Abstract
We present a simple type system inspired by that of Common Lisp. The type system is intended to be embedded into a host language and accepts certain fundamental types from that language as axiomatically given. The type calculus provided in the type system is capable of expressing union, intersection, and complement types, as well as membership, subtype, disjoint, and habitation (non-emptiness) checks. We present a theoretical foundation and two sample implementations, one in Clojure and one in Scala.