Grail: a functional form for imperative mobile code

In Robert Louis Stevenson’s novel [31], Dr Jekyll is a well-regarded member of polite society, while his alter ego Mr Hyde shares the same physical form but roams abroad communing with the lowest elements. In this paper we present Grail, a well-behaved first-order functional language that is the target for an ML-like compiler; while also being a wholly imperative language of assignments that travels and executes as Java classfiles. We use this dual identity in the Mobile Resource Guarantees project, where Grail serves as proof-carrying code to provide assurances of time and space performance, thereby supporting secure and reliable global computing.