Re: (not) handling new programming idioms with grace

[Sean Conner <sean@...>]

It was thus said that the Great Dibyendu Majumdar once stated:
> On 18 July 2018 at 17:19, Roberto Ierusalimschy <roberto@inf.puc-rio.br> wrote:
> > We had something (scope-qualified locals) that seemed to be enough.
> > Now we have this list of problems:
> >
> > - It does not create a new scope by itself;
> > - It is not visible enough;
> > - It still does not solve the problem for global variables;
> > - It cannot supress exceptions.
> >
> 
> Perhaps something simpler could be done? Such as ask a function to be
> called on scope exit (normally or via exception) - similar to defer
> statement in Go?
> 
> Then user code can do what it likes in that function - responsibility
> of Lua ends with invoking the function.

  It could be done now, although not automatically:

	function hoover(...)
	  for i = 1 , select('#',...) do
	    local obj = select(i,...)
	    local mt  = getmetatable(obj)
	    if mt and mt.__gc then
	      mt.__gc(obj)
	    end
	  end
	end

	do
	  local expensive = foo_user_obj()
	  local cheap     = {}
	  local medium    = setmetatable({},{ __gc = function(o) end })

	  hoover(expensive,cheap,medium)
	end

  -spc (Must ... avoid ... proposing ... new ... metamethod ... )