor. Code must be treated just as a means, a tool we know how to handle very well. But if we´re really trying to be craftsmen then we should be conscious about exactly that and act ethically. That means we must never be so focused on our tool as to be unable to suggest better solutions to the problems of our customers than code.   I´m all with Paul when he urges us to “Write great code”. Sure, if you need to write code, then by all means do so. Write the best code you can think of – and then try to improve it. Paul has all the best intentions when he signs Brians “treat code as an end” - but as we all know: “The road to hell is paved with best intentions” ;-) Yes, I can imagine a “hell of code focus”. In fact, I don´t need to imagine it, I´m seeing it quite often. Because code hell is whereever two developers stand together and are so immersed in talking about all sorts of coding tricks, design patterns, code smells, technologies, platforms, tools that they lose sight of the big picture. Talking about TDD or SOLID or refactoring is a sign of consciousness – relative to the “cowboy coders” view of the world. But from yet another point of view TDD, SOLID, and refactoring are just cures for ailments within a system. And I fear, if “Writing great code” is the only focus or the main focus of software development, then we as an industry lose the ability to see that. Focus draws a line around something, it defines a horizon for perceptions and thinking. So if we focus on code our horizon ends where “the land of code” ends. I don´t think that should be our professional attitude.   So what about Software Craftsmanship as the next big thing after Agility? I think Software Craftsmanship has an important message for all software developers and beyond. But to make it the successor of the Agility movement seems to miss a point. Agility never claimed to solve all software development problems, I´d say. So to blame it for having missed out on certain aspects of it is wrong. If I had to summarize Agility in one word I´d say “Value”. Agility put value for the customer back in software development. Focus on delivering value early and often – that´s Agility´s mantra. All else follows from that. And I ask you: Is that obsolete? Is delivering value not hip anymore? No, sure not. That´s our very purpose as software developers. So how can Agility become obsolete and need to be replaced? We need to do away with this “either/or”-thinking. It´s either Agility or Lean or Software Craftsmanship or whatnot. Instead we should start integrating concepts and movements. Think “both/and”. Think Agility plus Software Craftsmanship plus Lean plus whatnot. We don´t neet to tear down anything from a piedestal and replace it with a new idol. Instead we should do away with piedestals and arrange whatever is helpful is a circle. Then we can turn to concepts, movements for whatever they are best. After 10 years of Agility we should be able to identify what it was good at – and keep that. Keep Agility around and add whatever Agility was lacking or never concerned with. Add whatever is at the core of Software Craftsmanship. Add whatever is at the core of Lean etc. But don´t call out the age of Post-Agility. Because it better never will end. Because once we start to lose Agility´s core we´re losing focus of the customer.

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• first install for windows eight.....da beta

  - by raysmithequip

  The W8 preview is now installed and I am enjoying it.  I remember the learning curve of my first unix machine back in the eighties, this ain't that.It is normal for me to do the first os install with a keyboard and low end monitor...you never know what you'll encounter out in the field.  The OS took like a fish to water.  I used a low end INTEL motherboard dp55w I gathered on the cheap, an 1157 i5 from the used bin a pair of 6 gig ddr3 sticks, a rosewell 550 watt power supply a cheap used twenty buck sub 200g wd sata drive, a half working dvd burner and an asus fanless nvidia vid card, not a great one but Sub 50.00 on newey eggey...I did have to hunt the ms forums for a key and of course to activate the thing, if dos would of needed this outmoded ritual, we would still be on cpm and osborne would be a household name, of course little do people know that this ritual was common as far back as the seventies on att unix installs....not, but it was possible, I used to joke about when I ran a bbs, what hell would of been wrought had dos 3.2 machines been required to dial into my bbs to send fido mail to ms and wait for an acknowledgement.  All in all the thing was pushing a seven on the ms richter scale, not including the vid card, sadly it came in at just a tad over three....I wanted to evaluate it for a possible replacement on critical machines that in the past went down due to a vid card fan failure....you have no idea what a customer thinks when you show them a failed vid card fan..."you mean that little plastic piece of junk caused all this!!??!!!"...yea man.  Some production machines don't need any sort of vid, I will at least keep it on the maybe list for those, MTBF is a very important factor, some big box stores should put percentage of failure rate within 24 month estimates on the outside of the carton for sure.  And a warning that the power supplies are already at their limit.  Let's face it, today even 550w can be iffy.A few neat eye candy improvements over the earlier windows is nice, the metro screen is nice, anyone who has used a newer phone recently will intuitively drag their fingers across the screen....lot of good that was with no mouse or touch screen though.  Lucky me, I have been using windows since day one, I still have a copy of win 2.0 (and every other version) for no good reason.  Still the old ix collection of disks is much larger, recompiling any kernal is another silly ritual, same machine, different day, same recompile...argh. Rh is my all time fav, mandrake was always missing something, like it rewrote the init file or something, novell is ok as long as you stay on the beaten path and of course ubuntu normally recompiles with the same errors consistantly....makes life easy that way....no errors on windows eight, just a screen that did not match the installed hardware, natuarally I alt tabbed right out of it, then hit the flag key to find the start menu....no start button. I miss the start button already. Keyboard cowboy funnin and I was browsing the harddrive, nothing stunning there, I like that, means I can find stuff. Only I can't find what I want, the start button....the start menu is that first screen for touch tablets. No biggie for useruser, that is where they will want to be, I can see that. Admins won't want to be there, it is easy enough to get the control panel a bazzilion other ways though, just not the start button. (see a pattern here?). Personally, from the keyboard I find it fun to hit the carets along the location bar at the top of the explorer screen with tabs and arrows and choose SHOW ALL CONTROL PANEL ITEMS, or thereabouts. Bottom line, I love seven and I'll love eight even more!...very happy I did not have to follow the normal rule of thumb (a customer watching me build a system and asking questions said "oh I get it, so every piece you put in there is basically a hundred bucks, right?)...ok, sure, pretty much, more or less, well, ya dude.  It will be WAY past october till I get a real touch screen but I did pick up a pair of cheap tatungs so I can try the NEW main start screen, I parse a lot of folders and have a vision of how a pair of touch screens will be easier than landing a rover on mars.  Ok.  fine, they are way smallish, and I don't expect multitouch to work but we are talking a few percent of a new 21 inch viewsonic touch screen.  Will this OS be a game changer?  I don't know.  Bottom line with all the pads and droids in the world, it is more of a catch up move at first glance.  Not something ms is used to.  An app store?  I can see ms's motivation, the others have it.  I gather there will not be gadgets there, go ahead and see what ms did  to the once populated gadget page...go ahead, google gadgets and take a gander, used to hundreds of gadgets, they are already gone.  They replaced gadgets?  sort of, I'll drop that, it's a bit of a sore point for me.  More of interest was what happened when I downloaded stuff off codeplex and some other normal programs that I like, like orbitron, top o' my list!!...cardware it is...anyways, click on the exe, get a screen, normal for windows, this one indicated that I was not running a normal windows program and had a button for  exit the install, naw, I hit details, a hidden run program anyways came into view....great, my path to the normal windows has detected a program tha.....yea ok, acl is on, fine, moving along I got orbitron installed in record time and was tracking the iss on the newest Microsoft OS, beta of course, felt like the first time I setup bsd all those year ago...FUN!!...I suppose I gotta start to think about budgeting for the real os when it comes out in october, by then I should have a rasberry pi and be done with fedora remixed.  Of course that sounds like fun too!!  I would use this OS on a tablet or phone.  I don't like the idea of being hearded to an app store, don't like that on anything, we are americans and want real choices not marketed hype, lest you are younger with opm (other peoples money).   This os would be neat on a zune, but I suspect the zune is a gonner, I am rooting for microsoft, after all their default password is not admin anymore, nor alpine,  it's blank. Others force a password, my first fawn password was so long I could not even log into it with the password in front of me, who the heck uses %$# anyways, and if I was writing a brute force attack what the heck kinda impasse is that anyways at .00001 microseconds of a code execution cycle (just a non qualified number, not a real clock speed)....AI is where it will be before too long, MS is on that path, perhaps soon someone will sit down and write an app for the kinect that watches your eyes while you scan the new main start screen, clicking on the big E icon when you blink.....boy is that going to be fun!!!! sure. Blink,dammit,blink,dammit...... OPM no doubt.I like windows eight, we are moving forwards, better keep a close eye on ubuntu.  The real clinch comes when open source becomes paid source......don't blink, I already see plenty of very expensive 'ix apps, some even in app stores already.  more to come.......

