Re: Why do we need “toclose” (or those angle brackets) at all?

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

Sergey Zakharchenko wrote:
> Paul,
> 
>> Why do we need the ugly, weird-looking and controversial <toclose> notation at all?
> 
> Indeed, so many people don't like it, but fail to notice one thing.
> You don't have to use it!
> 
> local function scope(object)
>     return next,{[object]=1},nil,object
> end
> 
> for file in scope(io.open("file")) do
>     print("I can use file ",file)
> end

Oh, I missed those changes to the for loop as well. This example however
would ignore any errors, io.open would return nil as the first return
value and the loop never runs.

I tried extending your example, but my result doesn't look pretty in my
opinion:

  local function scoperesult (t, c)
      if not c then
          return true, table.unpack(t, 1, t.n)
      else
          return nil
      end
  end

  function scope (...)
      local t = { ... }
      t.n = select("#", ...)
      return scoperesult, t, nil, (...)
  end

  for _, f, err in scope(io.open("test.dat") do
      print(f, err)
  end

It works, but it requires a new temporary table and an otherwise unused
loop control variable.

I still hope for some syntax like
  local <toclose> f, err = io.open("test.dat")

Or whatever is used instead of "<toclose>", I don't care that much about
it, it doesn't look particularly ugly to me.

Best regards,

David