I work in combinatorics and algorithms. The motivating area is container data types and this has led to many results on Restricted Permutations. I manage the Otago University Theory of Computing Research Group. I retired at the end of December 2012 and continue my association with Otago as Professor Emeritus.
My previous research areas include varieties of groups, permutation groups, algebraic complexity, linear algebra, ordered sets, additive number theory, random generation of trees, and descent algebras; I occasionally dabble.