datafun is an open source programming language created in 2015 by Michael Arntzenius.
git clone https://github.com/rntz/datafun
|#1432on PLDB||8Years Old|
It's a simple, pure, and total functional language that generalizes Datalog. Datafun's superpower is that it can concisely and declaratively express and compute fixed points of monotone maps on semilattices.