A Formally Specified Type System and Operational Semantics for Higher-Order Procedural Variables

Abstract

We formally specified the type system and operational semantics of LOOPw with Ott and Isabelle/HOL proof assistant. Moreover, both the type system and the semantics of LOOPw have been tested using Isabelle/HOL program extraction facility for inductively defined relations. In particular, the program that computes the Ackermann function type checks and behaves as expected. The main difference (apart from the choice of an Ada-like concrete syntax) with LOOPw comes from the treatment of parameter passing. Indeed, since Ott does not currently fully support alpha-conversion, we rephrased the operational semantics with explicit aliasing in order to implement the out parameter passing mode.