Brachylog is a declarative logic programming language much like Prolog. Brachylog is designed to be much terser than Prolog, while retaining some readability.
Brachylog was developped for code golf: solving programming challenges with the smallest possible programs. Brachylog is, as far as I know, the only programming language where constraint logic programming is the default for all integer arithmetic operations.
As a showcase, here is a 34-character Brachylog program that solves sudokus:
{0∧9≥ℕ₁|}ᵐ².≠ᵐ\≠ᵐḍ₃ḍ₃ᵐ²zᵐcᵐ²c≠ᵐ∧.≜
Learn more about Brachylog on Github.