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• Day 2 - Game Design Documentation

  - by dapostolov

  So yesterday I didn't cut any code for my game but I was able to do a tiny bit of research on the XNA Game Development Technology and the communities out there and do you know what? I feel I'm a bit closer to my goal. The bad news is today I didn't cut code either. However, not all is lost because I wanted to get my ideas on paper and today I just did that.  Today, I began to jot down notes about the game and how I felt the visual elements would interact with each other. Unlike my workplace, my personal level of documentation is nothing more than a task list or a mind map of my ideas; it helps me streamline my solutions quiet effectively and circumvent the long process of articulating each thought to the n-th degree. I truly dislike documentation (because I have an extremely hard time articulating my thought and solutions); however, because I tend to do a really good job with documentation I tend to get stuck writing the buggers. But as a generalist remark: 'No Developer likes documentation.' For now let's stick with my basic notes and call this post a living document. Here are my notes, fresh, from after watching the new first episode of Merlin second season! Actually, a quick recommendation to anyone who is reading this (if anyone is): I truly recommend you envelope yourself in the medium or task you're trying to tackle. Be one with moment and feel it! For instance: Are you writing a fantasy script / game? What would the music of the genre sound like? For me the Conan the Barbarian soundtrack by Basil Poledouris is frackin awesome. There are many other good CD's out there, which I listen to (some who even use medival instruments, but Conan I keep returning to. It's a creative trigger for me. Ask yourself what would the imagery look like? Time to surf google for artist renditions of fantasy! What would the game feel like? Start playing some of your favorite games that inspire you, be wary though, have some self control and don't let it absorb your time. Anyhow, onto the documentation... Screens, Scenes, and Sprites. Oh My! (groan...) The first thing that came to mind were the screens, I thought the following would suffice: Menu Screen Character Customisation Screen Loading Screen? Battle Ground The Menu Screen Ok. So, the thought here is when the game loads a huge title is displayed: Wizard Wars. The player is prompted with 3 menu items: 1 Player Game, 2 Player Game, and Exit. Since I'm targetting the PC platform, as a non-networked game to start, I picture myself running my mouse over each menu option and the visual element of the menu item changes, along with a sound to indicate that I am over a curent menu item. And as I move my mouse away, it changes back, and possibly an exit mouse sound. Maybe on the screen somewhere is a brazier alit with a magical tome open right beside it, OR, maybe the tome is the menu! I hear the menu music as mellow, not obtrusive or piercing. On a menu item select, a confirmation sound bellows to indicate the players selection. The Esc key will always return me to the previous screens or desktop. The menu screen must feel...dark, like a really important ritual is about to happen and thus the music should build up. 1 Player Game - > Customize Character(s) 2 Player Game - > Customize Character(s) Exit - > Back to Windows Notes: So the first thing I pick up here are a couple things: First and foremost, my artistic abilities suck crap, so I may have to hire an artist (now that i've said that, lets get techy) graphical objects will be positioned within a scene on each screen / window. Menu items will be represented grapically, possibly animated, and have sound / animation effects triggered by user input or a time line. I have an animated scene involving a brazier or fire on a stick IF I was to move this game to the xbox, I'd have to track which menu item is currently selected (unless I do a mouse pointer type thing.) WindowObject has a scene A Scene has many GameObjects GameObject has a position graphic or animation MenuObject is a GameObject which has a mouse in, mouse out, and click event which either does something graphically (animation), does something with sound, or moves to another screen.  Character Customisation Screen With either the 1 or 2 player option selected, both selections will come to this screen; a wizard requires a name, powers, and vestements of course! Player one will configure his character first and then player two. I considered a split screen for PC but to have two people fighting over a keyboard would probably suck. For XBox, a split screen could work; maybe when I get into the networking portion (phase 2 blog?) of this game I will remove the 2 player option for PC and provide only multiplayer and I will leave 2 player for xbox...hmm... Anyhow...I picture the creation process as follows: Name: (textbox / keyboard entry) - for xbox, this would have to be different. Robe Color: (color box, or something) Stats: Speed, Oomph, and Health. (as sliders) 1 as minimum and 10 as maximum. Ok, Back, and Cancel buttons / options. Each stat has a benefit which are listed below. The idea is the player decides if he wants his wizard to run fast, be a tank and ... hit with a purse.Regardless, the player will have a pool of 12 points to use. Ideally, A balanced wizard will have 5 in each attribute. Spells? The only spell of choice is a ball of fire which comes without question. The music and screen should still feel like a ritual. The Character Speed Basically, how fast your character moves and casts. Oomph (Best Monster Truck Voice): PURE POWAH!!! The damage output of your fireball. Health How much damage you can take. Notes: I realise the game dynamics may sound uninteresting at the moment; but I think after a couple releases, we could have some other grand ideas such as: saved profiles, gold to upgrade arsenal of spells, talents, etc...but for now...a vanilla fireball thrower mage will suffice for this experiment. OK. So... a MenuObject  may need to be loosely coupled to allow future items such as networking? may be a button? a CharacterObject has a name speed oomph health and a funky robe color. cap on the three stats (1-10) an arsenal of 1 spell (possibly could expand this) The Loading Screen As is. The Battleground Screen For now, I'm keeping the screen as max resolution for the PC. The screen isn't going to move or even be a split screen. I'm not aiming high here because I want to see what level of change is involved when new features / concepts are added to game content. I'm interested to find out if we could apply techniques such as MVC or MVVM to this type of development or is it too tightly coupled? This reminds me when when my best friend and I were brainstorming our game idea (this is going back a while...1994, 6?) and he cringed at the thought of bringing business technology into games, especially when I suggested a database to store character information and COM / DCOM as the medium, but it seems I wasn't far off (reflecting); just like his implementation of a xml "config file" for dynamic direct-x menus back before .net in 1999...anyhow...i digress... The Battle One screen, two characters lobing balls of fire at each other...It doesn't get better than that. Every so often a scroll appears...and the fireballs bounce off walls, or the wizard has rapid fire, or even scrolls of healing! The scroll options are endless. Two bars at the top, each the color of the wizard (with their name beside the bar) indicate how much health they have. Possibly the appearance of the scrolls means the battle is taking too long? I'm thinking 1 player controls: up, down, left, right and space to fire the button. Or even possibly, mouse click and shift - mouse button to fire a spell in the direction they are facing. Two player controls: a, s, d, f and space AND arrows (up, down, left, right) and Del key or Crtl. The game ends when a player has 0 health and a dialog box appears asking for a rematch / reconfigure / exit. Health goes down when a fireball (friendly or not), connects with a wizard. When a wizard connects with a scroll, a countdown clock / icon appears near the health bar and the wizard begins to glow. For the most part, a wizard can have only scroll 1 effect on him at a time. Notes: Ok, there's alot to cover here. a CharacterObject is a GameObject it travels at a set velocity it travels in a direction it has sounds (walking, running, casting, impact, dying, laughing, whistling, other?) it has animations (walking, running, casting, impact, dying, laughing, idle, other?) it has a lifespan (determined by health) it is alive or dead it has a position a ScrollObject is a GameObject it carries a transferance of points "damage" (or healing, bad scroll effect?) (determinde by caster) it carries a transferance of "other" it is stationary it has a sound on impact it has a stationary animation it has an impact animation / or transfers an impact animation it has a fade animation? it has a lifespan (determined by game) it is alive or dead it has a position a WallObject is a GameObject it has a sound on fireball impact? it is a still image / stationary it has an impact animation / or transfers an impact animation it is dead it has a position A FireBall is a GameObject it carries a transferance of poinst "damage" (or healing, bad scroll effect?) (determinde by caster) it travels at a set velocity it travels in a direction it has a sound it has a travel animation it has an impact animation / or transfers an impact animation it has a fade animation? it has a lifespan (determined by caster) it is alive or dead it has a position As I look at this, I can see some common attributes in each object that I can carry up to the GameObject. I think I'm going to end the documentation here, it's taken me a bit of time to type this all out, tomorrow. I'll load up my IDE and my paint studio to get some good old fashioned cowboy hacking going!   D.

