I’ve put up online a functional programming library for Lua that I wrote this summer. It’s located here:
The idea is to provide a bunch of functional programming constructs such as maps, filters, folds, list comprehensions, zips, some stuff like that. It includes a documentation file and a test suite that I’ve used to make sure the functions are correct and bug-free. (But you can never be sure!)
The bad news — I tested it with Lua 5.1.4, the current version, but Lua 5.2, in beta, introduces some changes that break lua-functional. I hope to have a fix for this up by the time Lua 5.2 is official!