stack.lua

-- This Lua stack may be faster than the vararg stack, since it does less copies. Haven't benchmarked it yet.
-- However, it can't hold as many elements (13 000 ish elements on my machine, vs uh, 100 000 or more with varargs?).

local function callstack()
  local function f(v)
    local op, nv = coroutine.yield()
    while true do
      if op == "push" then
        op, nv = coroutine.yield(f(nv))
      elseif op == "pop" then
        return v
      end
    end
  end
  local function empty()
    local op, nv = coroutine.yield()
    while true do
      if op == "push" then
        op, nv = coroutine.yield(f(nv))
      else
        op, nv = coroutine.yield()
      end
    end
  end
  local co = coroutine.wrap(empty)
  co()
  return function(v)
    co("push", v)
  end, function()
    return co("pop")
  end
end