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• Calling Web Service Functions Asynchronously from a Web Page

  - by SGWellens

  Over on the Asp.Net forums where I moderate, a user had a problem calling a Web Service from a web page asynchronously. I tried his code on my machine and was able to reproduce the problem. I was able to solve his problem, but only after taking the long scenic route through some of the more perplexing nuances of Web Services and Proxies. Here is the fascinating story of that journey. Start with a simple Web Service     public class Service1 : System.Web.Services.WebService    {        [WebMethod]        public string HelloWorld()        {            // sleep 10 seconds            System.Threading.Thread.Sleep(10 * 1000);            return "Hello World";        }    } The 10 second delay is added to make calling an asynchronous function more apparent. If you don't call the function asynchronously, it takes about 10 seconds for the page to be rendered back to the client. If the call is made from a Windows Forms application, the application freezes for about 10 seconds. Add the web service to a web site. Right-click the project and select "Add Web Reference…" Next, create a web page to call the Web Service. Note: An asp.net web page that calls an 'Async' method must have the Async property set to true in the page's header: <%@ Page Language="C#"          AutoEventWireup="true"          CodeFile="Default.aspx.cs"          Inherits="_Default"           Async='true'  %> Here is the code to create the Web Service proxy and connect the event handler. Shrewdly, we make the proxy object a member of the Page class so it remains instantiated between the various events. public partial class _Default : System.Web.UI.Page {    localhost.Service1 MyService;  // web service proxy     // ---- Page_Load ---------------------------------     protected void Page_Load(object sender, EventArgs e)    {        MyService = new localhost.Service1();        MyService.HelloWorldCompleted += EventHandler;          } Here is the code to invoke the web service and handle the event:     // ---- Async and EventHandler (delayed render) --------------------------     protected void ButtonHelloWorldAsync_Click(object sender, EventArgs e)    {        // blocks        ODS("Pre HelloWorldAsync...");        MyService.HelloWorldAsync();        ODS("Post HelloWorldAsync");    }    public void EventHandler(object sender, localhost.HelloWorldCompletedEventArgs e)    {        ODS("EventHandler");        ODS("    " + e.Result);    }     // ---- ODS ------------------------------------------------    //    // Helper function: Output Debug String     public static void ODS(string Msg)    {        String Out = String.Format("{0}  {1}", DateTime.Now.ToString("hh:mm:ss.ff"), Msg);        System.Diagnostics.Debug.WriteLine(Out);    } I added a utility function I use a lot: ODS (Output Debug String). Rather than include the library it is part of, I included it in the source file to keep this example simple. Fire up the project, open up a debug output window, press the button and we get this in the debug output window: 11:29:37.94 Pre HelloWorldAsync... 11:29:37.94 Post HelloWorldAsync 11:29:48.94 EventHandler 11:29:48.94 Hello World   Sweet. The asynchronous call was made and returned immediately. About 10 seconds later, the event handler fires and we get the result. Perfect….right? Not so fast cowboy. Watch the browser during the call: What the heck? The page is waiting for 10 seconds. Even though the asynchronous call returned immediately, Asp.Net is waiting for the event to fire before it renders the page. This is NOT what we wanted. I experimented with several techniques to work around this issue. Some may erroneously describe my behavior as 'hacking' but, since no ingesting of Twinkies was involved, I do not believe hacking is the appropriate term. If you examine the proxy that was automatically created, you will find a synchronous call to HelloWorld along with an additional set of methods to make asynchronous calls. I tried the other asynchronous method supplied in the proxy:     // ---- Begin and CallBack ----------------------------------     protected void ButtonBeginHelloWorld_Click(object sender, EventArgs e)    {        ODS("Pre BeginHelloWorld...");        MyService.BeginHelloWorld(AsyncCallback, null);        ODS("Post BeginHelloWorld");    }    public void AsyncCallback(IAsyncResult ar)    {        String Result = MyService.EndHelloWorld(ar);         ODS("AsyncCallback");        ODS("    " + Result);    } The BeginHelloWorld function in the proxy requires a callback function as a parameter. I tested it and the debug output window looked like this: 04:40:58.57 Pre BeginHelloWorld... 04:40:58.57 Post BeginHelloWorld 04:41:08.58 AsyncCallback 04:41:08.58 Hello World It works the same as before except for one critical difference: The page rendered immediately after the function call. I was worried the page object would be disposed after rendering the page but the system was smart enough to keep the page object in memory to handle the callback. Both techniques have a use: Delayed Render: Say you want to verify a credit card, look up shipping costs and confirm if an item is in stock. You could have three web service calls running in parallel and not render the page until all were finished. Nice. You can send information back to the client as part of the rendered page when all the services are finished. Immediate Render: Say you just want to start a service running and return to the client. You can do that too. However, the page gets sent to the client before the service has finished running so you will not be able to update parts of the page when the service finishes running. Summary: YourFunctionAsync() and an EventHandler will not render the page until the handler fires. BeginYourFunction() and a CallBack function will render the page as soon as possible. I found all this to be quite interesting and did a lot of searching and researching for documentation on this subject….but there isn't a lot out there. The biggest clues are the parameters that can be sent to the WSDL.exe program: http://msdn.microsoft.com/en-us/library/7h3ystb6(VS.100).aspx Two parameters are oldAsync and newAsync. OldAsync will create the Begin/End functions; newAsync will create the Async/Event functions. Caveat: I haven't tried this but it was stated in this article. I'll leave confirming this as an exercise for the student J. Included Code: I'm including the complete test project I created to verify the findings. The project was created with VS 2008 SP1. There is a solution file with 3 projects, the 3 projects are: Web Service Asp.Net Application Windows Forms Application To decide which program runs, you right-click a project and select "Set as Startup Project". I created and played with the Windows Forms application to see if it would reveal any secrets. I found that in the Windows Forms application, the generated proxy did NOT include the Begin/Callback functions. Those functions are only generated for Asp.Net pages. Probably for the reasons discussed earlier. Maybe those Microsoft boys and girls know what they are doing. I hope someone finds this useful. Steve Wellens

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• Parallelism in .NET – Part 8, PLINQ’s ForAll Method

  - by Reed

  Parallel LINQ extends LINQ to Objects, and is typically very similar.  However, as I previously discussed, there are some differences.  Although the standard way to handle simple Data Parellelism is via Parallel.ForEach, it’s possible to do the same thing via PLINQ. PLINQ adds a new method unavailable in standard LINQ which provides new functionality… LINQ is designed to provide a much simpler way of handling querying, including filtering, ordering, grouping, and many other benefits.  Reading the description in LINQ to Objects on MSDN, it becomes clear that the thinking behind LINQ deals with retrieval of data.  LINQ works by adding a functional programming style on top of .NET, allowing us to express filters in terms of predicate functions, for example. PLINQ is, generally, very similar.  Typically, when using PLINQ, we write declarative statements to filter a dataset or perform an aggregation.  However, PLINQ adds one new method, which provides a very different purpose: ForAll. The ForAll method is defined on ParallelEnumerable, and will work upon any ParallelQuery<T>.  Unlike the sequence operators in LINQ and PLINQ, ForAll is intended to cause side effects.  It does not filter a collection, but rather invokes an action on each element of the collection. At first glance, this seems like a bad idea.  For example, Eric Lippert clearly explained two philosophical objections to providing an IEnumerable<T>.ForEach extension method, one of which still applies when parallelized.  The sole purpose of this method is to cause side effects, and as such, I agree that the ForAll method “violates the functional programming principles that all the other sequence operators are based upon”, in exactly the same manner an IEnumerable<T>.ForEach extension method would violate these principles.  Eric Lippert’s second reason for disliking a ForEach extension method does not necessarily apply to ForAll – replacing ForAll with a call to Parallel.ForEach has the same closure semantics, so there is no loss there. Although ForAll may have philosophical issues, there is a pragmatic reason to include this method.  Without ForAll, we would take a fairly serious performance hit in many situations.  Often, we need to perform some filtering or grouping, then perform an action using the results of our filter.  Using a standard foreach statement to perform our action would avoid this philosophical issue: // Filter our collection var filteredItems = collection.AsParallel().Where( i => i.SomePredicate() ); // Now perform an action foreach (var item in filteredItems) { // These will now run serially item.DoSomething(); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This would cause a loss in performance, since we lose any parallelism in place, and cause all of our actions to be run serially. We could easily use a Parallel.ForEach instead, which adds parallelism to the actions: // Filter our collection var filteredItems = collection.AsParallel().Where( i => i.SomePredicate() ); // Now perform an action once the filter completes Parallel.ForEach(filteredItems, item => { // These will now run in parallel item.DoSomething(); }); This is a noticeable improvement, since both our filtering and our actions run parallelized.  However, there is still a large bottleneck in place here.  The problem lies with my comment “perform an action once the filter completes”.  Here, we’re parallelizing the filter, then collecting all of the results, blocking until the filter completes.  Once the filtering of every element is completed, we then repartition the results of the filter, reschedule into multiple threads, and perform the action on each element.  By moving this into two separate statements, we potentially double our parallelization overhead, since we’re forcing the work to be partitioned and scheduled twice as many times. This is where the pragmatism comes into play.  By violating our functional principles, we gain the ability to avoid the overhead and cost of rescheduling the work: // Perform an action on the results of our filter collection .AsParallel() .Where( i => i.SomePredicate() ) .ForAll( i => i.DoSomething() ); The ability to avoid the scheduling overhead is a compelling reason to use ForAll.  This really goes back to one of the key points I discussed in data parallelism: Partition your problem in a way to place the most work possible into each task.  Here, this means leaving the statement attached to the expression, even though it causes side effects and is not standard usage for LINQ. This leads to my one guideline for using ForAll: The ForAll extension method should only be used to process the results of a parallel query, as returned by a PLINQ expression. Any other usage scenario should use Parallel.ForEach, instead.

