Re: Yet another proposal for <toclose> (was Re: [ANN] Lua 5.4.0 (alpha) now available)

[pocomane <pocomane_7a@...>]

On Fri, Jun 28, 2019 at 6:12 PM Sergey Kovalev <kovserg33@gmail.com> wrote:
>
> Can you give an example?
>
> > What about coroutines? I.e. "body" resumes a coroutine that calls "auto" (not protected by an inner "scope").

```
local function my_handler(f)
  print("closing",f)
end

local a_coroutine = coroutine.create(function()
  local auto = coroutine.yield()
  local f1 = auto(my_handler){ "file 1" }
  coroutine.yield()
  local f2 = auto(my_handler){ "file 2" }
  coroutine.yield()
  print("using", f1, "and", f2)
end)
coroutine.resume(a_coroutine)

scope(function(auto)
  coroutine.resume(a_coroutine, auto)
  coroutine.resume(a_coroutine)
end)
coroutine.resume(a_coroutine)
```

Yes, I know, I should use the scope/auto INSIDE the coroutine. Or I
have to put the last resume INSIDE scope. But the point is that with
this implementation I can also mess around like in the example. With a
real "Scoped annotation" like <toclose> I cannot.

In the past I have used something like your scope/auto, but exposing
auto outside the scope [1]. I admit that passing auto to the body
somehow protect you from some mistake, but I think it is not enough.

pocomane

[1] It was something like:

```
local list

local function defer( func )
  if not list then error("defer autside a scope", 2) end
  list[1+#list] = func
end

local function scope( block )
  local old_list = list
  list = {}

  local ok, err = pcall(block)

  for i = 1, #list do
    local ok, err = pcall(list[i])
    if not ok then warn(err) end
  end

  if not ok then error(err, 1) end

  list = old_list
end

----------------------------
-- usage example:

scope(function()

  local f1 = "file 1"
  defer(function() print("closing", f1) end)

  local f2 = "file 2"
  defer(function() print("closing", f2) end)

  print("using",f1,"and",f2)

end)
```