Abstract

Adding a static type system to a dynamically-typed language can be an invasive change that requires coordinated modification of existing programs, virtual machines and development tools. Optional pluggable type systems do not affect runtime semantics of programs, allowing them to be safely added to a language without affecting existing code and tools, and while supporting both dynamic and static typing. However, in programs mixing dynamic and static types, they do not allow reporting runtime type errors precisely. We present optional runtime monitoring of type errors for tracking these errors without affecting program semantics. Our Python-like target language Alore has a nominal optional type system with bindable interfaces that can be bound to existing classes by clients to help the safe evolution of programs and scripts to static typing.

This is work in progress. Practice talk for STOP 2011 .