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• Algorithmia Source Code released on CodePlex

  - by FransBouma

  Following the release of our BCL Extensions Library on CodePlex, we have now released the source-code of Algorithmia on CodePlex! Algorithmia is an algorithm and data-structures library for .NET 3.5 or higher and is one of the pillars LLBLGen Pro v3's designer is built on. The library contains many data-structures and algorithms, and the source-code is well documented and commented, often with links to official descriptions and papers of the algorithms and data-structures implemented. The source-code is shared using Mercurial on CodePlex and is licensed under the friendly BSD2 license. User documentation is not available at the moment but will be added soon. One of the main design goals of Algorithmia was to create a library which contains implementations of well-known algorithms which weren't already implemented in .NET itself. This way, more developers out there can enjoy the results of many years of what the field of Computer Science research has delivered. Some algorithms and datastructures are known in .NET but are re-implemented because the implementation in .NET isn't efficient for many situations or lacks features. An example is the linked list in .NET: it doesn't have an O(1) concat operation, as every node refers to the containing LinkedList object it's stored in. This is bad for algorithms which rely on O(1) concat operations, like the Fibonacci heap implementation in Algorithmia. Algorithmia therefore contains a linked list with an O(1) concat feature. The following functionality is available in Algorithmia: Command, Command management. This system is usable to build a fully undo/redo aware system by building your object graph using command-aware classes. The Command pattern is implemented using a system which allows transparent undo-redo and command grouping so you can use it to make a class undo/redo aware and set properties, use its contents without using commands at all. The Commands namespace is the namespace to start. Classes you'd want to look at are CommandifiedMember, CommandifiedList and KeyedCommandifiedList. See the CommandQueueTests in the test project for examples. Graphs, Graph algorithms. Algorithmia contains a sophisticated graph class hierarchy and algorithms implemented onto them: non-directed and directed graphs, as well as a subgraph view class, which can be used to create a view onto an existing graph class which can be self-maintaining. Algorithms include transitive closure, topological sorting and others. A feature rich depth-first search (DFS) crawler is available so DFS based algorithms can be implemented quickly. All graph classes are undo/redo aware, as they can be set to be 'commandified'. When a graph is 'commandified' it will do its housekeeping through commands, which makes it fully undo-redo aware, so you can remove, add and manipulate the graph and undo/redo the activity automatically without any extra code. If you define the properties of the class you set as the vertex type using CommandifiedMember, you can manipulate the properties of vertices and the graph contents with full undo/redo functionality without any extra code. Heaps. Heaps are data-structures which have the largest or smallest item stored in them always as the 'root'. Extracting the root from the heap makes the heap determine the next in line to be the 'maximum' or 'minimum' (max-heap vs. min-heap, all heaps in Algorithmia can do both). Algorithmia contains various heaps, among them an implementation of the Fibonacci heap, one of the most efficient heap datastructures known today, especially when you want to merge different instances into one. Priority queues. Priority queues are specializations of heaps. Algorithmia contains a couple of them. Sorting. What's an algorithm library without sort algorithms? Algorithmia implements a couple of sort algorithms which sort the data in-place. This aspect is important in situations where you want to sort the elements in a buffer/list/ICollection in-place, so all data stays in the data-structure it already is stored in. PropertyBag. It re-implements Tony Allowatt's original idea in .NET 3.5 specific syntax, which is to have a generic property bag and to be able to build an object in code at runtime which can be bound to a property grid for editing. This is handy for when you have data / settings stored in XML or other format, and want to create an editable form of it without creating many editors. IEditableObject/IDataErrorInfo implementations. It contains default implementations for IEditableObject and IDataErrorInfo (EditableObjectDataContainer for IEditableObject and ErrorContainer for IDataErrorInfo), which make it very easy to implement these interfaces (just a few lines of code) without having to worry about bookkeeping during databinding. They work seamlessly with CommandifiedMember as well, so your undo/redo aware code can use them out of the box. EventThrottler. It contains an event throttler, which can be used to filter out duplicate events in an event stream coming into an observer from an event. This can greatly enhance performance in your UI without needing to do anything other than hooking it up so it's placed between the event source and your real handler. If your UI is flooded with events from data-structures observed by your UI or a middle tier, you can use this class to filter out duplicates to avoid redundant updates to UI elements or to avoid having observers choke on many redundant events. Small, handy stuff. A MultiValueDictionary, which can store multiple unique values per key, instead of one with the default Dictionary, and is also merge-aware so you can merge two into one. A Pair class, to quickly group two elements together. Multiple interfaces for helping with building a de-coupled, observer based system, and some utility extension methods for the defined data-structures. We regularly update the library with new code. If you have ideas for new algorithms or want to share your contribution, feel free to discuss it on the project's Discussions page or send us a pull request. Enjoy!

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• Extreme Optimization – Numerical Algorithm Support

  - by JoshReuben

  Function Delegates Many calculations involve the repeated evaluation of one or more user-supplied functions eg Numerical integration. The EO MathLib provides delegate types for common function signatures and the FunctionFactory class can generate new delegates from existing ones. RealFunction delegate - takes one Double parameter – can encapsulate most of the static methods of the System.Math class, as well as the classes in the Extreme.Mathematics.SpecialFunctions namespace: var sin = new RealFunction(Math.Sin); var result = sin(1); BivariateRealFunction delegate - takes two Double parameters: var atan2 = new BivariateRealFunction (Math.Atan2); var result = atan2(1, 2); TrivariateRealFunction delegate – represents a function takes three Double arguments ParameterizedRealFunction delegate - represents a function taking one Integer and one Double argument that returns a real number. The Pow method implements such a function, but the arguments need order re-arrangement: static double Power(int exponent, double x) { return ElementaryFunctions.Pow(x, exponent); } ... var power = new ParameterizedRealFunction(Power); var result = power(6, 3.2); A ComplexFunction delegate - represents a function that takes an Extreme.Mathematics.DoubleComplex argument and also returns a complex number. MultivariateRealFunction delegate - represents a function that takes an Extreme.Mathematics.LinearAlgebra.Vector argument and returns a real number. MultivariateVectorFunction delegate - represents a function that takes a Vector argument and returns a Vector. FastMultivariateVectorFunction delegate - represents a function that takes an input Vector argument and an output Matrix argument – avoiding object construction  The FunctionFactory class RealFromBivariateRealFunction and RealFromParameterizedRealFunction helper methods - transform BivariateRealFunction or a ParameterizedRealFunction into a RealFunction delegate by fixing one of the arguments, and treating this as a new function of a single argument. var tenthPower = FunctionFactory.RealFromParameterizedRealFunction(power, 10); var result = tenthPower(x); Note: There is no direct way to do this programmatically in C# - in F# you have partial value functions where you supply a subset of the arguments (as a travelling closure) that the function expects. When you omit arguments, F# generates a new function that holds onto/remembers the arguments you passed in and "waits" for the other parameters to be supplied. let sumVals x y = x + y     let sumX = sumVals 10     // Note: no 2nd param supplied.     // sumX is a new function generated from partially applied sumVals.     // ie "sumX is a partial application of sumVals." let sum = sumX 20     // Invokes sumX, passing in expected int (parameter y from original)  val sumVals : int -> int -> int val sumX : (int -> int) val sum : int = 30 RealFunctionsToVectorFunction and RealFunctionsToFastVectorFunction helper methods - combines an array of delegates returning a real number or a vector into vector or matrix functions. The resulting vector function returns a vector whose components are the function values of the delegates in the array. var funcVector = FunctionFactory.RealFunctionsToVectorFunction(     new MultivariateRealFunction(myFunc1),     new MultivariateRealFunction(myFunc2));  The IterativeAlgorithm<T> abstract base class Iterative algorithms are common in numerical computing - a method is executed repeatedly until a certain condition is reached, approximating the result of a calculation with increasing accuracy until a certain threshold is reached. If the desired accuracy is achieved, the algorithm is said to converge. This base class is derived by many classes in the Extreme.Mathematics.EquationSolvers and Extreme.Mathematics.Optimization namespaces, as well as the ManagedIterativeAlgorithm class which contains a driver method that manages the iteration process.  The ConvergenceTest abstract base class This class is used to specify algorithm Termination , convergence and results - calculates an estimate for the error, and signals termination of the algorithm when the error is below a specified tolerance. Termination Criteria - specify the success condition as the difference between some quantity and its actual value is within a certain tolerance – 2 ways: absolute error - difference between the result and the actual value. relative error is the difference between the result and the actual value relative to the size of the result. Tolerance property - specify trade-off between accuracy and execution time. The lower the tolerance, the longer it will take for the algorithm to obtain a result within that tolerance. Most algorithms in the EO NumLib have a default value of MachineConstants.SqrtEpsilon - gives slightly less than 8 digits of accuracy. ConvergenceCriterion property - specify under what condition the algorithm is assumed to converge. Using the ConvergenceCriterion enum: WithinAbsoluteTolerance / WithinRelativeTolerance / WithinAnyTolerance / NumberOfIterations Active property - selectively ignore certain convergence tests Error property - returns the estimated error after a run MaxIterations / MaxEvaluations properties - Other Termination Criteria - If the algorithm cannot achieve the desired accuracy, the algorithm still has to end – according to an absolute boundary. Status property - indicates how the algorithm terminated - the AlgorithmStatus enum values:NoResult / Busy / Converged (ended normally - The desired accuracy has been achieved) / IterationLimitExceeded / EvaluationLimitExceeded / RoundOffError / BadFunction / Divergent / ConvergedToFalseSolution. After the iteration terminates, the Status should be inspected to verify that the algorithm terminated normally. Alternatively, you can set the ThrowExceptionOnFailure to true. Result property - returns the result of the algorithm. This property contains the best available estimate, even if the desired accuracy was not obtained. IterationsNeeded / EvaluationsNeeded properties - returns the number of iterations required to obtain the result, number of function evaluations.  Concrete Types of Convergence Test classes SimpleConvergenceTest class - test if a value is close to zero or very small compared to another value. VectorConvergenceTest class - test convergence of vectors. This class has two additional properties. The Norm property specifies which norm is to be used when calculating the size of the vector - the VectorConvergenceNorm enum values: EuclidianNorm / Maximum / SumOfAbsoluteValues. The ErrorMeasure property specifies how the error is to be measured – VectorConvergenceErrorMeasure enum values: Norm / Componentwise ConvergenceTestCollection class - represent a combination of tests. The Quantifier property is a ConvergenceTestQuantifier enum that specifies how the tests in the collection are to be combined: Any / All  The AlgorithmHelper Class inherits from IterativeAlgorithm<T> and exposes two methods for convergence testing. IsValueWithinTolerance<T> method - determines whether a value is close to another value to within an algorithm's requested tolerance. IsIntervalWithinTolerance<T> method - determines whether an interval is within an algorithm's requested tolerance.

