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malgo

★ 45 Open GitHub ↗

A statically typed functional programming language.

// repository documentation

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# malgo

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A statically typed functional programming language.

## Requirement

* [elan](https://github.com/leanprover/elan) (the Lean 4 toolchain manager; the toolchain version itself is pinned by `lean/lean-toolchain`)
* [Zig](https://ziglang.org/) 0.16, to compile Malgo programs to native executables

## Installation

```sh
git clone https://github.com/malgo-lang/malgo
cd malgo
cd lean && lake build
```

The compiler lands at `lean/.lake/build/bin/malgo`.

## Directory Structure

A brief overview of the main directories and files:

```
lean/          # The compiler, written in Lean 4 (CLI entry point, all passes)
docs/          # Documentation and references
examples/      # Example Malgo source files
runtime/malgo/ # Malgo runtime and standard library, and the self-hosted compiler
runtime/zig/   # The Zig backend's runtime (reference counting, primitives)
scripts/       # CI gates (golden parity, self-hosting, lint)
test/          # Testcases and golden fixtures
```

## Usage

To evaluate programs:

```sh
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

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

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

### Fibonacci number
File: `examples/malgo/Fib.mlg`
```malgo
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`
```malgo
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](https://github.com/jdx/mise) for managing development tools and tasks. The `mise.toml` file defines tool versions and common development workflows.

### Toolchain
- **Lean 4** (via elan; version pinned by `lean/lean-toolchain`)
- **Zig** 0.16 (pinned in `mise.toml`; the native backend's toolchain)
- **watchexec** (for file watching)
- **git-chglog** (for changelog generation)

### Common Tasks
Run these with `mise run <task>`:

- `setup` — Install elan.
- `build` — Build the compiler (`lake build`).
- `test` — Run the test suite. Filter with `-- --match <pattern>`.
- `exec` — Run the compiler (`-- eval examples/malgo/Hello.mlg`).
- `cli-gate` — Drive the CLI over the whole corpus.
- `zig-golden` — Byte-parity sweep of the Zig backend against the interpreter.
- `selfhost-golden` — Level 1 self-hosting (the Malgo evaluator written in Malgo).
- `lint-sources` — Lint every `.mlg` under `examples/`, `test/testcases/` and `runtime/`.
- `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: `duplicate`, `invalid`. (The workflow's exclusion list also names `skip-changelog`, but no such label exists, so it never matches.)

**Current hold:** the `v4.0.0` release PR (#398) is a draft and the `Create Release PR`
workflow is disabled until milestone `v4.0.0` is done (#385). Do not merge #398 before
then, and refresh the draft release's notes before you do — `release.yml` publishes
whatever draft exists, and the current one was generated at `v3.0.0..bf7c682f`.

To create labels via GitHub CLI:

```bash
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
```

malgo

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