Abstract

Regular tree expressions are a natural formalism for describing the sets of tree-structured values that commonly arise in programs; thus, they are well-suited to applications in program analysis. We describe an implementation of regular tree expressions and our experience with that implementation in the context of the FL type system. A combination of algorithms, optimizations, and fast heuristics for computationally difficult problems yields an implementation efficient enough for practical use. 1 Introduction Regular tree expressions are a natural formalism for describing the sets of tree-structured values that commonly arise in programs. As such, several researchers have proposed using (variations on) regular tree expressions in type inference and program analysis algorithms [JM79, Mis84, MR85, HJ90, HJ91, AM91]. We are not aware of any implementations based on regular tree expressions, however, except for our own work on type analysis for the functional language FL [B + 89]. A p...

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