Urn

Lisp dialect running on top of Lua, by SquidDev and demhydraz.

What?

• A minimal¹ Lisp implementation, with full support for compile time code execution and macros.
• Support for Lua 5.1, 5.2 and 5.3. Should also work with LuaJIT.
• Lisp-1 scoping rules (functions and data share the same namespace).
• Influenced by a whole range of Lisp implementations, including Common Lisp and Clojure.
• Produces standalone, optimised Lua files: no dependencies on a standard library.

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

Getting started: getting started guide. Docs: documentation for all functions and macros.