The Urn Logo

Urn: A Lisp implementation for Lua

Urn is a new language developed by SquidDev, and demhydraz. Urn is a Lisp dialect with a focus on minimalism which compiles to Lua.

What?

¹: Minimalism is an implementation detail.

Features

Pattern matching

> (case '("x" (foo 2 3))
.   [(string?  @ ?x) (.. "Got a string " x)]
.   [("x" (foo . ?x)) (.. "Got some remaining values " (pretty x))])
out = "Got some remaining values (2 3)"

Various looping constructs

> (loop [(o '())
.        (l '(1 2 3))]
.   [(empty? l) o]
.   (recur (cons (car l) o) (cdr l)))
out = (3 2 1)

Powerful assertion and testing framework

> (import test ())
out = nil
> (affirm (eq? '("foo" "bar" "")
.              (string/split "foo-bar" "-")))
[ERROR] <stdin>:1 (compile#111{split,temp}:46): Assertion failed
(eq? (quote ("foo" "bar" "")) (string/split "foo-bar" "-"))
     |                        |
     |                        ("foo" "bar")
     ("foo" "bar" "")

First-class support for Lua tables

> { :foo 1
.   :bar 2 }
out = {"bar" 2 "foo" 1}

Friendly error messages

> (]
[ERROR] Expected ')', got ']'
  => <stdin>:[1:2 .. 1:2] ("]")
 1 │ (]
 ^... block opened with '('
 1 │ (]
  ^ ']' used here
> 

Getting started

We have a getting started guide to help you get set up. Or you can clone the repo and jump right in!

The website also contains documentation for all functions and macros, should you need to check how something works.