Owl

Owl is an interpreted programming language that I made for fun to learn about compiler design and to get some experience with Go.

It shamelessly steals ideas from many different languages, here are a few highlights that I enjoy:

// Pattern matching arguments
let factorial = (0) => 1
              : (n) => n * f(n - 1)

f = (n) ? n == 1 => 1
  | (n) => n * f(n - 1) 

x = (a, b) => 1
  | when 0 == b => 0
  | when a < b (a, b) => -1 

// Simple list, set, and map definitions
let l = [1, 2, 3]
let s = {1, 2, 3}
let m = {a: 1, b: 2, c: 3}

// Spread syntax
let swap = (a, b, c) => c, b, a
let [x, ...xs] = swap(...l)

// First class functions
let plus_two = (x) => x + 2
let l_plus_two = l.map(plus_two)

// Null coalesce / access / call
let y = null ?? 4
let z = {a: 5, b: 6}?.c 
let w = {a: v => v + 1}.w?()
let v = l?[1]

// Multiple assignment / return values
x, y = y, x
x, y = (() => return 1, 2)()

// Operator overloading
complex = {real: 2, imag: 3}
complex::mul = (a, b) => {real: a.real * b.real - a.imag * b.imag, imag: a.real * b.imag + a.imag * b.real}
complex * complex == {real: -5, imag: 12}

Building

Bulding the code is as simple as running build.sh or build.bat depending on your operating system of choice. They both just run go build and copy the standard library into the bin folder. You can optionally add the bin folder to $PATH so you can execute the owl command more easily.

Updating

When releasing a new version, change the git tags so that go's package manager knows there has been an update.

go mod tidy
go test ./...

commit changes...

git tag vX.X.X
git push origin vX.X.X