Re: iterating over ... ?

[Patrick Donnelly <batrick@...>]

On Mon, Apr 4, 2011 at 9:48 AM, Jerome Vuarand <jerome.vuarand@gmail.com> wrote:
> You can use coroutines, but I don't think it's a better solution. For example:
>
> local function step(head, ...)
>  if head==nil then
>    return
>  end
>  coroutine.yield(head)
>  return step(...)
> end
>
> local function init(...)
>  coroutine.yield()
>  return step(...)
> end
>
> local function vararg(...)
>  local c = coroutine.wrap(init)
>  c(...)
>  return c
> end
>
> for value in vararg(1, 2, 3) do
>  print(value)
> end

You can also handle nils:

local function step (n1, n2, v, ...)
  if n1 > n2 then
    return nil
  else
    coroutine.yield(n1, v)
    return step(n1+1, n2, ...)
  end

end

local function init (...)
  coroutine.yield()
  return step(1, select("#", ...), ...)
end

function vararg(...)
  local c = coroutine.wrap(init)
  c(...)
  return c
end

Then you iterate using:

for i, v in vararg(a, b, c) do
end

-- 
- Patrick Donnelly