Interpreting types as abstract values [The Abstract of the lecture notes] We expound a view of type checking as evaluation with `abstract values'. Whereas dynamic semantics, evaluation, deals with (dynamic) values like 0, 1, etc., static semantics, type checking, deals with approximations like int. A type system is sound if it correctly approximates the dynamic behavior and predicts its outcome: if the static semantics predicts that a term has the type int, the dynamic evaluation of the term, if it terminates, will yield an integer. As object language, we use simply-typed and let-polymorphic lambda calculi with integers and integer operations as constants. We use Haskell as a metalanguage in which to write evaluators, type checkers, type reconstructors and inferencers for the object language.
Staapl is a collection of abstractions for metaprogramming microcontrollers from within PLT Scheme. The core of the system is a programmable code generator structured around a functional concatenative macro language adapted to a 2-stack machine model. On top of this it includes a syntax frontend for creating Forth style languages, a backend code generator for the Microchip PIC18 microcontroller architecture, and interaction tools for shortening the edit-compile-run cycle. It is structured as a code library to facilitate integration into larger systems employing a model-based design approach. The primary, practical goal is to provide a tool chain for programming low-end (8-bit) microcontrollers in a Forth-style language extended with powerful metaprogramming facilities. The secondary goal is to generalize and modularize this approach and extend it in two directions: to provide a standard machine model as an abstraction point for a large class of small embedded processo