bakpakin / fnl

Lua Lisp Language


Fnl is a lisp that compiles to Lua. It aims to be easy to use, expressive, and has almost zero overhead compared to handwritten Lua. It's currently a single file Lua library that can be dragged into any Lua project.

The documentation is currently sparse, but I don't want to commit too many features to documentation that haven't been fully defined. Current and projected features inlclude:

  • Full Lua compatibility - You can use any function from Lua
  • Zero overhead - Compiled code should be fast, standalone, and just as or more efficient than hand-written Lua.
  • Compile time only macros - Macros exist only at compile time and are not output in the final Lua compilation. In fact, macros are just a special case of special forms.
  • Ability to write custom special forms - Special forms are s-expressions that, when evaulated, directly output Lua code. This feature may be removed, in preference for macros.

Eventually, I also hope to add optional source maps, either embedded in the comments of the generated code, or in separate files. A standard library also needs to be made.


The fnl.lua module exports the following functions:

  • fnl.repl() - Starts a simple REPL.
  • fnl.eval(str, options) - Evaluates a string of Fnl.
  • fnl.compile(str, options) - Compiles a string of Fnl into a string of Lua
  • fnl.parse(str) - Reads a string and returns an AST.
  • fnl.compileAst(ast) - Compiles an AST into a Lua string.


Hello World

(print "hello, world!")

Fibonacci sequence

(set fib (fn [n] (or (and (> n 1)
                          (+ (fib (- n 1))
                             (fib (- n 2))))

(print (fib 10))

Try it

Clone the repository, and run lua fnl --repl to quickly start a repl.

Install with Luarocks

You can install the dev package from luarocks via

luarocks install --server= fnl


Copyright © 2016 Calvin Rose

Released under the MIT license

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