A functional programming language

Example

This is a factorial written in the current language syntax, it can be found here, and here it is colorized by Treesitter

factorial_standard : n :Int , Int =
    if lt n 2
    then
      1
    else
      mul n (factorial_standard (minus n 1));


factorial_acc : n:Int , acc:Int, Int =
    if lt n 2
    then
      acc
    else
      factorial_acc (minus n 1) (mul n acc);

factorial_acc_sass : n:Int, acc:Int, Int =
    if lt n 2
    then
      acc
    else
      let new_n = minus n 1;
          new_acc = mul n acc;
      in
        factorial_acc_sass new_n new_acc
    ;

Editor support

Treesitter

We maintain a Treesitter grammar here

Neovim

There is also a neovim plugin to register the language and set some properties here.

Note that you still need to install the Treesitter grammar by yourself.

Roadmap

• Build a simple typed lambda calculus compiler with let and definitions
  • Support for build-in booleans and ints
  • Type checking
  • A REPL
  • Minimal standard library
  • naive code generation (python)
  • cps optimization
  • sass optimization
  • code generation (python, wasm)
  • optional : module system
• Addition of monomorphic records
• Addition of sum types
• Addition of parametric polymorphism
• Optional:
  • Typeclasses
  • A fixed set of operators with fixed precedence
• Checked exceptions or effects
• Code formatter
• Treesitter grammar
• Package manager

Examples

factorial_aux : int -> int -> int
= {
    \ n acc ->
        if lt n 2
        then
            1
        else
            let new_n = minus n 1;
                new_acc = mul n acc;
            in
                factorial_aux new_n new_acc
}

factorial : int -> int = { \ n -> factorial_aux n 1 }

Build and Development

Build

The simpler way to build is using nix

nix build

Develop environment

To access a development environment

nix develop

Formatting

To format all files (Haskell + Markdown + Shell + Cabal + YAML + TOML) run

nix fmt

Pre-push hooks

Be sure to add the following pre-push hook under .git/hooks/pre-push

root=$(git rev-parse --show-toplevel)
cd $root

nix flake check
flake_check_status=$?
nix develop --command bash -c "cabal test"
cabal_test_status=$?
if [ $flake_check_status -ne 0 ]; then
  echo "Failed at flake check"
  exit $flake_check_status
fi
if [ $cabal_test_status -ne 0 ]; then
  echo "Failed at haskell tests"
  exit $cabal_test_status
fi
exit 0

Pre-commit hooks

Be sure to add the following pre-commit hook under .git/hooks/pre-commit

root=$(git rev-parse --show-toplevel)
cd $root

nix flake check
flake_check_status=$?

if [ $flake_check_status -ne 0 ]; then
  echo "Failed at flake check"
  exit $flake_check_status
fi

Checks

We have two checks active right now:

• format check
• spell check

Both of them are run as part of the nix checks:

nix flake check

But can be run individually

Spell check

The spell checker we use is typos and can be run individually by

nix build .\#spell-check

Format check

We use various tools for format, one per language.

All of this tools are supported by treefmt-nix, and we can run the format check like

nix build .\#format-check