malgo

A statically typed functional programming language.

Requirement

• cabal-install

Installation

Installing Malgo

git clone https://github.com/malgo-lang/malgo
cd malgo
cabal install

Directory Structure

A brief overview of the main directories and files:

app/           # CLI entry point (Main.hs)
docs/          # Documentation and references
examples/      # Example Malgo source files
nix/           # Nix-related files
runtime/       # Malgo runtime and standard library
src/           # Main source code (Haskell)
test/          # Test suites and testcases
README.md      # This file
malgo.cabal    # Cabal project file

Usage

To evaluate programs:

malgo eval [OPTIONS] SOURCE

• eval — Evaluate a Malgo program.
• SOURCE — Path to the source file to evaluate (required).

Options

• --no-opt — Disable optimizations during compilation.
• --lambdalift — Enable lambda lifting.
• --debug-mode — Enable debug mode for verbose output.

Example

malgo eval --no-opt --debug-mode examples/malgo/Hello.mlg

This will evaluate examples/malgo/Hello.mlg with optimizations disabled and debug mode enabled.

Examples

The examples/malgo/ directory contains a variety of example programs demonstrating Malgo's features. Here are some highlights:

Hello, world

File: examples/malgo/Hello.mlg

module {..} = import "../../runtime/malgo/Builtin.mlg"
module {..} = import "../../runtime/malgo/Prelude.mlg"

def main = {
  putStrLn "Hello, world!"
}

Fibonacci number

File: examples/malgo/Fib.mlg

module {..} = import "../../runtime/malgo/Builtin.mlg"
module {..} = import "../../runtime/malgo/Prelude.mlg"

infix 4 (<=)
def (<=) = { x y -> leInt32 x y }

infixl 6 (+)
def (+) = { x y -> addInt32 x y }

infixl 6 (-)
def (-) = { x y -> subInt32 x y }

def fib = { n ->
  if (n <= 1)
    { 1 }
    { fib (n - 1) + fib (n - 2) }
}

def main = {
  fib 5 |> toStringInt32 |> putStrLn
}

List operations

File: examples/malgo/List.mlg

module {..} = import "../../runtime/malgo/Builtin.mlg"
module {..} = import "../../runtime/malgo/Prelude.mlg"

infix 4 (<=)
def (<=) : Int32 -> Int32 -> Bool
def (<=) = {x y -> leInt32 x y}

infixl 6 (+)
def (+) : Int32 -> Int32 -> Int32
def (+) = {x y -> addInt32 x y}

infixl 6 (-)
def (-) : Int32 -> Int32 -> Int32
def (-) = {x y -> subInt32 x y}

def map : (a -> b) -> List a -> List b
def map =
  { _ Nil -> Nil,
    f (Cons x xs) -> Cons (f x) (map f xs)
  }

def sum : List Int32 -> Int32
def sum =
  { Nil -> 0,
    Cons x xs -> x + sum xs
  }

-- [0 .. n]
def below : Int32 -> List Int32
def below = { n ->
  if (n <= 0)
     { [0] }
     { Cons n (below (n - 1)) }
}

def main = {
  sum (map (addInt32 1) (below 10))
    |> toStringInt32
    |> putStrLn
}

Lisp interpreter

https://github.com/malgo-lang/minilisp

For Developers

This project uses mise for managing development tools and tasks. The mise.toml file defines tool versions and common development workflows.

Toolchain

• GHC (via ghcup)
• cabal-install
• hpack
• Haskell Language Server (HLS)
• go (for changelog generation)
• watchexec (for file watching)
• git-chglog (for changelog generation)

Common Tasks

Run these with mise run <task>:

• setup — Install and set up all required tools and dependencies.
• setup-hls — Build and set up Haskell Language Server for the project.
• build — Build the project (hpack && cabal build).
• test — Run the test suite. Optionally filter tests with --option match=<pattern>.
• exec — Run the project executable (cabal exec malgo-exe).
• changelog — Generate the changelog using git-chglog.

See mise.toml for more details and customization.

Release Workflow

• Labels: Use PR labels breaking, feat, fix following Conventional Commits to drive semantic version bumps.
• Auto-labeling: PRs are auto-labeled from commit messages via CI.
• Release PR: On pushes to master, CI computes the next version, creates a draft GitHub Release, and opens a release/vX.Y.Z PR.
• Publish: Merging a release/* PR to master tags the commit and publishes the GitHub Release.
• Notes: Releases use generated notes; excluded labels: skip-changelog, duplicate, invalid.

To create labels via GitHub CLI:

gh label create breaking --description "Major version bump (breaking change)" --color D93F0B
gh label create feat --description "Minor version bump (feature)" --color 0E8A16
gh label create fix --description "Patch version bump (fix)" --color FBCA04