Datafun is a new language I'm working on with Neel Krishnaswami. 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.
Here's some further resources on Datafun:
A mini-version of Datafun implemented in ~60 lines of Racket, with plenty of commented examples. Intended as a helpful introduction for folks who know Racket or Scheme. It includes set comprehensions and fixed points, but doesn't handle monotonicity, semilattices, or termination checking.