Scheme presentation and more fun with Scala/Swing

June 7, 2009 at 9:50 pm (Scala, Scheme, Week 11) (, , , , )

I gave my lunch & learn presentation on Scheme Friday, and it went pretty well. I found that I had forgotten to correct one of my slide mistakes, but aside from that I felt good about it. I went through the basics of Scheme/Lisp syntax and talked through some examples, and then finished up with the prime factors kata in Scheme. It went almost twice as long as I’d expected, since we stopped several times to discuss and answer questions. I took suggestions on the kata as well, which also slowed things down, but I felt like it was a better way to teach the process of refactoring to an inner recursive function (in place of what would be a loop in an imperative language). Everyone seemed interested and I got some great advice afterwards. The biggest things were that I didn’t always stand up (sometimes camping out in a chair) and that I kind of half-heartedly slapped a name on the presentation (“Scheme for Rubyists”) with only a few references to Ruby (where I could have had comparable Ruby examples for all my Scheme code).

Here are my [corrected] slides, if you want to get the basic gist (unfortunately, the formatting doesn’t translate perfectly to ppt file format – I used OpenOffice): Scheme Presentation

Friday afternoon and this weekend, I got a basic working version of Tic-Tac-Toe using Swing in Scala. I still have plenty to do: just as before, with Java Swing, I was basically spiking to learn the framework, and so there are some GUI tests missing. For now, I’ve put in TODO’s for implementation code I don’t have tests for; tomorrow I’ll start commenting out those pieces of code and driving them test-first. I feel good about my board and player classes; Friday I implemented some in-memory caching to speed up the computer player’s board-scoring computation. I still need to do some thinking about the technical article part of my apprenticeship challenges. I’m leaning towards something on functional programming, perhaps a few refactorings from imperative code to functional.

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State machines and scala.swing

June 4, 2009 at 10:49 pm (Scala, Scheme, Week 11) (, , , , )

After some morning refactoring on my Scala Tic-Tac-Toe (including moving my computer player’s minimax algorithm to a completely functional style) and speed tweaks, I moved on to thinking about how to integrate a GUI. Micah’s told me it’s not a requirement, but I’d like to have another crack at GUI development – I was very slow thinking things through in Java. Micah and I had talked yesterday about the possibility of a state machine to hold the game state so that my other application logic didn’t need to concern itself with whose turn it was. I have mixed feelings about it: on the one hand, state is what I’m trying to avoid in my functional programming study, but on the other, it’s apparently a very widely applicable design pattern that I ought to learn anyway.

At any rate, I spent the morning and most of the afternoon looking into SMC, the state machine compiler. Apparently there are numerous different ones (all named SMC) floating around on the internet. I believe all of them started with Uncle Bob‘s idea, and the one I’m using does give him credit on the website. It’s really like stepping into a second new language (DSL) writing state tables for the state machine compiler. I’m sure that the benefits will outweigh the time I needed to spend reading the documentation.

At the end of the workday, I fooled around with Scala’s Swing library (a wrapper for Java Swing). There are still some Javadocs I needed to dig into to understand what I was doing, but I was able to pick up the syntax pretty quickly. I have to say, Scala really does seem to be Java++. The Java libraries are still super-easy to grab, and the syntax is similar enough that it feels closer than it did with JRuby. The advantages I do see to Java are a familiar syntax and proliferation of tools, especially IDE support for refactoring – Scala’s IntelliJ plugin is good and has a few refactorings, but it has plenty of room for growth.

I spent some time tonight going back over my slides for tomorrow’s Lunch & Learn (“Scheme for Rubyists”), going through the presentation once for my wife and our dogs. I found a couple of outright mistakes and several extra points I needed to make, so it was good practice. I also went through a kata in Scheme that I’ll do tomorrow for the group if we have time. Wish me luck!

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Hacking up a storm: Scala takes to the command line

June 3, 2009 at 10:22 pm (Scala, Scheme, Week 11) (, )

Today was a bit slow going, but I was in a pretty good state of mind, and Scala was feeling a little better. At some point something started to click a little bit on the micro level for functional programming, and I mentioned that I thought functional programming would make testing easier. But when I tried to explain it to Micah, I realized that the problems I had been having with testing in my normal imperative loop were more due to the fact that I hadn’t really thought out what I needed to test in that loop. In fact, my problems were cleared up pretty easily with mocks (hand-rolled — I’m not sure if there’s a mocking library for Scala or not).

Tonight I hacked out the minimax algorithm and have a working (albeit slow) computer player on the console. I got a little stuck a few times, but I remembered that the breakthrough last time (in Java) was to slooooow dowwwwn and make sure I understood precisely for WHOM I was calculating the score for a given board.

I did some Pomodoros when I got home: 25 minutes on, 5 minutes off. I ended up alternating between coding and reading this Programming in Scala book during my “on” sessions, but eventually I got so involved in the minimax problem that I forgot about the timer and just kept going (much to my wife’s chagrin).

