px-lang

px aims to be a starting point for domain specific, typed lambda calculi. It is inspired by David Himmelstrup's fvg, Sean Lee's hylogen and Stephen Diehl's amazing "Write You a Haskell" series. It uses an interesting cofree approach to type inference inspired by Brian McKenna and is largely based on the papers "Generalizing Hindley-Milner type Inference Algorithms" by Heeren, Hage and Swierstra

I aim to make the language extensible with domain specific parsers, primitives and code generators. The goal is to make px be the main ingredient in a bunch of little functional languages.

notes

This project started as a way for me to learn about TAPL and to address my gripes with shader languages. It's been sitting on my hardrive untouched for over a year now and I figured I should get it out in public before it gets lost. It is not in a usable state, though it may compile and it may pass tests. The goals are lofty and unatainable with my current availability for OSS. It could be a fun study though!

target examples

These aren't functional yet, but there an example of what I'd like the language to look like in different domains (it's basically Haskell).

Coloring a canvas in WASM:

munchingSquares :: Vector Word4
munchingSquares = do
  x <- range 0 255
  y <- range 0 255
  return $ xor x y


main :: WASM ()
main = do
  -- Make the canvas and set the pixels
  c <- newCanvas 256 256
  setPixels c munchingSquares
  -- Add it to the DOM
  b <- body =<< document
  appendChild b c

Coloring a canvas in WASM:

features

• ML syntax
  • let expressions
  • indentation-sensitive parsing
  • pattern matching
  • case expressions
• custom data types
• type classes
• user defined primitives
• user defined mixfix operators
• user defined sugar
• repl for evaluating expressions at the command line
• hendley-milner type inference
• wasm codegen
• spir-v codegen

links to implementation helpers

These are bookmarked links from my browser that are on topic:

• Demystifying Type Classes
• Hindley-Milner type inference with constraints
• Renaissance: a functional shading language
• Parsing Mixfix Operators