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• Why not .NET-style delegates rather than closures in Java?

  - by h2g2java

  OK, this is going to be my beating a dying horse for the 3rd time. However, this question is different from my earlier two about closures/delegates, which asks about plans for delegates and what are the projected specs and implementation for closures. This question is about - why is the Java community struggling to define 3 different types of closures when we could simply steal the whole concept of delegates lock, stock and barrel from our beloved and friendly neighbour - Microsoft. There are two non-technical conclusions I would be very tempted to jump into: The Java community should hold up its pride, at the cost of needing to go thro convoluted efforts, by not succumbing to borrowing any Microsoft concepts or otherwise vindicate Microsoft's brilliance. Delegates is a Microsoft patented technology. Alright, besides the above two possibilities, Q1. Is there any weakness or inadequacy in msft-styled delegates that the three (or more) forms of closures would be addressing? Q2. I am asking this while shifting between java and c# and it intrigues me that c# delegates does exactly what I needed. Are there features that would be implemented in closures that are not currently available in C# delegates? If so what are they because I cannot see what I need more than what C# delegates has adequately provided me? Q3. I know that one of the concerns about implementing closures/delegates in java is the reduction of orthogonality of the language, where more than one way is exposed to perform a particular task. Is it worth the level convolution and time spent to avoid delegates just to ensure java retains its level of orthogonality? In SQL, we know that it is advisable to break orthogonality by frequently adequately satisfying only the 2nd normal form. Why can't java be subjected to reduction of orthogonality and OO-ness for the sake of simplicity? Q4. The architecture of JVM is technically constrained from implementing .NET-styled delegates. If this reason WERE (subjunctive to emphasize unlikelihood) true, then why can't the three closures proposals be hidden behind a simple delegate keyword or annotation: if we don't like to use @delegate, we could use @method. I cannot see how delegate statement format is more complex than the three closure proposals.

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• Javascript closures with google geocoder

  - by DaNieL

  Hi all, i still have some problems with javascript closures, and input/output variables. Im playing with google maps api for a no profit project: users will place the marker into a gmap, and I have to save the locality (with coordinates) in my db. The problem comes when i need to do a second geocode in order to get a unique pairs of lat and lng for a location: lets say two users place the marker in the same town but in different places, I dont want to have the same locality twice in the database with differents coords. I know i can do the second geocode after the user select the locality, but i want to understand what am i mistaking here: // First geocoding, take the marker coords to get locality. geocoder.geocode( { 'latLng': new google.maps.LatLng($("#lat").val(), $("#lng").val()), 'language': 'it' }, function(results_1, status_1){ // initialize the html var inside this closure var html = ''; if(status_1 == google.maps.GeocoderStatus.OK) { // do stuff here for(i = 0, geolen = results_1[0].address_components.length; i != geolen) { // Second type of geocoding: for each location from the first geocoding, // i want to have a unique [lat,lan] geocoder.geocode( { 'address': results_1[0].address_components[i].long_name }, function(results_2, status_2){ // Here come the problem. I need to have the long_name here, and // 'html' var should increment. coords = results_2[0].geometry.location.toUrlValue(); html += 'some html to let the user choose the locality'; } ); } // Finally, insert the 'html' variable value into my dom... //but it never gets updated! } else { alert("Error from google geocoder:" + status_1) } } ); I tryed with: // Second type of geocoding: for each location from the first geocoding, i want // to have a unique [lat,lan] geocoder.geocode( { 'address': results_1[0].address_components[i].long_name }, (function(results_2, status_2, long_name){ // But in this way i'll never get results_2 or status_2, well, results_2 // get long_name value, status_2 and long_name is undefined. // However, html var is correctly updated. coords = results_2[0].geometry.location.toUrlValue(); html += 'some html to let the user choose the locality'; })(results_1[0].address_components[i].long_name) ); And with: // Second type of geocoding: for each location from the first geocoding, i want to have // a unique [lat,lan] geocoder.geocode( { 'address': results_1[0].address_components[i].long_name }, (function(results_2, status_2, long_name){ // But i get an obvious "results_2 is not defined" error (same for status_2). coords = results_2[0].geometry.location.toUrlValue(); html += 'some html to let the user choose the locality, that can be more than one'; })(results_2, status_2, results_1[0].address_components[i].long_name) ); Any suggestion? EDIT: My problem is how to pass an additional arguments to the geocoder inner function: function(results_2, status_2, long_name){ //[...] } becose if i do that with a clousure, I mess with the original parameters (results_2 and status_2)

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• How to have member variables and public methods in a jQuery plugin?

  - by user169867

  I'm trying to create a jQuery plugin that will create something like an autoCompleteBox but with custom features. How do I store member variables for each matching jQuery element? For example I'll need to store a timerID for each. I'd also like to store references to some of the DOM elements that make up the control. I'd like to be able to make a public method that works something like: $("#myCtrl").autoCompleteEx.addItem("1"); But in the implementation of addItem() how can I access the member variables for that particular object like its timerID or whatever? Below is what I have so far... Thanks for any help or suggestions! (function($) { //Attach this new method to jQuery $.fn.autoCompleteEx = function(options) { //Merge Given Options W/ Defaults, But Don't Alter Either var opts = $.extend({}, $.fn.autoCompleteEx.defaults, options); //Iterate over the current set of matched elements return this.each(function() { var acx = $(this); //Get JQuery Version Of Element (Should Be Div) //Give Div Correct Class & Add <ul> w/ input item to it acx.addClass("autoCompleteEx"); acx.html("<ul><li class=\"input\"><input type=\"text\"/></li></ul>"); //Grab Input As JQ Object var input = $("input", acx); //Wireup Div acx.click(function() { input.focus().val( input.val() ); }); //Wireup Input input.keydown(function(e) { var kc = e.keyCode; if(kc == 13) //Enter { } else if(kc == 27) //Esc { } else { //Resize TextArea To Input var width = 50 + (_txtArea.val().length*10); _txtArea.css("width", width+"px"); } }); }); //End Each JQ Element }; //End autoCompleteEx() //Private Functions function junk() { }; //Public Functions $.fn.autoCompleteEx.addItem = function(id,txt) { var x = this; var y = 0; }; //Default Settings $.fn.autoCompleteEx.defaults = { minChars: 2, delay: 300, maxItems: 1 }; //End Of Closure })(jQuery);

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• Intermittent "Specified cast is invalid" with StructureMap injected data context