I did a few rounds of Scheme code kata as well, in preparation for my Lunch & Learn talk on Friday. I’m realizing as I practice these more that there are a few more topics I need to introduce in the slides portion of the presentation in order to have the kata make sense; probably will get to that tomorrow.

Hooray for progress! Now I have lots of refactoring and GUI code to look forward to.

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Slicing & dicing, and Chicago Code Camp!

May 31, 2009 at 1:55 pm (Ruby, Scheme, Watching, Week 10) (, , , , , , , )

Friday I spent the morning with Eric Meyer working on the same Rails app Jim and I had been working on last week. We got two bugs knocked out pretty quickly, and we also did some planning for a database refactoring (not as big of a deal as it sounds like, as the system isn’t in production yet). Eric’s laptop was having some boot problems, so we used mine; hopefully his Time Machine backup worked over the weekend – there aren’t many things more frustrating than not being able to boot. In the afternoon I chopped up a new website that should launch on Monday, showing Paul some tricks with the Slice tool in Photoshop along the way. I feel like I’m pretty efficient slicing up a PSD into XHTML/CSS – hopefully before too long I’ll feel that way in the code world!

Saturday was Chicago Code Camp, and it was awesome. The first session I went to was “Trends in Continuous Integration and Software Delivery” with Sean Blanton of OpenMake software. He went through the major features of a continuous integration system, and while we’ve got one in place for a couple of websites I work on (cc.rb), there was a lot of information there. I never realized how many different systems were out there. I was impressed with the fact that Sean wasn’t just pimping his products (Mojo and Meister) – it really seemed like a pretty fair assessment of the different systems. There were a couple of slides on Git, actually, which talked about how powerful it was, but that it might be hard for novices to get into. I thought that was odd at first, but as people asked questions I realized that Subversion and other systems have lots of GUI implementations that integrate tightly with OS’es, and Git doesn’t have so many yet. Maybe that’s a good project for someone…

Then I made the tough choice to miss Eric Smith and Eric Meyer’s talk on “TDD for the IPhone,” in order to attend Dean Wampler’s talk on “Better Ruby through Functional Programming.” Sorry, guys! I figured that since I’m working on a presentation involving functional programming, and I mostly use Ruby during work hours, I’d learn a lot there. And I did! I have a much better grasp of what functional programming is now, and how to apply that to Ruby (it can be done without too much hassle, actually). There was one particularly interesting point where Dean posited that we’d see programming (and concurrent programming in particular) become more functional on a small scale, but still object-oriented on a macro level.

Micah’s talk on Limelight (“Develop your Graphical User Interfaces (GUIs) faster than ever, with a thorough suite of unit tests to boot.”) was great, but it was tough because the 8th Lighters were the only Rubyists in the audience (I think), and there were only a few Agile/TDD practitioners. But there was a powerful point about what to do when something is hard to test: rewrite it so that it’s easy to test. And that’s just what Micah did with Limelight – which is indeed easy to test, once you know what you’re doing.

Next, I went to Dean’s other talk, “The Seductions of Scala,” and missed Jim’s “TDD and JavaScript” talk. Sorry, Jim! I had seen a version of Jim’s talk on Friday during the Lunch & Learn, and it was awesome. I’d of course heard about Scala because of the big Rails/Scala/Twitter debacle awhile back, so I was interested in what a language looks like that’s built with concurrency in mind. The language runs on the JVM, so like JRuby, it’s easy to interface with existing Java code. There is some strange-looking syntax to get used to, but it seems interesting, and it sounds like it’s gaining traction on production systems. I had thought the next language I took a look at would be Clojure, since it’s a Lisp dialect with concurrency in mind, and I’ve been studying Scheme, but now I’m thinking I may look into Scala. Or maybe learn JavaScript right. We’ll see. Incidentally, Dean’s new book, Programming Scala is available online in draft form as a preview – it looks great!

Micah’s last talk on “Ruby Kata and Sparring” was great. I’d seen forms of it before: the Langston’s Ant Kata and RubyConf 2008. There’s some kind of magical stuff in this version of the kata (instance_eval), but it’s extremely elegant once you understand the algorithm. I really like the notion of practice as important in software development; Paul was talking about this earlier in the day as well. I’m going to try to do the same kata 3 times a week for a few weeks and see if I see any benefits. I know from trumpet playing that even playing ridiculously easy exercises on a regular basis, with strict attention to form, can yield great benefits.

