Moony Parser 2.3 is out

A new version of Moony Parser is out (namely 2.3). It is a javascript library that implements "Earley" algorithm which makes it CFG complete. It provides a custom cool structurized grammar definition language that is more readable and more compact than BNF or PEG languages.

U can try it online on web page: Moony Parser

It features cool HTML based grammar testing environment.

A Theory of Changes for Higher-Order Languages: Incrementalizing Lambda by Static Differentiation

A PLDI 2014 paper by Yufei Cai et al; abstract:

If the result of an expensive computation is invalidated by a small change to the input, the old result should be updated incrementally instead of reexecuting the whole computation. We incrementalize programs through their derivative. A derivative maps changes in the program’s input directly to changes in the program’s output, without re-executing the original program. We present a program transformation taking programs to their derivatives, which is fully static and automatic, supports first-class functions, and produces derivatives amenable to standard optimization.

We prove the program transformation correct in Agda for a family of simply-typed -calculi, parameterized by base types and primitives. A precise interface specifies what is required to incrementalize the chosen primitives. We investigate performance by a case study: We implement in Scala the program transformation, a plugin and improve performance of a nontrivial program by orders of magnitude.

I'm skeptical of the differential approach, which to me seems wouldn't scale in general. But its a very interesting read regardless.