Lambda the Ultimate

Luke Palmer and Nick Szabo can shoot me for this if they want, but I think this is warranted, and I want to connect a couple of dots as well. Luke is one of a number of computer scientists, with Conal Elliott probably being the best known, who have devoted quite a bit of attention to Functional Reactive Programming, or FRP. FRP has been discussed on LtU off and on over the years, but, unusually for LtU IMHO, does not seem to have gotten the traction that some other similarly abstruse subjects have.

In parallel, LtU has had a couple of interesting threads about Second Life's economy, smart contracts, usage control, denial of service, technical vs. legal remedies, and the like. I would particularly like to call attention to this post by Nick Szabo, in which he discusses a contract language that he designed:

Designing the contract language radically changed my idea of what program flow and instruction pointers can be. Its successor, a general-purpose programming language, may thereby make event-oriented programming and concurrency far easier. The language is targeted at GUI programming as well as smart contracts, real-time, and workflow programming. My answer to the problems of concurrency and event handling is to make the ordering of instructions the syntactic and semantic core of the language. The order of execution and event handlers are the easiest things to express in the language rather than kludged add-ons to a procedural or functional language.

In recent private correspondence, Nick commented that he'd determined that he was reinventing synchronous programming à la Esterel, and mentioned "Reactive" programming.

Ding!

To make a potentially long entry somewhat shorter, Luke is working on a new language, Dana, which appears to have grown out of some frustration with existing FRP systems, including Conal Elliot's Reactive, currently perhaps the lynchpin of FRP research. Luke's motivating kickoff post for the Dana project can be found here, and there are several follow-up posts, including links to experimental source code repositories. Of particularly motivating interest, IMHO, is this post, where Luke discusses FRP's interaction with garbage collection succinctly but nevertheless in some depth. Luke's most recent post makes the connection from Dana, which Luke has determined needs to have a dependently-typed core, to Illative Combinatory Logic, explicit, and offers a ~100 line type checker for the core.

I find this very exciting, as I believe strongly in the project of being able to express computation centered on time, in the sense of Nick's contract language, in easy and safe ways extremely compelling. I've intuited for some time now that FRP represents a real breakthrough in moving us past the Von Neumann runtime paradigm in fundamental ways, and between Conal Elliott's and Luke's work (and no doubt that of others), it seems to me that my sense of this may be borne out, with Nick's contract language, or something like it, as an initial application realm.

So I wanted to call attention to Luke's work, and by extension recapitulate Conal's and Nick's, both for the PLT aspects that Luke's clearly represents, but also as a challenge to the community to assist in the realization of Nick's design efforts, if at all possible.