  - by FreshCode

  I am intermittently getting an System.InvalidCastException: Specified cast is not valid. error in my repository layer when performing an abstracted SELECT query mapped with LINQ. The error can't be caused by a mismatched database schema since it works intermittently and it's on my local dev machine. Could it be because StructureMap is caching the data context between page requests? If so, how do I tell StructureMap v2.6.1 to inject a new data context argument into my repository for each request? Update: I found this question which correlates my hunch that something was being re-used. Looks like I need to call Dispose on my injected data context. Not sure how I'm going to do this to all my repositories without copypasting a lot of code. Edit: These errors are popping up all over the place whenever I refresh my local machine too quickly. Doesn't look like it's happening on my remote deployment box, but I can't be sure. I changed all my repositories' StructureMap life cycles to HttpContextScoped() and the error persists. Code: public ActionResult Index() { // error happens here, which queries my page repository var page = _branchService.GetPage("welcome"); if (page != null) ViewData["Welcome"] = page.Body; ... } Repository: GetPage boils down to a filtered query mapping in my page repository. public IQueryable<Page> GetPages() { var pages = from p in _db.Pages let categories = GetPageCategories(p.PageId) let revisions = GetRevisions(p.PageId) select new Page { ID = p.PageId, UserID = p.UserId, Slug = p.Slug, Title = p.Title, Description = p.Description, Body = p.Text, Date = p.Date, IsPublished = p.IsPublished, Categories = new LazyList<Category>(categories), Revisions = new LazyList<PageRevision>(revisions) }; return pages; } where _db is an injected data context as an argument, stored in a private variable which I reuse for SELECT queries. Error: Specified cast is not valid. Exception Details: System.InvalidCastException: Specified cast is not valid. Stack Trace: [InvalidCastException: Specified cast is not valid.] System.Data.Linq.SqlClient.SqlProvider.Execute(Expression query, QueryInfo queryInfo, IObjectReaderFactory factory, Object[] parentArgs, Object[] userArgs, ICompiledSubQuery[] subQueries, Object lastResult) +4539 System.Data.Linq.SqlClient.SqlProvider.ExecuteAll(Expression query, QueryInfo[] queryInfos, IObjectReaderFactory factory, Object[] userArguments, ICompiledSubQuery[] subQueries) +207 System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query) +500 System.Data.Linq.DataQuery`1.System.Linq.IQueryProvider.Execute(Expression expression) +50 System.Linq.Queryable.FirstOrDefault(IQueryable`1 source) +383 Manager.Controllers.SiteController.Index() in C:\Projects\Manager\Manager\Controllers\SiteController.cs:68 lambda_method(Closure , ControllerBase , Object[] ) +79 System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +258 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +39 System.Web.Mvc.<>c__DisplayClassd.<InvokeActionMethodWithFilters>b__a() +125 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation) +640 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList`1 filters, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +312 System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +709 System.Web.Mvc.Controller.ExecuteCore() +162 System.Web.Mvc.<>c__DisplayClass8.<BeginProcessRequest>b__4() +58 System.Web.Mvc.Async.<>c__DisplayClass1.<MakeVoidDelegate>b__0() +20 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +453 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +371

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• What are the Options for Storing Hierarchical Data in a Relational Database?

  - by orangepips

  Good Overviews One more Nested Intervals vs. Adjacency List comparison: the best comparison of Adjacency List, Materialized Path, Nested Set and Nested Interval I've found. Models for hierarchical data: slides with good explanations of tradeoffs and example usage Representing hierarchies in MySQL: very good overview of Nested Set in particular Hierarchical data in RDBMSs: most comprehensive and well organized set of links I've seen, but not much in the way on explanation Options Ones I am aware of and general features: Adjacency List: Columns: ID, ParentID Easy to implement. Cheap node moves, inserts, and deletes. Expensive to find level (can store as a computed column), ancestry & descendants (Bridge Hierarchy combined with level column can solve), path (Lineage Column can solve). Use Common Table Expressions in those databases that support them to traverse. Nested Set (a.k.a Modified Preorder Tree Traversal) First described by Joe Celko - covered in depth in his book Trees and Hierarchies in SQL for Smarties Columns: Left, Right Cheap level, ancestry, descendants Compared to Adjacency List, moves, inserts, deletes more expensive. Requires a specific sort order (e.g. created). So sorting all descendants in a different order requires additional work. Nested Intervals Combination of Nested Sets and Materialized Path where left/right columns are floating point decimals instead of integers and encode the path information. Bridge Table (a.k.a. Closure Table: some good ideas about how to use triggers for maintaining this approach) Columns: ancestor, descendant Stands apart from table it describes. Can include some nodes in more than one hierarchy. Cheap ancestry and descendants (albeit not in what order) For complete knowledge of a hierarchy needs to be combined with another option. Flat Table A modification of the Adjacency List that adds a Level and Rank (e.g. ordering) column to each record. Expensive move and delete Cheap ancestry and descendants Good Use: threaded discussion - forums / blog comments Lineage Column (a.k.a. Materialized Path, Path Enumeration) Column: lineage (e.g. /parent/child/grandchild/etc...) Limit to how deep the hierarchy can be. Descendants cheap (e.g. LEFT(lineage, #) = '/enumerated/path') Ancestry tricky (database specific queries) Database Specific Notes MySQL Use session variables for Adjacency List Oracle Use CONNECT BY to traverse Adjacency Lists PostgreSQL ltree datatype for Materialized Path SQL Server General summary 2008 offers HierarchyId data type appears to help with Lineage Column approach and expand the depth that can be represented.

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• Precise explanation of JavaScript <-> DOM circular reference issue

  - by Joey Adams

  One of the touted advantages of jQuery.data versus raw expando properties (arbitrary attributes you can assign to DOM nodes) is that jQuery.data is "safe from circular references and therefore free from memory leaks". An article from Google titled "Optimizing JavaScript code" goes into more detail: The most common memory leaks for web applications involve circular references between the JavaScript script engine and the browsers' C++ objects' implementing the DOM (e.g. between the JavaScript script engine and Internet Explorer's COM infrastructure, or between the JavaScript engine and Firefox XPCOM infrastructure). It lists two examples of circular reference patterns: DOM element → event handler → closure scope → DOM DOM element → via expando → intermediary object → DOM element However, if a reference cycle between a DOM node and a JavaScript object produces a memory leak, doesn't this mean that any non-trivial event handler (e.g. onclick) will produce such a leak? I don't see how it's even possible for an event handler to avoid a reference cycle, because the way I see it: The DOM element references the event handler. The event handler references the DOM (either directly or indirectly). In any case, it's almost impossible to avoid referencing window in any interesting event handler, short of writing a setInterval loop that reads actions from a global queue. Can someone provide a precise explanation of the JavaScript ↔ DOM circular reference problem? Things I'd like clarified: What browsers are effected? A comment in the jQuery source specifically mentions IE6-7, but the Google article suggests Firefox is also affected. Are expando properties and event handlers somehow different concerning memory leaks? Or are both of these code snippets susceptible to the same kind of memory leak? // Create an expando that references to its own element. var elem = document.getElementById('foo'); elem.myself = elem; // Create an event handler that references its own element. var elem = document.getElementById('foo'); elem.onclick = function() { elem.style.display = 'none'; }; If a page leaks memory due to a circular reference, does the leak persist until the entire browser application is closed, or is the memory freed when the window/tab is closed?

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• impress.js Navigation with active class

  - by ArtGoddess

  I would like to use impress.js in order to make a website, with a navigation bar. In each slide, the corresponding anchor or div must have an "active" class, in order to achieve a different link appearance. I have followed all instructions provided here: https://github.com/Ralt/impress.js/commit/f88feb8cae704ce27bd2168bdb77768f516ac2da#L2R605 but the "active" class on the correct menu must be added. This is the code that generates the menu items. How can I add for example the "active" class in the first link? /* ************************ MENU ***************************** */ // Capitalize first letter of string // @see http://stackoverflow.com/a/1026087/851498 var capitalize = function( str ) { return str.charAt(0).toUpperCase() + str.slice(1); } // `showMenu` API function creates the menu // It defines the names of each entry by the id capitalized. var showMenu = function() { // Create the menu wrapper and the element that will be cloned // for each entry. var menu = document.createElement('div'), el = document.createElement('div'); // Apply some classes menu.className = 'menu'; el.className = 'menu-item'; // Create an element that will be the "button" and append it // to the menu var button = document.createElement('div'); button.className = 'menu-button'; button.textContent = 'Menu'; menu.appendChild(button); // Now, for each div in #impress, add an entry to the menu [].forEach.call(byId('impress').firstElementChild.children, function( child, index ) { var newEl = el.cloneNode(), i = index + 1, text = i + '. ' + capitalize(child.id); // Set the text of the new element newEl.textContent = text; // Add an onclick event to the new element // We need to use a closure to make sure the index is correct (function( index ) { newEl.addEventListener('click', function() { goto(index); }); }( index )); // And append the new element to the menu menu.appendChild(newEl); }); // And append the menu to #impress document.body.appendChild(menu); }; Then, in each click it must be removed the active class on the current, and add it to the clicked element. // Remove the active class from the current active document.querySelector( '.active' )[ 0 ].classList.remove( 'active' ); // And add it to the clicked index byId('impress').firstElementChild.children[ index ].classList.add( 'active' ); Where do I have to apply this code? Thank you!

