Mobile Lua – iOS and Android apps with Corona

On Thursday (May 26, 2011), I presented at the St. Louis Mobile Dev group, on cross-mobile-platform development with Lua. There are various ways to do this (including rolling your own), but for simplicity I used Ansca’s Corona product. The talk was somewhat impromptu, so I didn’t record audio or video. The slides are available as a PDF: 2011-Lua-Corona-Mobile-Dev.pdf

From this blog, you might get the impression that I use Lua extensively. That is not true; 95% of my work does not involve Lua in any way.

Upcoming Talk: Lua on iPhone and Android (using Corona)

This Thursday (May 26, 2011), I will give a talk at the St. Louis Mobile Dev group on cross-mobile-platform development with Lua. There are various ways to do this (including rolling your own), but for simplicity I’m using Ansca’s Corona product.

As usual, I’ll zoom through some slides, and concentrate instead on the code. For some background on Lua, you may want to watch the video of my 20-minute Lua talk from last year’s Strange Loop.

Update: slides are available here.


October 2010: Business of Software, Strange Loop, Clojure Conj

I attended three conferences in October 2010, the most of any month of my life to date. Others have posted extensively about all three events, so I’ll link to a few posts and point out highlights for me.

Business of Software 2010

BoS alternates between San Franscisco and Boston; this year it was in Boston. There are plenty of excellent summaries online (here, here, here, here), and an especially nice set of photos here.

The conference was packed full of great speakers, mostly well known. I am sure the most “expensive” person in the lineup was Seth Godin; he is an excellent speaker and had interesting content, but wasn’t as relevant to me as some of the others.

The high point of BoS was Joel Spolsky’s closing talk. Unlike everyone else, he used no slides, and simply sat at a table to tell us the story of his last year or so. I was a bit surprised at his public airing of partner grievances, but that was probably necessary to tell the (very worthwhile) story of his transition over the last year from the “small, profitable company” model to the “go big” model. The former can make good money; but only the latter can make a broad impact to build a (perhaps slightly) better world.

I also especially enjoyed Erik Sink and Derek Sivers telling the stories of their company sales. My own company sale experience was more like Erik Sink’s.

In the past, Business of Software has posted the videos for year N during the marketing runup for year N+1; I suspect the same will happen this time. When those videos appear, watch them. Especially keep an eye out for Joel’s criticism of Craigslist, with which I agree.

Strange Loop 2010

Strange Loop is held in, and named after, the Delmar Loop area which spans University City and a bit of St. Louis. The 2010 event was much larger than the 2009 event; I don’t know whether it will be possile to accomodate 2011’s crowd in the Loop area or not; I’ll certainly attend either way.

Again there are plenty of summaries online, including here and here.

The highlight of this event for me was Guy Steele’s talk on parallelism. Unlike some commenters, I greatly enjoyed both the first half of the talk (a stroll through some ancient IBM assembly code) and the second half (including the Fortress example code). I’ve been inspired by this talk and criticism about it to put together my own upcoming code-centric talks, in which I’ll touch on the key parallelism ideas briefly, then step through several code examples in various languages.

I also spoke at Strange Loop, in a 20 minute slot, on Lua (video). Most of the feedback on my talk was positive, particularly of the “why, not how” approach I used to make the best use of 20 minutes. A few people would have preferred a longer talk with more “how”; I might put together such a presentation at a later date.

Disclosure: Oasis Digital sponsored Strange Loop.

(first clojure-conj)

At Clojure Conj I had the strong impression of being at the start of something big. I believe that Clojure, in spite of the needlessly-feared parentheses, has more “legs” than any other of the current crop of ascendant languages: getting state right (and thus making it possible to get parallelism right) is more important than syntax. Based on the folks I met at the Conj, I’d say Clojure has exactly the right early adopters on board.

As usual plenty of others have posted detailed notes (here, here, here, here, here).

The talk that stands out most to me was not exactly about Clojure. Rich Hickey’s keynote was about the importance and process of thinking deeply about problems to create a solution. In a sense this is the counterpoint to agile, rapid-iteration development, suitable to a different class of problems. Clojure exudes a sense of having been thought about in depth, and Rich is obviously the #1 deep thinker. When this arrives on video, watch it. Twice.

I also enjoyed Rich’s impromptu Go clinic at the pre-conference speaker (and sponsor) dinner. Note that Go has totally different rules from the similarly named Go-Moku, and is not to be confused with Google’s Go language.

Disclosure: Oasis Digital sponsored Clojure Conj.

Back to Work

I’ve had very little time for my own projects this month; between the events, most of my available hours were occupied with Oasis Digital customers. My mind is bursting with worthwhile ideas to pursue.

Lua Doesn’t Suck – Strange Loop 2010 video

At Strange Loop 2010, I gave a 20 minute talk on Lua. The talk briefly covered six reasons (why, not how) to choose Lua for embedded scripting. Lua is safe, fast, simple, easily learned, and more popular that you might expect.

The Strange Loop crew only recorded video in the two largest venues (out of six), so I made a “bootleg” video of my talk, for your viewing pleasure:


The video/audio sync starts out OK, but drifts off by a second or so by the end. The drift is minor, so it is reasonably viewable all the way through. If you don’t have Flash installed (and thus don’t see the video above), you can download the video (x264); it plays well on most platforms (including an iPad).

