Rod Bustall: In Memoriam

This is an obituary of Rod Burstall, written in his honour. Rod was a prominent computer scientist whose contributions span over forty years. Most of his career was spent at Edinburgh University. He lead the team programming Freddy, the first hand-eye assembly robot, with much of his effort being devoted to the development of the POP-2 programming language. He became interested in a mathematical approach to software development: he recognised the central role of structural induction; his work on reasoning about mutable data structures was an influential precursor of separation logic; he was the first to point out the connection between program proof and modal logic; and he was responsible for the idea that stores are mappings from locations to their contents. As part of his quest for correctness of programs, Rod, with John Darlington, undertook the first major work on program transformation. His interest in novel programming languages continued with the experimental language HOPE, developed with Don Sannella and David MacQueen. Robin Milner's Standard ML and its relatives integrated ideas from Hope, and Rod was an active member of the Standard ML design team. Rod pioneered the use of algebraic and categorical techniques in programming. He and Joseph Goguen proposed the first algebraic specification language. Rod was an early user of categorical ideas, in particular developing computational category theory with David Rydeheard. The interplay between programming and correctness proofs is again evident in Rod's contributions to automated proof support systems. For example, he led Randy Pollack, Zhaohui Luo, and others in the Lego proof assistant, which implemented type systems supporting interactive proof development. Finally, Rod, with James McKinna, investigated notions of programs packaged with proofs of their correctness, anticipating the topic of proof-carrying code.