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• Multiple Timers with setTimeInterval

  - by visibleinvisibly

  I am facing a problem with setInterval being used in a loop. I have a function subscribeFeed( ) which takes an array of urls as input. It loops through the url array and subscribes each url to getFeedAutomatically() using a setInterval function. so if three URL's are there in the array, then 3 setInterval's will be called. The problem is 1)how to distinguish which setInterval is called for which URL. 2)it is causing Runtime exception in setInterval( i guess because of closure problem in javascript) //constructor function myfeed(){ this.feedArray = []; } myfeed.prototype.constructor= myfeed; myfeed.prototype.subscribeFeed =function(feedUrl){ var i=0; var url; var count = 0; var _this = this; var feedInfo = { url : [], status : "" }; var urlinfo = []; feedUrl = (feedUrl instanceof Array) ? feedUrl : [feedUrl]; //notifyInterval = (notifyInterval instanceof Array) ? notifyInterval: [notifyInterval]; for (i = 0; i < feedUrl.length; i++) { urlinfo[i] = { url:'', notifyInterval:5000,// Default Notify/Refresh interval for the feed isenable:true, // true allows the feed to be fetched from the URL timerID: null, //default ID is null called : false, position : 0, getFeedAutomatically : function(url){ _this.getFeedUpdate(url); }, }; urlinfo[i].url = feedUrl[i].URL; //overide the default notify interval if(feedUrl[i].NotifyInterval /*&& (feedUrl[i] !=undefined)*/){ urlinfo[i].notifyInterval = feedUrl[i].NotifyInterval; } // Trigger the Feed registered event with the info about URL and status feedInfo.url[i] = feedUrl[i].URL; //Set the interval to get the feed. urlinfo[i].timerID = setInterval(function(){ urlinfo[i].getFeedAutomatically(urlinfo[i].url); }, urlinfo[i].notifyInterval); this.feedArray.push(urlinfo[i]); } } // The getFeedUpate function will make an Ajax request and coninue myfeed.prototype.getFeedUpdate = function( ){ } I am posting the same on jsfiddle http://jsfiddle.net/visibleinvisibly/S37Rj/ Thanking you in advance

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• IO::Pipe - close(<handle>) does not set $?

  - by danboo

  My understanding is that closing the handle for an IO::Pipe object should be done with the method ($fh->close) and not the built-in (close($fh)). The other day I goofed and used the built-in out of habit on a IO::Pipe object that was opened to a command that I expected to fail. I was surprised when $? was zero, and my error checking wasn't triggered. I realized my mistake. If I use the built-in, IO:Pipe can't perform the waitpid() and can't set $?. But what I was surprised by was that perl seemed to still close the pipe without setting $? via the core. I worked up a little test script to show what I mean: use 5.012; use warnings; use IO::Pipe; say 'init pipes:'; pipes(); my $fh = IO::Pipe->reader(q(false)); say 'post open pipes:'; pipes(); say 'return: ' . $fh->close; #say 'return: ' . close($fh); say 'status: ' . $?; say q(); say 'post close pipes:'; pipes(); sub pipes { for my $fd ( glob("/proc/self/fd/*") ) { say readlink($fd) if -p $fd; } say q(); } When using the method it shows the pipe being gone after the close and $? is set as I expected: init pipes: post open pipes: pipe:[992006] return: 1 status: 256 post close pipes: And, when using the built-in it also appears to close the pipe, but does not set $?: init pipes: post open pipes: pipe:[952618] return: 1 status: 0 post close pipes: It seems odd to me that the built-in results in the pipe closure, but doesn't set $?. Can anyone help explain the discrepancy? Thanks!

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• What seems to be plaguing my hard drives?

  - by Craig

  In a little bit of a tech nightmare here. I know oodles about software, not so much more than the above average user about hardware. I recently had to toss an old desktop of mine. It was gradually getting slower and slower, and after shutting the desktop down for long periods of time, it would choke up upon startup. Sometimes it'd give a disk read error, sometimes say no OS was found, etc. Restarting it about 5-15 times would eventually boot properly. Weird. I also noticed that startup programs were going missing, Dropbox was reindexing my entire folder, and Backblaze was backing up less than the number of files that it should. This lead me to believe it was probably a hard drive issue. I began to wonder why I'd have hard drive issues, and came to closure when I assumed it was because of recent power surges and outages. I'm sure that does a number on the drive. I bought a new desktop recently. It's not a beast or anything, but it's enough for what I do. It's an eMachines (I know, I know) Ultra-Slim (http://www.amazon.com/eMachines-Ultra-Slim-ER1401-57-Desktop-PC/dp/B00475OG9U). This is ideal for me because it's small and portable. It comes with an AC adapter and battery, like a laptop. Just to be safe, I bought an uninterruptable power supply on top of that. It's basically protected completely from any outages that might scramble the drive. I set this up a few days ago and for the past few days I've been perfecting settings, downloading the usual applications, etc. Two days ago, I noticed Dropbox was reindexing my entire Dropbox folder. I installed both Dropbox and Backblaze on this system, but it is very much more lightweight than the other. Only about 15 third-party applications installed. I thought that maybe Dropbox and Backblaze were stressing my system, so I turned off Backblaze. Still, Dropbox runs and comes across this infinite reindex issue. I noticed that upon a reboot recently, two applications did not start on startup either. Also, much like my old desktop, every 3rd or 4th reboot, I'll be forced into a chkdsk. This makes me incredibly nervous. What could possibly be going wrong with my old, years-old desktop that is immediately causing the same issues to my new one? I've considered all of the basics. I'm in a very air conditioned room. I take run routine virus scans. I'd like to think I take care of my systems very well. What is this issue that is haunting me? There's always the possibility that this new desktop has a junk hard drive, but it just seems way too coincidental.

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• Displaying an image on a LED matrix with a Netduino

  - by Bertrand Le Roy

  In the previous post, we’ve been flipping bits manually on three ports of the Netduino to simulate the data, clock and latch pins that a shift register expected. We did all that in order to control one line of a LED matrix and create a simple Knight Rider effect. It was rightly pointed out in the comments that the Netduino has built-in knowledge of the sort of serial protocol that this shift register understands through a feature called SPI. That will of course make our code a whole lot simpler, but it will also make it a whole lot faster: writing to the Netduino ports is actually not that fast, whereas SPI is very, very fast. Unfortunately, the Netduino documentation for SPI is severely lacking. Instead, we’ve been reliably using the documentation for the Fez, another .NET microcontroller. To send data through SPI, we’ll just need  to move a few wires around and update the code. SPI uses pin D11 for writing, pin D12 for reading (which we won’t do) and pin D13 for the clock. The latch pin is a parameter that can be set by the user. This is very close to the wiring we had before (data on D11, clock on D12 and latch on D13). We just have to move the latch from D13 to D10, and the clock from D12 to D13. The code that controls the shift register has slimmed down considerably with that change. Here is the new version, which I invite you to compare with what we had before: public class ShiftRegister74HC595 { protected SPI Spi; public ShiftRegister74HC595(Cpu.Pin latchPin) : this(latchPin, SPI.SPI_module.SPI1) { } public ShiftRegister74HC595(Cpu.Pin latchPin, SPI.SPI_module spiModule) { var spiConfig = new SPI.Configuration( SPI_mod: spiModule, ChipSelect_Port: latchPin, ChipSelect_ActiveState: false, ChipSelect_SetupTime: 0, ChipSelect_HoldTime: 0, Clock_IdleState: false, Clock_Edge: true, Clock_RateKHz: 1000 ); Spi = new SPI(spiConfig); } public void Write(byte buffer) { Spi.Write(new[] {buffer}); } } All we have to do here is configure SPI. The write method couldn’t be any simpler. Everything is now handled in hardware by the Netduino. We set the frequency to 1MHz, which is largely sufficient for what we’ll be doing, but it could potentially go much higher. The shift register addresses the columns of the matrix. The rows are directly wired to ports D0 to D7 of the Netduino. The code writes to only one of those eight lines at a time, which will make it fast enough. The way an image is displayed is that we light the lines one after the other so fast that persistence of vision will give the illusion of a stable image: foreach (var bitmap in matrix.MatrixBitmap) { matrix.OnRow(row, bitmap, true); matrix.OnRow(row, bitmap, false); row++; } Now there is a twist here: we need to run this code as fast as possible in order to display the image with as little flicker as possible, but we’ll eventually have other things to do. In other words, we need the code driving the display to run in the background, except when we want to change what’s being displayed. Fortunately, the .NET Micro Framework supports multithreading. In our implementation, we’ve added an Initialize method that spins a new thread that is tied to the specific instance of the matrix it’s being called on. public LedMatrix Initialize() { DisplayThread = new Thread(() => DoDisplay(this)); DisplayThread.Start(); return this; } I quite like this way to spin a thread. As you may know, there is another, built-in way to contextualize a thread by passing an object into the Start method. For the method to work, the thread must have been constructed with a ParameterizedThreadStart delegate, which takes one parameter of type object. I like to use object as little as possible, so instead I’m constructing a closure with a Lambda, currying it with the current instance. This way, everything remains strongly-typed and there’s no casting to do. Note that this method would extend perfectly to several parameters. Of note as well is the return value of Initialize, a common technique to add some fluency to the API and enabling the matrix to be instantiated and initialized in a single line: using (var matrix = new LedMS88SR74HC595().Initialize()) The “using” in the previous line is because we have implemented IDisposable so that the matrix kills the thread and clears the display when the user code is done with it: public void Dispose() { Clear(); DisplayThread.Abort(); } Thanks to the multi-threaded version of the matrix driver class, we can treat the display as a simple bitmap with a very synchronous programming model: matrix.Set(someimage); while (button.Read()) { Thread.Sleep(10); } Here, the call into Set returns immediately and from the moment the bitmap is set, the background display thread will constantly continue refreshing no matter what happens in the main thread. That enables us to wait or read a button’s port on the main thread knowing that the current image will continue displaying unperturbed and without requiring manual refreshing. We’ve effectively hidden the implementation of the display behind a convenient, synchronous-looking API. Pretty neat, eh? Before I wrap up this post, I want to talk about one small caveat of using SPI rather than driving the shift register directly: when we got to the point where we could actually display images, we noticed that they were a mirror image of what we were sending in. Oh noes! Well, the reason for it is that SPI is sending the bits in a big-endian fashion, in other words backwards. Now sure you could fix that in software by writing some bit-level code to reverse the bits we’re sending in, but there is a far more efficient solution than that. We are doing hardware here, so we can simply reverse the order in which the outputs of the shift register are connected to the columns of the matrix. That’s switching 8 wires around once, as compared to doing bit operations every time we send a line to display. All right, so bringing it all together, here is the code we need to write to display two images in succession, separated by a press on the board’s button: var button = new InputPort(Pins.ONBOARD_SW1, false, Port.ResistorMode.Disabled); using (var matrix = new LedMS88SR74HC595().Initialize()) { // Oh, prototype is so sad! var sad = new byte[] { 0x66, 0x24, 0x00, 0x18, 0x00, 0x3C, 0x42, 0x81 }; DisplayAndWait(sad, matrix, button); // Let's make it smile! var smile = new byte[] { 0x42, 0x18, 0x18, 0x81, 0x7E, 0x3C, 0x18, 0x00 }; DisplayAndWait(smile, matrix, button); } And here is a video of the prototype running: The prototype in action I’ve added an artificial delay between the display of each row of the matrix to clearly show what’s otherwise happening very fast. This way, you can clearly see each of the two images being displayed line by line. Next time, we’ll do no hardware changes, focusing instead on building a nice programming model for the matrix, with sprites, text and hardware scrolling. Fun stuff. By the way, can any of my reader guess where we’re going with all that? The code for this prototype can be downloaded here: http://weblogs.asp.net/blogs/bleroy/Samples/NetduinoLedMatrixDriver.zip

