Applying Types as Abstract Interpretation to a Language with Dynamic Dispatch Johannes Emerich Abstract: We are concerned with an application of the "types as Abstract Interpretation" perspective of [Cousot 97] to the problem of typing overloaded operator symbols in a simple applicative language with dynamic dispatch. We begin by a development of abstract semantics, or type systems, for \lambda_C, a language without overloading. The distinction between parametric and ad-hoc type polymorphism is then introduced, where a particular challenge arising from the ad-hoc variant is stressed. \lambda_K, an extension of \lambda_C with support for overloading definitions at the user level serves to illustrate the problem of ad-hoc polymorphism, and is presented together with a type system designed to support some of its forms. To prove soundness of said type system, the abstract interpretation development of type systems for \lambda_C is extended to \lambda_K and the new type system is shown to be a sound abstraction in the sense of [Cousot 97].