Lang.NET 2009

Back in September, I attended the JVM Language Summit. This week I’ve been doing the Bainbridge Island to Redmond ferry commute in order to attend the Lang.NET symposium. Here’s some of the stuff that stood out to me.

Hopscotch

Gilad Bracha talked about Hopscotch, the IDE for Newspeak. Newspeak is one of those things that’s on my very long list of things to look at. For a Smalltalk or Lisp developer, much of the talk was familiar — an illustration of the power of writing the IDE for a dynamic language in a dynamic language. In fact Bracha asserted that the true power of Smalltalk is the dynamism in the IDE itself. I think that’s probably true today, since almost all popular IDE’s are written in a static language. The other interesting feature of Hopscotch is the pervasive use of a web browser style UI in the IDE. This looks promising, and gives me hope that a web browser based IDE might be feasible.

Newspeak is implemented atop the Squeak VM, and when questioned about this choice, Bracha said that it would be much harder to implement Newspeak on either the CLR or JVM (and he’d be a position to know about the JVM in particular). He was hopeful that John Rose’s work on dynamic extensions for the JVM would take out some (but not all) of the pain.

Powershell

At the JVM Language Summit, Rich Hickey gave a 15 minute talk that left me wishing he had been given 30 minutes. Jeffrey Snover’s 15 minute talk on Powershell left me feeling the same way. Powershell may not be a monad toting concurrency friendly uber functional language on the CLR, but it was compelling to me because of it’s sheer practicality and usefulness. I’ve been following Powershell via blog posts since it was announced, but seeing it demoed by its designer is another thing altogether. The Powershell folks have done some nice work to present shell users with a very consistent user interface. A side effect of this work makes it easy to make GUI’s that can output Powershell commands, and apparently in future versions of Windows, the GUI admin tools will do this. In addition to rationalizing the user visible behavior of the shell, Powershell is able to do some very impressive stuff in terms of remote execution, limited/secure execution, single machine transactions, and more.

I spent some time talking with Snover later in the day, and he seemed to think that UNIX shells could gain a fair amount of PowerShell’s capabilities by recognizing that pipes ship bytestreams, adopting a data format (like JSON or XML) for those byte streams, and proceeding from there. That might be true technically, but that would be a huge cultural change for that community.   

Lars Bak on V8

Lars Bak talked about his work on V8. V8 is the nth VM that Bak has worked on, and my main takeaway from his talk was that the V8 team has tried to do a lot of careful measurement of real (and anticipated future) Javascript programs. They’ve then turned around and used those measurements to guide them in selecting from the techniques developed for Self, StrongTalk, and Hotspot. None of those techniques would be a mystery to people familiar with the literature. But the insight into this all applies to Javascript was pretty interesting.

Since this is all about performance, it’s interesting to note that V8 has just about doubled its performance during its one year life. Bak predicted that by 3-4 years in perrformance will have quadupled. There was a funny moment where someone asked about comparison’s with Firefox’s TraceMonkey tracing JIT. Bak’s reply was “let’s run the (Google V8) benchmarks“, which he then proceeded to do (V8 won). Bak is clearly competitive about this, which can only mean good things for Javascript users.

F#

F# is something that’s been at the edge of my radar because of asynchronous workflows. Lang.NET was a chance for me to get a quick education on what that’s all about. It turns out that async workflows are an application of computation expressions, which are a way of doing monadically inspired language extension. Async workflows end up being a way of using CPS style tasking but with a nice syntax. Most of this became clear during Tomas Petricek’s talk on Reactive pattern matching for F#. The code that Petricek showed was very evocative of actor style code and the use of F# pattern matching was evocative of Erlang’s use of the same. One interesting point was the use of join patterns, something that doesn’t have a direct analog in either Erlang or typical actor implementations.

Amanda Laucher‘s talk Concurrency for F# was a discussion of a client engagement that she did using F# and the concurrency features of the language. The application in question was an insurance application, and the speedup numbers looked pretty interesting. This is notable because most of the concurrency examples that you can find are outside the domain of “business programming”. Having this kind of data is really useful for people interested in the concurrency space. Amanda’s work was done as a Microsoft case study, and published version will be available at some point.

Erik Meijer

Erik pretty much gets his own section because he’s that entertaining/interesting. This time he was talking about the Livelabs Reactive Framework, where he described a way to use LINQ for distributed computations, using the specific example of an AJAX dictionary based suggestion function. Erik started by using (throwing) coins to illustrate the IEnumerable and IObservable interfaces. He then used mindless symbol pushing to demonstrate that these two interfaces were duals of each other, and that they obeyed the rules for monads. That being true, he then showed how you could define observable collections which could be used with LINQ.

Tidbits

Herman Venter talked about a Common Compiler Infrastructure for the CLR. There’s some nice stuff in here if you are implementing a language on the CLR. One user of this infrastructure is the Code Canvas, a “spatial development environment”. It’s good to see that people are stretching the notion of what a development environment should be. The thing that stuck out to me most from this talk was not the technology (which is good), but Venter’s call to action at the end. The CCI is being open sourced, and Venter’s call for participation and contribution was indistinguishable from the same end of talk call at any open source conference. A sign of changes underway.

Joshua Goodman did a product rundown on What’s new in CLR V4 for Languages. There’s several years worth of changes to the CLR queued up for V4, which will be a big update. Most interesting to me was the inclusion of a Hill Climbing algorithm for allocating / managing threads. This strikes me as a kind of policy decision, something which you might want to plug into the CLR as opposed to having it installed under the hood. It will be interesting to see how this ends up working out in production settings.

Deja Vu

In a previous life, I did some work on database programming languages, and I experienced deja vu twice during the conference. The first was during Philip Wadler’s Links: Web programming without tiers. The goal of Links is enable front end and back end web programming using a single language. Wadler didn’t discuss the front end part during his talk. He focused on the back end, particularly on the ability to translate programming language code into SQL, in a fashion slightly beyond LINQ. This is done using a combination of the monadic techniques used for LINQ, as well as a type/effect system which is used to help determine whether a piece of code is SQLizable or not. The work was eerily familiar, and when Wadler quoted Limsoon Wong and Leonid Libkin’s work on Kleisi, I knew why. We looked at their work on structural recursion (and comprehension notation) for our work on list and tree queries.

The last talk(s) of Lang.NET was a double header talk on Oslo/M by Paul Vick and David Langworthy. David and I were officemates while we were graduate students at Brown. Even more deja vu was induced when I saw David demoing how the M toolchain could generate SQL schemas and queries. As he put it to me afterwards – “this is all that stuff we were talking about 10 years ago”. Well, closer to 20 now, but who’s counting. M is in its very early days – I think it will be more interesting when it can generate CLR code to match the SQL.

Last bits

Thanks to Harry Pierson for making sure that I got an invitation to Lang.Net. People were very welcoming, even though I had to ask questions about various bits of Microsoft alphabet soup. I suspect that this is the only conference I will go to all year where Macs are the minority. It’s probably good for me to get out of the bubble every once in a while…   

Overall, I found the topics to be a little more broad ranging than the JVM Summit. There were quite a few talks on tools, while there were comparatively fewer at the JVM summit, and those tools discussed at the JVM summit were really aimed at language implementors. One thing that worked well with the JVM Summit was allowing for some open space sessions so that attendees could get together and discuss topics of mutual interest, often based on what had been presented during the sessions. I think that some similar time slots would have enhanced the experience.

I definitely came away impressed by some of the work going on in the CLR ecosystem, and I hope that the exchange between the JVM and CLR communities will continue and expand.

Update: Videos of the talks are now available.

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