The slides are available for PDF download.

Video Hackery

This video recording was an experiment: instead of hiring a video crew (with professional equipment), or using my DV camcorder, I instead used the video recording capability of my family’s consumer-grade Canon digicam. This device has three advantages over my DV camcorder:

  1. No tape machinery; no motors; thus no motor noise in the audio.
  2. Smaller size, easier to carry in and out.
  3. Directly produces a video file, easily copied off its SD card.

As you can see from the results, the video quality is adequate but not great. Still, I learned that if I want to increase the quality of recording, the first step is not to use a better camera or lens! Rather, it is to bring (or persuade the venue to provide) better light. For good video results, the key is light the speaker well, without shining any extra light on the projector screen. With that in place, a better camera make sense.

The audio was a different story. Like nearly all consumer video cameras (and digicams with video), mine doesn’t have an external audio input, so the audio (from ~12 feet away) was awful. As a backup I had used a $75 audio recorder and a $30 lapel microphone, and that audio is very good, certainly worth using instead of the video recording audio track.

To combine the video in file A with the audio in file B, I used the ffmpeg invocation below. I reached the time adjustments below in just a few iterations of trial and error, by watching the drafts in VLC, using “f” and “g” to experiment with the audio/video time sync. I also trimmed off a bit of the bottom of the video, and used “mp4creator.exe -optimize”, which I had handy on a Windows machine, to prepare the file for progressive download viewing.

ffmpeg -y -ss 34.0 -i WS_10001.WMA -ss 34.0 -itsoffset -12.05 -i MVI_4285.AVI -shortest -t 8000 -vcodec libx264 -vpre normal -cropbottom 120 -b 400k -threads 2 -async 200 Cordes-2010-StrangeLoop-Lua.m4v

The remaining bits of technology are FlowPlayer, a WordPress FlowPlayer plugin, and a CDN.

Next Big Language = JavaScript

There’s a lot of buzz about Steve Yegge’s “port” of Rails to JavaScript, and Steve has now provided (in his funny, self-deprecating style) the background of how it came to be. He doesn’t quite say it explicitly in this post, but I think it reveals that the “Next Big Language” he has been hinting at is JavaScript.

I (mostly) agree:

JavaScript is in nearly every browser, including tiny ones (like the one in my BlackBerry Pearl). It may be the single most widely available language today.

Because of the above, an enormous population of JavaScript programmers (though sometimes of dubious skill) has emerged.

Starting with Java 6 it’s “in the box” there also. To me, this makes it the likely winner, by a wide margin, for a dynamic language to be used at Java shops or inside Java projects. Being “in the box” is a powerful advantage, one which the many other contenders will have a hard time overcoming.

Adobe’s new JavaScript virtual machine implementation, which they handed over to Mozilla as “Tamarin”, sounds like it will boost JavaScript performance great, making it good enough for a very wide variety of projects.

JavasScript uses curly braces, like the last few Big Languages.

Like Java, C, C++, etc., JavaScript has specs and multiple competing, complete, current, high quality implementations. This, to me, is a big advantage over Ruby, Python, and other currently popular dynamic languages. Of course there is plenty of room in the industry for these language to thrive also, I am not saying any of them will go away; we use Python with great results and expect to keep doing so.
Mark Volkmann initially thought I was nuts to predict JavaScript as a winner but came around a few month later (and said so in a user group talk).

In a project at work, we’d adopted JavaScript as our plugin extension language for user-customizable rules (billing rules, etc.). I’d have chosen Lua (as I did for another project), but there are at least 1000x as many JavaScript programs out there. So far it has worked very well. If we had it to do over we might implement far more of the project in JavaScript.

However, there are a few reasons why I only “mostly” agree:

First, with JavaScript there isn’t a good way to avoid shipping source code. Sure, you an obfuscate JavaScript with various tools, but the results remains far for amenable to readable-source recovery than in a more traditionally compiled language. For open source projects this is no big deal, but there are also many worthwhile businesses and projects which depend on proprietary, not open software (including most of our projects), and it’s not year clear that obfuscation is sufficient protection. (Update in reply to a comment below: This matters even for server-side software, because some of us create and sell software products for other people to run on their servers.)

Second, at the moment JavaScript appears to lack a module system, without which it’s painful to build large systems. I expect an upcoming language version will address this.

Java Scripting Talk – Code, Notes, and Audio

Last night (9 Nov 2006) at the St. Louis Java User Group, I gave a talk on “Scripting Your Java Application”. As I mentioned, there were no slides, but rather a handout, the text of which is pasted below. You can download the handout (a tight, one page PDF), the code, audio of the talk (WMA), and audio of the talk (MP3, larger). The audio was recorded with my Olympus WS100 Digital Voice Recorder, so the quality is bearable but not great.

Update: As an experiment, I also had CastingWords prepare a transcript of the talk. It’s somewhat tedious to read (I didn’t edit it at all), but it is available as Google fodder rather than trapped only in audio.
Continue reading “Java Scripting Talk – Code, Notes, and Audio”