Implicit Parameters: Dynamic Scoping with Static Types

Abstract

This paper introduces a language feature, called implicit parameters, that provides dynamically scoped variables within a statically-typed Hindley-Milner framework. Implicit parameters are lexically distinct from regular identifiers, and are bound by a special with construct whose scope is dynamic, rather than static as with let. Implicit parameters are treated by the type system as parameters that are not explicitly declared, but are inferred from their use.