ML Module Mania: A Type-Safe, Separately Compiled, Extensible Interpreter

Abstract

The new embedded interpreter Lua-ML combines extensibility and separate compilation without compromising type safety. The interpreter’s types are extended by applying a sum constructor to built-in types and to extensions, then tying a recursive knot using a two-level type; the sum constructor is written using an ML functor. The interpreter’s initial basis is extended by composing initialization functions from individual extensions, also using ML functors. Lua-ML adds a detailed example to the debate over how much power is needed in a modules language.