Crisp

Crisp is a curried lisp with its syntax being an amalgamation of Scheme and Fennel.

Building

The project depends on GHC 9.0.2 which can be installed by either GHCUP, you or Nix:

# Enter an evnironment with the correct `ghc` version
nix develop

# Build the project
stack build

# Run the project
stack run

File Structure

The project is split in two parts:

./src/ParserCombinators/ - small Parser Combinator library with parser for Crisp itself
./src/Crisp/ - repl and interpreter for the already parsed Crisp

Design

The project is built upon mtl's Monad___ typeclasses. Unfortunately, enforcing the MonadError String m constraint on the interpreter (together with MonadState m and MonadFix m) leads to infitite loops in most let-expressions, so, currently, interpreter errors are handled with the error function but the code is written in a way to easily enable the refactoring of using MonadError for errors handling when the looping error is (eventually) resovled. Other than that, at least, parsing errors are caught early enough.

Main functions

parse - Used to run a Parser on some input and (optionally) get a parsed AST back
eval - Used to evaluate already parsed code and aggregate the effect it induces (like define) using the monadic properties of State

Example code

Example code can be found at ./crisp/std.crisp

reo101 / crisp