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• Where are classpath, path and pathelement documented in Ant version 1.8.0?

  - by Robert Menteer

  I'm looking over the documentation that comes with Apache Ant version 1.8.0 and can't find where classpath, path and pathelement are documented. I've found a page that describes path like structures but it doesn't list the valid attributes or nested elements for these. Another thing I can't find in the documentation is a description of the relationships between filelist, fileset, patternset and path and how to convert them back and forth. For instance there has to be an easier way to compile only those classes in one package while removing all class dependencies on the package classes and update documentation. <!-- Get list of files in which we're interested. --> <fileset id = "java.source.set" dir = "${src}"> <include name = "**/Package/*.java" /> </fileset> <!-- Get a COMMA separated list of classes to compile. --> <pathconvert property = "java.source.list" refid = "java.source.set" pathsep = ","> <globmapper from = "${src}/*.@{src.extent}" to = "*.class" /> </pathconvert> <!-- Remove ALL dependencies on package classes. --> <depend srcdir = "${src}" destdir = "${build}" includes = "${java.source.list}" closure = "yes" /> <!-- Get a list of up to date classes. --> <fileset id = "class.uptodate.set" dir = "${build}"> <include name = "**/*.class" /> </fileset> <!-- Get list of source files for up to date classes. --> <pathconvert property = "java.uptodate.list" refid = "class.uptodate.set" pathsep = ","> <globmapper from="${build}/*.class" to="*.java" /> </pathconvert> <!-- Compile only those classes in package that are not up to date. --> <javac srcdir = "${src}" destdir = "${build}" classpathref = "compile.classpath" includes = "${java.source.list}" excludes = "${java.uptodate.list}"/> <!-- Get list of directories of class files for package. --: <pathconvert property = "class.dir.list" refid = "java.source.set" pathsep = ","> <globmapper from = "${src}/*.java" to = "${build}*" /> </pathconvert> <!-- Convert directory list to path. --> <path id = "class.dirs.path"> <dirset dir = "${build}" includes = "class.dir.list" /> </path> <!-- Update package documentation. --> <jdepend outputfile = "${docs}/jdepend-report.txt"> <classpath refid = "compile.classpath" /> <classpath location = "${build}" /> <classespath> <path refid = "class.dirs.path" /> </classespath> <exclude name = "java.*" /> <exclude name = "javax.*" /> </jdepend> Notice there's a number of conversions between filesets, paths and comma separated list just to get the proper 'type' required for the different ant tasks. Is there a way to simplify this while still processing the fewest files in a complex directory structure?

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• Javascript Closures - What are the negatives?

  - by vol7ron

  Question: There seem to be many benefits to Closures, but what are the negatives (memory leakage? obfuscation problems? bandwidth increasage?)? Additionally, is my understanding of Closures correct? Finally, once closures are created, can they be destroyed? I've been reading a little bit about Javascript Closures. I hope someone a little more knowledgeable will guide my assertions, correcting me where wrong. Benefits of Closures: Encapsulate the variables to a local scope, by using an internal function. The anonymity of the function is insignificant. What I've found helpful is to do some basic testing, regarding local/global scope: <script type="text/javascript"> var global_text = ""; var global_count = 0; var global_num1 = 10; var global_num2 = 20; var global_num3 = 30; function outerFunc() { var local_count = local_count || 0; alert("global_num1: " + global_num1); // global_num1: undefined var global_num1 = global_num1 || 0; alert("global_num1: " + global_num1); // global_num1: 0 alert("global_num2: " + global_num2); // global_num2: 20 global_num2 = global_num2 || 0; // (notice) no definition with 'var' alert("global_num2: " + global_num2); // global_num2: 20 global_num2 = 0; alert("local_count: " + local_count); // local_count: 0 function output() { global_num3++; alert("local_count: " + local_count + "\n" + "global_count: " + global_count + "\n" + "global_text: " + global_text ); local_count++; } local_count++; global_count++; return output; } var myFunc = outerFunc(); myFunc(); /* Outputs: ********************** * local_count: 1 * global_count: 1 * global_text: **********************/ global_text = "global"; myFunc(); /* Outputs: ********************** * local_count: 2 * global_count: 1 * global_text: global **********************/ var local_count = 100; myFunc(); /* Outputs: ********************** * local_count: 3 * global_count: 1 * global_text: global **********************/ alert("global_num1: " + global_num1); // global_num1: 10 alert("global_num2: " + global_num2); // global_num2: 0 alert("global_num3: " + global_num3); // global_num3: 33 </script> Interesting things I took out of it: The alerts in outerFunc are only called once, which is when the outerFunc call is assigned to myFunc (myFunc = outerFunc()). This assignment seems to keep the outerFunc open, in what I would like to call a persistent state. Everytime myFunc is called, the return is executed. In this case, the return is the internal function. Something really interesting is the localization that occurs when defining local variables. Notice the difference in the first alert between global_num1 and global_num2, even before the variable is trying to be created, global_num1 is considered undefined because the 'var' was used to signify a local variable to that function. -- This has been talked about before, in the order of operation for the Javascript engine, it's just nice to see this put to work. Globals can still be used, but local variables will override them. Notice before the third myFunc call, a global variable called local_count is created, but it as no effect on the internal function, which has a variable that goes by the same name. Conversely, each function call has the ability to modify global variables, as noticed by global_var3. Post Thoughts: Even though the code is straightforward, it is cluttered by alerts for you guys, so you can plug and play. I know there are other examples of closures, many of which use anonymous functions in combination with looping structures, but I think this is good for a 101-starter course to see the effects. The one thing I'm concerned with is the negative impact closures will have on memory. Because it keeps the function environment open, it is also keeping those variables stored in memory, which may/may not have performance implications, especially regarding DOM traversals and garbage collection. I'm also not sure what kind of role this will play in terms of memory leakage and I'm not sure if the closure can be removed from memory by a simple "delete myFunc;." Hope this helps someone, vol7ron

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