Lua is a minimalist language where iterators are an important concept. Flua is a small library to compose lua iterators in a functional style.
Main motivation for this library was to allow monadic operations (chain, flatten), which are not supported by luafun.
Iterators can return multiple values. Most of this library thrives to manage these values on the stack (to the cost of slightly less readable code). However, there are a few cases where it cannot be done. In those cases we provide a generic method (e.g. last) that uses the heap, and fix argument methods (e.g. last1, last3) which use the stack (and are hence faster). It is also the case for functions scan and fold. zip also suffers the same inconvenient (for the first argument only) and we might provide an equivalent method if we ever meet the need it.
The library targets lua jit (fork of lua 5.1) and do not work with lua 5.4 or later.
Code is somewhat convoluted as it handles varags without creating tables, using lua specificities to handle the situation purely on stack instead of using heap allocation.
Definition of functions are given in comments, but we use names which are pretty standard amongst similar libraries.
local f = require "flua"
local function cb(n)
return f.range(n)
end
local res = f.compose(f.chain(cb), f.to_list())(f.range(3))
-- { 1, 1, 2, 1, 2, 3 }