We are happy to announce that our paper entitled Type-Checking of Heterogeneous Sequences in Common Lisp authored by Jim Newton, Akim Demaille, and Didier Verna has been accepted for presentation and publication at the 9th European Lisp Symposium (http://www.european-lisp-symposium.org). Abstract: We introduce the abstract concept of rational type expression and show its relationship to rational language theory. We further present a concrete syntax, regular type expression, and a Common Lisp implementation thereof which allows the programmer to declaratively express the types of heterogeneous sequences in a way which is natural in the Common Lisp language. The implementation uses techniques well known and well founded in rational language theory, in particular the use of the Brzozowski derivative and deterministic automata to arrive at a solution which can match a sequence in linear time. We illustrate the concept with several motivating examples, and finally explain many details of its implementation. Please find the link to the article and a longer more elaborate project report here: https://www.lrde.epita.fr/wiki/Publications/newton.16.els.inc If you have any questions or comments about the paper, we are happy to discuss them with you. Jim