cons.lua

local Cons = {
    __tostring = function(cons) return "(" .. tostring(cons.car) .. " . " .. tostring(cons.cdr) .. ")" end
}

local function cons(car, cdr)
    local res = { car = car, cdr = cdr }
    setmetatable(res, Cons)
    return res 
end

local function list(a, ...)
    if a == nil then return nil end
    return cons(a, list(...))
end

local function map(f, l)
    if l == nil then return nil
    else return cons(f(l.car), map(f, l.cdr)) end
end

return {
    cons = cons,
    list = list,
    map = map
}