Ergo is a little engine of proof dedicated to program verification. It fully supports quantifiers and directly handles polymorphic sorts. Its core component is CC(X), a new combination scheme for the theory of uninterpreted symbols parameterized by a built-in theory X. In order to make a sound integration in a proof assistant possible, Ergo is capable of generating proof traces for CC(X). Alternatively, Ergo can also be called interactively as a simple oracle without further verification. It is currently used to prove correctness of C and Java programs as part of the Why platform. 1.

Abstract. Based on Danvy et al.’s functional correspondence, we give a further example of gradual refinement of an interpreter into a known, lowlevel abstract machine underlying real-world compilers, by deriving an abstract model of the Warren Abstract Machine from a simple resolutionbased Prolog interpreter. We show that other well-known functional programming techniques (namely, explicit laziness and semi-persistent data structures) can help to develop abstract machines without detailed examination of the semantics realised by the interpreter.