Parameterized Modules for Classes and Extensible Functions

We present F(EML), a language that combines classes, extensible functions, symmetric multiple dispatching, and a practical system for parameterized modules. Parameterized modules permit subclasses and function extensions to be defined and typechecked once, and then reused to extend multiple argument modules. F(EML)'s predecessor, EML, supported classes and extensible functions with multiple dispatch, but its support for parameterized modules was weak. F(EML)'s key novel features are alias declarations, generalized type relations in module signatures, and a nontrivial definition of signature subsumption.