Lambda the Ultimate

An Operational Foundation for Delimited Continuations in the CPS Hierarchy

We present an abstract machine and a reduction semantics for the lambda-calculus extended with control operators that give access to delimited continuations in the CPS hierarchy. The abstract machine is derived from an evaluator in continuation-passing style (CPS); the reduction semantics (i.e., a small-step operational semantics with an explicit representation of evaluation contexts) is constructed from the abstract machine; and the control operators are the shift and reset family. We also present new applications of delimited continuations in the CPS hierarchy: finding list prefixes and normalization by evaluation for a hierarchical language of units and products.

...or in other words - a view on the delimited continuations from another side (as compared to "A Monadic Framework for Subcontinuations" or Oleg's posts on Hakell list). I find it useful to learn about the same concept from different sources - and the delimited continuations are still promising to become an important concept.

Also, I suspect that defunctionalized approach might be more straightforward for people coming from imperative languages.

I thought some of you might be able to enjoy themselves playing around with this in the coming vacation. It's a basic interpreter written in javascript, and thus runs in the browser.

There is also a ruby interpreter written for the browser, which can be found here

Well .. that's all folks,
Merry christmas and a happy new year to all of you