👾 Plum

A simple, statically typed programming language with enums, pattern matching and generics. It compiles to WebAssembly.

import std/Io
import std/Int
import std/Float
import std/Str
import std/List
import std/Option

enum Shape =
  | Circle(r: Float)
  | Rect(w: Float, h: Float)

  fun area(self) -> Float =
    match self
      Circle(r) => r * r * 3.14
      Rect(w, h) => w * h

fun firstEven(xs: List[Int]) -> Option[Int] =
  for x := range xs
    if x % 2 == 0
      return Some(x)
  None

fun main(io: Io) =
  shape := Rect(w: 2.0, h: 3.0)
  even := firstEven([1, 3, 4]).unwrapOr(0)
  io.printLn("area {shape.area()}, first even {even}")

test "shapes"
  assert Rect(w: 2.0, h: 3.0).area() == 6.0
  assert firstEven([1, 3]).isNone()

Features

• Easy to read: blocks are indentation, and there is one way to loop over anything.
• Structs and enums: match checks that you handled every case.
• Generics: write fun id[T](x: T) -> T, and each type gets its own fast copy.
• No null, no exceptions: absence is Option, failure is Result, and ? passes an error up.
• Closures and tail calls: recursion runs in constant stack.
• Tests built in: add a test block next to your code and run plum test.
• Visible side effects: printing, files and network go through an Io value, so a function without one can't touch the outside world.
• Fast by default: the compiler removes temporary lists and updates values in place when it is safe, with no change to what your code means.
• Games: a built-in engine runs in the browser on WebGPU.
• Editor support: syntax highlighting and a language server for Helix and VSCode.

Plum compiles to WebAssembly (wasm-gc), and plum build wraps the result in a native executable. True native targets are planned.

Install

Make it executable and put it on your PATH, e.g. on macOS/Linux:

curl -L -o plum https://git.pyrossh.dev/releases/plum-cli/v0.1.0/plum-darwin-arm64
chmod +x plum
mv plum ~/.cargo/bin/plum   # or anywhere else already on your PATH

Or build from source with cargo install --path compiler/cli.

Use it

Run these from a checkout of this repository, so import std/... can find the standard library.

plum run file.plum       # compile and run; a game opens in the browser and reloads as you edit
plum test file.plum      # run its tests
plum build file.plum     # make an executable, or a website for a game
plum editor helix        # set up your editor (or vscode)

Learn more

• The language: the full guide
• The standard library: strings, lists, maps, JSON, files and more
• The game engine: drawing, input, sound and scene graphs
• Tools: every command and option, editors, building from source
• Performance: how the compiler optimises your code
• Examples: a runnable file per feature, and example games