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Crazy Java/Windows problem and some Scheming

May 12, 2009 at 8:34 pm (Java, Limelight, Ruby, Scheme, Week 8) (, , , , , )

As soon as I came in this morning, Micah asked for my help with a bug he’d been working on tracking down in some Java JNA code in the Limelight source. The gist of the code is that it was calling some native code in Windows DLLs, and about half the time, one of the API hooks didn’t get properly installed. We looked and looked, eventually doing some print statements looking for threading issues and other possibilities. Take a look at the code and see if you can spot the problem:

new Thread()
{
  public void run()
  {
    W32API.HINSTANCE appInstance = Kernel32.INSTANCE.GetModuleHandle(null);
    final User32.HHOOK keystrokeHook = User32.INSTANCE.SetWindowsHookEx(User32.WH_KEYBOARD_LL, new KeyboardHandler(), appInstance, 0);
    hookThreadId = Kernel32.INSTANCE.GetCurrentThreadId();
    MsgLoop();
    User32.INSTANCE.UnhookWindowsHookEx(keystrokeHook);
  }
}

Well, if you knew right away that the new KeyboardHandler() might sometimes get garbage collected before the Windows code gets around to calling it, then you’re lying. Just kidding! I am very impressed if so. Once we looked back on the problem, we could see how the problem might have happened, but it was really bizarre. The idea is that because we don’t hold onto a reference to the new KeyboardHandler() that we create, the garbage collector could think we’re all done with it, even though the Windows code really needs to hold onto it. We didn’t look in depth into how JNA translates the Java code into native Windows code, but Micah understands it, and I think he said it passes a function pointer to the Windows code in this case, so when Windows tries to callback to our Java code residing in that pointer, that code is no longer there. Wacky.

We also made an installer using install4j, which seemed really easy. I’m not sure how much setup Micah had already done, but we were able to drop in some custom icons and a splash screen really easily for our application, and it looks good on both Mac and Windows. I did my first work in Photoshop CS 3, and it was weird not so have the Save Optimized As.. option that I’m used to from Photoshop/ImageReady CS.

I spent some time this afternoon practicing recursion by writing methods to identify palindromes. I did it in Scheme, Ruby, and Java (in that order), all TDD, all in different editors. Of course, Ruby was the easiest and clearest by the end (negative array indexing helped out!), but Scheme wasn’t as hard as I’d expected. Things may be getting easier!

By the way, if anyone else is going through SICP and feeling like you need some more interesting assignments than reading the online book and watching the lectures, check out the sample programming assignments on the website. Even the first one (Exercise 11) might blow your mind if you’re like me and not so used to functional programming.

Here’s a taste:

(define foo6
  (lambda (x)
    (x (lambda (y) (y y))))

Give a Curried application of foo6 that evaluates to 3. Keep in mind this means that at some point you have to evaluate an expression which is a function applied to itself! Yikes. I’ll post my solution later, if anybody’s interested, but I don’t want to give it away too easily. I probably spent a good hour thinking this last one over, and learned to think in a different way in the process.

I need to find a new way of embedding code in this blog. Since it’s hosted on WordPress, I can’t include Javascript embeds of a Gist or Pastie, and I also don’t really have control over the styling. Any suggestions?

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Prime factors and the first client project

May 6, 2009 at 6:34 pm (Flex, Java, Limelight, Ruby, Scheme, Week 7) (, , , , , , )

I worked with Doug almost the whole day today, which was great. This morning when I came in, I happened to mention that last night, I’d done the prime factors kata, inspired by tweets from Doug and Caleb, but I used Scheme: the results are in a Gist. It was pretty frustrating trying to do this in a functional style, purposefully avoiding defining anything other than functions, but I sure learned how poorly I understood Scheme’s list-building constructs (cons, cdr, and car). I have a feeling there are clearer ways to do this, and I’ll definitely try again at some point to make it more fluid (I was completely stumped several times).

So, we spent some time in the morning working through the kata in C++, which was awesome. I hadn’t written any C++ since my only CS course in college, around 10 years ago, and what I wrote then was of course very simple. We used CPPUTest as our unit testing framework, but luckily, Doug already had the tests constructed, so we uncommented one at a time and concentrated on the implementation. I’d like to look into testing C++ a bit more at some point, but it may be awhile, considering all the other things I’m learning. We found several variations on the process of solving this problem, and the process of solving it became clearer, slowly but surely, as we worked through it several times. Then Doug said I should “perform” the kata for Caleb, which I did in Java (and in the process learned how much I rely on my IntelliJ Live Templates when I’m writing JUnit test code!) At some point I may try my hand at screencasting and record myself performing it, but I think I need a little more practice first!

Later on, after I struggled through setting up FlexUnit for the small AIR/Flex I’m building, Doug helped me get my bearings in the client project I’m working on now. We were writing Ruby, HTML, and JavaScript code most of the day, though Objective-C is also part of the project, and Flex/ActionScript may be eventually. It was awesome to be working on a bigger project and finding myself able to figure our what’s going on relatively quickly. My Limelight experience with Tic-Tac-Toe definitely paid off – if I hadn’t spent some time with that, there’s no way I would’ve known what was going on today. Of course, the technology itself wasn’t the sole aim of the Limelight Tic-Tac-Toe project – visual design was a big part of that, too.

At any rate, I’ll obviously have to be a bit more vague about project details now, but I’m excited to be getting into some client work, and I know I’m going to learn a lot from seeing Doug and Micah code on a regular basis.

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