Effects and effect inference for a core Java calculus

Abstract An effects system can be used to delimit the scope of computational effects within a program. This information is not only useful for the programmer, but also can be used in the definition of a number of optimizations. Most effects systems have been defined for functional languages with simple state. Greenhouse and Boyland have recently suggested how an effects system could be used within Java. In this paper we take a core imperative calculus for Java, and consider its extension with an effects system, following the suggestions of Greenhouse and Boyland. We define formally the effects system and an instrumented operational semantics and prove the correctness of the effects system; a question left open by Greenhouse and Boyland. We also consider the question of effect inference for our calculus, detailing an algorithm for inferring effects information and prove it correct.