iamkroot / pytapl

Implementations of various systems as described in Types and Programming Languages book, in Python 3.10

PyTAPL

(WIP) Python implementations of various type checkers and interpreters as described in Types and Programming Languages by Benjamin Pierce.

Components

Each subdirectory is a self-contained program, with run.py being the main entrypoint.

1. arith: A simple interpreter with basic numeric expressions to start things off.
2. untyped: Implementation of the untyped lambda calculus, as covered in chapters 5-7.
3. simplebool: Simply-typed calculus supporting Bool and Arrow (function) types and if-then-else statements, from chapters 9-10.
4. rcdsub: Calculus involving Record types and sub-typing relation between types. Supports both Top and Bot types. Covers chapters 15-17.
5. recon: Implementation of Hindley-Milner type inference algorithm on the simply-typed calculus by equality constraint generation, as described in chapter 22.
6. system_f: Includes the typechecker for lambda calculus with parametric polymorphism (SystemF). Supports both universal, and existential types.
7. ... TODO :)

Notes

• Mostly stays close to the original implementation in OCaml
• Makes heavy use of Python 3.10's new match statements for pattern matching
• Parsing is done using Lark. Not focusing on efficiency of the parser