The Datalog support is a very interesting feature for such a fully-featured language. From the home page:
def reachable(g: List[(String, Int32, String)], minSpeed: Int32): List[(String, String)] =
let facts = project g into Road;
let rules = #{
Path(x, y) :- Road(x, maxSpeed, y), if maxSpeed >= minSpeed.
Path(x, z) :- Path(x, y), Road(y, maxSpeed, z), if maxSpeed >= minSpeed.
};
query facts, rules select (src, dst) from Path(src, dst) |> Foldable.toList
Composing datalog natively like any other type – very cool.
