Re: To-be-close confusion...

[David Heiko Kolf <david@...>]

Sean Conner wrote:
>   Given the following example code:
> 
> 	local function readfile(name)
> 	  local <toclose> f = io.open(name)
> 	  if not f then return end

> 	  local res = {}
> 	  res.date = parse_date(f)
> 	  if not res.date then return end
> 	  res.name = parse_name(f)
> 	  if not res.name then return end
> 	  res.data = parse_data(f)
> 	  if not res.data then return end
> 	  return res
> 	end

I'd like to extend your example to include the error message from
io.open, in which case the current <toclose> syntax requires an extra
assignment:

	local function readfile(name)
	  local openres, errmsg, errcode = io.open(name)
	  local <toclose> f = openres
	  if not f then return nil, errmsg, errcode end

	  -- the rest I left unchanged:
	  local res = {}
	  res.date = parse_date(f)
	  if not res.date then return end
	  res.name = parse_name(f)
	  if not res.name then return end
	  res.data = parse_data(f)
	  if not res.data then return end
	  return res
	end

I think it is necessary to include full error handling in examples to
highlight the real use cases of the new syntax -- which I'd like to see
extended to "local <toclose> f, errmsg, errcode = io.open(name)".

Best regards,

David

(I hope I don't sound like a broken record yet.)