A Decision Procedure for Regular Expression Equivalence in Type Theory

Paper in proceeding, 2011

We describe and formally verify a procedure to decide regular expressions equivalence: two regular expressions are equivalent if and only if they recognize the same language. Our approach to this problem is inspired by Brzozowski’s algorithm using derivatives of regular expressions, with a new definition of finite sets. In this paper, we detail a complete formalization of Brzozowki’s derivatives, a new definition of finite sets along with its basic meta-theory, and a decidable equivalence procedure correctly proved using Coq and Ssreflect.