cons.lua

---@generic A, D
---@param head A
---@param tail D
---@return fun(): A, D
local function cons(head, tail)
  return function ()
    return head, tail
  end
end

---@generic A, D
---@param cell fun(): A, D
---@return A
local function car(cell)
  local head, _ = cell()
  return head
end

---@generic A, D
---@param cell fun(): A, D
---@return D
local function cdr(cell)
  local _, tail = cell()
  return tail
end

local a

local REPETITIONS = 10000000

-- luajit core/cons.lua  1.52s user 0.01s system 99% cpu 1.533 total
for _ = 1, REPETITIONS do
  local x = math.random()
  local y = math.random()

  local z = cons(x, y)
  a = car(z) + cdr(z)
end

-- luajit core/cons.lua  0.08s user 0.00s system 94% cpu 0.091 total
for _ = 1, REPETITIONS do
  local x = math.random()
  local y = math.random()

  local z = { x = x, y = y }
  a = z.x + z.y
end

print(a)

return {
  cons = cons,
  car = car,
  cdr = cdr,
}

Returning multiple values from a function isn't faster than using tables at all